Astronomers have discovered the oldest living star in the (known) universe — and, remarkably, it’s situated right on our galactic doorstep, just 6,000 light years away, well within the Milky Way. The star, which has the abbreviated name of SM0313, was born 13.6 billion years ago — just 100 or 200 million years after the Big Bang (and a whopping 400 million years before the previous record breaker). It is believed that SM0313 is an elusive Population II star — a star that was formed from the remnants of one of the universe’s very first supernovae. By using SM0313’s spectrographic fingerprint as a baseline, we will hopefully be able to find more ancient stars, eventually allowing us to build up a better picture of what actually happened during (and before?) the Big Bang.

SM0313 (full designation SMSS J031300.36-670839.3) was first spotted by the Australian National University’s Siding Spring Observatory’s SkyMapper Telescope, which is in the process of mapping out a billion stars, galaxies, and asteroids in the southern sky. The Magellan Telescopes in Chile then followed up with some high-resolution imagery. As the astronomers took a closer look at the images, they noticed something rather odd: SM0313 contains almost no iron — less than one ten millionth of the iron found in our local Sun, in fact. (Read: 9 gigapixels, 84 million stars: Peer into the world’s most detailed photo of the Milky Way.)

The remnants of Cassiopeia A, a massive supernova that occurred about 11, 000 light years away from us


As you may know, our current understanding of the formation of the universe (i.e. galaxies, stars, planets) is that supernovae play a very central role. Basically, the theory is that the Big Bang produced vast amounts of hydrogen, helium, and small amounts of lithium. All of the matter in the universe, and all of the matter that will ever be in the universe, is derived from that initial pool of three elements. After a few thousand years, as the universe started to cool, dense regions of hydrogen started to coalesce under gravity — and in some cases, if they became dense enough, a fusion reaction would begin. Thus, the the universe’s first stars were born. These early stars fused hydrogen into helium — but more importantly, when they went supernova, they produced the first instances of carbon, and traces of heavier elements like iron. Slowly but surely, through repeated cycles of star formation and supernovae, the universe started to fill up with heavier elements, eventually resulting in the formation of metal-rich stars and planets like our Sun and Earth. (Read: Supernova explodes nearby in the Cigar Galaxy, but don’t worry, we’re safe.)

SM0313, however, is almost pure hydrogen and helium, with almost no heavy elements at all. This indicates that it’s a Population II star — a star that was formed very early in in the universe’s history, from the remnants of the very first stars (so-called Population III stars, which are hypothetical and thought to be long extinct). SM0313 contains some carbon, and light metals like lithium, magnesium, and calcium, but that’s it. This is surprising to astronomers, because they thought that first-generation supernovae produced a lot of iron. “This indicates the primordial star’s supernova explosion was of surprisingly low energy. Although sufficient to disintegrate the primordial star, almost all of the heavy elements, such as iron, were consumed by a black hole that formed at the heart of the explosion,” said Stefan Keller, operational scientist of the SkyMapper Telescope. [Research paper: doi:10.1038/nature12990 – “A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36−670839.3″]

By fingerprinting SM0313’s spectrographic signature (its elemental composition), we should be able to find more similar stars in the universe — and thus paint a more accurate picture of what the universe was like, soon after the Big Bang. (Read: Hubble captures photo that looks back 13.2 billion years to the creation of the universe.)

How to find SM0313, the oldest star in the sky

How to find SM0313, the oldest star in the sky [Image credit: National Geographic]

While surprising astronomical finds are always nice, it’s even more striking when that discovery is in your own backyard. SM0313 is located just 6,000 light years away from Earth, in the southern constellation of Dorado. If you had a large’ish telescope, you could see it in the night sky yourself. We’re not entirely sure how this star — aged at 13.6 billion years — ended up in the Milky Way (which is roughly 13.2 billion years old). One theory, according to Keller, is that SM0313 was formed in an “isolated gas blob,” which was later absorbed by our rapidly expanding Milky Way.