Comet Catalina

October 31, 2013 – the Catalina Sky Survey in Arizona discovered C/2013 US10, known as the Catalina Comet. Astronomers thought they’d identified a new asteroid – not so fast. Catalina is officially a comet, an Oort cloud stray with a 4 – 20 kilometer nucleus, 800,000 kilometer tail, traveling through space at 166,000 km/h. Best of all – by late November, early December we should be able to view it with the naked eye.

Science pegs Catalina as a “one off”, a rogue comet destined to pass our solar system once, then find itself “ejected” to the cosmos, never to be seen again. From the end of November, through December look for Catalina along the east-southeast horizon just before dawn. Finding Venus in the direction of sunrise will be helpful. As of today the wait is 3 years for 46P, our next visible to the naked eye comet. Why wait for Comet 46P in 2018 – tickets for Catalina are on sale now.

November 23, 2015, 30 to 45 minutes before sunrise, local time. 'Local time' means the time on your clock, in all timezones.

View larger. | Comet C/2013 US10 (Catalina) on October 1, 2015 by José J. Chambó (

View larger. | Comet C/2013 US10 (Catalina) on October 1, 2015 by José J. Chambó (

From earthsky –

November 15, 2015. Comet Catalina is at perihelion or closest to the sun. It will not become as close to the sun as some comets do. At closest approach to our star, the comet will be moving between the orbits of planets Earth and Venus. Its perihelion distance is 0.82 AU from the sun (1 AU = 1 Earth-sun distance). Comet Catalina is traveling at a speed of 103,000 miles per hour (166,000 km/h) relative to the sun at perihelion.

November 23 to 30,2015. Comet Catalina starts to become visible for Northern Hemisphere observers.

December 7,2015. Sky show! Comet visible close to Venus and the waning moon. Hopefully, the comet will be visible to the eye by this time, but you never know. Either way … think photo opportunity.

December 31,2015. Comet approaching the apparent position of the star Arcturus on our sky’s dome. Another good photo opportunity.

January 1,2016. Comet Catalina will be passing very close to star Arcturus. An excellent reference to finding the comet in the sky!

January 17,2016. Comet Catalina will pass some 110 million kilometers (68 million miles) from Earth. That’s very, very far from Earth – hundreds of times farther than the moon’s distance. So there is no danger of a collision. That said, let’s talk about the size of the comet’s nucleus or core. Some estimates indicate the nucleus of Comet Catalina ranges between 4 and 20 kilometers in diameter.


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