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Exoplanets where life could develop as on Earth

Cambridge UK (SPX)

Aug 03, 2018

Scientists have identified a group of planets outside our solar system where the same chemical conditions that may have led to life on Earth exist.

The researchers, from the University of Cambridge and the Medical Research Council Laboratory of Molecular Biology (MRC LMB), found that the chances for life to develop on the surface of a rocky planet like Earth are connected to the type and strength of light given off by its host star.

Their study, published in the journal Science Advances, proposes that stars which give off sufficient ultraviolet (UV) light could kick-start life on their orbiting planets in the same way it likely developed on Earth, where the UV light powers a series of chemical reactions that produce the building blocks of life.

The researchers have identified a range of planets where the UV light from their host star is sufficient to allow these chemical reactions to take place, and that lie within the habitable range where liquid water can exist on the planet’s surface.

“This work allows us to narrow down the best places to search for life,” said Dr. Paul Rimmer, a postdoctoral researcher with a joint affiliation at Cambridge’s Cavendish Laboratory and the MRC LMB, and the paper’s first author. “It brings us just a little bit closer to addressing the question of whether we are alone in the universe.”

The new paper is the result of an ongoing collaboration between the Cavendish Laboratory and the MRC LMB, bringing together organic chemistry and exoplanet research. It builds on the work of Professor John Sutherland, a co-author on the current paper, who studies the chemical origin of life on Earth.

In a paper published in 2015, Professor Sutherland’s group at the MRC LMB proposed that cyanide, although a deadly poison, was in fact a key ingredient in the primordial soup from which all life on Earth originated.

In this hypothesis, carbon from meteorites that slammed into the young Earth interacted with nitrogen in the atmosphere to form hydrogen cyanide. The hydrogen cyanide rained to the surface, where it interacted with other elements in various ways, powered by the UV light from the Sun. The chemicals produced from these interactions generated the building blocks of RNA, the close relative of DNA which most biologists believe was the first molecule of life to carry information.

In the laboratory, Sutherland’s group recreated these chemical reactions under UV lamps, and generated the precursors to lipids, amino acids and nucleotides, all of which are essential components of living cells.

“I came across these earlier experiments, and as an astronomer, my first question is always what kind of light are you using, which as chemists they hadn’t really thought about,” said Rimmer. “I started out measuring the number of photons emitted by their lamps, and then realized that comparing this light to the light of different stars was a straightforward next step.”

The two groups performed a series of laboratory experiments to measure how quickly the building blocks of life can be formed from hydrogen cyanide and hydrogen sulphite ions in water when exposed to UV light. They then performed the same experiment in the absence of light.

“There is chemistry that happens in the dark: it’s slower than the chemistry that happens in the light, but it’s there,” said senior author Professor Didier Queloz, also from the Cavendish Laboratory. “We wanted to see how much light it would take for the light chemistry to win out over the dark chemistry.”

The same experiment run in the dark with the hydrogen cyanide and the hydrogen sulphite resulted in an inert compound which could not be used to form the building blocks of life, while the experiment performed under the lights did result in the necessary building blocks.

The researchers then compared the light chemistry to the dark chemistry against the UV light of different stars. They plotted the amount of UV light available to planets in orbit around these stars to determine where the chemistry could be activated.

They found that stars around the same temperature as our Sun emitted enough light for the building blocks of life to have formed on the surfaces of their planets. Cool stars, on the other hand, do not produce enough light for these building blocks to be formed, except if they have frequent powerful solar flares to jolt the chemistry forward step by step. Planets that both receive enough light to activate the chemistry and could have liquid water on their surfaces reside in what the researchers have called the abiogenesis zone.

Among the known exoplanets which reside in the abiogenesis zone are several planets detected by the Kepler telescope, including Kepler 452b, a planet that has been nicknamed Earth’s ‘cousin,’ although it is too far away to probe with current technology. Next-generation telescopes, such as NASA’s TESS and James Webb telescopes, will hopefully be able to identify and potentially characterize many more planets that lie within the abiogenesis zone.

Of course, it is also possible that if there is life on other planets, that it has or will develop in a totally different way than it did on Earth.

