Astronomers uncover Milky Means galaxy’s most-distant stars


Astronomers have detected within the stellar halo that represents the Milky Means’s outer limits a bunch of stars extra distant from Earth than any identified inside our personal galaxy – nearly midway to a neighbouring galaxy.
| Picture Credit score: AMR DALSH

Astronomers have detected within the stellar halo that represents the Milky Means’s outer limits a bunch of stars extra distant from Earth than any identified inside our personal galaxy – nearly midway to a neighbouring galaxy.

The researchers mentioned these 208 stars inhabit essentially the most distant reaches of the Milky Means’s halo, a spherical stellar cloud dominated by the mysterious invisible substance known as darkish matter that makes itself identified solely by its gravitational affect. The furthest of them is 1.08 million mild years from Earth. A lightweight 12 months is the gap mild travels in a 12 months, 5.9 trillion miles (9.5 trillion km).

These stars, noticed utilizing the Canada-France-Hawaii Telescope on Hawaii’s Mauna Kea mountain, are a part of a class of stars known as RR Lyrae which might be comparatively low mass and sometimes have low abundances of parts heavier than hydrogen and helium. Probably the most distant one seems to have a mass about 70% that of our solar. No different Milky Means stars have been confidently measured farther away than these.

The celebrities that populate the outskirts of the galactic halo could be considered as stellar orphans, most likely originating in smaller galaxies that later collided with the bigger Milky Means.

Additionally Learn | Closest identified black gap to Earth noticed by astronomers

“Our interpretation about the origin of these distant stars is that they are most likely born in the halos of dwarf galaxies and star clusters which were later merged – or more straightforwardly, cannibalized – by the Milky Way,” mentioned Yuting Feng, an astronomy doctoral pupil on the College of California, Santa Cruz, who led the research, offered this week at an American Astronomical Society assembly in Seattle.

“Their host galaxies have been gravitationally shredded and digested, but these stars are left at that large distance as debris of the merger event,” Feng added.

The Milky Means has grown over time by such calamities.

“The larger galaxy grows by eating smaller galaxies – by eating its own kind,” mentioned research co-author Raja GuhaThakurta, UC Santa Cruz’s chair of astronomy and astrophysics.

Containing an interior and outer layer, the Milky Means’s halo is vastly bigger than the galaxy’s essential disk and central bulge which might be teeming with stars. The galaxy, with a supermassive black gap at its middle about 26,000 mild years from Earth, comprises maybe 100 billion–400 billion stars together with our solar, which resides in one of many 4 main spiral arms that make up the Milky Means’s disk. The halo comprises about 5% of the galaxy’s stars.

Darkish matter, which dominates the halo, makes up many of the universe’s mass and is regarded as liable for its fundamental construction, with its gravity influencing seen matter to return collectively and type stars and galaxies.

The halo’s distant periphery is a poorly understood area of the galaxy. These newly recognized stars are nearly half the gap to the Milky Means’s neighbouring Andromeda galaxy.

“We can see that the suburbs of the Andromeda halo and the Milky Way halo are really extended – and are almost ‘back-to-back,'” Feng mentioned.

The seek for life past the Earth focuses on rocky planets akin to Earth orbiting in what known as the “habitable zone” round stars. Greater than 5,000 planets past our photo voltaic system, known as exoplanets, have already got been found.

“We don’t know for sure, but each of these outer halo stars should be about as likely to have planets orbiting them as the sun and other sun-like stars in the Milky Way,” GuhaThakurta mentioned.

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