A cosmic hourglass: Webb captures an image of a protostar shrouded in dark clouds

The L1527 protostar is embedded in a cloud of matter that fuels its growth.

Last month, the James Webb Telescope offered us a spectacular new image of the Pillars of creation-arguably the most famous image taken by Webb’s predecessor, the The Hubble Space Telescopein 1995. Now the telescope is giving astronomers clues about the formation of a new star, with a great picture of a dark, hourglass-shaped cloud surrounding a protostar, an object known as L1527.

as we have previously reportedthe James Webb Space Telescope launched in December 2021 and, after a suspenseful sunshade and mirror deployment over several months, began capturing stunning images. First there was the deep field image of the Universe, released in July. This was followed by images of atmospheres of exoplanetsthe South Ring Nebula, a cluster of interacting galaxies called Stephan’s Quintet, and the Carina Nebula, a star-forming region about 7,600 light-years away.

In August, we received gorgeous pictures of Jupiter, including auroras at both poles that result from Jupiter’s strong magnetic field, as well as its thin rings and two of the gas giant’s small moons. This was followed a month later by a mosaic image showing a panorama of star formation spanning a staggering 340 light-years in the Tarantula Nebula, so named for its long, dusty filaments. We were also treated to spectacular images of Neptune and its ringswhich have not been observed directly since Voyager 2 flew by the planet in 1989, and, as already mentioned, the Pillars of Creation.

This last image is courtesy of Webb’s main imager, the Near infrared camera (MIR Cam). To capture images of very faint objects, NIRCam’s coronagraphs block out any light from nearby brighter objects, much like shielding your eyes from sunlight helps us focus on the scene in front of us. L1527’s dark clouds are only visible in infrared, and NIRCam was able to capture features that were previously hidden. Check it out:

Enlarge / Material ejected from the star has cleared cavities above and below, the edges of which glow orange and blue in this infrared view.


In 2012, astronomers used the Submillimeter array– a collection of eight radio telescopes arranged in an interferometer which is also part of the Event Horizon telescope – for study the accretion disk around L1527 and measure its properties, including rotation. They found this the disk exhibited Keplerian motion, much like the planets of our solar system, which allowed them to determine the mass of the protostar. So learning more about L1527 could tell us more about what our own early Sun and solar system looked like.

Protostars are the earliest stage of stellar evolution, which typically lasts about 500,000 years. The process begins when a fragment of a molecular cloud of dense dust and gas acquires sufficient mass from the surrounding cloud to collapse under the force of its own gravity, forming a pressurized nucleus. The fledgling protostar continues to pull mass towards itself, and material spiraling around the center creates an accretion disk.

The protostar in L1527 is only 100,000 years old and therefore does not generate its own energy from nuclear fusion that turns hydrogen into helium, like a star in its own right. Its energy comes rather from the radiation emitted by the shock waves on the surface of the protostar and its accretion disk. Right now, it’s basically a puffy, sphere-shaped clump of gas that’s between 20 and 40 percent of the mass of our Sun. As the protostar continues to gain mass and compress further, its core will continue to heat up. Eventually it will get hot enough to trigger nuclear fusion, and a star will be born.

The Webb image above shows how material ejected from L1527’s protostar created empty cavities above and below; the bright orange and blue regions represent the boundaries describing these regions. (The blue region’s color is because it has less dust in it than the orange regions above it, which trap more blue light in the thick dust so it can’t escape.) The disk accretion appears as a dark band. There are also molecular hydrogen filaments in the image, the result of shocks from the protostar’s ejection material.

Listing image by NASA/ESA/CSA/STScI/J. DePasquale

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