“I’m not sure how contingent life is, but given that we only have one example so far, it makes sense to look for places that are most like us,” said Rimmer. “There’s an important distinction between what is necessary and what is sufficient. The building blocks are necessary, but they may not be sufficient: it’s possible you could mix them for billions of years and nothing happens. But you want to at least look at the places where the necessary things exist.”

According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. “Getting some idea of what fraction have been, or might be, primed for life fascinates me,” said Sutherland. “Of course, being primed for life is not everything and we still don’t know how likely the origin of life is, even given favorable circumstances – if it’s really unlikely then we might be alone, but if not, we may have company.”

Source: Space Daily.



Pair of colliding stars spill radioactive molecules into space

Charlottesville VA (SPX)

Aug 02, 2018

When two Sun-like stars collide, the result can be a spectacular explosion and the formation of an entirely new star. One such event was seen from Earth in 1670. It appeared to observers as a bright, red “new star.” Though initially visible with the naked eye, this burst of cosmic light quickly faded and now requires powerful telescopes to see the remains of this merger: a dim central star surrounded by a halo of glowing material flowing away from it.

Approximately 348 years after this event, an international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) and the NOEMA (Northern Extended Millimeter Array) radio telescopes studied the remains of this explosive stellar merger – known as CK Vulpeculae (CK Vul) – and discovered the clear and convincing signature of a radioactive version of aluminum (26Al, an atom with 13 protons and 13 neutron) bound with atoms of fluorine, forming 26-aluminum monofluoride (26AlF).

This is the first molecule bearing an unstable radioisotope definitively detected outside of our solar system. Unstable isotopes have an excess of nuclear energy and eventually decay into a stable, less-radioactive form. In this case, the 26-aluminum (26Al) decays to 26-magnesium (26Mg).

“The first solid detection of this kind of radioactive molecule is an important milestone in our exploration of the cool molecular universe,” said Tomasz Kami?ski, an astronomer with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and lead author on a paper appearing in Nature Astronomy.

The researchers detected the unique spectral signature of these molecules in the debris surrounding CK Vul, which is approximately 2,000 light-years from Earth. As these molecules spin and tumble through space, they emit a distinctive fingerprint of millimeter-wavelength light, a process known as “rotational transition.” Astronomers consider this the “gold standard” for molecular detections.

These characteristic molecular fingerprints are usually taken from laboratory experiments and then used to identify molecules in space. In the case of 26AlF, this method is not applicable because 26-aluminum is not present on Earth. Laboratory astrophysicists from the University of Kassel/Germany therefore used the fingerprint data of stable and abundant 27AlF molecules to derive accurate data for the rare 26AlF molecule.

“This method of extrapolation is based on the so-called Dunham approach,” explained Alexander Breier from the Kassel team. “It allows researchers to precisely calculate the rotational transitions of 26AlF with an accuracy far beyond the needs of astronomical observers.”

The observation of this particular isotopologue provides fresh insights into the merger process that created CK Vul. It also demonstrates that the deep, dense inner layers of a star, where heavy elements and radioactive isotopes are forged, can be churned up and cast into space by stellar collisions. “We are observing the guts of a star torn apart three centuries ago by a collision,” observed Kami?ski. “How cool is that?”

The astronomers also determined that the two stars that merged were relatively low-mass, with one being a red giant star with a mass somewhere between 0.8 and 2.5 times that of our Sun.

“This first direct observation of this isotope in a stellar-like object is also important in the broader context of galactic chemical evolution,” noted Kami?ski. “This is the first time an active producer of the radioactive nuclide 26Al has been directly observationally identified.”

It has been known for decades that there is about three entire Suns’ worth of 26Al spread across the Milky Way. But these observations, made at gamma-ray wavelengths, could only identify that the signal was there; they couldn’t pinpoint individual sources and it was unclear how the isotopes got there.

With current estimates on the mass of 26Al in CK Vul (about a quarter the mass of Pluto) and the rare occurrence of mergers such as this, it seems rather unlikely that mergers are solely responsible for this galactic radioactive material, the astronomers conclude.

However, ALMA and NOEMA can only detect the amount of 26Al bound with fluorine. The actual mass of 26Al in CK Vul (in atomic form) may be much greater. It is also possible that other merger remnants may have far greater amounts. Astronomers may also have underestimated the current merger rates in the Milky Way. “So this is not a closed issue and the role of mergers may be non-negligible,” speculated Kamiski.

