The hunt is on for closest Earth-like planets

NASA's Transiting Exoplanet Survey satellite passes critical review
NASA's Transiting Exoplanet Survey Satellite (TESS), shown here in a conceptual illustration, will identify exoplanets orbiting the brightest stars just outside our solar system. Credit: NASA's Goddard Space Flight Center

NASA's new Transiting Exoplanet Survey Satellite (TESS) is designed to ferret out habitable exoplanets, but with hundreds of thousands of sunlike and smaller stars in its camera views, which of those stars could host planets like our own?

TESS will observe 400,000 across the whole sky to catch a glimpse of a planet transiting across the face of its star, one of the primary methods by which exoplanets are identified.

A team of astronomers from Cornell, Lehigh and Vanderbilt universities has identified the most promising targets for this search in the new "TESS Habitable Zone Star Catalog," published in Astrophysical Journal Letters. Lead author is Lisa Kaltenegger, professor of astronomy and director of Cornell's Carl Sagan Institute and member of the TESS science team.

This new catalog draws from one originally developed at Vanderbilt that contains hundreds of millions of stars. Using data from a number of sources, including Vanderbilt's KELT telescope and the star "flicker" analysis method pioneered at Vanderbilt, Stevenson Professor of Physics and Astronomy Keivan Stassun and his team have been working since 2012 to narrow down the field from 470 million stars visible to TESS to the 250,000 most likely to host a planet like our own.

The work to sift through such a massive volume of data was done by Vanderbilt undergraduates, graduate students and postdoctoral scientists associated with the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA), as well as students, developers, and data visualizers associated with the Frist Center for Autism and Innovation.

"Our ambition is to not only detect hundreds of Earth-like worlds in other solar systems, but to find them around our closest neighboring solar systems," Stassun said. "In a few years' time, we may very well know that there are other out there, with breathable atmospheres. Of course, we won't yet know whether there is anything, or anyone, there breathing it. Still, this is a remarkable time in human history and a huge leap for our understanding of our place in the universe."

The catalog identifies 1,823 stars for which TESS is sensitive enough to spot Earth-like just a bit larger than Earth that receive radiation from their star equivalent to what Earth receives from our sun. For 408 stars, TESS can glimpse a planet just as small as Earth, with similar irradiation, in one transit alone.

"Life could exist on all sorts of worlds, but the kind we know can support life is our own, so it makes sense to first look for Earth-like planets," Kaltenegger said. "This catalog is important for TESS because anyone working with the data wants to know around which stars we can find the closest Earth-analogs."

Kaltenegger leads a program on TESS that is observing the catalog's 1,823 stars in detail, looking for planets. "I have 408 new favorite stars," says Kaltenegger. "It is amazing that I don't have to pick just one; I now get to search hundreds of stars."

Confirming an exoplanet has been observed and figuring out the distance between it and its star requires detecting two transits across the star. The 1,823 stars the researchers have identified in the catalog are ones from which TESS could detect two planetary transits during its mission. Those orbital periods place them in the middle of the habitable zone of their star.

The habitable zone is the area around a star at which water can be liquid on a rocky planet's surface, therefore considered ideal for sustaining life. As the researchers note, planets outside the habitable zone could certainly harbor life, but it would be extremely difficult to detect any signs of life on such frozen planets without flying there.

The catalog also identifies a subset of 227 stars for which TESS can not only probe for planets that receive the same irradiation as Earth, but for which TESS can also probe out further, covering the full extent of the habitable zone all the way to cooler Mars-like orbits. This will allow astronomers to probe the diversity of potentially habitable worlds around hundreds of cool stars during the TESS mission's lifetime.

The stars selected for the catalog are bright, cool dwarfs, with temperatures roughly between 2,700 and 6,000 degrees Kelvin. The stars in the catalog are selected due to their brightness; the closest are only approximately 4 light-years from Earth.

"We don't know how many planets TESS will find around the hundreds of stars in our catalog or whether they will be habitable," Kaltenegger said, "but the odds are in our favor. Some studies indicate that there are many rocky planets in the habitable zone of cool stars, like the ones in our catalog. We're excited to see what worlds we'll find."

