From SPACE.com: “McDonald Observatory: Searching for Dark Energy”

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From SPACE.com

McDonald Observatory is a Texas-based astronomical site that has made significant contributions in research and education for more than 80 years.

Administered by the University of Texas at Austin, the McDonald Observatory has several telescopes perched at an altitude of 6791 feet (2070 meters) above sea level on Mount Locke and Mount Fowlkes, part of the Davis Mountains in western Texas, about 450 miles (724 kilometers) west of Austin. McDonald “enjoys the darkest night skies of any professional observatory in the continental United States,” according to a news release issued for the observatory’s 80th anniversary.

McDonald is home to the Hobby-Eberly Telescope, one of the world’s largest optical telescopes, with a 36-foot-wide (11 meter) mirror.

A visitor center offers daytime tours of the grounds and big telescopes, daytime solar viewing, a twilight program in an outdoor amphitheater, and nighttime star parties with telescope viewing.

The observatory is also known for its daily StarDate program, which runs on more than 300 radio stations across the country.

The gift of an observatory

The regents of the University of Texas were surprised when they opened the will of William Johnson McDonald, a banker from Paris, Texas, who died in 1926. He had left the bulk of his fortune to the university for the purpose of building an astronomical observatory. After court proceedings were done, about $850,000 (the equivalent of $11 million today) was available, according to the Texas State Historical Association.

“McDonald is said to have thought that an observatory would improve weather forecasting and therefore help farmers to plan their work,” the association said.

But there were two major challenges to overcome before McDonald’s wish could become reality. First, the money was enough to build an observatory but not enough to run it, so the university would need to acquire more funds. Second, at that time, the University of Texas had no astronomers on its faculty, so it needed to recruit a team of space experts.

Fortunately, the University of Chicago had astronomers who were looking for another telescope to use in addition to their university’s refracting telescope at Yerkes Observatory. So, the presidents of the two universities made a deal: The University of Texas would build the new observatory, and the University of Chicago would provide experts to operate it.

McDonald’s first major telescope — later named the Otto Struve Telescope after the observatory’s first director — was finished in 1939 and is still in use today.

McDonald Observatory Otto Struve telescope
Altitude 2,026 m (6,647 ft)

Its main mirror is 82 inches (2.08 meters) across. One of the main purposes of the Struve Telescope was to analyze the exact colors of light coming from stars and other celestial bodies, to determine their chemical composition, temperature, and other properties. To do this, the telescope was designed to send light through a series of mirrors into a spectrograph — an instrument that separates light into its component colors — in another room. This required the telescope to be mounted on a strange-looking arrangement of axes and counterweights, designed and built by the Warner & Swasey company. “With its heavy steel mounting and black, half-open framework, the Struve is not just a scientific instrument, but it is a work of art,” the Observatory’s website says.

The Struve Telescope helped astronomers gather the first evidence of an atmosphere on Saturn’s moon Titan. Gerard Kuiper, assisted by Struve himself, found the clues while examining our solar system’s largest moons in 1944. Kuiper published his spectroscopic study in The Astrophysical Journal.

In 1956, a reflecting telescope with a 36-inch (0.9 m) mirror was added to the McDonald site at the request of the University of Chicago.

McDonald Observatory .9 meter telescope, Altitude 2,026 m (6,647 ft)

Housed in a dome made from locally quarried rock and leftover metal from the Struve Telescope dome, this instrument was designed primarily to measure changes in the brightness of stars. It is now obsolete for professional research, but is regularly used for special public-viewing nights.

The Harlan J. Smith Telescope, with a main mirror 107 inches (2.7 m) across, was built by NASA to examine other planets in preparation for spacecraft missions. It was the world’s third-largest telescope when it saw first light in 1968.

