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TESS helps scientists find a super-cool super-Earth

Planet GJ 357 d
An artist’s conception depicts GJ 357 d orbiting its host star. (Cornell University Illustration / Jack Madden)

Astronomers are sharing a flood of findings from NASA’s Transiting Exoplanet Survey Satellite, or TESS, including the detection of a potentially habitable super-Earth far beyond our solar system.

The planet is said to circle an M-type dwarf star called GJ 357, about 31 light-years from Earth in the constellation Hydra. Known as GJ 357 d, the world is at least six times more massive than Earth — and orbits the star every 55.7 days, at a distance that’s only 20% as far away as Earth is from our own sun.

With that orbit, GJ 357 d would be broiling-hot if it were in our solar system. But its parent star is so much dimmer than our sun that the super-Earth could conceivably be just warm enough to have liquid water. That characteristic serves as the definition for habitable zones around alien suns.

“This is exciting, as this is humanity’s first nearby super-Earth that could harbor life – uncovered with help from TESS, our small, mighty mission with a huge reach,” astronomer Lisa Kaltenegger, who’s the director of Cornell University’s Carl Sagan Institute, said in a news release.

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A new search for more planets at Alpha Centauri

NEAR instrument at VLT
The NEAR instrument, shown here mounted on one of the telescopes at the European Southern Observatory’s Very Large Telescope facility, came into use with ESO’s VISIR imager and spectrometer on May 21. (ESO / NEAR Collaboration Photo)

The European Southern Observatory and the billionaire-backed Breakthrough Watch program say they have achieved first light with a new observing instrument designed to spot super-Earths in Alpha Centauri, the nearest star system to our own.

The NEAR instrument, which takes its name from the acronym for “Near Earths in the AlphaCen Region,” has been installed on an 8-meter (26.2-foot) telescope that’s part of ESO’s Very Large Telescope facility in Chile’s Atacama Desert.

NEAR takes advantage of a thermal-infrared coronagraph to block out most of the light coming from the stars in the Alpha Centauri system, a little more than 4 light-years away – including the sunlike stars Alpha Centauri A and B, plus a red dwarf called Proxima Centauri.

Cutting down on that glare makes it easier for an infrared imaging spectrometer known as VISIR to pick up the warm glow of planets orbiting the stars. The upgraded instrumentation, which took three years to develop, should be capable of detecting worlds down to twice the size of Earth.

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Could Barnard’s Star harbor an icy home for life?

Red dwarf and planets
An artist’s conception shows three planets around a red dwarf star. (NASA / JPL-Caltech Illustration)

Where’s the nearest exoplanet with conditions that are right for life? Over the past couple of years, astrobiologists have talked up Proxima Centauri b, which is sitting just 4.2 light-years away.

But Villanova University astrophysicist Edward Guinan favors a world that’s just a bit farther out, at least in astronomical terms. It’s Barnard’s Star b, a super-Earth that orbits Barnard’s Star, 6 light-years from our solar system.

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Red dwarfs seem to wipe out life’s necessities

AU Microscopii with planet
An artist’s conception shows the red dwarf star AU Microscopii with a hypothetical planet and moon in the foreground. (NASA / ESA Illustration / G. Bacon)

Red dwarf stars have been seen as the biggest potential frontier for alien life, in part because they’re the most common stars in our galaxy. But observations made using the Hubble Space Telescope suggest that the frontier might turn out to be a desert.

“We may have found the limit to habitable planets,” said Carol Grady, a co-investigator on the Hubble observations from Eureka Scientific in Oakland, Calif. She laid out the research team’s findings today at the American Astronomical Society’s winter meeting in Seattle.

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TESS mission adds ‘sub-Neptune’ to discovery list

TESS probe
An artist’s conception shows NASA’s Transiting Exoplanets Survey Satellite, or TESS, with an assortment of exoplanets. (NASA / GSFC / MIT Illustration)

Less than a year after NASA’s TESS spacecraft was launched, the scientists behind the mission have unveiled their third confirmed planet, a weird alien world that’s between Earth and Neptune in size. And hundreds of additional potential finds are in the pipeline.

The latest exoplanet on the list is HD 21749b, which orbits a star that’s about 80 percent as massive as our sun, located about 53 light-years away in the southern constellation Reticulum. Its 36-day orbital period is a record high for the TESS mission.

The “sub-Neptune” planet is about three times Earth’s size, but 23 times its mass. In comparison, Neptune is almost four times as wide as Earth but only 17 times as massive.

