Space enthusiasts have been talking about C/2022 E3, more commonly known as the “green comet” for the last couple of weeks.
The comet, which was estimated to have last passed Earth 50,000 years ago, was discovered as part of a survey that monitors the solar system looking for objects and other moving things that aren’t permanent. The comet is expected to pass nearby in the next few days.
Dr. Lee Carkner, director of the John Deere Planetarium and professor of physics at Augustana College, explained: “Comets come from the outer solar system, and they come into the inner solar system and that’s when we see them, and they go back out and sometimes they come back again. All comets have what we would think of as long periods. They only come around in decades or hundreds of years. We can figure out its orbit by watching it, by tracking it. This particular comet we believe visited the inner solar system about 50,000 years ago.”
That doesn’t mean the comet will be back in another 50,000 years.
“Comet orbits, though, get perturbed and so they’re not constant. We actually think this one is probably going to be ejected from the solar system and it won’t be coming back again,” Carkner said. “They get influenced by the gravity of Jupiter and Saturn when they come in and they get a little bit more or less of a push, so it’s not something you can easily predict in advance.”
While this comet is unusual for its color, Carkner says there’s a scientific explanation for the hue.
“Comets are just a little ball of rock and ice from the outer solar system but when they come into the inner solar system then that rock evaporates, and it makes a big cloud around the comet, and it’s called the coma,” he said.
“That’s really what you see, you’re not really seeing the solid object, you’re seeing a big cloud of gas and ice that’s around it. What happens is when the sun’s light interacts with those chemicals that are there, it can produce different colors so right now there’s some carbon around the comet that’s being energized by the sun’s light and that glows green. The green light is really only visible if you look at it in like a long exposure photograph so that the green is not super apparent unless you look at it very carefully, but comets do sometimes show colors because the gas is around them are being energized.”
Experts say the comet can be spotted in the night sky between February 2-5, if you know where to look.
“The comet is moving, so it appears in a little bit of different place every night,” Carkner said. “Right now, it’s in the northern part of the sky, it’s sort of near the Big and Little Dipper, so if you can find the Big Dipper, it’s sort of near there. It’s moving more towards the northeast, so those are just some landmarks to use to find it. If you’re looking for the comet, it’ll start appearing more northeast and, in a few days, it will be near a bright star in the constellation of Auriga called Capella which is one of the brightest stars in the sky.
“In a few more days, it’ll be close to the planet Mars, so those are so those are just two bright things that you can see out in the sky in the evening sort of in the northeast.” Dr. Carkner says the best way to know exactly where to look is to consult a finding chart.
You’re going to need help seeing the comet. “The comet is fairly bright for a comet but it’s not too easy for us to see with our eyes, especially if you don’t live someplace that’s very dark,” he said. “To really get a view of the comet, you’ll need binoculars or a small telescope. If you have a good pair of binoculars, you might want to give that a shot, especially if you live someplace dark.”
Sky watchers can go out around 8 or 9 p.m. to try to spot the comet, but the brightness of the moon might interfere. If you don’t see it, Dr. Carkner says you’re not really missing anything. “People are always looking for comets and sometimes when we find one, we get really excited, hoping that it will be bright, but we haven’t had a really bright comet for a long time. This isn’t really a super comet; older people might remember Comet Hale Bopp or Comet Hyakutake that appeared in the 1990s. Those were really easily visible with the eye this one really kind of need binoculars to see.” Dr. Carkner has one other piece of advice for anyone who want to venture out for stargazing. “If you want to go out and look for the comet, that’s great, but don’t freeze when you’re out there. It’s a little bit tricky to do observing this time of year, so make sure you dress warm.”