Grab your binoculars or a telescope because there’s a "new" comet in town, and it won’t be around for long. In fact, once Comet Catalina leaves our solar system, it won’t be coming back again.
Comet Catalina, a dual-tailed comet with a diameter of about 12 miles, will be traveling across the skies over the next few weeks before it disappears from view. Also referred to as C/2013 US10, Comet Catalina has been visible since last November when it made its closest approach to the sun on Nov. 15, just 76.5 million miles from the sun. According to SPACE.com, it will be closest to Earth on Jan. 17, when it will be a mere 67.4 million miles away.
To see Comet Catalina this month, astronomers believe binoculars or a telescope will be necessary as the comet is expected to maintain a magnitude of 6 before fading after its closest approach on the Jan. 17. While 6th magnitude objects are technically visible (but very faint and easily obstructed by moonlight and light pollution), you’ll need tools to get a good look at this visiting "dirty snowball."
While the comet can be seen this month in the east just before dawn, Jan. 18 might be the best morning for viewing. To find Comet Catalina, skywatchers should first look for the Big Dipper and then find Mizar (of the Mizar and Alcor double-star). Comet Catalina will appear a few degrees left of Mizar, which is the second to last star in the handle of the Big Dipper. Comet Catalina should appear to have a greenish tinge.
Comet Catalina is named for how it was discovered. On Oct. 31, 2013, Catalina Sky Survey’s Schmidt-Cassegrain telescope, located in the Catalina Mountains outside of Tucson, Arizona, detected the object. Catalina Sky Survey, a NASA-funded program, is charged with finding near-Earth objects (NEOs) which are asteroids and comets in Earth’s part of the solar system. Comet Catalina was originally thought to be an asteroid, but after observing its behavior, scientists determined its true identity. A similar misidentification occurred with 2015’s Halloween Asteroid which was later revealed to be a dead comet.
Like all comets, Comet Catalina formed around 4.6 billion years ago in a very young solar system. However, this is likely the first and last time that Comet Catalina will pass through the inner solar system. It has a hyperbolic orbit, meaning it has enough velocity to escape the sun’s gravitational pull and continue on its way out into interstellar space, presumably never to return to the solar system again.
Scientist believe that Comet Catalina originated in the Oort Cloud at the distant reaches of the solar system and was knocked out of orbit and sent on its current path by gravitational pulls from other objects. Scientists suggest that comets originate from either the Oort Cloud or the Kuiper Belt (where Pluto resides), and behave in certain ways based on their origins. Oort Cloud natives are suspected of being long-period comets with orbits of 200 or more years, while Kuiper Belt comets are thought by some scientists to be short-period comets.
Aside from its one-time-only appearance to our corner of the universe, an additional feature of Comet Catalina that makes it even more interesting is the way its dual tails appear to be traveling in opposing directions. Some comets have two tails, one made of gas and one made of dust. What causes this comet to appear in its unique fashion is the effect the sun has on the comet and our unique perspective in viewing it. Put simply, the sun affects the two tails differently. The gas tail becomes ionized and blows in the solar winds. At the same time, the dust tail is pushed back from the comet in a trailing fashion. From where we're standing, the tails seem to shoot out in different directions thereby making the glowing green Comet Catalina that much more special.