Source: Space Daily.


NASA finds a large amount of water in an exoplanet’s atmosphere

by Ann Jenkins for STSI News

Baltimore MD (SPX)

Mar 02, 2018

Much like detectives study fingerprints to identify the culprit, scientists used NASA’s Hubble and Spitzer space telescopes to identify the “fingerprints” of water in the atmosphere of a hot, bloated, Saturn-mass exoplanet some 700 light-years away. And, they found a lot of water. In fact, the planet, known as WASP-39b, has three times as much water as Saturn does.

Though no planet like this resides in our solar system, WASP-39b can provide new insights into how and where planets form around a star, say researchers. This exoplanet is so unique, it underscores the fact that the more astronomers learn about the complexity of other worlds, the more there is to learn about their origins. This latest observation is a significant step toward characterizing these worlds.

Although the researchers predicted they’d see water, they were surprised by how much water they found in this “hot Saturn.” Because WASP-39b has so much more water than our famously ringed neighbor, it must have formed differently. The amount of water suggests that the planet actually developed far away from the star, where it was bombarded by a lot of icy material. WASP-39b likely had an interesting evolutionary history as it migrated in, taking an epic journey across its planetary system and perhaps obliterating planetary objects in its path.

“We need to look outward so we can understand our own solar system,” explained lead investigator Hannah Wakeford of the Space Telescope Science Institute in Baltimore, Maryland, and the University of Exeter in Devon, United Kingdom. “But exoplanets are showing us that planet formation is more complicated and more confusing than we thought it was. And that’s fantastic!”

Wakeford and her team were able to analyze the atmospheric components of this exoplanet, which is similar in mass to Saturn but profoundly different in many other ways. By dissecting starlight filtering through the planet’s atmosphere into its component colors, the team found clear evidence for water. This water is detected as vapor in the atmosphere.

Using Hubble and Spitzer, the team has captured the most complete spectrum of an exoplanet’s atmosphere possible with present-day technology. “This spectrum is thus far the most beautiful example we have of what a clear exoplanet atmosphere looks like,” said Wakeford.

“WASP-39b shows exoplanets can have much different compositions than those of our solar system,” said co-author David Sing of the University of Exeter in Devon, United Kingdom. “Hopefully this diversity we see in exoplanets will give us clues in figuring out all the different ways a planet can form and evolve.”

Located in the constellation Virgo, WASP-39b whips around a quiet, Sun-like star, called WASP-39, once every four days. The exoplanet is currently positioned more than 20 times closer to its star than Earth is to the Sun. It is tidally locked, meaning it always shows the same face to its star.

Its day-side temperature is a scorching 1,430 degrees Fahrenheit (776.7 degrees Celsius). Powerful winds transport heat from the day-side around the planet, keeping the permanent night-side almost as hot. Although it is called a “hot Saturn,” WASP-39b is not known to have rings. Instead, it has a puffy atmosphere that is free of high-altitude clouds, allowing Wakeford and her team to peer down into its depths.

Looking ahead, Wakeford hopes to use the James Webb Space Telescope – scheduled to launch in 2019 – to get an even more complete spectrum of the exoplanet. Webb will be able to give information about the planet’s atmospheric carbon, which absorbs light at longer, infrared wavelengths than Hubble can see. By understanding the amount of carbon and oxygen in the atmosphere, scientists can learn even more about where and how this planet formed.

Source: Space Daily.


TRAPPIST-1 System Planets Potentially Habitable

Tucson AZ (SPX)

Jan 24, 2018

Two exoplanets in the TRAPPIST-1 system have been identified as most likely to be habitable, a paper by PSI Senior Scientist Amy Barr says.

The TRAPPIST-1 system has been of great interest to observers and planetary scientists because it seems to contain seven planets that are all roughly Earth-sized, Barr and co-authors Vera Dobos and Laszlo L. Kiss said in “Interior Structures and Tidal Heating in the TRAPPIST-1 Planets” that appears in Astronomy and Astrophysics.

“Because the TRAPPIST-1 star is very old and dim, the surfaces of the planets have relatively cool temperatures by planetary standards, ranging from 400 degrees Kelvin (260 degrees Fahrenheit), which is cooler than Venus, to 167 degrees Kelvin (-159 degrees Fahrenheit), which is colder than Earth’s poles,” Barr said.

