From “Astronomy Magazine” : “Radio interference from satellites is threatening astronomy”

From “Astronomy Magazine”

3.9.23
Christopher Gordon De Pree | Deputy Electromagnetic Spectrum Manager, National Radio Astronomy Observatory
Christopher R. Anderson | Associate Professor of Electrical Engineering, United States Naval Academy
Mariya Zheleva | Assistant Professor of Computer Science, University at Albany, State University of New York

Just as human development leads to more light pollution increasing numbers of satellites are leading to more radio interference.

“Visible light is just one part of the electromagnetic spectrum that astronomers use to study the universe. The James Webb Space Telescope was built to see infrared light, other space telescopes capture X-ray images, and observatories like the Green Bank Telescope, the Very Large Array, the Atacama Large Millimeter Array, and dozens of other observatories around the world work at radio wavelengths.

Green Bank Radio Telescope, West Virginia now the center piece of the Green Bank Observatory being cut loose by the National Science Foundation, supported by Breakthrough Listen Project, West Virginia University, and operated by the nonprofit Associated Universities, Inc.

National Radio Astronomy Observatory Karl G Jansky Very Large Array located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~50 miles (80 km) west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes.

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)/National Radio Astronomy Observatory/National Astronomical Observatory of Japan(JP) ALMA Observatory (CL).

Radio telescopes are facing a problem. All satellites, whatever their function, use radio waves to transmit information to the surface of the Earth. Just as light pollution can hide a starry night sky, radio transmissions can swamp out the radio waves astronomers use to learn about black holes, newly forming stars and the evolution of galaxies.

We are three scientists who work in astronomy and wireless technology. With tens of thousands of satellites expected to go into orbit in the coming years and increasing use on the ground, the radio spectrum is getting crowded. Radio quiet zones – regions, usually located in remote areas, where ground-based radio transmissions are limited or prohibited – have protected radio astronomy in the past.

As the problem of radio pollution continues to grow, scientists, engineers and policymakers will need to figure out how everyone can effectively share the limited range of radio frequencies. One solution that we have been working on for the past few years is to create a facility where astronomers and engineers can test new technologies to prevent radio interference from blocking out the night sky.

Different telescopes capture different parts of the electromagnetic spectrum, with radio telescopes collecting radiation of the longest wavelengths. Credit: InductiveLoad/NASA/Wikimedia Commons, CC BY-SA

Astronomy with radio waves

Radio waves are the longest wavelength emissions on the electromagnetic spectrum, meaning that the distance between two peaks of the wave is relatively far apart. Radio telescopes collect radio waves in wavelengths from millimeter to meter wavelengths.

Messier 87*, The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via The Event Horizon Telescope Collaboration released on 10 April 2019 via National Science Foundation.

This is the first image of Sagittarius A* – [SGR A*] the supermassive black hole at the center of the Milky Way. Credit: The Event Horizon Telescope Collaboration.

Even if you are unfamiliar with radio telescopes, you have probably heard about some of the research they do. The fantastic first images of accretion disks around black holes were both produced by the Event Horizon Telescope.

The locations of the radio dishes of the Event Horizon Telescope array in 2019. Since then new telescopes have been added.

This telescope is a global network of eight radio telescopes, and each of the individual telescopes that make up the Event Horizon Telescope is located in a place with very little radio frequency interference: a radio quiet zone.

A radio quiet zone is a region where ground-based transmitters like cellphone towers are required to lower their power levels so as not to affect sensitive radio equipment. The U.S. has two such zones. The largest is the National Radio Quiet Zone, which covers 13,000 square miles (34,000 square kilometers) mostly in West Virginia and Virginia.

National Radio Quiet Zone (NRQZ)
The National Radio Quiet Zone (NRQZ) was set aside by the federal government to provide a geographical region to protect sensitive instrumentation from Radio Frequency Interference (RFI).

It contains the Green Bank Observatory. The other, the Table Mountain Field Site and Radio Quiet Zone, in Colorado, supports research by a number of federal agencies.

Table Mountain Field Site and Radio Quiet Zone, Colorado.

Similar radio quiet zones are home to telescopes in Australia, South Africa and China.

Inyarrimanha Ilgari Bundara, our Murchison Radio-astronomy Observatory is one of the best locations in the world to operate telescopes that listen for radio signals from space.

Our observatory in the heart of Wajarri Country in remote Western Australia is home to our ASKAP radio telescope as well as other international radio astronomy projects. We currently host the Curtin University-led Murchison Widefield Array (MWA) and Arizona State University’s Experiment to Detect the Global Epoch of Reionization Signature (EDGES) instrument.
Credit: CSIRO.

Karoo radio quite zone, South Africa

FAST-Five-hundred-meter Aperture Spherical radio Telescope [[五百米口径球面射电望远镜] (CN), located in the Dawodang depression in Pingtang County, Guizhou Province, South China.

Large satellite constellations, like those of Starlink, can be seen marching in lines across night skies and harm both visible and radio astronomy. STARLINK satellites train seen from earth – SpaceX Elon Musk.

A satellite boom

On Oct. 4, 1957, the Soviet Union launched Sputnik into orbit. As the small satellite circled the globe, amateur radio enthusiasts all over the world were able to pick up the radio signals it was beaming back to Earth. Since that historic flight, wireless signals have become part of almost every aspect of modern life – from aircraft navigation to Wi-Fi – and the number of satellites has grown exponentially.

The more radio transmissions there are the more challenging it becomes to deal with interference in radio quiet zones. Existing laws do not protect these zones from satellite transmitters, which can have devastating effects. In one example, transmissions from an Iridium satellite completely obscured the observations of a faint star made in a protected band allocated to radio astronomy.

Two images from the Very Large Array in New Mexico show what a faint star looks like to a radio telescope without satellite interference, left, and with satellite interference, right. G. Taylor, UNM, CC BY-ND.

Satellite internet networks like Starlink, OneWeb and others will eventually be flying over every location on Earth and transmitting radio waves down to the surface. Soon, no location will be truly quiet for radio astronomy.

Just as with light pollution, the more development there is on Earth and in the sky, the more radio interference there will be. Gppercy/Wikimedia Commons, CC BY-SA

Interference in the sky and on the ground

The problem of radio interference is not new.

In the 1980s, the Russian Global Navigation Satellite System – essentially the Soviet Union’s version of GPS – began transmitting at a frequency that was officially protected for radio astronomy. Researchers recommended a number of fixes for this interference. By the time operators of the Russian navigation system agreed to change the transmitting frequency of the satellites, a lot of harm had already been done due to the lack of testing and communication.

Many satellites look down at Earth using parts of the radio spectrum to monitor characteristics like surface soil moisture that are important for weather prediction and climate research. The frequencies they rely on are protected under international agreements but are also under threat from radio interference.

A recent study showed that a large fraction of NASA’s soil moisture measurements experience interference from ground-based radar systems and consumer electronics. There are systems in place to monitor and account for the interference, but avoiding the problem altogether through international communication and prelaunch testing would be a better option for astronomy.

Most radio telescopes, like the Atacama Large Millimeter Array in Chile, are in areas far from any source of interference. But a new site designed to test technologies and interference solutions could prevent future problems.
Credit: J. Guarda/ALMA (ESO/NAOJ/NRAO) CC BY.

Solutions to a crowded radio spectrum

As the radio spectrum continues to get more crowded, users will have to share. This could involve sharing in time, in space or in frequency. Regardless of the specifics, solutions will need to be tested in a controlled environment. There are early signs of cooperation. The National Science Foundation and SpaceX recently announced an astronomy coordination agreement to benefit radio astronomy.

Working with astronomers, engineers, software and wireless specialists, and with the support of the National Science Foundation, we have been leading a series of workshops to develop what a national radio dynamic zone could provide. This zone would be similar to existing radio quiet zones, covering a large area with restrictions on radio transmissions nearby. Unlike a quiet zone, the facility would be outfitted with sensitive spectrum monitors that would allow astronomers, satellite companies and technology developers to test receivers and transmitters together at large scales. The goal would be to support creative and cooperative uses of the radio spectrum. For example, a zone established near a radio telescope could test schemes to provide broader bandwidth access for both active uses, like cell towers, and passive uses, like radio telescopes.

For a new paper our team just published [IEEEXplore (below)], we spoke with users and regulators of the radio spectrum, ranging from radio astronomers to satellite operators. We found that most agreed that a radio dynamic zone could help solve, and potentially avoid, many critical interference issues in the coming decades.

Such a zone doesn’t exist yet, but our team and many people across the U.S. are working to refine the concept so that radio astronomy, Earth-sensing satellites and government and commercial wireless systems can find ways to share the precious natural resource that is the radio spectrum.”

IEEEXplore

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “How high-altitude balloons help unlock the cosmos”

From “Astronomy Magazine”

3.7.23
Paul Sutter

Balloons offer an affordable way to climb high above Earth’s atmosphere providing a clear view of space that’s inaccessible to ground-based telescopes.

Michael Lentz/NASA’s Goddard Space Flight Center Conceptual Image Lab.

The recent episodes of jet fighters shooting down spy balloons has everyone talking about how they can be used for surveillance. But if anyone had bothered to ask an astronomer, they would know we’ve been attaching telescopes to balloons for decades — and the technique even represents the latest cutting edge in NASA research.

Windows to the universe

Sure, the atmosphere may provide living creatures on our planet with plenty of air to breathe. But for the astronomer, it’s simply a nuisance.

Not only does the atmosphere scatter light from distant sources, making detailed observations difficult, but also the atoms and molecules in the air between us and space are fantastic at absorbing large portions of the electromagnetic spectrum.

To human eyes, the atmosphere looks as clear as, well, day. But that’s because our eyes are adapted to the visible wavelengths of light that sail right through our air. Radio waves, which are invisible to us, also handily slosh through our atmosphere. But other wavelengths aren’t so lucky.

Any photons that are especially energetic — like gamma rays, X-rays, and most ultraviolet rays — get stopped dead in their tracks when they encounter our atmosphere. Infrared, too, is easily absorbed, drastically limiting our view of the cosmos.

