Planet and Star Formation

We study the formation of stars on all scales and the birth of planetary systems and their evolution. The Department established observational programs to search for extrasolar planets and to characterize their properties. We investigate the chemical and physical state of the interstellar medium and protoplanetary disks in dedicated laboratory experiments where we study the formation of complex organic molecules and cosmic dust analogues.

Star formation is a key process in the universe, shaping the structure of entire galaxies and driving their chemical evolution and, at the same time, providing the conditions for the formation of planets. Our goal is to understand the different modes of star formation, from massive star clusters to more isolated groups of low-mass stars.

We want to unravel the mysteries of planet formation from tiny dust grains to the formation of giant planets and their migration in gas disks. At the same time, we establish new search strategies for brown dwarfs and exoplanets and are beginning to characterize their atmospheres.

To this end, we combine multi-wavelength observations from large ground-based telescopes and space-born infrared observatories with large-scale numerical simulations on supercomputers, theoretical models, and dedicated laboratory experiments. Our research places extreme demands on observational techniques, pushing available angular resolution, dynamic range, and spectral resolving power to their limits. We help develop and construct astronomical instruments to meet these demanding requirements. Our particular fields of expertise are adaptive optics and interferometry for ground-based observations, and sensitive space-based infrared instruments.

Source: Max Planck Institute for Astronomy

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Heidelberg Initiative for the Origins of Life – HIFOL

The Heidelberg Initiative for the Origins of Life (HIFOL) seeks to understand one of the most fundamental questions of humanity: how did life emerge on Earth and does life exist elsewhere in the Universe. HIFOL facilitates a wide range of interdisciplinary theoretical, experimental, and observational research covering the fields of astronomy, physics, geosciences, chemistry, biology and life sciences from a range of research institutes based in Heidelberg. HIFOL brings together researchers from the Max Planck Institute for Astronomy, the Max Planck Institute for Nuclear Physics, the University of Heidelberg, Heidelberg Institute of Theoretical Studies, and Kirchhoff Institute for Physics, each tackling different aspects of the same problem.

Astrophysicists aim to understand how planets form around stars and search for habitable Earth analogues, characterizing their atmospheres, using both space- and ground-based telescopes. Using both meteoritic and earth samples, geoscientists strive to unravel the past evolutionary history of the solar system and earth itself, including its interior, crust and hydrosphere. Chemists focus on studying the conditions at which amino acids, nucleotides and their first chains could be abiogenically synthesized and started the self-catalytic replication cycle, while biologists seek to figure out how transition from a non-living to a living world has occurred and where on early Earth it has happened, and how first cells, their membranes, metabolic and reproduction systems have emerged.

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Contact:

Dr. Myriam Benisty
Director
benisty@mpia.de

Office:

Christelle Hiemstra
Assistant to the Managing Director
tel:06221/528-436
hiemstra@mpia.de

Director Emeritus:

Prof. Dr. Dr. h.c. Thomas K. Henning
tel:+49 6221 528-200
henning@mpia.de

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New Era of Exoplanet Discovery Begins with Images of ‘Jupiter’s Younger Sibling’

A direct image captured with the keck ii telescope of af lep b, an extrasolar planet that has a mass and orbit similar to jupiter.
Credit: University of Texas at Austin/W. M. Keck Observatory

Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Maunakea, Hawaiʻi Island have discovered one of the lowest-mass planets whose images have been directly captured. Not only were they able to measure its mass, but they were also able to determine that its orbit is similar to the giant planets in our own solar system.

The planet, called AF Lep b, is among the first ever discovered using a technique called astrometry; this method measures the subtle movements of a host star over many years to help astronomers determine whether hard-to-see orbiting companions, including planets, are gravitationally tugging at it.

The study, led by astronomy graduate student Kyle Franson at the University of Texas at Austin (UT Austin), is published in today’s issue of Astrophysical Journal Letters.

“When we processed the observations using the Keck II telescope in real time to carefully remove the glare of the star, the planet immediately popped out and became increasingly apparent the longer we observed,” said Franson.

The direct images Franson’s team captured revealed that AF Lep b is about three times the mass of Jupiter and orbits AF Leporis, a young Sun-like star about 87.5 light-years away. They took a series of deep images of the planet starting in December 2021; two other teams also captured images of the same planet since then.

“This is the first time this method has been used to find a giant planet orbiting a young analog of the Sun,” said Brendan Bowler, an assistant professor of astronomy at UT Austin and senior author on the study. “This opens the door to using this approach as a new tool for exoplanet discovery.”

The movement of the extrasolar planet AF Lep b (white spot at about 10 o’clock) around its host star (center) can be seen in these two images taken in Dec. 2021 and Feb. 2023. Images were collected using the W. M. Keck Observatory’s 10-meter telescope in Hawaiʻi. Credit: Kyle Franson, University of Texas at Austin/W. M. Keck Observatory

Despite having a much smaller mass than its host star, an orbiting planet causes a star’s position to wobble slightly around the center of mass of the planetary system. Astrometry uses this shift in a star’s position on the sky relative to other stars to infer the existence of orbiting planets. Franson and Bowler identified the star AF Leporis as one that might harbor a planet, given the way it had moved during 25 years of observations from the Hipparcos and Gaia satellites.

To directly image the planet, the UT Austin team used Keck Observatory’s adaptive optics system, which corrects for fluctuations caused by turbulence in Earth’s atmosphere, paired with the Keck II Telescope’s Near-Infrared Camera 2 (NIRC2) Vector Vortex Coronagraph, which suppresses light from the host star so the planet could be seen more clearly. AF Lep b is about 10,000 times fainter than its host star and is located about 8 times the Earth-Sun distance.

“Imaging planets is challenging,” Franson said. “We only have about 15 examples, and we think this new ‘dynamically informed’ approach made possible by the Keck II telescope and NIRC2 adaptive optics imaging will be much more efficient compared to blind surveys which have been carried out for the past two decades.”

This chart shows the masses and orbital distances of all the extrasolar planets that have been directly imaged so far. Astronomers have confirmed the masses of five (marked with stars) and estimated the rest (dots). The newly imaged planet, AF Lep b (yellow star), has a mass and orbit that make it one of the most Jupiter-like extrasolar planets imaged so far. Credit: Brendan Bowler, University of Texas at Austin

The two most common ways of finding extrasolar planets involve observing slight, periodic dimming of the starlight if a planet happens to regularly pass in front of the star— like a moth spiraling around a porch light — and measuring minute changes in the frequencies of starlight that result from the planet tugging the star back and forth along the direction to Earth. Both methods tend to work best with large planets orbiting close to their host stars, and both methods are indirect: we don’t see the planet, we only see how it influences the star.

