NASA's planet-hunter TESS makes first discoveries

Mindy Sparks
January 8, 2019

NASA's planet-hunting telescope is making landmark discoveries at an astonishing pace and has now confirmed discovery of a third new planet and a handful of exploding stars in our "cosmic backyard".

Since Kepler is no longer hunting for planets, NASA is now hoping that a new space telescope will aid in the search: the Transiting Exoplanet Survey Satellite (TESS).

Unusually, the planet is roughly 1.9 times the size of Earth - much larger than most other exoplanets that orbit close to their stars, which are normally not more than 1.5 times the size of Earth. "The planet likely has a density of water, or a thick atmosphere".

Of the planets yet discovered, HD 21749b has the longest orbital period around its star, taking 36 days to perform a transit. At a cool 300 degrees Fahrenheit (~149 degrees Celsius), it's also "relatively cool" for a planet orbiting so close to its star.

Serendipitously, the researchers have also detected evidence of a second planet, though not yet confirmed, in the same planetary system, with a shorter, 7.8-day orbit.

Past year at the American Astronomical Society meeting, it was announced that citizen scientists helped discover five planets between the size of Earth and Neptune around star K2-138, the first multiplanet system found through crowdsourcing.

Its size is unusual for an exoplanet (the term for a planet that orbits a star outside our solar system).

"Reorienting Kepler relative to the Sun caused miniscule changes in the shape of the telescope and the temperature of the electronics, which inevitably affected Kepler's sensitive measurements in the first days of each campaign", said study co-author Geert Barentsen, an astrophysicist at NASA's Ames Research Center, in a statement.

The planet is in the K2-288 system, which contains a pair of dim, cool M-type stars that are 5.1 billion miles apart, about six times the distance between Saturn and the sun. Because TESS is programmed to look at a portion of the sky for only 27 days, any planets with a longer orbit are hard to identify. The satellite will cover virtually the entire sky by the end of its two-year prime mission. It lies within its host star's habitable zone, which means the planet may have liquid water on its surface.

The other two planets it has discovered are Pi Mensae c, a super-Earth that zips around its star in 6.3 days, and LHS 3844b, a rocky planet that flies around its planet in a whopping 11-hour orbit.


"It's the coolest small planet that we know of around a star this bright", Dragomir said.

"We think this planet wouldn't be as gaseous as Neptune or Uranus, which are mostly hydrogen and really puffy", Dragomir said.

Within the sector 1 data, Dragomir identified a single transit, or dip, in the light from the star HD 21749.

Follow-up observations were made with multiple telescopes to confirm the exoplanet.

"They had looked at this star system a decade ago and never announced anything because they weren't sure if they were looking at a planet versus the activity of the star", Dragomir says.

In the HARPS data, she and her team found that the HD 21749 signal repeats every 36 days.

It turned out that they did not analyze all of the data.

"It's a very exciting discovery due to how it was found, its temperate orbit and because planets of this size seem to be relatively uncommon", said Adina Feinstein, a University of Chicago graduate student in astrophysics and lead author of a paper describing the new planet that was accepted for publication by The Astronomical Journal.

"There was quite some detective work involved, and the right people were there at the right time", Dragomir said. "But we were lucky and we caught the signals, and they were really clear".

The discovery was announced Monday at the 233rd meeting of the American Astronomical Society in Seattle.

Other reports by Iphone Fresh

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