Earth’s atmosphere only allows certain wavelengths of light to pass through it to the ground, meaning that high-altitude or space-based observatories are often the only way to see certain parts of the universe. NASA.

The most straightforward response to this challenge (other than depleting our atmosphere and making Earth an airless world) to is send our telescopes into the vacuum of outer space. Such orbiting observatories have already provided a wealth of data about the wider universe. But they do have one serious drawback: Pound-for-pound, space telescopes are orders of magnitude more expensive than any other type of telescope.

So, with too much air to do decent astronomy on the ground, and not enough money to consistently do it in space, there’s one form of observatory that is gaining more and more traction — the balloon.

Lofting science

The idea is simple. Step 1: Build a giant balloon, something capable of getting tens of thousands of feet above the Earth. Step 2: Attach a telescope to said balloon. Step 3: Profit.

In 1957, the pioneering astrophysicist Martin Schwarzschild designed the Stratoscope I, the first balloon-borne observatory. Featuring a 12-inch primary mirror and a 35mm movie camera, Schwarzschild used the floating observatory to study turbulence in the Sun’s photosphere from 80,000 feet (24.4 kilometers) above Earth’s surface.

The fully inflated balloon that lofted Stratoscope I is seen here shortly before its flight in 1957. The telescope captured one exposure of the Sun per second, with each exposure lasting 1/1000th of a second. U.S. Navy.

Since that initial test, balloons have provided a unique window into the wider universe. Even though each individual balloon mission could only last a few days to a few months, they could reach altitudes far higher than any ground-based observatory — all for a fraction of the cost of space-based missions.

With balloons, astronomers have been able to easily access several regions of the electromagnetic spectrum, offering insights into the high-energy and infrared universe.

Perhaps the most significant of the balloon-born experiments was BOOMERanG, the Balloon Observations Of Millimetric Extragalactic Radiation And Geophysics. Starting in 1997, the BOOMERanG experiment flew to an altitude of 138,000 feet (42 km) above Antarctica to observe the cosmic microwave background, the leftover light from when the entire universe cooled from a plasma state when it was just 380,000 years old.

National Aeronautics Space AgencyCosmic Background Explorer COBE 1989 to 1993.

COBE image of the CMB, the earliest image of the CMB

NASA/Wilkinson Microwave Anisotropy Probe (WMAP) 2001 to 2010 annotated.

Cosmic Microwave Background NASA/WMAP

The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU) Planck microwave telescope 2009 to 2013.

CMB per European Space Agency(EU) Planck.

BOOMERanG made critical measurements of this background radiation that provided the information needed to demonstrate that our universe is geometrically flat, confirming a key prediction of the Big Bang theory and validating that dark energy is real.

The future is looking up

The BOOMERanG experiments ended in 2003, but their legacy continues. Antarctica provides especially fruitful ground for many kinds of astronomy thanks to the relative clarity and dryness of the air above the South Pole.

And not all balloon-borne experiments look up. The innovative ANITA (Antarctic Impulsive Transient Antenna) looked down into the Antarctic ice sheet during its series of months-long missions.

ANITA.

ANITA consisted of a series of radio telescopes closely monitoring the ice while suspended from a helium-filled balloon at an altitude of some 121,000 feet (37 km). If a high-energy neutrino (a ghostly particle produced during nuclear reactions throughout the cosmos) slammed into a water ice molecule, it would produce a flash of radio emission.

By recording when and where these radio flashes occurred, ANITA essentially turned the whole Antarctic continent into a giant neutrino telescope — something that would be impossible from the ground or from space.

The next major balloon-borne experiment is ASTHROS, the Astrophysics Stratospheric Telescope for High Spectral Resolution Observations at Submillimeter-wavelengths. Led by NASA’s Jet Propulsion Laboratory, ASTHROS is expected to launch for a three-week mission in December 2023, once again above Antarctica.

Reaching an expected altitude of 130,000 feet (39.6 km), ASTHROS will feature a balloon some 400 feet (122 meters) wide carrying a payload totaling 5,500 pounds (2,500 kilograms). That balloon will loft an enormous 8.2-foot-wide (2.5 m) telescope, tying the record for largest telescope ever mounted on a balloon.

ASTHROS is designed to specifically target star-forming regions in the Milky Way, which will help astronomers understand stellar feedback, or how star formation in one area affects star formation nearby.

Missions like ASTHROS show that despite a perpetual tug-of-war between ground- and space-based observatories, there will always be a third option — one where the sky is the limit.

ASTHROS is seen observing the cosmos while floating some 130,000 feet (39.6 km) above Antarctica in this artist’s concept. NASA/JPL-Caltech.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “How lunar cycles guide the spawning of corals and worms and more”

From “Astronomy Magazine”

3.2.23
Virat Markandeya

Many sea creatures release eggs and sperm into the water on just the right nights of the month. Researchers are starting to understand the biological rhythms that sync them to phases of the Moon.

Many species of coral release their bundles of sperm and eggs during a particular phase in the lunar cycle, as shown here for coral in the Red Sea. The fantastic show — as well as reproductive events in other marine creatures — requires a biological clock with tight coupling to lunar cycles. TOM SHLESINGER.

It’s evening at the northern tip of the Red Sea, in the Gulf of Aqaba, and Tom Shlesinger readies to take a dive. During the day, the seafloor is full of life and color; at night it looks much more alien. Shlesinger is waiting for a phenomenon that occurs once a year for a plethora of coral species, often several nights after the Full Moon.

Guided by a flashlight, he spots it: coral releasing a colorful bundle of eggs and sperm, tightly packed together. “You’re looking at it and it starts to flow to the surface,” Shlesinger says. “Then you raise your head, and you turn around, and you realize: All the colonies from the same species are doing it just now.”

Some coral species release bundles of a pinkish- purplish color, others release ones that are yellow, green, white or various other hues. “It’s quite a nice, aesthetic sensation,” says Shlesinger, a marine ecologist at Tel Aviv University and the Interuniversity Institute for Marine Sciences in Eilat, Israel, who has witnessed the show during many years of diving. Corals usually spawn in the evening and night within a tight time window of 10 minutes to half an hour. “The timing is so precise, you can set your clock by the time it happens,” Shlesinger says.

Moon-controlled rhythms in marine critters have been observed for centuries. There is calculated guesswork, for example, that in 1492 Christopher Columbus encountered a kind of glowing marine worm engaged in a lunar-timed mating dance, like the “flame of a small candle alternately raised and lowered” [PLOS ONE (below)] Diverse animals such as sea mussels, corals, polychaete worms and certain fishes are thought to synchronize their reproductive behavior by the Moon. The crucial reason is that such animals — for example, over a hundred coral species [Marine Biology (below)] at the Great Barrier Reef — release their eggs before fertilization takes place, and synchronization maximizes the probability of an encounter between eggs and sperm.

How does it work? That has long been a mystery, but researchers are getting closer to understanding. They have known for at least 15 years that corals, like many other species, contain light-sensitive proteins called cryptochromes, and have recently reported that in the stony coral, Dipsastraea speciosa, a period of darkness between sunset and moonrise appears key [PNAS (below)] for triggering spawning some days later.

PNAS 2021

Fig. 1.

Spawning day of D. speciosa in the field manipulation experiment. (A) Study location at Lyudao (Green Island), Taiwan. The white dot indicates Gonggan, where D. speciosa fragments were collected and the field observation and experiment were conducted. (B) An egg trap in a transparent plastic bag and (C) an egg trap in an aluminum foil bag. (D) Spawning in natural populations of D. speciosa (>10 colonies) at the study location and (E) spawning of D. speciosa fragments under the moonlight-blocking treatment commencing at 3 d before the full moon (panel 1), 1 d before the full moon (panel 2), and 1 d after the full moon (panel 3). Black bars indicate major spawning (>hundreds of eggs), and white bars indicate minor spawning (several eggs) in four replicate fragments. Note that “NA” indicates no observation. Different letters in the panels in E indicate significant differences between the treatments (ANOVA and Tukey HSD test; P < 0.001). For detailed results of statistical analysis, refer to SI Appendix, Table S2.

Fig. 2.

Spawning day of D. speciosa under different moonlight exposure days. (A) The design of one experimental unit, including four replicate tank systems for each experimental treatment. (B) D. speciosa fragments were exposed to three experimental moonlight (dim light [∼0.3 lx]) conditions with different exposure days at nighttime (18:30 to 05:00): no light treatment (panel 1), 2-d exposure treatment (panel 2), and 4-d exposure treatment (panel 3). Black bars indicate major spawning (>hundreds of eggs), and white bars indicate minor spawning (several eggs) in four replicate fragments. Different letters in the panels indicate significant differences between the treatments (ANOVA and Tukey HSD test; P ≤ 0.001). For detailed results of statistical analysis, refer to SI Appendix, Table S2.

Marine Biology 1986

PLOS ONE 2018

Fig 1

Bioluminescent display of Odontosyllis enopla.
During the breeding period, female Odontosyllis enopla swim in slow circles secreting a bright bluish-green luminous mucus while releasing gametes. Photo credit: Dr. James B. Wood.

Fig 2

Multiple sequence alignment of the Odontosyllis enopla luciferase gene with that of the Japanese syllid O. undecimdonta.
The Odontosyllis enopla luciferase gene (329 amino acids in length) is aligned with the four putative luciferase transcripts (isoforms) of O. undecimdonta. The alignment was generated using default parameters and the L-INS-i iterative refinement method within MAFFT (v7.402). Ou: O. undecimdonta. Oe1: O. enopla Individual 1.

Fig 3

An unrooted maximum likelihood-based phylogenetic tree showing the relationship of both orthologs and paralogs of the luciferase gene for Odontosyllis enopla and O. undecimdonta.

