Normally I wouldn’t spend so much time on a comet that most people won’t be able to see until October, but Comet Elenin is special. There’s so much misinformation online about this rather ordinary object that I thought it time again to share what I know from my observations and those of others.
New brightness estimates based on the comet’s current light curve and tables prepared using the NASA’s extremely useful Horizons site indicate that Elenin will only reach 6th magnitude when brightest in the fall. Since magnitude 6 is the naked eye limit for stars seen from a dark site, that means we’ll need binoculars to see it.
But I’m getting ahead of myself. Currently the comet is in the constellation Leo the Lion, where it will remain until August 7, when it moves into Virgo. Leo is sinking in the western sky for observers in the northern hemisphere. Matter of fact, Comet Elenin is now so near the western horizon by nightfall, that few if any observers living in mid-northern latitudes will see it again until it returns to the morning sky in October. The comet remains stubbornly dim with a current magnitude of around 12. Combine that with the usual low altitude haze and you’ll need a very large amateur telescope to pluck it.
The situation improves the farther south you live. Here in Duluth, Elenin is only about 10 degrees high by the time it’s dark enough to look for it, while in Tucson, Ariz. it’s closer to 20 degrees. As you can see from the illustration above, the best views are from the southern hemisphere.
Elenin hugs the horizon and remains in twilight from the northern U.S. and Canada now until it pops into the morning sky in October. Happy trails till we meet again! Those living in the southern hemisphere however will continue to be able to watch the comet all the way into early September, when it might reach 7th magnitude.
From mid-September through the start of October no one will see Elenin, because it will be too near the sun and invisible in its glare. Around October 4, it will enter the morning sky in fine form in Leo for observers in the northern hemisphere. Since the comet is closest to Earth around this time, it will cover ‘ground’ quickly, becoming easier to see each morning as it moves higher in the sky. Because of the comet’s angle to the horizon, southern hemisphere observers will need to wait a few more days for its re-appearance.
Comet Elenin is one of many comets visible in the sky in 2011. At the moment there are are about a half dozen, most of which of which are on the faint side like Elenin, requiring at least an 8-inch telescope and dark skies to see.
People always want to know how big the comet is. Most comets are smaller than 6 miles across and Elenin appears to be no exception.Â Since that’s less than a billionth of the mass of the Earth, its gravitational effect on us is positively miniscule. Add in the fact that at closest on October 16, the comet will be 22 million miles from Earth, and there’s nothing to fear. Consider that Venus is nearly the same distance – 26 million miles – at inferior conjunction every couple years with no ill effects. Heck, that’s an entire planet!
According to Don Yeomans of NASAâ€™s Near-Earth Object Program Office at NASAâ€™s Jet Propulsion Laboratory: “Comet Elenin will not only be far away, it is also on the small side for comets. And comets are not the most densely-packed objects out there. They usually have the density of something akin to loosely packed icy dirt.”
The following is a list of things to look forward to as Comet Elenin gradually brightens up in the next few months. Consider it an Elenin ‘planner’, but remember – while distances and visibility prospects aren’t likely to change, it’s possible the comet might be brighter or fainter than expectations. Of course, we always hope for brighter! And although Elenin has only a short, faint tail at the moment, it will undoubtedly develop a brighter, longer one as it gets closer to the sun. And if it does anything crazy, I’ll update you right here.
* June 28 – Currently at 13 magnitude and 165.5 million miles from Earth. Located low in the western sky and nearly impossible to see from more northern latitudes.
* August 7 – Moves from Leo in the constellation Virgo. Earth distance: 133 million miles. Now at 10th magnitude. Might still be visible from the southern U.S. very low in the west during late twilight through a telescope.
* First week of September – Now at 7th magnitude and visible in binoculars very low in the west to experienced observers in the southern hemisphere. Earth distance on the 3rd: 84.3 million miles
* September 11 – Perihelion or closest approach to the sun. Sun-comet distance: 44.6 million miles. Earth distance: 65.1 million miles. Comet lost in the sun/twilight glare and not visible. Magnitude 6.2
* September 26 – Elenin about 2.25 degrees due north of and in conjunction with the sun (closest to the sun seen from Earth) . Contrary to what some websites are saying, it won’t ‘eclipse’ the sun. It won’t even pass in front of the sun from our perspective. The comet will shine at magnitude 6.0 but won’t be seen because of solar glare. Earth distance: 36.7 million miles
* Around October 4 – It’s finally here! Appears low in the morning sky at dawn in the constellation Leo while fading to magnitude 6.3. Earth distance: 27.9 million miles
* October 16 – Closest approach to Earth at 21.7 million miles. Magnitude 7.0