Scientists discover a "giant cavity" in the Milky Way

Astronomers have discovered in the Milky Way a giant cavity surrounded by two nebulae, the clouds Perseus and Taurus, which appeared after the explosion of at least one giant star, according to a study published Wednesday.

The molecular clouds of Perseus and Taurus, as they are called, have been the focus of observation for a long time due to their proximity to the Earth, between 500 and 1,000 light years, which is a negligible distance on the scale of our Milky Way galaxy, which is more than 80,000 light years in diameter.

But interest in them is also due to the fact that they harbor factories for stars that were formed thanks to the mixture of molecular gas and dust that makes up these clouds.

It also seemed that these two nebulae are connected by some kind of thread, but this hypothesis was later ruled out due to the distance that separates them from the planet Earth.

"The funny thing about these two clouds is that we find that they are well connected, not in the way you imagine, but through a giant cavity," researcher Shmuel Bialy of the Harvard Center for Astrophysics and the Smithsonian Institution told AFP.

This is the first time that scientists have been able to design a three-dimensional map of such a structure, called a "per-tau shell", using advanced computational and imaging techniques, especially a map of molecular gases in a wider area drawn using data from the European "Gaia" space telescope. .

It should be imagined, Bialy explained, "a kind of ball with an empty interior" or a "super bubble" with a diameter of about 500 light-years (about 4.7 million billion km), and its outer atmosphere is formed partly by the Perseus and Taurus clouds.

The interior of the cavity contains very little dust, "but at a very low density compared to the density of clouds," assistant professor at Germany's Max Planck Institute, astrophysicist and physicist Torsten Enslin, told AFP.

Solar "neighborhood"

Enslin has co-authored this study with lead author Shmuel Bialy, whose results were published in the "Astrophysical Journal Letters".

He is one of the scientists who created in 2019 and 2020, the first 3D map of dust clouds close to our sun.

This happened thanks to Gaia's data on the location and characteristics of more than five million stars in this solar "suburb".

Catherine Zucker, a post-doctoral researcher and astrophysicist, also signed up for a second study on the topic, Wednesday, to explain how scientists used this map well, with the help of algorithms developed in part under her supervision.

"This is the first time that we can use real 3D views, not simulations, to compare theory with observation, and estimate which works best" to explain where this giant cavity and clouds settled on its surface, she said in a statement cited by a statement from the Center for Astrophysics.

"We think it was caused by a supernova, a huge explosion that pushed these gases and formed these clouds," Bialy explained.

According to this theory, one or more stars exploded at the end of the end-of-life phase and gradually pushed the bulk of the gas that was swimming in them back to form this cavity, between 6 and 22 million years ago.