Asteroid Tracking Network Observes Close Approach

On Oct. 12 EDT (Oct. 11 PDT), a small asteroid designated 2012 TC4 will safely pass by Earth at a distance of approximately 26,000 miles (42,000 kilometers). This is a little over one tenth the distance to the Moon and just above the orbital altitude of communications satellites. This encounter with TC4 is being used by asteroid trackers around the world to test their ability to operate as a coordinated international asteroid warning network.

2012 TC4 is estimated to be 50 to 100 feet (15 to 30 meters) in size. Orbit prediction experts say the asteroid poses no risk of impact with Earth. Nonetheless, its close approach to Earth is an opportunity to test the ability of a growing global observing network to communicate and coordinate its optical and radar observations in a real scenario.

This asteroid was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii in 2012. Pan-STARRS conducts a near-Earth object (NEO) survey funded by NASA’s NEO Observations Program, a key element of NASA’s Planetary Defense Coordination Office. However, 2012 TC4 traveled out of the range of asteroid-tracking telescopes shortly after it was discovered.

Based on the observations they were able to make in 2012, asteroid trackers predicted that it should come back into view in the fall of 2017. Observers with the European Space Agency and the European Southern Observatory were the first to recapture 2012 TC4, in late July 2017, using one of their large 8-meter aperture telescopes.Since then, observers around the world have been tracking the object as it approaches Earth and reporting their observations to the Minor Planet Center.

This “test” of what has become a global asteroid-impact early-warning system is a volunteer project, conceived and organized by NASA-funded asteroid observers and supported by the NASA Planetary Defense Coordination Office (PDCO).

As explained by Michael Kelley, program scientist and NASA PDCO lead for the TC4 observation campaign, “Asteroid trackers are using this flyby to test the worldwide asteroid detection and tracking network, assessing our capability to work together in response to finding a potential real asteroid-impact threat.”

No asteroid currently known is predicted to impact Earth for the next 100 years.

Asteroid TC4’s closest approach to Earth will be over Antarctica at 1:42 AM EDT on Oct. 12 (10:42 p.m. PDT on Oct. 11). Tens of professionally run telescopes across the globe will be making ground-based observations in wavelengths from visible to near-infrared to radar. Amateur astronomers may contribute more observations, but the asteroid will be very difficult for backyard astronomers to see, as current estimates are that it will reach a visual magnitude of only about 17 at its brightest, and it will be moving very fast across the sky.

Many of the observers who are participating in this exercise are funded by NASA’s NEO Observations Program, but observers supported by other countries’ space agencies and space institutions around the world are now involved in the campaign.

Vishnu Reddy, an assistant professor at the University of Arizona’s Lunar and Planetary Laboratory in Tucson, is leading the 2012 TC4 campaign. Reddy is principal investigator for a NASA-funded near-Earth asteroid characterization project. “This campaign is a team effort that involves more than a dozen observatories, universities and labs around the globe so we can collectively learn the strengths and limitations of our near-Earth object observation capabilities,” he said. “This effort will exercise the entire system, to include the initial and follow-up observations, precise orbit determination, and international communications.”

In September, asteroid observers were able to conduct a “pre-test” of coordinated tracking of the close approach of a much larger asteroid known as 3122 Florence. Florence, one of the largest known NEOs, at 2.8 miles (4.5 kilometers) in size, passed by Earth on Sept. 1 at 18 times the distance to the Moon. Coordinated observations of this asteroid revealed, among other things, that Florence has two moons.

Scientists Discover One Of The Most Luminous ‘New Stars’ Ever

Astronomers have today announced that they have discovered possibly the most luminous ‘new star’ ever — a nova discovered in the direction of one of our closest neighboring galaxies: The Small Magellanic Cloud.

Astronomers from the University of Leicester contributed to the discovery by using the Swift satellite observatory to help understand what was likely the most luminous white dwarf eruption ever seen.

