A young protostar discovered in 2012 reveals its details thanks to a spectacular image by James Webb.
On the surface, it looks like some kind of cosmic hourglass. Instead of sand, it looks like interstellar gas patiently flowing through a tiny point of light. It is an illusion: it is not an instrument for measuring time. This image shows the formation of a star. A star in the making. A protostar. your name ? L1527.
This photo was presented on November 16 by NASA, which was having a busy day with the long-awaited maiden flight of the Space Launch System (SLS), marking the official start of the Artemis program and the return of astronauts to the Moon. It was captured by the James Webb Space Telescope with its NIRCam infrared camera.
In the middle of the hourglass the star in pregnancy. If we look closely, we can see that the star appears to be crossed by a horizontal black line. This dark line is not a sign of a protostar, but the sign of another birth: that of a protoplanet. It’s actually a segment of the disk of matter forming around the star.
A protostar only 100,000 years old
In fact, it is an extremely young protostar – estimated to be around 100,000 years old (and very young on a universe scale). In the classification of protostars, it falls into the so-called class 0, the earliest stage of star formation. This classification is based on observations of the star’s luminosity, but also of the “chaos” around it.
There is gas all around, even in the dark areas around L1527. The more red and orange the color, the higher the dust density. But the more the color range goes towards blue, the finer and more dispersed the dust becomes. We can guess when we admire the variations in the colors: the distribution is not entirely homogeneous.
This naturally raises the question: Why doesn’t the star shine everywhere, even in the dark areas?
Precisely because of the disk of matter, which has a masking effect and blocks the star’s light. As a result, the gas is only illuminated where the pane does not obstruct, i.e. “above” and “below”. It’s a bit like a flashlight: the beam of light only goes in one direction (the others are “blocked” by the case and the components of the device).
And this protoplanetary disk is anything but tiny. The American space agency indicates that it is the size of our solar system, the length of which is tens of billions of kilometers. But everything seems tiny from where you are: L1527 is about 450 light-years from Earth in the constellation of Taurus.
Despite the huge gap separating us from the star, astronomers can say that L1527, discovered in 2012, ” does not yet produce its own energy through nuclear fusion of hydrogen », like a normal star. Its shape is not completely spherical but also ” unstable “. Its mass is between 20 and 40% that of the Sun.
This increase in mass is currently underway – this is shown by the gas clusters all around. All of the surrounding stardust is gradually being pulled toward the center, where the protostar is located. This has the effect of feeding the star, allowing it to grow, compress and reach the threshold of equilibrium between its gravitational mass and triggering nuclear fusion.
This is a phase that will be extremely long by our standards. L1527 will not be an independent star in tens and hundreds of thousands of years. But for astronomers, it’s a great opportunity to have a case that can tell us about the formation of stars, planets, and solar systems. Like ours.