See rare comet before it vanishes for 1,300 years
Sarah Knapton
21 October 2025 at 6:20 pm
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A rare green Hallowe'en comet will be visible in the night sky over the next few weeks before it vanishes for 1,300 years.
Comet Lemmon was discovered in January and has been making its way towards Earth ever since.
It reaches its closest approach on the night of Oct 21, at a distance of 56 million miles from Earth, before sweeping on towards the Sun and then moving back out into the Solar System.
The comet is so bright that it could be visible to the naked eye in dark skies, although astronomers recommend binoculars or a telescope to be certain of catching the phenomenon.
It will appear as a fairly bright, fuzzy green glowing object in the sky with a barely perceptible short tail.
Dr Robert Massey, deputy executive director of the Royal Astronomical Society said: "Comet Lemmon is pretty much at its best visibility right now.
"The best place to look is in the evening sky. As the sky darkens the comet will first of all be moving, over a matter of days, past the bright star Arcturus, and then further round towards the south-west, beneath the stars of the Summer Triangle."
Comet Lemmon is best seen from the Northern Hemisphere and has been moving underneath the Big Dipper, or Ursa Major. It was named after Arizona's Mount Lemmon where it was detected.
It is best to look for the brightest star in the night sky - Arcturus in the constellation Boötes - and the comet will be moving slowly nearby. Boötes has the shape of a kite, and Arcturus is at the point where the tail would attach.
It will continue to brighten as it gets closer to the Sun, and will reach peak illumination around Hallowe'en when it will pass in front of the stars of the constellation Ophiuchus.
A second comet, known as Swan, was discovered in September and can be spotted in the predawn sky, when it will appear on the eastern horizon. It is harder to see and will require binoculars or a telescope.
It is estimated that it takes as many as 20,000 years for Comet Swan to orbit the Sun.
The appearance of the two comets coincides with the annual Orionid meteor shower, which is visible until Nov 7 and peaks around Oct 21.
Meteor showers occur when the Earth passes through a clump of debris in space - often comet tails - as our planet moves along its orbit around the Sun.
This particular one comes from the dust stream of Halley's Comet, which swings by the Earth only once every 75-76 years and is next due to appear in 2061.
When the meteors enter our atmosphere at high speed, the friction as they pass through causes the air around them to heat up dramatically, resulting in a characteristic brief bright streak of light or "shooting star".
The shooting stars will appear to emanate from a point slightly above and to the left of the bright red star Betelgeuse, which forms one of the shoulders of Orion.
For observers in the UK, the constellation will rise towards the South East and the best time to watch will be at dawn on both Oct 21 and Oct 22. This is when it will be highest in the sky and activity is predicted to peak.
During especially active periods, as many as 75 shooting stars from this comet can be seen per hour, but more typical years have 10-20 per hour.
Dr Mark Norris, senior lecturer in astrophysics at the University of Lancashire, said: "A meteor shower happens when Earth passes through debris left by a comet or asteroid as it moves through the solar system.
"The small pieces of rock and ice, usually about the size of a grain of sand, hit our atmosphere at speeds above 30 km/s. Friction heats the meteors up, causing them to light up and glow brightly enough for us to see.
"The latest meteor shower is called the Orionids - named after the constellation of Orion that it appears to radiate from.
"The shooting stars of this meteor shower originated as material ejected from the famous Halley's Comet. Halley's Comet returns to the inner solar system every 76 years, and last visited us in 1986."