Asteroid impact in 2052 ruled out

Newswand: ESA’s asteroid team working with experts at the European Southern Observatory have officially ruled out asteroid impact in 2052 as they removed ‘2021 QM1’ from their asteroid risk list.

Photo credit: ESA

With Asteroid Day Live 2022 set for 30 June, we can safely say that the riskiest asteroid known to humankind in the last year will not strike – at least not for the next century.

2021 QM1 was initially discovered on 28 August 2021 by the Mount Lemmon observatory, located north of Tucson, Arizona. To start, nothing stood out as unusual about the discovery – about a dozen new near-Earth asteroids are discovered every dark night. Routine follow-up observations were then acquired from telescopes around the globe, but these started to tell a more worrying story.

“These early observations gave us more information about the asteroid’s path, which we then projected into the future,” said Richard Moissl, ESA’s Head of Planetary Defence.

“We could see its future paths around the Sun, and in 2052 it could come dangerously close to Earth. The more the asteroid was observed, the greater that risk became.”

It’s important to note that orbit calculations based on just a few nights of observations come with some uncertainty, which is why asteroids often get onto ESA’s risk list soon after they are discovered and are then removed once more data is gathered, uncertainties shrink, and the asteroid is proven safe. On this occasion, that wasn’t possible.

Unfortunate cosmic alignment

Just as the risk appeared to be increasing, an (im)perfect cosmic alignment occurred: the asteroid’s path brought it closer to the Sun as seen from Earth, and for months it became impossible to see due to our star’s brilliant glare.

“We just had to wait,” explained Marco Micheli, Astronomer at ESA’s Near-Earth Object Coordination Centre (NEOCC).

“But to cap things off, we knew that 2021 QM1 was also moving away from Earth in its current orbit – meaning by the time it passed out of the Sun’s glare, it could be too faint to detect.”

The European Southern Observatory’s Very Large Telescope (VLT) was primed and ready. As soon as the 50-meter asteroid edged out from the sunlight – and if and when weather conditions allowed – ESO’s VLT would focus its 8 m mirror on the disappearing rock.

“We had a brief window in which to spot our risky asteroid,” explained Olivier Hainaut, Astronomer at ESO.

“To make matters worse, it was passing through a region of the sky with the Milky Way just behind. Our small, faint, receding asteroid would have to be found against a backdrop of thousands of stars. These would turn out to be some of the trickiest asteroid observations we have ever made”.

Faintest asteroid ever observed

Over the night of 24 May, ESO’s VLT took a series of new images. The data arrived and Olivier and Marco began to process them, stacking subsequent observations on top of each other and removing the background stars: it took some time.

The result! A positive detection of the faintest asteroid ever observed. With a magnitude of 27 on the scale used by astronomers to describe the brightness of objects in the sky, 2021 QM1 was 250 million times fainter than the faintest stars visible to the naked eye from a dark spot. (In this astronomical scale of visible magnitudes, the brighter an object appears the lower the value of its magnitude, while the brightest objects reach negative values, e.g. the Sun is magnitude -27).

Olivier was certain this small blur was in fact an asteroid, and Marco was certain that given its location, it was our asteroid.

Safe at last!

With these new observations, our risky asteroid’s path was refined, ruling out an impact in 2052, and 2021 QM1 was removed from ESA’s risk list. Another 1377 remain.

More than one million asteroids have been discovered in the Solar System, almost 30,000 of which pass near Earth, with many more expected to be out there. ESA’s Planetary Defence Office, NEOCC and astronomers around the globe are looking up to keep us safe, working together to ensure we know well in advance if an asteroid is discovered on a collision course.

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NASA’s Curiosity takes inventory of key life ingredient on Mars

Newswand: Scientists using data from NASA’s Curiosity rover measured the total organic carbon – a key component in the molecules of life – in Martian rocks for the first time.

Yellow Life Bay of Mars. Photo credit: NASA/JPL-Caltech/MSSS

“Total organic carbon is one of several measurements [or indices] that help us understand how much material is available as feedstock for prebiotic chemistry and potentially biology,” said Jennifer Stern of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We found at least 200 to 273 parts per million of organic carbon. This is comparable to or even more than the amount found in rocks in very low-life places on Earth, such as parts of the Atacama Desert in South America, and more than has been detected in Mars meteorites.”

