Comet Leonard, which last passed by Earth 80,000 years ago, has been dazzling the night sky in the days leading up to Christmas, and there are only a few days left to observe it before it vanishes forever.
In a spectacular animated sequence of photographs from Friday to Sunday, the imager onboard the Solar Orbiter, a cooperative mission between NASA and the European Space Agency, recorded Leonard speeding across the sky with the Milky Way in the background. Venus and Mercury can also be seen in the animation’s top right corner, with Venus brighter and travelling from left to right.
On Earth, astronomers have been chasing the comet, which is a half-mile (1 kilometre) broad clump of cosmic dust, rock, and ice.
On December 12, comet Leonard made its closest approach to Earth, passing near 21 million miles (34 million kilometres). Until the end of the month, the comet will be visible in both the Northern and Southern hemispheres.
On January 3, it reaches its closest approach to the sun, coming within 56 million miles (90 million kilometres) of our star, or just more than half the distance between Earth and the sun. According to NASA, if it does not disintegrate, its trajectory will propel it into interstellar space, where it will never return.
The comet was also imaged by NASA’s Solar Terrestrial Relations Observatory-A satellite.
From Earth, an ultrafast comet looks to crawl
In January, astronomer Greg Leonard, a senior research specialist at the University of Arizona Lunar and Planetary Laboratory, detected the comet. On January 3, he began following the hazy speck of light.
“The fact that the tail showed up in those images was remarkable, considering that the comet was about 465 million miles out (from Earth) at that point, about the same distance as Jupiter (from Earth),” he said this month.
According to EarthSky, it’s also an ultrafast comet, whizzing through the inner solar system at 158,084 miles per hour (71 kilometres per second), but due to its distance from Earth, it’ll appear to be a slow-moving object.
Use Venus, which is currently visible in the southwestern sky around sunset, to aid in your search for the comet.
“This comet will appear very low above the horizon just after sunset,” Leonard said. “It will skim across the west-southwestern horizon between now up until around Christmastime. The fact that it’s so close to the horizon makes this comet a bit challenging to observe .”
The Oort Cloud, a huge, ice region that surrounds our solar system, is home to most comets with long orbital periods, including Comet Leonard. It’s too far away from Earth for a spaceship to have ever visited.
“When the tug-of-war is won by the gravity of our solar system, an object may start moving inwards, accelerating as it gets closer to the sun,” Leonard explained.
Comets begin to shed part of its material as they approach the sun, forming a halo, or coma, around the object. Comet tails are formed by dust and gas streaming behind them. During their long orbits around the sun, most comets only become visible to us as they pass through the inner solar system, where Earth is located.
Because comets operate as cosmic time capsules of material, they can provide insight into the birth of our sun and solar system.
“As much as we have great science on comets, they’re still highly unpredictable with respect to their size, shape, chemical makeup and behavior,” Leonard said. “A wise and famous comet discoverer once said: ‘Comets are like cats — both have tails, and both do precisely what they want.”
Comet Leonard may have passed by Earth around 80,000 years ago, and ancient human predecessors may have seen it. But it isn’t going to happen again.
“This is the last time we are going to see the comet,” Leonard said. “It’s speeding along at escape velocity, 44 miles per second. After its slingshot around the sun, it will be ejected from our solar system, and it may stumble into another star system millions of years from now.”