February 22, 2024

Astronomers observe an “extragalactic” stellar disk for the first time!

Artist’s impression of the disk and jet of the young extragalactic star HH 1177. Source: ESO/M. Grain Knife/Bulletin
Sergio Messina Sergio Messina Italy meteorite 6 minutes

Mechanisms that lead to the formation of a star with its stellar disk, it’s known. These are physical processes that are universally valid. So If these processes occur during the formation of stars in our galaxy and its disks, it is assumed that the same processes also occur in other galaxiesWhere new stars are born.

indeed So far, no stellar disks have been observed in other galaxies. ALMA’s achievement is the first observation of an extragalactic stellar disk.

How a star is born

During the development phase Stars, dust and gas (its components) that move due to rotation Flatten into the disc. The result is a new rotating star with a rotating protostellar disk.

The galactic molecular clouds from which stars are formed have a rotational motion. As the cloud parts split and each part collapses to form a star, these parts also maintain their rotation. This gets faster and faster as the gas condenses in the new star.

Averagely After 10 to 15 million years after the birth of the star, the disk completely melts. Since part of it fell on the star, a large part of it has evaporated into interstellar space due to the heating of the star, and part of it has been blown away by the star’s winds.

In the end it stays The star with its planetary system and perhaps the asteroid belt.

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What Alma noticed

Alma It is a telescope, or rather a network of 66 telescopes, They are called antennas because they monitor in the range of millimeter waves that are not visible to the human eye. His name stands for Atacama Large Millimeter Array It is located in the Chilean Atacama Desert in the Andes Mountains.

A night view of the antenna network that makes up the ALMA telescope. Credit: iso/b. Tafrishi (twanight.org)

The radiation collected by each antenna is transmitted to the station using interferometric techniques Produces a single image of the observed objectBut as if they were observed by a single telescope the size of the entire network.

ALMA has the ability to vary the distance between antennas, up to a maximum distance of 16 km. It appears as if the observer is a telescope with a mirror with a diameter of 16 kilometers, and the amount of radiation collected is the sum of the radiation collected by the 66 antennas.

The ALMA telescope can do that Detecting the presence of a gaseous structure orbiting the star, with higher velocities toward the center and slower velocities outward; In other words: Rotating star disk. Moreover, it was He discovered the presence of gas that gradually deposited on the star and its mass increasedConfirming that he is a new star.

The discovered star is called HH1177 and is located in the Large Magellanic Cloud. In addition to the Small Magellanic Cloud, there are two galaxies orbiting our Galaxy, which is why they are also called satellite galaxies. The existence of star-forming regions in these clouds was already known.

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H 1177
An image of the star HH1177 with the two jets at different magnifications. Credit: Nature (Nature) ISSN 1476-4687

the ALMA’s discovery of the disk surrounding the star HH1177 is no coincidence. In fact, the previous observations were made using an instrument called contemplation, That’s on VLT (very large telescope) Eso (European Southern Telescope) that The presence of two dipole jets flowing from the star (similar to the cover image), has been discovered. These rays are a feature of star formation, so it was assumed that the star had a protostellar disk.

Thanks to its high spatial resolution, ALMA was the one that detected this disk.

The star HH 1177 arouses curiosity Compared to newborn stars in our galaxy. While the latter is completely hidden in its atmosphere of gas and dust and is barely visible in infrared light, the star is HH1177. Already visible in the visual range.

It is believed that this difference is due to the fact that They were formed in an environment different from ours, precisely because they were poor in minerals and dust. This evidence provides useful information to better understand how star formation processes depend on the properties of the environment in which they form.