Astronomers discover two ‘super-Earths’ orbiting a nearby star

TESS Photometry for LP 890-9. For each of the four sectors, the 2-minute data points (in grey) were grouped at 30-minute intervals to produce the black points, with error bars corresponding to the root mean squared uncertainty of points in bins. Crossings of LP 890-9 b and c are indicated by red and blue dotted lines, respectively. The region highlighted in orange in sector 4 was affected by thermal effects and was therefore excluded from the analysis. Credit: Delrez et al. , 2022.

An international team of astronomers reports the discovery of two new “super-Earths” exoplanets orbiting a nearby M-type dwarf star. The newly discovered alien worlds, called LP 890-9 b and LP 890-9 c, are slightly larger than Earth. . The results have been published in Astronomy and astrophysics.

“Super planets” are planets larger than Earth but only the mass of Neptune. Although the term “super-Earth” only refers to the mass of the planet, it is also used by Astronomy scientists To describe planets larger than Earth but smaller than the so-called “mini Neptune” (with a radius between one and four Earth radii).

Now, astronomers led by Laetitia Delris of the University of Liège in Belgium have discovered two new super-Earths. They observed LP 890-9 – a nearby dwarf star of type M6V spectroscopically, using NASA’s Transiting Exoplanet Reconnaissance Satellite (TESS). This led to the discovery of the inner planet, which received the designation LP 890-9 b. Follow-up observations of this system with the Southern Observatory SPECULOOS (EClipsing ULtra-cOOl Stars) led to the discovery of a second, longer-period transiting planet – LP 890-9 c.

“We have presented the discovery and initial characterization of the LP 890-9 system, which hosts two temperate super-Earths passing through a nearby M6 dwarf,” the researchers wrote in the paper.

LP 890-9 b has a radius of about 1.32 Earth’s radius and is estimated to have a mass of no more than 13.2 Earth masses. The planet orbits its host every 2.73 days at a distance of about 0.018 astronomical units from it. The equilibrium temperature for LP 890-9 b was calculated to be 396 K.

When it comes to LP 890-9c, its radius has been measured to be about 1.37 Earth radii, while its mass is assumed to be less than 25.3 Earth masses. An exoplanet is separated from parent star by 0.04 AU and his orbital 8.46 days approx. The planet’s equilibrium temperature is estimated at 272 K.

The host star LP 890-9 has a radius of about 0.15 solar radii and a mass of 0.12 solar masses. The effective temperature of this M dwarf is about 2871 K and its luminosity is at 0.00143 solar luminosity. The star is located around 104 light years away from the earth.

Summing up the results, the astronomers confirmed that their discovery makes LP 890-9 the second-coolest star found to host planets after TRAPPIST-1. They added that LP 890-9 c is the second most habitable terrestrial planet known to date.

The discovery of the remarkable LP 890-9 system presented in this work provides another rare opportunity to study temperate terrestrial regions. planets About our smaller and more wonderful neighbours.

Two planets orbiting a nearby star discovered by TESS

more information:
L. Delrez et al, two temperate super-Earths crossing a nearby M-type dwarf, Astronomy and astrophysics (2022). DOI: 10.1051 / 0004-6361 / 202244041

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