Water Detected On An Exoplanet Located In Its Star’s Habitable Zone

 

 

Ever since the discovery of the first exoplanet in the 1990s, astronomers have made steady progress towards finding and probing planets located in the habitable zone of their stars, where conditions can lead to the formation of liquid water and the proliferation of life.

Results from the Kepler satellite mission, which discovered nearly 2/3 of all known exoplanets to date, indicate that 5 to 20% of Earths and super-Earths are located in the habitable zone of their stars. However, despite this abundance, probing the conditions and atmospheric properties on any of these habitable zone planets is extremely difficult and has remained elusive… until now.

A new study by Professor Björn Benneke of the Institute for Research on Exoplanets at the Université de Montréal, his doctoral student Caroline Piaulet and several of their collaborators reports the detection of water vapour and perhaps even liquid water clouds in the atmosphere of the planet K2-18b. This exoplanet is about nine times more massive than our Earth and is found in the habitable zone of the star it orbits. This M-type star is smaller and cooler than our Sun, but due to K2-18b’s close proximity to its star, the planet receives almost the same total amount of energy from its star as our Earth receives from the Sun.

The similarities between the exoplanet K2-18b and the Earth suggest to astronomers that the exoplanet may potentially have a water cycle possibly allowing water to condense into clouds and liquid water rain to fall. This detection was made possible by combining eight transit observations — the moment when an exoplanet passes in front of its star — taken by the Hubble Space Telescope.

The Université de Montréal is no stranger to the K2-18 system located 111 light years away. The existence of K2-18b was first confirmed by Prof. Benneke and his team in a 2016 paper using data from the Spitzer Space Telescope. The mass and radius of the planet were then determined by former Université de Montréal and University of Toronto PhD student Ryan Cloutier. These promising initial results encouraged the iREx team to collect follow-up observations of the intriguing world.”

Scientists currently believe that the thick gaseous envelope of K2-18b likely prevents life as we know it from existing on the planet’s surface. However, the study shows that even these planets of relatively low mass which are therefore more difficult to study can be explored using astronomical instruments developed in recent years. By studying these planets which are in the habitable zone of their star and have the right conditions for liquid water, astronomers are one step closer to directly detecting signs of life beyond our Solar System.

“This represents the biggest step yet taken towards our ultimate goal of finding life on other planets, of proving that we are not alone. Thanks to our observations and our climate model of this planet, we have shown that its water vapour can condense into liquid water. This is a first,” says Björn Benneke.

 

Scientists Detect The Ringing Of A Newborn Black Hole For The First Time

 

Now, physicists from MIT and elsewhere have “heard” the ringing of an infant black hole for the first time, and found that the pattern of this ringing does, in fact, predict the black hole’s mass and spin — more evidence that Einstein was right all along.

The findings, published today in Physical Review Letters, also favor the idea that black holes lack any sort of “hair” — a metaphor referring to the idea that black holes, according to Einstein’s theory, should exhibit just three observable properties: mass, spin, and electric charge. All other characteristics, which the physicist John Wheeler termed “hair,” should be swallowed up by the black hole itself, and would therefore be unobservable.

The team’s findings today support the idea that black holes are, in fact, hairless. The researchers were able to identify the pattern of a black hole’s ringing, and, using Einstein’s equations, calculated the mass and spin that the black hole should have, given its ringing pattern. These calculations matched measurements of the black hole’s mass and spin made previously by others.

If the team’s calculations deviated significantly from the measurements, it would have suggested that the black hole’s ringing encodes properties other than mass, spin, and electric charge — tantalizing evidence of physics beyond what Einstein’s theory can explain. But as it turns out, the black hole’s ringing pattern is a direct signature of its mass and spin, giving support to the notion that black holes are bald-faced giants, lacking any extraneous, hair-like properties.

“We all expect general relativity to be correct, but this is the first time we have confirmed it in this way,” says the study’s lead author, Maximiliano Isi, a NASA Einstein Fellow in MIT’s Kavli Institute for Astrophysics and Space Research. “This is the first experimental measurement that succeeds in directly testing the no-hair theorem. It doesn’t mean black holes couldn’t have hair. It means the picture of black holes with no hair lives for one more day.”

