From “McDonald Observatory: Searching for Dark Energy”

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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.

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.

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 “Einstein’s Quest to ‘Know God’s Thoughts’ Could Take Millennia” Don Lincoln of FNAL

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(Image: © Shutterstock)

In 1925, Einstein went on a walk with a young student named Esther Salaman. As they wandered, he shared his core guiding intellectual principle: “I want to know how God created this world. I’m not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; the rest are just details.”

The phrase “God’s thoughts” is a delightfully apt metaphor for the ultimate goal of modern physics, which is to develop a perfect understanding of the laws of nature — what physicists call “a theory of everything,” or TOE. Ideally, a TOE would answer all questions, leaving nothing unanswered. Why is the sky blue? Covered. Why does gravity exist? That’s covered, too. Stated in a more scientific way, a TOE would ideally explain all phenomena with a single theory, a single building block and a single force. In my opinion, finding a TOE could take hundreds, or even thousands, of years. To understand why, let’s take stock.

We know of two theories that, when taken together, give a good description of the world around us, but both are light-years from being a TOE.

The first is Einstein’s theory of general relativity, which describes gravity and the behavior of stars, galaxies and the universe on the largest scales. Einstein described gravity as the literal bending of space and time. This idea has been validated many times, most notably with the discovery of gravitational waves in 2016.

The second theory is called the Standard Model, which describes the subatomic world. It is in this domain that scientists have made the most obvious progress toward a theory of everything.

Standard Model of Particle Physics

If we look at the world around us — the world of stars and galaxies, poodles and pizza, we can ask why things have the properties they do. We know everything is made up of atoms, and those atoms are made up of protons, neutrons and electrons.

And, in the 1960s, researchers discovered that the protons and neutrons were made of even smaller particles called quarks and the electron was a member of the class of particles called leptons.

Finding the smallest building blocks is only the first step in devising a theory of everything. The next step is understanding the forces that govern how the building blocks interact. Scientists know of four fundamental forces, three of which — electromagnetism, and the strong and weak nuclear forces — are understood at the subatomic level. Electromagnetism holds atoms together and is responsible for chemistry. The strong force holds together the nucleus of atoms and keeps quarks inside protons and neutrons. The weak force is responsible for some types of nuclear decay.

Each of the known subatomic forces has an associated particle or particles that carry that force: The gluon carries the strong force, the photon governs electromagnetism, and the W and Z bosons control the weak force. There is also a ghostly energy field, called the Higgs field, that permeates the universe and gives mass to quarks, leptons and some of the force-carrying particles. Taken together, these building blocks and forces make up the Standard Model.

A theory of everything will explain all known phenomena. We aren’t there yet, but we have unified the behavior of the quantum world in the standard model (yellow) and we understand gravity (pink). In the future, we imagine a series of additional unifications (green). However, the problem is that there are phenomena we don’t understand (blue) that need to fit in somewhere. And we are not certain that we won’t find other phenomena as we go to higher energy (red circles). (Image: © Don Lincoln)

Using quarks and leptons and the known force-carrying particles, one can build atoms, molecules, people, planets and, indeed, all of the known matter of the universe. This is undoubtedly a tremendous achievement and a good approximation of a theory of everything.

And yet it really isn’t. The goal is to find a single building block and a single force that could explain the matter and motion of the universe. The Standard Model has 12 particles (six quarks and six leptons) and four forces (electromagnetism, gravity, and the strong and weak nuclear forces). Furthermore, there is no known quantum theory of gravity (meaning our current definition covers just gravity involving things larger than, for example, common dust), so gravity isn’t even part of the Standard Model at all. So, physicists continue to look for an even more fundamental and underlying theory. To do that they need to reduce the number of both building blocks and forces.

Finding a smaller building block will be difficult, because that requires a more powerful particle accelerator than humans have ever built. The time horizon for a new accelerator facility coming on line is several decades and that facility will provide only a relatively modest incremental improvement over existing capabilities. So, scientists must instead speculate on what a smaller building block might look like. A popular idea is called superstring theory, which postulates that the smallest building block isn’t a particle, but rather a small and vibrating “string.” In the same way a cello string can play more than one note, the different patterns of vibrations are the different quarks and leptons. In this way, a single type of string could be the ultimate building block.