U Texas at Austin McDonald Observatory Harlan J Smith 2.7-meter Telescope , Altitude 2,026 m (6,647 ft)

From 1969 to 1985, the Smith telescope was also used to aim laser light at special reflecting mirrors left on the moon by Apollo astronauts. Measuring the time required for the reflected light to return to Earth enables astronomers to measure the moon’s distance to an accuracy of 1.2 inches (3 centimeters). These measurements, in turn, contribute to our understanding of Earth’s rotation rate, the moon’s composition, long-term changes in the moon’s orbit, and the behavior of gravity itself, including small effects predicted by Albert Einstein’s General Theory of Relativity.

When the Smith telescope was being built, a circular hole was cut in the center of its main quartz mirror to allow light to pass to instruments at the back of the telescope. The cutout quartz disk was made into a new mirror 30 inches (0.8 m) across for another telescope. This instrument, built nearby in 1970 and known simply as the 0.8 meter telescope, has the advantage of an unusually wide field of view.

McDonald’s biggest telescope

Today, the giant at McDonald is the Hobby-Eberly Telescope (HET), on neighboring Mount Fowlkes, almost a mile (1.3 km) from the cluster of original domes on Mount Locke.

U Texas Austin McDonald Observatory Hobby-Eberly Telescope, Altitude 2,026 m (6,647 ft)

The HET is a joint project of the University of Texas at Austin, Pennsylvania State University, and two German universities: Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

Dedicated in 1997, the HET makes a striking technological contrast with the classic Struve instrument. HET’s main mirror is not one piece of glass or quartz, but an array of 91 individually controlled hexagonal segments making a honeycomb-like reflecting area that’s 36 feet (11 m) wide. A mushroom-shaped tower next to the main dome contains lasers that are aimed at the mirror segments to test and adjust their alignment.

Another remarkable feature of the HET is that the telescope can rotate to point toward any compass direction, but it cannot tilt up or down to point at different heights in the sky. Instead, the main mirror is supported at a fixed angle pointing 55 degrees above the horizon. A precisely controlled tracking support moves light-gathering instruments to various locations above the main mirror, which has the effect of aiming at slightly different parts of the sky. This unique, simplified design allowed the HET to be built for a fraction of the cost of a conventional telescope of its size, while still allowing access to 70% of the sky visible from its location.

The HET was designed primarily for spectroscopy, which is a key method in current research areas such as measuring motions of space objects, determining distances to galaxies and discovering the history of the universe since the Big Bang.

Habitable planets and dark energy

In 2017, the HET was rededicated after a $40 million upgrade. The tracking system was replaced with a new unit that uses more of the main mirror and has a wider field of view. And, new sensing instruments were created.

One of the new instruments is the Habitable Zone Planet Finder (HPF), built in conjunction with the National Institute of Standards and Technology.

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Habitable Zone Planet Finder

The HPF is optimized to study infrared light from nearby, cool red dwarf stars, according to an announcement from the observatory. These stars have long lifetimes and could provide steady energy for planets orbiting close to them. The HPF allows precise measurements of a star’s radial velocity, measured by the subtle change in the color of the star’s spectra as it is tugged by an orbiting planet, which is critical information in the discovery and confirmation of new planets.

Advancing another frontier is the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX).Billed as the first major experiment searching for the mysterious force pushing the universe’s expansion, the HETDEX “will tell us what makes up almost three-quarters of all the matter and energy in the universe. It will tell us if the laws of gravity are correct, and reveal new details about the Big Bang in which the universe was born,” the HETDEX project website says.

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VIRUS-P undergoes testing at the Harlan J. Smith Telescope at McDonald Observatory. HETDEX will consist of 145 identical VIRUS units attached to the Hobby-Eberly Telescope. [Martin Harris/McDonald Observatory]

A key piece of technology for the dark-energy search is the Visible Integral-Field Replicable Unit Spectrographs, or VIRUS, a set of 156 spectrographs mounted alongside the telescope and receiving light via 35,000 optical fibers coming from the telescope. With this package of identical instruments sharing the telescope, the HET can observe several hundred galaxies at once, measuring how their light is affected by their own motions and the expansion of the universe.