The four transcripts (isoforms) found by Schultz et al. [44*] are in orange. ‘O_undecimdonta_DN31989’ (green) is identical to one of the four isoforms but has a different name because it is based on our Trinity assembly. The two additional green terminals are paralogs of the O. undecimdonta luciferase that were not reported by Schultz et al. [44]. For O. enopla, orthologs are shown in purple and the paralogs in blue. O_enopla_1: Individual 1, O_enopla_2: Individual 2, O_enopla_3: Individual 3. The ML tree was constructed using a MUSCLE-based amino acid alignment and the following parameters: WAG + gamma + I model; aLRT-based support values.
*References in the science paper

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “‘Fireworks’ sparked by survivor of stellar collision”

From “Astronomy Magazine”

2.28.23
Mark Zastrow

The object powering this display may be the result of a supernova that didn’t destroy the stars involved.

Like a blooming firework in the night sky, the nebula Pa 30 has stunningly thin contrails of sulfur emission emanating from a central star. The bright star to the right of center is not associated with the object. Credit: Robert Fesen.

When two white dwarfs in a binary star system eventually spiral in toward each other and collide, the result is usually mutually assured destruction: a thermonuclear explosion that consumes both stars and scatters their remains into the cosmos.

But astronomers have found one case where such a collision resulted in fireworks of a different kind.

New observations of the faint nebula Pa 30 have revealed that it is surrounded by filaments of glowing sulfur gas, appearing like the trails of sparks blown outward by an exploding fireworks shell. Astronomers think this scene was caused when two white dwarfs collided — and managed to not destroy each other. Instead, they apparently merged and formed a magnetic monster of a star that blows its own material into space, whisking debris from the merger outward to form the sulfuric, streaming contrails.

Researchers say the nebula and its central star comprise a unique object with scarcely any observational precedent. “I’ve worked on supernova remnants for 30 years and I’ve never seen anything like this,” said Robert Fesen, of Dartmouth College in Hanover, New Hampshire. Fesen was speaking Jan. 12 in Seattle at the winter meeting of the American Astronomical Society (AAS), where he presented his team’s results at a press conference. “There’s nothing like this in our galaxy.” The science paper has been accepted for publication by The Astrophysical Journal Letters [below].

It is “a really interesting” object, said Benson Guest, an X-ray astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who wasn’t involved with the study. “These things are very hard to detect because they’re not very bright compared to a normal supernova, so you’re looking for a very faint transient [object].”

The new imagery bolsters the case that Pa 30 is what astronomers call a Type Iax supernova — a type of “failed” supernova that results in a relatively tepid burst of light and leaves behind a surviving star. These have been observed in distant galaxies, but “this would be the first one we’ve ever found” in the Milky Way that we can easily study, said Guest. “Any time you can say that in astronomy, that’s something that’s really cool.”

What’s more, the new observations also pins down the object’s age — and give it a strong case for being the solution to a 900-year-old astronomical mystery.

Overlooked gem

Pa 30 lies just 7,500 light-years away in Cassiopeia and spans roughly 3′ (or about one-tenth the width of the Full Moon). It was discovered by amateur astronomer Dana Patchik in 2013 as he was searching archival data from NASA’s Wide Infrared Survey Satellite (WISE).

National Aeronautics and Space Administration Wise/NEOWISE Telescope.

In that data, the object had a rather conventional circular doughnut-like appearance resembling a planetary nebula — an object formed when an aging star sheds its outer layers of gas into space and then irradiates that gas, exciting it and causing it to glow.

Over the next few years, multiple professional observatories conducted follow-up observations, including the 10-meter Gran Telescopio Canarias (GTC) on La Palma.

Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries (ES)

But they barely detected any emission from hydrogen or oxygen or nitrogen gas. With apparently nothing to study the researchers never fully scrutinized the data.

Infrared imagery from NASA’s Wide Infrared Survey Satellite (left) show Pa 30 as a doughnut-shaped blob. Data from the European Space Agency’s XMM-Newton satellite overlaid on WISE data (middle) show powerful X-rays coming from the nebula’s central star.

The European Space Agency [La Agencia Espacial Europea] [Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganization](EU) XMM Newton X-ray Telescope.

An image taken with an Oxygen-III filter on a 2.1-meter telescope from Kitt Peak (right) only hints at the “fireworks” structure of the nebula; at the time, the Hong Kong team simply called it a “diffuse shell.”

NOIRLab KPNO 2.1 m telescope

The University of Hong Kong

Interest in the object picked up again in 2018 when some French amateur astronomers using an 8-inch scope found that the nebula was harboring a very blue star at its center. They notified one of the research groups that had observed Pa 30, a team at the University of Hong Kong (HKU), who began reanalyzing their data.

But they were beaten to publication in 2019 by a Russian team that had noted the same thing.

Bolshoi Large Altazimuth Telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences.

Using the Russian 6-meter telescope in the Caucasus Mountains, they obtained a spectrum that revealed this star had some jaw-dropping qualities: It shines with the brightness of 36,000 Suns thanks to a temperature of about 200,000 degrees Celsius (360,000 degrees Fahrenheit) at its surface, from which a wind of material zips into space at 35 million mph (57,000 km/h). Writing in Nature [below], the Russian team proposed that the star was the remnant of a double-white dwarf Type Iax supernova, spinning rapidly with a magnetic field strong enough to accelerate the winds.

Fresh evidence for a cold case

When the HKU team published their results in 2021 in The Astrophysical Journal Letters [below], they added new insights. First, they found that while the nebula didn’t have much glowing oxygen gas, it did have some sulfur. Their spectra revealed that this sulfur is traveling away from the central star at about 2.5 million mph (4 million km/hr). Assuming this is debris from the Type Iax supernova, and using the WISE image as a reference for how far this gas had traveled, they estimated that the supernova had occurred about 1,000 years ago, plus or minus about 250 years.

This, the HKU team noticed, meant Pa 30 might hold the key to solving a historical supernova mystery. In 1181, Chinese and Japanese astronomers recorded a “guest star” in this region of the sky. It was only about as bright as the brightest star — perhaps magnitude –1, rather modest for a supernova in our galaxy.

Since the 1970s, scientists had thought that the remnant of this event was a nebula called 3C 58 that housed a pulsar, a type of rapidly rotating neutron star leftover from a supernova. But that was called into question by observations in the past few decades that estimated 3C 58 was more like 2,500 years old. 3C 58 was too static in the sky and too cool to be linked to the death of a star as recent as SN 1181. Pa 30’s age, as estimated by the HKU team, was a better fit, though there was still much uncertainty.

In Chinese historical records, supernova SN 1181 was said to lie in the “lunar lodge” Kui (between the two dotted purple lines) and in between the Chinese asterisms Huagai and Chuanshe (red lines). The best estimate for SN 1181 is plotted with a blue cross, surrounded by an error circle with a radius of 5 degrees. The location of Pa 30 lies well within that circle and fits the recorded description. The University of Hong Kong.

Fesen and his colleague Bradley Schaefer of Louisiana State University saw an opportunity to do one better. Most professional observatories — and all of the ones that had so far observed Pa 30 — are only designed to use filters that allow a relatively large range of wavelengths to pass through. This is the same reason that professional astronomers never noticed the enormous oxygen emission feature right next to the Andromeda Galaxy that was recently discovered by a team of amateur astronomers using narrowband filters. (Fesen was also a co-author on that study.)

The OIII emission nebula Strottner-Drechsler-Sainty Object 1 appears next to Messier 31 as a banded teal arc in this HOLRGB image. Marcel Drechsler/Xavier Strottner/Yann Sainty.

Fesen, Schaefer, and Patchik were able to use a narrow passband Sulfur-II filter on the 2.4-meter Hiltner telescope at Kitt Peak.

2.4-meter Hiltner telescope at Kitt Peak.

It was “low-hanging fruit,” Fesen told Astronomy at the AAS meeting in Seattle. “In fact, it was so low, it was on the ground,” he joked. It is a standard technique and methodology, agrees Guest. “It’s just a nonstandard object.”

The result was stunning: With a filter capable of blocking out much more background noise, what had appeared as a hazy blob was revealed to instead be fine contrails of gas driven outward by the high winds of the central star. “It’s beautifully symmetric,” said Fesen.

The clarity of these features allowed the team to much more precisely determine how far the sulfur gas had traveled from its central star. Combining that measurement with the sulfur-derived velocity of 2.5 million mph (4 million km/hr), they could narrow down PA 30’s age: 844 years, plus or minus 55 years — nearly an exact match to the 842-year age of SN 1181. “Well, that’s ridiculously good … almost too good,” said Fesen. “Finally, we have really nailed down the remains of the star that the Chinese and Japanese saw in early August of 1181 A.D.”

Fesen and his colleagues hope to obtain follow-up observations of the object with the Hubble or James Webb space telescopes, which “should be amazing,” he said. He says the object will lend more insight into the physics of Type Iax supernovae and how exactly a star survives, of which astronomers know little.

“There’s beauty, science, and history in the story,” Fesen said. “We’ve never seen a Iax in our galaxy. So here we have one that’s just a few thousand light years away.”

The Astrophysical Journal Letters 2021
Abstract
The guest star of AD 1181 is the only historical supernova of the past millennium that is without a definite counterpart. The previously proposed association with supernova remnant G130.7+3.1 (3C 58) is in strong doubt because of the inferred age of this remnant. Here we report a new identification of SN 1181 with our codiscovery of the hottest known Wolf–Rayet star of the oxygen sequence (IRAS 00500+6713 or 2MASS J00531123+6730023, here named by us as “Parkerʼs star”) and its surrounding nebula Pa 30. Our spectroscopy of the nebula shows a fast shock with extreme velocities of ≈1100 km s−1. The derived expansion age of the nebula implies an explosive event ≈1000 yr ago that agrees with the 1181 event. The on-sky location also fits the historical Chinese and Japanese reports of SN 1181 to within 3°.5. Pa 30 and Parker’s star have previously been proposed to be the result of a double-degenerate merger, leading to a rare Type Iax supernova. The likely historical magnitude and the distance suggest the event was subluminous for normal supernova. This agrees with the proposed Type Iax association that would also be only the second of its kind in the Galaxy. Taken together, the age, location, event magnitude, and duration elevate Pa 30 to prime position as the counterpart of SN 1181. This source is the only Type Iax supernova where detailed studies of the remnant star and nebula are possible. It provides strong observational support for the double-degenerate merger scenario for Type Iax supernovae.