The problem is that there is no empirical evidence that superstrings actually exist. Further, the expected energy required to see them is called the Planck energy, which is a quadrillion (10 raised to the 15th power) times higher than we can currently generate. The very large Planck energy is intimately connected to what’s known as the Planck length, an unfathomably tiny length beyond which quantum effects become so large that it is literally impossible to measure anything smaller. Meanwhile, go smaller than the Planck length (or bigger than the Planck energy), and the quantum effects of gravity between photons, or light particles, become important and relativity no longer works. That makes it likely this is the scale at which quantum gravity will be understood. This is, of course, all very speculative, but it reflects our current best prediction. And, if true, superstrings will have to remain speculative for the foreseeable future.

The plethora of forces is also a problem. Scientists hope to “unify” the forces, showing that they are just different manifestations of a single force. (Sir Isaac Newton did just that when he showed the force that made things fall on Earth and the force that governed the motion of the heavens were one and the same; James Clerk Maxwell showed that electricity and magnetism were really different behaviors of a unified force called electromagnetism.)

In the 1960s, scientists were able to show that the weak nuclear force and electromagnetism were actually two different facets of a combined force called the electroweak force. Now, researchers hope that the electroweak force and the strong force can be unified into what is called a grand unified force. Then, they hope that the grand unified force can be unified with gravity to make a theory of everything.

Historically, scientists have shown how seemingly unrelated phenomena originate from a single underlying force. We imagine that this process will continue, resulting in a theory of everything. (Image: © Don Lincoln)

However, physicists suspect this final unification would also take place at the Planck energy, again because this is the energy and size at which quantum effects can no longer be ignored in relativity theory. And, as we’ve seen, this is a much higher energy than we can hope to achieve inside a particle accelerator any time soon. To give a sense of the chasm between current theories and a theory of everything, if we represented the energies of particles we can detect as the width of a cell membrane, the Planck energy is the size of Earth. While it is conceivable that someone with a thorough understanding of cell membranes might predict other structures within a cell — things like DNA and mitochondria — it is inconceivable that they could accurately predict the Earth. How likely is it that they could predict volcanoes, oceans or Earth’s magnetic field?

The simple fact is that with such a large gap between currently achievable energy in particle accelerators and the Planck energy, correctly devising a theory of everything seems improbable.

That doesn’t mean physicists should all retire and take up landscape painting — there is still meaningful work to be done. We still need to understand unexplained phenomena such as dark matter and dark energy, which make up 95% of the known universe, and use that understanding to create a newer, more comprehensive theory of physics. This newer theory will not be a TOE, but will be incrementally better than the current theoretical framework. We will have to repeat that process over and over again.

Disappointed? So am I. After all, I’ve devoted my life to trying to uncover some of the secrets of the cosmos, but perhaps some perspective is in order. The first unification of forces was accomplished in the 1670s with Newton’s theory of universal gravity. The second was in the 1870s with Maxwell’s theory of electromagnetism. The electroweak unification was relatively recent, only half a century ago.

Given that 350 years has elapsed since our first big successful step in this journey, perhaps it’s less surprising that the path ahead of us is longer still. The notion that a genius will have an insight that results in a fully developed theory of everything in the next few years is a myth. We’re in for a long slog — and even the grandchildren of today’s scientists won’t see the end of it.

But what a journey it will be.

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From “Faster-Than-Light Particles Emit Superbright Gamma Rays that Circle Pulsars”

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Yasemin Saplakoglu

The Vela pulsar that lives 1,000 light years from our planet. (Image: © NASA/CXC/Univ of Toronto/M.Durant et al)

Charged particles travel faster than light through the quantum vacuum of space that surrounds pulsars. As these electrons and protons fly by pulsars, they create the ultrabright gamma-ray flashes emitted by the rapidly twirling neutron stars, new research reveals.

These gamma-rays, called Cherenkov emissions, are also found in powerful particle accelerators on Earth, such as the Large Hadron Collider near Geneva, Switzerland. The rays are also the source of the bluish-white glow in the waters of a nuclear reactor.


CERN map


CERN LHC particles

Daya Bay, nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China

But until now, no one thought that pulsar emissions consisted of Cherenkov radiation.

That’s in part because of Albert Einstein’s famous theory of relativity, which holds that nothing can travel faster than light in a vacuum. Because of those propositions, scientists previously thought that Cherenkov emissions couldn’t happen in the quantum vacuum of space surrounding pulsars. That area is mostly devoid of matter but home to ghostly quantum particles that flicker in and out of existence.