A nova happens when an old star erupts dramatically back to life. In a close binary star system consisting of a white dwarf[1] and a Sun-like companion star, material is transferred from the companion to the white dwarf, gradually building up until it reaches a critical pressure. Then uncontrolled nuclear burning occurs, leading to a sudden and huge increase in brightness. It is called a nova because it appeared to be a new star to the ancients.

Novae are usually found in visible light, but often go on to emit higher energy X-rays as well. Together, these different datasets provide information on the white dwarf, such as its temperature and chemical composition.

Using telescopes from South Africa to Australia to South America, as well as the orbiting Swift observatory, a team led by the South African Astronomical Observatory has revealed that the nova SMCN 2016-10a, which was discovered on 14th October 2016, is the most luminous nova ever discovered in the SMC, and one of the brightest ever seen in any galaxy. The observations that they made are the most comprehensive ever for a nova in this galaxy.

The SMC, 200,000 light-years away, is one of our closest companion galaxies; it is a dwarf galaxy, very much less massive than our own. Novae occur frequently in our Galaxy, with a rate of around 35 each year, but SMCN 2016-10a is the first nova to have been detected in the SMC since 2012.

Dr Kim Page, a member of the Swift team at the University of Leicester, led the X-ray analysis, while Paul Kuin, from the Mullard Space Science Laboratory, University College London, organised the UV data.

Dr Page said: “Swift’s ability to respond rapidly, together with its daily-planned schedule, makes it ideal for the follow-up of transients, including novae. It was able to observe the nova throughout its eruption, starting to collect very useful X-ray and UV data within a day of the outburst first being reported. The X-ray data were essential in showing that the mass of the white dwarf is close to the theoretical maximum; continued accretion might cause it eventually to be totally destroyed in a supernova explosion.”

Dr Kuin added:”The present observations provide the kind of coverage in time and spectral colour that is needed to make progress for gaining understanding of a nova in a neighbouring galaxy. Observing the nova in different wavelengths using world-class telescopes such as Swift and the Southern African Large Telescope help us reveal the condition of matter in nova ejecta as if it were nearby.”

Professor Julian Osborne, who leads the Swift team at the University of Leicester, and was also involved in this study, said: “Although it is difficult to measure the distance to novae directly, its position in the SMC on the sky, and everything else we know about this nova point to it being in this dwarf galaxy. This makes the nova as intrinsically bright as the most luminous ever seen, and thus very interesting in trying to understand these explosions.”

The paper, entitled “Multiwavelength observations of nova SMCN 2016-10a — Probably the brightest nova in the SMC and one of the brightest on record” has been accepted for publication in Monthly Notices of the Royal Astronomical Society.

Two Separate Teams Of Astronomers Find Evidence Of Missing Baryonic Matter

Two teams working independently have found evidence of the existence of Baryonic matter—particles that link galaxies together. One team was made of members from the Institute of Space Astrophysics, the other was based out of the University of Edinburgh. Both teams have uploaded a paper describing their work to the arXiv preprint server and both are claiming their findings solve the mystery of where so much of the normal matter—protons, neutrons and electrons—in the universe has been hiding.

Once scientists came up with the Big Bang Theory, a problem immediately arose—after calculating how much normal matter should exist in the universe at this point in time, they found approximately 50 percent of it is missing. Since then, scientists have worked on theories to explain where all that matter was hiding—the prevailing theory suggests that it exists as strands of Baryonic matter floating in the space between galaxies and cannot be seen with conventional instruments—this was the theory both teams in this new effort tested.

To get around the problem of not being able to see the Baryonic matter directly, the researchers considered a phenomenon called the Sunyaev-Zel’dovich effect in which light left over from the Big Bang scatters as it passes through hot gas—it should be measurable in the cosmic microwave background. Both teams used data from the Planck satellite launched two years ago to create a map of where Baryonic matter strands might exist. Each selected a pair of galaxies to study, focusing on the space between them. Then, they stacked data from between the two galaxies to magnify data believed to be from Baryonic matter.

