That’s because a comet that orbits between Jupiter and the sun will make its closest approach to Earth in centuries.
“The fuzziness is just because it’s a ball of gas basically,” Tony Farnham, a research scientist in the astronomy department at the University of Maryland, said Saturday morning after a long night studying the comet at the Discovery Channel Telescope, about 40 miles southeast of Flagstaff, Arizona. “You’ve got a 1-kilometer solid nucleus in the middle, and gas is going out hundreds of thousands of miles.”
The comet glows green because the gases emit light in green wavelengths.
The ball of gas and dust, sometimes referred to as the “Christmas comet,” was named 46P/Wirtanen, after astronomer Carl Wirtanen, who discovered it in 1948. It orbits the sun once every 5.4 years, passing by Earth approximately every 11 years, but its distance varies and it is rarely this close. As the comet passes by, it will be 30 times farther from Earth than the moon, NASA said.
The proximity of 46P/Wirtanen provides an opportunity to research the tail of the comet and see farther into the nucleus.
“The fact that it’s brighter means we can study a lot of different gas types that we normally can’t study because they’re too faint,” Farnham said, adding that researchers could learn more about where the comet formed and how it evolved.
The comet is also interesting to scientists because it is hyperactive, meaning it emits more water than expected, a phenomenon that is relatively rare.
The comet is visible now but it will shine even brighter Sunday as it reaches its closest approach, 7.1 million miles from Earth. It is among the 10 closest approaches by a comet in 70 years, NASA said. Only a few of those could be seen with the naked eye.
Don’t worry if you miss the comet Sunday. It should be just as visible for a week or two because its appearance will change gradually.
This article originally appeared in The New York Times.