Soon after its discovery last year, comet C/2019 Y4 (Atlas) gained a lot of attention, possibly being a fragment of Great Comet C/1844 Y1. Its orbit will bring it closer to the Sun than planet Mercury (about 38 million km) and it has the potential to become significantly bright.
Comet ATLAS (C/2019 Y4) is coming … and the Sun is waiting. In late May, the dirty snowball will dip inside the orbit of Mercury, passing only 0.25 AU from the Sun. No one knows what will happen when the comet’s icy core is exposed to solar heat at point blank range.
“ATLAS is a bit of a wildcard, and there’s a spectrum of possibilities as it nears the Sun,” says Karl Battams of the Naval Research Lab in Washington DC. “At one extreme, it could simply crumble away in the coming weeks, and at the other extreme it could brighten up tremendously. It has an unusually small perihelion distance inside of Mercury’s orbit, which bodes well for getting those frozen gases fizzing furiously.”
Currently Comet ATLAS is beyond the orbit of Mars. Even at that great distance, it is already brightening, shooting up 100-fold since the beginning of February. Currently, it looks like a fuzzy star of 11th magnitude in the Big Dipper–an easy target for backyard telescopes. By the end of May, the comet could be as bright as a 1st magnitude star. Astronomers will be struggling to see it, however, through the glare of the approaching Sun.
“All is not lost!” says Battams. “We have a number of space telescopes designed to view objects very close to the Sun. For instance, the Heliospheric Imager on NASA’s STEREO spacecraft will get a great view of ATLAS from mid-May through early June. The camera is very sensitive, so we might be able to observe ATLAS’s tail interacting with the solar wind and outflows.”
For Amateur astronomers
Can’t wait for May? Amateur astronomers with mid-sized backyard telescopes can observe Comet ATLAS now. Monitoring is encouraged. Outbursts are possible in the weeks ahead as new veins of volatile material are exposed by intensifying sunlight. Point your optics using this ephemeris from JPL and submit your images here.