Organic carbon is carbon bound to a hydrogen atom. It is the basis for organic molecules, which are created and used by all known forms of life. However, organic carbon on Mars does not prove the existence of life there because it can also come from non-living sources, such as meteorites and volcanoes, or be formed in place by surface reactions.

Organic carbon has been found on Mars before, but prior measurements only produced information on particular compounds, or represented measurements capturing just a portion of the carbon in the rocks. The new measurement gives the total amount of organic carbon in these rocks.

Although the surface of Mars is inhospitable for life now, there is evidence that billions of years ago the climate was more Earth-like, with a thicker atmosphere and liquid water that flowed into rivers and seas. Since liquid water is necessary for life as we understand it, scientists think Martian life, if it ever evolved, could have been sustained by key ingredients such as organic carbon, if present in sufficient amount.

Curiosity is advancing the field of astrobiology by investigating Mars’ habitability, studying its climate and geology. The rover drilled samples from 3.5-billion-year-old mudstone rocks in the Yellowknife Bay formation of Gale crater, the site of an ancient lake on Mars. Mudstone at Gale crater was formed as very fine sediment (from physical and chemical weathering of volcanic rocks) in water settled on the bottom of a lake and was buried. Organic carbon was part of this material and got incorporated into the mudstone. Besides liquid water and organic carbon, Gale crater had other conditions conducive to life, such as chemical energy sources, low acidity, and other elements essential for biology, such as oxygen, nitrogen, and sulfur. “Basically, this location would have offered a habitable environment for life, if it ever was present,” said Stern, lead author of a paper about this research published June 27 in the Proceedings of the National Academy of Sciences.

To make the measurement, Curiosity delivered the sample to its Sample Analysis at Mars (SAM) instrument, where an oven heated the powdered rock to progressively higher temperatures. This experiment used oxygen and heat to convert the organic carbon to carbon dioxide (CO2), the amount of which is measured to get the amount of organic carbon in the rocks. Adding oxygen and heat allows the carbon molecules to break apart and react carbon with oxygen to make CO2. Some carbon is locked up in minerals, so the oven heats the sample to very high temperatures to decompose those minerals and release the carbon to convert it to CO2. The experiment was performed in 2014 but required years of analysis to understand the data and put the results in context of the mission’s other discoveries at Gale Crater. The resource-intensive experiment was performed only once during Curiosity’s 10 years on Mars.

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BepiColombo makes second flyby of Mercury successfully

Newswand: The ESA/JAXA BepiColombo mission has made its second flyby of planet Mercury on June 23 and captured new close-up images of the planet.

Photo credit: ESA

The closest approach took place at 09:44 UTC (11:44 CEST) on 23 June 2022, about 200 km above the planet’s surface. Images from the spacecraft’s three monitoring cameras (MCAM), along with scientific data from a number of instruments, were collected during the encounter.

 “We have completed our second of six Mercury flybys and will be back this time next year for our third before arriving in Mercury orbit in 2025,” says Emanuela Bordoni, ESA’s BepiColombo Deputy Spacecraft Operations Manager. 

Because BepiColombo’s closest approach was on the planet’s night side, the first images in which Mercury is illuminated were taken at around five minutes after close approach, at a distance of about 800 km. Images were taken for about 40 minutes after the close approach as the spacecraft moved away from the planet again.

As BepiColombo flew from the night side to dayside, the Sun seemingly rose over the cratered surface of the planet, casting shadows along the terminator – the boundary between night and day – and highlighting the topography of the terrain in dramatic fashion.

Jack Wright, a member of the MCAM team, and a research fellow based at ESA’s European Space Astronomy Centre (ESAC) in Madrid, helped to plan the imaging sequence for the flyby. He said: “I punched the air when the first images came down, and I only got more and more excited after that. The images show beautiful details of Mercury, including one of my favourite craters, Heaney, for which I suggested the name a few years ago.”

Heaney is a 125 km wide crater covered in smooth volcanic plains. It hosts a rare example of a candidate volcano on Mercury, which will be an important target for BepiColombo’s high resolution imaging suite once in orbit.

