Young stars are like young kids. Their energy is often unruly and can express itself chaotically. We can see the unrestrained energy of two young stars about 650 light-years away as their energetic jets create a distinct hourglass shape with clumps and swirls of gas and dust.
Young stars grow by gobbling up nearby gas and dust. Over time, they can become extremely massive. The most massive stars we know of have up to 200 solar masses. But the flow of matter isn’t a one-way street. Instead, young protostars eject some of the matter back into space with powerful jets.
In this image, the James Webb Space Telescope observed what’s known as Lynds 483 (L483). Lynds 483 is a dense cloud of gas and dust where new stars are forming. Two young protostars are hidden in the heart of L483. The stars are tiny in this image, but they’re there, and they make their presence known by shaping their surroundings.
The JWST is the largest, most powerful space telescope ever deployed. It sees further into the infrared than any previous infrared telescope and has extremely high resolution. That means that when it is pointed at objects already observed by other telescopes, it reveals even more detail. This is true of Lynds 483.
L483 features dense clouds of gas and dust that are barriers to observation in visible light. The JWST was designed and built to observe targets like this.
What looks like twin flames are known as Lynds 483 (L483), ejections from two actively forming stars at the center. The stars themselves are hidden in a teeny, opaque disk of dust that fits into one pixel. This is the most detailed image of L483 to date, delivered in high-resolution near-infrared light by the James Webb Space Telescope. Image Credit: NASA, ESA, CSA, STScI
All stars, including protostars like the ones in L483, rotate. As they draw gas and dust toward themselves, the matter forms a swirling accretion disk around the star. However, not all of the matter in this circumstellar disk becomes part of the star. Instead, some of it is funnelled toward the poles with the help of powerful magnetic fields. Powerful protostellar jets come out of the stars’ poles and reach speeds of several hundred km per second.
The jets are intermittent, not continuous because the young stars accrete matter intermittently. They’ve been emitting their matter for tens of thousands of years in tight jets and in slower outflows. As recent jets slam into previously ejected material, the differing speeds and gas densities create lumps and swirls.
These hourglass-shaped clouds of gas are chemically rich, and chemical reactions over time create methanol, carbon dioxide, and other organic molecules. A 2019 paper said that these reactions take place mostly in the hot corino, the hot, innermost region around young stars. Complex organic molecules (COMs) have also been found in “the transition region between the outer infalling-rotating envelope and the centrifugal barrier, i.e., the radius at which the kinetic energy of the infalling material is converted into rotational energy,” the paper states. This is where the centrifugal force becomes strong enough to counteract the inward pull of gravity.
The two protostars responsible for all this visual mayhem and chemical activity are at the very center of the hourglass shape in an opaque band of thick dust. Above and below this disk are orange cones of starlight, visible through thinner dust.
There is also a pair of dark cones oriented at 90 degrees from the cones. This is not the blackness of empty space; it’s a pair of diametrically opposed regions of thick dust. Almost no light pierces this dust, though even here, the power of the JWST is clear. It’s able to spot dim yet visible background stars beyond L483.
In the upper right of the image, a prominent orange arc marks the location of a shock front, where outflowing gas and dust in the jets slammed into a dense region in the interstellar medium.
Just below that, where orange meets pink, the JWST’s incredible power has revealed a previously unseen detail in L483. This tangled pattern of thin, flimsy-looking filaments has never been seen before, and this messy region still needs explanation.
The gas and dust appear to be thicker in the lower part of the image compared to the upper part. The press release presenting the image urges us to “Zoom in to find tiny light purple pillars.”
This zoom-in image shows the lower portion of L483. The tiny light purple pillars are oriented to the protostellar jets. The pillars form because the gas and dust are so dense here that they can’t be easily blown away. Image Credit: NASA, ESA, CSA, STScI
The JWST has answered some of astronomers’ existing questions and posed new ones. However, much about L483 still needs explanation. Its shape is partly symmetrical and partly asymmetrical. Astronomers will work together to piece together the object’s history, calculate how much material the stars have ejected, and determine which chemicals have been created and in what abundance.
The protostars in L483 are extremely young and won’t become main sequence stars for millions of years. When they finally begin their lives of fusion, they’ll be similar in mass to the Sun. At that point, there will be no hourglass of gas and dust and no jets. The jets will have swept the region clean and will cease to be emitted.
However, some gas and dust will remain in circumstellar disks around the stars. Planets will likely form in those disks, but only in the far-off, distant future.
At that point in time, the JWST will be only dimly remembered, if at all. Imagine what telescopes we’ll have at our disposal if humanity somehow survives that long.
