A giant ‘cavity’ surrounded by two nebulae discovered in the Milky Way

A kind of giant “cavity” surrounded by two nebulae, the Perseus and Taurus cloud, which appeared after – at least – the explosion of a giant star. This is what astronomers have discovered in the Milky Way A study published Wednesday, September 22 in the journal Astrophysical Journal Letters.

The molecular clouds of Perseus and Taurus, as they are called, have long been investigated due to their proximity to Earth – between 500 and 1,000 light-years – and are a straw on the scale of our Milky Way, which stretches 80,000 light-years in diameter.

But also because it harbors star nurseries, which were formed thanks to the mixture of molecular gas and dust that make up these clouds. Finally, because these nebulae seemed to be connected by some kind of thread. Then I excluded observation, because of their distance from our planet.

The funny thing about these two clouds, explains researcher Shmuel Bialy, from Harvard and Smithsonian Astrophysics Center, that is “We find that they are well connected, but not in the way we imagine: through a giant cavity”.

“The type of ball that is empty inside”

This is the first time that scientists have been able to design a 3D map of such a structure, dubbed “Shell Bear Tau”With the help of advanced computing and imaging techniques, and above all a map of the molecular gases of a much larger area, it was drawn up using data from the European space telescope Gaia.

We must imagine a “Sort of a field that would be empty inside”According to Mr. Biali, a “Superbubble”As it is called, its diameter is about 500 light-years (about 4.7 million km), and its outer shell consists partly of two clones of Perseus and Taurus.

Inside the cavity already contains a little dust, “But at a very low density compared to the density of clouds”says cosmologist and astrophysicist Torsten Enslin, associate professor at the German Max Planck Institute for Astrophysics and co-author of the study with Shmuel Bialy. He’s one of the scientists who, in 2019 and 2020, made the first 3D map of dust clouds close to our sun. And this is thanks to data from Gaia about the location and characteristics of more than 5 million stars in this Suburb Solar.

He is a colleague of Mr. Bialy, Kathryn Zucker, a postdoctoral fellow and astrophysicist, who is signing a second study on the topic on Wednesday to explain how scientists have put this map to good use, using algorithms developed in part under her guidance.

“This is the first time that we can use real 3D views, not simulations, to compare theory to observation, and estimate which theories work best.” To clarify the source of this giant cavity and the clouds settled on its surface, She said in a press release from Astrophysics Center.

“We think that because of the supernova, a huge explosion pushed these gases and formed these clouds”Bialy, whose study proposes a multiple supernova scenario. According to this theory, one or more stars exploded at the end of their lives and gradually pushed most of the gas they bathed in back to form this cavity, between 6 million and 22 million years ago.

Today we notice the cavity in its final stage, where it has already slowed down [son expansion]Allow clouds to form About Perseus and the bull, says M. Bialy. He now intends to focus on the younger groups of stars appearing there.

As for Professor Ensslin, he expects to be “The discovery of many other structures” Like Shell Bear Tau. “This bubble is probably one among the others.”He explains, adding that despite its size, it takes up little space in the 3D map produced by his department. It remains to be explored and baptized…