You may have seen claims about three comets discovered this year: C/2025 K1 (ATLAS), C/2025 R2 (SWAN), and C/2025 A6 (Lemmon), being visible in the fall skies.
Yeah … about that.
Unless there are significant changes in these comets, two of the three will likely not be visible without a sizable telescope. But the third holds some promise to light up the Halloween night sky
C/2025 K1 (ATLAS) is currently approaching the Sun and is lost in the glare as a result. If it survives perihelion on Wednesday, Oct. 8, the closest point to the Sun in its orbit, it could significantly brighten.
Unfortunately Comet Atlas will remain below the horizon until late November, when it will be about 40 million miles from Earth and likely too dim to see.
Comet C/2025 R2 (SWAN) was discovered on Sept. 11 by amateur astronomer Vladimir Bezugly in images from NASA’s Solar and Heliospheric Observatory (SOHO). It is currently about 50 million miles from Earth but is drawing closer.
Comet SWAN survived perihelion two weeks ago and is just beginning to peek over the western horizon this week. It will continue to rise in the western evening sky night over night and is expected to continue brightening through its closest point to Earth on Oct. 19, a mere 24 million miles away.
However, it is expected to remain too dim to see without a telescope.
C/2025 A6 (Lemmon) was discovered in January by telescopes atop Mount Lemmon in Arizona. It has generated some excitement as observers in the southern hemisphere record the comet steadily brightening bringing the comet to the edge of naked-eye visibility under dark skies. More importantly, the comet has followed the predicted brightening pattern very closely, boosting confidence in forecasts of future brightness.
If this trend continues, Comet Lemmon might be visible to the unaided (suburban) eye, low on the western horizon, in late October as it approaches its Nov. 8 perihelion.
That’s a big if because, as comet discoverer David H. Levy points out, “Comets are like cats: they have tails, and they do precisely what they want.”
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