Just a few minutes after closest approach and with the Sun shining from above, Mercury’s largest impact feature, the 1550 km-wide Caloris basin swung into view for the first time, its highly-reflective lavas on its floor making it stand out against the darker background. The volcanic lavas in and around Caloris are thought to post-date the formation of the basin itself by a hundred million years or so, and measuring and understanding the compositional differences between these is an important goal for BepiColombo.

“Mercury flyby 1 images were good, but flyby 2 images are even better,” commented David Rothery of the Open University who leads ESA’s Mercury Surface & Composition Working Group and who is also a member of the MCAM team. “The images highlight many of the science goals that we can address when BepiColombo gets into orbit. I want to understand the volcanic and tectonic history of this amazing planet.”

BepiColombo will build on the data collected by NASA’s Messenger mission that orbited Mercury 2011-2015. BepiColombo’s two science orbiters – ESA’s Mercury Planetary Orbiter and JAXA’s Mercury Magnetospheric Orbiter – will operate from complementary orbits to study all aspects of mysterious Mercury from its core to surface processes, magnetic field and exosphere, to better understand the origin and evolution of a planet close to its parent star. 

Even though BepiColombo is currently in ‘stacked’ cruise configuration, meaning many instruments cannot be fully operated during the brief flybys, they can still grab insights into the magnetic, plasma and particle environment around the spacecraft, from locations not normally accessible during an orbital mission.

“Our instrument teams on both spacecraft have started receiving their science data and we’re looking forward to sharing our first insights from this flyby,” says Johannes Benkhoff, ESA’s BepiColombo project scientist. “It will be interesting to compare the data with what we collected on our first flyby, and add to this unique dataset as we build towards our main mission.”

BepiColombo’s main science mission will begin in early 2026. It is making use of nine planetary flybys in total: one at Earth, two at Venus, and six at Mercury, together with the spacecraft’s solar electric propulsion system, to help steer into Mercury orbit. Its next Mercury flyby will take place on 20 June 2023.

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Sulfer Dioxide found on Europa

Newswand: A Southwest Research Institute-led team which has been mapping Jupiter’s moon Europa has found concentrations of sulfer dioxide on its trailing side.

SwRI scientists used Hubble Space Telescope to image the surface of Jupiter’s fourth largest moon Europa (shown lower right in this composite image) in the ultraviolet, mapping concentrations of sulfur dioxide on its surface that likely came from Io (above), Jupiter’s ultra-volcanic moon.
Photo credit: NASA

The team used the Hubble Space Telescope to observe Jupiter’s moon, Europa, at ultraviolet wavelengths, filling in a “gap” in the various wavelengths used to observe this icy water world. The team’s near-global UV maps show concentrations of sulfur dioxide on Europa’s trailing side.

SwRI will further these studies using the Europa Ultraviolet Spectrograph (Europa-UVS), which will observe Jupiter’s fourth largest moon from aboard NASA’s Europa Clipper, scheduled to launch in 2024. Scientists are almost certain that hidden beneath Europa’s icy surface is a saltwater ocean containing nearly twice as much water as is in all of Earth’s oceans. This moon may be the most promising place in our solar system suitable for some form of life beyond Earth.

“Europa’s relatively young surface is primarily composed of water ice, although other materials have been detected across its surface,” said Dr. Tracy Becker, lead author of a paper describing these UV observations. “Determining whether these other materials are native to Europa is important for understanding Europa’s formation and subsequent evolution.”

Assessing the surface material can provide insights into the composition of the subsurface ocean. SwRI’s dataset is the first to produce a near-global map of sulfur dioxide that correlates with large-scale darker regions in both the visible and the ultraviolet wavelengths.

“The results were not surprising, but we did get much better coverage and resolution than previous observations,” said SwRI’s Dr. Philippa Molyneux, a co-author of the paper. “Most of the sulfur dioxide is seen on the ‘trailing’ hemisphere of Europa. It’s likely concentrated there because Jupiter’s co-rotating magnetic field traps sulfur particles spewing from Io’s volcanoes and slams them against the backside of Europa.”

