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Newly-discovered exoplanet twice the size of Earth could have water

09 January 2019

Three new planets and six supernovae outside our solar system have been observed by Nasa's planet-hunting Tess mission in its first three months.

It was identified by TESS, NASA's leading mission to identify exoplanets, alongside two other worlds. The announcement was made by scientists this week, and the new planet is called HD 21749b. It's clear that the world is significantly larger than Earth, about twice the size, but it's located within what scientists consider the habitable zone of its system. If confirmed, it could be the first Earth-sized world discovered by TESS.

The planet has an orbit of 36 days and a surface temperature of about 300 degrees Fahrenheit.

"It's the coolest small planet that we know of around a star this bright", said Diana Dragomir, a postdoctoral researcher in the Massachusetts Institute for Technology's Kavli Institute for Astrophysics and Space Research.

"It's the coolest planet we know of around a star this bright".

"We think of TESS as an exoplanet-hunter, but in addition TESS is very effective at finding many other types of objects", said Dr. George Ricker, principal investigator with the TESS mission. As NASA's JPL notes in a blog post, planets between 1.5 and 2 times the size of Earth are seemingly rare based on the exoplanet data we've gathered thus far.

The discoveries of a new planet and several supernovae are exciting enough and what's to come should give us even more information about the phenomena already discovered.

The exoplanet, named K2-288Bb, could either be a rocky world like Earth or a gas-rich planet like Neptune. This causes a regular dip in the measured brightness of the star that signals a planet's presence.

NASA's Transiting Exoplanet Survey Satellite (TESS) recorded more than 100 short-lived changes - a lot of them likely stellar outbursts of various types - in its first observing sector.

HD 21749b completes one orbit of its host star, which is almost as bright as our sun, every 36 Earth days. Revealed in a press conference at a meeting of the American Astronomical Society (AAS), planet Kepler-10c is 17 times heavier than the Earth, and may require scientists to rethink their ideas on planet formation and the likelihood of life in our galaxy. Because TESS stares non-stop at one slice of the sky for 27 days, then moves to a neighbouring slice, it captures an unprecedented view of these exploding stars as they brighten and then dim.

"Some of the most interesting science occurs in the early days of a supernova, which has been very hard to observe before TESS", said Michael Fausnaugh, a TESS researcher at MKI. "NASA's Kepler space telescope caught five of these events as they brightened during its first four years of operations". Its size is different from other exoplanets that revolve around a star outside our solar system. For what it's worth, several TESS finds have been the subject of pre-print research papers.

TESS is considered to be a "bridge to the future", finding exoplanet candidates to study in more detail.

The data that yielded the finds was collected between 25 July and 22 August a year ago by the space telescope's four cameras. Using ground-based telescopes, astronomers are now conducting follow-up observations on more than 280 TESS exoplanet candidates.

Newly-discovered exoplanet twice the size of Earth could have water