Nature 2019

Abstract
Gravitational-wave emission can lead to the coalescence of close pairs of compact objects orbiting each other[1*],[2]. In the case of neutron stars, such mergers may yield masses above the Tolman–Oppenheimer–Volkoff limit (2 to 2.7 solar masses)[3], leading to the formation of black holes[4]. For white dwarfs, the mass of the merger product may exceed the Chandrasekhar limit, leading either to a thermonuclear explosion as a type Ia supernova[5],[6] or to a collapse forming a neutron star[7],[8]. The latter case is expected to result in a hydrogen- and helium-free circumstellar nebula and a hot, luminous, rapidly rotating and highly magnetized central star with a lifetime of about 10,000 years[9],[10]. Here we report observations of a hot star with a spectrum dominated by emission lines, which is located at the centre of a circular mid-infrared nebula. The widths of the emission lines imply that wind material leaves the star with an outflow velocity of 16,000 kilometres per second and that rapid stellar rotation and a strong magnetic field aid the wind acceleration. Given that hydrogen and helium are probably absent from the star and nebula, we conclude that both objects formed recently from the merger of two massive white dwarfs. Our stellar-atmosphere and wind models indicate a stellar surface temperature of about 200,000 kelvin and a luminosity of about 104.6 solar luminosities. The properties of the star and nebula agree with models of the post-merger evolution of super-Chandrasekhar-mass white dwarfs[9], which predict a bright optical and high-energy transient upon collapse of the star[11] within the next few thousand years. Our observations indicate that super-Chandrasekhar-mass white-dwarf mergers can avoid thermonuclear explosion as type Ia supernovae, and provide evidence of the generation of magnetic fields in stellar mergers.
*References follow the abstract.

For further illustrations see the science paper.

The Astrophysical Journal Letters
ABSTRACT
A newly recognized young Galactic SN remnant, Pa 30 (G123.1+4.6), centered on a hot central star
with a ∼16,000 km s^−1 wind velocity has recently been proposed to be the result of a double-degenerate
merger leading to a SN Iax event associated with the guest star of 1181 CE. Here we present deep
optical [S II] λλ6716,6731 images of Pa 30 which reveal an extraordinary and highly structured nebula
170′′ in diameter with dozens of long (5′′ − 20′′) radially aligned filaments with a convergence point
near the hot central star. Optical spectra of filaments indicate a peak expansion velocity ‘1100 km s^−1
with electron densities of ≤100 to 700 cm^−3, and a thick shell-like structure resembling its appearance
in 22 μm WISE images. No Hα emission was seen ([S II] λ6716/Hα > 5), with the only other line
emission detected being faint [Ar III] λ7136 suggesting a S, Ar-rich but H-poor remnant. The nebula’s
angular size, estimated 2.3 kpc distance, and 1100 km s^−1 expansion velocity are consistent with an
explosion date around 1181 CE. The remnant’s unusual appearance may be due to the photoionization
of wind-driven ejecta due to clump-wind interactions caused by the central star’s high-luminosity wind.

For further illustrations see the science paper.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “Observe hidden gems in the constellation Orion the Hunter”

From “Astronomy Magazine”

2.10.23
Phil Harrington

Scour the sky for some new prey.

Take a seat, kick your feet up, and enjoy some of the more overlooked targets the Hunter has to offer. Credit: Roen Kelly/ Astronomy

Without a question, Orion the Hunter tops the list when it comes to renowned constellations. The reason is simple: Orion demands our attention because it is visible around the globe this time of year. Its brightest stars — Betelgeuse (Alpha [α] Orionis) and Rigel (Beta [β] Orionis) — are discernible in all but the severest light polluted skies.

Betelgeuse-a superluminous red giant star 650 light-years away in the infrared from the European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganization](EU)Herschel Space Observatory (EU) Stars like Betelgeuse, end their lives as supernovae. Credit: Decin et al. “Astronomy & Astrophysics”.

Rigel. Credit: https://www.star-facts.com/rigel/

And, visible through binoculars and telescopes, the Hunter hosts one of the sky’s most famous sights: the Orion Nebula (Messier 42).

Orion Nebula via The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL)Very Large Telescope.

In one of the most detailed astronomical images ever produced, NASA ESA’s Hubble Space Telescope captured an unprecedented look at the Orion Nebula. This extensive study took 105 Hubble orbits to complete. All imaging instruments aboard the telescope.

But there is much more to see within Orion than these familiar gems. This month, we are going to hunt for some of the Hunter’s lesser-known targets. Raise your binoculars toward Orion’s Belt.

Orion Molecular Cloud Complex showing the distinctive three stars of Orion’s belt. Credit: Rogelio Bernal Andreo Wikimedia Commons.

The three equally spaced stars that form the Belt are, from west to east, Mintaka (Delta [δ] Orionis), Alnilam (Epsilon [ε] Orionis), and Alnitak (Zeta [ζ] Orionis). These stellar belt loops are among the hottest stars visible to the unaided eye.

Mintaka (Delta [δ] Orionis). Credit: https://www.star-facts.com/mintaka/

Alnilam (Epsilon [ε] Orionis). Credit: https://www.star-facts.com/alnilam/

Alnitak (Zeta [ζ] Orionis). Credit: https://www.star-facts.com/alnilam/

As you view the scene through your binoculars, notice how the many fainter stars that surround the Belt appear to form a football-shaped pattern parallel to the Belt. An S-shaped asterism of a dozen stars winds its way from Mintaka to Alnilam; if we imagine those dim stars as a football, maybe the S is its stitching. Centered on Alnilam is a collection of more than 70 stars belonging to Collinder 70. The Collinder catalog, published in 1931 by Swedish astronomer Per Collinder, includes 471 open clusters. Some are cross listed in the Messier and NGC catalogs, while others, like Collinder 70, are not.

Collinder 70 contains more than 100 widely separated stars. For instance, Mintaka and Alnitak are estimated to lie some 900 and 800 light-years away, respectively, but Alnilam is another 400 or so light-years farther out. The stars in Collinder 70 belong to the Orion OB1 association. OB associations are loose collections of young, hot, type O and B stars often separated by tens or hundreds of light-years.

Another member of the Collinder catalog lies north of Collinder 70. Collinder 69 overlays Orion’s tiny triangular head, so it is also easy to locate. Some references call it the Lambda (λ) Orionis Cluster, since third-magnitude Lambda, also known as Meissa, is the brightest member.

Long before it was recognized as a cluster, Orion’s head drew attention. In his 1888 book Astronomy With an Opera-Glass, Garrett P. Serviss wrote, “Although there is no nebula here, yet these stars, as seen with the naked eye, have a remarkably nebulous look.”

Binoculars resolve Collinder 69 into a scattered collection of about 20 stars strewn across 70′. Three stars stand out in the field. Their equal spacing and similar brightness remind me of a miniaturized Orion’s Belt. At the center is Lambda, while Phi1 (φ1) sits to its south and 6th-magnitude HD 36881 lies to its north. The southeastern star in Orion’s head, Phi2 (φ2) Orionis, is not a cluster member.

Serviss noted a faint glimmering between Lambda and Phi1. He explained how “a field-glass shows that this twinkling is produced by a pretty little row of three stars of the eighth and ninth magnitudes.”

Serviss was wrong about one thing, however, when he said there is no nebula here. He would be amazed to learn that the entire area is engulfed in a huge glowing cloud of gas and dust cataloged as Sharpless 2–264.

The lambda Orionis region of the constellation Orion, showing molecular clouds and Betelgeuse, as well as gamma Orionis, lambda Orionis, and phi Orionis.
10 December 2017
Lithopsian

Although invisible through binoculars, it appears as a large sphere of ionized hydrogen in images.

Expand the scene to include Phi2, as well as stars HD 37232 and HD 37355 to its southeast, and you get an asterism that looks like a Recliner. That’s how reader Hope Harle-Mould near Buffalo, New York, interprets it. HD 36881 and Phi1 form the back, while Phi1 to Phi2 and those other two HDs make the seat and leg extension. So, kick up your feet and see if you can also imagine a comfy chair here.

Next month, we’ll head south for a late winter getaway. Questions, comments, suggestions are always welcome. Contact me through my website, http://philharrington.net. Until next time, remember that two eyes are better than one.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “Amateur astronomers discover enormous nebula near Andromeda”

From “Astronomy Magazine”

2.3.23
Mark Zastrow

The vast emission feature lies right next to the Andromeda Galaxy [Messier 31 or M31 for short], though researchers aren’t yet sure if they’re physically related.

The OIII emission nebula Strottner-Drechsler-Sainty Object 1 appears next to Messier 31 as a banded teal arc in this HOLRGB image. Credit: Marcel Drechsler/Xavier Strottner/Yann Sainty.

Despite being one of the most venerable and prominent objects in the night sky, the Andromeda Galaxy (M31) still has surprises. And a group of amateur astronomers have uncovered the latest: a previously unknown emission nebula lying just southeast of Andromeda and spanning half the width of the galaxy itself.

The feature was discovered in images taken last year with an Oxygen-III (OIII) filter by French astroimager Yann Sainty, who worked with Marcel Drechsler and Xavier Strottner to process and analzye the data. They have designated the feature Strottner-Drechsler-Sainty Object 1.

They then worked with a team of professional astronomers and other astroimagers to confirm the find. The team published their results in Research Notes of the AAS [below] last month — as well as a stunning, highly-processed image on the astroimaging site Astrobin (reproduced above).

A side project

The observations of Andromeda began as a side project for the trio, who had originally teamed up for another reason: Drechsler and Strottner maintain a catalog of planetary nebulae, and had asked Sainty to capture several known and candidate objects.

