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The Planetary Society Blog
By Emily Lakdawalla
Got binoculars? Spot a comet near Saturn tonight
Feb. 23, 2009 | 16:32 PST | Feb. 24 00:32 UTC
The greenish comet Lulin, more formally known as C/2007 N3, has been approaching Earth for some time and will, tomorrow, be at its brightest, as it'll reach its closest approach to us. But it might be easiest to spot tonight, as it will be passing especially close to Saturn. (Close, that is, in the flattened geometry of our sky; it's actually much, much closer to us than it is to Saturn.) Although Lulin technically a naked-eye object, if you're graced with particularly dark skies, it's more reasonably a binocular target for most people. The good news is that even if you live in a fairly light-polluted location, binoculars should still reveal it. (Or so I'm told.) | Spotting comet LulinComet Lulin climbs higher in the east-southeast each night this week. Spot bright Saturn and Regulus, and use them to zero in on the comet's position for your date.
(The comet's positions marked are for the evening of the date indicated in the time zones of the Americas. The orientation of the view with respect to the horizon is for North America.)
Credit: Sky & Telescope |
Lulin has a special significance for us at The Planetary Society, because it was discovered by one of our recent Gene Shoemaker NEO Grant recipients: Quanzhi Ye, the now-19-year-old principal investigator of the Lulin Sky Survey.Quanzhi Ye2007 winner of a Shoemaker NEO grant. |
Astrophotographers of all stripes have been capturing spectacular images of Lulin in recent days. Spaceweather.com is always a good place to look for lots of variety; I browsed their Lulin gallery and picked out this one as my favorite so far.Comet C/2007 N3, a.k.a. comet LulinPhilip Jones captured this stunning photo of comet Lulin at the Central Texas Astronomical Society observatory grounds in Clifton, Texas on February 22, 2009. More of his photos are available here. Credit: Philip Jones |
The comet is both spectacular and strange because it has a prominent antitail. The word "antitail" is one I must admit I was not familiar with, but it was pointed out to me by reader Borja Tosar who also provided me with the following diagram: What is an antitail?This diagram explains how some comets, like C/2007 N3 (known as comet Lulin), can appear to have an "antitail." Most comets have two different tails: an ion tail and a dust tail. The ion tail is caused by the comet's interaction with the solar wind and points more or less directly away from the Sun. The dust tail is caused by the interaction of dust particles ejected by the comet with sunlight: light pressure pushes the dust particles away from the comet, which means they're in a (slightly) more distant solar orbit, which means they orbit the Sun more slowly than the comet itself, so the dust tail more or less follows the comet's orbit but trails behind it. We usually see the ion tail and dust tail as two separate fingers pointing to the comet.
In the unusual geometry in which Earth happens to be passing through the comet's orbital plane, the two tails are collinear, and either overlap or appear on opposite sides of the comet. If they appear on opposite sides, the ion tail still points away from the Sun, but the dust tail appears, in this rare geometry, actually to point toward the Sun. Credit: Borja Tosar |
So take out your binoculars tonight or tomorrow and try to spot the smudge of Lulin near Saturn or, later in the week, between Saturn and Regulus. And imagine the teenager in China who discovered it.
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