Astronomers have conducted a detailed analysis of a mysterious galactic object known as "The Accident," revealing it to be an exceptionally old brown dwarf formed when the universe was low in methane.
Not quite a star and not quite a planet, "The Accident" belongs to the class of objects known as brown dwarfs. These "failed stars" can be up to 80 times the mass of Jupiter but lack the mass to sustain nuclear fusion in their cores, so they don't shine like true stars. Instead, they gradually cool and fade over millions or billions of years.
Astronomers have identified about 2000 of these dim objects in our galaxy, most detected by NASA's NEOWISE mission.
First discovered by an amateur astronomer, "The Accident" quickly distinguished itself. It appeared faint in some infrared wavelengths, hinting at a cold, ancient brown dwarf, yet bright in others, suggesting a young, warm one. This paradox spurred further investigation.
Researchers used the Hubble and Spitzer space telescopes, along with the WM Keck Observatory's infrared instrument in Hawaii, to resolve the mystery.
Situated about 50 light-years from Earth, this brown dwarf hurtles through the galaxy at more than 800,000 km/h—far faster than typical for its kind. According to the study published in The Astrophysical Journal Letters, this high speed indicates gravitational accelerations from larger objects over billions of years, confirming its great age.
Atmospheric analysis supports this: infrared spectra reveal very low methane levels, unusual for brown dwarfs of similar temperatures. Since methane requires carbon—which was scarce early on—this suggests formation 10 to 13 billion years ago, when the galaxy was rich in hydrogen and helium but carbon-poor.
These findings position "The Accident" as an exceptionally ancient brown dwarf, more than twice the age of any previously known.
"It's no surprise to find a brown dwarf this old, but it's a surprise to find one in our backyard," says Federico Marocco, astrophysicist at Caltech. "Finding one so close to the Solar System could be a happy coincidence, or it tells us they are more common than we thought."