“The planets also orbit very close to the star, with orbital periods of a few days. Because their orbits are eccentric – not quite circular – these planets could experience tidal heating just like the moons of Jupiter and Saturn.”

“Assuming the planets are composed of water ice, rock, and iron, we determine how much of each might be present, and how thick the different layers would be. Because the masses and radii of the planets are not very well-constrained, we show the full range of possible interior structures and interior compositions.” Barr said. The team’s results show that improved estimates of the masses of each planet can help determine whether each of the planets has a significant amount of water.

The planets studied are referred to by letter, planets b through h, in order of their distance from the star. Analyses performed by co-author Vera Dobos show that planets d and e are the most likely to be habitable due to their moderate surface temperatures, modest amounts of tidal heating, and because their heat fluxes are low enough to avoid entering a runaway greenhouse state. A global water ocean likely covers planet d.

The team calculated the balance between tidal heating and heat transport by convection in the mantles of each planet. Results show that planets b and c likely have partially molten rock mantles. The paper also shows that planet c likely has a solid rock surface, and could have eruptions of silicate magmas on its surface driven by tidal heating, similar to Jupiter’s moon Io.

Source: Space Daily.


Overlooked Treasure: The First Evidence of Exoplanets

Pasadena CA (JPL)

Nov 02, 2017

Beneath an elegant office building with a Spanish-style red tiled roof in Pasadena, California, three timeworn storerooms safeguard more than a century of astronomy. Down the stairs and to the right is a basement of wonder. There are countless wooden drawers and boxes, stacked floor to ceiling, with telescope plates, sunspot drawings and other records. A faint ammonia-like smell, reminiscent of old film, fills the air. Guarding one storeroom is a short black door with a sign saying “This door to be kept closed.”

Carnegie Observatories hosts 250,000 photographic plates taken at Mount Wilson, Palomar and Las Campanas observatories, spanning more than 100 years. In their heydays, the Mount Wilson 60-inch and 100-inch telescopes – the bigger saw its first light on Nov. 1, 1917 – were the most powerful instruments of their kind.

Each indelibly changed humanity’s understanding of our place in the cosmos. But these technological marvels were ahead of their time – in one case, capturing signs of distant worlds that wouldn’t be recognized for a century.

Mount Wilson is the site where some of the key discoveries about our galaxy and universe were made in the early 20th century. This is where Edwin Hubble realized that the Milky Way cannot be the extent of our universe, because Andromeda (or M31) is farther away than the most distant reaches of our galaxy. The photographic plate from the 100-inch Hooker Telescope from 1923, which captured this monumental realization, is blown up as a huge poster outside the Carnegie storerooms.

Hubble and Milton Humason, whose Mount Wilson career began as a janitor, worked together to explore the expanding nature of the universe. Using the legendary telescopes, as well as data from Lowell Observatory in Flagstaff, Arizona, they recognized that clusters of galaxies are traveling away from each other – and the more distant galaxies move away from each other at greater speeds.

But there is a far lesser known, 100-year-old discovery from Mount Wilson, one that was unidentified and unappreciated until recently. It’s actually: The first evidence of exoplanets.

A detective story

It started with Ben Zuckerman, professor emeritus of astronomy at the University of California, Los Angeles. He was preparing a talk about the compositions of planets and smaller rocky bodies outside our solar system for a July 2014 symposium at the invitation of Jay Farihi, whom he had helped supervise when Farihi was a graduate student at UCLA. Farihi had suggested that Zuckerman talk about the pollution of white dwarfs, which are faint, dead stars composed of mainly hydrogen and helium.

By “pollution,” astronomers mean heavy elements invading the photospheres – the outer atmospheres – of these stars. The thing is, all those extra elements shouldn’t be there – the strong gravity of the white dwarf should pull the elements into the star’s interior, and out of sight.

The first polluted white dwarf identified is called van Maanen’s Star (or “van Maanen 2” in the scientific literature), after its discoverer Adriaan van Maanen. Van Maanen found this object in 1917 by spotting its subtle motion relative to other stars between 1914 and 1917. Astronomer Walter Sydney Adams, who would later become director of Mount Wilson, captured the spectrum – a chemical fingerprint – of van Maanen’s Star on a small glass plate using Mount Wilson’s 60-inch telescope.

