Comets viewable from Earth are very rare, creating spectacular events in the night sky. Recently discovered Comet Tsuchinshan-ATLAS -- also called C/2023-A3 or Comet A3 -- could give us a big show as it nears our planet this month, but one lucky astronaut captured some amazing photos of the comet as it rounded the sun in late September.
NASA astronaut Don Pettit, an accomplished astrophotographer (and inventor of the zero-G coffee cup), shared scenic views of Comet A3 via X on Sept. 22. The images show the bright comet against a dark, starry background. Earth's glow is visible as a curve in some of the shots. "It is totally awesome to see a comet from orbit," Pettit wrote. "The perspective of rising through the atmosphere on edge is truly unique from our vantage point."
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Comet A3 has already grown a million times brighter since its discovery in January 2023.
Don Pettit/NASANASA describes comets as "cosmic snowballs," made up of frozen gases, rock and dust. These objects orbit the sun. As they near our star, they heat up and kick off some of their dust and gases. That's how comets get their distinctive tails. Comet A3 is working on growing its plumage. "The comet tail is still too dim to see with your eyes, but it is heading towards the sun and growing brighter every day," said Pettit.
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As Comet A3 gets closer to Earth, it could become brighter than Jupiter or Venus.
Don Pettit/NASAPettit's ISS crewmate Matthew Dominick did the math to help dial in the comet's location so Pettit would know where to point the camera to capture the distant object. Dominick previously tweeted a time-lapse of A3 on Sept. 19, describing the comet as looking like a "fuzzy star to the naked eye."
"This comet is going to make for some really cool images as it gets closer to the sun," Dominick wrote.
There are some unknowns with Comet A3. It won't impact Earth, so don't worry about that. But sometimes comets break up as they near the sun. The comet will be closest to the sun on Sept. 27, an event called perihelion. If it survives, it could potentially brighten enough for observers to easily see it from the ground.
Some talented photographers have been able to capture A3 from our planet's surface, but casual viewers will have a hard time spotting the comet. That could change over the coming weeks. The best viewing opportunities could come in mid to late October. The comet's closest approach to Earth is on Oct. 12.
Comet A3 could become a space celebrity, but comets are notoriously fickle. We'll have to stay tuned to find out if A3 is a stud or a dud. The astronauts on board the ISS will help keep us in the know.