So, does this new research mean Einstein’s landmark theory was just violated? Not at all, said study co-author Dino Jaroszynski, a professor of physics at the University of Strathclyde in Scotland.

Pulsars create crushingly strong electromagnetic fields in the quantum vacuum surrounding the stars. These fields warp, or polarize, the vacuum, essentially creating speed bumps that slow down light particles, Jaroszynski told Live Science. Meanwhile, charged particles such as protons and electrons zoom through these fields, racing past light.

As charged particles fly through this field, they displace electrons along their path and emit radiation, which gathers into an electromagnetic wave. This wave, like an optical version of a sonic boom, is what we see as the gamma-ray flash, according to a statement.

The team still doesn’t know exactly how bright these gamma-ray flashes are, Jaroszynski said.

“What we do know is that, under the right conditions, vacuum Cherenkov radiation outshines synchrotron radiation,” he added, referring to another type of radiation that is emitted from pulsars by charged particles moving along a curved path.

But the new findings could have implications beyond pulsars, the researchers said.

“This is a very exciting new prediction because it could provide answers to basic questions such as what is the origin of the gamma-ray glow at the centre of galaxies?” Jaroszynski said in the statement. “It provides a new way of testing some of the most fundamental theories of science by pushing them to their limits.”

The researchers reported their findings April 25 in the journal Physical Review Letters.

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Women in STEM – Dame Susan Jocelyn Bell Burnell

Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

Dame Susan Jocelyn Bell Burnell 2009

Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www.


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From “Dawn Mission: Shedding Light on Asteroids”

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May 1, 2018
Nola Taylor Redd

NASA Dawn Spacescraft

When NASA’s Dawn mission launched in 2007, it was on its way to breaking several records. When it entered orbit around the Vesta, it became the first to orbit a main-belt asteroid. After leaving Vesta, it journeyed on to Ceres, becoming the first spacecraft to visit and then orbit a dwarf planet and the first spacecraft to orbit two extraterrestrial targets.

The journey hasn’t been smooth. Along the way, the spacecraft lost threeof its four reaction wheels that keep it oriented. It successfully concluded its primary mission to study both targets in 2016. Once it runs out of fuel near the end of 2018, it will continue to orbit Ceres for another 50 years.

“To me, the real story here is how cool it is that we’re exploring what, in my view, are some of the last uncharted worlds in the inner solar system,” chief engineer and Dawn mission director Marc Rayman told “Most people think of asteroids as chips of rock, but these are whole new worlds.”


This map from NASA’s Dawn mission shows locations of bright material on the dwarf planet Ceres. There are more than 300 bright areas, called “faculae,” on Ceres.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI/Caltech

Out of this world

Dawn launched from Cape Canaveral, Florida, on Sept. 27, 2007. Its arrived at the asteroid Vesta on July 16, 2011. The spacecraft spent almost a year in orbit around the second-largest object in the asteroid belt, departing on Sept. 5, 2012.

On March 6, 2015, Dawn entered orbit around Ceres. Ceres is by far the most massive object in the asteroid belt between Mars and Jupiter, weighing in at nearly two-thirds the total mass of the belt. Its massive size and roundness means it qualifies as a dwarf planet. Unlike a full-size planet, a dwarf planet is a round object that fails to clear out its orbit. Dawn was just barely the first mission to arrive at a dwarf planet; NASA’s New Horizons mission zipped by Pluto only a few months later (though, in fairness, New Horizons launched first but had much farther to travel).

Dawn traveled 1.7 billion miles (2.8 billion kilometers) to reach Vesta, then another 3.1 billion miles (4.9 billion km) to Ceres. Boosted by an ion propulsion system, the spacecraft took four days to accelerate from 0 to 60 mph (0 to 97 km/h) at maximum throttle. Each engine produces about the same amount of force as a single piece of paper notebook paper presses against your hand.

Over time, however, that small force adds up. In 2010, it surpassed the previous record for velocity change held by NASA’s Deep Space 1 when its accumulated acceleration over the mission exceeded 9,600 MPH (4.3 km per second).

“I am delighted that it will be Dawn that surpasses DS1’s record,” Rayman, who was a previous project manager for Deep Space 1, said in a statement. “It is a tribute to all those involved in the design and operations of this remarkable spacecraft.

