HD 21749b appears to have the longest orbital period of the three planets so far identified by Tess.
Since it started surveying the sky in July, the MIT-led Transiting Exoplanet Survey Satellite project has identified Pi Mensae b, a "super-Earth" that travels around its star every six days, and LHS 3844b, a rocky world with an orbit of only 11 hours. If this world is confirmed, it will be the first roughly Earth-size planet found 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", Dr Dragomir said.
"We know a lot about atmospheres of hot planets, but because it's very hard to find small planets that orbit farther from their stars, and are therefore cooler, we haven't been able to learn much about these smaller, cooler planets", she continued.
It is three times bigger than Earth, which classes it as a Sub-Neptune exoplanet, but it is surprisingly 23 times its mass. In comparison, Neptune is nearly four times as wide as Earth but only 17 times as massive.
The extraordinarily large planet is 226 light-years away, in a constellation called Taurus, and experts say it's most likely either a rocky or gas-rich planet, similar to Neptune. "The planet likely has a density of water, or a thick atmosphere".
An illustration of NASA's Kepler space telescope. NASA
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. During the meeting, Chelsea Huang, an MIT researcher working on the TESS datasets, stated that TESS has confirmed the existence of eight new exoplanets, and that "there are probably 20 or 30" other potential discoveries "almost ready to be published".
A timely reminder of that fact comes in the form of an all-new exoplanet discovery made by citizen scientists who dedicated their time to combing through Kepler's logs.
TESS will look for exoplanets using the transit method, observing slight dips in the brightness of stars as planets pass in front of them. "But we re-extracted the data and zoomed in to look more carefully, and found what looked like the end of a transit".
Data from Kepler has helped scientists determine whether a given planet has a solid surface, like Earth, or a gaseous one, such as Jupiter.
K2-288Bb, as the new planet is called, is located within its star's habitable zone, which is why liquid water is a possibility.
The newfound planet K2-288Bb, illustrated here, is slightly smaller than Neptune. It was unclear whether this signal was caused by a planet or variations in the host star's activity, so Dragomir and her colleagues analyzed observations taken by another instrument, the High Accuracy Radial velocity Planet Searcher (HARPS), a spectrograph installed on a telescope at the European Southern Observatory's La Silla Observatory in Chile.
"This is only the ninth system discovered containing six or more planets", he said.
TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by Goddard. More than a dozen universities, research institutes, and observatories worldwide are participants in the mission.