Sainty traveled all across France in search of the darkest sites he could find for his mobile observing setup, which includes a 4.2-inch Takahashi refractor and a CMOS astronomical camera from ZWO. After concluding this months-long project, Sainty “decided to focus on a relaxing and easy project — the Andromeda Galaxy,” Drechsler said in a statement shared with media, including Astronomy and ZWO.

“While working on the Andromeda project, Yann Sainty did something that few astrophotographers before him have done — he used an OIII filter to better bring out the faint HII regions,” said Drechsler. “Since an OIII filter is relatively new territory in astrophotography, Yann sent the data to [me] and Xavier for review. Yann’s secret hope, perhaps, was to have a previously unknown planetary nebula or supernova remnant in the data.”

When Drechsler and Strottner looked at the OIII images, they noticed “an extremely faint nebulosity … at the edge of the image that seemed to continue outside the photo.” At first, the team considered whether it was an artifact, like a gradient introduced through a faulty flat-field calibration image. But Drechsler “urged Sainty to collect more OIII data, thinking he spotted finer sub-structures in the barely-visible nebula.”

Sainty collected more images through the fall of 2022, eventually totaling 111 hours of exposure. As he did, the team began increasingly sure they had found something real — and previously unreported.

Confirming observations

The team reached out to professional astronomers to aid in verifying their discovery, including Robert Fesen of Dartmouth College in Hanover, New Hampshire. In an interview with Astronomy at last month’s meeting of the American Astronomical Society (AAS) in Seattle, Fesen pointed to the arc in an image and summed up his initial reaction: “What the hell is that?”

“When they sent it to me, I said, ‘There’s something wrong with your camera, and go fix it and leave me alone,’” he quipped. “[Dreschler] came back a couple of weeks later: ‘Rob, it’s real.’ And I said, ‘Look, you haven’t tried hard enough to kill it.’”

To confirm it, other astroimagers joined the hunt: Bray Falls working with two remote telescopes in California, Christophe Vergnes and Nicolas Martino in France, and Sean Walker (associate editor at Sky and Telescope magazine) observing with a remote telescope in New Mexico. Their results convinced Fesen: “Five different telescopes see stuff there? At different levels of resolution, but it’s in the same spot of the sky off M31? I decided it’s real.”

Remarkably, the nebula had been missed by previous OIII surveys of M31 on professional-grade telescopes, including one by the 3.6-meter Canada-France-Hawaii Telescope (CFHT) on Mauna Kea.

CFHT Telescope, Mauna Kea, Hawai’i, 4207 m (13802 ft) above sea level.

That’s because many instruments designed for research simply aren’t well-suited to spot such a faint and extended nebula.

CFHT’s MegaCam instrument has a field of view of 1° — wide by professional standards, but still not wide enough to capture the full extent of the new object, which spans 1.5°.

CFHT MegaCam

The MegaCam survey of M31 also used a filter that allowed a relatively wide range of wavelengths to pass through — over 10 nanometers. Sainty used an off-the-shelf Antlia filter with a bandwidth of just 3 nm, which better isolated the OIII signal from background noise.

Here or there?

The find has set the astronomical community ablaze with speculation about the object’s nature, including whether it is physically next to Andromeda, which is 2.5 million light-years away. It is entirely possible that the newfound object is part of the Milky Way and simply lies along our line of sight to our galactic neighbor.

One possibility that the team considered was that the feature is caused by Andromeda beginning to interact with the Milky Way. But, they wrote, “the arc seems much too close to M31 to fit that picture. More likely, it lies within M31’s halo and is related to the numerous stellar streams, especially the Giant Stellar Stream whose eastern edge lies close to the OIII arc.”

However, Fesen tells Astronomy that since then, “I have started to think it less likely to be a feature of M31, but, instead, a Milky Way nebula much closer. But who knows.”

To settle the issue, Fesen and his colleagues hope to obtain a spectrum with a professional-grade observatory. From this, they can measure any Doppler shift in the light caused by motion toward or away from the Milky Way — and whether it matches the motion of Andromeda itself.

Whether or not the arc is ultimately associated with Andromeda, the discovery highlights the role that amateur astronomers and imagers with widely available high-quality narrowband filters are playing in discovering faint, extended emission nebulae.

Fesen expressed admiration for the imagers, who, he notes, are taking data that totals exposures of “fractions of a day or more.” He pointed to one of the confirmation images: “That one picture’s 86 hours. Are you kidding me? [Sainty’s image] was taken over 22 nights over three months of clear weather. This is insane.”

Research Notes of the AAS

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “Supermassive black holes can be kicked off-center in bright galaxies”

From “Astronomy Magazine”

1.30.23
Paul Sutter

Black hole and its accretion disk. Image credit NASA Dana Berry SkyWorks Digital.

The largest black holes in the universe can have masses hundreds of millions of times that of the Sun. So, it understandably takes a lot of force to move one of those things.

Nonetheless, new research reveals that it’s surprisingly common for supermassive black holes to be flung far from the centers of their host galaxies. In fact, according to a new study in MNRAS [below], it seems that up to one-third of the biggest black holes get pushed around like this.

Black holes and their host galaxies: A complicated relationship

Observations suggest that almost every galaxy in the universe hosts its own giant black hole, which are called, appropriately enough, supermassive black holes. Even our own Milky Way galaxy has one of its known, Sagittarius A*, which sits about 26,000 light-years away and holds a mass of some 4 million Suns.

This is the first image of Sagittarius A* – [SGR A*] the supermassive black hole at the center of the Milky Way. Credit: The Event Horizon Telescope Collaboration.

These monsters are by far the largest objects in their host galaxies.

While supermassive black holes don’t largely affect the rest of the galaxy directly through their gravity (even the biggest black holes weigh less than 1 percent of their host galaxy), they can influence the overall temperature and rate of star formation of their galaxy. That’s because supermassive black holes are capable of devouring enormous amounts of material and ejecting heat and energy back into their surrounding galaxy.

Researchers have long believed that there’s an intimate connection between galaxies and their supermassive black holes, since they tend to follow a proportional relationship in their mass: The bigger the galaxy, the bigger the black hole. And so the largest supermassive black holes belong to the largest galaxies, which tend to be found in the centers of enormous clusters of galaxies.

These giant galaxies, known as brightest cluster galaxies (BCGs), evolve through the merger and subsequent cannibalization of many smaller galaxies throughout their lifetime. Because they sit at the center of clusters, BCGs often interact with other members of the galaxy cluster that happen to swing by. And if those other galaxies come too close, they are absorbed into the larger BCG.

Those cannibalized galaxies carry along with them their own supermassive black holes. And after merging, the smaller galaxy’s black hole eventually finds its way down to the center of the BCG and merges with the already monstrous black hole there. In fact, this kind of merging process helps explain why both the BCGs and their supermassive black holes can reach such astronomical sizes.

But not all galaxy and black hole mergers go smoothly.

Repeated galaxy collisions give black holes a kick

A team of astrophysicists at the Sorbonne University in Paris used state-of-the-art simulations of galaxy formation combined with simple models of black hole interactions to find out what happens when galaxies repeated collide with BCGs.

The team found that, occasionally, the infalling galaxy is capable of completely disrupting the supermassive black hole at the center of the BCG. That’s because, if the interloping galaxy is massive enough and makes a beeline right for the center, it can get stuck orbiting within the core region of the BCG before it completely merges.

As its in the process of merging, the swallowed remnant galaxy wreaks havoc, with continued gravitational interactions raising the energies of everything in the BCG’s core, including the supermassive black hole that resides there. In some cases, the researchers found, these interactions “kicked” the black hole out as much as hundreds of thousands of light-years from the core — outside the BCG itself!

This figure from the new research plots the timing (in gigayears, or billions of years) and distance kicked (in kiloparsecs, with 100 kpc equal to 326,156 light-years) for a black hole that’s experienced more than a dozen merger events. MNRAS.

These kinds of unlucky interactions are relatively rare, but the life of a BCG is nothing but merger after merger, so over the course of billions of years, it’s quite common for a BCG’s central black hole to become dislodged at some point.

Most of the time, the black hole makes its way back down to the core where it can finally rest. But the researchers found that a third of all BCGs currently have displaced supermassive black holes in the present era, with some of those black holes not expected to return to their homes for another 6 billion years.

Supermassive black holes: An inconsistent role

This new work may hold important consequences for future research into the relationship between supermassive black holes and their host galaxies. Most models of galaxy formation today include the effects of feedback from giant black holes, where the black holes consume raw gas and occasionally spit radiation back out into their galaxies. But those models assume that the supermassive black holes stay at the cores of their host galaxies for billions of years straight.

But if a black hole gets kicked away from its galactic core it may find itself in a much less dense environment. Without new material to reliably consume, the black hole can’t fuel the cosmic engine that usually floods its host galaxy with radiation. The entire feedback cycle largely shuts down.

It remains to be seen how much of an impact these new results have. But future simulations will incorporate the fact that many black holes might spend a significant amount of time away from the centers of their host galaxies. And those results could help shed light on the complex relationship that exists between galaxies and their supermassive black holes.

MNRAS
See the science paper for instructive material with images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “What happens when we detect alien life?”

From “Astronomy Magazine”

1.19.23
FROM THE May 2012 ISSUE

Seth Shostak | SETI Institute

Scientists have been listening for signals from extraterrestrial civilizations for decades but what would they do if they actually heard one?

NASA Voyager Golden Record. The Voyager Golden Records are two phonograph records that were included aboard both Voyager spacecraft launched in 1977.

National Aeronautics and Space Administration Voyager 1.

National Aeronautics and Space Administration Voyager 2.

National Aeronautics and Space Administration Heliosphere-heliopause showing positions of two Voyager spacecraft. Credit: NASA/JPL-Caltech.

The Sun-like star Epsilon (ε) Eridani was one of Frank Drake’s first targets in his search for extraterrestrial intelligence. Astronomers have since learned that the star anchors the closest known planetary system, depicted in this artist’s conception, but no detectable life. Credit: NASA/JPL-Caltech

Frank Drake with his Drake Equation. Credit Frank Drake.