Io is another of Jupiter’s largest moons but, in contrast, is considered the most volcanic body in the solar system. Jupiter’s magnetic field can cause chemical reactions between the water ice and the sulfur, creating sulfur dioxide on Europa’s surface.

“In addition to studying the sulfur dioxide on the surface, we are continuing to try to understand the puzzle of why Europa — which has a surface that is known to be dominated by water ice — does not look like water ice at ultraviolet wavelengths, as confirmed by this paper,” Becker said. “We are actively working to understand why.”

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Two new, rocky planets found

Newswand: An international team of astronomers led by Rafael Luque of the Institute of Astrophysics of Andalusia, Spain, and also of the University of Chicago have found two rocky worlds orbiting the relatively bright, red dwarf star HD 260655, only 33 light-years away. The new planets, HD 260655 b and HD 260655 c, are among the closest-known rocky planets yet found outside our solar system that astronomers can observe crossing the faces of their stars.

Photo credit: NASA/JPL-Caltech

Using NASA’s orbiting planet hunter, the Transiting Exoplanet Survey Satellite (TESS), they discovered sibling planets in Earth’s size-range that are prime candidates for atmospheric investigation. And the discovery comes at an ideal moment: The giant James Webb Space Telescope, soon to deliver its first science images, can examine the atmospheres of exoplanets – planets beyond our solar system – to search for water, carbon molecules and other components. Learning more about the atmospheres of rocky planets will help scientists understand the formation and development of worlds like our own.

Both planets are “super-Earths” – terrestrial worlds like ours, only bigger. Planet b is about 1.2 times as big around as Earth, planet c 1.5 times. In this case, however, neither world is likely to support life. The temperature on planet b, nearest to the star, is estimated at 816 degrees Fahrenheit (435 Celsius), planet c 543 Fahrenheit (284 Celsius), though actual temperature depends on the presence and nature of possible atmospheres.

Still, the science team that discovered the planets says they are well worth further investigation. At 33 light-years, they are relatively close to us, and their star, though smaller than ours, is among the brightest in its class. These and other factors raise the likelihood that the Webb telescope, and perhaps even the Hubble Space Telescope, could capture data from the star’s light shining through these planets’ atmospheres. Such light can be spread into a spectrum, revealing the fingerprints of molecules within the atmosphere itself.

Both planets rate in the top 10 candidates for atmospheric characterization among all terrestrial exoplanets so far discovered, the team says. That places them in the same category as one of the most famous planetary systems: the seven roughly Earth-sized planets around a star called TRAPPIST-1. The TRAPPIST-1 worlds and several other rocky exoplanets are already on the list of observation targets for the Webb telescope.

The jury is out on whether either newly discovered planet possesses an atmosphere, and if so, what it’s made of. But the science team’s analysis already has produced some intriguing clues. TESS finds exoplanets by watching for “transits” – the tiny drop in starlight when a planet passes in front of its star – which can reveal the planet’s diameter. But the scientists also used data from ground-based telescopes to confirm the existence of the two new planets. These telescopes measured the “wobble” of the star, caused by the gravitational tugs from orbiting planets, which yields the planets’ mass. Combine these measurements, and you can determine the density of the planets – in this case confirming they are rocky worlds. The measurements also suggest that if the planets do have atmospheres, they are not extended, hydrogen atmospheres.

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No signs (yet) of life on Venus

Newswand: Astronomers were unable to find any signs of life on Venus as they could not find any finger prints of it after research for the past few years.

Researchers from the University of Cambridge used a combination of biochemistry and atmospheric chemistry to test the ‘life in the clouds’ hypothesis, which astronomers have speculated about for decades, and found that life cannot explain the composition of the Venusian atmosphere.

Any life form in sufficient abundance is expected to leave chemical fingerprints on a planet’s atmosphere as it consumes food and expels waste. However, the Cambridge researchers found no evidence of these fingerprints on Venus.

Even if Venus is devoid of life, the researchers say their results, reported in the journal Nature Communications, could be useful for studying the atmospheres of similar planets throughout the galaxy, and the eventual detection of life outside our Solar System.

