Introduction
On December 18th, 2017, a group of Spanish astronomers published their findings of star J0815+4729. This is very special because they may have discovered the oldest star we have ever detected in our galaxy! J0815+4729 was first detected by the William Herschel Telescope and at Gran Telescopio de Canarias as part of the Sloan Digital Sky Survey (SDSS).
J0815+4729 can be found 7,500 light years away from earth and within the halo of the Milky Way. This star has been classified as an ultralow metallicity star which means that its consist of an unusually small amount of elements larger than helium. Knowing this will become critical to estimating J0815+4729's age!
A Side Note On Halos
The halo of a spiral galaxy is the region outside of the galaxys arms. It contains individual stars, smaller clusters of stars, and large amounts of dark matter.
How Can We Estimate J0815+4729’s Age?
Astrophysicist have theorized that the composition of older stars contain the more simplistic elements because they were formed in a time before larger elements had a chance to form in higher concentrations. However, the younger of these stars (which are still ancient) are theorized to contain extra carbon which is a byproduct of the older stars which created the first-generation supernovas.
Here is a pie chart showing off the element composition of our sun’s atmosphere. Although we are interested in comparing the other elements, take a look at how much more hydrogen and helium are present in our sun!
Compared to our sun J0815+4729 has ten times less iron and calcium. It does however, have around 15% more carbon.
Based on our models, these values place J0815+4729 among the second generation of stars suggesting it is approximately 13.5 billion years old!
How Does J0815+4729’s Age Compare to Other Stars?
Unfortunately, we know of at least one star in the milky way which is 13.7 billion years old. But, as our prediction for J0815+4729 is only a rough estimate, it still has a chance at being older!
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Work Cited:
http://www.astronomy.com/news/2018/02/oldest-star-in-mw
https://arxiv.org/abs/1712.06487
http://hubblesite.org/reference_desk/faq/answer.php.id=39&cat=galaxies