Astronomers just discovered two new 'super-Earth' planets

Astronomers at the University of Birmingham have just discovered two 'super-Earth' planets orbiting LP 890-9 (also called TOI-4306 or SPECULOOS-2)- a small, cool star located about 100 light-years from Earth, according to a press release published by the institution on Wednesday. What's most notable about the development is that one of the planets may be habitable.

Seeking previously missed planets

The discovery was made by using the SPECULOOS telescopes (Search for habitable Planets EClipsing ULtra-cOOl Stars) and by seeking additional transiting planets in the system that would have been missed by TESS.

"TESS searches for exoplanets using the transit method, by monitoring the brightness of thousands of stars simultaneously, looking for slight dimmings that might be caused by planets passing in front of their stars," explained Laetitia Delrez, a postdoctoral researcher at the University of Liège, and the lead author of the article.

"However, a follow-up with ground-based telescopes is often necessary to confirm the planetary nature of the detected candidates and to refine the measurements of their sizes and orbital properties," adds Delrez.

The telescopes of the SPECULOOS project, installed at ESO's Paranal Observatory in Chile and on the island of Tenerife, are optimized to observe very cold stars, such as LP 890-9. These types of stars emit most of their light in the near-infrared- which TESS has a rather limited sensitivity to.

"The goal of SPECULOOS is to search for potentially habitable terrestrial planets transiting some of the smallest and coolest stars in the solar neighborhood, such as the TRAPPIST-1 planetary system, which we discovered in 201," recalls Michaël Gillon from the University of Liège, and the principal investigator of the SPECULOOS project.

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"This strategy is motivated by the fact that such planets are particularly well suited to detailed studies of their atmospheres and to the search for possible chemical traces of life with large observatories, such as the James Webb Space Telescope (JWST)," reveals Gillon.

A second unknown planet

The new observations not only confirm one super-Earth planet, but they also detected a second. This second planet, LP 890-9c (renamed SPECULOOS-2c by the SPECULOOS researchers), is similar in size to the first (about 40% larger than Earth) but has a longer orbital period of about 8.5 days which places it in the so-called 'habitable zone' around its star.

“The habitable zone is a concept under which a planet with similar geological and atmospheric conditions as Earth, would have a surface temperature allowing water to remain liquid for billions of years," explains Amaury Triaud, a professor of Exoplanetology at the University of Birmingham. Triaud is also the leader of the SPECULOOS working group that scheduled the observations leading to the discovery of the second planet.

"This gives us a license to observe more and find out whether the planet has an atmosphere, and if so, to study its content and assess its habitability," shares Triaud.

Now, researchers will focus on evaluating the atmosphere of this planet.“It is important to detect as many temperate terrestrial worlds as possible to study the diversity of exoplanet climates, and eventually to be in a position to measure how frequently biology has emerged in the Cosmos,” adds Professor Amaury Triaud.