“We’ve spent the past two years trying to explain the weird sulphur chemistry we see in the clouds of Venus,” said co-author Dr Paul Rimmer from Cambridge’s Department of Earth Sciences. “Life is pretty good at weird chemistry, so we’ve been studying whether there’s a way to make life a potential explanation for what we see.”

The researchers used a combination of atmospheric and biochemical models to study the chemical reactions that are expected to occur, given the known sources of chemical energy in Venus’s atmosphere.

“We looked at the sulphur-based ‘food’ available in the Venusian atmosphere – it’s not anything you or I would want to eat, but it is the main available energy source,” said Sean Jordan from Cambridge’s Institute of Astronomy, the paper’s first author. “If that food is being consumed by life, we should see evidence of that through specific chemicals being lost and gained in the atmosphere.”

The models looked at a particular feature of the Venusian atmosphere – the abundance of sulphur dioxide (SO2). On Earth, most SO2 in the atmosphere comes from volcanic emissions. On Venus, there are high levels of SO2 lower in the clouds, but it somehow gets ‘sucked out’ of the atmosphere at higher altitudes.

“If life is present, it must be affecting the atmospheric chemistry,” said co-author Dr Oliver Shorttle from Cambridge’s Department of Earth Sciences and Institute of Astronomy. “Could life be the reason that SO2 levels on Venus get reduced so much?”

The models, developed by Jordan, include a list of metabolic reactions that the life forms would carry out in order to get their ‘food’, and the waste by-products. The researchers ran the model to see if the reduction in SO2 levels could be explained by these metabolic reactions.

They found that the metabolic reactions can result in a drop in SO2 levels, but only by producing other molecules in very large amounts that aren’t seen. The results set a hard limit on how much life could exist on Venus without blowing apart our understanding of how chemical reactions work in planetary atmospheres.

“If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus’s atmospheric chemistry,” said Jordan. “We wanted life to be a potential explanation, but when we ran the models, it isn’t a viable solution. But if life isn’t responsible for what we see on Venus, it’s still a problem to be solved – there’s lots of strange chemistry to follow up on.”

Although there’s no evidence of sulphur-eating life hiding in the clouds of Venus, the researchers say their method of analysing atmospheric signatures will be valuable when JWST, the successor to the Hubble Telescope, begins returning images of other planetary systems later this year. Some of the sulphur molecules in the current study are easy to see with JWST, so learning more about the chemical behaviour of our next-door neighbour could help scientists figure out similar planets across the galaxy.

“To understand why some planets are alive, we need to understand why other planets are dead,” said Shorttle. “If life somehow managed to sneak into the Venusian clouds, it would totally change how we search for chemical signs of life on other planets.”

“Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host life,” said Rimmer, who is also affiliated with Cambridge’s Cavendish Laboratory. “We can take what we’ve learned here and apply it to exoplanetary systems – this is just the beginning.”

The research was funded by the Simons Foundation and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

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Mysterious Fast Radio Bursts raise many questions

Newswand: Mysterious Fast Radio Bursts from the space have left astronomers surprised as they have raised many questions.

Photo credit: National Radio Astronomy Observatory

They have found only the second example of a highly active, repeating Fast Radio Burst (FRB) with a compact source of weaker but persistent radio emission between bursts. The discovery raises new questions about the nature of these mysterious objects and also about their usefulness as tools for studying the nature of intergalactic space. The scientists used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and other telescopes to study the object, first discovered in 2019.

The object, called FRB 190520, was found by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China. A burst from the object occurred on May 20, 2019, and was found in data from that telescope in November of that year. Follow-up observations with FAST showed that, unlike many other FRBs, it emits frequent, repeating bursts of radio waves.

Observations with the VLA in 2020 pinpointed the object’s location, and that allowed visible-light observations with the Subaru telescope in Hawaii to show that it is in the outskirts of a dwarf galaxy nearly 3 billion light-years from Earth. The VLA observations also found that the object constantly emits weaker radio waves between bursts.

“These characteristics make this one look a lot like the very first FRB whose position was determined — also by the VLA — back in 2016,” said Casey Law, of Caltech. That development was a major breakthrough, providing the first information about the environment and distance of an FRB. However, its combination of repeating bursts and persistent radio emission between bursts, coming from a compact region, set the 2016 object, called FRB 121102, apart from all other known FRBs, until now.

