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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 

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NASA's New Horizons spacecraft flew by the Kuiper Belt object Ultima Thule on Jan. 1, 2019 as shown in this artist's illustration. It's the furthest planetary flyby in history.

Asteroids, Comets, Black Holes — Oh My! The Year 2019 in Astronomy

By Nola Taylor Redd

A black hole was photographed, the farthest flyby was completed, and a beloved rover was proclaimed dead. Follow us through the highs and lows of 2019 space science.

Artist's illustration of a black hole.

The Decade in Astronomy: These Space Discoveries Shaped the 2010s

By Sarah Wells

As the 2010s come to a close, it's time to revisit how some of the biggest space science stories shaped the decade.

Comet 2I/Borisov is the first interstellar comet ever observed by humans. These two images, taken by NASA's Hubble Space Telescope, capture the comet appearing near a background galaxy on Nov. 16 (left) and after the object's closest approach to the sun, on Dec. 9 (right).

Interstellar Comet Borisov Shines in Incredible New Hubble Photos

By Chelsea Gohd

Two new "ghostly" images catch the first observed interstellar comet whizzing by the sun and in front of a distant, spiral galaxy on the object's way back out of our solar system.

A depiction of the path of interstellar Comet Borisov, which makes its closest approach to the sun on Dec. 8, 2019. It may be visible in small telescopes.

Interstellar Comet Borisov Makes Closest Approach to the Sun

By Samantha Mathewson

It may be visible in small telescopes.

Gennady Borisov, a skywatcher who discovered the first interstellar comet.

How to Find an Interstellar Comet: A Q&A with Discoverer Gennady Borisov

By Meghan Bartels

Gennady Borisov stunned the astronomical community earlier this year when he announced that he had spotted an interstellar comet dashing through our solar system.

NASA's Transiting Exoplanet Survey Satellite caught Comet 46P/Wirtanen emitted a blast of dust, ice and gases beginning on Sept. 26, 2018.

NASA Planet-Hunting Telescope Spots Massive Burp from a Comet

By Meghan Bartels

Scientists have caught their best-ever look at a comet belching out ice, dust and gas — and the observations came courtesy of a mission designed to hunt for alien worlds.

Left: A new image of the interstellar Comet 2l/Borisov. Right: A composite image of the comet with a photo of the Earth to show scale.

Interstellar Comet Borisov Shines in New Photo

By Mike Wall

A new photo shows the solar system's second confirmed interstellar visitor in an impressive new light.

Skywatcher Jim Gamble of El Paso, Texas created this composite image of the 2010 Leonid meteor shower display using an allsky camera.

The Leonid Meteor Shower Explained in 10 Facts

By Robert Roy Britt

NASA's Hubble Space Telescope captured this view of the interstellar object Comet 2I/Borisov on Oct. 12, 2019.

Hubble Space Telescope Spots Interstellar Comet Borisov (Video)

By Elizabeth Howell

NASA's venerable Hubble Space Telescope turned its eyes to interstellar visitor Comet 2I/Borisov and caught a surprise: The interloper looks a lot like comets from our own solar system.

The first color image of the comet C/2019 Q4 (Borisov), which astronomers believe to be the first known interstellar comet ever identified, was captured by the Gemini North telescope at Hawaii's Mauna Kea. Gemini North acquired four 60-second exposures in two color bands (red and green). The blue and red lines are background stars moving in the background.

Interstellar Comet Borisov Looks Pretty Normal, New Observations Suggest

By Meghan Bartels

Observations of the interstellar Comet Borisov have been flooding in for six weeks, and the more astronomers duplicate one another's work, the more confident they are in their analysis of the object.

An artist's illustration of the centaur Chiron, which may have rings or orbiting dust structures.

Centaurs Rising: NASA Eyes Missions to Weird Asteroid-Comet Hybrids

By Mike Wall

The Centaurs may get their first-ever close-up soon.

The first color image of the comet 2I/Borisov, the first known interstellar comet ever identified, was captured by the Gemini North telescope at Hawaii's Mauna Kea. Gemini North acquired four 60-second exposures in two color bands (red and green). The blue and red lines are background stars moving in the background.

Gas Molecule Identified on Interstellar Comet for 1st Time

By Mike Wall

For the first time ever, astronomers have taken the compositional measure of an interstellar interloper.

An image of a protoplanetary disk and black gaps marking where planets are formed, as captured by the Atacama Large Millimeter/submillimeter Array telescope in Chile.

'Oumuamua and Borisov Are Just the Beginning of an Interstellar Object Bonanza

By Meghan Bartels

Astronomers are only now getting the hang of spotting interstellar objects, space debris that fled another solar system to swing through ours.

An image of 2I/Borisov captured on Sept. 24, 2019, in Italy.

It's Official! Suspected Interstellar Comet Borisov Is from Beyond Our Solar System

By Meghan Bartels

A comet spotted at the end of August is officially an interstellar object, according to the International Astronomical Union.

Small, icy bodies travel through a gateway region of space where they turn into comets.

Newfound Cosmic 'Gateway' Funnels Small, Icy Objects to the Inner Solar System

By Yasemin Saplakoglu

Beginning as small, icy bodies on the outskirts of the solar system, comets turn into spectacular streaks of light when they pass through a "gateway" near Jupiter.

The first color image of the comet C/2019 Q4 (Borisov), which astronomers believe was born in another solar system, was captured by the Gemini North telescope at Hawaii's Mauna Kea. Gemini North acquired four 60-second exposures in two color bands (red and green). The blue and red lines are stars moving in the background.

We Could Chase Down Interstellar Comet Borisov by 2045

By Mike Wall

We could get an up-close look at our solar system's latest interstellar interloper a quarter century from now if we so desired, a new study suggests.

Observations of what scientists believe to be the first interstellar comet ever identified.

First Glimpses of Interstellar Comet Suggest It's Not So Different

By Meghan Bartels

Astronomers are rushing to study what appears to be the first known interstellar comet — and in some of the very earliest observations, it looks oddly familiar.

A 30-second exposure of the newly identified comet captured by the Canada-France-Hawaii Telescope in early September 2019.

Interstellar Comet: Here's Why It's Got Scientists So Pumped Up

By Meghan Bartels

Karen Meech wouldn't credit Comet C/2019 Q4 with good timing. But when faced with a chance to study the first known interstellar comet, by golly you take it.

The first color image of the comet C/2019 Q4 (Borisov), which astronomers believe to be the first known interstellar comet ever identified, was captured by the Gemini North telescope at Hawaii's Mauna Kea. Gemini North acquired four 60-second exposures in two color bands (red and green). The blue and red lines are background stars moving in the background.

1st Color Photo of Interstellar Comet Reveals Its Fuzzy Tail

By Elizabeth Howell

Astronomers took the first multicolor images of a potentially interstellar comet, and it looks spectacular.

A depiction of the path of Comet C/2019 Q4, which may be the second interstellar object detected to date.

This Comet Might Be from Interstellar Space. Here's How We Could Find Out.

By Meghan Bartels

At first, it was just another bright, fuzzy speck in the sky. But it may turn out to be something much more exciting: the second known object to hurtle through our solar system after leaving another.