Star With Unusual Chemistry Came From Out Of Town

Using the Subaru Telescope, astronomers have confirmed the existence of a star that may have originated in a dwarf galaxy that has since merged with the Milky Way.

AsianScientist (May 16, 2019) – Astronomers have discovered a star in the Milky Way galaxy with a chemical composition unlike any other star in our galaxy. The findings are published in Nature Astronomy.

When analyzing survey data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), an international team of researchers noticed the star J1124+4535 for its unusual chemical composition. Initial observations showed that J1124+4535, located in the constellation Ursa Major (Big Dipper), had low abundances of certain elements such as magnesium.

Follow-up observations with the High Dispersion Spectrograph on the Subaru Telescope confirmed the low levels of magnesium but found comparatively high levels of europium. This is the first time an element ratio like this has been observed in a star in the Milky Way.

The researchers noted that stars form from clouds of interstellar gas, and the element ratios of the parent cloud impart an observable chemical signature on stars formed in that cloud. Therefore, stars formed close together have similar element ratios. However, the composition of J1124+4535 does not match that of any other stars in the Milky Way, indicating that it must have formed elsewhere in the universe.

Galaxy evolution models and simulations suggest that galaxies like the Milky Way grow by absorbing neighboring dwarf galaxies. Thus, the team thinks that J1124+4535 was originally formed in a now-vanished dwarf galaxy which merged into the Milky Way.

The article can be found at: Xing et al. (2019) Evidence for the Accretion Origin of Halo Stars With an Extreme R-process Enhancement.


Source: National Astronomical Observatory of Japan; Photo: Pixabay.
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