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It was early January 2025 when a faint spot of light was spotted at Mount Lemmon Observatory in Arizona. Follow-ups revealed that the object was a visiting comet from the outer edge of the solar system, and was named Comet Lemmon (C/2025 A6). Its “period” – the time it takes to complete its long orbit around the Sun – is about 1,350 years.
Initially, the comet was so faint that it could only be seen with specialized equipment. But it rapidly grew brighter as the months passed, and by fall, it was bright enough to be seen with binoculars. It will now become brighter, as it approaches Earth and the Sun, and may become visible to the naked eye.
according to NASAThe culprit will be lemon Closest to Earth around October 21, 2025It passes at a distance of about 0.60 astronomical units, or au (1au is the distance between the Earth and the Sun). The comet is then expected to reach perihelion – the point at which it is closest to the sun – on November 8. By the time the comet reaches perihelion, it will likely have reached maximum brightness, and may be visible to the naked eye if conditions are favorable in the dark sky.
The comet’s tail will also be at its longest extension around perihelion. Tails form on comets when solar radiation heats the frozen ice and gases in the comet’s nucleus, causing them to sublimate — turning them from a solid into a gas — and then the radiation causes some of that material to spew out of the comet in a clear line. The stronger the radiation, the greater the magnitude of this effect, and so the tails of comets grow as they approach the stars and shrink again as they move away.
Comet Lemon is green in colour. This is caused by the cloud of gas surrounding the comet’s nucleus, known as its ‘coma’, where the color is created by diatomic carbon (molecules made up of two carbon atoms) interacting with sunlight.
How to view a comet
As of early October, Comet Lemmon can be found just below the handle in Ursa Major (or Plough, as it’s known in the UK), which forms part of the constellation Ursa Major. If you look into the northern sky, you will be able to trace its path. In the Northern Hemisphere, it is It is expected To appear in the northwestern to western skies after sunset from mid-October onward. It will be low above the horizon, and is expected to emit a faint glow in the twilight just after sunset.
The best time to observe the comet is about a week before and after its closest approach. In November, the comet will cross the celestial equator and become visible from the southern hemisphere.
Binoculars or small telescopes are best for observing it, but if you choose a location with little light pollution, you may be able to see it with the naked eye. If you look at the sky just after sunset when it’s a little bright, you may be able to see it. If you’re having trouble finding the comet, use the star map app on your smartphone or planetarium software to help you locate it.
