Astronomers using NASA’s Hubble Space Telescope, and a trick of nature, have confirmed the existence of a planet orbiting two stars in the system OGLE-2007-BLG-349, located 8,000 light-years away towards the center of our galaxy.
The planet orbits roughly 300 million miles from the stellar duo, about the distance from the asteroid belt to our sun. It completes an orbit around both stars roughly every seven years. The two red dwarf stars are a mere 7 million miles apart, or 14 times the diameter of the moon’s orbit around Earth.
The Hubble observations represent the first time such a three-body system has been confirmed using the gravitational microlensing technique. Gravitational microlensing occurs when the gravity of a foreground star bends and amplifies the light of a background star that momentarily aligns with it. The particular character of the light magnification can reveal clues to the nature of the foreground star and any associated planets.
The three objects were discovered in 2007 by an international collaboration of five different groups: Microlensing Observations in Astrophysics (MOA), the Optical Gravitational Lensing Experiment (OGLE), the Microlensing Follow-up Network (MicroFUN), the Probing Lensing Anomalies Network (PLANET), and the Robonet Collaboration. These ground-based observations uncovered a star and a planet, but a detailed analysis also revealed a third body that astronomers could not definitively identify.
“The ground-based observations suggested two possible scenarios for the three-body system: a Saturn-mass planet orbiting a close binary star pair or a Saturn-mass and an Earth-mass planet orbiting a single star,” explained David Bennett of the NASA Goddard Space Flight Center in Greenbelt, Maryland, the paper’s first author.
The sharpness of the Hubble images allowed the research team to separate the background source star and the lensing star from their neighbors in the very crowded star field. The Hubble observations revealed that the starlight from the foreground lens system was too faint to be a single star, but it had the brightness expected for two closely orbiting red dwarf stars, which are fainter and less massive than our sun. “So, the model with two stars and one planet is the only one consistent with the Hubble data,” Bennett said.
Bennett’s team conducted the follow-up observations with Hubble’s Wide Field Planetary Camera 2. “We were helped in the analysis by the almost perfect alignment of the foreground binary stars with the background star, which greatly magnified the light and allowed us to see the signal of the two stars,” Bennett explained.
Kepler has discovered 10 other planets orbiting tight binary stars, but these are all much closer to their stars than the one studied by Hubble.
Now that the team has shown that microlensing can successfully detect planets orbiting double-star systems, Hubble could provide an essential role in this new realm in the continued search for exoplanets.
The team’s results have been accepted for publication in The Astronomical Journal.
International teams of astronomers have used the Atacama Large Millimeter/submillimeter Array (ALMA) to explore the distant corner of the Universe first revealed in the iconic images of the Hubble Ultra Deep Field (HUDF). These new ALMA observations are significantly deeper and sharper than previous surveys at millimetre wavelengths. They clearly show how the rate of star formation in young galaxies is closely related to their total mass in stars. They also trace the previously unknown abundance of star-forming gas at different points in time, providing new insights into the “Golden Age” of galaxy formation approximately 10 billion years ago.
The new ALMA results will be published in a series of papers appearing in the Astrophysical Journal and Monthly Notices of the Royal Astronomical Society. These results are also among those being presented this week at the Half a Decade of ALMA conference in Palm Springs, California, USA.
In 2004 the Hubble Ultra Deep Field images — pioneering deep-field observations with the NASA/ESA Hubble Space Telescope — were published. These spectacular pictures probed more deeply than ever before and revealed a menagerie of galaxies stretching back to less than a billion years after the Big Bang. The area was observed several times by Hubble and many other telescopes, resulting in the deepest view of the Universe to date.
Astronomers using ALMA have now surveyed this seemingly unremarkable, but heavily studied, window into the distant Universe for the first time both deeply and sharply in the millimetre range of wavelengths . This allows them to see the faint glow from gas clouds and also the emission from warm dust in galaxies in the early Universe.
ALMA has observed the HUDF for a total of around 50 hours up to now. This is the largest amount of ALMA observing time spent on one area of the sky so far.
One team led by Jim Dunlop (University of Edinburgh, United Kingdom) used ALMA to obtain the first deep, homogeneous ALMA image of a region as large as the HUDF. This data allowed them to clearly match up the galaxies that they detected with objects already seen with Hubble and other facilities.
