The star SDSS J0715-7334, found on the outskirts of the Milky Way near the Large Magellanic Cloud, contains less than 0.005% of the metals found in the sun. It is made almost entirely of hydrogen and helium and is the closest known analogue to the first stars that formed in the universe.
The object was flagged for follow-up in 2014 by Kevin Schlaufman as part of the fifth generation of the Sloan Digital Sky Survey. A team analysed high-resolution spectra taken with the Magellan Clay Telescope and its echelle spectrograph to measure the star's chemical makeup. Those measurements show only trace amounts of carbon and iron.
The researchers conclude the star formed from gas that had recently mixed with material ejected by a Population III star's supernova. By working backwards from the element ratios, astronomers can probe the mass of that original Population III star and the energy of its explosion. The findings appear in the journal Nature Astronomy.
Difficult words
- outskirt — area at the outer edge of a placeoutskirts
- metal — elements heavier than hydrogen and heliummetals
- analogue — thing that is similar in important ways
- follow-up — additional action or test after an earlier one
- spectrum — range of light from an objectspectra
- supernova — explosion at the end of a star's life
- trace — a very small amount of something
- probe — to examine or study something carefully
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Why do the researchers call this star an analogue of the first stars in the universe?
- How can working backwards from element ratios help astronomers learn about an earlier supernova?
- Which instruments mentioned in the article were important for the study, and why do you think they were used?
- Do you think finding stars with very low metals changes what we know about star formation? Why or why not?
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