The HETDEX will spend about three years observing a minimum of 1 million galaxies to produce a large map showing the universe’s expansion rate during different time periods. Any changes in how quickly the universe grows could yield differences in dark energy.

Keeping the skies dark

In 2019, the McDonald Observatory received a grant from the Apache Corp., an oil and gas exploration and production company, to promote awareness of the value of dark skies as a natural resource and as an aid to astronomical research. The gift will fund education programs, outreach events, and a new exhibit at the observatory’s visitors center. According to the observatory’s announcement, Apache has served as a model for other businesses in west Texas by adjusting and shielding the lights at its drilling sites and related facilities.

See the full article here .

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From The New York Times: “Leonids Meteor Shower Will Peak in Night Skies”

New York Times

From The New York Times

Nov. 16, 2019
Nicholas St. Fleur

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A meteor from the Leonids streaking through the sky, seen between the arms of a cactus in Tucson, Ariz., in 2001.Credit…James S. Wood/Arizona Daily Star, via Associated Press

All year long as Earth revolves around the sun, it passes through streams of cosmic debris. The resulting meteor showers can light up night skies from dusk to dawn, and if you’re lucky you might be able to catch a glimpse.

The next shower you might be able to see is the Leonids. Active between Nov. 6 and Nov. 30, the show peaks around Sunday night into Monday morning, or Nov. 17-18.

The Leonids are one of the most dazzling meteor showers and every few decades it produces a meteor storm where more than 1,000 meteors can been seen an hour. Cross your fingers for some good luck — the last time the Leonids were that strong was in 2002. Its parent comet is called Comet-Temple/Tuttle and it orbits the sun every 33 years.

Where meteor showers come from

If you spot a meteor shower, what you’re usually seeing is an icy comet’s leftovers that crash into Earth’s atmosphere. Comets are sort of like dirty snowballs: As they travel through the solar system, they leave behind a dusty trail of rocks and ice that lingers in space long after they leave. When Earth passes through these cascades of comet waste, the bits of debris — which can be as small as grains of sand — pierce the sky at such speeds that they burst, creating a celestial fireworks display. A general rule of thumb with meteor showers: You are never watching the Earth cross into remnants from a comet’s most recent orbit. Instead, the burning bits come from the previous passes. For example, during the Perseid meteor shower you are seeing meteors ejected from when its parent comet, Comet Swift-Tuttle, visited in 1862 or earlier, not from its most recent pass in 1992.

What on Earth Is Going On?

That’s because it takes time for debris from a comet’s orbit to drift into a position where it intersects with Earth’s orbit, according to Bill Cooke, an astronomer with NASA’s Meteoroid Environment Office.

How to watch

The best way to see a meteor shower is to get to a location that has a clear view of the entire night sky. Ideally, that would be somewhere with dark skies, away from city lights and traffic. To maximize your chances of catching the show, look for a spot that offers a wide, unobstructed view.

Bits and pieces of meteor showers are visible for a certain period of time, but they really peak visibly from dusk to dawn on a given few days. Those days are when Earth’s orbit crosses through the thickest part of the cosmic stream. Meteor showers can vary in their peak times, with some reaching their maximums for only a few hours and others for several nights. The showers tend to be most visible after midnight and before dawn.

It is best to use your naked eye to spot a meteor shower. Binoculars or telescopes tend to limit your field of view. You might need to spend about half an hour in the dark to let your eyes get used to the reduced light. Stargazers should be warned that moonlight and the weather can obscure the shows. But if that happens, there are usually meteor livestreams like the ones hosted by NASA and by Slooh.

See the full article here .

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From AAS NOVA: “Hunting for a Dark Matter Wake”

AASNOVA

From AAS NOVA

13 November 2019
Susanna Kohler

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The Large Magellanic Cloud is the Milky Way’s most massive satellite. What evidence has this galaxy left behind as it plows through the Milky Way’s dark matter halo? [ESO/VMC Survey]

As the Large Magellanic Cloud plows through the Milky Way’s dark matter halo, it may leave telltale signs of its passage. A recent study explores whether we’ll be able to spot this evidence — and what it can tell us about our galaxy and the nature of dark matter.