Adams interpreted the spectrum to be of an F-type star, presumably based on the presence and strength of calcium and other heavy-element absorption features, with a temperature somewhat higher than our Sun. In 1919, van Maanen called it a “very faint star.”

Today, we know that van Maanen’s Star, which is about 14 light-years away, is the closest white dwarf to Earth that is not part of a binary system.

“This star is an icon,” Farihi said recently. “It is the first of its type. It’s really the proto-prototype.”

While preparing his talk, Zuckerman had what he later called a “true ‘eureka’ moment.” Van Maanen’s Star, unbeknownst to the astronomers who studied it in 1917 and those who thought about it for decades after, must be the first observational evidence that exoplanets exist.

What does this have to do with exoplanets?

Heavy elements in the star’s outermost layer could not have been produced inside the star, because they would immediately sink due to the white dwarf’s intense gravitational field. As more white dwarfs with heavy elements in their photospheres were discovered in the 20th century, scientists came to believe that the exotic materials must have come from the interstellar medium – in other words, elements floating in the space between the stars.

But in 1987, more than 70 years after the Mount Wilson spectrum of van Maanen’s Star, Zuckerman and his colleague Eric Becklin reported an excess of infrared light around a white dwarf, which they thought might come from a faint “failed star” called a brown dwarf. This was, in 1990, interpreted to be a hot, dusty disk orbiting a white dwarf. By the early 2000s, a new theory of polluted white dwarfs had emerged: Exoplanets could push small rocky bodies toward the star, whose powerful gravity would pulverize them into dust. That dust, containing heavy elements from the torn-apart body, would then fall on the star.

“The bottom line is: if you’re an asteroid or comet, you can’t just change your address. You need something to move you,” Farihi said. “By far, the greatest candidates are planets to do that.”

NASA’s Spitzer Space Telescope has been instrumental in expanding the field of polluted white dwarfs orbited by hot, dusty disks. Since launch in 2004, Spitzer has confirmed about 40 of these special stars. Another space telescope, NASA’s Wide-field Infrared Survey Explorer, also detected a handful, bringing the total up to about four dozen known today. Because these objects are so faint, infrared light is crucial to identifying them.

“We can’t measure the exact amount of infrared light coming from these objects using telescopes on the ground,” Farihi said. “Spitzer, specifically, just burst this wide open.”

Supporting the new “dusty disk” theory of pulled white dwarfs, in 2007, Zuckerman and colleagues published observations of a white dwarf atmosphere with 17 elements – materials similar to those found in the Earth-Moon system. (The late UCLA professor Michael Jura, who made crucial contributions to the study of polluted white dwarfs, was part of this team.)

This was further evidence that at least one small, rocky body – or even a planet – had been torn apart by the gravity of a white dwarf. Scientists now generally agree that a single white dwarf star with heavy elements in its spectrum likely has at least one rocky debris belt – the remnants of bodies that collided violently and never formed planets – and probably at least one major planet.

So, heavy elements that happened to be floating in the interstellar medium could not account for the observations. “About 90 years after van Maanen’s discovery, astronomers said, ‘Whoa, this interstellar accretion model can’t possibly be right,'” Zuckerman said.

Chasing the spectrum

Inspired by Zuckerman, Farihi became enamored with the idea that someone had taken a spectrum with the first evidence of exoplanets in 1917, and that a record must exist of that observation. “I got my teeth in the question and I wouldn’t let go,” he said.

Farihi reached out to the Carnegie Observatories, which owns the Mount Wilson telescopes and safeguards their archives. Carnegie Director John Mulchaey put volunteer Dan Kohne on the case. Kohne dug through the archives and, two days later, Mulchaey sent Farihi an image of the spectrum.

“I can’t say I was shocked, frankly, but I was pleasantly blown out of my seat to see that the signature was there, and could be seen even with the human eye,” Farihi said.

The spectrum of van Maanen’s Star that Farihi had requested is now located in a small archival sleeve, labeled with the handwritten date “1917 Oct 24” and a modern yellow sticky note: “possibly 1st record of an exoplanet.”

