Exoplanets

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Timothy Lyons

Edward Schwieterman

UC Riverside astrophysicist part of TESS planet finder team

Anonymous — Tue, 25 Aug 2020 01:29:49 +0000

UC Riverside astrophysicist part of TESS planet finder team Anonymous (not verified) Mon, 08/24/2020 - 18:29 More News Sarah Nightingale | UCR News April 19, 2018

NASA’s Transiting Exoplanet Survey Satellite (TESS) launched on April 18 from Florida’s Cape Canaveral Air Force Station, rising off the pad aboard a SpaceX Falcon 9 rocket at 3:51 p.m. PDT and deploying into Earth’s orbit 49 minutes later.

Stephen Kane, an associate professor of planetary astrophysics at UC Riverside and a Guest Investigator on the TESS Mission, witnessed the takeoff from the launch viewing site in Cape Canaveral.

The telescope will search for exoplanets — planets outside our solar system — orbiting the brightest stars in the sky, including those that could support life. In a two-year survey of the solar neighborhood, TESS will monitor more than 200,000 stars for temporary drops in brightness caused by planetary transits. Those planets will then be studied in detail through follow-up observations by other ground- and space-based telescopes.

Wednesday’s launch was originally scheduled for Monday, but it was delayed to give SpaceX time to check a potential issue with the rocket’s guidance, navigation, and control systems.

“The spacecraft is reported to be in good health and both solar arrays have been deployed. TESS is now being deployed into its final orbit that will cross the orbit of the moon,” Kane said.

Kane said the TESS mission will pick up the search for exoplanets as the Kepler mission prepares to wind down. Launched in 2009, the Kepler Space Telescope has discovered more than 4,500 potential and confirmed exoplanets. The stars viewed by TESS will be 30-100 times brighter than those surveyed by the Kepler satellite, therefore TESS planets should be much easier to characterize with follow-up observations.

Kane, who led the Kepler Habitable Zone Working Group for the Kepler mission, is a key part of the TESS mission. He has been collaborating with other TESS scientists to create the list of stars that TESS will observe and prepare for observations that will characterize the atmospheres of detected planets.

His team at UCR will be measuring the masses of detected planets as well as studying their orbits and simulating potential habitable conditions. “There are many exciting exoplanet hunting days ahead for UCR and we expect that our astrobiology group will be extremely busy as we use the TESS data to better understand the prevalence of life in the universe,” Kane said.

Kane, a member of UCR’s NASA-funded Alternative Earths Astrobiology Center, is available for media interviews about the launch and his involvement in analyzing TESS data and observations.

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Omega centauri unlikely to harbor life

Anonymous — Tue, 25 Aug 2020 01:07:17 +0000

Omega centauri unlikely to harbor life Anonymous (not verified) Mon, 08/24/2020 - 18:07 More News Sarah Nightingale | UCR News August 09, 2018

Searching for life in the vast universe is an overwhelming task, but scientists can cross one place off their list.

Omega Centauri — a densely packed cluster of stars in our galactic backyard — is unlikely to be home to habitable planets, according to a study by scientists at the University of California, Riverside, and San Francisco State University.

Forthcoming in The Astrophysical Journal, the study was led by Stephen Kane, an associate professor of planetary astrophysics in UCR’s Department of Earth Sciences and a pioneer in the search for habitable planets outside our solar system, known as exoplanets. Sarah Deveny, a graduate student at San Francisco State who is working with Kane, co-authored the paper.

Omega Centauri. NASA, ESA, AND THE HUBBLE ERO TEAM.

In the hunt for habitable exoplanets, Omega Centauri, the largest globular cluster in the Milky Way, seemed like a good place to look. Comprising an estimated 10 million stars, the cluster is nearly 16,000 light years from Earth, making it visible to the naked eye and a relatively close target for observations by the Hubble Space Telescope.

“Despite the large number of stars concentrated in Omega Centauri’s core, the prevalence of exoplanets remains somewhat unknown,” Kane said. “However, since this type of compact star cluster exists across the universe, it is an intriguing place to look for habitability.”

