Astronomers, including those from the University of Michigan, are using NASA’s James Webb Space Telescope (JWST) to uncover answers about the universe’s smallest celestial bodies. They target the Flame Nebula, a star-formation region 1,400 light-years away, to find the smallest objects that can form independently from gas and dust. This nebula hosts brown dwarfs, sometimes called “failed stars,” which are too dim and cool for most telescopes to observe effectively. However, JWST’s infrared capabilities allow researchers to study these elusive objects in detail.
Within the Flame Nebula, JWST has identified free-floating objects two to three times the mass of Jupiter, pushing the boundaries of what was previously detectable. The study, accepted by The Astrophysical Journal Letters, explores the lower mass limits of brown dwarfs, revealing fewer objects as they approach one Jupiter mass. “The goal of this project was to explore the fundamental low-mass limit of the star and brown dwarf formation process,” stated lead author Matthew De Furio, now a postdoctoral fellow at the University of Texas.
De Furio’s research, guided by professor Michael Meyer, aims to establish the lowest mass at which objects can self-form. Meyer, involved with JWST’s planning long before its 2021 launch, highlighted the telescope’s potential in advancing astronomical research. “These results, generated by this team ably led by Matthew De Furio, are an example of its promise fulfilled,” Meyer remarked.
Smaller Fragments
Fragmentation determines the low-mass limit sought by the team. Molecular clouds break into smaller fragments, influenced by temperature, thermal pressure, and gravity. If a core is massive enough, it will start hydrogen fusion, stabilizing as a star. Without sufficient mass, fragments continue to contract without burning hydrogen. “The cooling of these clouds is important because if you have enough internal energy, it will fight that gravity,” Meyer noted.
Fragmentation halts when a fragment absorbs its radiation, preventing further collapse. Prior theories suggested a fragment’s lower limit ranged from one to 10 Jupiter masses. JWST’s findings narrow this range, indicating fewer low-mass objects, such as three-Jupiter-mass bodies, than previously detected. “We don’t really find any objects below two or three Jupiter masses,” De Furio explained.
Building on Hubble’s Legacy
Brown dwarfs, challenging to detect, hold valuable insights for star formation and planetary science. NASA’s Hubble Space Telescope has long searched for them, but JWST advances this research with its powerful instruments. “It’s really difficult to do this work, looking at brown dwarfs down to even 10 Jupiter masses, from the ground,” De Furio said, emphasizing JWST’s necessity for such investigations. Massimo Robberto of the Space Telescope Science Institute praised JWST’s capabilities, saying, “Webb is really opening an entirely new realm of possibilities, understanding these objects.”
The research team continues to study the Flame Nebula, using JWST’s spectroscopy to further analyze its cosmic constituents. “There’s a big overlap between the things that could be planets and the things that are very, very low mass brown dwarfs,” Meyer added. The team aims to distinguish between these objects in the coming years.
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