The method of combining direct imaging with astrometry could help astronomers find extrasolar planets that were hard to find before with other methods because they were too far from their host star, were too low mass, or didn’t have orbits that were edge-on as seen from Earth. Another benefit of this technique is that it allows astronomers to directly measure a planet’s mass, which is difficult with other methods at wide orbital distances.

Bowler said the team plans to continue studying AF Lep b.

“This will be an excellent target to further characterize with the James Webb Space Telescope and the next generation of large ground-based telescopes like the Giant Magellan Telescope and the Thirty Meter Telescope,” Bowler said. “We’re already planning more sensitive follow-up efforts at longer wavelengths to study the physical properties and atmospheric chemistry of this planet.”

NASA Keck time is administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency’s scientific partnership with the California Institute of Technology and the University of California.

Source: W. M. Keck Observatory/News

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About ADAPTIVE OPTICS

W. M. Keck Observatory is a distinguished leader in the field of adaptive optics (AO), a breakthrough technology that removes the distortions caused by the turbulence in the Earth’s atmosphere. Keck Observatory pioneered the astronomical use of both natural guide star (NGS) and laser guide star adaptive optics (LGS AO) and current systems now deliver images three to four times sharper than the Hubble Space Telescope at near-infrared wavelengths. AO has imaged the four massive planets orbiting the star HR8799, measured the mass of the giant black hole at the center of our Milky Way Galaxy, discovered new supernovae in distant galaxies, and identified the specific stars that were their progenitors. Support for this technology was generously provided by the Gordon and Betty Moore Foundation, Mt. Cuba Astronomical Foundation, NASA, NSF, and W. M. Keck Foundation.

About NIRC2

The Near-Infrared Camera, second generation (NIRC2) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the center of our galaxy. Astronomers also use NIRC2 to map surface features of solar system bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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VLA Detects Possible Extrasolar Planetary-Mass Magnetic Powerhouse

Artist's conception of SIMP J01365663+0933473, an object with 12.7 times the mass of Jupiter, but a magnetic field 200 times more powerful than Jupiter's. This object is 20 light-years from Earth. Credit: Chuck Carter, NRAO/AUI/NSF.  Hi-res image

Object is at boundary between giant planet and brown dwarf

Astronomers using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) have made the first radio-telescope detection of a planetary-mass object beyond our Solar System. The object, about a dozen times more massive than Jupiter, is a surprisingly strong magnetic powerhouse and a “rogue,” traveling through space unaccompanied by any parent star.

“This object is right at the boundary between a planet and a brown dwarf, or ‘failed star,’ and is giving us some surprises that can potentially help us understand magnetic processes on both stars and planets,” said Melodie Kao, who led this study while a graduate student at Caltech, and is now a Hubble Postdoctoral Fellow at Arizona State University.

Brown dwarfs are objects too massive to be considered planets, yet not massive enough to sustain nuclear fusion of hydrogen in their cores — the process that powers stars. Theorists suggested in the 1960s that such objects would exist, but the first one was not discovered until 1995. They originally were thought to not emit radio waves, but in 2001 a VLA discovery of radio flaring in one revealed strong magnetic activity.

Subsequent observations showed that some brown dwarfs have strong auroras, similar to those seen in our own Solar System’s giant planets. The auroras seen on Earth are caused by our planet’s magnetic field interacting with the solar wind. However, solitary brown dwarfs do not have a solar wind from a nearby star to interact with. How the auroras are caused in brown dwarfs is unclear, but the scientists think one possibility is an orbiting planet or moon interacting with the brown dwarf’s magnetic field, such as what happens between Jupiter and its moon Io.

The strange object in the latest study, called SIMP J01365663+0933473, has a magnetic field more than 200 times stronger than Jupiter’s. The object was originally detected in 2016 as one of five brown dwarfs the scientists studied with the VLA to gain new knowledge about magnetic fields and the mechanisms by which some of the coolest such objects can produce strong radio emission. Brown dwarf masses are notoriously difficult to measure, and at the time, the object was thought to be an old and much more massive brown dwarf.

Last year, an independent team of scientists discovered that SIMP J01365663+0933473 was part of a very young group of stars. Its young age meant that it was in fact so much less massive that it could be a free-floating planet — only 12.7 times more massive than Jupiter, with a radius 1.22 times that of Jupiter. At 200 million years old and 20 light-years from Earth, the object has a surface temperature of about 825 degrees Celsius, or more than 1500 degrees Fahrenheit. By comparison, the Sun’s surface temperature is about 5,500 degrees Celsius.

The difference between a gas giant planet and a brown dwarf remains hotly debated among astronomers, but one rule of thumb that astronomers use is the mass below which deuterium fusion ceases, known as the “deuterium-burning limit”, around 13 Jupiter masses.

Simultaneously, the Caltech team that originally detected its radio emission in 2016 had observed it again in a new study at even higher radio frequencies and confirmed that its magnetic field was even stronger than first measured.

“When it was announced that SIMP J01365663+0933473 had a mass near the deuterium-burning limit, I had just finished analyzing its newest VLA data,” said Kao.

The VLA observations provided both the first radio detection and the first measurement of the magnetic field of a possible planetary mass object beyond our Solar System.

Such a strong magnetic field “presents huge challenges to our understanding of the dynamo mechanism that produces the magnetic fields in brown dwarfs and exoplanets and helps drive the auroras we see,” said Gregg Hallinan, of Caltech.

“This particular object is exciting because studying its magnetic dynamo mechanisms can give us new insights on how the same type of mechanisms can operate in extrasolar planets — planets beyond our Solar System. We think these mechanisms can work not only in brown dwarfs, but also in both gas giant and terrestrial planets,” Kao said.

“Detecting SIMP J01365663+0933473 with the VLA through its auroral radio emission also means that we may have a new way of detecting exoplanets, including the elusive rogue ones not orbiting a parent star,” Hallinan said.

Kao and Hallinan worked with J. Sebastian Pineda who also was a graduate student at Caltech and is now at the University of Colorado Boulder, David Stevenson of Caltech, and Adam Burgasser of the University of California San Diego. They are reporting their findings in the Astrophysical Journal.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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Media Contact:

Dave Finley, Public Information Officer
(575) 835-7302
dfinley@nrao.edu

Source: National Radio Astronomy Observatory (NRAO)/News

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Kepler Solves Mystery of Fast and Furious Explosions

Model for the Creation of a Fast-Evolving Luminous Transient

This illustration shows a proposed model for a mysterious astronomical event called a Fast-Evolving Luminous Transient (FELT). In the left panel, an aging red giant star loses mass via a stellar wind. This balloons into a huge gaseous shell around the star. In the center panel, the massive star’s core implodes to trigger a supernova explosion. In the right panel, the supernova shockwave plows into the outer shell, converting the kinetic energy from the explosion into a brilliant burst of light. The flash of radiation lasts for only a few days — one-tenth the duration of a typical supernova explosion.  Credit:  Illustration: NASA, ESA, and A. Feild (STScI) - Science: NASA, ESA, and A. Rest (STScI).  Release images

The universe is full of mysterious exploding phenomena that go boom in the dark. One particular type of ephemeral event, called a Fast-Evolving Luminous Transient (FELT), has bewildered astronomers for a decade because of its very brief duration.