Starting with a rainbow-colored assortment of 470,000 stars in Omega Centauri’s core, the researchers homed in on 350,000 stars whose color — a gauge of their temperature and age — means they could potentially harbor life-bearing planets.

For each star, they then calculated the habitable zone — the orbital region around each star in which a rocky planet could have liquid water, which is a key ingredient for life as we know it. Since most of the stars in Omega Centauri’s core are red dwarfs, their habitable zones are much closer than the one surrounding our own larger sun.

“The core of Omega Centauri could potentially be populated with a plethora of compact planetary systems that harbor habitable-zone planets close to a host star,” Kane said. “An example of such a system is TRAPPIST-1, a miniature version of our own solar system that is 40 light years away and is currently viewed as one of the most promising places to look for alien life.”

Ultimately, though, the cozy nature of stars in Omega Centauri forced the researchers to conclude that such planetary systems, however compact, cannot exist in the cluster’s core. While our own sun is a comfortable 4.22 light years from its nearest neighbor, the average distance between stars in Omega Centauri’s core is 0.16 light years, meaning they would encounter neighboring stars about once every 1 million years.

“The rate at which stars gravitationally interact with each other would be too high to harbor stable habitable planets,” Deveny said. “Looking at clusters with similar or higher encounter rates to Omega Centauri’s could lead to the same conclusion. So, studying globular clusters with lower encounter rates might lead to a higher probability of finding stable habitable planets.”

The title of the paper is “Habitability in the Omega Centauri Cluster.”

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NASA’s TESS mission finds ‘missing link’ planets

Anonymous — Tue, 25 Aug 2020 00:48:19 +0000

NASA’s TESS mission finds ‘missing link’ planets Anonymous (not verified) Mon, 08/24/2020 - 17:48 More News Jules Bernstein | UCR News July 29, 2019

NASA’s newest planet-hunting satellite has discovered a type of planet missing from our own solar system.

Launched in 2018, the Transiting Exoplanet Survey Satellite, or TESS, has found three new worlds around a neighboring star. Stephen Kane, a UC Riverside associate professor of planetary astrophysics, says the new star system, called TESS Object of Interest, or TOI-270, is exactly what the satellite was designed to find.

A paper describing TOI-270 has been published in the journal Nature Astronomy and is now available online. Of the three new exoplanets, meaning they’re outside our solar system, one is rocky and slightly larger than Earth, while the two others are gaseous and roughly twice Earth’s size.

Compare and contrast worlds in the TOI 270 system. (NASA’s Goddard Space Flight Center)

Not only is the smaller planet in the habitable zone — the range of distances from a star that are warm enough to allow liquid-water oceans on a planet — but the TOI-270 star is nearby, making it brighter for viewing. It’s also “quiet,” meaning it has few flares and allows scientists to observe it and its orbiting planets more easily.

“We’ve found very few planets like this in the habitable zone, and many fewer around a quiet star, so this is rare,” said Kane. “We don’t have a planet quite like this in our solar system.”

In our own solar system, there are either small, rocky planets like Earth, Mercury, Venus, and Mars, or much larger planets like Saturn, Jupiter, Uranus, and Neptune that are dominated by gasses rather than land. We don’t have planets about half the size of Neptune, though these are common around other stars.

“TOI-270 will soon allow us to study this “missing link” between rocky Earth-like planets and gas-dominant mini-Neptunes, because here all of these types formed in the same system,” said lead researcher Maximilian Gunther, a Torres Postdoctoral Fellow at the Massachusetts Institute of Technology.

Follow-up observations on the system have been planned for 2021, when the James Webb Space Telescope launches. It will be able to measure the composition of the TOI-270 planets’ atmospheres for oxygen, hydrogen, and carbon monoxide.

Kane says these kinds of observations can help determine whether a planet has ever had a liquid water ocean, and whether any of the planets has conditions suitable for life as we know it.

While TOI-270 is far enough away that no one living will likely ever travel there, at 73 light-years away it is still considered close.

“The diameter of our galaxy is 100,000 light years, and our galaxy is just one of millions of galaxies,” Kane said. “So, 73 light years means it’s one of our neighboring stars.”