This study showed clearly for the first time that the stellar mass of a galaxy is the best predictor of star formation rate in the high redshift Universe. They detected essentially all of the high-mass galaxies  and virtually nothing else.
Jim Dunlop, lead author on the deep imaging paper sums up its importance: “This is a breakthrough result. For the first time we are properly connecting the visible and ultraviolet light view of the distant Universe from Hubble and far-infrared/millimetre views of the Universe from ALMA.”
The second team, led by Manuel Aravena of the Núcleo de Astronomía, Universidad Diego Portales, Santiago, Chile, and Fabian Walter of the Max Planck Institute for Astronomy in Heidelberg, Germany, conducted a deeper search across about one sixth of the total HUDF .
“We conducted the first fully blind, three-dimensional search for cool gas in the early Universe,” said Chris Carilli, an astronomer with the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, USA and member of the research team. “Through this, we discovered a population of galaxies that is not clearly evident in any other deep surveys of the sky.” 
Some of the new ALMA observations were specifically tailored to detect galaxies that are rich in carbon monoxide, indicating regions primed for star formation. Even though these molecular gas reservoirs give rise to the star formation activity in galaxies, they are often very hard to see with Hubble. ALMA can therefore reveal the “missing half” of the galaxy formation and evolution process.
“The new ALMA results imply a rapidly rising gas content in galaxies as we look back further in time,” adds lead author of two of the papers, Manuel Aravena (Núcleo de Astronomía, Universidad Diego Portales, Santiago, Chile). “This increasing gas content is likely the root cause for the remarkable increase in star formation rates during the peak epoch of galaxy formation, some 10 billion years ago.”
The results presented today are just the start of a series of future observations to probe the distant Universe with ALMA. For example, a planned 150-hour observing campaign of the HUDF will further illuminate the star-forming potential history of the Universe.
“By supplementing our understanding of this missing star-forming material, the forthcoming ALMA Large Program will complete our view of the galaxies in the iconic Hubble Ultra Deep Field,” concludes Fabian Walter.
 Astronomers specifically selected the area of study in the HUDF, a region of space in the faint southern constellation ofFornax (The Furnace), so ground-based telescopes in the southern hemisphere, like ALMA, could probe the region, expanding our knowledge about the very distant Universe.
Probing the deep, but optically invisible, Universe was one of the primary science goals for ALMA.
 In this context “high mass” means galaxies with stellar masses greater than 20 billion times that of the Sun ( 2 × 1010solar masses). For comparison, the Milky Way is a large galaxy and has a mass of around 100 billion solar masses.
 This region of sky is about seven hundred times smaller than the area of the disc of the full Moon as seen from Earth. One of the most startling aspects of the HUDF was the vast number of galaxies found in such a tiny fraction of the sky.
 ALMA’s ability to see a completely different portion of the electromagnetic spectrum from Hubble allows astronomers to study a different class of astronomical objects, such as massive star-forming clouds, as well as objects that are otherwise too faint to observe in visible light, but visible at millimetre wavelengths.
The search is referred to as “blind” as it was not focussed on any particular object.
The new ALMA observations of the HUDF include two distinct, yet complementary types of data: continuum observations, which reveal dust emission and star formation, and a spectral emission line survey, which looks at the cold molecular gas fueling star formation. The second survey is particularly valuable because it includes information about the degree to which light from distant objects has been redshifted by the expansion of the Universe. Greater redshift means that an object is further away and seen farther back in time. This allows astronomers to create a three-dimensional map of star-forming gas as it evolves over cosmic time.
The dusty disk surrounding the star TW Hydrae exhibits circular features that may signal the formation of protoplanets. LMU astrophysicist Barbara Ercolano argues, however, that the innermost actually points to the impending dispersal of the disk.
