An earth-sized planet discovered around a red dwarf star shares its name with a biscuit

Astronomers have discovered an Earth-sized planet orbiting an ultrasound red dwarf star similar in size to Jupiter. The red dwarf, located about 55 light-years away, is 100 times less luminous than the sun and exhibits half the temperature of our star.

This new exoplanet, or exoplanet, is called SPECULOOS-3, and it marks the second time astronomers have discovered a planetary system around a red dwarf star, the first being the Trappist-1 system .

A world the size of Earth was discovered by the Search for habitable Planets Eclipsing Ultra-cool Stars (SPECULOOS) project located at the Paranal Observatory in the Atacama Desert in northern Chile. The aim of the mission (named after a popular Belgian biscuit called “Speculoos”) is to use infrared observations to detect rocky exoplanets around nearby ultracool stars such as red dwarfs and “failed stars, ” or brown dwarfs as they are called.

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“SPECULOOS-3 b orbits a red dwarf star. The small size of these stars makes it easier to detect small Earth-sized planets around them, and above all to observe any planetary atmospheres,” Émeline Bolmont, team member and assistant professor in the astronomy department at the UNIGE, said in a statement. “Numerous studies show that life could develop on the orbiting red dwarf planets. They are, therefore, ideal candidates for us.”

Although SPECULOOS-3 b is almost the same size as our planet, there are other differences that indicate it is very different from Earth. This includes the entire orbit of its star, so a year on SPECULOOS-3 b lasts only 17 hours. This exoplanet is probably “tidal-locked” to its star, meaning it has an eternal day and an eternal night.

“We believe that the planet rotates synchronously, so that the same side, called the day side, always faces the star, just as the moon does for the Earth,” said SPECULOOS team leader, Michaël Gillon, in statement. “On the other hand, the night side hand would be, to be locked in endless darkness.”

SPECULOOS-3 b and custom

Red dwarfs, or “M-dwarfs,” are believed to make up 70% of the stars in the Milky Way galaxy. Because they are thousands of degrees cooler than the sun, they burn through their fuel supplies needed for nuclear fusion relatively slowly. This means that red dwarfs have extremely long lifetimes – at least a hundred times longer than the sun’s estimated 10 billion year lifetime.

The planet’s star, SPECULOOS, is part of an even cooler subclass of red dwarfs that astronomers predict will eventually be the last stars to burn in a cold and dark cosmos; the orbs will probably burn for more than 100 billion years. This means that life could have more time to develop around red dwarfs than in systems around stars that live quickly and die young.

However, red dwarfs are not well understood due to their low luminosity. In addition, planets around these cool little stars are rarely found. So, while red dwarf exoplanets may be the most common worlds in our galaxy, we don’t know much about them. SPECULOOS aims to change that.

A red star at the bottom of the screen and an exoplanet at the top.  The star appears to be radiating tiny flames from its body.

A red star at the bottom of the screen and an exoplanet at the top. The star appears to be radiating tiny flames from its body.

Due to the fact that the ultracool dwarf stars are scattered throughout the sky, scientists must look at the objects one at a time and over a period of weeks in order to detect possible transiting planets. This requires a dedicated network of professional telescopes like those comprising SPECULOOS, and the discovery of SPECULOOS-3 bi is a step in the right direction towards the goal of understanding red dwarf worlds.

However, while the planets orbiting the red dwarfs are considered ideal locations for life, SPECULOOS-3 b is not habitable, to be clear. The planet is bombarded by about 16 times more radiation than the Earth receives from the sun, which makes it impossible for liquid water to exist on its surface.

When it comes to hunting for life on planets around a red dwarf, the seven Earth-like planets of the Trappist-1 system, many of which are in their star’s habitable zone, are even better targets. But this does not make SPECULOOS-3 b uninteresting. Far from it.

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SPECULOOS-3 b will be the ideal target for the James Webb Space Telescope (JWST), for testing whether planets close to their stars can hold on to atmospheres, according to the team.

“The JWST should be able to determine whether the planet was able to maintain an atmosphere despite its proximity to its star,” Bolmont said. “If we find one on this highly irradiated planet, it gives us good hope that there is also one on the planets in TRAPPIST-1’s habitable zone.”

The team’s research was published on Wednesday (May 15) in the journal Nature Astronomy.

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