A chirp, decoded

On Sept. 9, 2015, scientists made the first-ever detection of gravitational waves — infinitesimal ripples in space-time, emanating from distant, violent cosmic phenomena. The detection, named GW150914, was made by LIGO, the Laser Interferometer Gravitational-wave Observatory. Once scientists cleared away the noise and zoomed in on the signal, they observed a waveform that quickly crescendoed before fading away. When they translated the signal into sound, they heard something resembling a “chirp.”

Scientists determined that the gravitational waves were set off by the rapid inspiraling of two massive black holes. The peak of the signal — the loudest part of the chirp — linked to the very moment when the black holes collided, merging into a single, new black hole. While this infant black hole likely gave off gravitational waves of its own, its signature ringing, physicists assumed, would be too faint to decipher amid the clamor of the initial collision.

Isi and his colleagues, however, found a way to extract the black hole’s reverberation from the moments immediately after the signal’s peak. In previous work led by Isi’s co-author, Matthew Giesler, the team showed through simulations that such a signal, and particularly the portion right after the peak, contains “overtones” — a family of loud, short-lived tones. When they reanalyzed the signal, taking overtones into account, the researchers discovered that they could successfully isolate a ringing pattern that was specific to a newly formed black hole.

In the team’s new paper, the researchers applied this technique to actual data from the GW150914 detection, concentrating on the last few milliseconds of the signal, immediately following the chirp’s peak. Taking into account the signal’s overtones, they were able to discern a ringing coming from the new, infant black hole. Specifically, they identified two distinct tones, each with a pitch and decay rate that they were able to measure.

“We detect an overall gravitational wave signal that’s made up of multiple frequencies, which fade away at different rates, like the different pitches that make up a sound,” Isi says. “Each frequency or tone corresponds to a vibrational frequency of the new black hole.”

Listening beyond Einstein

Einstein’s theory of general relativity predicts that the pitch and decay of a black hole’s gravitational waves should be a direct product of its mass and spin. That is, a black hole of a given mass and spin can only produce tones of a certain pitch and decay. As a test of Einstein’s theory, the team used the equations of general relativity to calculate the newly formed black hole’s mass and spin, given the pitch and decay of the two tones they detected.

They found their calculations matched with measurements of the black hole’s mass and spin previously made by others. Isi says the results demonstrate that researchers can, in fact, use the very loudest, most detectable parts of a gravitational wave signal to discern a new black hole’s ringing, where before, scientists assumed that this ringing could only be detected within the much fainter end of the gravitational wave signal, and only with much more sensitive instruments than what currently exist.

“This is exciting for the community because it shows these kinds of studies are possible now, not in 20 years,” Isi says.

As LIGO improves its resolution, and more sensitive instruments come online in the future, researchers will be able to use the group’s methods to “hear” the ringing of other newly born black holes. And if they happen to pick up tones that don’t quite match up with Einstein’s predictions, that could be an even more exciting prospect.

“In the future, we’ll have better detectors on Earth and in space, and will be able to see not just two, but tens of modes, and pin down their properties precisely,” Isi says. “If these are not black holes as Einstein predicts, if they are more exotic objects like wormholes or boson stars, they may not ring in the same way, and we’ll have a chance of seeing them.”

This research was supported, in part, by NASA, the Sherman Fairchild Foundation, the Simons Foundation, and the National Science Foundation.

Evidence Found For Cloaked Black Hole In Early Universe

A group of astronomers, including Penn State scientists, has announced the likely discovery of a highly obscured black hole existing only 850 million years after the Big Bang, using NASA’s Chandra X-ray Observatory. This is the first evidence for a cloaked black hole at such an early time.

Supermassive black holes typically grow by pulling in material from a disk of surrounding matter. For the most rapid growth, this process generates prodigious amounts of radiation in a very small region around the black hole, and produces an extremely bright, compact source called a quasar.

Theoretical calculations indicate that most of the early growth of black holes occurs while the black hole and disk are surrounded by a dense cloud of gas that feeds material into the disk. As the black hole grows, the gas in the cloud is depleted until the black hole and its bright disk are uncovered.

