The Flame Nebula, located 1,400 light-years from Earth, is a region where many stars are forming and is less than a million years old. Among these stars are “brown dwarfs,” also known as “failed stars.”
Brown dwarfs are too small to sustain hydrogen fusion like regular stars. Over time, they become cooler and dimmer, making them difficult to observe with typical telescopes.
However, they are warmer and brighter when they are young, making observation easier. NASA’s James Webb Space Telescope can see through the dense dust of the Flame Nebula to detect the faint infrared glow of these young brown dwarfs.
Astronomers used this capability to find extremely low-mass, free-floating objects in the Flame Nebula, ranging from 0.5 to 3 times the mass of Jupiter. This study aimed to understand the formation of the smallest and faintest brown dwarfs.
The team explored the low-mass limit of star and brown dwarf formation, guided by fragmentation. In this process, large molecular clouds break into smaller parts or fragments, which can form stars or brown dwarfs depending on their mass.
Gravity causes fragments to contract and heat up. If a fragment’s core becomes hot and massive enough, hydrogen fusion starts, balancing gravity and stabilizing it as a star. Fragments that can’t burn hydrogen continue to contract and cool.
Fragmentation ends when a fragment becomes opaque enough to trap its own radiation, stopping further collapse. Theories placed the smallest fragments’ masses between 1 and 10 Jupiter masses, but Webb’s observations found fewer objects as mass decreased below 10 Jupiter masses. No objects were detected below 2 or 3 Jupiter masses, suggesting this might be the minimum limit.
This study shows that Webb can explore and confirm these low-mass boundaries, ruling out free-floating objects smaller than one Jupiter mass unless they were initially planets ejected from their systems.
Brown dwarfs are challenging to find, but they are valuable for understanding star formation and planetary research because they share characteristics with both stars and planets. For decades, NASA’s Hubble Space Telescope has been key in identifying brown dwarf candidates, though it cannot detect masses as low as Webb can.
Swirls of dust detected in Flame nebula
Webb has expanded on Hubble’s decades of data from the Orion Molecular Cloud Complex, enabling detailed studies of these objects. Observing low-mass brown dwarfs, even down to ten Jupiter masses, is difficult from the ground, but Webb’s advanced capabilities make it possible.
The Webb images represent light at wavelengths of 1.15 microns and 1.4 microns (filters F115W and F140M) as blue, 1.82 microns (F182M) as green, 3.6 microns (F360M) as orange, and 4.3 microns (F430M) as red.
NASA, ESA, CSA, STScI, M. Meyer (University of Michigan)
The team continues to investigate the Flame Nebula using Webb’s tools to distinguish between very low-mass brown dwarfs and objects that could be planets. Over the next few years, this research aims to clarify their origins.
Lead study author Matthew De Furio of the University of Texas at Austin said, “Webb, for the first time, has been able to probe up to and beyond that limit. If that limit is real, there really shouldn’t be any one-Jupiter-mass objects free-floating out in our Milky Way galaxy, unless they were formed as planets and then ejected out of a planetary system.”
Astronomer Massimo Robberto of the Space Telescope Science Institute said, “It’s a quantum leap in our capabilities between understanding what was going on from Hubble. Webb is really opening an entirely new realm of possibilities, understanding these objects.”
“There’s a big overlap between the things that could be planets and the things that are very, very low mass brown dwarfs,” Meyer stated. “And that’s our job in the next five years: to figure out which is which and why.”
Source: Tech Explorist