When the maps appeared at the end of March, experts were electrified. The images revealed an orange-red disk pitted with circular gaps that looked like the grooves in an old-fashioned long-playing record. But this was no throwback to the psychedelic Sixties. It was a detailed portrait of a so-called protoplanetary disk, made up of gas and dust grains, associated with a young star – the kind of structure out of which planets could be expected to form. Not only that, the maps showed that the disk around the star known as TW Hydrae exhibits several clearly defined gaps. Astronomers speculated that these gaps might indicate the presence of protoplanets, which had pushed away the material along their orbital paths. And to make the story even more seductive, one prominent gap is located at approximately the same distance from TW Hydrae as Earth is from the Sun – raising the possibility that this putative exoplanet could be an Earth-like one.
Now an international team led by Professor Barbara Ercolano at LMU’s Astronomical Observatory has compared the new observations with theoretical models of planet formation. The study indicates that the prominent gap in the TW Hydrae system is unlikely to be due to the action of an actively accreting protoplanet. Instead, the team attributes the feature to a process known as photoevaporation. Photoevaporation occurs when the intense radiation emitted by the parent star heats the gas, allowing it to fly away from the disk. But although hopes of a new exo-Earth orbiting in the inner gap of TW Hydrae may themselves have evaporated, the system nevertheless provides the opportunity to observe the dissipation of a circumstellar disk in unprecedented detail. The new findings appear in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).
Only 175 light-years from Earth
The dusty disk that girdles TW Hydrae has long been a favored object of observation. The star lies only 175 light-years from Earth, and is it relatively young (around 106 years old). Moreover, the disk is oriented almost perpendicular to our line of sight, affording a well-nigh ideal view of its structure. The spectacular images released in March were made with the Atacama Large Millimeter/submillimeter Array (ALMA), an array of detectors in the desert of Northern Chile. Together, they form a radiotelescope with unparalleled resolving power that can detect the radiation from dust grains in the millimeter size range.
Photoevaporation is one of the major forces that shape the fate of circumstellar disks. Not only can it destroy such disks –which typically have a life expectancy of around 10 million years — it can also stop young planets being drawn by gravity and by the interaction with the surrounding disc gas into their parent star. The gaps caused by the action of photoevaporation on the disk, park the planets at their location by removing the gas, allowing the small dusty clumps to grow into fully fledged planets and steering them into stable orbits. However, in the case of the TW Hydrae system, Barbara Ercolano believes that the inner gap revealed by the ALMA maps is not caused by a planet, but represents an early stage in the dissipation of the disk. This view is based on the fact that many characteristic features of the disk around TW Hydrae, such as the distance between the gap and the star, the overall mass accretion rate, and the size and density distributions of the particles, are in very good agreement with the predictions of her photoevaporation model.
The puzzling appearance of an ice cloud seemingly out of thin air has prompted NASA scientists to suggest that a different process than previously thought — possibly similar to one seen over Earth’s poles — could be forming clouds on Saturn’s moon Titan.
Located in Titan’s stratosphere, the cloud is made of a compound of carbon and nitrogen known as dicyanoacetylene (C4N2), an ingredient in the chemical cocktail that colors the giant moon’s hazy, brownish-orange atmosphere.
Decades ago, the infrared instrument on NASA’s Voyager 1 spacecraft spotted an ice cloud just like this one on Titan. What has puzzled scientists ever since is this: they detected less than 1 percent of the dicyanoacetylene gas needed for the cloud to condense.
Recent observations from NASA’s Cassini mission yielded a similar result. Using Cassini’s composite infrared spectrometer, or CIRS — which can identify the spectral fingerprints of individual chemicals in the atmospheric brew — researchers found a large, high-altitude cloud made of the same frozen chemical. Yet, just as Voyager found, when it comes to the vapor form of this chemical, CIRS reported that Titan’s stratosphere is as dry as a desert.
“The appearance of this ice cloud goes against everything we know about the way clouds form on Titan,” said Carrie Anderson, a CIRS co-investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study.
The typical process for forming clouds involves condensation. On Earth, we’re familiar with the cycle of evaporation and condensation of water. The same kind of cycle takes place in Titan’s troposphere — the weather-forming layer of Titan’s atmosphere — but with methane instead of water.
A different condensation process takes place in the stratosphere — the region above the troposphere — at Titan’s north and south winter poles. In this case, layers of clouds condense as the global circulation pattern forces warm gases downward at the pole. The gases then condense as they sink through cooler and cooler layers of the polar stratosphere.