NASA Deep Space 1

Ion engines are extremely fuel-efficient — Dawn only carried 937 lbs. (425 kilograms) of xenon propellant at launch — but the fuel won’t last forever. The spacecraft also carried 100.5 lbs. (45.6 kg) of hydrazine propellant used to change the spacecraft’s orientation, and that tank is quickly running dry. Dawn is expected to run out of hydrazine fuel in the second half of 2018.

“When the last of the hydrazine is exhausted, the spacecraft will no longer be able to control its orientation, so it won’t be able to point its solar arrays at the sun, its sensors at Ceres, nor its antenna at Earth,” Rayman told in 2017. “That will be the end of Dawn’s operational life.”

Dawn will continue to orbit Ceres for decades. Planetary protection rules insisted on at least 20 years before the spacecraft crashed into the dwarf planet, to reduce the chances of contamination. The Dawn team opted to set the spacecraft on an orbit that would keep it aloft for at least 50 years.

The dwarf planet Ceres spins in this series of photos captured by NASA’s Dawn spacecraft on April 29, 2017, when the probe was between Ceres and the sun.

Exploring Vesta

Dawn’s first stop was Vesta, a rocky asteroid and the second largest inhabitant of the asteroid belt, where it made several significant findings at Vesta. It discovered a geologic landscape that scientists called “exotic and diverse,” and compiled the first map of the 330-mile (530 km) wide body.

The Dawn team reasoned that reaching those temperatures would have caused the heavy elements to melt and sink down to the core in a process known as differentiation. In fact, joked JPL’s Carol Raymond, Dawn’s deputy principal investigator, “We like to call Vesta ‘the smallest terrestrial planet.'”

Dawn also confirmed that Vesta is the source of the howardite-eucrite-diogenite (HED) meteorites found on Earth and Mars. The Dawn team thinks that the HEDs came from an impact basin the team named Rheasilvia. The basin itself has an age of about 1 billion years, and formed from a massive collision that stripped the away the bulk of the asteroid’s southern hemisphere. With a diameter of 310 miles (500 km), Rheasilvia is nearly as large as Vesta itself.

“Vesta likely came close to shattering,” said Raymond.

A second basin showcases another dangerous impact beneath Rheasilvia. Named Veneneia, the basin is nearly as big and nearly a billion years younger than Rheasilvia and may be another potential source for HED meteorites.

Research from Dawn also suggests that Vesta may hide ice beneath its surface. Originally, the scientists suspected that roughness on the asteroid’s surface came from impacts, but Dawn’s data suggests that some of the features are caused by ice buried beneath the surface.

“We suggest that modifications of the surface by melting of buried ice could be responsible for smoothing those areas,” Essam Heggy, a planetary scientist at the University of Southern California in Los Angeles, told “Buried ice could have been brought to the surface after an impact, which caused heated ice to melt and travel up through the fractures to the surface.”

“We went to Vesta to fill in the blanks of our knowledge about the early history of our solar system,” said Dawn principal investigator Christopher Russell, of UCLA, said in a statement.

“Dawn has filled in those pages, and more, revealing to us how special Vesta is as a survivor from the earliest days of the solar system. We can now say with certainty that Vesta resembles a small planet more closely than a typical asteroid.”


215 years after its discovery, we know so much more about the dwarf planet Ceres. NASA’s Dawn spacecraft captured this amazing view of Ceres in the asteroid belt, showing the dwarf planet’s Occator Crater in false color, after it arrived in orbit around Ceres in 2015. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Ceres science

While Vesta is rocky, Ceres is surprisingly icy. Before Dawn arrived, scientists estimated that water could make up as much as a quarter of the dwarf planet, though that water would be tucked beneath the surface. Observations made by the Hubble Space Telescope revealed a cloud of vapor that suggested the dwarf planet might be degassing, though no strong signs of such activity has been spotted by Dawn.

On the surface, Ceres appears relatively bland. Aside from a few craters — though less than scientists anticipated — the only outstanding feature is a single mountain, Ahuna Mons. Researchers suspected the mountain was a cryovolcano, oozing ice instead of hot lava. Further studies revealed that, while it may be thought of as a “lonely mountain” today, it could have had companions in the past. Made of ice, these mountains may have slowly flowed back onto the surface.

“We think we have a very good case that there have been lots of cryovolcanoes on Ceres but they have deformed,” Dawn researcher Michael Sori of the University of Arizona in Tucson said in a statement.

