A huge bipolar outflow of gas and dust, grown from the tumultuous birth of a double-star system, has formed a cosmic hourglass — and the James Webb Space Telescope imaged the scene in splendiferous detail.
Referred to as Lynds 483, or LBN 483,, this nebulous outflow is located about 650 light years away. It provides an ideal opportunity for the James Webb Space Telescope to learn more about the process of star formation. (Beverly Lynds was an astronomer who catalogued both bright nebulas – BN – and dark nebulas – DN – in the 1960s)
How does the birth of stars form a nebula like this? Well, stars grow by accreting material from their immediate environs of a gravitationally collapsed cloud of molecular gas. Yet, paradoxically, they are able to spit some material back out in fast, narrow jets or wider but slower outflows. These jets and outflows clash with gas and dust in the surroundings, creating nebulas like LBN 483.
The jets are formed by material with a rich abundance of varied molecules falling onto young protostars. In the case of LBN 483, there’s not one but two protostars, the main star having a lower mass companion that was only discovered as recently as 2022 by a team led by Erin Cox of Northwestern University using ALMA, the Atacama Large Millimeter/submillimeter Array in Chile. The fact that there are two stars lurking at the heart of this butterfly-shaped nebula will be crucial, as we shall see.
We can’t see those two protostars in the JWST’s Near-Infrared Camera image — they are far too small on the scale of this image — but if we could imagine zooming in right to the heart of the nebula, between its two lobes, or “wings,” we would find the two stars snugly ensconced within a dense, doughnut-shaped cloud of gas and dust. This cloud is supplemented with material from the gaseous, butterfly-shaped nebula beyond; the stars grow from material that accretes onto them from the dusty doughnut.
The jets and outflows are not constant but rather occur in bursts, responding to periods when the baby stars are overfed and belch out some of their accreted material. Magnetic fields play a crucial role here, directing these outflows of charged particles.
In LBN 483, the JWST is witnessing where these jets and outflows are colliding with both the surrounding nebulous womb but also earlier ejected material. As the outflows crash into the surrounding material, intricate shapes are formed. The fresh outflow plows through and responds to the density of the material its are encountering.
The whole scene is illuminated by the light of the burgeoning stars themselves, shining up and down through the holes of their dusty donuts, hence why we see the V-shaped bright lobes and dark areas between them where light is blocked by the torus.
The JWST has picked out intricate details in LBN 483’s lobes, namely the aforementioned twists and crumples. The bright orange arc is a shock-front where an outflow is currently crashing into surrounding material. We can also see what look like pillars, colored light purple here (this is all false color, meant to represent different infrared wavelengths) and pointing away from the two stars. These pillars are denser clumps of gas and dust that the outflows haven’t yet managed to erode, like how the towering buttes in the western United States have remained resolute to wind and rain erosion.
Observations by ALMA have detected polarized radio waves coming from the cold dust in the heart of the nebula — dust too cold for even JWST to detect. The polarization of these radio waves is caused by the orientation of the magnetic field that pervades LBN 483’s inner sanctum. This magnetic field is parallel to the outflows that form LBN 483, but perpendicular to the inflow of material falling onto the two stars.
Remember, it is the magnetic field that ultimately drives the outflows, so how it behaves is important for sculpting the shape of the nebula. The dust polarization reveals that about 93 billion miles (150 billion kilometers/1,000 astronomical units) from the stars (similar to the distance of Voyager 1 from our sun), the magnetic field has a distinct 45-degree counter-clockwise kink. This may have an effect on how the outflows shape LBN 483.
This twist is a result of the movements of the growing stars. Currently, the two protostars are separated by 34 astronomical units (3.2 billion miles/5.1 billion kilometers), which is just a little farther than Neptune is from our sun. However, the leading hypothesis suggests that the two stars were born farther apart, and then one migrated closer to the other. This likely altered the distribution of angular momentum (the momentum of orbiting bodies) in the young system. Like energy, momentum has to be conserved, so the excess angular momentum would have been dumped into the magnetic field that is carried by the outflows in the same way that our sun’s magnetic field is carried by the solar wind, causing the magnetic field to twist.
Studying young systems like the one powering LBN 483 is vital for learning more about how stars form, beginning with a giant cloud of molecular gas that becomes destabilized, undergoes gravitational collapse and fragments into clumps, each clump being the womb of a new star system. LBN 483 is particularly interesting in that it does not seem to be part of a larger star-forming region like the Orion Nebula, and so as an isolated spot of starbirth it may operate on slightly different rules to those huge stellar nurseries.
By studying the shape of LBN 483 and the way that shape arises from outflows emanating from the protostars, and plugging those details into numerical simulations of star formation so that they can replicate what the JWST sees, astronomers can revise their models of star formation and better understand not only how all the stars in the night sky formed, but also the events that resulted in the birth of our own sun 4.6 billion years ago.
Who knows, perhaps 4.6 billion years ago, alien astronomers were watching our own sun form. And in another 4.6 billion years, the inhabitants of the binary system currently sitting snugly within LBN 483 could be doing the same thing, while at the same time watching the protracted death of our sun. These astronomers would be separated by billions of years, but connected by the immense longevity of the stars around them.