Now, NASA’s Kepler Space Telescope — designed to go hunting for planets across our galaxy — has also been used to catch FELTs in the act and determine their nature. They appear to be a new kind of supernova that gets a brief turbo boost in brightness from its surroundings.

Kepler's ability to precisely sample sudden changes in starlight has allowed astronomers to quickly arrive at this model for explaining FELTs, and rule out alternative explanations.

Researchers conclude that the source of the flash is from a star after it collapses to explode as a supernova. The big difference is that the star is cocooned inside one or more shells of gas and dust. When the tsunami of explosive energy from the blast slams into the shell, most of the kinetic energy is immediately converted to light. The burst of radiation lasts for only a few days — one-tenth the duration of a typical supernova explosion.

Over the past decade several FELTs have been discovered with timescales and luminosities not easily explained by traditional supernova models. And, only a few FELTs have been seen in sky surveys because they are so brief. Unlike Kepler, which collects data on a patch of sky every 30 minutes, most other telescopes look every few days. Therefore they often slip through undetected or with only one or two measurements, making understanding the physics of these explosions tricky.

In the absence of more data, there have been a variety of theories to explain FELTs: the afterglow of a gamma-ray burst, a supernova boosted by a magnetar (neutron star with a powerful magnetic field), or a failed Type Ia supernova.

Then along came Kepler with its precise, continuous measurements that allowed astronomers to record more details of the FELT event. "We collected an awesome light curve," said Armin Rest of the Space Telescope Science Institute in Baltimore, Maryland. "We were able to constrain the mechanism and the properties of the blast. We could exclude alternate theories and arrive at the dense-shell model explanation. This is a new way for massive stars to die and distribute material back into space.

"With Kepler, we are now really able to connect the models with the data," he continued. "Kepler just makes all the difference here. When I first saw the Kepler data, and realized how short this transient is, my jaw dropped. I said, 'Oh wow!'"

"The fact that Kepler completely captured the rapid evolution really constrains the exotic ways in which stars die. The wealth of data allowed us to disentangle the physical properties of the phantom blast, such as how much material the star expelled at the end of its life and the hypersonic speed of the explosion. This is the first time that we can test FELT models to a high degree of accuracy and really connect theory to observations," said David Khatami of the University of California at Berkeley and Lawrence Berkeley National Laboratory.

This discovery is an unexpected spinoff of Kepler’s unique capability to sample changes in starlight continuously for several months. This capability is needed for Kepler to discover extrasolar planets that briefly pass in front of their host stars, temporarily dimming starlight by a small percent.

The Kepler observations indicate that the star ejected the shell less than a year before it went supernova. This gives insight into the poorly understood death throes of stars — the FELTs apparently come from stars that undergo "near-death experiences" just before dying, belching out shells of matter in mini-eruptions before exploding entirely.

The science team's study appears in the March 26, 2018 online issue of Nature Astronomy.

Rest says the next steps will be to find more of these objects in the ongoing K2 mission, or in the next mission of that kind, TESS. This will allow astronomers to start a follow-up campaign spanning different wavelength regimes, which constrains the nature and physics of this new kind of explosion.

NASA's Ames Research Center at Moffett Field, California, manages the Kepler and K2 missions for NASA's Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace and Technologies Corp. operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder, Colorado. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, archives, hosts, and distributes Kepler science data. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.


Related Links

This site is not responsible for content found on external links

• The science paper by A. Rest et al.
• NASA's Kepler Feature Story
• NASA's Kepler Portal

Contacts

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

Armin Rest
Space Telescope Science Institute, Baltimore, Maryland
410-338-4358
arest@stsci.edu

Source: HubbleSite/News

Hubble Observes Exoplanet that Snows Sunscreen

Kepler-13Ab Artist's Concept
Artwork: NASA, ESA, and G. Bacon (STScI)
Science: NASA, ESA, and T. Beatty (Pennsylvania State University)

This is an artist’s impression of the gas giant planet Kepler-13Ab as compared in size to several of our solar system planets. The behemoth exoplanet is six times more massive than Jupiter. Kepler-13Ab is also one of the hottest known planets, with a dayside temperature of nearly 5,000 degrees Fahrenheit. It orbits very close to the star Kepler-13A, which lies at a distance of 1,730 light-years from Earth.  Credits: NASA, ESA, and A. Feild (STScI)

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NASA's Hubble Space Telescope has found a blistering hot planet outside our solar system where it "snows" sunscreen. The problem is the sunscreen (titanium oxide) precipitation only happens on the planet's permanent nighttime side. Any possible visitors to the exoplanet, called Kepler-13Ab, would need to bottle up some of that sunscreen, because they won't find it on the sizzling hot, daytime side, which always faces its host star.

Hubble astronomers suggest that powerful winds carry the titanium oxide gas around to the colder nighttime side, where it condenses into crystalline flakes, forms clouds, and precipitates as snow. Kepler-13Ab's strong surface gravity — six times greater than Jupiter's — pulls the titanium oxide snow out of the upper atmosphere and traps it in the lower atmosphere.

Astronomers using Hubble didn't look for titanium oxide specifically. Instead, they observed that the giant planet's atmosphere is cooler at higher altitudes, which is contrary to what was expected. This finding led the researchers to conclude that a light-absorbing gaseous form of titanium oxide, commonly found in this class of star-hugging, gas giant planet known as a "hot Jupiter," has been removed from the dayside's atmosphere. 

The Hubble observations represent the first time astronomers have detected this precipitation process, called a "cold trap," on an exoplanet.

Without the titanium oxide gas to absorb incoming starlight on the daytime side, the atmospheric temperature grows colder with increasing altitude. Normally, titanium oxide in the atmospheres of hot Jupiters absorbs light and reradiates it as heat, making the atmosphere grow warmer at higher altitudes.

These kinds of observations provide insight into the complexity of weather and atmospheric composition on exoplanets, and may someday be applicable to analyzing Earth-size planets for habitability.

"In many ways, the atmospheric studies we're doing on hot Jupiters now are testbeds for how we're going to do atmospheric studies on terrestrial, Earth-like planets," said lead researcher Thomas Beatty of Pennsylvania State University in University Park. "Hot Jupiters provide us with the best views of what climates on other worlds are like. Understanding the atmospheres on these planets and how they work, which is not understood in detail, will help us when we study these smaller planets that are harder to see and have more complicated features in their atmospheres."