The same fate may await the lonely volcano.

“Ahuna Mons is at most 200 million years old. It just hasn’t had time to deform,” Sori said.

From a distance, Dawn caught sight of bright spots from a distance that soon resolved into more than 130 bright patches, most of them tied to craters. Initially thought to be Epsom salt, the patches turned out to be a version of salts that require water to form. Since water skips to gas almost immediately on the dwarf planet’s surface, that suggests that the liquid must lie beneath the crust.

“That was something we had not expected,” Russell told “The carbonates are a very strong indication of the processes now that we believe took place in the interior, that makes it more Earthlike, when it can alter the chemistry inside.”

“It’s not something that’s just lying around out there in space,” he added.

The flowing ice that formed Ahuna Mons and the presence of salts suggest that an ancient ocean once lie beneath the crust of Ceres.

“We believe these bright spots are a sign that Ceres once had a global ocean,” planetary geologist Lynnae Quick, of the Smithsonian Institute in Washington, D.C., told

“It’s possible there is still brine coming up to the surface,” Nathan Stein, a planetary scientist at the California Institute of Technology in Pasadena, told “It’s certainly intriguing.”

Researchers also spotted ammonia-rich clays on the dwarf planet. Ammonia is more commonly found in the outer solar system. The material could have been delivered to Ceres by comets, or its presence could be a sign that the dwarf planet formed in the outer solar system.

These and other discoveries by Dawn have revealed that Ceres is a rich, evolving world.

“The IAU [International Astronomical Union] has defined what a planet is in a particular way,” Russell said, “but I think of a planet more as a body which, when it’s big enough and has enough activity … is now making things, producing things in its interior that are not just sitting there for the eons but in fact that the body evolves with time inside.”

Additional resources

NASA Dawn mission
Dawn mission home page (JPL)

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From “Hayabusa2: Japan’s 2nd Asteroid Sample Mission”

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March 30, 2018
Elizabeth Howell

JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

Hayabusa2 is a Japanese asteroid-sampling spacecraft that launched in December 2014. It is currently on the way to asteroid 162173 Ryugu and will arrive there between June and July 2018, according to the Japanese Aerospace Exploration Agency (JAXA). The mission is a follow-up of Hayabusa, which returned samples of asteroid 25143 Itokawa to Earth in 2010 despite numerous technical difficulties.

JAXA’s original Hayabusa spacecraft

Mission development

Hayabusa2 was first selected by Japan’s Space Activities Commission in 2006, and received funding in August 2010 (shortly after Hayabusa’s return). The cost is estimated at 16.4 billion yen ($150 million).

A year after launch, Hayabusa2 briefly returned to Earth. The spacecraft made a planned flyby to get a speed boost by using the Earth’s gravitational field. Meanwhile, astronomers are doing periodic observations of Ryugu to gather information ahead of the spacecraft’s arrival. The 600-kg spacecraft is expected to remain at the asteroid for 18 months, and return to Earth in 2020 with samples on board.

The basic configuration of Hayabusa2 is very similar to Hayabusa, except for some improved technology, according to JAXA. Here are some of the improvements on Hayabusa2.

Ion engine: Improving the lifespan of the neutralizers (which failed on Hayabusa) by strengthening the internal magnetic field. Also, more careful checks of the ion engine will be performed to improve its propulsion generation and ignition stability.
Sampler mechanism: Better seal performance, more compartments and an improved mechanism for picking up material from the surface. On Hayabusa, it was unclear at the time of sample collection if it had actually picked up something from the surface.
Re-entry capsule: JAXA has added an instrument to measure acceleration, movement and interior temperatures during flight. (The Hayabusa capsule broke up during re-entry.)
Flat antennas: Instead of Hayabusa’s parabolic antenna, Hayabusa2 will have flat antennas. This will allow it to have the same communications capacity as Hayabusa, while saving on weight (and launch fuel). “A flat antenna can perform to the same capacity as a parabolic antenna due to technological improvements … Thanks to the flat design, the weight of the antenna is reduced to one-fourth, compared to a parabolic antenna whose performance is the same.” JAXA said.