Drake Equation, Frank Drake, Seti Institute.

We’ve never heard a peep from aliens. But improved technology is speeding up the search for extra- terrestrial intelligence (SETI), so what happens if today’s silence suddenly gives way to tomorrow’s discovery?

“Wow!” signal from Ohio State Big Ear Radio Telescope Aug. 15, 1977.

Ohio State Big Ear Radio Telescope, Construction of the Big Ear began in 1956 and was completed in 1961, and it was finally turned on for the first time in 1963, disassembled in 1998 having operated for over 30 years.

SETI Institute

LaserSETI observatory installation at Haleakala Observatory in Maui, Hawai’i, aimed East.

The Nickel 1-meter Telescope at Lick Observatory which includes the NIROSETI instrument which saw first light on March 15, 2015. © Laurie Hatch.

Alumna Shelley Wright, now an assistant professor of physics at UC San Diego (US), discusses the dichroic filter of the NIROSETI instrument, developed at the U Toronto Dunlap Institute for Astronomy and Astrophysics (CA) and brought to UCSD and installed at the UC Santa Cruz (US) Lick Observatory Nickel Telescope (Photo by Laurie Hatch).

Shelley Wright of UC San Diego with (US) NIROSETI, developed at U Toronto Dunlap Institute for Astronomy and Astrophysics (CA) at the 1-meter Nickel Telescope at Lick Observatory at UC Santa Cruz

NIROSETI team from left to right Rem Stone UCO Lick Observatory Dan Werthimer, UC Berkeley; Jérôme Maire, U Toronto; Shelley Wright, UCSD; Patrick Dorval, U Toronto; Richard Treffers, Starman Systems. (Image by Laurie Hatch).

Would the world rejoice in the news that someone’s out there? Would euphoria engulf humanity, as Nobel Prizes are doled out like after-dinner mints?

That’s one view. But many people think the dis- covery would be hushed up as quickly as a Mafia informant, assuming that the public couldn’t handle the news. Or scarier still, kept secret for fear that an unauthorized response would tell a hostile race exactly where to send their interstellar battlewagons.

That’s melodramatic enough. But has any serious consideration gone into what happens when our efforts to detect cosmic intelligence pay off and we find a blip of a signal in the sea of radio noise that pours into the SETI antennas?

Some think that addressing that question — even in a speculative way — is hubristic at best and wildly pre- sumptuous at worst. After all, SETI scientists have been torquing their telescopes toward celestial targets for more than half a century without ever detecting such a signal. If we haven’t won the E.T. lottery in all that time, why worry about what would happen if we got the winning ticket?

Simple: SETI researchers are buying more tickets all the time, and the chances of scoring the big one keep going up. As computer power improves and new detection technology comes out of the labs, the search is accelerating. Unless the aliens are excessively secretive or simply nonexistent, we could find evidence for their presence within decades.

So, again, then what?

SETI Institute Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, Altitude 986 m (3,235 ft), the origins of the Institute’s search.

The Allen Telescope Array and the Jansky Very Large Array (pictured) are powerful enough to detect and pinpoint a possible extraterrestrial transmission with a high degree of accuracy. The latter hosts 27 antennas, while the former boasts 42 and plans to have 350 upon completion.Credit: Dave Finley/AUI/NRAO/NSF.

Immediate reactions

In the spring of 1960, astronomer Frank Drake performed the first modern SETI experiment, whimsically dubbed Project Ozma after L. Frank Baum’s fictional queen of Oz. What few people realize is that he actually detected something. While pointing his antenna at the nearby Sun-like star Epsilon (ε) Eridani, Drake heard a strong hammering signal. Surprised by how quickly his search succeeded, he wondered, “What do we do now?”

Drake answered his own question by rigging up additional equipment, and he soon proved that the throbbing bleats from his loudspeaker were terrestrial interference, not Eridanians trying to phone our home.

Project Ozma could tune to only one frequency at a time, but today’s SETI receivers simultaneously monitor hundreds of millions of channels. Consequently, picking up a signal is neither remarkable nor rare: A few dozen typically come up with each scan. Naturally, no one gets very excited about this. Instead, researchers rely on sophisticated software to perform the tedious task of deciding whether these signals are likely to be alien intelligence or (as in Drake’s case) just more human-caused radio static.

Only rarely does any signal survive this automatic scrutiny. But if and when that happens, a series of additional tests occurs. Eventually, the astronomers running the experiment ask someone at another observatory to verify the detection — to rule out equipment bugs, coding errors, or pranks.

The scenario for handling a signal is briefly described in a document developed under the auspices of the International Academy of Astronautics, and referred to as “SETI detection protocols.” These “best practices” boil down to this: (1) carefully verify that the signal is truly extraterrestrial, (2) inform other scientists and the public, and (3) seek international approval before transmitting any reply.
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Abridged SETI detection protocols

Confirmed detections:

If the verification process confirms that a signal is due to extraterrestrial intelligence, the discoverer shall report this conclusion in a full and complete open manner to the public, the scientific community, and the Secretary General of the United Nations. All data necessary for the confirmation of the detection should be made available to the international scientific community through publications, meetings, conferences, and other appropriate means.

The discovery should be monitored. Any data bear- ing on the evidence of extraterrestrial intelligence should be recorded and stored permanently to the greatest extent feasible and practicable.

If the evidence of detection is in the form of electromagnetic signals, observers should seek international agreement to protect the appropriate frequencies by exercising the extraordinary procedures established within the World Administrative Radio Council of the International Telecommunication Union.

Post detections:

A Post Detection Task Group under the auspices of the SETI Permanent Committee has been established to assist in matters that may arise in the event of a confirmed signal, and to support the scientific and public analysis by offering guidance, interpretation, and discussion of the wider implications of the detection.

Response to signals:

In the case of the confirmed detection of a signal, signatories to this declaration will not respond without first seeking guidance and consent of a broadly representative international body, such as the United Nations.

(From the International Academy of Astronautics Commission 1 “Space Physical Sciences” Meeting on October 2, 2011)
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Not so fast

These are all patently good ideas that seem to suggest that everyone would handle a discovery soberly. However, such interesting signals are bound to provoke a response that’s both messy and confused because verification will take many days, at the least.

During all that time, word of the possible detection will surely spread via blogs and tweets from the researchers themselves (there’s no policy of secrecy in SETI). So you can bet that long before any official press conference announcing that we’ve found the aliens, you’ll have heard about it many times over. Indeed, you should brace yourself for plenty of future false alarms caused by signals that — at first blush — look promising. This has occurred in the past and shows the error of those who think that a discovery could be covered up.

Any real detection would be a headliner, everyone agrees. SETI practitioner Paul Horowitz of Harvard University in Cam- bridge, Massachusetts, says it would “easily be the most interesting discovery in human history. Journalists would go wild, at least for a month or two.”

Astronomer Jill Tarter, who heads the SETI Institute’s listening efforts in Mountain View, California, concurs: “The general public will be in an excited state for a while, fueled by the media. But UFO enthusiasts will yawn because they knew it all along.”

A public reaction of initial enthusiasm, and not mayhem, has precedent. Consider the 1996 announcement that NASA scientists had found fossilized martian microbes in a meteorite. That story ran in The New York Times with billboard-sized headlines for three days. The public’s reaction to the possible detection of life beyond Earth? “That’s interesting. Tell us more.”

The meteorite story was a stunted reprisal of astronomer Percival Lowell’s reports of martian canals a century earlier. Again, people were tantalized, but few seemed to panic.

When astronomers announced that a martian rock contained fossilized microbes (the tube-like structures, less than one-hundredth the width of a human hair) in 1996, the public proved itself capable of “handling” an extraterrestrial discovery. Credit: NASA.

Early results

Of course, in 1996 no one felt threatened by dead protozoans, even if they were from Mars. But SETI searches for intelligent life, and given that human beings are still the new kids on the technological block (consider that we’ve only had radio technology for a hundred years), you can be pretty sure that anyone we hear will be more advanced than us — possibly much more advanced.

That might sound unsettling, but most people don’t see it that way. A 2005 survey by the National Geographic Channel, the SETI Institute, and the University of Connecticut found that 72 percent of Americans said they would feel “excited and hopeful” to learn about a signal from E.T. Only 20 percent confessed they would be “anxious and nervous.”

Again, perhaps that’s not too surprising, given that any transmission we discover likely will be from beings many hundreds of light-years distant, a seemingly safe remove. And, at first, we won’t know much more than the signal’s existence.

But you can bet your paycheck that every telescope on Earth will aim straight for the transmission. Is a star waiting there? Does it have planets? In the rush to learn more, even a stalled project like NASA’s Terrestrial Planet Finder might see new life as scientists shake it out of its comatose state, infuse it with new vigor, and hurl it into orbit.

NASA’s Terrestrial Planet Finder depiction.

There are some things we could learn quickly about the signal’s source. Within a thousand light-years lie tens of millions of stars. Consequently, a few arcminutes separate them in the sky, on average. A high-resolution radio telescope, such as the Jansky Very Large Array in New Mexico [above], has a beam size of about 5 arc seconds at the commonly used SETI frequency of 1420 megahertz. It would have little difficulty pinpointing which star hosts the detected aliens. We’ll know exactly where they live.

And that’s not all. Two decades ago, radio astronomers Jim Cordes and Woodruff Sullivan considered what we might learn by looking at the subtle variations of any alien signal. This includes small frequency shifts due to the Doppler effect (which alters a signal’s frequency according to its motion), as well as intensity changes due to the atmosphere of E.T.’s planet or simply its daily rotation.

Careful measurement could theoretically pin down the length of the aliens’ day and year, the size of their world, the presence of moons, and possibly even information about their atmosphere and magnetic field.

Initial questions

All of that would be tasty fodder for the technically inclined, but everyone else is going to ask an obvious question: What are the aliens saying? That, of course, assumes that they’re saying anything — that they’ve included a message in the signal. After all, the extraterrestrials might withhold commentary if they want us to reply first, perhaps so they can gauge what level of conversation is appropriate.