Beatty's team selected Kepler-13Ab because it is one of the hottest of the known exoplanets, with a dayside temperature of nearly 5,000 degrees Fahrenheit. Past observations of other hot Jupiters have revealed that the upper atmospheres increase in temperature. Even at their much colder temperatures, most of our solar system's gas giants also exhibit this phenomenon. 

Kepler-13Ab is so close to its parent star that it is tidally locked. One side of the planet always faces the star; the other side is in permanent darkness. (Similarly, our moon is tidally locked to Earth; only one hemisphere is permanently visible from Earth.)

The observations confirm a theory from several years ago that this kind of precipitation could occur on massive, hot planets with powerful gravity.

"Presumably, this precipitation process is happening on most of the observed hot Jupiters, but those gas giants all have lower surface gravities than Kepler-13Ab," Beatty explained. "The titanium oxide snow doesn't fall far enough in those atmospheres, and then it gets swept back to the hotter dayside, revaporizes, and returns to a gaseous state."

The researchers used Hubble's Wide Field Camera 3 to conduct spectroscopic observations of the exoplanet's atmosphere in near-infrared light. Hubble made the observations as the distant world traveled behind its star, an event called a secondary eclipse. This type of eclipse yields information on the temperature of the constituents in the atmosphere of the exoplanet's dayside. 

"These observations of Kepler-13Ab are telling us how condensates and clouds form in the atmospheres of very hot Jupiters, and how gravity will affect the composition of an atmosphere," Beatty explained. "When looking at these planets, you need to know not only how hot they are but what their gravity is like."

The Kepler-13 system resides 1,730 light-years from Earth.

The team's results appeared in The Astronomical Journal

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Related Links

This site is not responsible for content found on external links

• The science paper by T. Beatty et al.
• NASA's Hubble Portal
• Pennsylvania State University's Release

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Contact

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Thomas Beatty
Pennsylvania State University, University Park
814-863-7346
tbeatty@psu.edu

Source: HubbleSite/News

Hubble Detects Exoplanet with Glowing Water Atmosphere

Artist's View of WASP-121b
Illustration: NASA, ESA, and G. Bacon (STScI)
Credits: Science: NASA, ESA, and T. Evans (University of Exeter)

Comparison of WASP-121b Stratosphere with Brown Dwarf Atmosphere

Credits: Illustration: NASA, ESA, and A. Feild (STScI)

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Scientists have discovered the strongest evidence to date for a stratosphere on a planet outside our solar system, or exoplanet. A stratosphere is a layer of atmosphere in which temperature increases with higher altitudes.

"This result is exciting because it shows that a common trait of most of the atmospheres in our solar system — a warm stratosphere — also can be found in exoplanet atmospheres," said Mark Marley, study co-author based at NASA's Ames Research Center in California's Silicon Valley. "We can now compare processes in exoplanet atmospheres with the same processes that happen under different sets of conditions in our own solar system."

Reporting in the journal Nature, scientists used data from NASA's Hubble Space Telescope to study WASP-121b, a type of exoplanet called a "hot Jupiter." Its mass is 1.2 times that of Jupiter, and its radius is about 1.9 times Jupiter's — making it puffier. But while Jupiter revolves around our sun once every 12 years, WASP-121b has an orbital period of just 1.3 days. This exoplanet is so close to its star that if it got any closer, the star's gravity would start ripping it apart. It also means that the top of the planet's atmosphere is heated to a blazing 4,600 degrees Fahrenheit (2,500 degrees Celsius), hot enough to boil some metals. The WASP-121 system is estimated to be about 900 light-years from Earth — a long way, but close by galactic standards.

Previous research found possible signs of a stratosphere on the exoplanet WASP-33b as well as some other hot Jupiters. The new study presents the best evidence yet because of the signature of hot water molecules that researchers observed for the first time.

"Theoretical models have suggested stratospheres may define a distinct class of ultra-hot planets, with important implications for their atmospheric physics and chemistry," said Tom Evans, lead author and research fellow at the University of Exeter, United Kingdom. "Our observations support this picture."

To study the stratosphere of WASP-121b, scientists analyzed how different molecules in the atmosphere react to particular wavelengths of light, using Hubble's capabilities for spectroscopy. Water vapor in the planet's atmosphere, for example, behaves in predictable ways in response to certain wavelengths of light, depending on the temperature of the water.

Starlight is able to penetrate deep into a planet's atmosphere, where it raises the temperature of the gas there. This gas then radiates its heat into space as infrared light. However, if there is cooler water vapor at the top of the atmosphere, the water molecules will prevent certain wavelengths of this light from escaping to space. But if the water molecules at the top of the atmosphere have a higher temperature, they will glow at the same wavelengths.

"The emission of light from water means the temperature is increasing with height," said Tiffany Kataria, study co-author based at NASA's Jet Propulsion Laboratory, Pasadena, California. "We’re excited to explore at what longitudes this behavior persists with upcoming Hubble observations."

The phenomenon is similar to what happens with fireworks, which get their colors from chemicals emitting light. When metallic substances are heated and vaporized, their electrons move into higher energy states. Depending on the material, these electrons will emit light at specific wavelengths as they lose energy: sodium produces orange-yellow and strontium produces red in this process, for example. The water molecules in the atmosphere of WASP-121b similarly give off radiation as they lose energy, but in the form of infrared light, which the human eye is unable to detect.

In Earth's stratosphere, ozone gas traps ultraviolet radiation from the sun, which raises the temperature of this layer of atmosphere. Other solar system bodies have stratospheres, too; methane is responsible for heating in the stratospheres of Jupiter and Saturn's moon Titan, for example.

In solar system planets, the change in temperature within a stratosphere is typically around 100 degrees Fahrenheit (about 56 degrees Celsius). On WASP-121b, the temperature in the stratosphere rises by 1,000 degrees (560 degrees Celsius). Scientists do not yet know what chemicals are causing the temperature increase in WASP-121b's atmosphere. Vanadium oxide and titanium oxide are candidates, as they are commonly seen in brown dwarfs, "failed stars" that have some commonalities with exoplanets. Such compounds are expected to be present only on the hottest of hot Jupiters, as high temperatures are needed to keep them in a gaseous state.

"This super-hot exoplanet is going to be a benchmark for our atmospheric models, and it will be a great observational target moving into the Webb era," said Hannah Wakeford, study co-author who worked on this research while at NASA's Goddard Space Flight Center, Greenbelt, Maryland.

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, Inc., in Washington, D.C. The California Institute of Technology (Caltech) manages the Jet Propulsion Laboratory (JPL) for NASA.

