ORLANDO, Fla.- – So, I’m telling you there’s a chance. A few weeks ago, Comet ATLAS showed all the promise of the next great comet, coming into view at the end of April. That chance has gotten a little smaller over the past few days, however, as observers have noted changes with ATLAS’s nucleus.
If you were born in the mid-to-late 90s or later, you may never have seen a comet in person. The last show-stopping comet to visit the Northern Hemisphere was Hale-Bopp in 1997. A few comets have been visible since, away from city lights, but none as prominent as Hale-Bopp. The Southern Hemisphere on the other hand has been treated to a couple of very bright comets recently.
ATLAS, named after being discovered by the Asteroid Terrestrial-impact Last Alert System, was found in late December. Up until the first few days of April, ATLAS had been brightening at a very rapid rate.
“We don’t get this too often. Comets are exciting just because they are so unpredictable. We just don’t know how they’re going to act or what they’re going to do,” said Seth Mayo, curator of astronomy at the Museum of Arts and Sciences in Daytona Beach. “It’s kind of fun to follow them and watch how they evolve as they come closer to us and the sun.”
ATLAS is coming to us from the outer reaches of our solar system, the Oort cloud, a cloud of trillions of comets that orbit the sun. Occasionally a comet gets pushed from its deep freeze into an orbit that sends it into our part of the solar system. If ATLAS were to survive its orbit around the sun, it wouldn’t return for another 6,000 years! The famous Halley’s Comet is a short-period comet that comes by every 75-76 years. It was last seen in 1986 and is due back in 2061 to 2062.
A comet is a large chunk of frozen gas, rock and dust that forms a giant glowing head and and tail as they approach the sun. The sun’s heat vaporizes some of the comet’s material that were frozen in the ice forming the iconic outer glow. Solar radiation and solar wind blow away the gas, forming the tail.
“They’re dim when they’re far away and that’s the challenge with them. They only brighten up when they get closer to the sun,” Mayo said. “They make finding them very difficult. We just don’t know they exist until they get closer to us. It’s a good reminder of why we need observation of the sky and why we need to pay attention because these things can kind of come last minute. It’s kind of crazy to think of all of those objects that are out there that we don’t know about.”
ATLAS is mimicking the orbit of the Great Comet of 1844. Some astronomers believe ATLAS could be a piece of that comet, adding to the excitement.
“If ATLAS is indeed a piece of another earlier comet, then that might be good in a way, since it could mean that ATLAS is less likely to do something like disintegrate like Comet ISON did back in 2013,” said Dr. Yan Fernandez, a professor with the the Department of Physics at the University of Central Florida. “But it could also mean that if it’s broken apart before, it could do so again.”
HOW TO SEE
While the brightness of ATLAS has been fading over the last week, it is still visible with a good pair of binoculars or a telescope away from light-polluted skies. It is currently hanging out in the constellation Camelopardalis, just to the left of the more recognizable Big Dipper.
Mayo captured ATLAS moving through the night sky via telescope April 6.
If it wasn’t for coronavirus, Fernandez says they would be showing off the comet at UCF’s campus observatory. The virus has also curbed the daily “Sky Tonight” live show at Lohman Planetarium at MOAS. To make up for this, Mayo has been providing weekly updates digitally on the program Stellarium.
“I basically narrate over that and tell people about the weeks coming up, what you can see in the sky,” Mayo said. “Stargazing and observing the universe is a perfect activity for people to partake in. You just stay at home and look up.”
Depending on the evolution of ATLAS over the next several days or weeks, ATLAS could become visible to the naked eye, reaching second magnitude by the end of April or early May. It may become even brighter through the middle of May. Second magnitude is as bright as the stars in the Big Dipper. On the astronomical magnitude scale, the smaller the number, the brighter the object.
After about magnitude 5 or so, you’ll need the help from binoculars or a telescope. As of April 8, ATLAS has a magnitude of around 9.
It’s not just about the magnitude when it comes to comets but also the size. For example, Hale-Bopp had a magnitude about the same as the brightest star in the summer sky, but it’s nucleus was huge, about 38 miles, adding to the comet’s greatness.
When it comes to ATLAS, however, there are still many questions.
“It sounds like it’s not brightening any more, and is starting to look like other comets do when they are about to disintegrate,” said Fernandez.
We should know more in the next few days/weeks.
As mentioned, comets are notorious for being highly unpredictable anytime these icy bodies pay us a visit.
“Disintegration may have occurred, so it will be interesting to see how it evolves from here. It may not reach a great comet status near perihelion, but it is a wait-and-see kind of thing right now,” said Mayo.
Here’s to hoping ATLAS starts brightening again.