“It’s extraordinarily challenging to find quasars in this cloaked phase because so much of their radiation is absorbed and cannot be detected by current instruments,” said Fabio Vito, CAS-CONICYT Fellow at the Pontificia Universidad Católica de Chile, who led the study, which he started as a postdoctoral researcher at Penn State. “Thanks to Chandra and the ability of X-rays to pierce through the obscuring cloud, we think we’ve finally succeeded.”

The discovery resulted from observations of a quasar called PSO 167-13, which was first discovered by Pan-STARRS, an optical-light telescope in Hawaii. Optical observations from these and other surveys have resulted in the detection of about 200 quasars already shining brightly when the universe was less than a billion years old, or about 8 percent of its present age. These surveys were only considered effective at finding unobscured black holes, because the radiation they detect is suppressed by even thin clouds of surrounding gas and dust. Therefore PSO 167-13 was expected to be unobscured.

Vito’s team were able to test this idea by making Chandra observations of PSO 167-13 and nine other quasars discovered with optical surveys. After 16 hours of observation only three X-ray photons were detected from PSO 167-13, all with relatively high energies. Low energy X-rays are more readily absorbed than higher energy ones, so the likely explanation for the Chandra observation is that the quasar is highly obscured by gas, allowing only high energy X-rays to be detected.

“This was a complete surprise,” said co-author Niel Brandt, Verne M. Willaman Professor of Astronomy and Astrophysics and professor of physics at Penn State. “It was like we were expecting a moth but saw a cocoon instead. None of the other nine quasars we observed were cloaked, which is what we anticipated.”

An interesting twist for PSO 167-13 is that the galaxy hosting the quasar has a close companion galaxy visible in data previously obtained with the Atacama Large Millimeter Array (ALMA) of radio dishes in Chile and NASA’s Hubble Space Telescope. Because of their close separation and the faintness of the X-ray source, the team was unable to determine whether the newly-discovered X-ray emission is associated with the quasar PSO 167-13 or with the companion galaxy.

If the X-rays come from the known quasar, then astronomers need to develop an explanation for why the quasar appeared highly obscured in X-rays but not in optical light. One possibility is that there has been a large and rapid increase in obscuration of the quasar during the 3 years between when the optical and the X-ray observations were made.

On the other hand, if instead the X-rays arise from the companion galaxy, then it represents the detection of a new quasar in close proximity to PSO 167-13. This quasar pair would be the most distant yet detected, breaking the record of 1.2 billion years after the Big Bang. In either of these two cases, the quasar detected by Chandra would be the most distant cloaked one yet seen. The previous record holder is observed 1.3 billion years after the Big Bang. The authors plan to make a more refined characterization of the source with follow-up observations.

“With a longer Chandra observation, we’ll be able to get a better estimate of how obscured this black hole is,” said co-author Franz Bauer, also from the Pontificia Universidad Católica de Chile and a former Penn State postdoctoral researcher, “and make a confident identification of the X-ray source with either the known quasar or the companion galaxy.”

The authors also plan to search for more examples of highly obscured black holes.

“We suspect that the majority of supermassive black holes in the early universe are cloaked: it’s then crucial to detect and study them to understand how they could grow to masses of a billion suns so quickly,” said co-author Roberto Gilli of INAF in Bologna, Italy.

A paper describing these results appears online August 8 in the journal Astronomy & Astrophysics. NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science and flight operations from Cambridge, MA. The data utilized in this research were gathered using the Advanced CCD Imaging Spectrometer on Chandra, an instrument conceived and designed by a team led by Penn State Evan Pugh Professor Emeritus of Astronomy and Astrophysics Gordon Garmire.

In addition to Vito, Brandt, and Bauer, the research team also includes former Penn State postdoctoral researchers Ohad Shemmer, Cristian Vignali, and Bin Luo, who also earned his doctoral degree at Penn State.

Astronomers Discover Vast Ancient Galaxies, Which Could Shed Light On Dark Matter

Astronomers used the combined power of multiple astronomical observatories around the world and in space to discover a treasure-trove of previously unknown ancient massive galaxies. This is the first multiple discovery of its kind and such an abundance of this type of galaxy defies current models of the universe. These galaxies are also intimately connected with supermassive black holes and the distribution of dark matter.

