You'll be hearing a lot about Comet PanSTARRS, also known as C/2011 L4, now that it's become visible in the Northern Hemisphere — but if you're not properly prepared, the experience can be underwhelming. You have to know where and when to look, and with what. Fortunately, there are lots of resources to draw upon.
First, some quick facts: Comet PanSTARRS is thought to come from the Oort Cloud on the solar system's edge, and is making its first round through the inner solar system. It was discovered in 2011 by the Pan-STARRS Telescope team, but it didn't attract wide attention until last year, when astronomers noticed a brightening trend that promised to produce a sight visible to the naked eye. The comet is expected to shine brighter than the stars of the Big Dipper (magnitude +2 to +1) over the weekend.
The challenge is that during this time of peak brightness, the comet will be visible quite low near the western horizon, just after sunset.
"Look too early and the sky will be too bright," NASA postdoctoral fellow Rachel Stevenson said in a PanSTARRS preview provided by the Jet Propulsion Laboratory. "Look too late, the comet will be too low and obstructed by the horizon. This comet has a relatively small window."
The farther north you are, the closer to the horizon you'll have to look. Those aren't exactly ideal conditions, especially if you have an obstructed view to the west, or if there are clouds on the horizon, or if there's significant haze in the air. The best viewing spots should be at higher elevations, far from haze and the glare of city lights, where the skies can get as dark as possible as soon as possible after sunset.
Depending on your location in the Northern Hemisphere, you may not be able to get a good look at the comet until next week. But even if you miss seeing it on Thursday or Friday, it's worth checking out a variety of spots over the next few days to get ready for the peak experience on March 12 and 13. That's when Comet PanSTARRS is due to make a pretty appearance close to the crescent moon.
Although the comet has become visible to the naked eye, you'll want to pull out the binoculars to make out the comet's tail. You might notice two elements to the tail, pointing in slightly different directions: One element is made up of glowing ionized gas, while the other is made up of dust that reflects the light of the sun.
PanSTARRS is due to make its closest approach to the sun on Sunday, coming within 28 million miles (45 million kilometers). On each evening after that, the comet's position will be slightly more elevated from the horizon, and shift slightly to the north. It'll also become dimmer. By mid-April, the comet will no longer be visible to the naked eye, even under the best circumstances.
When PanSTARRS fades from the spotlight, don't put your binoculars back in the attic: Another starry messenger from the outer solar system, known as Comet ISON, is due to make its appearance in November. Some skywatchers have dubbed ISON the "Comet of the Century" because the most optimistic projections suggest it could shine as brightly as the full moon. It's way too early to make firm predictions, but it's a good bet that the comet-watching skills you develop while looking for PanSTARRS will come in handy when it's ISON's turn.
Got comet pictures? Share them via NBC News' FirstPerson photo upload site and we'll pass them along in a future posting.
Now for those resources:
- PanSTARRS updates from Sky & Telescope
- Astronomy Magazine's PanSTARRS guide
- All you need to know from EarthSky
- Video: When can you see the comet?
- Space.com's PanSTARRS viewing guide
- Discovery News' comet viewing guide
- Check with your local astronomy club
- Comet gallery at SpaceWeather.com
- Guide to photographing comets
- More tips from EyesOnCometISON.com
- Comet reports from "Waiting for ISON"
- Geek out at Comets-ML and CometObs
- Flash interactive: Inside a comet
- More about comets from Cosmic Log
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.