"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", University of Chicago graduate student Adina Feinstein, the lead author of a paper on the discovery, said in a NASA news release. This causes a regular dip in the measured brightness of the star that signals a planet's presence. The discovery is unique for a number of reasons - not least of which is that it was made by amateur astronomers - but the biggest surprise for scientists was its size.
Project member Diana Dragomir says that this is the coolest small planet known around a star this bright.
HD 21749b also has the longest orbital period of any exoplanet found within 100 light years of us (36 days), is about three times Earth's size but 23 times its mass - and, perhaps surprisingly, it's considered nearly chilly, as exoplanets go.
One of its latest discoveries is a freakish world that has at least 23 times the mass of Earth. This is likely the result of intense starlight breaking up atmospheric molecules and eroding away the atmospheres of some planets over time, leaving behind two populations. However, observations of a third transit were needed to confirm the discovery of an exoplanet. In comparison, exoplanet Pi Mensae b completes one circle around its star in 6.3 days, while another exoplanet, labelled LHS 3844b, has an orbital period of just 11 hours. TESS began its two-year mission in April 2018, and scientists say it will examine 200,000 nearby stars as it looks for rocky, Earth-size planets. The star is very similar to our sun, both in mass and in size. As far as what the planet may be like, the jury is still out.
Dubbed +K2-288Bb, the new planet is located within its star's habitable zone, which hints at a possibility of liquid water.
Tess has also detected dozens of short-lived events, including images of six supernovae in distant galaxies that were later seen by ground-based telescopes.
Stay tuned for more news from TESS!
The data that yielded the finds was collected between 25 July and 22 August a year ago by the space telescope's four cameras. The satellite will cover virtually the entire sky by the end of its two-year prime mission.
TESS will continue to sweep the southern hemisphere until mid-2019, at which point it will turn its cameras to the Northern Hemisphere and start another observation phase. Bright stars allow for easier followup study through ground- and space-based telescopes. To put it in context, Michael Fausnaugh, a pipeline scientist on TESS, discussed this in comparison to NASA's now defunct Kepler telescope.
If the planet is not hit by radiation, it could mean that it might support life.
K2-288Bb lies within the star's habitable zone, suggesting it may have liquid water on the surface.