“Now we have two like this, and that brings up some important questions,” Law said. Law is part of an international team of astronomers reporting their findings in the journal Nature.

The differences between FRB 190520 and FRB 121102 and all the others strengthen a possibility suggested earlier that there may be two different kinds of FRBs.

“Are those that repeat different from those that don’t? What about the persistent radio emission — is that common?” said Kshitij Aggarwal, a graduate student at West Virginia University (WVU).

The astronomers suggest that there may be either two different mechanisms producing FRBs or that the objects producing them may act differently at different stages of their evolution. Leading candidates for the sources of FRBs are the super dense neutron stars left over after a massive star explodes as a supernova, or neutron stars with ultra-strong magnetic fields, called magnetars.

One characteristic of FRB 190520 calls into question the usefulness of FRBs as tools for studying the material between them and Earth. Astronomers often analyze the effects of intervening material on the radio waves emitted by distant objects to learn about that tenuous material itself. One such effect occurs when radio waves pass through space that contains free electrons. In that case, higher-frequency waves travel more quickly than lower-frequency waves.

This effect, called dispersion, can be measured to determine the density of electrons in the space between the object and Earth, or, if the electron density is known or assumed, provide a rough estimate of the distance to the object. The effect often is used to make distance estimates to pulsars.

That didn’t work for FRB 190520. An independent measurement of the distance based on the Doppler shift of the galaxy’s light caused by the expansion of the Universe placed the galaxy at nearly 3 billion light-years from Earth. However, the burst’s signal shows an amount of dispersion that ordinarily would indicate a distance of roughly 8 to 9.5 billion light-years.

“This means that there is a lot of material near the FRB that would confuse any attempt to use it to measure the gas between galaxies,” Aggarwal said. “If that’s the case with others, then we can’t count on using FRBs as cosmic yardsticks,” he added.

The astronomers speculated that FRB 190520 may be a “newborn,” still surrounded by dense material ejected by the supernova explosion that left behind the neutron star. As that material eventually dissipates, the dispersion of the burst signals also would decline. Under the “newborn” scenario, they said, the repeating bursts also might be a characteristic of younger FRBs and dwindle with age.

“The FRB field is moving very fast right now and new discoveries are coming out monthly. However, big questions still remain, and this object is giving us challenging clues about those questions,” said Sarah Burke-Spolaor, of WVU.

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Gaia detect ‘star quakes’

Newswand: The European Space Agency’s Gaia Mission has detected ‘star quakes’ – tiny motions on the surface of a star – that change the shapes of stars, something the observatory was not originally built for.

Photo credit: ESA

The details of the star quakes are included in the Gaia mission releases which takes place on June 13.

Gaia is ESA’s mission to create the most accurate and complete multi-dimensional map of the Milky Way. This allows astronomers to reconstruct our home galaxy’s structure and past evolution over billions of years, and to better understand the lifecycle of stars and our place in the Universe.

What’s new in data release 3?

Gaia’s data release 3 contains new and improved details for almost two billion stars in our galaxy. The catalogue includes new information including chemical compositions, stellar temperatures, colours, masses, ages, and the speed at which stars move towards or away from us (radial velocity).

Much of this information was revealed by the newly released spectroscopy data, a technique in which the starlight is split into its constituent colours (like a rainbow). The data also includes special subsets of stars, like those that change brightness over time.

Also new in this data set is the largest catalogue yet of binary stars, thousands of Solar System objects such as asteroids and moons of planets, and millions of galaxies and quasars outside the Milky Way.

Star quakes

One of the most surprising discoveries coming out of the new data is that Gaia is able to detect star quakes – tiny motions on the surface of a star – that change the shapes of stars, something the observatory was not originally built for.

Previously, Gaia already found radial oscillations that cause stars to swell and shrink periodically, while keeping their spherical shape. But Gaia has now also spotted other vibrations that are more like large-scale tsunamis. These nonradial oscillations change the global shape of a star and are therefore harder to detect.

