Comets

Comets are remnants from the early days of the solar system, billions of years ago. Primarily made of ice and dust, these "dirty snowballs" orbit the sun and in habit the Oort cloud, an area in the outskirts of the solar system beyond Pluto. As comets approach the inner solar system, solar wind from the sun can sweep dust back into a long tail. When these comets are close enough to Earth, they can appear as dazzling objects in the night sky. Space probes from Earth have visited several comets to learn more about their composition. Learn more about comets, icy wanderers in the solar system.

Related Topics: Asteroids, Meteors, Shooting Stars and Fireballs, Rosetta Spacecraft, Stargazer Photos 

Latest Updates

a blue-green comet in the night sky

40 years ago, a comet came out of the blue in a surprise Earth flyby. Here's what we know now.

By Joe Rao published

Forty years ago this month, there came a show stopping celestial sight — literally a bolt out of the blue — as a new comet was discovered close to Earth.

a large rock in space from which is streaming a white cloudy haze

James Webb Space Telescope discovers water around a mysterious comet

By Robert Lea published

The James Webb Space Telescope has imaged a rare main asteroid belt comet, discovering water around the object that could help reveal how Earth became a wet planet teeming with life.

An artist's depiction of the interstellar comet 'Oumuamua, as it warmed up in its approach to the sun and outgassed hydrogen (white mist), which slightly altered its orbit.

Sorry, E.T. fans: Interstellar visitor 'Oumuamua isn't an alien spacecraft. It's just passing gas.

By Tereza Pultarova published

Since its arrival in the solar system in 2017, interstellar object 'Oumuamua has puzzled scientists. Two American astronomers now think they have solved one of the space rock's biggest mysteries.

a bright comet in the sky over a large antenna dish

A comet coming in 2024 could outshine the stars - if we're lucky

By Joe Rao published

A comet recently discovered zooming through our solar system has the potential to be quite bright when it arrives late in 2024, but comets have let us down before.

a pyramid of light in the night sky

See the night sky shine with ghostly zodiacal light this month

By Robert Lea published

For the next few weeks in March, the sky to the west is illuminated by a pyramid of ethereal glow after twilight known as the zodiacal light.

Comet ISON seen making a close approach to the sun in 2013. A newly discovered comet, C/2023 A3, will appear far brighter in the sky if it survives the sun's rays in fall 2024.

Bright new comet discovered zooming toward the sun could outshine the stars next year

By Stephanie Pappas published

The newly discovered comet C/2023 A3 is making a close approach around the sun for the first time in 80,000 years, and might be as bright as a star in fall 2024.

Comet C/2022 E3 (ZTF) imaged by the Japanese Equuleus cubesat that is orbiting the moon.

Green comet seen from space by Artemis 1 moon mission cubesat (video)

By Tereza Pultarova published

A Japanese cubesat launched aboard NASA's Artemis 1 moon mission took a video of Comet C/2022 E3 (ZTF) earlier this month, about two weeks after the ice ball's closest approach to Earth.

An illustration of the night sky on Feb. 19 showing comet C/2022 A2 (Pan-STARRS) near the constellation Cepheus.

Watch a comet make its 1st and final pass by the sun this weekend

By Robert Lea published

The comet C/2022 A2 (Pan-STARRS) will pass close by the sun on Sunday (Feb. 19), making its first and likely final approach to our star.

A greenish comet streaks through the night sky.

Comet C/2022 A2 (Pan-STARRS) passes close by the sun this weekend

By Stefanie Waldek published

The comet C/2022 A2 (Pan-STARRS) will reach perihelion, or the closest point to the sun in its orbit, on Saturday, Feb. 18. The comet will be visible from Earth at dawn and dusk.

A long-exposure photograph of comet C/2022 E3 (ZTF) taken from Jackson, Wisconsin on Feb. 5, 2023.

Green comet C/2022 E3 (ZTF) may be heading out of the solar system for good

By Robert Lea published

Green comet C/2022 E3 (ZTF) has been predicted to have a period of 50,000 years, but there’s a chance it’s racing out of the solar system.

An image of comet C/2022 E3 (ZTF) taken by Alex Boutté in Scotsdale, Arizona.

Watch green comet near Mars today with free telescope livestream

By Brett Tingley last updated

The Virtual Telescope Project is hosting a free livestream of comet C/2022 E3 (ZTF) near Mars on Saturday (Feb. 11) starting at 2:00 p.m. EST (1900 GMT).

An illustration of the night sky on Feb. 10 showing the green comet C/2022 E3 (ZTF) close to Mars and the Taurus constellation.

See the green comet near Mars in the night sky this week

By Brett Tingley published

Comet C/2022 E3 (ZTF) will be positioned close to Mars in the Taurus constellation from Feb. 9 through Feb. 14, making it easier to locate as it dims in the night sky.

An image of 96P Machholz as it heads toward the sun shows fragments of the comet leading ahead of it.

Massive comet hurtling past the sun is chasing its tail

By Robert Lea published

The massive comet 96P Machholz is currently headed through the inner solar system, and a closer look at this unusual 4-mile-wide space snowball reveals that it's chasing its own tail.

A photo of comet C/2022 E3 (ZTF) taken by Chris Schur in Payson, Arizona.

Watch the green comet pass the bright star Capella on Sunday (Feb. 5)

By Robert Lea published

It's a meeting of the GOATs this weekend when superstar green comet C/2022 E3 meets up with Capella, the Goat Star. Capella should help skywatchers spot C/2022 E3 as it races away from Earth.

British astrophotographer Josh Dury took this image of comet C/2022 E3 above Stonehenge.

Rare green comet's close approach a once-in-50,000 years feast for astrophotographers (photos)

By Tereza Pultarova published

A rare green comet that hasn't been seen since the time of the Neaderthals made its closest approach to Earth on Feb. 1, and astrophotographers all over the world couldn't peel their eyes off it.

Machholz 1 as imaged by NASA's Galaxy Evolution Explorer (GALEX) spacecraft.

Gigantic 'alien' comet spotted heading straight for the sun

By Ben Turner published

Scientists think it may have come from another solar system.

An image of comet C/2022 E3 (ZTF) taken by Miguel Claro in Portugal.

Green comet flaunts its tail in dazzling deep space photo

By Miguel Claro published

A new image from astrophotographer Miguel Claro shows a close-up view of Comet C/2022 E3 (ZTF) on Jan. 22, 2023 immersed in a colorful starfield.

An illustration of the night sky on Feb. 1 showing comet C/2022 E3 (ZTF) at perigee.

Watch a green comet make its first Earth approach in 50,000 years today with this free webcast

By Brett Tingley published

Comet C/2022 E3 (ZTF) is making its closest approach to Earth, and you can watch it pass by without even stepping outside, thanks to a free livestream.

A photograph of comet C/2022 E3 (ZTF) taken by Bob Schiff in Danville, CA.

Green comet C/2022 E3 (ZTF) will be closest to Earth today. Here's how to see it.

By Robert Lea published

C/2022 E3 (ZTF) hasn't been this close to Earth in 50,000 years since the last ice age and prior to the extinction of the Neanderthals.

An image of Comet C/2022 E3 (ZTF) as seen over Italy on Jan. 24, 2023.

The Comet Interceptor probe could visit a stunning object like the green C/2022 E3 (ZTF)

By Meghan Bartels published

Comet C/2022 E3 (ZTF) is tantalizing to spot through a telescope, but what would it look like up close?