TESS is a NASA Astrophysics Explorer mission led and operated by MIT and managed by NASA’s Goddard Space Flight Center. Additional partners include Northrop Grumman, NASA’s Ames Research Center, the Harvard-Smithsonian Center for Astrophysics, MIT’s Lincoln Laboratory, and the Space Telescope Science Institute. More than a dozen universities, research institutes, and observatories worldwide are participants in the mission.

Kane, a member of UCR’s NASA-funded Alternative Earths Astrobiology Center, is available for media interviews about TESS and his involvement in analyzing its data and observations.

He and the team hope further research will reveal additional planets in the system beyond the three now known. The smaller planet is unlikely to host life because its surface could be too warm for the presence of liquid water. But additional planets at greater distances from the star might be cooler, allowing water to pool on their surfaces.

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Scientists develop new method to detect oxygen on exoplanets

Anonymous — Sat, 01 Aug 2020 02:48:19 +0000

Scientists develop new method to detect oxygen on exoplanets Anonymous (not verified) Fri, 07/31/2020 - 19:48 More News Jules Bernstein | UCR News January 06, 2020

Scientists have developed a new method for detecting oxygen in exoplanet atmospheres that may accelerate the search for life.

One possible indication of life, or biosignature, is the presence of oxygen in an exoplanet’s atmosphere. Oxygen is generated by life on Earth when organisms such as plants, algae, and cyanobacteria use photosynthesis to convert sunlight into chemical energy.

UC Riverside helped develop the new technique, which will use NASA’s James Webb Space Telescope to detect a strong signal that oxygen molecules produce when they collide. This signal could help scientists distinguish between living and nonliving planets.

Since exoplanets, which orbit stars other than our sun, are so far away, scientists cannot look for signs of life by visiting these distant worlds. Instead, they must use a cutting-edge telescope like Webb to see what’s inside the atmospheres of exoplanets.

Conceptual image of water-bearing (left) and dry (right) exoplanets with oxygen-rich atmospheres. The red sphere is the M-dwarf star around which the exoplanets orbit. The dry exoplanet is closer to the star, so the star appears larger. (NASA/GSFC/Friedlander-Griswold)

“Before our work, oxygen at similar levels as on Earth was thought to be undetectable with Webb,” said Thomas Fauchez of NASA’s Goddard Space Flight Center and lead author of the study. “This oxygen signal is known since the early 1980s from Earth’s atmospheric studies but has never been studied for exoplanet research.”

UC Riverside astrobiologist Edward Schwieterman originally proposed a similar way of detecting high concentrations of oxygen from nonliving processes and was a member of the team that developed this technique. Their work was published today in the journal Nature Astronomy.

“Oxygen is one of the most exciting molecules to detect because of its link with life, but we don’t know if life is the only cause of oxygen in an atmosphere,” Schwieterman said. “This technique will allow us to find oxygen in planets both living and dead.”

When oxygen molecules collide with each other, they block parts of the infrared light spectrum from being seen by a telescope. By examining patterns in that light, they can determine the composition of the planet’s atmosphere. Schwieterman helped the NASA team calculate how much light would be blocked by these oxygen collisions.

Intriguingly, some researchers propose oxygen can also make an exoplanet appear to host life when it does not, because it can accumulate in a planet’s atmosphere without any life activity at all.

If an exoplanet is too close to its host star or receives too much star light, the atmosphere becomes very warm and saturated with water vapor from evaporating oceans. This water could then be broken down by strong ultraviolet radiation into atomic hydrogen and oxygen. Hydrogen, which is a light atom, escapes to space very easily, leaving the oxygen behind.

Over time, this process may cause entire oceans to be lost while building up a thick oxygen atmosphere — more even, than could be made by life. So, abundant oxygen in an exoplanet’s atmosphere may not necessarily mean abundant life but may instead indicate a history of water loss. Schwieterman cautions that astronomers are not yet sure how widespread this process may be on exoplanets.

“It is important to know whether and how much dead planets generate atmospheric oxygen, so that we can better recognize when a planet is alive or not,” he said.