Either way, a cloud forms when the air temperature and pressure are favorable for the vapor to condense into ice. The vapor and the ice reach a balance point — an equilibrium — that is determined by the air temperature and pressure. Because of this equilibrium, scientists can calculate the amount of vapor where ice is present.
“For clouds that condense, this equilibrium is mandatory, like the law of gravity,” said Robert Samuelson, an emeritus scientist at Goddard and a co-author of the paper.
But the numbers don’t compute for the cloud made from dicyanoacetylene. The scientists determined that they would need at least 100 times more vapor to form an ice cloud where the cloud top was observed by Cassini’s CIRS.
One explanation suggested early on was that the vapor might be present, but Voyager’s instrument wasn’t sensitive enough in the critical wavelength range needed to detect it. But when CIRS also didn’t find the vapor, Anderson and her Goddard and Caltech colleagues proposed an altogether different explanation. Instead of the cloud forming by condensation, they think the C4N2 ice forms because of reactions taking place on other kinds of ice particles. The researchers call this “solid-state chemistry,” because the reactions involve the ice, or solid, form of the chemical.
The first step in the proposed process is the formation of ice particles made from the related chemical cyanoacetylene (HC3N). As these tiny bits of ice move downward through Titan’s stratosphere, they get coated by hydrogen cyanide (HCN). At this stage, the ice particle has a core and a shell comprised of two different chemicals. Occasionally, a photon of ultraviolet light tunnels into the frozen shell and triggers a series of chemical reactions in the ice. These reactions could begin either in the core or within the shell. Both pathways can yield dicyanoacteylene ice and hydrogen as products.
The researchers got the idea of solid-state chemistry from the formation of clouds involved in ozone depletion high above Earth’s poles. Although Earth’s stratosphere has scant moisture, wispy nacreous clouds (also called polar stratospheric clouds) can form under the right conditions. In these clouds, chlorine-bearing chemicals that have entered the atmosphere as pollution stick to crystals of water ice, resulting in chemical reactions that release ozone-destroying chlorine molecules.
“It’s very exciting to think that we may have found examples of similar solid-state chemical processes on both Titan and Earth,” said Anderson.
The researchers suggest that, on Titan, the reactions occur inside the ice particles, sequestered from the atmosphere. In that case, dicyanoacetylene ice wouldn’t make direct contact with the atmosphere, which would explain why the ice and the vapor forms are not in the expected equilibrium.
“The compositions of the polar stratospheres of Titan and Earth could not differ more,” said Michael Flasar, CIRS principal investigator at Goddard. “It is amazing to see how well the underlying physics of both atmospheres has led to analogous cloud chemistry.”
Research led by Johns Hopkins University astrophysicists using information from a NASA space telescope breaks new ground in ways to observe a star swallowed by a black hole, promising to help paint a clearer picture of this cosmic phenomenon.
The results, published online in the Astrophysical Journal, are based on two methods that are new in the study of this sort of star destruction: the first infrared observations, and using galaxy dust to reflect, or “echo,” the electromagnetic energy burst of a star being devoured by a black hole, called a “tidal disruption flare.”
The approach, which in this case allowed scientists to measure flare energy more precisely than had been done before, offers fresh ways to understand “tidal disruptions.” The phenomena were first raised hypothetically in the 1970s, and only studied closely since 2005, although the first possible examples were claimed several years earlier, said Julian H. Krolik, a professor in the Department of Physics and Astronomy at Johns Hopkins and one of four authors of the paper.
“What happens to the mass of the star once it’s torn apart?” Krolik said. “Is it heated up? Does it go quickly into the black hole? Does it swirl around for a while? These are the questions” that this approach could help to answer, Krolik said. He co-wrote the paper with lead author Sjoert van Velzen, a Hubble Fellow at Johns Hopkins; Alexander J. Mendez, who was a post-doctoral fellow at the university when the work was done; and Varoujan Gorjian, an astronomer at NASA’s Jet Propulsion Laboratory, a division of Caltech.
The four scientists used images that had been compiled by the Wide-field Infrared Survey Explorer (WISE) telescope, which NASA launched into Earth’s orbit in 2009. The study considered five instances in which a star had apparently moved close enough to the gravitational pull of a black hole to be drawn in, have its mass stretched and compressed into long strands, and be devoured — a “tidal disruption.”
