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

Protostar L1527 is embedded within a cloud of material that fuels its growth.

Last month, the James Webb Telescope gave us a new and spectacular image of the Pillars of Creation—possibly the most famous image taken by Webb’s predecessor, the hubble space telescopein 1995. Now the telescope is giving astronomers clues about the formation of a new star, with a awesome 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 failing deployment of a sun shield and mirror for several months, began to capture impressive images. First, there was the deep field image of the Universe, released in July. This was followed by images of exoplanet atmospheresthe Southern 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 lovely pictures of Jupiter, including auroras at both poles that result from Jupiter’s powerful 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 stretching across a staggering 340 light-years in the Tarantula Nebula, named for its long, dusty filaments. We were also treated to spectacular images of Neptune and its ringsthat have not been directly observed since Voyager 2 flew by the planet in 1989, and, as already mentioned, the Pillars of Creation.

This latest image is courtesy of Webb’s main camera, the near infrared camera (MIRCam). To capture images of very faint objects, NIRCam’s coronagraphs block any light from brighter objects nearby, similar to how shielding our eyes from bright sunlight helps us focus on the scene in front of us. L1527’s dark clouds are only visible in the infrared, and NIRCam was able to capture features previously hidden from view. Check it out:

Material ejected from the star has cleaned out the cavities above and below it, the boundaries of which glow orange and blue in this infrared view.
Enlarge / Material ejected from the star has cleaned out the cavities above and below it, the boundaries of which glow orange and blue in this infrared view.

NASA/ESA/CSA/STScI/J. depasquale

In 2012, astronomers used the submillimeter array—an array of eight radio telescopes arranged in an interferometer that is also part of the Event Horizon Telescope— to study the accretion disk around L1527 and measure its properties, including rotation. They found that the disk exhibited Keplerian motion, much like the planets in our Solar System, which allowed them to determine the mass of the protostar. So learning more about L1527 could teach us more about what our Sun and Solar System looked like in its infancy.

Protostars are the earliest stage of stellar evolution and typically last about 500,000 years. The process begins when a fragment of a molecular cloud of dense dust and gas gains enough mass from the surrounding cloud to collapse under the force of its own gravity, forming a pressure-supported core. The nascent protostar continues to pull mass towards itself, and the infalling material spirals around the center to create an accretion disk.

The protostar inside L1527 is only 100,000 years old, and therefore does not generate its own energy from nuclear fusion that converts hydrogen to helium, like a full-fledged star. Rather, its energy comes from radiation released by shock waves at the surface of the protostar and its accretion disk. Right now, it’s basically a puffy, sphere-shaped clump of gas between 20 and 40 percent the mass of our Sun. As the protostar continues to gain mass and compress more, 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 has created empty cavities above and below; the bright orange and blue regions represent the boundaries enclosing those regions. (The blue region’s color is because it has less dust in it, compared to the orange regions above, which trap more blue light in the thick dust so it can’t escape.) The accretion disk appears as a dark band. There are also filaments of molecular hydrogen in the image, the result of the collisions of the material ejected by the protostar.

NASA/ESA/CSA/STScI/J listing image. depasquale

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