But let’s suppose that E.T. is trying to tell us something. Just getting the message “bits” could be hard. SETI observations add up incoming static for seconds or minutes to increase the sensitivity to weak signals.

This is completely analogous to astronomical photography — the longer the exposure time, the fainter the stuff you can image. Unfortunately, just as a long exposure would obliterate the rapid flashes of an optical pulsar, so too would these long SETI observations smooth away any message. If, for example, the alien transmission included a television-type signal, researchers would need an antenna roughly 10,000 times larger than most of today’s radio telescopes to see the picture. Building such an enormous antenna would require impressive amounts of money and time. However, after a signal’s detection, it’s reasonable to assume that research money would be practically unlimited, unlike today’s situation.

In the meantime, the public would be confronted with the fact of cosmic company. We wouldn’t know what they’re like, nor what we might learn from them, only that they exist. Anthropologist Ben Finney of the University of Hawaii at Manoa has predicted that an “interpretation industry” would quickly sprout — facile pundits who, out of conviction or merely greed, will explain to the masses what contact means and how we should feel about it.

And in particular, how should religions react? Research in this area is lacking, but most mainstream theologians have expressed the upbeat view that our belief systems could adapt. As Vatican Observatory astronomer Brother Guy Consolmagno has said, “If your religion has survived millennia — if it can handle Copernicus, Galileo, and even Darwin — then E.T. should eventually prove palatable.”

Mainstream religion might easily incorporate the discovery, but fundamentalists will have a harder time. They are less willing to accept a cosmic circumstance that’s not found in scripture. And unless you’re inclined to consider seraphim, nephilim, or angels as alien beings, most religions don’t anticipate the presence of intelligent life on other worlds (an exception is The Church of Jesus Christ of Latter Day Saints).

The fundamentalists would likely rail against the discovery, claiming it’s “just Satan, tempting you,” according to sociologist Bill Bainbridge of George Mason University in Fairfax, Virginia.

Significance sets in

Without doubt, learning of other beings among the star fields of the Milky Way would be discomfiting to some. But the most profound consequences of a SETI detection would surely be the long-term impacts. And these would affect everyone.

The degree to which a signal would alter the lives of our descendants depends on whether we could decode any attached message. This might sound like a tractable problem — merely a matter of time and effort. After all, humans eventually deciphered hieroglyphics, Linear B, and other “messages” that once seemed as inscrutable as teenage behavior. But the universe is old, and consequently the content of any message might simply be incomprehensible to our 3-pound hominid brains.

Still, let’s take the sunny view and assume that we eventually learn what the aliens are saying. Because, as noted, they’re likely to be well in advance of us, the information might include such practical topics as all of Physics and Astronomy, the extent and nature of Cosmic Biology and intelligence, the whether and how of faster-than- light travel, and many other things that are the provenance of science fiction today. To suddenly learn such matters would trigger a sharp discontinuity in our species’ history — a kind of “wormhole” to a future that we might otherwise reach only after thousands or millions of years.

Aside from such a torrent of knowledge, we would confront the fact that the differences among humans are of trivial import compared to the gulf between extra-terrestrials and ourselves. Some people, such as SETI’s Tarter, suggest that this would lead to more human harmony and less worry that we’re on the road to destruction. After all, if they’ve survived their technical adolescence, then we could, too.

Sociologist Don Tarter of the University of Alabama, Huntsville, is less sanguine. He notes that the idea of the world’s peoples coming together in sweetness and light — popular in the early days of space exploration with the first pictures of Earth as a small blue orb against a vast, dark sky — was shattered by subsequent wars and terrorist attacks. We’re back to the usual conflict and competition.

And what about a response? If we know where the aliens live, do we dare reply with our own shout out? Or would that, as some aver [Stephan Hawking, among others], merely expose our planet to possible future destruction because we’ve given away our existence and position?

In fact, while no one can say whether aliens would be peaceable or pugnacious, we’ve been sending radio, television, and (most visibly) radar signals into space inadvertently for more than 90 years. Any society that has the capability to travel interstellar distances and threaten our world could easily pick up these “leaked” signals. Indeed, by using their own sun as gravitational lens, the nearest could theoretically see the lights from our cities. Any deliberate reply from us would simply add to information they already have.

The great unknown

Frankly, predicting the truly durable consequences of a SETI success is a fool’s errand. Consider if members of the Spanish court in 1492 had written a treatise on what the discovery of a new continent might eventually mean. An interesting exercise, but not one likely to have much currency a few hundred years down the road.

But this much we can say: If SETI succeeds, we’ll have proof that biology is as much a part of the cosmos as pulsars and pockmarked planets. And, while instant brotherhood is unlikely to erupt suddenly on Earth, we’ll at least know we’re neither the crown of creation nor even particularly exceptional. For as long as our species exists, we’ll be aware that we’re just one more duck in a row.

And you can be sure that news will ruffle a few feathers.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “Fiber optics help scientists take the pulse of our planet”

From “Astronomy Magazine”

12.22.22
Carolyn Wilke

It’s like radar but with light. Distributed acoustic sensing — DAS — picks up tremors from volcanoes and quaking ice and deep-sea faults as well as traffic rumbles and whale calls.

Researchers are using fiber optics to monitor vibrations — including in remote places like this site in Greenland, where a team is drilling into an ice sheet to remove a core of ice. Last summer, scientists lowered a cable 1,500 meters into the borehole and captured the rumblings produced by bedrock and ice rubbing together. Credit: Andreas Fichtner.

Andreas Fichtner strips a cable of its protective sheath, exposing a glass core thinner than a hair — a fragile, 4-kilometer-long fiber that’s about to be fused to another. It’s a fiddly task better suited to a lab, but Fichtner and his colleague Sara Klaasen are doing it atop a windy, frigid ice sheet.

After a day’s labor, they have spliced together three segments, creating a 12.5-kilometer-long cable. It will stay buried in the snow and will snoop on the activity of Grímsvötn, a dangerous, glacier-covered, Icelandic volcano.

Sitting in a hut on the ice later on, Fichtner’s team watches as seismic murmurs from the volcano beneath them flash across a computer screen: earthquakes too small to be felt but readily picked up by the optical fiber. “We could see them right under underneath our feet,” he says. “You’re sitting there and feeling the heartbeat of the volcano.”

Researchers Sara Klaasen and Andreas Fichtner splice optical fibers in the back of a vehicle atop an Icelandic glacier. It is tricky work for cold hands in a harsh environment. Credit: Hildur Jonsdottir.

Fichtner, a geophysicist at the Swiss Federal Institute of Technology in Zürich, is one of a cadre of researchers using fiber optics to take the pulse of our planet. Much of this work is being done in remote places, from the tops of volcanoes to the bottoms of the seas, where traditional monitoring is too costly or difficult. There, in the last five years fiber optics have started to shed light on seismic rumblings and ocean currents and even animal behaviors.

Grímsvötn’s ice sheet, for example, sits on a lake of water thawed by the volcano’s heat. Data from the new cable reveal that the floating ice field serves as a natural loudspeaker, amplifying tremors from below. The work suggests a new way to eavesdrop on the activity of volcanoes that are sheathed by ice — and so catch tremors that may herald eruptions.

Like radar but with light

The technique used by Fichtner’s team is called distributed acoustic sensing, or DAS. “It’s almost like radar in the fiber,” says physicist Giuseppe Marra of the United Kingdom’s National Physical Laboratory in Teddington, England. While radar uses reflected radio waves to locate objects DAS uses reflected light to detect events, from seismic activity to moving traffic, and to determine where they occurred.

It works like this: A laser source at one end of the fiber shoots out short pulses of light. As a pulse moves along the fiber, most of its light continues forward. But a fraction of the light’s photons bang into intrinsic flaws in the fiber — spots of abnormal density. These photons scatter, some of them traveling all the way back to the source, where a detector analyzes this reflected light for hints about what occurred along the fiber’s length.

An optical fiber for DAS typically stretches several to tens of kilometers and it moves or bends in response to disturbances in the environment. “It wiggles as cars go by, as earthquakes happen, as tectonic plates move,” says earth scientist Nate Lindsey, coauthor of a 2021 article on fiber optics for seismology in The Annual Review of Earth and Planetary Sciences [below]. Those wiggles change the reflected light signal and allow researchers to tease out information such as how an earthquake bent a cable at a certain point.

An optical cable captures vibrations, for instance, of seismic tremors along its whole length. In contrast, a typical seismic sensor, or seismometer, relays information from only one spot. And seismometers can be costly to deploy and difficult to maintain, says Lindsey, who works at a company called FiberSense that is using fiber-optic networks for applications in city settings.

Whether it’s under a city or on top of a remote glacier, an optical cable will wiggle when disturbed — for instance, by the motion of traffic or of seismic waves. Distributed acoustic sensing, or DAS, captures those tiny movements. Laser light pulses are sent out from the interrogator into the fiber. As they travel, some photons hit defects in the fiber, which scatters them, and some of this scattered light makes it back to the source. Analyzing this “backscattered pulse” and comparing it with the light that was originally sent out allows researchers to detect environmental events. Credit: Knowable Magazine

DAS can provide about 1 meter resolution, turning a 10-kilometer fiber into something like 10,000 sensors, Lindsey says. Researchers can sometimes piggyback off existing or decommissioned telecommunications cables. In 2018, for example, a group including Lindsey, who was then at UC Berkeley and Lawrence Berkeley National Laboratory, turned a 20-kilometer cable operated by the Monterey Bay Aquarium Research Institute — normally used to film coral, worms and whales — into a DAS sensor while the system was offline for maintenance.

“The ability to just go under the seafloor for tens of kilometers — it is remarkable that you can do that,” Lindsey says. “Historically, deploying one sensor on the seafloor can cost $10 million.”

During their four-day measurement, the team caught a 3.4-magnitude earthquake shaking the ground some 30 kilometers away in Gilroy, California. For Lindsey’s team, it was a lucky strike. Earth scientists can use seismic signals from earthquakes to get a sense of the structure of the ground that the quake has traveled through, and the signals from the fiber-optic cable allowed the team to identify several previously unknown submarine faults [Science (below)]. “We’re using that energy to basically illuminate this structure of the San Andreas Fault,” Lindsey says.

