Comet Lemmon

Look up in the sky! 🔭 A special visitor from the frozen edges of our solar system is currently blazing a trail through our cosmic neighborhood. It's called Comet Lemmon (C/2025 A6), and it's putting on a spectacular show for stargazers.

Here’s everything you need to know about this amazing "dirty snowball" from space.

What Is Comet Lemmon?

Comet Lemmon (officially known as C/2025 A6) is a long-period comet. Think of it as a giant ball of ice, dust, and rock, often called a "dirty snowball." These objects spend almost all their time in the freezing cold, far-flung reaches of the solar system, way beyond Pluto.

This particular comet is on a long, elliptical orbit that takes about 1,350 years to complete! This means the last time it swung past the Sun, it was around the 7th century, and it won't be back again until sometime in the 34th century.

Why Is It Called "Lemmon"?

You might be wondering if it's named after the fruit. 🍋 It's not!

The comet gets its name from where it was discovered: the Mount Lemmon Survey in Arizona. This survey uses powerful telescopes to scan the night sky, looking for near-Earth objects like asteroids and comets. It was discovered by this survey on January 3, 2025.

Because this survey is so good at its job, it has found many comets. You might also hear about "Comet Lemmon" C/2012 F6, which put on a great show back in 2013.7 It's just a different comet found by the same program.

Why Is This Comet So Special?

What's exciting about Comet C/2025 A6 is its brightness. Scientists' initial predictions suggested it would be a faint object, only visible with large telescopes.

However, the comet has brightened much more than expected! As it gets closer to the Sun, the Sun's heat causes the ice on the comet's surface to turn directly into gas (a process called sublimation). This process releases a huge cloud of gas and dust, which forms a glowing atmosphere around the comet called a coma. This coma is what we see from Earth.

That Amazing Green Glow

One of the most striking features of Comet Lemmon is its beautiful greenish color. This isn't an Instagram filter—it's real chemistry happening in space.

• The comet's coma contains a molecule called diatomic carbon (C_2).

• When sunlight (specifically, ultraviolet radiation) hits this C_2 gas, it causes the molecules to glow, or fluoresce, with a distinct green light.

• Interestingly, this green glow is usually only seen in the comet's head (the coma). The same UV light that makes the C_2 glow also breaks it apart in a day or two, so it never makes it into the comet's tail, which often looks white or dusty.

How and When to See It

This is the best part: you can see it right now!

Comet Lemmon made its closest pass by Earth on October 21, 2025.It's now heading for its closest point to the Sun (its perihelion) on November 8, 2025.

• Best Time to Look: The best viewing time for observers in the Northern Hemisphere is in the evening, just after sunset.

• Where to Look: Look toward the northwestern sky. The comet is currently moving through the constellation Boötes. A good way to find it is to first locate the Big Dipper, then follow its handle to the bright star Arcturus. The comet will be in that general area.

• What You Need: From a location with very dark skies (away from city lights), you might be able to spot it as a faint, fuzzy smudge with just your naked eye. However, your best bet is to use a good pair of binoculars or a small telescope, which will reveal its glowing coma and maybe even a faint tail.

Don't miss your chance! This comet is a rare visitor, and it's giving us a fantastic opportunity to see a pristine piece of the early solar system with our own eyes. Happy stargazing!