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The Large and Small Magellanic clouds, as observed from Earth. [ESO/S. Brunier]

The Milky Way’s Large Companion

The Milky Way is far from lonely. Dozens of smaller satellite-galaxy companions orbit around our galaxy, charging through its larger dark matter halo. The most massive of these is the Large Magellanic Cloud (LMC), a galaxy of perhaps 10 or 100 billion solar masses that’s about 14,000 light-years across.

Studies suggest that the LMC is on its first pass around the Milky Way, traveling on a highly eccentric orbit; it likely only first got close to our galaxy (within about 200 kpc, or 650,000 light-years) about two billion years ago.

There are still many uncertainties about this satellite and its travels, however. How massive, exactly, is the LMC? What does its past orbit look like? And how has it interacted with our galaxy’s dark matter halo, which it’s passing through?

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Density perturbations caused by the LMC’s motion for one of the authors’ Milky Way models. The Milky Way’s disk is in the x–y plane; the black curve traces the LMC’s past orbital path and the red star indicates its current position. Three primary overdense/underdense features are visible as signatures of the LMC’s wake. [Adapted from Garavito-Camargo et al. 2019]

A Telltale Trail

A team of scientists led by Nicolas Garavito-Camargo (Steward Observatory, University of Arizona) thinks there may be evidence we can use to answer these questions.

Like a boat, the LMC should generate a wake as it plows through the Milky Way’s dark matter halo. This wake is caused by gravitational interactions between the satellite and dark matter particles that drag at the LMC, causing the galaxy to lose angular momentum as it orbits.

The perturbations that make up this wake — overdensities and underdensities in the dark matter and stellar distribution in the halo — are signatures that we can predict and hunt for. In a new study, Garavito-Camargo and collaborators use high-resolution N-body simulations to explore the motion of the LMC through the Milky Way’s halo and examine the perturbations caused by this charging satellite.

Spotting the Evidence of Passage

The authors find that the LMC’s motion produces a pronounced dark matter wake that can be decomposed into three parts:

Transient response, a trailing wake of overdensity behind the satellite that traces its orbital history
Global underdensity, a large underdense region south of the transient response
Collective response, an extended overdensity leading the LMC in the galactic north

These features in the dark-matter distribution are echoed in how stars are distributed in the regions, and the stars should also show distinctive kinematic signatures.

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Observing strategies for identifying the LMC’s wake using stellar densities. To avoid confusion with the Sagittarius stellar stream (the prominent yellow, orange, and red points indicated), the authors identify several regions for observation (colored rectangles) away from the stream where the wake should be detectable. [Garavito-Camargo et al. 2019]

Garavito-Camargo and collaborators outline an observing strategy to spot the predicted overdensities and underdensities of the wake, and they show that the detection of just 20–30 stars in specific regions could provide useful confirmation of their models. The measurements needed should be achievable with current and upcoming stellar surveys.

What can we learn from these observations? The detection of the LMC’s wake will track its past orbit, which will provide an indirect measure of our own galaxy’s mass. The specifics of the LMC’s motion will also better constrain the satellite’s mass, as well as provide clues as to the nature of the dark-matter particles that drag on it.

Citation

“Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud,” Nicolas Garavito-Camargo et al 2019 ApJ 884 51.

https://iopscience.iop.org/article/10.3847/1538-4357/ab32eb

See the full article here .


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AAS Mission and Vision Statement

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

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From NASA JPL-Caltech: “NASA Finds Neptune Moons Locked in ‘Dance of Avoidance'”

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From NASA JPL-Caltech

November 14, 2019
Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-6215
gretchen.p.mccartney@jpl.nasa.gov

Alana Johnson
NASA Headquarters, Washington
202-358-1501
alana.r.johnson@nasa.gov

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Neptune Moon Dance: This animation illustrates how the odd orbits of Neptune’s inner moons Naiad and Thalassa enable them to avoid each other as they race around the planet.

