by -
NASA’s Webb telescope spotted the smallest brown dwarf ever observed.
-
Brown dwarfs are some of the most unusual objects in the universe. They are not a star or a planet.
-
In theory, such a brown dwarf should not exist. Theorists have their hands full explaining this one.
NASA’s James Webb Space Telescope helped set another record.
Interpolating Webb’s views of a star cluster about 1,000 light-years from Earth, astronomers discovered some unusual objects – the smallest they had ever seen.
“The smallest of the new objects we found is probably the smallest free-floating brown dwarf observed to date,” Kevin Luhman, professor of astronomy 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 is a brown dwarf?
Brown dwarfs are one of the most unusual objects in the universe. Many objects we see in the cosmos are some form of nebula, planet, star or black hole.
But brown dwarfs do not fit into any of these categories. The best way to describe them is star-good.
They are not big enough to qualify as stars, like our sun. And they are so big that astronomers won’t classify them as planets. Another name scientists use for them is “failed stars.”
This leaves brown dwarfs in an unusual interstellar position that makes them very interesting to scientists studying one of the most fundamental questions in astronomy:
“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
Webb is the largest, most powerful and most complex space telescope ever built. And its sensitivity to distant light in the cosmos was key to finding this overachieving brown dwarf.
JWST also found that astronomers focused on the star cluster IC 348. Part of the reason they chose this cluster is that it is relatively young, around 5 million years old. (Our sun is about 4.5 billion years old.)
It is easier to search for fresh young dwarfs because these objects do not release 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 hydrogen’s cousin, 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 the astronomers helped astronomers set the record by targeting a young star cluster with young brown dwarfs.
“Since brown dwarfs do not have hydrogen fusion, they are relatively cool and are brightest at infrared wavelengths. As a result, an infrared telescope like JWST is the best choice for detecting new brown dwarfs,” said Luhman with BI.
The smallest brown dwarf on record
The failed star has a mass only about three to four times that of Jupiter, the astronomers reported in their paper. In comparison, the mass of our sun is more than 1,000 times that of Jupiter.
Astronomers found only one small brown dwarf located in the star cluster IC 348. They found three. The other two were smaller but still only had a mass of up to eight times that of Jupiter.
But what is the point of using the the most powerful telescope in the world to look for failed stars?
It is considered that “missing link” between stars and planets, helping scientists to solve many mysteries of the universe.
For example, “brown dwarfs overlap with giant planets in some physical properties, such as mass and temperature, so brown dwarfs can be used as laboratories to study atmospheres similar to giant planets,” Luhman said.
They are also important for understanding star formation, in general. “We have to ask, how does the star formation process work at such very small masses?” Catarina Alves de Oliveira of the European Space Agency, principal investigator of the observation program, said in the statement.
The discovery raises new questions
This discovery surprises scientists because it is difficult to theoretically prove the existence of such small brown dwarfs, according to the statement.
In the case of a small cloud, it is more difficult to collapse due to low gravity. So in theory, if it gained a mass equivalent to a giant planet, it should become a planet.
Then what causes it to be a brown dwarf? That’s a cosmic mystery that has yet to be solved.
For now, astronomers want to conduct longer surveys with JWST that could help detect even smaller objects, up to the same mass as Jupiter, according to the statement.
Will astronomers find an even smaller brown dwarf? Perhaps, if astronomers continue to discover more of these strange outliers, it could provide more clues to this cosmic mystery.
“It’s possible that brown dwarfs exist at even smaller masses, but they haven’t been discovered yet,” Luhman said.
Read the original article on Business Insider