The Hubble Space Telescope gave us unprecedented access to the previously unseen universe, but even it is blind to some of the most fundamental pieces of the cosmic puzzle. Astronomers from the Institute of Astronomy at the University of Tokyo wanted to see some things they long suspected may be out there but which Hubble could not show them. Newer generations of astronomical observatories have finally revealed what they sought.

“This is the first time that such a large population of massive galaxies was confirmed during the first 2 billion years of the 13.7-billion-year life of the universe. These were previously invisible to us,” said researcher Tao Wang. “This finding contravenes current models for that period of cosmic evolution and will help to add some details, which have been missing until now.”

But how can something as big as a galaxy be invisible to begin with?

“The light from these galaxies is very faint with long wavelengths invisible to our eyes and undetectable by Hubble,” explained Professor Kotaro Kohno. “So we turned to the Atacama Large Millimeter/submillimeter Array (ALMA), which is ideal for viewing these kinds of things. I have a long history with that facility and so knew it would deliver good results.”

Even though these galaxies were the largest of their time, the light from them is not only weak but also stretched due to their immense distance. As the universe expands, light passing through becomes stretched, so visible light becomes longer, eventually becoming infrared. The amount of stretching allows astronomers to calculate how far away something is, which also tells you how long ago the light you’re seeing was emitted from the thing in question.

“It was tough to convince our peers these galaxies were as old as we suspected them to be. Our initial suspicions about their existence came from the Spitzer Space Telescope’s infrared data,” continued Wang. “But ALMA has sharp eyes and revealed details at submillimeter wavelengths, the best wavelength to peer through dust present in the early universe. Even so, it took further data from the imaginatively named Very Large Telescope in Chile to really prove we were seeing ancient massive galaxies where none had been seen before.”

Another reason these galaxies appear so weak is because larger galaxies, even in the present day, tend to be shrouded in dust, which obscures them more than their smaller galactic siblings.

And what does the discovery of these massive galaxies imply?

“The more massive a galaxy, the more massive the supermassive black hole at its heart. So the study of these galaxies and their evolution will tell us more about the evolution of supermassive black holes, too,” said Kohno. “Massive galaxies are also intimately connected with the distribution of invisible dark matter. This plays a role in shaping the structure and distribution of galaxies. Theoretical researchers will need to update their theories now.”

What’s also interesting is how these 39 galaxies are different from our own. If our solar system were inside one of them and you were to look up at the sky on a clear night, you would see something quite different to the familiar pattern of the Milky Way.

“For one thing, the night sky would appear far more majestic. The greater density of stars means there would be many more stars close by appearing larger and brighter,” explained Wang. “But conversely, the large amount of dust means farther-away stars would be far less visible, so the background to these bright close stars might be a vast dark void.”

As this is the first time such a population of galaxies has been discovered, the implications of their study are only now being realized. There may be many surprises yet to come.

“These gargantuan galaxies are invisible in optical wavelengths so it’s extremely hard to do spectroscopy, a way to investigate stellar populations and chemical composition of galaxies. ALMA is not good at this and we need something more,” concluded Wang. “I’m eager for upcoming observatories like the space-based James Webb Space Telescope to show us what these primordial beasts are really made of.”

Hubble’s New Portrait Of Jupiter

A new Hubble Space Telescope view of Jupiter, taken on June 27, 2019, reveals the giant planet’s trademark Great Red Spot, and a more intense color palette in the clouds swirling in Jupiter’s turbulent atmosphere than seen in previous years. The colors, and their changes, provide important clues to ongoing processes in Jupiter’s atmosphere.

The bands are created by differences in the thickness and height of the ammonia ice clouds. The colorful bands, which flow in opposite directions at various latitudes, result from different atmospheric pressures. Lighter bands rise higher and have thicker clouds than the darker bands.

Among the most striking features in the image are the rich colors of the clouds moving toward the Great Red Spot, a storm rolling counterclockwise between two bands of clouds. These two cloud bands, above and below the Great Red Spot, are moving in opposite directions. The red band above and to the right (northeast) of the Great Red Spot contains clouds moving westward and around the north of the giant tempest. The white clouds to the left (southwest) of the storm are moving eastward to the south of the spot.