Gaia found strong nonradial star quakes in thousands of stars. Gaia also revealed such vibrations in stars that have seldomly been seen before. These stars should not have any quakes according to the current theory, while Gaia did detect them at their surface.

“Star quakes teach us a lot about stars, notably their internal workings. Gaia is opening a goldmine for ‘asteroseismology’ of massive stars,” says Conny Aerts of KU Leuven in Belgium, who is a member of the Gaia collaboration.

The DNA of stars

What stars are made of can tell us about their birthplace and their journey afterwards, and therefore about the history of the Milky Way. With today’s data release, Gaia is revealing the largest chemical map of the galaxy coupled to 3D motions, from our solar neigbourhood to smaller galaxies surrounding ours.

Some stars contain more ‘heavy metals’ than others. During the Big Bang, only light elements were formed (hydrogen and helium). All other heavier elements – called metals by astronomers – are built inside stars. When stars die, they release these metals into the gas and dust between the stars called the interstellar medium, out of which new stars form. Active star formation and death will lead to an environment that is richer in metals. Therefore, a star’s chemical composition is a bit like its DNA, giving us crucial information about its origin.

With Gaia, we see that some stars in our galaxy are made of primordial material, while others like our Sun are made of matter enriched by previous generations of stars. Stars that are closer to the centre and plane of our galaxy are richer in metals than stars at larger distances. Gaia also identified stars that originally came from different galaxies than our own, based on their chemical composition.

“Our galaxy is a beautiful melting pot of stars,” says Alejandra Recio-Blanco of the Observatoire de la Côte d’Azur in France, who is a member of the Gaia collaboration.

“This diversity is extremely important, because it tells us the story of our galaxy’s formation. It reveals the processes of migration within our galaxy and accretion from external galaxies. It also clearly shows that our Sun, and we, all belong to an ever changing system, formed thanks to the assembly of stars and gas of different origins.”

Binary stars, asteroids, quasars, and more

Other papers that are published today reflect the breadth and depth of Gaia’s discovery potential. A new binary star catalogue presents the mass and evolution of more than 800 thousand binary systems, while a new asteroid survey comprising 156 thousand rocky bodies is digging deeper into the origin of our Solar System. Gaia is also revealing information about 10 million variable stars, mysterious macro-molecules between stars, as well as quasars and galaxies beyond our own cosmic neighbourhood.

“Unlike other missions that target specific objects, Gaia is a survey mission. This means that while surveying the entire sky with billions of stars multiple times, Gaia is bound to make discoveries that other more dedicated missions would miss. This is one of its strengths, and we can’t wait for the astronomy community to dive into our new data to find out even more about our galaxy and its surroundings than we could’ve imagined,” says Timo Prusti, Project Scientist for Gaia at ESA.

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Hubble spots drifting black hole for the first time

Newswand: NASA’s Hubble Space Telescope has, for the first time ever, provided direct evidence for a lone black hole drifting through interstellar space by a precise mass measurement of the phantom object.

Photo credit: NASA

Astronomers estimate that 100 million black holes roam among the stars in our Milky Way galaxy, but they have never conclusively identified an isolated black hole.

The newly detected wandering black hole lies about 5,000 light-years away, in the Carina-Sagittarius spiral arm of our galaxy. However, its discovery allows astronomers to estimate that the nearest isolated stellar-mass black hole to Earth might be as close as 80 light-years away. The nearest star to our solar system, Proxima Centauri, is a little over 4 light-years away.

Black holes roaming our galaxy are born from rare, monstrous stars (less than one-thousandth of the galaxy’s stellar population) that are at least 20 times more massive than our Sun. These stars explode as supernovae, and the remnant core is crushed by gravity into a black hole. Because the self-detonation is not perfectly symmetrical, the black hole may get a kick, and go careening through our galaxy like a blasted cannonball.

Telescopes can’t photograph a wayward black hole because it doesn’t emit any light. However, a black hole warps space, which then deflects and amplifies starlight from anything that momentarily lines up exactly behind it.

Ground-based telescopes, which monitor the brightness of millions of stars in the rich star fields toward the central bulge of our Milky Way, look for a tell-tale sudden brightening of one of them when a massive object passes between us and the star. Then Hubble follows up on the most interesting such events.

