Exoplanets in madness | Press

We are now approaching the threshold of 5,000 confirmed planets in other solar systems. These exoplanets are often worthy of science fiction. Here are some of the more exotic astronomers have observed in the past year.

Mathieu Perreault
Press

The giantess of the giants

Until this year, no planet had been detected around a star more than three times as massive as our Sun. It is now done for B Centauri b, an exoplanet ten times more massive than Jupiter. B Centauri b orbits two stars, the combined weight of which approaches ten times that of our Sun. And that’s not all: this giant (less than 0.5% of exoplanets are more massive) located 325 light years away is 100 times farther from its stars than Jupiter is from our Sun. Usually, planets of this size have orbits even closer than that of Jupiter. This discovery by astronomers from the University of Chicago, published in early December in Nature, upsets the models of planetary creation.

A 16 hour year

It is five times more massive than Jupiter, but it revolves around its star at a distance 24 times less than that between Mercury and its star. TOI-2109b has a year of 16 hours, and the duration of its orbit appears to be decreasing, which means that it could disintegrate within 1 million years in its star located in the constellation of Hercules, at 855 light years. MIT researchers, who describe it at the end of November in theAstronomical Journal, note that the temperature on the exoplanet TOI-2109b exceeds 3000 ° C. So far, astronomers have discovered 400 “hot Jupiters” in close orbit, but none are as close to their star as TOI-2109b.

An iron planet

A handful of Earth-sized exoplanets are in orbit so close together that they circle their star in less than ten hours. Astronomers from the Technical Institute in Berlin have just characterized for the first time one of these “ultrashort-period exoplanets” (USP). In Science in early December, they calculate that the density of GJ 367b, located 30 light years away, is equivalent to that of iron, which means that it has lost not only its atmosphere, but also its crust. It is therefore composed only of its ferrous core.

Artificial intelligence to the rescue

This is relatively good news for astronomers. A NASA artificial intelligence algorithm, ExoMiner, has successfully detected 300 exoplanets in data from the Kepler Space Telescope. This telescope examined half a million stars between 2009 and 2018 and discovered the majority of confirmed exoplanets. These exoplanets, which had not been recognized as such by astronomers, add only 10% to Kepler’s performance. The authors of the study published in early November in theAstrophysical Journal warn, however, that the algorithm could be refined. And, one day, compete with astronomers for the detection of exoplanets.

A planet from another galaxy

For the first time in the fall, an exoplanet outside the Milky Way was detected. M51-ULS-1b, which is 28 million light years away in the Messier 51 galaxy, flew past its star as Harvard astronomers spied on it. However, they could not determine its mass and believe that its orbit will bring it back in front of its star only in 70 years. In Nature Astronomy at the end of October, they describe how they scanned 55 stars from M51, 64 from the Messier 101 galaxy and 119 from the Messier 104 galaxy to arrive at this detection.

When a planet loses its atmosphere

When a massive collision causes a planet to lose its atmosphere, a cloud of carbon monoxide revolves for several hundred thousand years around its star, before being disintegrated by photons from the sun’s rays. MIT astronomers have just discovered, 95 light years away in the constellation Peacock, evidence of a recent collision involving a still undetected exoplanet orbiting the star HD 172555. In Nature at the end of October, they calculate that the collision took place less than 200,000 years ago.