Astronomers using the NASA/ESA/CSA James Webb Space Telescope investigated the lowest mass limits of brown dwarfs within Flame Nebula, a hotbed of star formation in Orion’s constellation.
A collage of this image from the Flame Nebula shows a view of near-infrared light from Hubble on the left, while the two insets on the right show the near-infrared view taken by Webb. Image credits: NASA/ESA/CSA/M. Meyer, University of Michigan/A. Pagan, Stsci.
Flame Nebula It is about 1,400 light years away from Orion’s constellation.
Also known as NGC 2024 and SH2-277, this ejection nebula is about 12 light years wide and is less than a million years.
The Flame Nebula was discovered on January 1, 1786 by British astronomer William Herschel, born in Germany.
It is part of the Orion molecular cloud complex and includes famous nebulae such as the Hosehead Nebula and the Orion Nebula.
In a new study, astronomers used Webb to explore the lowest mass limits of brown dwarfs within the flame nebula.
The results, they found, were free-floating objects with mass about 2-3 times the mass of Jupiter.
“The goal of this project was to explore the fundamental low-mass limits of the star- and brown dwarf formation process,” said Dr. Matthew De Julio, an astronomer at the University of Texas at Austin.
“Webb allows you to investigate the faintest and lowest mass objects.”
The low mass limits that the required teams are looking for are set by a process known as fragmentation.
In this process, the large molecular clouds that produce both star and brown dwarfs are broken down into smaller units or fragments.
Fragmentation relies heavily on several factors where temperature, thermo-pressure, and gravity balance are the most important.
More specifically, as fragments contract under gravity, their cores become hot.
If the core is large enough, the hydrogen starts to fuse.
The outward pressure created by that fusion counters gravity, stops collapse and stabilizes the object.
However, the core is not compact, it is hot enough to burn hydrogen, and continues to shrink as long as it emits internal heat.
This near-infrared image of a portion of the Webb flame nebula highlights three low-mass objects found in the right inset. Image credits: NASA/ESA/CSA/STSCI/M. MEYER, University of Michigan.
“We’ve seen a lot of effort into making it,” said Dr. Michael Meyer, an astronomer at the University of Michigan.
“If the clouds cool efficiently, they collapse and fall apart.”
When the fragment becomes opaque enough to reabsorb its own radiation, fragmentation stops, thereby stopping cooling and preventing further decay.
The theory places the lower bounds of these fragments between 1-10 Jupiter masses.
This study significantly reduces its scope as the Webb census counted fragments of different masses within the nebulae.
“As we found in many previous studies, going to a lower mass actually increases the amount of objects about ten times as much as Jupiter’s mass,” Dr. Deirio said.
“Studies using Webb are sensitive to Jupiter up to 0.5 times the mass of Jupiter, and as they get below 10 times the mass of Jupiter, there are considerably fewer.”
“We discovered that there are fewer 5 Jupiter Mass objects than the Ten Jupiter Mass object, and we can see that there are fewer 3 Jupiter Mass objects than the 5 Jupiter Mass objects.”
“We don’t actually find any objects below the mass of two or three Jupiter. We’re hoping to see if they’re there, so we’re assuming this could be the limit itself.”
“For the first time, Webb was able to investigate beyond that limit,” added Dr. Meyer.
“If that limitation is real, there really is no object of 1 Jupiter mass that floats freely in our Milky Way galaxies, unless it forms as a planet and is kicked out of the planetary system.”
a paper Regarding the survey results, Astrophysics Journal Letter.
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Matthew de Julio et al. 2025. Identification of sales in the initial mass function of young star clusters up to 0.5 mJ. apjl 981, L34; doi: 10.3847/2041-8213/ADB96A
Source: www.sci.news