Both teams repeated this process for multiple pairs of galaxies to show that their readings were consistent across multiple test sites—one team tested a million pairs, the other 260,000. Both report finding evidence of the theorized filaments between the galaxies. One group found them to be three times as dense as the mean of observable matter, the other group six times—a difference that was expected, the groups explain, due to differences in distances from the galaxies that were studied.

Both groups claim their findings prove the existence of missing Baryonic matter and thus solve the mystery of where all the unmeasurable matter has been hiding.

Astronomers Use IAC Instrument To Probe The Origins Of Cosmic Rays

In November 1572 a supernova explosion was observed in the direction of the constellation of Cassiopeia, and its most famous observer was Tycho Brahe, one of the founders of modern observational astronomy. The explosion produced an expanding cloud of superhot gas, a supernova remnant which was rediscovered in 1952 by British radioastronomers, confirmed by visible photographs from Mount Palomar observatory, California, in the 1960’s, and a spectacular image was taken in X-rays by the Chandra satellite observatory in 2002. Astronomers use supernova remnants to explore high energy physics in interstellar space.

In an article to be published in the Astrophysical Journal a team from 7 countries, including researchers at the Instituto de Astrofísica de Canarias (IAC), has observed the Tycho supernova remnant with GHaFaS, a sophisticated instrument from the IAC, mounted on the 4.2m William Herschel Telescope (WHT) at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands). Their aim was to explore the hypothesis that the cosmic rays, high energy sub-atomic particles which continually bombard the Earth’s outer atmosphere, originate in these highly energetic gas clouds. GHaFaS allows astronomers to observe the emission from ionized hydrogen across wide fields, giving a map of the velocity structure within an object in fine detail.

They mapped a sizeable portion of the Tycho remnant cloud, including a prominent bright filament, and showed that the hydrogen line emitted from the filament shows a much bigger spread of velocities than can be explained from the temperature of the gas. In fact they measured two components of emission, one with a large velocity spread, and another with an even larger spread. They showed that the only way for the emission to show these characteristics is if there is a mechanical mechanism in the cloud producing high energy particles. Supernova remnants have long been considered a probable source of the cosmic rays which pour onto the outer atmosphere of the Earth, but this is the first time that clear evidence for an acceleration mechanism has been produced. Cosmic rays have energies much higher than those produced in even the biggest particle accelerators on Earth (such as CERN), and their study is important not only for astrophysics but for particle physics.

“These results could not have been produced by any of the other spectrographs on major telescopes in the world” says Joan Font, one of the authors of the article, and the person responsible for the operations of GHaFaS. “Our instrument has a unique combination of high velocity resolution, wide field, and good angular resolution, and this combination was required for the Tycho project”. These observations are a first step towards a fuller understanding of the cosmic ray acceleration mechanism in supernova remnants. “We should be able to combine these results with observations already taken using the OSIRIS narrow band imager on the 10.4m Gran Telescopio CANARIAS (GTC) to determine the efficiency of acceleration of the cosmic rays” says John Beckman, another IAC researcher and a co-author on the paper.

Seeing Double: Scientists Find Elusive Giant Black Hole Pairs

Astronomers have identified a bumper crop of dual supermassive black holes in the centers of galaxies. This discovery could help astronomers better understand how giant black holes grow and how they may produce the strongest gravitational wave signals in the Universe.

The new evidence reveals five pairs of supermassive black holes, each containing millions of times the mass of the Sun. These black hole couples formed when two galaxies collided and merged with each other, forcing their supermassive black holes close together.

The black hole pairs were uncovered by combining data from a suite of different observatories including NASA’s Chandra X-ray Observatory, the Wide-Field Infrared Sky Explorer Survey (WISE), and the ground-based Large Binocular Telescope in Arizona.

“Astronomers find single supermassive black holes all over the universe,” said Shobita Satyapal, from George Mason University in Fairfax, Virginia, who led one of two papers describing these results. “But even though we’ve predicted they grow rapidly when they are interacting, growing dual supermassive black holes have been difficult to find.”

Before this study fewer than ten confirmed pairs of growing black holes were known from X-ray studies, based mostly on chance detections. To carry out a systematic search, the team had to carefully sift through data from telescopes that detect different wavelengths of light.