Even by the wild standards of the outer solar system, the strange orbits that carry Neptune’s two innermost moons are unprecedented, according to newly published research [Icarus].

Orbital dynamics experts are calling it a “dance of avoidance” performed by the tiny moons Naiad and Thalassa. The two are true partners, orbiting only about 1,150 miles (1,850 kilometers) apart. But they never get that close to each other; Naiad’s orbit is tilted and perfectly timed. Every time it passes the slower-moving Thalassa, the two are about 2,200 miles (3,540 kilometers) apart.


An observer sitting on Thalassa would see Naiad in an orbit that varies wildly in a zigzag pattern, passing by twice from above and then twice from below. Credit: NASA/JPL-Caltech

In this perpetual choreography, Naiad swirls around the ice giant every seven hours, while Thalassa, on the outside track, takes seven and a half hours. An observer sitting on Thalassa would see Naiad in an orbit that varies wildly in a zigzag pattern, passing by twice from above and then twice from below. This up, up, down, down pattern repeats every time Naiad gains four laps on Thalassa.

Although the dance may appear odd, it keeps the orbits stable, researchers said.

“We refer to this repeating pattern as a resonance,” said Marina Brozovi?, an expert in solar system dynamics at NASA’s Jet Propulsion Laboratory in Pasadena, California, and the lead author of the new paper, which was published Nov. 13 in Icarus. “There are many different types of ‘dances’ that planets, moons and asteroids can follow, but this one has never been seen before.”

Far from the pull of the Sun, the giant planets of the outer solar system are the dominant sources of gravity, and collectively, they boast dozens upon dozens of moons. Some of those moons formed alongside their planets and never went anywhere; others were captured later, then locked into orbits dictated by their planets. Some orbit in the opposite direction their planets rotate; others swap orbits with each other as if to avoid collision.

Neptune has 14 confirmed moons. Neso, the farthest-flung of them, orbits in a wildly elliptical loop that carries it nearly 46 million miles (74 million kilometers) away from the planet and takes 27 years to complete.

Naiad and Thalassa are small and shaped like Tic Tacs, spanning only about 60 miles (100 kilometers) in length. They are two of Neptune’s seven inner moons, part of a closely packed system that is interwoven with faint rings.

So how did they end up together – but apart? It’s thought that the original satellite system was disrupted when Neptune captured its giant moon, Triton, and that these inner moons and rings formed from the leftover debris.

“We suspect that Naiad was kicked into its tilted orbit by an earlier interaction with one of Neptune’s other inner moons,” Brozovi? said. “Only later, after its orbital tilt was established, could Naiad settle into this unusual resonance with Thalassa.”

Brozovi? and her colleagues discovered the unusual orbital pattern using analysis of observations by NASA’s Hubble Space Telescope. The work also provides the first hint about the internal composition of Neptune’s inner moons. Researchers used the observations to compute their mass and, thus, their densities – which were close to that of water ice.

“We are always excited to find these co-dependencies between moons,” said Mark Showalter, a planetary astronomer at the SETI Institute in Mountain View, California, and a co-author of the new paper. “Naiad and Thalassa have probably been locked together in this configuration for a very long time, because it makes their orbits more stable. They maintain the peace by never getting too close.”

More information about Neptune’s moons can be found here:

https://solarsystem.nasa.gov/moons/neptune-moons/in-depth/

See the full article here .


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NASA JPL Campus

Jet Propulsion Laboratory (JPL)) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge, on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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From Science Alert: “Japan’s Space Probe Is Returning to Earth With an Actual Piece of Asteroid”

ScienceAlert

From Science Alert

13 NOV 2019
KYOKO HASEGAWA, AFP

KYOKO HASEGAWA, AFP
13 NOV 2019

Japan’s Hayabusa-2 probe will leave its orbit around a distant asteroid and head for Earth on Wednesday after an unprecedented mission, carrying samples that could shed light on the origins of the Solar System.

JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

The long voyage home would begin at 10:05 am (0105 GMT), with the probe expected to drop off its precious samples some time late 2020, the Japan Aerospace Exploration Agency (JAXA) said.

“We expect Hayabusa-2 will provide new scientific knowledge to us,” project manager Yuichi Tsuda told reporters.

The probe will bring back to Earth “carbon and organic matter” that will provide data as to “how the matter is scattered around the Solar System, why it exists on the asteroid and how it is related to Earth,” added Tsuda.

The mission took the fridge-sized probe some 300 million kilometres (186 million miles) from Earth, where it explored the asteroid Ryugu, whose name means “Dragon Palace” in Japanese – a reference to a castle at the bottom of the ocean in an ancient fable.

In April, Hayabusa-2 fired an “impactor” into the asteroid to stir up materials that had not previously been exposed to the atmosphere.

It then made a “perfect” touchdown on the surface of the asteroid to collect the samples that scientists hope will provide clues into what the Solar System was like at its birth some 4.6 billion years ago.

“I’m feeling half-sad, half-determined to do our best to get the probe home,” said Tsuda.

“Ryugu has been at the heart of our everyday life for the past year and a half,” he added.
‘New destination’

Hayabusa-2 will receive its orders to head for home on Wednesday, break free of the asteroid’s gravity on November 18 and fire its main engines early next month en route to Earth, JAXA said.

Tsuda said the six-year mission, which had a price tag of around 30 billion yen (US$278 million), had exceeded expectations but admitted his team had to overcome a host of technical problems.

It took the probe three-and-a-half years to get to the asteroid but the return journey should be significantly shorter because Earth and Ryugu will be much closer due to their current positions.

Hayabusa-2 is expected to drop the samples off in the South Australian desert, but JAXA is negotiating with the Australian government about how to arrange it, Tsuda said.

The probe is the successor to JAXA’s first asteroid explorer “Hayabusa”, which means falcon in Japanese.

The earlier probe returned with dust samples from a smaller, potato-shaped asteroid in 2010 despite various setbacks during its epic seven-year odyssey, and was hailed as a scientific triumph.

The first generation probe re-entered Earth’s atmosphere and burned out.

Under the current plan, Hayabusa-2 will boldly continue its journey in space after dropping off its capsule to Earth, and might “carry out another asteroid exploration,” JAXA spokesman Keiichi Murakami earlier told AFP.

“The team has just started to study what can be done (after dropping off the capsule),” but there is no concrete plans about a new destination, Tsuda said.

See the full article here .


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From Science Alert: “TESS Data May Already Hold a Clue to The Mysterious Planet Nine”

ScienceAlert

From Science Alert

14 NOV 2019
MICHELLE STARR

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Artist’s impression of Planet Nine. (nagualdesign/Tom Ruen/ESO/Wikimedia Commons)

There seems to be something large lurking in the far reaches of the Solar System, messing with the orbits of some of the Kuper Belt rocks out past Neptune. Some astronomers believe it’s a planet, about five times the mass of Earth. They call it Planet Nine.

But finding this potential lurker is not so simple. From here, it would appear extremely small and faint, and we don’t even know where in the sky we should be looking. Astronomers are searching (and finding some other really neat stuff in the process), but it’s slow and painstaking work.

According to a new paper [ Research Notes of the AAS], though, there could be another way: NASA’s Transiting Exoplanet Survey Satellite (TESS). And it’s possible the planet has already been observed, and is hidden away in the TESS data.

NASA/MIT TESS replaced Kepler in search for exoplanets

You may be thinking “duh, it’s a planet-hunting telescope”, but looking for planets that are very far away, and looking for planets that are relatively close are two different things.

TESS looks for exoplanets using the transit method.

Planet transit. NASA/Ames

It stares at sections of the sky for long durations, looking for faint, regular dips in starlight caused by planets orbiting between us and the star (what is known as a transit).

In the case of Planet Nine, detecting its transit would be impossible, because it wouldn’t pass between TESS and the Sun.

