A bright new comet from the solar system could put on a show in the October night sky as it flies past Earth.
Comet C/2025 R2 (SWAN) was discovered on September 10 by Ukrainian amateur astronomer Vladimir Bezugly. It has brightened significantly since then, raising hopes that it could become a naked-eye comet when it comes closest to Earth later this month, on October 21.
As it gets closer to the sun, the heat from our star causes the frozen material in the comet’s core to change from a solid state directly to a gaseous state, in a process called sublimation. The resulting gaseous shell is then blown away by the solar wind, creating a long tail of dust and gas that reflects sunlight, creating a cosmic spectacle that might, if we’re lucky, be visible to the naked eye from Earth.
C/2025 R2 (SWAN) came closest to the sun – a point known as perihelion – on September 12, when it passed just under 47 million kilometers from the sun, or about half the average orbital distance of Earth.
Magnitude
Magnitude is the scale used to measure the apparent brightness of objects in the night sky. The lower the number, the brighter the object! For context, the brightest stars are around Mag +1, while a full moon is at -13 and the sun is at -27.
Recent observations collected by the Comet Observing Database (COBS) managed by the Crni Vrh Observatory in Slovenia placed the brightness of C/2025 R2 (SWAN) at magnitude 5.6, meaning it could already be visible as a very faint object to the naked eye under a perfectly dark sky. As a reminder, the human eye is capable of detecting objects in the night sky with a magnitude less than +6 under ideal conditions. (The brighter an object, the lower its magnitude.) The comet will be much easier to spot with a pair of binoculars or a telescope.
How to Find Comet C/2025 R2 (SWAN) in the October Night Sky
Comet C/2025 R2 (SWAN) can be found in the evening sky throughout October and is best spotted in the hours after sunset, before sinking low on the south-southwest horizon. On October 16, the comet will be positioned about 5 degrees to the upper left of the star Xi Serpentis, in the eastern part of the Serpens constellation. A stargazing app on your mobile device can help you locate the comet if you are unfamiliar with these stars.
The following week will see the C/2025 R2 (SWAN) pass above the famous asterism “teapot” in the Sagittarius constellation to cross the stars of the Scutum constellation.
By the end of the month, the solar system’s wandering body will be visible above the southern horizon, between the bright stars Sadalmelik and Sadalsuud in the constellation Aquarius, with the half-lit moon below.
Astronomers hoping to spot C/2025 R2 (SWAN) should read our summaries of best binoculars And telescopes for observing the night skywhile those seeking to imagine the wanderer should read our guide to imaging a solar system comet with a DSLR camera.
Editor’s note: If you capture an image of Comet C/2025 R2 (SWAN) and would like to share it with Space.com readers, please send your photo(s), comments, and your name and location to spacephotos@space.com.