Two teams used Hubble data in their investigations – one led by Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland; and the other by Casey Lam of the University of California, Berkeley. The teams’ results differ slightly, but both suggest the presence of a compact object.

The warping of space due to the gravity of a foreground object passing in front of a star located far behind it will momentarily bend and amplify the light of the background star as it passes in front of it. Astronomers use the phenomenon, called gravitational microlensing, to study stars and exoplanets in the approximately 30,000 events seen so far inside our galaxy.

The signature of a foreground black hole stands out as unique among other microlensing events. The very intense gravity of the black hole will stretch out the duration of the lensing event for over 200 days. Also, if the intervening object was instead a foreground star, it would cause a transient color change in the starlight as measured because the light from the foreground and background stars would momentarily be blended together. But no color change was seen in the black hole event.

Next, Hubble was used to measure the amount of deflection of the background star’s image by the black hole. Hubble is capable of the extraordinary precision needed for such measurements. The star’s image was offset from where it normally would be by about a milliarc second. That’s equivalent to measuring the diameter of a 25-cent coin in Los Angeles as seen from New York City.

This astrometric microlensing technique provided information on the mass, distance, and velocity of the black hole. The amount of deflection by the black hole’s intense warping of space allowed Sahu’s team to estimate that it weighs seven solar masses.

Lam’s team reports a slightly lower mass range, meaning that the object may be either a neutron star or a black hole. They estimate that the mass of the invisible compact object is between 1.6 and 4.4 times that of the Sun. At the high end of this range the object would be a black hole; at the low end, it would be a neutron star.

Sahu’s team estimates the isolated black hole is traveling across the galaxy at 100,000 miles per hour, or 160,000 kilometers per hour (fast enough to travel from Earth to the Moon in less than three hours). That’s faster than most of the other neighboring stars in that region of our galaxy.

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Bacterial cellulose enables microbial life on Mars

Newswand: An international research team including the University of Göttingen has investigated the chances of survival of kombucha cultures under Mars-like conditions.

Kombucha is known as a drink, sometimes called tea fungus or mushroom tea, which is produced by fermenting sugared tea using kombucha cultures – a symbiotic culture of bacteria and yeast. Although the simulated Martian environment destroyed the microbial ecology of the kombucha cultures, surprisingly, a cellulose-producing bacterial species survived. The results were published in Frontiers in Microbiology.

The scientists of the “Biology and Mars Experiment” (BIOMEX) project had already sent kombucha cultures to the International Space Station (ISS) in 2014 with the support of the European Space Agency. The aim was to learn more about the robustness of cellulose as a biomarker, the genomic architecture of kombucha, and its survival behaviour under extraterrestrial conditions. After one and a half years under simulated Martian conditions outside the ISS, the samples were reactivated on Earth and cultivated for another two and a half years.

The head of the University of Göttingen’s Institute of Veterinary Medicine, Professor Bertram Brenig, was responsible for the sequencing and bioinformatic analysis of the metagenomes of the reactivated cultures and individual kombucha cultures in a team with researchers from the University of Minas Gerais in Brazil.

He said, “Based on our metagenomic analysis, we found that the simulated Martian environment drastically disrupted the microbial ecology of kombucha cultures. However, we were surprised to discover that the cellulose-producing bacteria of the genus Komagataeibacter survived.” The results suggest that the cellulose produced by the bacteria is probably responsible for their survival in extraterrestrial conditions. This also provides the first evidence that bacterial cellulose could be a biomarker for extraterrestrial life and cellulose-based membranes or films could be a good biomaterial for protecting life and producing consumer goods in extraterrestrial settlements.

Another interesting aspect of these experiments could be the development of novel drug delivery systems, for example for the development of medicine suitable for use in space. Another focus was on investigations into changes in antibiotic resistance: the research team was able to show that the total number of antibiotic and metal resistance genes – meaning that these microorganisms might survive despite antibiotics or metals in the environment – were enriched in the exposed cultures. “This result shows that the difficulties associated with antibiotic resistance in medicine in space should be given special attention in the future,” the scientists said.

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