Eavesdropping on cities and cetaceans

DAS was pioneered by the oil and gas industry to monitor wells and detect gas in boreholes, but researchers have been finding a variety of other uses for the technique. In addition to earthquakes, it has been harnessed to monitor traffic and construction noise in cities [Geophysical Research Letters (below)]. In densely populated metropolises with significant seismic hazards, such as Istanbul, DAS could help to map the sediments and rocks in the subsurface to reveal which areas would be the most dangerous during a large quake, Fichtner says. A recent study even reported eavesdropping on whale songs using a seabed optical cable near Norway [Frontiers in Marine Science (below)].

Cutting a trench for fiber-optic cable.
Fichtner’s team buried their fiber-optic cable on Grímsvötn. In this video, they are trenching the first few hundred meters with a chainsaw because this part of the caldera rim is too steep for their snow-grooming vehicle. Credit: Andreas Fichtner.

But DAS comes with some limitations. It’s tricky to get good data from fibers longer than 100 kilometers. The same flaws in the cables that make light scatter — producing the reflected light that is measured — can deplete the signal from the source. With enough distance traveled, the original pulse would be completely lost.

But a newer, related method may provide an answer — and perhaps allow researchers to spy on a mostly unmonitored seafloor, using existing cables that shuttle the data of billions of emails and streaming binges.

In 2016, Marra’s team sought a way to compare the timekeeping of ultraprecise atomic clocks at distant spots around Europe. Satellite communications are too slow for this job, so the researchers turned to buried optical cables instead. At first, it didn’t work: Environmental disturbances introduced too much noise into the messages that the team sent along the cables. But the scientists sensed an opportunity. “That noise that we want to get rid of actually contains very interesting information,” Marra says.

On a glacier above Iceland’s Grímsvötn volcano, Andreas Fichtner and Sara Klaasen unroll a spool of fiber-optic cable. They will eventually lay down some 12 kilometers of the cable for distributed acoustic sensing. Credit: Kristin Jonsdottir.

Using state-of-the-art methods for measuring the frequency of light waves bouncing along the fiber-optic cable, Marra and colleagues examined the noise and found that — like DAS — their technique detected events like earthquakes through changes in the light frequencies.

Instead of pulses, though, they use a continuous beam of laser light. And unlike in DAS, the laser light travels out and back on a loop; then the researchers compare the light that comes back with what they sent out. When there are no disturbances in the cable, those two signals are the same. But if heat or vibrations in the environment disturb the cable, the frequency of the light shifts.

With its research-grade light source and measurement of a large amount of the light initially emitted — as opposed to just what’s reflected — this approach works over longer distances than DAS does. In 2018, Marra’s team demonstrated that they could detect quakes with undersea and underground fiber-optic cables up to 535 kilometers long [Science (below)], far exceeding DAS’s limit of around 100 kilometers.

This offers a way to monitor the deep ocean and Earth systems that are usually hard to reach and rarely tracked using traditional sensors. A cable running close to the epicenter of an offshore earthquake could improve on land-based seismic measurements, providing perhaps minutes more time for people to prepare for a tsunami and make decisions, Marra says. And the ability to sense changes in seafloor pressure may open the door to directly detecting tsunamis too.

On Grímsvötn, a research team prepares to deploy a cable onto a floating ice field on the volcano’s caldera. Data from that cable have revealed that the ice field acts as a loudspeaker, amplifying seismic tremors from below. Credit: Andreas Fichtner.

In late 2021, Marra’s team managed to sense seismicity across the Atlantic on a 5,860-kilometer optical cable running on the seafloor between Halifax in Canada and Southport in England. And they did so with far greater resolution than before, because while earlier measurements relied on accumulated signals from across the entire submarine cable’s length, this work parsed changes in light from roughly 90-kilometer spans between signal-amplifying repeaters.

Fluctuations in intensity of the signal picked up on the transatlantic cable appear to be tidal currents [Science (below)]. “These are essentially the cable being strummed as a guitar string as the currents go up and down,” Marra says. While it’s easy to watch currents at the surface, seafloor observations can improve an understanding of ocean circulation and its role in global climate, he adds.

So far, Marra’s team is alone in using this method. They’re working on making it easier to deploy and on providing more accessible light sources.

Researchers are continuing to push sensing techniques based on optical fibers to new frontiers. Earlier this year, Fichtner and a colleague journeyed to Greenland, where the East Greenland Ice-Core Project is drilling a deep borehole into the ice sheet to remove an ice core. Fichtner’s team then lowered a fiber-optic cable 1,500 meters, by hand — and caught a cascade of icequakes, rumbles that result from the bedrock and ice sheet rubbing together.

Icequakes can deform ice sheets and contribute to their flow toward the sea. But researchers haven’t had a way before now to investigate how they happen: They are invisible at the surface. Perhaps fiber optics will finally bring their hidden processes into the light.

Science papers:

Science 2018
Science
Geophysical Research Letters 2020
Frontiers in Marine Science
See the above science paper for instructive material with images.

Science article:
The Annual Review of Earth and Planetary Sciences 2021
See the science article for instructive material with images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From “Astronomy Magazine” : “The universe may be more unstable than you think”

From “Astronomy Magazine”

12.16.22
Paul Sutter

The cosmos is considered metastable which means there is a chance it could fall apart — or it already has.

sakkmesterke/Shutterstock

Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey.

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Apache Point Observatory
SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft).

Apache Point Observatory near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft).
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The ultimate stability of the vacuum of our universe may rest on the masses of two fundamental particles, the Higgs boson — that inhabits all space and time — and the top quark. The latest measurements of those masses reveals that our universe is metastable, meaning that it can persist in its present state essentially forever… or not.

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Higgs

Higgs in Standard Model of Particle Physics

European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) ATLAS Higgs Event June 18, 2012.

European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)CMS Higgs Event May 27, 2012.

Peter Higgs – University of Edinburgh [Oilthigh Dhùn Èideann] (SCT).

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Vacuum expectations

Our universe has not always been the same. In the earliest moments of the Big Bang, when our cosmos was a mere fraction of its current size, the energies and temperatures were so enormously high that even the fundamental rules of physics were completely different. Most notably, physicists believe that at one time, all four forces of nature (gravity, electromagnetism, strong nuclear and weak nuclear) were merged into a single, unified force.

The nature of that unified force remains a mystery, but as the universe expanded and cooled from initial state, the forces peeled off from each other. First came gravity, then strong nuclear, and lastly electromagnetism and the weak nuclear force split from each other. That last step we can recreate in the lab. In our most powerful particle colliders, we can achieve the energies needed to – temporarily, at least – recombine those forces into a single “electroweak” force.

Each time the forces divided, the cosmos underwent a radical phase transition, populated by new particles and forces. For example, the unified electroweak force is carried by a quartet of massless particles, but the electromagnetic force is carried by a single massless particle, the photon, while three massive particles carry the weak nuclear. If those two forces hadn’t split, then life as we know it, which depends on electromagnetic interactions to glue atoms together into molecules, simply wouldn’t exist.

The universe has not undergone such a reshuffling of fundamental forces in over 13 billion years, but that doesn’t mean it’s not capable of playing the same tricks again.

The deciding Higgs boson

The current stability of the vacuum depends on how ultimate that splitting of the electroweak force was. Did that splitting bring the universe to its final, lowest-energy ground state? Or is it merely a pitstop on the road of its further evolution?

The answer comes down to the masses of two fundamental particles. One is the Higgs boson, which plays a major role in physics: Its existence triggered the separation of the electromagnetic and weak nuclear forces all those billions of years ago.

At first, when our universe was hot and dense, the Higgs stayed in the background, allowing the electroweak force to rule unimpeded. But once the universe cooled beyond a certain point, the Higgs made its presence known, and interfered with that force, creating a separation that has been maintained ever since. The mass of the Higgs boson determined when that splitting happened, and it regulates how “strong” that separation is today.

But the Higgs plays another major role in physics: By interacting with many other particles, it gives those particles mass. How strongly a particle connects to the Higgs governs that particle’s mass. For example, the electron barely talks to the Higgs at all, so it gets a light mass of 511 MeV. On the other end of the spectrum, the top quark interacts with the Higgs the most, making it the heaviest object in the Standard Model of particle physics, weighing in at 175 GeV.

Standard Model of Particle Physics, Quantum Diaries.

In particle physics, particles are constantly interacting and interfering with all the other kinds of particles, but the strength of those interactions depend on the particle masses. So, when we try to evaluate anything involving the Higgs boson – like, say, its ability to maintain the separation between the electromagnetic and weak nuclear forces – we also need to pay attention to how the other particles will interfere with that effort. And since the top quark is handily the biggest of the bunch (the next largest, the bottom quark, weighs a mere 5 GeV) it’s essentially the only other particle we need to care about.

Stability of the universe

When physicists first calculated the stability of the universe, as determined by the Higgs boson’s ability to maintain the separation of the electroweak force, they didn’t know the mass of either the Higgs itself or the top quark. Now we do: The top quark weighs around 175 GeV, and the Higgs around 125 GeV.

Plugging those two numbers into the stability equations reveals that the universe is… metastable. This is different than stable, which would mean that there’s no chance of the universe splitting apart instantly, but also different than unstable, which would mean it already happened.

Instead, the universe is balanced in a rather precarious position: It can remain in its present state indefinitely, but if something were to perturb spacetime in just the wrong way, then it would transform to a new ground state.

What would that new state look like? It’s impossible to say, as the new universe would feature new physics, with new particles and new forces of nature. But it’s safe to say that life would be different, if not completely impossible.

What’s worse, it may have already happened. Some corner of the cosmos may have already begun the transition, with the bubble of a new reality expanding outwards at the speed of light. We wouldn’t know it hit us until it already arrived. Sleep tight!

See the full article here .

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Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.