The events — each of which can unfold over a period of months — occurred in five galaxies, the closest of which is 840 million light years from Earth.
In each case, the destruction of the star set off a burst of energy, or flare. Krolik said it’s been generally expected that the flares would emit most of their energy in low-energy X-rays or extreme ultraviolet light, but these bands are very difficult to observe. For that reason, most observations have been in visible or near ultraviolet light.
This research relied on indirect observation of the flare. The scientists compiled information gathered by the telescope on the temperature of the dust roughly 2 trillion miles away from where the stars were destroyed by the black holes. The intense radiation of the flare first burns away the dust, cleaning out a sphere with a radius of about 2 trillion miles. At the edge of this sphere, dust absorbs and then re-emits the heat from the tidal disruption flare, creating a thermal “echo” picked up by the telescope.
“The dust echo thus provides a unique means to measure total energy that is emitted during the stars’ destruction,” van Velzen said. “A measurement of the total energy is very important; without this we have an incomplete picture of what happens during a stellar tidal disruption. For example, the total energy is needed to understand if the star got fully destroyed, or if the black hole only nibbled a piece of the star.”
The study refined the understanding of the energy produced by these flares. The flare energy was measured at 10 times more than previous observations saw, but one tenth the energy predicted in the earliest, most simple models.
That point is part of an emerging understanding of a cosmic event that has only been observed a few dozen times. The picture is bound to become clearer as researchers develop new methods, including the first infrared observations.
“In astronomy, opening a ‘new wavelength regime’ is often reason to celebrate,” van Velzen said.
The research says “there’s value in the use of infrared telescopes in looking for these echoes,” added Krolik. “We expect to do more.”
With funding from The Kavli Foundation, the think tank will bring together some of the major researchers in exoplanetary science – arguably the most exciting field in modern astronomy – for a series of annual meetings to address the biggest questions in this field which humanity could conceivably answer in the next decade.
“We’re really at the frontier in exoplanet research,” said Dr Nikku Madhusudhan of Cambridge’s Institute of Astronomy, who is leading the think tank. “The pace of new discoveries is incredible – it really feels like anything can be discovered any moment in our exploration of extra-terrestrial worlds. By bringing together some of the best minds in this field we aim to consolidate our collective wisdom and address the biggest questions in this field that humanity can ask and answer at this time.”
Tremendous advances have been made in the study of exoplanets since the first such planet was discovered around a sun-like star in 1995 by the Cavendish Laboratory’s Professor Didier Queloz. Just last month, a potentially habitable world was discovered in our own neighbourhood, orbiting Proxima Centauri, the nearest star to the sun.
However, there are still plenty questions to be answered, such as whether we’re capable of detecting signatures of life on other planets within the next ten years, what the best strategies are to find habitable planets, how diverse are planets and their atmospheres, and how planets form in the first place.
With at least four space missions and numerous large ground-based facilities scheduled to become operational in the next decade, exoplanetary scientists will be able to detect more and more exoplanets, and will also have the ability to conduct detailed studies of their atmospheres, interiors, and formation conditions. At the same time, major developments are expected in all aspects of exoplanetary theory and data interpretation.
In order to make these major advances in the field, new interdisciplinary approaches are required. Additionally, as new scientific questions and areas emerge at an increasingly fast pace, there is a need for a focused forum where emerging questions in frontier areas of the field can be discussed. “Given the exciting advancements in exoplanetary science now is the right time to assess the state of the field and the scientific challenges and opportunities on the horizon,” said Professor Andy Fabian, director of the Institute of Astronomy at Cambridge.
The think tank will operate in the form of a yearly Exoplanet Symposium series which will be focused on addressing pressing questions in exoplanetary science. One emerging area or theme in exoplanetary science will be chosen each year based on its critical importance to the advancement of the field, relevance to existing or imminent observational facilities, need for an interdisciplinary approach, and/or scope for fundamental breakthroughs.
About 30 experts in the field from around the world will discuss outstanding questions, new pathways, interdisciplinary synergies, and strategic actions that could benefit the exoplanet research community.
