A massive star on the distant outskirts of our Milky Way galaxy is seen blowing a powerful cosmic blowtorch in a new image courtesy of James Webb Webb Space Telescope’s Near-Infrared Camera.
The James Webb Space Telescope (JWST) caught the two jets slamming into the interstellar medium around them, forming the nebulous structure known as Sharpless 2-284, or Sh2-284 for short.
What’s more, their very existence is proof of the process by which the most massive stars in the universe form.
Models of star formation suggest the size of the jets scales with the size of the star producing them.
“Such a spectacular outflow of molecular hydrogen from a massive star is rare in other regions of our galaxy.”
The James Webb Webb Space Telescope’s Near-Infrared Camera has captured a new image of a massive star on the far side of our Milky Way galaxy blowing a potent cosmic blowtorch.
Sharpless 2-284, or Sh2-284 for short, is a nebulous structure formed by the two jets colliding with the interstellar medium surrounding them, as seen by the James Webb Space Telescope (JWST). At a speed of hundreds of thousands of miles per hour, the jets spread out over a total of eight light-years. Furthermore, the fact that they exist at all is evidence of the formation process of the universe’s most massive stars.
According to a statement from Jonathan Tan of Chalmers University of Technology in Gothenburg and the University of Virginia in Charlottesville, “Once we discovered a massive star launching these jets, we realized we could use the Webb observations to test theories of massive-star formation.”.
As lower mass stars form, it is common to observe them launching stellar jets. The substance that falls onto the expanding star, primarily hydrogen gas, fuels the jets. A disk of this material forms around the young protostar. The star gains mass from some of the material in the disk, but if too much material accumulates in the disk, some of it is thrown out in two jets along the young star’s axis by tightly wound magnetic fields.
Low-mass stars form in a fairly orderly fashion, but more massive stars, or stars that explode as supernovas, are thought to form more chaotically due to their accretion of infalling gas. If this were true, the jets would move, twist, and spray over a wider area, and the star and its accretion disk would wobble around.
Nevertheless, the jets are straight and pointing nearly 180 degrees opposite to one another in the JWST image of Sh2-284, indicating no signs of movement. This suggests there was no chaos involved in the star’s formation.
The size of the jets appears to scale with the size of the star that produces them, according to star formation models.
“These models suggest that the star has been driving this outflow and is roughly ten times the mass of the sun. It is also still expanding,” Tan said.
Astronomers can learn more about the environment in which stars generating these jets form as well as the inherent characteristics of such stars by determining the energy, straightness, narrow collimation, and age of these jets.
Yu Cheng of the National Astronomical Observatory of Japan, who oversaw the JWST observations, said in the statement, “Before the observation, we didn’t really know there was a massive star with this kind of super-jet out there.”. It is unusual for a massive star to release molecular hydrogen in such a spectacular manner in other parts of our galaxy. “.”.
Cheng makes reference to where Sh2-284 is located in our galaxy. Elements heavier than hydrogen and helium are scarce in the very periphery of the Milky Way’s spiral disk, where this young star is situated 15,000 light-years from Earth. The reason for this is that these elements are created inside stars, and star-formation on the galaxy’s periphery hasn’t been active enough to create many of them. Astronomers (familiarly) call these elements “metals,” even though they aren’t all metals in the traditional sense.
It is fortunate for astronomers to discover a star forming in this low metallicity environment, though, because these conditions are similar to those in the early universe.
Cheng stated, “We can use this massive star as a laboratory to study what was going on in earlier cosmic history because our discovery is shedding light on the formation mechanism of massive stars in low metallicity environments.”.
Its history is more recent (Sh2-284). The jets’ tips are the oldest, and their lengthy length documents the life of the young star.
According to Tan, “the material [in the tips] was close into the star at first, but over 100,000 years the tips were propagating out, and next the stuff behind is a younger outflow.”.
Direct view of the growing star is not possible. Nearer to us in the foreground are the bright stars with the diffraction spikes. As a result of the jets’ interactions with the surrounding interstellar medium, the JWST can identify the structure of Sh2-284, which includes filaments, knots, bow shocks, and linear chains of clumpy material.
These jets and the nebulosity they create are strong, but they are only temporary. The star will eventually come out of its cocoon, fully developed, and perhaps tens of times as massive as our sun. It will have a brief lifespan of a few million years. The metals it forged will enrich space after it explodes, leaving behind a brand-new nebula that is one of star-death rather than birth.
And there will be more star cycles.
