All About Space

Strange ancient ‘failed stars’ found by citizen scientists

- Words by Doris Elin Urrutia

Citizen scientists recently helped direct astronomer­s to a pair of objects that straddle the line between planets and stars. These newly spotted substellar objects are brown dwarfs, which share many elements in common with stars. However, unlike stars these gaseous bodies don’t have enough mass to start nuclear fusion in their core, so they resemble planets more than stars.

These newfound brown dwarfs have very unusual compositio­ns. They are the most planetlike brown dwarfs to be observed in the Milky

Way’s oldest population­s of stars. They also might help researcher­s learn more about planets outside the Solar System.

The citizen scientists who spotted both objects were part of the ongoing NASA-funded Backyard Worlds: Planet 9 project. They were looking through spacecraft data from NASA’s WISE and NEOWISE missions; both missions are chapters in the life of a single spacecraft called the Wide-field

Infrared Survey Explorer, and the objects that the collaborat­ion recently found, now called WISE 1810 and WISE 0414, are weird.

When scientists studied them, they were surprised to see that these two brown dwarfs have very little iron compared to what’s usually observed in brown dwarfs. This is a telltale sign that they are ancient, with each estimated to be about 10 billion years old. Both dwarfs have a mass of about 75 times the mass of Jupiter.

If these brown dwarfs formed with low levels of metal, so might ancient exoplanets. This could be a reason to search for old metal-poor exoplanets or alien worlds that orbit ancient metalpoor stars. Further research into this brown dwarf population could answer questions about how dependent the planet formation process is on the presence of metals.

NASA representa­tives said Backyard Worlds: Planet 9 has contribute­d to more than 1,600 brown dwarf discoverie­s.

 ??  ?? L-Caltech

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