Schwieterman is a visiting postdoctoral fellow at UCR who will soon start as assistant professor of astrobiology in the Department of Earth and Planetary Sciences.

The research received funding from Goddard’s Sellers Exoplanet Environments Collaboration, which is funded in part by the NASA Planetary Science Division’s Internal Scientist Funding Model. This project has also received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant, the NASA Astrobiology Institute Alternative Earths team, and the NExSS Virtual Planetary Laboratory.

Webb will be the world’s premier space science observatory when it launches in 2021. It will allow scientists to solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.

Bill Steigerwald and Nancy Jones of NASA Goddard Space Flight Center made significant contributions to this article.

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Edward Schwieterman

Newly discovered planet zips around baby star in a week

Anonymous — Sat, 01 Aug 2020 02:37:01 +0000

Newly discovered planet zips around baby star in a week Anonymous (not verified) Fri, 07/31/2020 - 19:37 More News Holly Ober | UCR News June 24, 2020

Understanding how planets form is one of the main challenges scientists face when placing our own and other planetary systems in context. Planets are thought to form from the disk-shaped clouds of gas and dust that surround newborn stars, but this process has never been observed. Astronomers normally only observe planets after they have already formed and have to deduce the pathways that led to their final states.

An artist's rendering of the AU Mic star system. (NASA’s Goddard Space Flight Center)

For more than a decade, astronomers have searched for planets orbiting AU Microscopii, a nearby star still surrounded by a disk of debris left over from its formation. Now scientists using data from NASA’s Transiting Exoplanet Survey Satellite, or TESS, and now-retired Spitzer Space Telescope report the discovery of a planet about as large as Neptune that circles the young star in just over a week.

The new planet, AU Mic b, is located 31.9 light-years away in the southern constellation Microscopium and described in a paper published in Nature. The system, known as AU Mic for short, provides a one-of-a-kind laboratory for studying how planets and their atmospheres form, evolve, and interact with their stars.

“AU Mic is a young, nearby M dwarf star. It’s surrounded by a vast debris disk in which moving clumps of dust have been tracked, and now, thanks to TESS and Spitzer, it has a planet with a direct size measurement,” said co-author Bryson Cale, a doctoral student at George Mason University in Fairfax, Virginia. “There is no other known system that checks all of these important boxes.”

“Finding a ‘missing link,’ such as the planet orbiting AU Mic, essentially caught in the act of forming, is extremely rare,” said co-author Stephen Kane, an associate professor in the Department of Earth and Planetary Sciences at the University of California, Riverside. “What makes this especially rare is that it also transits its star, so we can measure the radius as well as the mass, leading to an estimate of the bulk density of the planet and its likely composition.

An artist's rendering of the planet AU Mic b. (NASA’s Goddard Space Flight Center)

“This discovery will form the foundation for many years of observational and theoretical studies into the very earliest stages for planet formation,” added Kane, who helped develop the instrument that measured the planet mass and was part of the TESS team that discovered the transit of the planet.

AU Mic is a cool red dwarf star with an age estimated at 20 million to 30 million years, making it a stellar infant compared to our sun, which is at least 150 times older. The planet AU Mic b almost hugs its star, completing an orbit every eight-and-a-half days. It weighs less than 58 times Earth’s mass, placing it in the category of Neptune-like worlds.

“We think AU Mic b formed far from the star and migrated inward to its current orbit, something that can happen as planets interact gravitationally with a gas disk or with other planets,” said co-author Thomas Barclay, an associate research scientist at the University of Maryland, Baltimore County, and an associate project scientist for TESS at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

An artist's rendering of how scientists discovered AU Mic b. (NASA’s Goddard Space Flight Center)

When a planet crosses in front of its star from our perspective — an event called a transit — its passage causes a distinct dip in the star’s brightness. TESS monitors large swaths of the sky, called sectors, for 27 days at a time. During this long stare, the mission’s cameras regularly capture snapshots that allow scientists to track changes in stellar brightness.

Regular dips in a star’s brightness signal the possibility of a transiting planet. Usually, it takes at least two observed transits to recognize a planet’s presence.

