12:30 PM | *Comet ATLAS could become as bright as the moon by the time it approaches the sun in late May*
Paul Dorian
Three weeks ago, amateur astronomer Roman Kulesza of Ontario, Canada, tried to find Comet ATLAS (C/2019 Y4). "It wasn't easy," says Kulesza. "But last night--wow! The comet has really brightened." He took this picture of the emerald-green comet with a 5-inch refracting telescope. Courtesy SpaceWeather.com
Overview
Just a few weeks ago, Comet ATLAS was very difficult to find, but it has surprised many astronomers and has brightened quite dramatically in recent days. The comet is now about as bright now as an 8th or 9th magnitude star which is hundreds of times brighter than astronomers predicted when it was discovered four months ago. There is increasing hope that Comet ATLAS will become quite bright by the time it approaches the sun in late May – perhaps even as bright as the moon.
The orbit of Comet ATLAS courtesy NASA’s JPL; courtesy NASA, spaceweather.com
Discussion
Comet ATLAS was discovered in early 2019 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) and has been given the nickname of ATLAS, but its official name is C/2019 Y4. The comet is what is known as a hyperbolic comet and is in close proximity to the orbit of Mars, but heading closer to the sun. ATLAS is an asteroid impact early warning system being developed by the University of Hawaii and is funded by NASA. It consists of two telescopes, 100 miles apart, which automatically scan the whole sky several times every night looking for moving objects. ATLAS will provide one day's warning for a 30-kiloton "town killer," a week for a 5-megaton "city killer," and three weeks for a 100-megaton "county killer". So far, ATLAS has discovered 427 near-earth asteroids and as many as 37 comets included the one now being referred to as Comet ATLAS.
The comet is hundreds of times brighter than originally predicted at the time of discovery and there is growing hope that it will become quite bright when it approaches the sun during the latter part of the month of May. Brightness estimates for Comet ATLAS range from magnitude +1 to -10 which is somewhere between a 1st magnitude star and the waxing crescent moon.
The photograph (top) of Comet ATLAS was taken last night in Ontario, Canada using a 5-inch refracting telescope. In the image, the comet is about 1 degree wide and this information combined with the estimated distance of 1.1 AU allows for an estimate of the physical size of the comet’s green atmosphere: ~300,000 km or more than twice as wide as Jupiter. In other words, it’s a pretty big target and it’s getting bigger as it approaches. Amateur astronomers can find Comet ATLAS in Ursa Major. By late May, Comet ATLAS will be only about 0.25 AU away from the sun and getting closer (one AU (astronomical unit) is equivalent to the distance between the Earth and the Sun).
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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