COLUMBIA — From a dead clot of long forgotten frozen dirt to a visible comet, Holmes is puzzling astronomers and entertaining stargazers.
After more than 100 years in dormancy, Comet Holmes brightened by nearly a million times in less than 24 hours on Oct. 24. Through Tuesday night, the comet continued to shine as brightly as when it first flared.
“It’s one of the strangest things I’ve ever seen,” said Val Germann, president of the Central Missouri Astronomical Association. “We’ve been observing it every chance we’ve had since that time. It is still more than bright enough to be seen by the naked eye.”
Comet Holmes is behaving unlike most comets by brightening at such a far distance from the sun. Most comets have an egg-shaped orbit that brings them close to the sun and then takes them very far away. Comet Holmes has a circular orbit that lasts about seven years and doesn’t bring it very close to the sun, Germann said.
“It’s unusual for the comet to be breaking up and exploding since it is so far away from the sun,” Germann said.
In typical comets, the icy, solid nucleus is close enough to the sun to receive heat. It then sprays vapor and dust from its evaporating surface. Comet Holmes was far from the sun and considered dormant, implying that something had to happen from the inside to make it come apart all at once.
Astronomers speculate that as a comet ages, it develops a hard, frozen shell. The shell is often dark, which could allow the comet to absorb whatever solar heat it receives. As the warmth gradually vaporizes the ice inside, eventually the shell bursts. Some thought Comet Holmes might have been hit by a meteoroid, but astronomers ruled that out because meteoroids are sparse, space is vastly empty and cold comets have exhibited the behavior in the past.
“No one really has a handle on this,” said Alan MacRobert, an astronomer and editor for Sky & Telescope Magazine. “The only way we can find out what will happen is to watch.”
As the comet continues to break up, it will rotate and shed parts in all directions, which will be illuminated by sunlight. Comet Holmes doesn’t have a tail, unlike most comets.
“It looks like a star that is out of focus,” Germann said. “It is a bit of a mystery.”
The comet is predicted to be visible for about the next 10 days.
“The moon also isn’t in the sky during the evening, which would dilute the comet, so the next 10 days provide opportune viewing conditions,” Germann said. “When the moon returns it will somewhat wash the comet out.”
If the comet has destroyed itself, as astronomers predict, Comet Holmes will gradually fade away like a photograph, which could take more than a month.
To find the comet, face northeast between 7 to 8 p.m. Find the W-shaped constellation Cassiopeia and look below the “W” about halfway down to the horizon. There, the brightest star Mirfak can be seen in the constellation Perseus. Mirfak is the top star of a small triangle, with two stars below. The triangle’s lower-left corner is Comet Holmes. The later in the evening you look, the higher Comet Holmes will be.
Comet Holmes was discovered in 1892 by Edwin Holmes in London. At the time, Comet Holmes experienced a lesser outburst than the current one, faded in a few weeks, and then erupted two months later before fading away.
The greatest attribute of Comet Holmes is that everyone has the opportunity to view the extraordinary event.
“You don’t need a telescope or a Ph.D. in physics,” MacRobert said. “All you have to do is go out and look to the right spot in the northeast and there it is — it’s a chance for anybody and everybody to be an amateur astronomer.