All of Jupiter’s colorful cloud bands in this image are confined to the north and south by jet streams that remain constant, even when the bands change color. The bands are all separated by winds that can reach speeds of up to 400 miles (644 kilometers) per hour.

On the opposite side of the planet, the band of deep red color northeast of the Great Red Spot and the bright white band to the southeast of it become much fainter. The swirling filaments seen around the outer edge of the red super storm are high-altitude clouds that are being pulled in and around it.

The Great Red Spot is a towering structure shaped like a wedding cake, whose upper haze layer extends more than 3 miles (5 kilometers) higher than clouds in other areas. The gigantic structure, with a diameter slightly larger than Earth’s, is a high-pressure wind system called an anticyclone that has been slowly downsizing since the 1800s. The reason for this change in size is still unknown.

A worm-shaped feature located below the Great Red Spot is a cyclone, a vortex around a low-pressure area with winds spinning in the opposite direction from the Red Spot. Researchers have observed cyclones with a wide variety of different appearances across the planet. The two white oval-shaped features are anticyclones, like small versions of the Great Red Spot.

Another interesting detail is the color of the wide band at the equator. The bright orange color may be a sign that deeper clouds are starting to clear out, emphasizing red particles in the overlying haze.

The new image was taken in visible light as part of the Outer Planets Atmospheres Legacy program, or OPAL. The program provides yearly Hubble global views of the outer planets to look for changes in their storms, winds and clouds.

Hubble’s Wide Field Camera 3 observed Jupiter when the planet was 400 million miles from Earth, when Jupiter was near “opposition” or almost directly opposite the Sun in the sky.

Dead Planets Can ‘Broadcast’ For Up To A Billion Years

Astronomers are planning to hunt for cores of exoplanets around white dwarf stars by ‘tuning in’ to the radio waves that they emit.

In new research led by the University of Warwick, scientists have determined the best candidate white dwarfs to start their search, based upon their likelihood of hosting surviving planetary cores and the strength of the radio signal that we can ‘tune in’ to.

Published in the Monthly Notices of the Royal Astronomical Society, the research led by Dr Dimitri Veras from the Department of Physics assesses the survivability of planets that orbit stars which have burnt all of their fuel and shed their outer layers, destroying nearby objects and removing the outer layers of planets. They have determined that the cores which result from this destruction may be detectable and could survive for long enough to be found from Earth.

The first exoplanet confirmed to exist was discovered orbiting a pulsar by co-author Professor Alexander Wolszczan from Pennsylvania State University in the 1990s, using a method that detects radio waves emitted from the star. The researchers plan to observe white dwarfs in a similar part of the electromagnetic spectrum in the hope of achieving another breakthrough.

The magnetic field between a white dwarf and an orbiting planetary core can form a unipolar inductor circuit, with the core acting as a conductor due to its metallic constituents. Radiation from that circuit is emitted as radio waves which can then be detected by radio telescopes on Earth. The effect can also be detected from Jupiter and its moon Io, which form a circuit of their own.

However, the scientists needed to determine how long those cores can survive after being stripped of their outer layers. Their modelling revealed that in a number of cases, planetary cores can survive for over 100 million years and as long as a billion years.

The astronomers plan to use the results in proposals for observation time on telescopes such as Arecibo in Puerto Rico and the Green Bank Telescope in West Virginia to try to find planetary cores around white dwarfs.

Lead author Dr Dimitri Veras from the University of Warwick said: “There is a sweet spot for detecting these planetary cores: a core too close to the white dwarf would be destroyed by tidal forces, and a core too far away would not be detectable. Also, if the magnetic field is too strong, it would push the core into the white dwarf, destroying it. Hence, we should only look for planets around those white dwarfs with weaker magnetic fields at a separation between about 3 solar radii and the Mercury-Sun distance.

“Nobody has ever found just the bare core of a major planet before, nor a major planet only through monitoring magnetic signatures, nor a major planet around a white dwarf. Therefore, a discovery here would represent ‘firsts’ in three different senses for planetary systems.”

Professor Alexander Wolszczan from Pennsylvania State University, said: “We will use the results of this work as guidelines for designs of radio searches for planetary cores around white dwarfs. Given the existing evidence for a presence of planetary debris around many of them, we think that our chances for exciting discoveries are quite good.”

