Unique 'Failed Star' Is Like Nothing Else in the Milky Way, Study Finds

Astronomers have uncovered fascinating new details about a bizarre "failed star" that has a set of "unusual" properties and "unique" traits that distinguish it from every other known object like it in our galaxy.

In the study, which was published in The Astrophysical Journal Letters, astronomers analyzed data regarding a peculiar object known as WISEA J153429.75-104303.3, which has been dubbed "The Accident" due to the fortuitous manner of its recent discovery.

The Accident is a type of brown dwarf—a class of astronomical objects with a mass between that of a planet and a star. In fact, these objects are often referred to as "failed stars" because while they form in much the same way, they do not have the required mass to kickstart the crucial process of nuclear fusion that gives birth to true stars.

The findings of the latest paper suggest that there may be many more brown dwarfs in the universe than previously thought, given that The Accident does not appear to resemble any of the roughly 2,000 brown dwarfs that have been found in the Milky Way to date.

Some brown dwarfs appear to defy characterization but until the latest discovery, astronomers had a relatively good understanding of their general characteristics.

The Accident, however, appears to be an outlier that "defied all our expectations," Davy Kirkpatrick, an author of the study from Caltech, said in a statement.

As brown dwarfs age, they become cooler and their brightness in different wavelengths of light changes. Brown dwarfs tend to be cooler and dimmer compared to most stars, emitting mainly infrared light.

But when the authors analyzed data on The Accident, the findings caused confusion, because it appeared to have seemingly contradictory properties.

In some wavelengths of light, the object appeared to be very faint, suggesting it was very cold—and therefore old. But in others, it seemed to glow more brightly indicating a much higher temperature.

To understand more about these unusual properties, the scientists conducted further investigations revealing that The Accident, which is located around 50 light-years from Earth, was indeed very cold and that the object was moving at around half a million miles per hour—much faster than all the other known brown dwarfs at this distance from Earth.

Taking all of this evidence into account, the authors concluded that the brown dwarf's strange properties could be explained by the fact that it was somewhere between 10 and 13 billion years old, at least double the median age of other known brown dwarfs.

This means that the object likely formed early in the history of the galaxy when the Milky Way contained very little carbon, and was composed almost entirely of hydrogen and helium.

Most brown dwarfs that have a similar temperature to The Accident are rich in methane, a gas which consists of hydrogen and carbon. But the light properties of The Accident indicate that it contains very little methane today, suggesting that it is very old.

The latest findings indicate that there are many more ancient brown dwarfs in the galaxy than previously thought because astronomers have not been looking for objects with the unusual mix of characteristics displayed by The Accident.

The characteristics of The Accident are so different to any other known brown dwarf that it took a stroke of pure luck to discover the object, hence the name. It was not picked up by typical searches for brown dwarfs. In fact, the object was discovered accidentally by citizen scientist Dan Caselden who was observing another, more ordinary, brown dwarf in data from the NEOWISE project, which maps the entire sky roughly once every six months.

"This discovery is telling us that there's more variety in brown dwarf compositions than we've seen so far," Kirkpatrick said. "There are likely more weird ones out there, and we need to think about how to look for them."

The latest discovery suggests that if astronomers change how they look for brown dwarfs, we may discover many more than we could have previously predicted in future.

"It's not a surprise to find a brown dwarf this old, but it is a surprise to find one in our backyard," Federico Marocco, an astrophysicist at Caltech who was also involved in the study, said in the statement.

"We expected that brown dwarfs this old exist, but we also expected them to be incredibly rare. 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."

A brown dwarf in space
This artist’s illustration shows a dim, cold brown dwarf in space. Astronomers have uncovered fascinating new details about a bizarre "failed star." IPAC/Caltech