And a single exposure wouldn’t reveal an object as faint as Planet Nine. However, the way TESS stares at sections of the sky for long durations could be combined with an astronomy technique called digital tracking.

In order to reveal transit dips, TESS takes a lot of photos of one field of view. If you stack these images, faint objects can become much brighter, revealing objects that would otherwise be hidden.

Because Planet Nine is a moving object, just stacking the images wouldn’t necessarily reveal the planet. This is where you have to do a bit of guesswork to calculate an estimated orbit of the object, and sort-of shift the exposures to centre on your estimated position – and stack the images then.

“To discover new objects, with unknown trajectories,” the researchers wrote in their paper, “we can try all possible orbits!”

Just feed your images and orbit and parallax corrections (TESS has a highly elliptical orbit around Earth, so the line-of-sight gets displaced as it moves) into a software program and wait for the results.

It sounds like a scattershot approach, but it might actually work. For example, digital tracking with the Hubble Space Telescope has been used to discover several objects out past Neptune.

The next question is whether TESS is powerful enough to detect the planet. But there’s a way to test this too.

Models have suggested Planet Nine has an apparent magnitude – that is, brightness as seen from Earth – between 19 and 24. There are some known orbiting trans-Neptunian objects that have apparent magnitudes within this range – namely, Sedna (20.5 to 20.8), 2015 BP519 (21.5) and 2015 BM518 (21.6).

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(Holman et al., Research Notes of the AAS, 2019)

So, the team used digital tracking to resolve each of these three objects… and all three showed up, clear as a really fuzzy low-resolution crystal. But still identifiable. You can see them in the image above: From left, that’s Sedna, 2015 BP519 and 2015 BP518. The images have been shown in negative to make the objects easier to see.

Hypothetically, TESS should be able to see any object at around those magnitudes. Which means, the researchers said, that it should also be able to see Planet Nine. It may even already be there in the data – we just haven’t found it yet.

You’d have to test for all possible orbits, which could require a lot of computing. So… Anyone got a spare supercomputer?

See the full article here .


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From ALMA: “Two Cosmic Peacocks Show Violent History of the Magellanic Clouds”

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

From ALMA

14 November, 2019

Nicolás Lira
Education and Public Outreach Coordinator
Joint ALMA Observatory, Santiago – Chile
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1
ALMA images of two molecular clouds N159E-Papillon Nebula (left) and N159W South (right). Red and green show the distribution of molecular gas in different velocities seen in the emission from 13CO. Blue region in N159E-Papillon Nebula shows the ionized hydrogen gas observed with the Hubble Space Telescope. Blue part in N159W South shows the emission from dust particles obtained with ALMA. Credit: ALMA (ESO/NAOJ/NRAO)/Fukui et al./Tokuda et al./NASA-ESA Hubble Space Telescope

NASA/ESA Hubble Telescope

3
Artist’s impression of the formation process of peacock-shaped clouds. After collision of two clouds (left), complicated filamentary structures with a pivot in the bottom are formed in the boundary region (center), and a massive star is formed in the dense part with ionized region shown in blue (right). Credit: NAOJ

Two peacock-shaped gas clouds were revealed in the Large Magellanic Cloud (LMC) by observations with the Atacama Large Millimeter/submillimeter Array (ALMA). A team of astronomers found several massive baby stars in the complex filamentary clouds, which agrees well with computer simulations of giant collisions of gas clouds. The researchers interpret this to mean that the filaments and young stars are telltale evidence of violent interactions between the LMC and the Small Magellanic Cloud (SMC) 200 million years ago.

Large Magellanic Cloud. Adrian Pingstone December 2003

smc

Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

Astronomers know that stars are formed in collapsing clouds in space. However, the formation processes of giant stars, 10 times or more massive than the Sun, are not well understood because it is difficult to pack such a large amount of material into a small region. Some researchers suggest that interactions between galaxies provide a perfect environment for massive star formation. Due to the colossal gravity, clouds in the galaxies are stirred, stretched, and often collide with each other. A huge amount of gas is compressed in an unusually small area, which could form the seeds of massive stars.

