Astronomers Discover Milky Way Galaxy’s Most-Distant Stars

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

The researchers mentioned these 208 stars inhabit essentially the most distant reaches of the Milky Way‘s halo, a spherical stellar cloud dominated by the mysterious invisible substance referred to as darkish matter that makes itself identified solely by way of its gravitational affect. The furthest of them is 1.08 million gentle years from Earth. A lightweight 12 months is the gap gentle 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 referred to as RR Lyrae which are 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 p.c that of our sun. No different Milky Manner stars have been confidently measured farther away than these.

The celebrities that populate the outskirts of the galactic halo may be considered as stellar orphans, in all probability originating in smaller galaxies that later collided with the bigger Milky Manner.

“Our interpretation concerning the origin of those distant stars is that they’re most certainly born within the halos of dwarf galaxies and star clusters which have been later merged – or extra straightforwardly, cannibalised — by the Milky Manner,” mentioned Yuting Feng, an astronomy doctoral pupil on the College of California, Santa Cruz, who led the research, introduced this week at an American Astronomical Society assembly in Seattle.

“Their host galaxies have been gravitationally shredded and digested, however these stars are left at that enormous distance as particles of the merger occasion,” Feng added.

The Milky Manner has grown over time by way of such calamities.

“The bigger galaxy grows by consuming smaller galaxies — by consuming its personal type,” mentioned research co-author Raja GuhaThakurta, UC Santa Cruz’s chair of astronomy and astrophysics.

Containing an inside and outer layer, the Milky Manner’s halo is vastly bigger than the galaxy’s primary disk and central bulge which are teeming with stars. The galaxy, with a supermassive black gap at its middle about 26,000 gentle years from Earth, accommodates maybe 100 billion–400 billion stars together with our solar, which resides in one of many 4 major spiral arms that make up the Milky Manner’s disk. The halo accommodates about 5 p.c 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 kind 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 Manner’s neighboring Andromeda galaxy.

“We are able to see that the suburbs of the Andromeda halo and the Milky Manner halo are actually prolonged – and are nearly ‘back-to-back,'” Feng mentioned.

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

“We do not know for certain, however every of those outer halo stars must be about as prone to have planets orbiting them because the solar and different sun-like stars within the Milky Manner,” GuhaThakurta mentioned.

© Thomson Reuters 2023