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Links

This site is not responsible for content found on external links

• The science paper by T. Evans et al.
• NASA's Hubble Portal
• Journal Nature
• NASA JPL's Feature Story
• NASA's Exoplanets Portal
• University of Exeter's Release

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Contacts
Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, California
818-354-6425
elizabeth.landau@jpl.nasa.gov
 
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

Source: HubbleSite

Mini-Flares Potentially Jeopardize Habitability of Planets Circling Red Dwarf Stars

Flaring Red Dwarf Star (Artist's Illustration)

Credit: NASA, ESA, and G. Bacon (STScI)

 Release image

Cool dwarf stars are hot targets for exoplanet hunting right now. The discoveries of planets in the habitable zones of the TRAPPIST-1 and LHS 1140 systems, for example, suggest that Earth-sized worlds might circle billions of red dwarf stars, the most common type of star in our galaxy. But, like our own sun, many of these stars erupt with intense flares. Are red dwarfs really as friendly to life as they appear, or do these flares make the surfaces of any orbiting planets inhospitable?

To address this question, a team of scientists has combed 10 years of ultraviolet observations by the Galaxy Evolution Explorer (GALEX) spacecraft looking for rapid increases in the brightnesses of stars due to flares. Flares emit radiation across a wide swath of wavelengths, with a significant fraction of their total energy released in the ultraviolet bands where GALEX observed. At the same time, the red dwarfs from which the flares arise are relatively dim in the ultraviolet. This contrast, combined with the time resolution of the GALEX detectors, allowed the team to measure events with less total energy than many previously detected flares. This is important because, although individually less energetic and therefore less hostile to life, smaller flares might be much more frequent and add up over time to produce an inhospitable environment.

“What if planets are constantly bathed by these smaller, but still significant, flares?” asked Scott Fleming of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “There could be a cumulative effect.”

To detect and accurately measure these flares, the team had to slice the GALEX data into very high time resolution. From images with exposure times of nearly half an hour, the team was able to reveal stellar variations lasting just seconds.

First author Chase Million of Million Concepts in State College, Pennsylvania, led a project called gPhoton that reprocessed more than 100 terabytes of GALEX data held at the Mikulski Archive for Space Telescopes (MAST), located at STScI. The team then used custom software developed by Million and Clara Brasseur (STScI) to search several hundred red dwarf stars and detected dozens of flares.

“We have found dwarf star flares in the whole range that we expected GALEX to be sensitive to, from itty bitty baby flares that last a few seconds, to monster flares that make a star hundreds of times brighter for a few minutes,” said Million.

The flares GALEX detected are similar in strength to flares produced by our own sun. However, because a planet would have to orbit much closer to a cool, red dwarf star to maintain a temperature friendly to life as we know it, such planets would be subjected to more of a flare’s energy than Earth.

Large flares can strip away a planet’s atmosphere. Strong ultraviolet light from flares that penetrates to a planet’s surface could damage organisms or prevent life from arising.

Currently, team members Rachel Osten (STScI) and Brasseur are examining stars observed by both the GALEX and Kepler missions to look for similar flares. The team expects to eventually find hundreds of thousands of flares hidden in the GALEX data.

"These results show the value of a survey mission like GALEX, which was instigated to study the evolution of galaxies across cosmic time and is now having an impact on the study of nearby habitable planets," said Don Neill, research scientist at Caltech in Pasadena, California, who was part of the GALEX collaboration. "We did not anticipate that GALEX would be used for exoplanets when the mission was designed."

New and powerful instruments like the James Webb Space Telescope, scheduled for launch in 2018, ultimately will be needed to study atmospheres of planets orbiting nearby red dwarf stars and search for signs of life. But as researchers pose new questions about the cosmos, archives of data from past projects and missions, like those held at MAST, continue to produce exciting new scientific results.

These results were presented in a press conference at a meeting of the American Astronomical Society in Austin, Texas.

The GALEX mission, which ended in 2013 after more than a decade of scanning the skies in ultraviolet light, was led by scientists at Caltech. NASA's Jet Propulsion Laboratory, also in Pasadena, California, managed the mission and built the science instrument. JPL is managed by Caltech for NASA.

The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble Space Telescope science operations and is the mission and science operations center for the James Webb Space Telescope. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

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Contacts

Christine Pulliam / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4366 / 410-338-4514
cpulliam@stsci.edu / villard@stsci.edu

Chase Million
Million Concepts, State College, Pennsylvania
765-914-5336
chase.million@gmail.com

Source: HubbleSite

Hubble Captures 'Shadow Play' Caused by Possible Planet

TW Hydrae

Credits: NASA, ESA, and J. Debes (STScI)

Hi-re images

Release Videos

Searching for planets around other stars is a tricky business. They're so small and faint that it's hard to spot them. But a possible planet in a nearby stellar system may be betraying its presence in a unique way: by a shadow that is sweeping across the face of a vast pancake-shaped gas-and-dust disk surrounding a young star.

The planet itself is not casting the shadow. But it is doing some heavy lifting by gravitationally pulling on material near the star and warping the inner part of the disk. The twisted, misaligned inner disk is casting its shadow across the surface of the outer disk.

A team of astronomers led by John Debes of the Space Telescope Science Institute in Baltimore, Maryland, say this scenario is the most plausible explanation for the shadow they spotted in the stellar system TW Hydrae, located 192 light-years away in the constellation Hydra, also known as the Female Water Snake. The star is roughly 8 million years old and slightly less massive than our sun. The researchers uncovered the phenomenon while analyzing 18 years' worth of archival observations taken by NASA's Hubble Space Telescope.

"This is the very first disk where we have so many images over such a long period of time, therefore allowing us to see this interesting effect," Debes said. "That gives us hope that this shadow phenomenon may be fairly common in young stellar systems."

Debes will present his team's results Jan. 7 at the winter meeting of the American Astronomical Society in Grapevine, Texas.

Debes' first clue to the phenomenon was a brightness in the disk that changed with position. Astronomers using Hubble's Space Telescope Imaging Spectrograph (STIS) first noted this brightness asymmetry in 2005. But they had only one set of observations, and could not make a definitive determination about the nature of the mystery feature.

Searching the archive, Debes' team put together six images from several different epochs. The observations were made by STIS and by Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

STIS is equipped with a coronagraph that blocks starlight to within about 1 billion miles from the star, allowing Hubble to look as close to the star as Saturn is to our sun. Over time, the structure appeared to move in counterclockwise fashion around the disk, until, in 2016, it was in the same position as it was in images taken in 2000.

This 16-year period puzzled the researchers. They originally thought the feature was part of the disk, but the short period meant that the feature was moving way too fast to be physically in the disk.