A total of 137 stars in the catalog are within the continuous viewing zone of NASA's James Webb Space Telescope, now under construction. Webb will be able to observe them to characterize in-depth any planets found by TESS and search for signs of life in their atmospheres.

Planets TESS identifies may also make excellent targets for observations by ground-based extremely large telescopes currently being built, the researchers note, as the brightness of their host stars would make them easier to characterize.


Explore further

MuSCAT2 to find Earth-like planets in the TESS era

More information: L. Kaltenegger et al, TESS Habitable Zone Star Catalog, The Astrophysical Journal (2019). dx.doi.org/10.3847/2041-8213/ab0e8d
Journal information: Astrophysical Journal Letters

Citation: The hunt is on for closest Earth-like planets (2019, March 26) retrieved 20 June 2019 from https://phys.org/news/2019-03-closest-earth-like-planets.html
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Mar 26, 2019
"Our ambition is to not only detect hundreds of Earth-like worlds in other solar systems, but to find them around our closest neighboring solar systems," Stassun said.


TESS is a truly amazing probe, but it was designed to work in conjunction with the James Webb Space Telescope (JWST) which was supposed to follow up on TESS discoveries.

Where oh where is the JWST? Oh where oh where can it be? (Sung to the Underdog song)

It seems like it is always 2 years away, but even Congress is getting pretty fed up at this point:

https://spacenews...at-jwst/

Mar 26, 2019
This is depressing & exciting news.

Hopefully none of the confirmed Living Worlds will be within range of any possible contact.
That these systems are far enough away to avoid contamination by
Homo Anthropophagus.

That those Alien Biospheres & eventually, possible sophonts will survive long after we have destroyed ourselves & murdered our World.
& it will be murder, most foul!
But at least the deniers will will perish clutching their 24 pieces of silver.
Cause, isn't being the wealthiest corpse a sign of superiority?
While, in their spite, If they cannot live forever in luxury?
Kill all the rest of humanity & every biological creature.

Just to show us all whose Boss!

Optimism is a psychotic break from Reality.

Mar 26, 2019
It seems like it is always 2 years away, but even Congress is getting pretty fed up at this point:


Can't blame them. It's not as if politicians ever fail to deliver promises! :)

Mar 27, 2019
rrwillsj, if we continue destroying Earth the way we are now, we will not be around long enough to reach any exoplanets. At best, a relatively small number of humans will cling to existence here and on Mars. As these people struggle just to stay alive, I suspect they will develop an appreciation of the value of a living environment far more than we have. Heck, maybe they won't elect leaders that assert the Global Warming is a Chinese Hoax.

Even if we somehow reach the stars with all our bad habits intact and start destroying other worlds like we are currently destroying our own, I suspect the non-interference from aliens we are currently enjoying may not go on forever. Stated another way, sooner or later destroying every planet we can reach may ultimately be a very bad idea. Put the shoe on the other foot. Suppose we are the highly advanced species watching a nascent Borg-like species destroy everything they touch. How would we react?

Mar 27, 2019
So now we debate if the Borg have any more or less right to existence than we do?
Perhaps the Borg are protecting pre-sophonts by destroying those worlds manifesting the technology as well as the psychology of conquest & extermination?

Claiming the Right to dictate what is Right for others?
Is not the same as actually having the Right to decide for others what is Right for them.

Cause, uhh, self-serving are we?

Mar 27, 2019
Perhaps the Borg are protecting pre-sophonts by destroying those worlds manifesting the technology as well as the psychology of conquest & extermination?


You obviously did not watch the show or watch it closely enough. The Borg enslave all "sophonts" for their own selfish purposes and take their technology, planets, etc. They are a menace.

https://memory-al...episode)

rrwillsj: "Hopefully none of the confirmed Living Worlds will be within range of any possible contact."

Mark: (Essentially) Destroying worlds is a bad idea for many reasons.

rrwillsj: There is is a bright side to destroying intelligent races.

Mark: Your statements appear to be in conflict. My position is unchanged, i.e., destroying worlds is a bad idea for many reasons, even if one completely lacks any integrity whatsoever.

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