A research team used ALMA to study the structure of dense gas in N159, a bustling star formation region in the LMC. Thanks to ALMA’s high resolution, the team obtained a very detailed map of the clouds in two sub-regions, N159E-Papillon Nebula and N159W South.

Interestingly, the cloud structures in the two regions look very similar: fan-shaped filaments of gas extending to the north with the pivots in the southernmost points. The ALMA observations also found several massive baby stars in the filaments in the two regions.

“It is unnatural that in two regions separated by 150 light-years, clouds with such similar shapes were formed and that the ages of the baby stars are similar in two regions separated 150 light years,” says Kazuki Tokuda, a researcher at Osaka Prefecture University and the National Astronomical Observatory of Japan. “There must be a common cause of these features. Interaction between the LMC and SMC is a good candidate.”

Magellanic Bridge ESA Gaia satellite. Image credit V. Belokurov D. Erkal A. Mellinger.

In 2017, Yasuo Fukui, a professor at Nagoya University and his team revealed the motion of hydrogen gas in the LMC and found that a gaseous component right next to N159 has a different velocity than the rest of the clouds. They suggested a hypothesis that the starburst is caused by a massive flow of gas from the SMC to the LMC, and that this flow originated from a close encounter between the two galaxies 200 million years ago.

The pair of the peacock-shaped clouds in the two regions revealed by ALMA fits nicely with this hypothesis. Computer simulations show that many filamentary structures are formed in a short time scale after a collision of two clouds, which also backs this idea.

“For the first time, we uncovered the link between massive star formation and galaxy interactions in very sharp detail,” says Fukui, the lead author of one of the research papers. “This is an important step in understanding the formation process of massive star clusters in which galaxy interactions have a big impact.”

Additional Information

This research was presented in the following two papers on 14 November 2019 in The Astrophysical Journal.

Fukui et al. “An ALMA view of molecular filaments in the Large Magellanic Cloud I: The formation of high-mass stars and pillars in the N159E-Papillon Nebula triggered by a cloud-cloud collision”
Tokuda et al. “An ALMA view of molecular filaments in the Large Magellanic Cloud II: An early stage of high-mass star formation embedded at colliding clouds in N159W-South”

Research team members are:

Yasuo Fukui (Nagoya University), Kazuki Tokuda (Osaka Prefecture University/National Astronomical Observatory of Japan), Kazuya Saigo (National Astronomical Observatory of Japan), Ryohei Harada (Osaka Prefecture University), Kengo Tachihara (Nagoya University), Kisetsu Tsuge (Nagoya University), Tsuyoshi Inoue (Nagoya University), Kazufumi Torii (National Astronomical Observatory of Japan), Atsushi Nishimura (Nagoya University), Sarolta Zahorecz (Osaka Prefecture University/National Astronomical Observatory of Japan), Omnarayani Nayak (Space Telescope Science Institute), Margaret Meixner (Johns Hopkins University/Space Telescope Science Institute), Tetsuhiro Minamidani (National Astronomical Observatory of Japan), Akiko Kawamura (National Astronomical Observatory of Japan), Norikazu Mizuno (National Astronomical Observatory of Japan/Joint ALMA Observatory), Remy Indebetouw (University of Virginia/National Radio Astronomy Observatory), Marta Sewiło (NASA Goddard Space Flight Center/University of Maryland), Suzanne Madden (Université Paris-Saclay), Maud Galametz(Université Paris-Saclay), Vianney Lebouteiller (Université Paris-Saclay), C.-H. Rosie Chen (Max Planck Institute for Radio Astronomy), and Toshikazu Onishi (Osaka Prefecture University)

This research was supported by JSPS KAKENHI (No. 22244014, 23403001, 26247026, 18K13582, 18K13580,18H05440), NAOJ ALMA Scientific Research Grant (No. 2016-03B), and NASA (No.80GSFC17M0002).

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The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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