Dr Veras added: “A discovery would also help reveal the history of these star systems, because for a core to have reached that stage it would have been violently stripped of its atmosphere and mantle at some point and then thrown towards the white dwarf. Such a core might also provide a glimpse into our own distant future, and how the solar system will eventually evolve.”

Hubble Uncovers A ‘Heavy Metal’ Exoplanet Shaped Like A Football

How can a planet be “hotter than hot?” The answer is when heavy metals are detected escaping from the planet’s atmosphere, instead of condensing into clouds.

Observations by NASA’s Hubble Space Telescope reveal magnesium and iron gas streaming from the strange world outside our solar system known as WASP-121b. The observations represent the first time that so-called “heavy metals” — elements heavier than hydrogen and helium — have been spotted escaping from a hot Jupiter, a large, gaseous exoplanet very close to its star.

Normally, hot Jupiter-sized planets are still cool enough inside to condense heavier elements such as magnesium and iron into clouds.

But that’s not the case with WASP-121b, which is orbiting so dangerously close to its star that its upper atmosphere reaches a blazing 4,600 degrees Fahrenheit. The temperature in WASP-121b’s upper atmosphere is about 10 times greater than that of any known planetary atmosphere. The WASP-121 system resides about 900 light-years from Earth.

“Heavy metals have been seen in other hot Jupiters before, but only in the lower atmosphere,” explained lead researcher David Sing of the Johns Hopkins University in Baltimore, Maryland. “So you don’t know if they are escaping or not. With WASP-121b, we see magnesium and iron gas so far away from the planet that they’re not gravitationally bound.”

Ultraviolet light from the host star, which is brighter and hotter than the Sun, heats the upper atmosphere and helps lead to its escape. In addition, the escaping magnesium and iron gas may contribute to the temperature spike, Sing said. “These metals will make the atmosphere more opaque in the ultraviolet, which could be contributing to the heating of the upper atmosphere,” he explained.

The sizzling planet is so close to its star that it is on the cusp of being ripped apart by the star’s gravity. This hugging distance means that the planet is football shaped due to gravitational tidal forces.

“We picked this planet because it is so extreme,” Sing said. “We thought we had a chance of seeing heavier elements escaping. It’s so hot and so favorable to observe, it’s the best shot at finding the presence of heavy metals. We were mainly looking for magnesium, but there have been hints of iron in the atmospheres of other exoplanets. It was a surprise, though, to see it so clearly in the data and at such great altitudes so far away from the planet. The heavy metals are escaping partly because the planet is so big and puffy that its gravity is relatively weak. This is a planet being actively stripped of its atmosphere.”

The researchers used the observatory’s Space Telescope Imaging Spectrograph to search in ultraviolet light for the spectral signatures of magnesium and iron imprinted on starlight filtering through WASP-121b’s atmosphere as the planet passed in front of, or transited, the face of its home star.

This exoplanet is also a perfect target for NASA’s upcoming James Webb Space Telescope to search in infrared light for water and carbon dioxide, which can be detected at longer, redder wavelengths. The combination of Hubble and Webb observations would give astronomers a more complete inventory of the chemical elements that make up the planet’s atmosphere.

The WASP-121b study is part of the Panchromatic Comparative Exoplanet Treasury (PanCET) survey, a Hubble program to look at 20 exoplanets, ranging in size from super-Earths (several times Earth’s mass) to Jupiters (which are over 100 times Earth’s mass), in the first large-scale ultraviolet, visible, and infrared comparative study of distant worlds.

The observations of WASP-121b add to the developing story of how planets lose their primordial atmospheres. When planets form, they gather an atmosphere containing gas from the disk in which the planet and star formed. These atmospheres consist mostly of the primordial, lighter-weight gases hydrogen and helium, the most plentiful elements in the universe. This atmosphere dissipates as a planet moves closer to its star.

“The hot Jupiters are mostly made of hydrogen, and Hubble is very sensitive to hydrogen, so we know these planets can lose the gas relatively easily,” Sing said. “But in the case of WASP-121b, the hydrogen and helium gas is outflowing, almost like a river, and is dragging these metals with them. It’s a very efficient mechanism for mass loss.”

The results will appear online today in The Astronomical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.