The inaugural symposium, “Kavli ExoFrontiers 2016”, is being held this week in Cambridge. The goal of this first symposium is to bring together experts from different areas of exoplanetary science to share their visions about the most pressing questions and future outlook of their respective areas. These visions will help provide both a broad outlook of the field and identify the ten most important questions in the field that could be addressed within the next decade. “We hope the think tank will provide a platform for new breakthroughs in the field through interdisciplinary and international efforts while bringing the most important scientific questions of our time to the fore,” said Madhusudhan. “We are in the golden age of exoplanetary science.”
Ingredients regarded as crucial for the origin of life on Earth have been discovered at the comet that ESA’s Rosetta spacecraft has been probing for almost two years.
They include the amino acid glycine, which is commonly found in proteins, and phosphorus, a key component of DNA and cell membranes.
Scientists have long debated the important possibility that water and organic molecules were brought by asteroids and comets to the young Earth after it cooled following its formation, providing some of the key building blocks for the emergence of life.
While some comets and asteroids are already known to have water with a composition like that of Earth’s oceans, Rosetta found a significant difference at its comet – fuelling the debate on their role in the origin of Earth’s water.
But new results reveal that comets nevertheless had the potential to deliver ingredients critical to establish life as we know it.
Amino acids are biologically important organic compounds containing carbon, oxygen, hydrogen and nitrogen, and form the basis of proteins.
Hints of the simplest amino acid, glycine, were found in samples returned to Earth in 2006 from Comet Wild-2 by NASA’s Stardust mission. However, possible terrestrial contamination of the dust samples made the analysis extremely difficult.
Now, Rosetta has made direct, repeated detections of glycine in the fuzzy atmosphere or ‘coma’ of its comet.
“This is the first unambiguous detection of glycine at a comet,” says Kathrin Altwegg, principal investigator of the ROSINA instrument that made the measurements, and lead author of the paper published in Science Advances today.
“At the same time, we also detected certain other organic molecules that can be precursors to glycine, hinting at the possible ways in which it may have formed.”
The measurements were made before the comet reached its closest point to the Sun – perihelion – in August 2015 in its 6.5 year orbit.
The first detection was made in October 2014 while Rosetta was just 10 km from the comet. The next occasion was during a flyby in March 2015, when it was 30–15 km from the nucleus.
Glycine was also seen on other occasions associated with outbursts from the comet in the month leading up to perihelion, when Rosetta was more than 200 km from the nucleus but surrounded by a lot of dust.
“We see a strong link between glycine and dust, suggesting that it is probably released perhaps with other volatiles from the icy mantles of the dust grains once they have warmed up in the coma,” says Kathrin.
Glycine turns into gas only when it reaches temperatures just below 150°C, meaning that usually little is released from the comet’s surface or subsurface because of the low temperatures. This accounts for the fact that Rosetta does not always detect it.
“Glycine is the only amino acid that is known to be able to form without liquid water, and the fact we see it with the precursor molecules and dust suggests it is formed within interstellar icy dust grains or by the ultraviolet irradiation of ice, before becoming bound up and conserved in the comet for billions of years,” adds Kathrin.
Another exciting detection made by Rosetta and described in the paper is of phosphorus, a key element in all known living organisms. For example, it is found in the structural framework of DNA and in cell membranes, and it is used in transporting chemical energy within cells for metabolism.
“There is still a lot of uncertainty regarding the chemistry on early Earth and there is of course a huge evolutionary gap to fill between the delivery of these ingredients via cometary impacts and life taking hold,” says co-author Hervé Cottin.
“But the important point is that comets have not really changed in 4.5 billion years: they grant us direct access to some of the ingredients that likely ended up in the prebiotic soup that eventually resulted in the origin of life on Earth.”
“The multitude of organic molecules already identified by Rosetta, now joined by the exciting confirmation of fundamental ingredients like glycine and phosphorous, confirms our idea that comets have the potential to deliver key molecules for prebiotic chemistry,” says Matt Taylor, ESA’s Rosetta project scientist.
“Demonstrating that comets are reservoirs of primitive material in the Solar System and vessels that could have transported these vital ingredients to Earth, is one of the key goals of the Rosetta mission, and we are delighted with this result.”