Cynthia Hunt, an astronomer who serves as chair of Carnegie’s history committee, took the glass plate out of the envelope and placed it onto a viewer that lit it up. The spectrum itself just about 1/6th of an inch, or a bit over 0.4 centimeters.

Though the plate seems unremarkable at first glance, Farihi saw two obvious “fangs” representing dips in the spectrum. To him, this was the smoking gun: Two absorption lines from the same calcium ion, meaning there were heavy elements in the photosphere of the white dwarf – indicating it likely has at least one exoplanet. He wrote about it in 2016 in New Astronomy Reviews.

Exoplanets and debris disks

Scientists have long thought the gravity of giant planets could be keeping debris belts in place, especially in young planetary systems. A recent study in The Astrophysical Journal showed that young stars with disks of dust and debris are more likely to have giant planets orbiting at great distance from their parent star than those without disks.

A white dwarf is not a young star – on the contrary, it forms when a low-to-medium-mass star has already burned all of the fuel in its interior. But the principle is the same: The gravitational pull of giant exoplanets could throw small, rocky bodies into the white dwarfs.

Our own Sun will become a red giant in about 5 billion years, expanding so much it may even swallow Earth before it blows off its outer layers and becomes a white dwarf. At that point, Jupiter’s large gravitational influence may be more disruptive to the asteroid belt, flinging objects toward our much-dimmer Sun. This kind of scenario could explain the heavy elements at van Maanen’s Star.

Spitzer’s observations of van Maanen’s Star have not found any planets there so far. In fact, to date, no exoplanets have been confirmed orbiting white dwarfs, although one does have an object thought to be a massive planet. Other compelling evidence has emerged just in the last couple of years. Using the W. M. Keck Observatory in Hawaii, scientists, including Zuckerman, recently announced that they had found evidence of a Kuiper-Belt-like object having been eaten by a white dwarf.

Scientists are still exploring polluted white dwarfs and looking for the exoplanets they may host. About 30 percent of all white dwarfs we know about are polluted, but their debris disks are harder to spot. Jura put forward that with lots of asteroids coming in and colliding with debris, dust may be converted into gas, which would not have the same highly detectable infrared signal as dust.

Farihi was thrilled about how his Mount Wilson archive detective work turned out. In 2016, he described the historical find in the context of a review paper about polluted white dwarfs, arguing that white dwarfs are “compelling targets for exoplanetary system research.”

Who knows what other overlooked treasures await discovery in the archives of great observatories – the sky-watching records of a cosmos rich in subtlety. Surely, other clues will be found by those motivated by curiosity who ask the right questions.

“It’s personal interaction with data that can really spur us to get invested in the questions that we’re asking,” Farihi said.

Source: Space Daily.


Atmosphere around super-earth detected

Heidelberg, Germany (SPX)

Apr 07, 2017

Astronomers have detected an atmosphere around the super-Earth GJ 1132b. This marks the first detection of an atmosphere around a low-mass super-Earth, in terms of radius and mass the most Earth-like planet around which an atmosphere has yet been detected. Thus, this is a significant step on the path towards the detection of life on an exoplanet.

The team, which includes researchers from the Max Planck Institute for Astronomy, used the 2.2-m ESO/MPG telescope in Chile to take images of the planet’s host star, GJ 1132, and measured the slight decrease in brightness as the planet and its atmosphere absorbed some of the starlight while passing directly in front of their host star.

While it’s not the detection of life on another planet, it’s an important step in the right direction: the detection of an atmosphere around the super-Earth GJ 1132b marks the first time an atmosphere has been detected around a planet with a mass and radius close to Earth’s mass and radius (1.6 Earth masses, 1.4 Earth radii).

Astronomers’ current strategy for finding life on another planet is to detect the chemical composition of that planet’s atmosphere, on the lookout for certain chemical imbalances that require the presence of living organisms as an explanation. In the case of our own Earth, the presence of large amounts of oxygen is such a trace.

We’re still a long way from that detection though. Until the work described in this article, the (few!) observations of light from exoplanet atmospheres all involved planets much more massive than Earth: gas giants – relatives of our own solar system’s Jupiter – and a large super-Earth with more than eight times the Earth’s mass. With the present observation, we’ve taken the first tentative steps into analyzing the atmosphere of smaller, lower-mass planets that are much more Earth-like in size and mass.