Starting with the Galaxy Zoo project, researchers used optical data from the Sloan Digital Sky Survey (SDSS) to identify galaxies where it appeared that a merger between two smaller galaxies was underway. From this set, they selected objects where the separation between the centers of the two galaxies in the SDSS data is less than 30,000 light years, and the infrared colors from WISE data match those predicted for a rapidly growing supermassive black hole.

Seven merging systems containing at least one supermassive black hole were found with this technique. Because strong X-ray emission is a hallmark of growing supermassive black holes, Satyapal and her colleagues then observed these systems with Chandra. Closely-separated pairs of X-ray sources were found in five systems, providing compelling evidence that they contain two growing (or feeding) supermassive black holes.

Both the X-ray data from Chandra and the infrared observations suggest that the supermassive black holes are buried in large amounts of dust and gas.

“Our work shows that combining the infrared selection with X-ray follow-up is a very effective way to find these black hole pairs,” said Sara Ellison of the University of Victoria in Canada, who led the other paper describing these results. “X-rays and infrared radiation are able to penetrate the obscuring clouds of gas and dust surrounding these black hole pairs, and Chandra’s sharp vision is needed to separate them”.

The paper led by Ellison used additional optical data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to pinpoint one of the new black hole pairs. One member of this black hole pair is particularly powerful, having the highest X-ray luminosity in a black hole pair observed by Chandra to date.

This work has implications for the burgeoning field of gravitational wave astrophysics. While scientists using the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the VIRGO interferometer have detected the signals of merging black holes, these black holes have been of the smaller variety weighing between about eight and 36 times the mass of the Sun.

The merging black holes in the centers of galaxies are much larger. When these supermassive black holes draw even closer together, they should start producing gravitational waves. The eventual merger of the dual supermassive black holes in hundreds of millions of years would forge an even bigger black hole. This process would produce an astonishing amount of energy when some of the mass is converted into gravitational waves.
“It is important to understand how common supermassive black hole pairs are, to help in predicting the signals for gravitational wave observatories,” said Satyapal. “With experiments already in place and future ones coming online, this is an exciting time to be researching merging black holes. We are in the early stages of a new era in exploring the universe.”

LIGO/VIRGO is not able to detect gravitational waves from supermassive black hole pairs. Instead, pulsar timing arrays such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) are currently performing this search. In the future, the Laser Interferometer Space Antenna (LISA) project could also search for these gravitational waves.

Four of the dual black hole candidates were reported in a paper by Satyapal et al. that was recently accepted for publication in The Astrophysical Journal, and appears online. The other dual black hole candidate was reported in a paper by Ellison et al., which was published in the September 2017 issue of the Monthly Notices of the Royal Astronomical Society and appears online.

Explosive Bursts Of Methane Helped Ancient Mars Keep Liquid Water Flowing, Study Finds

In a drying time, Mars may have been kept warm enough for liquid water to remain stable on the surface thanks to explosive bursts of methane gas, a new study finds.

The simulations, described in the journal Nature Geoscience, could explain how Mars managed to sustain a series of lakes in a climate that at first glance seems too cold and arid to have done so.

Since landing on the Red Planet in August 2012, NASA’s rover Curiosity has discovered that 96-mile-wide Gale Crater held a series of lakes around 3.5 billion years ago. The rocks it has drilled and X-rayed and lasered have also revealed environments that would have been potentially habitable for Earth-like life.

Keep in mind, however, that Mars’ wettest period was likely the first billion years of its 4.6 billion-year life, the Noachian period, when it had a thicker atmosphere that would have been better able to keep liquid water stable on the planet’s surface.

“Although the climate was relatively cold compared to Earth, there is evidence that liquid water flowed in streams and rivers, formed alluvial fans and deltas, and ponded in big lakes and possibly seas,” Alberto Fairen of the Centro de Astrobiologia in Spain and Cornell University, who was not involved in the paper, wrote in a commentary.