“As luck would have it, the second of three TESS transits occurred when the spacecraft was near its closest point to Earth. At such times, TESS is not observing because it is busy downlinking all of the stored data,” said co-author Diana Dragomir, a research assistant professor at the University of New Mexico in Albuquerque. “To fill the gap, our team was granted observing time on Spitzer, which caught two additional transits in 2019 and enabled us to confirm the orbital period of AU Mic b.”

Because the amount of light blocked by a transit depends on the planet’s size and orbital distance, the TESS and Spitzer transits provide a direct measure of AU Mic b’s size. Analysis of these measurements shows the planet is about 8% larger than Neptune.

AU Mic b might not be the only planet orbiting its star.

“There is an additional candidate transit event seen in the TESS data, and TESS will hopefully revisit AU Mic later this year in its extended mission,” said lead author Peter Plavchan, an assistant professor of physics and astronomy at George Mason. “We are continuing to monitor the star with precise radial velocity measurements, so stay tuned.”

The paper, “A planet within the debris disk around the pre-main-sequence star AU Microscopii,” was published June 24.

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Surprising number of exoplanets could host life

Anonymous — Sat, 01 Aug 2020 01:57:55 +0000

Surprising number of exoplanets could host life Anonymous (not verified) Fri, 07/31/2020 - 18:57 More News Jules Bernstein | UCR News July 31, 2020

Our solar system has one habitable planet — Earth. A new study shows other stars could have as many as seven Earth-like planets in the absence of a gas giant like Jupiter.

Image from NASA's Juno spacecraft of Jupiter, the largest planet in our solar system. (NASA/JPL-Caltech/SwRI/MSSS)

This is the conclusion of a study led by UC Riverside astrobiologist Stephen Kane published this week in the Astronomical Journal.

The search for life in outer space is typically focused on what scientists call the “habitable zone,” which is the area around a star in which an orbiting planet could have liquid water oceans — a condition for life as we know it.

Kane had been studying a nearby solar system called Trappist-1, which has three Earth-like planets in its habitable zone.

“This made me wonder about the maximum number of habitable planets it’s possible for a star to have, and why our star only has one,” Kane said. “It didn’t seem fair!”

His team created a model system in which they simulated planets of various sizes orbiting their stars. An algorithm accounted for gravitational forces and helped test how the planets interacted with each other over millions of years.

They found it is possible for some stars to support as many as seven, and that a star like our sun could potentially support six planets with liquid water.

“More than seven, and the planets become too close to each other and destabilize each other’s orbits,” Kane said.

Why then does our solar system only have one habitable planet if it is capable of supporting six? It helps if the planets’ movement is circular rather than oval or irregular, minimizing any close contact and maintain stable orbits.

The Trappist-1 planetary system has three planets in its habitable zone, compared to our solar system which has only one. (NASA/JPL/Caltech)

Kane also suspects Jupiter, which has a mass two-and-a-half times that of all the other planets in the solar system combined, limited our system’s habitability.

“It has a big effect on the habitability of our solar system because it’s massive and disturbs other orbits,” Kane said.

Only a handful of stars are known to have multiple planets in their habitable zones. Moving forward, Kane plans to search for additional stars surrounded entirely by smaller planets. These stars will be prime targets for direct imaging with NASA telescopes like the one at Jet Propulsion Laboratory’s Habitable Exoplanet Observatory.

Kane’s study identified one such star, Beta CVn, which is relatively close by at 27 light years away. Because it doesn’t have a Jupiter-like planet, it will be included as one of the stars checked for multiple habitable zone planets.

Future studies will also involve the creation of new models that examine the atmospheric chemistry of habitable zone planets in other star systems.

Projects like these offer more than new avenues in the search for life in outer space. They also offer scientists insight into forces that might change life on our own planet one day.

“Although we know Earth has been habitable for most of its history, many questions remain regarding how these favorable conditions evolved with time, and the specific drivers behind those changes,” Kane said. “By measuring the properties of exoplanets whose evolutionary pathways may be similar to our own, we gain a preview into the past and future of this planet — and what we must do to main its habitability.”

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