Here are the major instruments of the mission:

Small Carry-on Impactor (SCI): This will create an artificial crater on the surface of the asteroid. Hayabusa2 will look at the changes on the surface before and after the impact takes place. They will also sample the crater to get “fresh” materials from underground.
Near InfraRed Spectrometer (NIRS3) and Thermal Infrared Imager (TIR): The spectrometer will look at mineral composition of the asteroid, and the properties of water there. The imager will study the temperature and thermal inertia (resistance to changing temperature) of the asteroid.
The small rovers MINERVA-II: Three small rovers will bounce along the surface and collect data from close-up. They are successors to the MINERVA rover aboard Hayabusa, which failed to meet its target after launch.
A small lander (MASCOT): This is a lander that will jump only once after it arrives on the surface. It will also perform close-up observations of the surface. This instrument is built by DLR (Germany’s space agency) and the CNES (France’s space agency).

Science goals

Japan chose a different type of asteroid to study for Hayabusa2. The goal is to collect information about a wide variety of asteroids across the solar system. Ryugu is a C-type asteroid, meaning that it is carbonaceous; with a high percentage of carbon, this is the most common type of asteroid in the solar system. (The target for Hayabusa was Itokawa, an S-type asteroid — meaning that it is made up more of stony materials and nickel iron.)

Ryugu is an older type of body than Itokawa, and likely contains more organic or hydrated minerals, JAXA stated. Organics and water are key elements for life on Earth, although their presence on other bodies doesn’t necessarily mean life itself. “We expect to clarify the origin of life by analyzing samples acquired from a primordial celestial body such as a C-type asteroid to study organic matter and water in the solar system, and how they co-exist while affecting each other,” JAXA said.

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From SETI Institute via “‘Search for Extraterrestrial Intelligence’ Needs a New Name, SETI Pioneer Says”

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SETI Institute


January 25, 2018
Calla Cofield

Jill Tarter at the Arecibo radio telescope in Puerto Rico, which was used to search for communications signals from alien civilizations.
Credit: Acey Harper/The LIFE Images Collection/Getty

NAIC/Arecibo Observatory, Puerto Rico, USA, at 497 m (1,631 ft)

Astrophysicist Jill Tarter is one of the world’s best-known leaders in the search for extraterrestrial intelligence, or SETI. For 35 years, she served as the director of the Center for SETI Research (part of the SETI institute) and was also the project scientist for NASA’s SETI program, before its cancellation in 1993.

Despite her longtime association with that four-letter acronym, Tarter says it’s time for “SETI” to be rebranded.

At a recent meeting of the National Academy of Sciences’ Committee on Astrobiology Science Strategy for the Search for Life in the Universe, held here at the University of California, Irvine, Tarter explained that the phrase “search for extraterrestrial intelligence” generates an incorrect perception of what scientists in this field are actually doing. A more appropriate title for the field, she said, would be “the search for technosignatures,” or signs of technology created by intelligent alien civilizations.

“We need to be very careful about our language,” Tarter said during a presentation at the committee meeting on Jan. 18. “SETI is not the search for extraterrestrial intelligence. We can’t define intelligence, and we sure as hell don’t know how to detect it remotely. [SETI] … is searching for evidence of someone else’s technology. We use technology as a proxy for intelligence.

“[The acronym] ‘SETI’ has been problematic in history, and we should just drop [it] and just continue to talk about a search for technosignatures,” she said.

Signs of life

What constitutes a “technosignature”? Tarter reviewed some of the possibilities that she and other SETI scientists have proposed.

“We have a pragmatic definition for technology, which is the ability to deliberately modify an environment in ways that can be sensed over interstellar or interplanetary distances, including the unintended consequences of that modification,” Tarter said. “Life does this, but it doesn’t do it deliberately.”

One technosignature that scientists have been actively seeking for decades is communication signals. These could include signals used by members of an alien civilization to communicate with each other or attempts to communicate with other civilizations. The SETI Institute continues to search for alien communications in radio waves, using the Allen Telescope Array.

SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA, Altitude 986 m (3,235 ft)

(Tarter was the inspiration for the main character in Carl Sagan’s novel Contact, which was adapted into a movie; in that story, aliens make contact with Earth via radio waves.) But recent SETI efforts have expanded to look for other mediums of alien communication, and SETI scientists have theorized that an interstellar civilization might use laser light to communicate.

