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A new study suggests that the Milky Way has a graveyard of dead stars that spans three times the height of the galaxy. Astronomers discovered ancient stellar remains when they first mapped this “galactic underworld”.
Our galaxy, this one Formed about 13 billion years agoIt was home to billions of stars. Over time, many of these huge objects have collapsed into dense debris.
When a star eight times larger than the Sun burns through its elements and collapses, the star’s outer layers explode in a supernova. Meanwhile, the star’s core condenses into a neutron star or black hole.
It is easy to detect modern neutron stars and black holes forming in the Milky Way because they stay in our galaxy and conform to their shape. But when the researchers tried to find ancient stars in the evolving young Milky Way, they looked like stellar ghosts.
The supernova explosions that caused the stars to collapse actually pushed them into interstellar space. According to their study, published in a recent issue of the journal, the researchers determined that 30% of those stellar remnants have been completely ejected from the galaxy. Royal Astronomical Society Monthly Notices.
By recreating the life cycles of ancient stars, the research team was able to determine where stars reside in and around our galaxy.
“One of the problems with finding these ancient objects is that until now we didn’t know where to look,” said Peter Tuthill, professor at the University of Sydney School of Physics and director of the Sydney Institute for Astronomy. In Australia, in a statement.
“Old neutron stars and black holes formed when the galaxy was young and had a different shape, then underwent complex transformations over billions of years. Finding him was a tall order. Modeling all of this was like trying to find a legendary tomb. The bones of these rare massive stars must have been there, but they seemed to be darkening in mystery.
Researchers faced many challenges as they attempted to track the footsteps and violent death scatters of ancient stars. When a star explodes in a supernova, it gets a “kick”.
“Supernova explosions are asymmetrical and debris is ejected at high speeds – up to millions of kilometers per hour – and, worse still, they occur in an unknown and random direction of each object,” said lead researcher David Sweeney. A student of the Sydney Institute of Astronomy at the University of Sydney, in a statement.
Knowing the size is not enough. The team had to model how stars would behave after a supernova experience and the orbits they might enter. There is no friction to slow interstellar remnants.
“Every remnant ever created is still there, drifting in interstellar space like ghosts,” Sweeney said.
The new map includes where the stars in the Milky Way were born, where they exploded and where they settled.
Comparing the current appearance of the Milky Way with a new model of its star rays shows surprising differences. The galaxy’s distinctive spiral arms seem to disappear under all the kicks of the supernova as it washes away.
The “galactic underworld” appears longer and more protruding than the Milky Way because the supernova’s kicks pushed the debris into a sort of halo formation around the galaxy.
“It was a huge shock,” study co-author Dr Sanjib Sharma, a University of Sydney researcher, said in a statement. I didn’t expect such a drastic change ”.
Astronomically, the research team estimates that stellar ghosts can pass relatively close to our sun.
“Statistically, our closest remnant should be 65 light-years away – roughly our backyard in terms of galaxies,” Tuthill said.
The map will allow scientists to identify individual remains to learn more about the evolution of the galaxy and the stellar timeline.
“Now that we know where to look, we’re developing techniques to find it,” Sweeney said. “I bet the ‘galactic underworld’ won’t be shrouded in mystery for long.”
