An obscure comet discovered more than a century ago suddenly became about a million times brighter late last month, wowing amateur astronomers in Colorado and around the world.
Scientists are so intrigued with the changeable Comet Holmes, they asked for – and got – emergency viewing time on the over-scheduled Hubble Space Telescope last week.
The astronomers are eager to see the results, said Jimmy Westlake, an astronomy professor at Colorado Mountain College in Steamboat Springs.
“It was like the full moon becoming as bright as the sun – overnight,” Westlake said.
“And it keeps changing, every day,” he said. “Did it get hit by a piece of space junk? Did the comet fragment? Everyone in the world is waiting to see what happens next.”
The comet was discovered in the 1890s by amateur astronomer Edwin Holmes. At the time it was also strangely luminous for a few months, said Chris Peterson, owner of a robotic telescope in Guffey that’s used to track big meteors for the Denver Museum of Nature & Science. Holmes completes its orbit every seven years, but it never gets close enough to the sun to go through the regular, bright outgassings of more well-known comets, such as Halley or Hale-Bopp, he said.
“Normally, comets become active for the obvious reason that they’re quite close to the sun,” Peterson said.
Not Holmes.
“It’s actually been lost at various times,” Peterson said. “Decades have gone by when nobody really knew where it was.”
Which makes Holmes’ recent appearance all the more spectacular, he said.
Scientists suspect that the dusty and icy comet has a porous or weak surface that either broke apart or sunk in on itself, Peterson said.
That could have happened if Comet Holmes hit a bit of space debris, or if it just collapsed in on itself, perhaps because the sun’s heat happened to reach a vulnerable pocket of gas or ice inside it.
“What we’re seeing is volatile material – a mixture of dust and gases that are boiled off the surface and diffusing spherically,” Peterson said. “So you get a bigger and bigger ball of dust out there, reflecting sunlight.
“With binoculars, it’s amazing – it’s this huge, fuzzy, cotton-candy ball, as big as the full moon,” Peterson said. “It’s pale gold, and it even shows up through light pollution, in the middle of the city.”
Ray Villard, news chief at the Space Telescope Science Institute, which schedules Hubble’s viewing time, called the comet “really bizarre and wacky.”
“We call this a target of opportunity,” Villard said. “The comet went through an unexpected change, and we wanted to be able to look at it.”
Researchers are still analyzing last week’s pictures, he said. Hubble won’t be able to snap detailed images of the comet’s core, Villard said, but the telescope’s images may reveal telling details of the comet’s debris cloud.
Holmes’ core is probably 2 to 6 miles across, Peterson said.
Katy Human: 303-954-1910 or khuman@denverpost.com
Get a gander at comet
Binoculars are the tool of choice to see Comet Holmes, according to Chris Peterson, an astronomer in Guffey.
Surrounded by a halo of dust, the comet should appear just north of northeast, in the constellation Perseus.
At 7 p.m., Peterson calculated, Holmes should be about 30 degrees high in the sky. At midnight, it’s almost directly overhead.
For a more detailed map showing nearby constellations, go to and click on “sky map.”
Sources: and Chris Peterson