Then came the 600 million-year Hesperian period, when the Red Planet began to transform from a cold, wet world to a cold, icy one, as the protective atmosphere thinned and the planet’s interior cooled. The next 3 billion years until now are known as the Amazonian period, during which Mars solidified its reputation as the cold, dry planet we see today.

So here’s the thing that’s puzzled planetary scientists: Gale Crater’s rocks bear evidence of liquid water on Mars during the Hesperian period, including lakes (perhaps protected by a layer of surface ice) and deltas. But that means these lakes and deltas persisted during a period that was markedly drier, with a thinner atmosphere less capable of sustaining liquid water. How do these two facts square up?

“Previous hypotheses have struggled to explain lake-forming climates that are both rare and long-lasting,” Fairen wrote. “For example, volcanism and impacts can produce episodes of climate warming, but not of sufficiently long duration.”

Now, lead author Edwin Kite, a planetary scientist the University of Chicago, and his colleagues say that after running climate models they’ve come up with an explanation: explosive bursts of methane.

Here’s how it works. The Red Planet’s obliquity, or tilt on its axis, can vary far more dramatically than Earth’s does. The researchers think that occasional dramatic shifts in that tilt (perhaps around 10 to 20 degrees) would have exposed ice-covered parts of the Martian surface to the sun, causing that cover to shrink fairly quickly. The ice’s retreat would have exposed clathrates filled with pockets of methane, allowing the methane to burst out of the ground and into the atmosphere.

Methane is a powerful greenhouse gas – about 25 times as powerful as carbon dioxide. So if enough of it were to emerge from the ground at the same time, it could actually result in a significant amount of warming, the thinking goes.

Now, eventually, methane gets broken down by sunlight. But in the meantime, Kite and his colleagues found that it could lead to warming lasting hundreds of thousands of years – long enough to explain the extended presence of liquid water during this otherwise dry time in Martian history, scientists say.

What does this mean for the possibility that life could have emerged on Mars? Kite was quick to point out that if any microbes ever lived on the Red Planet, they would likely have done so during its earliest days, when water was far more abundant.

“If life ever established itself on Mars, then it would have probably done so before the relatively young (less than 3.6 billion years ago) features modeled in our paper,” Kite wrote in an email.

Regardless, the study reveals an increasingly complex portrait of a planet in transition, scientists said.

“The methane burst scenario proposed by Kite et al. contributes to an emerging view that the existence of liquid water on early Mars arose from a combination of diverse astronomical, geochemical and geological factors,” Fairen wrote. “Although it seems unlikely that a single mechanism can explain not only the presence of liquid water, but its recurrence and persistence, the methane burst hypothesis provides a means to episodically tip the Hesperian climate over the edge.”

Meteorite Tells Us That Mars Had A Dense Atmosphere 4 Billion Years Ago

Exploration missions have suggested that Mars once had a warm climate, which sustained oceans on its surface. To keep Mars warm requires a dense atmosphere with a sufficient greenhouse effect, while the present-day Mars has a thin atmosphere whose surface pressure is only 0.006 bar, resulting in the cold climate it has today. It has been a big mystery as to when and how Mars lost its dense atmosphere.

An old meteorite has been known to contain the ancient Martian atmosphere. The researchers simulated how the composition of the Martian atmosphere changed throughout history under various conditions. By comparing the results to the isotopic composition of the trapped gas, the researchers revealed how dense the Martian atmosphere was at the time when the gas became trapped in the meteorite.

The research team concluded that Mars had a dense atmosphere 4 billion years ago. The surface air pressure at the time was at least 0.5 bar and could have been much higher. Because Mars had its magnetic field about 4 billion years ago and lost it, the result suggests that stripping by the solar wind is responsible for transforming Mars from a warm wet world into a cold desert world.

NASA’s MAVEN spacecraft is orbiting Mars to explore the processes that removed the Martian atmosphere. The Japan Aerospace Exploration Agency (JAXA) is planning to further observe the removal processes by the Martian Moons eXploration (MMX) spacecraft. These missions will reveal how the dense atmosphere on ancient Mars predicted in this study was removed over time.