Laser SETI, the future of SETI Institute research

Science-fiction writer Arthur C. Clarke wrote that “any sufficiently advanced technology is indistinguishable from magic,” which would mean that alien technology could be as mysterious and unexplainable to humans as technologies that appear in science-fiction TV shows and movies. That opens up a dauntingly large range of possibilities for what technosignatures might look like. What if an alien civilization were communicating via a mechanism that Earth-based scientists haven’t discovered yet? Would humans immediately recognize these “magical” technosignatures, or would we not see them as unnatural?

Tarter said she prefers to focus on a slight alteration of Clarke’s prediction written by the futurist Karl Schroeder: “Any sufficiently advanced technology is indistinguishable from nature.”

“[The system] will be so efficient that there will be no wastage, and [it] will appear to be natural,” Tarter said. If this prediction is correct, it might also be impossible for humans to identify technosignatures from very advanced civilizations. But Tarter uses it as a jumping-off point to brainstorm how scientists might identify technologies that have not yet reached that level of sophistication.

In the field of exoplanet science, new techniques and new instruments are increasing scientists’ ability to study exoplanets and gather information about their atmospheres and surface conditions. The central focus in that field is to find habitable planets, or planets with “unintelligent” life-forms (like plants). Tarter said those tools could also provide the opportunity to look for signs of technology that artificially alters a planet’s climate or conditions.

“As we begin to look for exoplanets and image them, you might get an unexpected glint, [because] maybe mirrors re cooling their planet, reflecting light away from the planet,” Tarter said.

But a technosignature wouldn’t necessarily have to be the detection of the technology itself. The artificial alteration of a planet’s climate could be revealed simply because the planet in question is too close or too far away from its parent star to have the observed climate. A star system with multiple planets that all have similarly moderate, habitable climates, despite their particular proximity to the parent star, could indicate large-scale bioengineering by an intelligent civilization, Tartar said.

“[An alien civilization] also might want to decrease latitudinal variation in temperature; maybe they want more of their planet to be nice and cozy,” Tarter said. “It’s going to take a lot of energy to do that, but I don’t know the physics that says you can’t.”

Into the future

The search for technosignatures is daunting, but Tarter says now is “a really opportunistic time” for it. The field is benefiting from new instruments and a wider array of instruments. SETI scientists are often searching through large volumes of data, seeking the proverbial needle in the haystack. Artificial intelligence and artificial “neural networks” can help aid this effort by combing through this vast data to search for signals that the scientists program machines to find and also allowing “the data to tell us what kind of signals are there,” Tarter said, which increases the odds of finding an unanticipated technosignature.

Tarter listed multiple SETI projects and initiatives that are underway around the world. The most high-profile is Breakthrough Listen, a private initiative that has funded a group of researchers at the University of California, Berkeley to utilize various telescopes to search for signs of alien communication or other possible technosignatures.

Breakthrough Listen Project


Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

GBO radio telescope, Green Bank, West Virginia, USA

CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

The Berkeley group has led an effort to crack the mystery of Boyajian’s star, which has exhibited a very strange pattern of dimming and brightening. A few years ago, some researchers proposed that perhaps the strange light patterns were created by an alien megastructure orbiting the star — a fantastic example of a technosignature. Though that possibility has largely been ruled out, the Breakthrough Listen researchers are still working to understand this phenomenon.

The challenge of searching for alien technosignatures may be daunting, but Tarter remains unwavering in her optimism for the search for life beyond Earth.

“In 2004, Craig Venter and Daniel Cohen made a really bold statement: They said the 20th century had been the century of physics, but the 21st century would be the century of biology,” Tarter said. “I think they were right, but I don’t think they were bold enough. Because I think the 21st century is going to be the century of biology on Earth and beyond.”

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From “Lightning Bolts Are Churning Out Antimatter All Over Planet Earth”

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November 27, 2017
Rafi Letzter

Credit: Vasin Lee/Shutterstock

Particles split in the hot belly of a lightning bolt. Radioactive particles decay in the afterglow. Gamma rays rain down to Earth.

Teruaki Enoto, a physicist at Kyoto University in Japan, proved for the first time, in a paper published Nov. 23 [Nature], that lightning bolts work as natural particle accelerators. Enoto and his co-authors’ results confirm for the first time speculation dating back to 1925 [Proceedings of the Physical Society of London] about this phenomenon. Back then, scientists suggested that energized, radioactive particles might zip through the booms and flashes of a thunderstorm. Those particles emit energy at precise wavelengths, which Enoto and colleagues are the first to detect.

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