Dirty snowballs have got to be the best snowballs of all, but don't go running off to the store just yet -- they're definitely not available locally! In fact, I doubt anyone has ever had the chance to hold an actual dirty snowball in their own two hands; however, that's probably a good thing since they are pretty darn toxic. For those of you who haven't guessed yet what this post is actually all about let me tell you... It's about comets!!!!
That's right, comets are dirty snowballs! In all actuality, comets are asteroids comprised of dirty ice that orbit our Sun. The most visible aspect of a comet for us here on Earth is the comet's tail. As a comet's orbit brings it closer to the Sun, the ice begins to melt, creating a tail of vapors and dust that tag along behind the still solid portion, called the nucleus. The tail often consists of chemicals like diatomic C2 gas and cyanogen that appear green to us when reacting to sunlight, as you can see in the picture above of
Comet Lemmon (C/2012 F6). For more images of Comet Lemmon, and to read more about its discovery last year in Arizona by the Mount Lemmon Survey, please see the source list at the end of this post.
Speaking of Comet Lemmon, it is currently in the southern hemisphere but it is roughly at a apparent magnitude of 7. Unfortunately, the naked eye limit of apparent magnitude is a 6, meaning that it is invisible to the naked eye right now since brighter objects have lower apparent magnitudes. Don't fret though, come late March, early April Comet Lemmon should be visible in the northern hemisphere, peaking in brightness with an apparent magnitude of about 3. If you get the chance to see it, do so, because with an orbital period of about 11,000 years, this will be the only chance anyone living today will have to view this comet. Should you miss it, there will be opportunities to view at least two other comets this year. For this reason, 2013 has been dubbed the year of the comet -- in other words, keep your eye on the sky!
4 points. By the way, because the magnitudes of the comet are typically reported for the whole comet, sometimes a 5th magnitude comet is difficult or impossible to see because the light is spread out over such a large area. Essentially, it's easiest to see if all of the light is concentrated in a small area. Astronomers refer to this as "surface brightness."
ReplyDeleteYear of the comet!!
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