Located about 212 million light-years from Earth, the massive spiral galaxy NGC 6872 has been known to astronomers for decades. But it wasn't until a recent survey of nearby star-forming regions that NASA scientists realized just how big it truly is. New data shows that, from tip-to-tip across its two outsized spiral arms, this galaxy measures a whopping 522,000 light-years across — making it more than five times the size of the Milky Way. NASA now says it's the largest spiral galaxy that has ever been discovered.
Astronomers were able to award NGC 6872 with this distinction by analyzing data acquired from the Galaxy Evolution Explorer (GALEX) mission, which is now located at California Institute of Technology in Pasadena.
While scanning the area around the galaxy, NASA scientists were taken aback at the volume of ultraviolet light coming from its younger stars — an indication that there was more to this galaxy than initially met the eye.
NASA made the announcement at the American Astronomical Society meeting. The team credited with the discovery includes Rafael Eufrasio of the Catholic University of America and NASA's Goddard Space Flight Center, and colleagues from the University of Sao Paulo in Brazil and the European Southern Observatory in Chile.
Assuming the galaxy has a similar star distribution to the Milky Way, it could contain anywhere from 500 billion to 2 trillion stars.
Interestingly, NGC 6872 had a recent run-in with a nearby lens-shaped galaxy called IC 4970 (which is about a fifth the size of NGC 6872 ). Models show that as the two galaxies collided, it kindled a wave of star formation along NGC 6872's spiral arms. Using supplementary data from the Very Large Telescope, the Two Micron All-Sky Survey and the Spitzer space telescope, NASA confirmed that the stars at the outer reaches of NGC 6872 are older than the ones sitting at the interior — a phenomenon they attribute to the collision.
And it's this exact kind of galactic interaction that may be responsible for not just the massive size of NGC 6872, but for the iterative formation of galaxies in general. That said, the collision may have produced the opposite effect — the potential spawning a new small galaxy.
Source and images: NASA.