The planet in question, GJ 1132b, orbits the red dwarf star GJ 1132 in the southern constellation Vela, at a distance of 39 light-years from us. Recently, the system has come under scrutiny by a team led by John Southworth (Keele University, UK).

The project was conceived, and the observations coordinated, by Luigi Mancini, formerly of the Max Planck Institute for Astronomy (MPIA) and now working at the University of Rome Tor Vergata. Additional MPIA team members were Paul Molliere and Thomas Henning.

The team used the GROND imager at the 2.2-m ESO/MPG telescope of the European Southern Observatory in Chile to observe the planet simultaneously in seven different wavelength bands. GJ 1132b is a transiting planet: From the perspective of an observer on Earth, it passes directly in front of its star every 1.6 days, blocking some of the star’s light.

The size of stars like GJ 1132 is well known from stellar models. From the fraction of starlight blocked by the planet, astronomers can deduce the planet’s size – in this case around 1.4 times the size of the Earth. Crucially, the new observations showed the planet to be larger at one of the infrared wavelengths than at the others.

This suggests the presence of an atmosphere that is opaque to this specific infrared light (making the planet appear larger) but transparent at all the others.

Different possible versions of the atmosphere were then simulated by team members at the University of Cambridge and the Max Planck Institute for Astronomy. According to those models, an atmosphere rich in water and methane would explain the observations very well.

The discovery comes with the usual exoplanet caveats: while somewhat larger than Earth, and with 1.6 times Earth’s mass (as determined by earlier measurements), observations to date do not provide sufficient data to decide how similar or dissimilar GJ 1132b is to Earth. Possibilities include a “water world” with an atmosphere of hot steam.

The presence of the atmosphere is a reason for cautious optimism. M dwarfs are the most common types of star, and show high levels of activity; for some set-ups, this activity (in the shape of flares and particle streams) can be expected to blow away nearby planets’ atmospheres.

GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years (that is, long enough for us to detect it). Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe.

In any case, the new observations make GJ 1132b a high-priority target for further study by instruments such as the Hubble Space Telescope, ESO’s Very Large Telescope, and the James Webb Space Telescope slated for launch in 2018.

Source: Space Daily.


Possible Venus twin discovered around dim star

Mountain View CA (SPX)

Apr 07, 2017

Astronomers using NASA’s Kepler space telescope have found a planet 219 light-years away that seems to be a close relative to Venus. This newly discovered world is only slightly larger than Earth and orbits a low-temperature star called Kepler-1649 that’s one-fifth the diameter of our Sun.

The planet tightly embraces its dim home star, encircling it every 9 days. The tight orbit causes the flux of sunlight reaching the planet to be 2.3 times as great as the solar flux on Earth. For comparison, the solar flux on Venus is 1.9 times the terrestrial value.

The discovery will provide insight into the nature of planets around M dwarf stars, by far the most common type in the universe. While such stars are redder and dimmer than the Sun, recent exoplanet discoveries have revealed instances in which Earth-sized worlds circle an M dwarf in orbits that would place them in their star’s habitable zone. But such worlds might not inevitably resemble Earth, with its salubrious climate. They could just as well be analogs of Venus, with thick atmospheres and scalding temperatures.

According to SETI Institute scientist Isabel Angelo, the study of planets similar to the Venus analog Kepler-1649b is “becoming increasingly important in order to understand the habitable zone boundaries of M dwarfs.

“There are several factors, like star variability and tidal effects, that make these planets different from Earth-sized planets around Sun-like stars.”

It’s said that Venus is Earth’s sister planet, but in many ways it’s not a close sibling. Despite being the same size as Earth, and only 40 percent closer to the Sun, its atmosphere and surface temperature are wildly different from our own. If we wish to find life on other Earth-sized worlds, we should take a cue from “The Music Man” and get to know the territory.

Elisa Quintana, from the SETI Institute and NASA Goddard Space Flight Center, and a member of the Kepler 1649b discovery team, notes, “Many people are hung up on finding other Earths. But Venus analogs are just as important.

“Since new telescopes coming down the pike will allow us to probe atmospheres, focusing on both Earth and Venus analogs may help decipher why, in our solar system, one planet allows life to thrive, and one does not, despite having similar masses, comparable densities, etc.”

Source: Space Daily.


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