Mysterious Ring Spotted in Massive Stellar Nursery

Image via ESA/Herschel/PACS/SPIRE
Image via ESA/Herschel/PACS/SPIRE

This amazing image comes from the European Space Agency’s Herschel space telescope. In it, we clearly see billowing clouds of gas and dust as they emanate out from NGC 7538, a stellar nursery that is located some 9,000 light-years from Earth. And this isn’t just any stellar nursery; it is a nursery of epic proportions. NGC 7538 births massive stars. It is one of the few regions that is (relatively) close to us that is capable of producing O-type stars, the most massive stars in the universe.

O-type stars are blue stars are the hottest, most massive, and most luminous stars.  They can be up to one million times more luminous than the Sun, with surface temperatures that range from 20,000K to a scorching 50,000K (that’s an astounding 35,000 to 89,000 Fahrenheit ). By comparison, our own Sun is a cool 6,000K at the surface. And these beasts aren’t just hot, they are amazingly massive. Most O-type stars will have a mass between 20 and 100 solar masses.  The radiation from Type-O5 stars (the more massive O-type stars) is so intense that it can ionize hydrogen over a volume of space 1,000 light years across (which would be very unfortunate for any organisms within that area).

However, such extremes don’t just adversely affect nearby organisms (what with the massive amounts of heat and radiation and all), they also spell doom for the stars themselves. Our sun, a G-type yellow star, will spend a total of 10 billion years in the main sequence stage, and it will spend another few billion years expanding as a red giant, before it finally becomes a white dwarf. However, the most massive O-type stars spend less than a million years in the main sequence and explode as supernovae three or four million years after that.

The image pictured above, released on June 12th, reveals a puzzling ring, which you can see in the top center portion of the image. This ring could be the result of several different phenomenon. Violent winds given off by a central star  can result in a ring-like formation, akin to the one pictured here, billowing out across space. Alternatively, a cataclysmic  death of an O-type star (in a stellar explosion called a “supernova”), can also produce this structure. The problem, of course, is that both of these phenomenon require a central star. And as we can clearly see in this image,  in the middle of the ring, the remains of such a star are absent.

But before we start with all the crazy hypotheses about aliens siphoning gas from the interstellar nursery (yes, such things have been proposed before; no, I am not going to give them traffic by linking to them) it’s likely that one of the enormous stars blew this bubble and then moved away before researchers were able to detect it.

More research will be needed to determine the actual cause, but regardless of what mechanism created this structure, the result is beautiful.

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