March 4, 2013 at 7:51 PM ET
Observers in the Southern Hemisphere have been watching Comet PanSTARRS for weeks, but the Northern Hemisphere is due to get its first looks at one of the year's most eagerly anticipated sky extravaganzas this week. And there's good news for northerners: The up-and-down expectations for the cometary show are trending upward again.
"In the Southern Hemisphere we have a few days to enjoy it," Argentine photographer Victor Gabriel Bibe, one of many observers who have been tracking the comet's brightening glow, said in an email.
On Tuesday, PanSTARRS makes its closest approach to Earth. On Thursday or so, it should start becoming visible to Northern Hemisphere observers in the western sky, low to the horizon just after sunset. The best photo ops will come March 12 and 13, when PanSTARRS pairs up with the crescent moon.
The brightness of an astronomical object is measured by magnitude, with lower numbers denoting brighter objects. Magnitude +6 is about the limit for naked-eye observations under prime conditions. Magnitude +2 is equivalent to the brightness of Polaris, the North Star. Early on, astronomers said PanSTARRS could get to magnitude zero, putting it in a league with some of the brightest stars in the sky. More recently, they noted that the comet wasn't brightening as quickly as they originally thought and revised the forecast to around +2. Now, the consensus is that it could get to +1 or brighter — maybe not dazzling, but definitely not bad.
"As long as it continues its behavior for a few days, it looks like the Northern Hemisphere — even us city-dwellers — might get a pretty good view of this thing," said Karl Battams of the Naval Research Laboratory in Washington.
The comet was discovered in June 2011 by the Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS, in Hawaii — which helps explain the genesis of its official name, Comet C/2011 L4 (PanSTARRS). The "C" means that the comet is considered a non-periodic newbie, coming in for the first time from the Oort Cloud on the solar system's edge. The "L4" means it was the fourth comet discovered during the first half of June.
Even though PanSTARRS is still a few days away from Northern Hemisphere visibility, you can take advantage of these tips to maximize your comet-viewing experience:
After PanSTARRS: ISON
PanSTARRS is the first of two comets expected to take the spotlight this year. The other one is Comet ISON, which has the potential to get much, much brighter than PanSTARRS in November. Some experts are hoping it will equal the brightness of the full moon, although Battams says it's way too early to make firm predictions.
To prepare for ISON's arrival, Battams and other researchers are helping NASA organize a comet observing campaign. "We just want to make sure that all the major observatories are aware of this," Battams said.
ISON is expected to pass as close to the sun's surface as 684,000 miles (1.1 million kilometers), which could produce a dramatic brightening of the comet when it swings back out of the inner solar system. It could produce scientific insights as well.
"Sungrazing comets are unique objects that experience the most extreme thermal and gravitation forces our solar system has to offer them," the campaign's Web page says. "However, rarely do we get to see these objects more than a few hours before their demise. Comet ISON offers us the rare opportunity to study a sungrazer in great detail, for an extended period, and place it in the context of other comets."
Got comet pictures? Share them via NBC News' FirstPerson photo upload site and we'll pass them along in a future posting.
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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.