Rare double-tailed asteroid spotted changing colors
One of the weirdest objects in the asteroid belt just got weirder. Not only does the asteroid 6478 Gault have two tails like a comet, but now astronomers have spotted it changing color in real time, shifting from red to blue.
Originally discovered way back in 1988, Gault was long thought to be a boring old space rock. It’s about 4 km (2.5 mi) wide and orbits in the asteroid belt between Mars and Jupiter, along with millions of other bits of rock.
It wasn’t until early this year, however, that Gault began attracting more attention. In January the rock was found to be a rare “active” asteroid, meaning it’s spewing dust and forming a long tail like a comet. In this case, Gault actually has two tails, with one stretching half a million miles behind it.
And now, astronomers have taken a closer look and discovered some new wrinkles to its weirdness. Namely, it’s changing colors, and doing so very quickly.
The find was made by an MIT team using the Infrared Telescope Facility (IRTF) in Hawaii. The astronomers observed Gault over two nights, with the aim of studying its composition by analyzing the light reflected off its surface.
Through this analysis, the researchers determined that Gault is dry and rocky. No surprises there. But what was surprising was that the object was changing color, from red to blue within the near-infrared part of the spectrum. And it was doing it very quickly, noticeable within the two-night window of observations.
“We've never seen such a dramatic change like this over such a short period of time,” says Francesca DeMeo, co-author of the study. “Interestingly, you only need a very thin layer to be removed to see a change in the spectrum. It could be as thin as a single layer of grains just microns deep.”
The team believes that the cause of this color change is the same reason Gault has tails: it’s spinning very fast. This centrifugal force is throwing dust off the surface of the rock, creating the tails behind it and changing its color in infrared. Unfortunately, this motion is also causing Gault to self-destruct.
To confirm the theory, the next step is to look for changes in the asteroid’s brightness over time.
The research was published in Astrophysical Journal Letters.