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Astronomers claim to have found the oldest star ever discovered: a 13.5 billion year old sun hovering over the edges of our Milky Way, according to a new study.
The star may seem trivial, 2MASS J18082002-5104378 B, but its content is quite special. According to researchers at John Hopkins University, Carnegie observatories in the United States and Monash University in Australia, it is considered to be the poorest metal thin-film star system.
Composed only of hydrogen, helium and some lithium, this little star is almost entirely made from the material that formed shortly after the Big Bang, an event that would have occurred 13.7 billion years ago. The team thinks the star was born just 200 million years later – a point in the cosmological timeline of events.
Since the star is so old, it could mean that its galactic quarter, a small slice of the Milky Way, is at least three billion years older than previously thought. The results were published in The Astrophysical Journal (here is the free version of arXiv).
"This star is perhaps one in 10 million," said Kevin Schlaufman, lead author of the article and associate professor of physics and astronomy at Johns Hopkins University in the United States, earlier this week. "It tells us something very important about the first generations of stars."
Does my crown look big?
The majority of the old stars were probably giants, he said. Stars are born when interstellar gas clouds collapse and the more a cloud contains mass when it begins to fall on itself, the more star masses it produces is great.
Hydrogen is a poor coolant, so the first gas clouds were very hot – up to 1,000 Kelvin (726.85 degrees Celsius). This heat means that the molecules in the cloud have more energy, so they squirm more, so you need more mass to form a star. The stars produced from these early clouds were large, metal-poor, and had a short, violent life.
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Larger UMP stars are relatively common; Astronomers have found 30 with a mass equivalent to that of the Sun. But until now, it was not known if old, small, poor metal stars could exist and 2MASS J18082002-5104378 B shows that this is possible after all.
The new star represents only 14% of the mass of the Sun and has the same heavy metal content as Mercury. In comparison, the Sun has a heavy element content of 14 Jupiters, indicating that it was made up of much older stellar debris, with a higher proportion of metals and heavier elements.
Another advantage is that stars such as 2MASS J18082002-5104378 B have an incredibly long service life. Scientists believe that such stars, which represent about 0.075 to about 0.50 of our solar mass, can theoretically last billions of years.
"If our inference is correct, the low mass stars whose composition is exclusively from the Big Bang may exist," said Schlaufman, also affiliated with the Institute for Data Intensive Engineering and Science at the university. "Even though we have not yet found an object of this type in our galaxy, it may exist." ®
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