A recently discovered comet – although not visible to the eye alone – is becoming bright enough to view with small telescopes and binoculars. Comet C/2017 O1 (ASASSN1) is a long-period comet – presumably from the Oort Comet Cloud surrounding our solar system – first detected on July 19, 2017 from the All Sky Automated Survey for Supernovae from Cerro Tololo, Chile. In fact, it was the first comet detected by this survey. The comet had an outburst shortly after discovery and has been getting brighter, and – if you have a small telescope or good binoculars – you can start watching it now. During most of September, Comet C/2017 O1 is in front of the constellation of Taurus and shows a brightness or magnitude of 9.5.
An orbit analysis of this celestial visitor indicates it will be at perihelion, or closest to the sun, on October 14, 2017. It’ll be closest to Earth on October 18, passing distantly at about 67 million miles (108 million km) from our planet.
Although comets are unpredictable, recent observations show that C2017 O1 has brightened. It is not expected to become visible to the unaided eye, but the comet may reach a magnitude of around 8. If so, it’ll be well within reach of binoculars and small telescopes.
Binoculars should reveal it as a small fuzzy patch of light in the sky. Some observers may see a hint of green color in the comet, which is caused by gases like diatomic carbon.
Bottom line: Charts that can help you find long-period comet C/2017 O1 (ASASSN1).
Eddie Irizarry of the Sociedad de Astronomía del Caribe (Astronomical Society of the Caribbean) has been a NASA Solar System Ambassador since 2004. He loves public outreach and has published multiple astronomy articles for EarthSky, as well as for newspapers in Puerto Rico. He has also offered dozens of conferences related to asteroids and comets at the Arecibo Observatory.