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Climate analysis checks for most livable exoplanets

TRAPPIST-1 planets
This illustration shows the seven Earth-size planets of TRAPPIST-1, an exoplanet system about 39 light-years away. The image shows the relative sizes of planets b through h, from left to right, but does not represent their orbits to scale. (NASA / JPL-Caltech Illustration)

If you had to pick a place to set up shop amid the seven planets in the TRAPPIST-1 star system, 39 light-years from Earth, the fourth rock from that alien sun is the best place to start.

That Earth-sized world, known as TRAPPIST-1 e, came out on top in a recent round of exoplanetary climate modeling, detailed in a paper published Nov. 1 by the Astrophysical Journal.

Not that anyone’s planning on setting up shop there soon: Unless there’s a breakthrough that allows us to travel at a significant fraction of the speed of light, it would take hundreds of thousands of years to get to TRAPPIST-1. But the climate modeling methods developed for the TRAPPIST-1 system could help scientists decide which planets to target first with telescopes capable of analyzing alien atmospheres.

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Scientists report super-Earth at Barnard’s Star

Barnard's Star b
An artist’s conception shows what the surface of the reported planet known as Barnard’s Star b might look like. (ESO Illustration / M. Kornmesser)

The astronomical team that found the nearest exoplanet at Proxima Centauri has done it again with the reported detection of a super-Earth orbiting Barnard’s Star, the second-closest star system to our own.

The discoverers acknowledge, however, that they’re not completely sure yet.

“After a very careful analysis, we are 99 percent confident that the planet is there,” Spanish astronomer Ignasi Ribas, lead author of a study about the detection published today by the journal Nature, said in a news release. “However, we’ll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet.”

Assuming it exists, Barnard’s Star b would be at least 3.2 times as massive as Earth, tracing a 233-Earth-day orbit. It would be as close to its parent star as Mercury is to our own sun — but because Barnard’s Star is a dim red dwarf, surface conditions would be far too chilly for life as we know it. The surface temperature would be about 275 degrees below zero Fahrenheit (-170 degrees Celsius).

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Planet-hunting Kepler telescope runs out of gas

Kepler space telescope
Stylized artwork shows NASA’s Kepler space telescope among planetary systems. (NASA Illustration / Wendy Stenzel / Daniel Rutter)

NASA’s Kepler planet-hunting telescope now belongs to the ages, with its fuel completely spent and its instruments shut down — but the planet quest continues, thanks to a treasure trove of downloaded data as well as a new generation of robotic planet-hunters.

Space agency officials declared the end of spacecraft operations today, nine and a half years after the car-sized probe was launched. The hydrazine fuel ran out about two weeks ago, signaled by a sharp drop in pressure readings for the propulsion system.

“In the end, we didn’t have a drop of fuel left over for anything else,” Charlie Sobeck, project system engineer at NASA’s Ames Research Center, said during a teleconference.

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Hubble boosts evidence for first exomoon

Kepler-1625b and moon transiting star
An artist’s impression shows the Jupiter-sized exoplanet Kepler-1625b transiting its parent star with the Neptune-sized candidate exomoon in tow. (Dan Durda Illustration)

With a lot of help from the Hubble Space Telescope, astronomers now feel confident enough to publish their evidence for the first moon detected in orbit around a planet beyond our solar system.

But they’re still not completely confident.

“At this point, it’s up to us to report what we’re seeing, hand it over to the community and let the community probe it,” said Columbia University astronomer Alex Teachey, one of the authors of a study about the find published in the open-access journal Science Advances. “If they see what we see, I expect some people will be convinced and other people will be skeptical. And that’s all part of the process.”

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TESS probe finds its first potential planets

TESS spacecraft
An artist’s conception shows NASA’s Transiting Exoplanet Survey Satellite, or TESS, with an alien sun and planet in the background. (NASA / GSFC Illustration)

Astronomers on the team for NASA’s Transiting Exoplanet Survey Satellite mission, or TESS, are reporting their first potential planet discoveries, just days after the spacecraft’s first science image was unveiled.

The first reported candidate planet was detected orbiting a star known as Pi Mensae, a sunlike yellow dwarf star nearly 60 light-years from Earth that was already known to harbor a world that’s more than 10 times as massive as Jupiter.

The newly detected prospect is closer to its parent star in the southern constellation Mensa, making a complete orbit every 6.3 Earth days.

In a paper published on the ArXiv pre-print website and submitted to the journal Astronomy & Astrophysics, the team’s scientists say Pi Mensae c appears to be about twice as wide as Earth and 4.5 times as massive.

Its density is estimated as roughly equal to water’s density, which suggests the planet is a super-Earth that “may have held on to a significant atmosphere,” the scientists say.

The second candidate planet orbits a red dwarf star known as LHS 3844, 49 light-years away in the constellation Indus. LHS 3844 b is thought to be a “hot Earth,” with a diameter about a third wider than Earth’s. It swings around its sun every 11 hours.

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