Impressions are gained in a fluid, global, diffused way. The rugged extent of the colored rings fossil galaxy is known as Heracles. The yellow dot indicates the position of the sun. Credit: Danny Horta-Darrington (Liverpool John Moores University), NASA / JPL-Caltech and SDSS
Scientists working with data from the Sloan Digital Sky Services Apache Point Observatory Galactic Evolution Experiment (APOGE) have discovered a “fossil constellation” hidden in the depths of our own galaxy.
The result, published today Monthly instructions of the Royal Astronomical Society, Our understanding of how the galaxy grew into the galaxy we see today may be shaken.
The Milky Way galaxy was probably predicted ten billion years ago, when our galaxy was still in its infancy. Astronomers named him Heracles, the ancient Greek hero who received the gift of immortality when the galaxy was formed.
The remains of Heracles make up about one-third of the Milky Way’s circular halo. But if the stars and gas of Heracles make up such a large percentage of the galactic halo, why haven’t we seen it before? The answer lies in its location from the depths of the galaxy.
“To find a fossil galaxy like this, we had to look at the detailed chemical composition and motions of thousands of stars,” says Ricardo Schiavone, lead researcher at John Moores University (LJMU) in Liverpool, UK. Team. “It’s especially difficult for the stars in the middle of the galaxy to do so, as they are hidden from view by the international dust clouds. Apogee lets us pierce through that dust and look deeper into the heart of the galaxy than ever before.”
All-sky image of galaxy stars visible from Earth. The colored rings show the approximate extent of the stars that come from the fossil galaxies known as Heracles. The small objects at the bottom right of the image are large and small magellanic clouds, which are two small satellite galaxies in the galaxy. Credit: Danny Horta-Darrington (Liverpool John Moores University), ESA / Gaia and SDSS
APOGEE does this by taking a spectra of stars into nearby infrared light, instead of visible light, which is obscured by dust. In its ten years of observational life, Apogee has measured spectra for more than half a million stars in all galaxies, including its previous dust-obscure core.
Announcing the results, LJMU graduate student Danny Horta, the lead author of the paper, explains, “To find unusual stars in the densely populated heart of the Milky Way, it is necessary to examine such a large number of stars as to find a needle in it.” A haystack. “
To separate the stars connected to Heracles from the stars of the original galaxy, the team used both the chemical composition and velocity of the stars measured by the APOGE instrument.
“Of the thousands of stars we saw, a few hundred had surprisingly different chemical compositions and velocities,” Horta said. “These stars are so different that they could only have come from another galaxy. By studying them in detail, we can find out the exact location and history of this fossil galaxy.”
Because galaxies are formed by the merger of smaller galaxies over time, fossils of older galaxies are often found in the outer halo of the Milky Way, a vast but very scattered cloud of stars starring the main galaxy. But since our galaxy is bound from the inside, we need to look at the most central parts of the galaxy’s halo to find an early merger, which is buried deep inside the disk and bulge.
Originally associated with Heracles, the stars today make up about a third of the entire Milky Way galaxy – meaning that this newly discovered ancient collision must have been a major event in the history of our galaxy. This suggests that our galaxy may be unusual, as most similarly large spiral galaxies were very quiet in early life.
“As our cosmic home, the galaxy is already special to us, but this buried ancient galaxy makes it even more special,” says Xiaovan.
Karen Masters, SDSS-IV comments, “APOGEE is one of the main surveys of the fourth phase of SDSS, and this result is an example of the amazing science anyone can do. We have now completed almost ten-year missions.”
And this new era of discovery will not end with the cessation of APGGE observations. The fifth phase of SDSS has begun taking data, and its “Milky Way Mapper” will consider APGG’s success in measuring ten times the spectra across all parts of the galaxy, light using near-infrared light, and sometimes both.
A new family of stars discovered in the Milky Way shed new light on the formation of the galaxy
“Evidence from Apogee for the presence of Bald Halo’s major building blocks in the Inner Galaxy,” Danny Horta et al., 2020 Nov. 20, Monthly instructions of the Royal Astronomical Society: Arxiv.org/abs/2007.10374].
Slogan provided by Digital Sky Survey
Citation: Astronomers have discovered a new ‘fossil galaxy’ buried inside the Milky Way (2020, November 20) (2020, November 20) November 20, 2020 https://phys.org/news/2020-11-astronomers-fossil -galaxy-deep-milky.html
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