Under the laws of gravity, disks rotate at glacial speeds. The outermost parts of the TW Hydrae disk would take centuries to complete one rotation.

"The fact that I saw the same motion over 10 billion miles from the star was pretty significant, and told me that I was seeing something that was imprinted on the outer disk rather than something that was happening directly in the disk itself," Debes said. "The best explanation is that the feature is a shadow moving across the surface of the disk."

The research team concluded that whatever was making the shadow must be deep inside the 41-billion-mile-wide disk, so close to the star it cannot be imaged by Hubble or any other present-day telescope. The most likely way to create a shadow is to have an inner disk that is tilted relative to the outer disk. In fact, submillimeter observations of TW Hydrae by the Atacama Large Millimeter Array (ALMA) in Chile suggested a possible warp in the inner disk.

But what causes disks to warp? "The most plausible scenario is the gravitational influence of an unseen planet, which is pulling material out of the plane of the disk and twisting the inner disk," Debes explained. "The misaligned disk is inside the planet's orbit."

Given the relatively short 16-year period of the clocklike moving shadow, the planet is estimated to be about 100 million miles from the star — about as close as Earth is from the sun. The planet would be roughly the size of Jupiter to have enough gravity to pull the material up out of the plane of the main disk. The planet's gravitational pull causes the disk to wobble, or precess, around the star, giving the shadow its 16-year rotational period.

Recent observations of TW Hydrae by ALMA in Chile add credence to the presence of a planet. ALMA revealed a gap in the disk roughly 9 million miles from TW Hydrae. A gap is significant, because it could be the signature of an unseen planet clearing away a path in the disk.

This new Hubble study offers a unique way to look for planets hiding in the inner part of the disk and probe what is happening very close to the star, which is not reachable in direct imaging by current telescopes. "What is surprising is that we can learn something about an unseen part of the disk by studying the disk's outer region and by measuring the motion, location, and behavior of a shadow," Debes said. "This study shows us that even these large disks, whose inner regions are unobservable, are still dynamic, or changing in detectable ways which we didn't imagine."

The Hubble Space Telescope is a project of international cooperation between NASA and the 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.

Contact

Felicia Chou
NASA Headquarters, Washington, D.C.
202-358-0257
felicia.chou@nasa.gov

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

John Debes
Space Telescope Science Institute, Baltimore, Maryland
410-338-4782
debes@stsci.edu

Source: HubbleSite

The weird system of star CVSO 30: two planets at extreme distances

A direct image has been taken of a planet so far away from his star that it takes twenty-seven thousand years for completing one orbit, and it shares the system with another planet which completes its orbit in just eleven hours.

The planet CVSO 30c seen to the left of its star.

Credit:  Keck II telescope (left image) and (right image) VLT (ESO / Schmidt et al.)

 

An international observation campaign has allowed to photograph a planet around CVSO 30 star which is part of a curious system: the newly found CVSO 30c orbits the star at a extreme distance (more than twenty times the distance between Neptune and the Sun), and contrasts with its partner CVSO 30b, found in 2012, that is only at 1.2 million kilometers from the star (Mercury, the planet closest to the Sun, is 58 million kilometers away from it). It is the first system found with these characteristics, and their weird orbits could be due to the fact that both planets interacted to each other in the past and there was a dispersion process.

Up to now, most of the more than two thousand found planets orbiting other stars have been detected thanks to indirect methods, which study the influence of the planets on their stars. Barely sixty have been found with direct imaging, a very instrumental demanding method, but allowing exploring remote regions of the star where indirect methods are less effective.

The confirmation that the little dot on the images was indeed a planet has been possible thanks to the combined use of Keck (Hawaii), VLT (Chile) and Calar Alto Observatory telescopes. “CVSO 30c has been a surprise as it is at 660 Astronomical Units - an Astronomical Unit, or AU, is equivalent to hundred and fifty million kilometers, the distance between the Earth and the Sun -.  Neptune is the most external planet of our Solar System, and it is at 30 AUs” , Jesús Aceituno, Calar Alto Observatory (CAHA, MPG/CSIC) Deputy Director points.

A unique system

Besides, this planet shares system with another one found in 2012 through indirect methods. Although both planets have a similar mass (between one and four times the mass of Jupiter), both of them have a relative distance never saw in the planetary system found up to now: while one is as close to its star that it completes its orbit in barely eleven hours, the other takes about twenty-seven thousand years for finishing it.

Researchers think about several possibilities in order to explain this distance disparity, but the most probable explanation points to the fact that both planets were formed within the internal regions of the system, and a gravitational interaction, happened in the past, resulted in the dispersion. This is a mechanism invoked to explain what are known as “Hot Jupiters”, gas giants very close to its star and which its detection constituted a surprise: in so short distances, the temperature prevents condensation of volatile ice to form gaseous planets, so they should have migrated to the inner regions by orbital resonances with other bodies.

This planetary system is a suitable object for studying these planetary dispersion theories, as well as for inquire on the first planet development phases: CVSO 30 star is a very young one, with only 2.5 million years (our Sun has 5 million years), and researchers are studying how it could form planets so quickly.

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The German-Spanish Calar Alto Observatory is located at Sierra de los Filabres, north of Almería (Andalucía, Spain). It is jointly operated by the Instituto Max Planck de Astronomía in Heidelberg, Germany, and the Instituto de Astrofísica de Andalucía (CSIC) in Granada, Spain. Calar Alto has three telescopes with apertures of 1.23m, 2.2m and 3.5m. A 1.5m aperture telescope, also located at the mountain, is operated under control of the Observatorio de Madrid.

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Reference:

T.O.B. Schmidt et al. "Direct Imaging discovery of a second planet candidate around the possibly transiting planet host CVSO 30 ⋆". Astronomy & Astrophysics. DOI: http://dx.doi.org/10.1051/0004-6361/201526326

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Contact:

Instituto de Astrofísica de Andalucía (IAA-CSIC)
Unidad de Divulgación y Comunicación
Silbia López de Lacalle - sll[arroba]iaa.es - 958230532
http://www.iaa.es
http://www-divulgacion.iaa.es

Source: Instituto de Astrofísica de Andalucía (IAA-CSIC)

Robotically Discovering Earth’s Nearest Neighbors

Artist’s impression of a view from the HD 7924 planetary system looking back toward our sun, which would be easily visible to the naked eye. Since HD 7924 is in our northern sky, an observer looking back at the sun would see objects like the Southern Cross and the Magellanic Clouds close to our sun in their sky. Art by Karen Teramura & BJ Fulton, UH IfA.

A team of astronomers using ground-based telescopes in Hawaii, California, and Arizona recently discovered a planetary system orbiting a nearby star that is only 54 light-years away. All three planets orbit their star at a distance closer than Mercury orbits the sun, completing their orbits in just 5, 15, and 24 days.

