Readers of a certain age may remember the visit of Halley’s Comet back in the 1980s, and younger readers may look forward to its return in 2061. In the meantime, we can all enjoy October’s Orionid meteor shower, as the Earth makes its semi-annual passage through Halley’s debris trail. This month’s show will be a good one, since it will occur on Oct. 21, during new moon, when the sky is dark.
The best time to catch the meteor shower will be an hour or two before dawn on the 21st, when we might see as many as 20 per hour. Orionid meteors will be in our skies from Oct. 2 through Nov. 7, but the best visibility will be before dawn on the 21st. Meteors will appear to streak in a direction away from the constellation Orion but can appear anywhere in the sky. For best viewing, find a location well away from artificial lights, and be sure to allow 15 minutes for your eyes to fully adapt to the dark. Bundle up, too, since October mornings can be chilly.
The evening of Oct. 21 is also a good time to look for Comet C/2025 R2 (SWAN), after sunset in the west. Comet SWAN R2 was found by the SOHO spacecraft which, monitors the sun. The comet was just discovered in September after swinging around the sun and is now outbound to the far reaches of the solar system. Comet SWAN R2 takes about 600 years to complete a full orbit, which extends out to some 145 AU from the Sun, about as far away as the Voyager 2 spacecraft. The Voyager 1 spacecraft is even further – almost 170 AU, while relatively nearby Pluto is only about 40 AU from the sun. Astronomers are still gathering observations to calculate a more precise orbit for Comet SWAN R2.
Comet SWAN R2 will be closest to Earth on Oct. 20. It’s visible with binoculars in early October, and may be visible with the naked eye later in October as it gets closer. The comet will pass through Ophiuchus in early October, heading toward Serpens, and will reach Sagittarius by the 20th. Look low in the southwest as the sky darkens after sunset to find it.
Comet C/2025 A6 (Lemmon) may also be visible later in October, also reaching its closest approach to Earth on Oct. 21 at a distance of 0.6 AU. Comet Lemmon is headed closer to the Sun, with closed approach to the Sun on Nov. 8. It will then swing around to begin its long journey outbound to a distance of 244 AU, returning again in 1,155 years. On the 21st, look for Comet Lemmon near Bootes with binoculars.
Three planets will also put on a show in October. Venus remains a brilliant morning “star” all month – hard to miss in the pre-dawn, eastern sky. Jupiter will be high in the southeast before dawn, rising well before the sun. But Saturn returns to the evening sky, visible in the east-southeast after sunset and will be up all night, setting before dawn. For most of the month, Mercury and Mars are too close to the sun to spot, but Mercury will become visible low in the southwest about 30 minutes after sunset late in October. Mercury will reach its greatest separation from the sun on October 29 before it dives back closer to the sun.
Finally, we hope you enjoy this lovely picture of the conjunction of the Moon and Venus on Sept. 19. In other parts of the world, Venus was fully occulted by the Moon, but here in Indiana, we enjoyed an eye-catching conjunction in the early morning hours. The image was taken by David Sprinkle of the IU Physics Department.
Conjunction of the Moon and Venus. September 19, 2025 by David Sprinkle
The College of Arts