A team of astronomers announces that they have identified the presence of an exoplanet around one of the youngest known stars. An interesting discovery that could tell us more about the youth of our own system.
AU Microscopii (AU MIC), located about 32 light years away, is a young and small star only 22 million years old. For comparison, the Sun is about twice as big and has 4.6 billion years on the clock.
We have also known since the early 2000s that AU MIC has a debris disc which ranges from 35 to 210 AU (one AU equals approximately 150 million km). Therefore, astronomers naturally wondered if one or more planets could form inside.
Finally, the satellite TESS (transition Transitioning Exoplanet Survey), from NASA, isolated one in 2018. These data were then confirmed by follow-up studies made with the Spitzer telescope, now at rest. These works are now the subject of a publication in the journal Nature.
A gas giant very close to its star
This new exoplanet – which has just been named AU MIC b – has a size similar to that of Neptune. And, like Neptune, this is a gas giant. However, the similarities end there. AU MIC b is indeed three times more massive (or about 58 land masses).
In addition, if we know that Neptune prefers to evolve in the cold and dark parts of the solar system (30.1 AU all the same), completing a tour of the Sun in 164.79 Earth years, this exoplanet evolves very close to its star, completing a revolution in 8.46 days. In other words, AU MIC b is closer to its star than is Mercury from the Sun.
Shedding light on the formation of the solar system
The youth and proximity of this system makes it a prime target for studying the way in which planetary systems are formed.
« This star has probably not yet had time to form small rocky planets, explains Thomas Barclay, of the University of Maryland (United States). This gives us a chance to analyze what could have happened before our own terrestrial planets, like Earth and Venus, entered the solar system. ».
The researchers plan in particular to focus on the atmospheric composition of this new world. Assuming that certain chemicals can indeed only form at certain distances from a star, the presence of such and such a substance could then tell us where the planet was formed, and if it has migrated since its formation. .
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