Astronomers discover a new exoplanet 66.5 light-years away, making it one of the nearest known to date

Named GJ 1252 b, it is a little bigger than Earth and joins a small but growing group of small planets orbiting nearby M dwarf stars. It also joins the group of small planets orbiting at very short periods, commonly called ultra-short periods.


                            Astronomers discover a new exoplanet 66.5 light-years away, making it one of the nearest known to date
GJ 1252 b orbits a red dwarf star (Getty Images)

Every new planet found orbiting a distant star opens a world of possibilities for astronomers. And a team of scientists has now discovered a rocky exoplanet -- a little bigger than Earth -- which is among the smallest, nearest exoplanets known to date. 

The exoplanet -- implying a planet outside our Solar System -- has been dubbed as GJ 1252 b. It is only 66.5 light-years away, orbiting a red dwarf star GJ 1252, according to researchers from the Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology; and Center for Astrophysics, Harvard & Smithsonian, among others.

“Here we present the discovery of GJ 1252 b, a small planet orbiting an M dwarf. The planet was initially discovered as a transiting planet candidate using TESS (Transiting Exoplanet Survey Satellite) data. Based on the TESS data and additional follow-up data, we are able to reject all false positive scenarios, showing it is a real planet. In addition, we were able to obtain a marginal mass measurement,” say the researchers in a pre-print version on arXiv, which is operated by Cornell University. The research has also been submitted to the American Astronomical Society.

The Solar System has either small, rocky planets like Earth, Mercury, Venus, and Mars, or much larger planets like Saturn, Jupiter, Uranus, and Neptune that are dominated by gases rather than land, say scientists. The discovery of exoplanets such as GJ 1252 b will enable scientists to better understand the worlds orbiting other stars, as well as study the missing link between rocky Earth-like planets and gas-dominant mini-Neptunes. 

The diameter of our galaxy is 100,000 light-years, and our galaxy is just one of the millions of galaxies. So, 66.5 light-years imply that it is one of our neighboring stars, say experts. GJ 1252 was observed by “camera 2 of the TESS spacecraft during Sector 13,” from June 19, 2019, to July 17, 2019. 

NASA describes TESS as the next step in the search for planets outside of our solar system, including those that could support life. TESS -- launched on April 18, 2018, aboard a SpaceX Falcon 9 rocket -- will survey 200,000 of the brightest stars near the sun to search for transiting exoplanets. 

NASA's Transiting Exoplanet Survey Satellite (TESS), shown here in a conceptual illustration, will identify exoplanets orbiting the brightest stars just outside our solar system. (NASA's Goddard Space Flight Center)

According to the scientists, GJ 1252 b joins a small but growing group of small planets orbiting nearby M dwarf stars. It also joins the group of small planets orbiting at very short periods, commonly called ultra-short periods, or USPs. Experts say that USPs orbital period ranges from about one day down to less than 10 hours, and even as short as about 4 hours, especially around M dwarfs. Planets in this group are believed to have undergone photo-evaporation which removed their atmosphere.

“GJ 1252 b joins the short but growing list of small planets orbiting bright and nearby stars discovered by TESS that are amenable to detailed characterization. GJ 1252 is one of the closest planet host stars to the Sun to host a planet with a measured radius. GJ 1252’s brightness and the short orbital period (0.518 day, or 12.4 hours) make it a potential target for transmission and emission spectroscopy, which can reveal whether or not the planet has an atmosphere,” says the team.

The field of exoplanets has come a long way since the first discoveries at the end of the 20th century. One of the current frontiers in the study of exoplanets is that of small planets, smaller than Neptune and Uranus.  However, the number of small planets with a well-measured mass is still small, say experts.

The study of small planets is hampered by the lack of small planets orbiting stars that are bright enough for detailed follow-up investigations. The TESS mission is designed to overcome this problem by detecting transiting planet candidates orbiting bright stars positioned across almost the entire sky. So far, 4,104 exoplanets have been confirmed in our galaxy. 

“Among those, planet candidates orbiting nearby M dwarf stars present a special opportunity, as their typical high proper motion and small size make it easier to rule out false-positive scenarios. This quickly clears the way for follow-up studies, including mass measurement and atmospheric characterization,” says the study.

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