Astronomers from the University of Hawaii at Manoa, the University of California, Berkeley, the University of California Observatories, and Tennessee State University found the planets using measurements from the Automated Planet Finder (APF) Telescope at Lick Observatory in California, the W. M. Keck Observatory on Maunakea, Hawaii, and the Automatic Photometric Telescope (APT) at Fairborn Observatory in Arizona. 

The team discovered the new planets by detecting the wobble of the star HD 7924 as the planets orbited and pulled on the star gravitationally. APF and Keck Observatory traced out the planets’ orbits over many years using the Doppler technique that has successfully found hundreds of mostly larger planets orbiting nearby stars. APT made crucial measurements of the brightness of HD 7924 to assure the validity of the planet discoveries.

The new APF facility offers a way to speed up the planet search. Planets can be discovered and their orbits traced much more quickly because APF is a dedicated facility that robotically searches for planets every clear night. Training computers to run the observatory all night, without human oversight, took years of effort by the University of California Observatories staff and graduate students on the discovery team.

“We initially used APF like a regular telescope, staying up all night searching star to star. But the idea of letting a computer take the graveyard shift was more appealing after months of little sleep. So we wrote software to replace ourselves with a robot,” said University of Hawaii graduate student BJ Fulton.

The Keck Observatory found the first evidence of planets orbiting HD 7924, discovering the innermost planet in 2009 using the HIRES instrument installed on the 10-meter Keck I telescope. This same combination was also used to find other super-Earths orbiting nearby stars in planet searches led by UH astronomer Andrew Howard and UC Berkeley Professor Geoffrey Marcy. It took five years of additional observations at Keck Observatory and the year-and-a-half campaign by the APF Telescope to find the two additional planets orbiting HD 7924.

The Kepler Space Telescope has discovered thousands of extrasolar planets and demonstrated that they are common in our Milky Way galaxy. However, nearly all of these planets are far from our solar system. Most nearby stars have not been thoroughly searched for the small “super-Earth” planets (larger than Earth but smaller than Neptune) that Kepler found in great abundance.

This discovery shows the type of planetary system that astronomers expect to find around many nearby stars in the coming years. “The three planets are unlike anything in our solar system, with masses 7-8 times the mass of Earth and orbits that take them very close to their host star,” explains UC Berkeley graduate student Lauren Weiss. 

“This level of automation is a game-changer in astronomy,” says Howard. “It’s a bit like owning a driverless car that goes planet shopping.”

Observations by APF, APT, and Keck Observatory helped verify the planets and rule out other explanations. “Starspots, like sunspots on the sun, can momentarily mimic the signatures of small planets. Repeated observations over many years allowed us to separate the starspot signals from the signatures of these new planets,” explains Evan Sinukoff, a UH graduate student who contributed to the discovery.

The robotic observations of HD 7924 are the start of a systematic survey for super-Earth planets orbiting nearby stars. Fulton will lead this two-year search with the APF as part of his research for his doctoral dissertation. “When the survey is complete we will have a census of small planets orbiting sun-like stars within approximately 100 light-years of Earth,” says Fulton. 

Telescope automation is relatively new to astronomy, and UH astronomers are building two forefront facilities. Christoph Baranec built the Robo-AO observatory to takes high-resolution images using a laser to remove the blur of Earth’s atmosphere, and John Tonry is developing ATLAS, a robotic observatory that will hunt for killer asteroids. 

The paper presenting this work, “Three super-Earths orbiting HD 7924,” has been accepted for publication in the Astrophysical Journal and is available at no cost at http://arxiv.org/abs/1504.06629. The other authors of the paper are Howard Isaacson (UC Berkeley), Gregory Henry (TSU), and Bradford Holden and Robert I. Kibrick (UCO).

In honor of the donations of Gloria and Ken Levy that helped facilitate the construction of the Levy spectrograph on APF and supported Lauren Weiss, the team has informally named the HD 7924 system the “Levy Planetary System.” The team also acknowledges the support of NASA, the U.S. Naval Observatory, and the University of California for its support of Lick Observatory. 

Contacts:

BJ Fulton
bfulton@hawaii.edu
+1 408-528-4858

Dr. Andrew Howard
howard@ifa.hawaii.edu
+1 808-208-1224

Ms. Louise Good
Media Contact
+1 808-381-2939
good@ifa.hawaii.edu

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Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Maunakea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii.

Source:  Institute for Astronomy at the University of Hawaii

Tau Ceti: The next Earth? Probably not

How would an alien world like this look? That’s the question that undergraduate art major Joshua Gonzalez attempted to answer. He worked with Professor Patrick Young’s group to learn how to analyze stellar spectra to find chemical abundances, and inspired by the scientific results, he created two digital paintings of possible unusual extrasolar planets, one being Tau Ceti for his Barrett Honors Thesis. Credit: Joshua Gonzalez.

The list of potential life-supporting planets just got a little shorter

 

As the search continues for Earth-size planets orbiting at just the right distance from their star, a region termed the habitable zone, the number of potentially life-supporting planets grows. In two decades we have progressed from having no extrasolar planets to having too many to search. Narrowing the list of hopefuls requires looking at extrasolar planets in a new way. Applying a nuanced approach that couples astronomy and geophysics, Arizona State University researchers report that from that long list we can cross off cosmic neighbor Tau Ceti.

The Tau Ceti system, popularized in several fictional works, including Star Trek, has long been used in science fiction, and even popular news, as a very likely place to have life due to its proximity to Earth and the star’s sun-like characteristics. Since December 2012 Tau Ceti has become even more appealing, thanks to evidence of possibly five planets orbiting it, with two of these – Tau Ceti e and f – potentially residing in the habitable zone.

Using the chemical composition of Tau Ceti, the ASU team modeled the star’s evolution and calculated its habitable zone. Although their data confirms that two planets (e and f) may be in the habitable zone it doesn’t mean life flourishes or even exists there.

“Planet e is in the habitable zone only if we make very generous assumptions. Planet f initially looks more promising, but modeling the evolution of the star makes it seem probable that it has only moved into the habitable zone recently as Tau Ceti has gotten more luminous over the course of its life,” explains astrophysicist Michael Pagano, ASU postdoctoral researcher and lead author of the paper appearing in the Astrophysical Journal. The collaboration also included ASU astrophysicists Patrick Young and Amanda Truitt and mineral physicist Sang-Heon (Dan) Shim.

Based upon the team’s models, planet f has likely been in the habitable zone much less than 1 billion years. This sounds like a long time, but it took Earth’s biosphere about 2 billion years to produce potentially detectable changes in its atmosphere. A planet that entered the habitable zone only a few hundred million years ago may well be habitable and even inhabited, but not have detectable biosignatures.

