Halloween is upon us and the 2025 spooky season is abuzz with speak of three cosmic guests — Comet Lemmon, Comet SWAN and the interstellar traveler 3I ATLAS — mentioned to be haunting the night time sky. But with regards to stargazing, one in every of these ghostly wanderers is extra trick than deal with!
Comets are composed of primordial matter left over from the creation of our photo voltaic system — and others — which turn into lively as they method the solar, as the rise in warmth radiation causes icy supplies to rework right into a gaseous shell across the nucleus. That shell is then blown away by the photo voltaic wind — the relentless stream of charged particles issuing forth from our star — making a tail that displays daylight..
A Cometary trick, or a stargazing treat?
Comet Lemmon — A Halloween treat
Comet C/2025 A6 Lemmon has brightened dramatically over the past month. It currently boasts a magnitude — or apparent brightness — of around +4.2, according to the Comet Observation Database, which might render it seen as a hazy patch of sunshine from a darkish sky location.
Whilst it is attainable to view Comet Lemmon with the bare eye, a pair of 10X50 binoculars or perhaps a modest yard telescope will assist reveal the daylight reflecting from the icy wanderer’s central coma and sumptuous, elongated tail.
Comet Lemmon will probably be positioned low on the western horizon, embedded among the many stars of the constellation Ophiuchus in the hours following sunset on Oct. 31. After locating the constellation, use your smartphone astronomy app to pinpoint the stars Kappa Ophiuchi and Epsilon Ophiuchi. Comet Lemmon will shine roughly halfway between these two stellar giants, near the magnitude +3.8 star Marfik.
Interstellar Comet 3I/ATLAS — a skywatching trick
On Halloween night, 3I/ATLAS will be positioned close to the rocky planet Venus in the constellation Virgo, which will rise highest in the hour preceding dawn on Nov. 1, bathed in the glow of the rising sun. The cosmic interloper is expected to emerge from behind the glare of our parent star by early December, according to NASA, although its obvious brightness will possible have dipped considerably by then, because it passes ever farther from the solar’s radiation, on an escape trajectory from our photo voltaic system.
Comet C/2025 R2 (SWAN) — A telescopic problem
SWAN’s brightness is currently on the decline following its close brush with Earth on Oct. 21. Its estimated magnitude of 7.2 renders it too dim to be spotted with the naked eye, though a pair of 10X50 binoculars or a small backyard telescope will help reveal the hazy reflected light centered around its icy nucleus shining against the blackness of space. However, the light of the 76%-lit moon will present an added challenge to spotting the comet on the night of Oct. 31
Look to the southern horizon in the hours following sunset on Halloween to find the moon glowing among the stars of the constellation Aquarius. Next, locate the bright magnitude 3 stars Sadalmelik and Sadalsuud, which form the shoulders of the “water bearer” depicted in the stellar formation. Comet SWAN can be found in the patch of sky two-thirds of the way from Sadalsuud to Sadalmelik.
Comet SWAN is now rushing headlong away from the sun on a highly eccentric orbit that takes it well beyond the orbit of icy Neptune, and it isn’t expected to return for another 1,400 years after it disappears from Earth’s skies, so catch it while you can!
Stargazers interested in creating a lasting view of the transient visitors to Earth’s sky should check out our guide to observing and photographing comets, along with our roundups of the best cameras and lenses for astrophotography in 2025.
Editor’s Note: If you would like to share your cometary astrophotography with Space.com’s readers, then please send your photo(s), comments, name and the location of your shoot to spacephotos@space.com.