Baby Star Ejecting Exceptional Streams Of Gas Gives Us New Clues On How They Form

Artist’s impression of the baby star MMS 5/OMC-3. ALMA observations identified two gas streams from the protostar, a collimated fast jet and a wide-angle slow outflow, and found that the axes of the two gas flows are misaligned. NAOJ 

Astronomers have discovered a baby star ejecting two different gas streams. This is rather special, but what makes this star unique is that these two gas flows were released at different times, moved at different speeds, and were ejected at different angles. This exceptional system is helping researchers understand how these stellar jets actually form.

Stars are born from clouds of hydrogen pulled together by their own gravity. After they ignite, their gravitational pull continues to attract material towards them. Sometimes some of the material escapes in gaseous flows, either in a fast and narrow jet, or a wide and slow outflow.

While studying the star in question, MMS 5/OMC-3, astronomers observed it ejecting both simultaneously, although curiously the jet and the outflow are misaligned and were produced at different times. Their model suggests the fast jet started just 500 years ago while the slower one started 1,300 years ago, as reported in The Astrophysical Journal

“Measuring the Doppler shift of the radio waves, we can estimate the speed and lifetime of the gas flows,” lead author Yuko Matsushita, from Kyushu University, said in a statement. “We found that the jet and outflow were launched 500 years and 1,300 years ago, respectively. These gas streams are quite young.”

Catching them so soon after their formation is very important. If they were older flows, they might have become misaligned due to other processes but as they are young, the difference in direction is probably related to where they formed and suggests they didn’t form together.

The observations were possible thanks to the sensitive antennas of the Atacama Large Millimeter/submillimeter Array (ALMA), which allowed the researchers to work out some incredible details about the system.

ALMA image of the protostar MMS5/OMC-3. ALMA (ESO/NAOJ/NRAO), Matsushita et al.

There are two competing models to explain the forming of these outflows. One is that the narrow jets form first and their expansion creates the slow-moving outflow, but this “entrainment model” does not easily explain what is seen here as their findings indicated that the outflow was ejected before the jet. The alternative model sees the flows being created in different areas of the gas disk that surrounds the protostar. MMS 5/OMC-3 suggests that the independent model is more likely to be correct as it could explain the misalignment of the flows, which also indicates that the star’s gas disk might be warped, though more observations are necessary.  

“ALMA’s high sensitivity and high angular resolution will enable us to find more and more young, energetic outflow-and-jet-systems like MMS 5/OMC-3,” said co-author Satoko Takahashi, an astronomer at the National Astronomical Observatory of Japan and the Joint ALMA Observatory. “They will provide clues to understand the driving mechanisms of outflows and jets. Moreover studying such objects will also tell us how the mass accretion and ejection processes work at the earliest stage of star formation.”


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