As the late Carl Sagan once famously said, “We’re made of star-stuff.” That’s a clever way to illustrate that all the heavy elements in the universe, even those that make up the seven and a half billion humans on Earth, came from the nuclear inferno of a star at some point. Astronomers mapping our galaxy have stumbled upon a region rich in OB stars, which are believed to be instrumental in seeding the universe with the makings of life.
Until just a few years ago, it was impossible to map these distant star clusters with much accuracy, but the ESA’s Gaia project has changed that. The Gaia spacecraft launched in 2013 and uses parallax measurements from its two telescopes to determine the distance and proper motion of sufficiently bright stars. And OB Stars are definitely in that camp.
The international team used Gaia data to explore a new region they’ve dubbed the Cepheus spur. This pocket of stars is located between the Orion arm (where we are) and the next arm out known as Perseus. Astronomers are excited to study the Cepheus spur because it’s rich in these rare OB stars, which enrich the universe with heavy elements every time one of them goes boom.
Astronomers call these “OB stars” because they’re spectral types O or early B (the blue points of light in the above image). That means they’re several times larger than the sun and they burn hot. The bright blue inferno of an OB star doesn’t last long, but that just means they’re quick to fuse hydrogen into heavier elements and then go supernova in a couple of million years. These objects are very rare, with an approximate total of 200,000 in the entire galaxy. That might sound like a big number, but remember there are hundreds of billions of stars in the Milky Way. That’s why finding a large number of OB stars so interesting.
Gaia is the most advanced galaxy mapping mission ever devised.
The researchers have data to show that this is not just a random alignment of OB stars that drifted together. They’re all moving in the same direction, which suggests they’re part of the spiral galactic disk. However, the Cepheus spur appears to be slightly above the galactic plane, which could point to interesting happenings in the distant past.
The Gaia project releases data in chunks. The first was DR1 in 2016, which included 14 months of observational data. DR2 came along in 2018 with 22 months of star mapping data. Currently, DR3 isn’t expected until 2022 because of the COVID-19 pandemic. The more data we have, the more OB stars the researchers behind this study will be able to find as they work to improve the map.
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