According to Pagano, he and his collaborators didn’t pick Tau Ceti “hoping, wanting, or thinking” it would be a good candidate to look for life, but for the idea that these might be truly alien new worlds.

Tau Ceti has a highly unusual composition with respect to its ratio of magnesium and silicon, which are two of the most important rock forming minerals on Earth. The ratio of magnesium to silicon in Tau Ceti is 1.78, which is about 70% more than our sun.

The astrophysicists looked at the data and asked, “What does this mean for the planets?”

Building on the strengths of ASU’s School of Earth and Space Exploration, which unites earth and space scientists in an effort to tackle research questions through a holistic approach, Shim was brought on board for his mineral expertise to provide insights into the possible nature of the planets themselves.

“With such a high magnesium and silicon ratio it is possible that the mineralogical make-up of planets around Tau Ceti could be significantly different from that of Earth. Tau Ceti’s planets could very well be dominated by the mineral olivine at shallow parts of the mantle and have lower mantles dominated by ferropericlase,” explains Shim.

Considering that ferropericlase is much less viscous, or resistant to flowing, hot, yet solid, mantle rock would flow more easily, possibly having profound effects on volcanism and tectonics at the planetary surface, processes which have a significant impact on the habitability of Earth.

“This is a reminder that geological processes are fundamental in understanding the habitability of planets,” Shim adds.

“Tau Ceti has been a popular destination for science fiction writers and everyone's imagination as somewhere there could possibly be life, but even though life around Tau Ceti may be unlikely, it should not be seen as a letdown, but should invigorate our minds to consider what exotic planets likely orbit the star, and the new and unusual planets that may exist in this vast universe,” says Pagano.

This work was supported by funding from the NASA Astrobiology Institute and NASA Nexus for Exoplanet System Science.

Written by Nikki Cassis

Source: School of Earth and Space Exploration (SESE) - Arizona State University (ASU)

Three Almost Earth-Size Planets Found Orbiting Nearby Star

This whimsical cartoon shows the three newly discovered extrasolar planets (right) casting shadows on their host star that can been seen as eclipses, or transits, at Earth (left). Earth can be detected by the same effect, but only in the plane of Earth's orbit (the ecliptic). During the K2 mission, many of the extrasolar planets discovered by the Kepler telescope will have this lucky double cosmic alignment that would allow for mutual discovery—if there is anyone on those planets to discover Earth. The three new planets orbiting EPIC 201367065 are just out of alignment; while they are visible from Earth, our solar system is tilted just out of their view.  Credit: K. Teramura, UH IfA. High-resolution version

MAUNA KEA, HI – A team of scientists recently discovered a system of three planets, each just larger than Earth, orbiting a nearby star called EPIC 201367065. The three planets are 1.5-2 times the size of Earth.

The outermost planet orbits on the edge of the so-called “habitable zone,” where the temperature may be just right for liquid water, believed necessary to support life, on the planet’s surface. The paper, “A Nearby M Star with Three Transiting Super-Earths Discovered by K2,” was submitted to the Astrophysical Journal today and is available here.

“The compositions of these newfound planets are unknown, but, there is a very real possibility the outer planet is rocky like Earth,” said Erik Petigura, a University of California, Berkeley graduate student who spent a year visiting the UH Institute for Astronomy. “If so, this planet could have the right temperature to support liquid water oceans.”

The planets were confirmed by the NASA Infrared Telescope Facility (IRTF) and the W. M. Keck Observatory in Hawaii as well as telescopes in California and Chile.

“Keck's contribution to this discovery was vital,” said Andrew Howard, a University of Hawaii astronomer on the team. “The adaptive optics image from NIRC2 showed the star hosting these three planets is a single star, not a binary. It showed that the planets are real and not an artifact of some masquerading multi-star system.”

Due to the competitive state of planet finding, and the fact that time on the twin Keck telescopes are scheduled months in advance, the team asked UC Berkeley Astronomer, Imke de Pater to gather some data during her scheduled run. 

“The collegiality of the Keck Observatory community is just wonderful,” Howard said. “Imke took time away from her own science observations to get us images of this system, all on a couple hours’ notice.”

The new discovery paves the way for studies of the atmosphere of a warm planet nearly the size of Earth. 

“We’ve learned in the past year that planets the size and temperature of Earth are common in our Milky Way galaxy,” Howard said. “We also discovered some Earth-size planets that appear to be made of the same materials as our Earth, mostly rock and iron.”

The astronomers next hope to determine what elements are in the planets’ atmospheres. If these warm, nearly Earth-size planets have thick, hydrogen-rich atmospheres, there is not much chance for life.

“A thin atmosphere made of nitrogen and oxygen has allowed life to thrive on Earth. But nature is full of surprises. Many extrasolar planets discovered by the Kepler Mission are enveloped by thick, hydrogen-rich atmospheres that are probably incompatible with life as we know it,” said Ian Crossfield, the University of Arizona astronomer who led the study.

The discovery is all the more remarkable because Kepler is now hobbled by the loss of two reaction wheels that kept it pointing at a fixed spot in space. Kepler, launched in 2009, was reborn in 2014 as “K2” with a clever strategy of pointing the telescope in the plane of the Earth’s orbit to stabilize the spacecraft. Kepler is back to mining the cosmos for planets by searching for eclipses, or transits, as planets orbit in front of their host stars and periodically block some of the starlight.

“I was devastated when Kepler was crippled by a hardware failure,” Petigura added. “It’s a testament to the ingenuity of NASA engineers and scientists that Kepler can still do great science.”

Kepler sees only a small fraction of the planetary systems in its gaze, those with orbital planes aligned edge-on to our view from Earth. Planets with large orbital tilts are simply missed by Kepler.

“It’s remarkable that the Kepler telescope is now pointed in the ecliptic, the plane that Earth sweeps out as it orbits the Sun,” Fulton explains. “This means that some of the planets discovered by K2 will have orbits lined up with Earth’s, a celestial coincidence that allows Kepler to see the alien planets, and Kepler-like telescopes in those very planetary systems (if there are any) to discover Earth.”

“Here’s looking at you, looking at me,” said Howard.

In addition to Howard and Petigura, UH graduate students Benjamin Fulton and Kimberly Aller, and UH astronomer Michael Liu were among the two dozen scientists who contributed to the study.

The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems. 

NIRC2 (the Near-Infrared Camera, second generation) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the center of our galaxy. Astronomers also use NIRC2 to map surface features of solar system bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.

Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

Media Contact:

Steve Jefferson
Communications Officer
W. M. Keck Observatory
808.881.3827
sjefferson@keck.hawaii.edu

Source: W. M. Keck Observatory