The Milky Way galaxy just got a lot weirder. More to the point, our understanding of how weird the galaxy is got a lot better.
It’s possible the Milky Way is positively teeming with a startling number of dead stars, some of which might be nearly as old as the galaxy itself.
We have an amateur stargazer to thank for the discovery. Dan Caselden was playing the video game Counter-Strike late one night back in 2018 when a custom software program he’d created for analyzing data from a NASA star survey found something odd.
A huge cold object in space, moving fast 50 light-years from Earth. “The system enthusiastically pointed me to a place in the sky that had absolutely nothing interesting there at all,” Caselden told The Daily Beast. “But in the bottom left corner, there was a faint object just screaming across the screen.”
Because he’d found the object without really trying, Caselden named it… The Accident.
Caselden abandoned his video-game teammates and immediately emailed some astronomers he was working with details of his discovery. The emails kicked off three years of close study by a team of scientists, the initial results of which are finally beginning to appear in print.
What Caselden found appears to be a brown dwarf, a star up to 75 times the mass of Jupiter that never quite managed to ignite and become the kind of star that warms and lights up our planet.
Brown dwarfs are cold and dark. And while these dead stars aren’t uncommon, they’re usually a bit warmer and brighter and a lot farther away from Earth than The Accident seems to be. “It really stood out,” Caselden said of his brown dwarf.
The Accident’s light profile hints that it contains very little methane, which is usually abundant in brown dwarfs. That dearth of methane could be a sign that The Accident formed when the Milky Way itself contained very little of the gas. “The Accident is very old, most likely older than 10 billion years,” Federico Marocco, a Caltech astrophysicist who studied The Accident, told The Daily Beast.
The Accident’s age is surprising. Its proximity to Earth is even more surprising. “We expected that brown dwarfs this old exist, but we also expected them to be incredibly rare,” Marocco explained in a NASA release. “The chance of finding one so close to the solar system could be a lucky coincidence, or it tells us that they’re more common than we thought.”
In other words, if a random glance at a random patch of space not far from Earth just happened to turn up an unlit star as odd as The Accident, a more comprehensive survey might turn up even greater wonders in even greater quantities.
“The Accident is showing us that the Milky Way still has mysteries to reveal,” J. Davy Kirkpatrick, another Caltech astronomer who has studied The Accident, told The Daily Beast.
Clues abound that the Milky Way is much stranger than we once thought. In just the past few years, scientists have spotted free-roaming “rogue” planets wandering across the galaxy, untethered to any star.
They’ve also detected a very strange “zombie” star that apparently survived a collision with another star and is now streaking across the Milky Way like shrapnel from an explosion, on a path that could take it into the unfathomable cold, dark expanse between our galaxy and the next.
New and better technology could help amateurs such as Caselden and pros such as Marocco and Kirkpatrick find more weird stuff in the vastness of space that could potentially tell us more about our galaxy. It’s worth noting that the survey data Caselden used to first glimpse The Accident came from an old NASA probe called the Wide-Field Infrared Survey Explorer, or WISE.
To get a closer look, the scientists used a ground-based telescope at the W. M. Keck Observatory in Hawaii as well as NASA’s Hubble and Spitzer space telescopes.
While the follow-on surveys helped them better understand The Accident, they didn’t reveal any additional nearby brown stars sharing The Accident’s peculiar color, temperature and composition. “Where are the other Accidents?” Caselden asked. “We may need new infrared telescopes to find out.”
It just so happens, NASA is getting ready to launch a new infrared telescope—the much-delayed, high-tech James Webb Space Telescope.
With James Webb at their disposal, Caselden, Marocco and Kirkpatrick might be able to find other old, cold brown dwarfs. Especially now that they know what to look for. “The Accident has shown us that we should accept a wider range of possibilities when considering what very cold objects should look like,” Kirkpatrick said. “We’ll be casting a wider net when searching for other faint denizens of the solar neighborhood.”
Caselden already knows what he wants to call the next brown dwarf he finds. “I want the new system that I’ve spent all my free time for the past few years to find another Accident and I will call it The On-Purpose.”