NASA's James Webb Space Telescope breaks another record, discovering the smallest star-like object astronomers have ever seen

  • NASA's Webb telescope spotted what is likely the smallest brown dwarf ever observed.

  • Brown dwarfs are some of the most unusual objects in the universe. They aren't a star or a planet.

  • In theory, such a brown dwarf shouldn't exist. Theorists have their hands full explaining this one.

NASA's James Webb Space Telescope has helped set yet another record.

Pointing Webb's sights on a star cluster about 1,000 light years from Earth, astronomers discovered some unusual objects — the smallest they've ever observed.

"The smallest of the new objects that we found is likely to be the least massive free-floating brown dwarf that has been observed to date," Kevin Luhman, an astronomy professor at Pennsylvania State University, told Business Insider.

Luhman was the lead author of a study documenting the team's findings that they recently published in the peer-reviewed journal The Astronomical Journal.

What are brown dwarfs?

NASA illustration of a brown dwarf.
Brown dwarfs emit light and temperature, but not nearly to the extent of a star.NOIRLab/NSF/AURA/P. Marenfeld/Acknowledgement: William Pendrill

Brown dwarfs are one of the most unusual objects in the universe. Many objects we can see in the cosmos are some form of nebula, planet, star, or black hole.

But brown dwarfs don't fall into any of these categories. The best way to describe them is star-like.

They're not large enough to qualify as a star, like our sun. And they're so large that astronomers won't categorize them as a planet. Another name scientists use for them is "failed stars."

This leaves brown dwarfs in an unusual in-between state that makes them especially interesting for scientists studying one of astronomy's most fundamental questions:

"One basic question you'll find in every astronomy textbook is, 'What are the smallest stars?' That's what we're trying to answer," Luhman said in a statement.

Webb sets another record

JWST has broken numerous records in astronomy since it was launched. NASA

Webb is the largest, most powerful, and most complex space telescope ever built. And its sensitivity to distant light in the cosmos was crucial for finding this record-breaking brown dwarf.

Helping JWST out was also the fact that astronomers targeted the IC 348 star cluster. Part of the reason they chose this cluster is because it's relatively young, about 5 million years old. (Our sun is about 4.5 billion years old.)

Searching for young, new brown dwarfs is easier because these objects don't fuse hydrogen in their cores, like our sun. So they don't get nearly as bright as a star.

But brown dwarfs are massive enough to generate the right conditions to fuse a cousin of hydrogen, called deuterium. This is how they generate heat and light that telescopes like JWST can detect.

Over time, however, brown dwarfs deplete their deuterium reserves, and burn dimmer, as a result, making them harder to detect. So targeting a young star cluster with young brown dwarfs helped astronomers set the record.

"Since brown dwarfs lack hydrogen fusion, they are relatively cool and glow brightest at infrared wavelengths. As a result, an infrared telescope like JWST is the best option for trying to detect new brown dwarfs," Luhman told BI.

The smallest brown dwarf on record

Webb NIRCam composite image of Jupiter.
Webb NIRCam composite image of Jupiter.NASA, ESA, Jupiter ERS Team; image processing by Judy Schmidt

The failed star has a mass of only about three to four times that of Jupiter, the astronomers reported in their paper. By comparison, our sun has a mass of more than 1,000 times that of Jupiter.

Astronomers didn't just find one small brown dwarf nestled in the IC 348 star cluster. They found three. The other two weren't as small but still only had masses of up to eight times that of Jupiter.

But what's the point of using the world's most powerful telescope to seek out failed stars?

They're considered the "missing link" between stars and planets, helping scientists unravel many mysteries of the universe.

For instance, "brown dwarfs overlap with giant planets in some physical properties, such as mass and temperature, so brown dwarfs can be used as laboratories for studying atmospheres that are similar to those of giant planets," Luhman said.

They're also important for understanding stellar formation, in general. "We have to ask, how does the star formation process operate at such very, very small masses?" Catarina Alves de Oliveira of the European Space Agency, principal investigator on the observing program, said in the statement.

The discovery raises new questions

Scientists are surprised by this discovery because it is difficult to theoretically prove the existence of such small brown dwarfs, per the statement.

For a small cloud, it's harder to collapse due to low gravity. So theoretically, if it has gained a mass equivalent to a giant planet, it should become a planet.

Then what causes it to become a brown dwarf? That's a cosmic mystery that remains to be solved.

Up next, astronomers would like to conduct longer surveys with JWST that could help detect even smaller objects, down to the same mass as Jupiter, per the statement.

Will astronomers find an even smaller brown dwarf? Perhaps, if astronomers keep discovering more of these bizarre outliers, it could give more clues to this cosmic mystery.

"It is possible that brown dwarfs exist at even smaller masses, but they have not been detected yet," Luhman said.

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