A Red “Snow White”

Astronomers at the California Institute of Technology have discovered that “Snow White,” a dwarf planet officially named 2007 OR10, is actually red.  Time to come up with another name!  But why was it called Snow White to begin with?

It was originally called Snow White because Mike Brown, a professor of planetary astronomy at Caltech, had guessed that it was an icy body formed by a breakup of another dwarf planet.  Since he thought the planet would be icy and water ice appears to be white, the name fit.

Dr. Brown and his team have discovered that the little planet known as Snow White is actually red.  And it is covered with water ice, which is usually white.  So what makes this little planet red?

The explanation is probably in Snow White’s disappearing atmosphere.  In 2002, Dr. Brown helped to discover a similar dwarf planet, Quaoar.
Quaoar was covered with volcanoes that spewed an icy slush.  Quaoar was too small to hold on to its atmosphere, so it has slowly drifted away into space. What was left behind was some methane, the heaviest gas thought to have been in its atmosphere.  The methane, after being exposed to space radiation, combined into long hydrocarbon chains.  The hydrocarbon chains rest on the icy surface, giving Quaoar a rosy hue.

The spectrum of “Snow White” looks similar to the spectrum of Quaoar, an indication that the planets’ atmospheric compositions may be the same.

“That combination — red and water — says to me, ‘methane,'” Brown explains. “We’re basically looking at the last gasp of Snow White. For four and a half billion years, Snow White has been sitting out there, slowly losing its atmosphere, and now there’s just a little bit left.”

Mike Brown doesn’t yet know that Snow White has methane; there’s no evidence, other than the comparison with Quaoar.  It will take more investigation, with a larger telescope, to determine that for sure.

And now that the astronomy community has determined that Snow White is an interesting object to study, it needs a real name.

Before the discovery of water ice and the possibility of methane, “2007 OR10” might have sufficed for the astronomy community, since it didn’t seem noteworthy enough to warrant an official name. “We didn’t know Snow White was interesting,” Brown says. “Now we know it’s worth studying.”

That’s science–there’s always more to discover, even when it seems like all of the interesting discoveries have already been made.
Stay tuned to see what they re-name “Snow White.”

Explore how spectroscopy is used to determine the atmospheric composition of distant planets in our space investigation.