NASA Scientists Confirm A Planet Orbits Star AU Microscopii

Astronomers have confirmed using NASA's retired Spitzer Space Telescope and the Transiting Exoplanet Survey Satellite (TESS) that a planet is orbiting a nearby star called AU Microscopii (AU Mic). That star is surrounded by disc debris leftover from its formation. Using data from TESS and Spitzer, the team has discovered a planet orbiting the star about as large as Neptune.

One interesting aspect of the planet is that it circles the young star in about a week. Researchers consider AU Mic as a unique laboratory for studying how planets in their atmospheres form, evolve, and interact with stars. AU Mic is a young, nearby M dwarf star that is surrounded by a dusty debris disc.

Inside that debris disc are moving clumps of dust that have been tracked in the past. Data from Spitzer and TESS allowed scientists to confirm with a direct size measurement that the star has a planet orbiting. The new planet is called AU Mic b and is usually described in a paper co-authored by Bryson Cale and his advisor Peter Plavchin. AU Mic is a cool red dwarf star with an age estimated to be 20 to 30 million years.

For comparison, the Sun is 150 times older than that. The star is so young that it primarily shines from heat generated. Less than 10% of the energy the star generates comes from the fusion of hydrogen and helium and its core. That is the process the power stars like the Sun. The system is 31.9 light-years away in the southern constellation of Microscopium.

AU Mic b orbits very close to its star meeting only 8.5 days to make a complete orbit. It weighs less than 58 times Earth's mass, placing it in the category of Neptune-like worlds. The researchers believe that the planet formed far from the star and migrated inward to its current orbit. Scientists have believed for decades that AU Mic might have planets, and this is the first confirmation that planets do exist around the star.