Comet C/2025 F2 (SWAN) captured from California (Credit: Dan Bartlett/ NASA.gov/ Public Domain)

A glowing green comet is captivating skywatchers across the Northern Hemisphere. Comet C/2025 F2 (SWAN) was first spotted by amateur astronomer Michael Mattiazzo on March 29, 2025. He discovered it while looking through images from the Solar Wind Anisotropies camera aboard NASA's Solar Heliospheric Observatory. Since then, the comet has been seen multiple times with the help of telescopes.

Comet SWAN is expected to make its closest approach to the Sun on May 1, 2025, passing just 31 million miles (49.9 million km) away. That is closer than Mercury, the innermost planet to the Sun. It will also reach its closest point to Earth on the same day, coming within 89.5 million miles (144 million km).

How to spot Comet SWAN

Thanks to its position in the northern skies, the next two weeks will offer the best viewing opportunities from the Northern Hemisphere. Comet SWAN will be visible in the early morning sky through April 24, 2025. Stargazers should seek out an unobstructed view and look northeast at least 70 minutes before sunrise.

Starting April 25, the comet will shift to the west-northwest horizon and be visible shortly after sunset. Experts suggest waiting at least 70 minutes after sunset for the best view.

Chart showing the location of Comet SWAN in April 2025 (Credit: NASA.gov/ Public Domain)

The comet will fade from the Northern Hemisphere skies around May 8. Southern Hemisphere viewers will join the party around May 4. They will enjoy views of the comet through the rest of May.

Unless the comet brightens significantly, you will need binoculars or a small telescope to see it. While it appears green in photos, it will likely look like a fuzzy white light to the naked eye. The green glow in images comes from gas around the comet that glows when hit by sunlight. But it is very faint, so our eyes usually cannot see it. Cameras, however, can pick it up, making the comet appear even striking in pictures!

What are comets?

Comets are icy objects that orbit the Sun. They are made of dust, rock, and frozen gases. When a comet nears the Sun, the heat causes its ice to vaporize, forming a glowing head called a coma and one or more tails.

Dusty comets produce more dust, forming a bright, curved tail that reflects sunlight.
Gas-rich comets release more gas, forming a straight, blue or green tail that points away from the Sun due to the solar wind. Comet SWAN's distinct green color suggests it is primarily made of gas.

Comets come from distant regions of the Solar System, such as the Kuiper Belt and the Oort Cloud. They travel in long, oval-shaped orbits and take hundreds or even millions of years to complete their journey around the Sun. For instance, Comet SWAN will not return for another 1.4 million years, making this a truly once-in-a-lifetime event!

Resources: Space.com, Smithsonianmag.com, Skyandtelescope.com