Comet Elenin is coming! We’re doomed! That is if you believe everything you see on the internet. Comet Elenin’s approach has been all but ignored by the mainstream media, and into this vacuum a host of bloggers and online videos have poured rumours and prophesies of death and destruction. Here are the facts about this anticipated and feared visitor from deep space.

Comet Elenin is not going to hit Earth unlike the comet in this 1998 movie. (Image Credit: Paramount Pictures)

(If you are looking for recent images of Comet Elenin go to this post: Comet Elenin images from STEREO-B spacecraft)

1. Elenin is the name of the comet, not an acronym of anything (Extinction Level Event 9?) Traditionally comets are named for their discoverers.  Comet Elenin (also known to the International Astronomical Union as C/2010 X1) was discovered by Russian amateur astronomer Leonid Elenin on 10 December  2010 using the International Scientific Optical Network’s robotic observatory near....

2. Elenin is a comet, a small and icy Solar System body. It is not a rogue planet or brown dwarf star (if it was it would be visible to the naked eye right now). It is not the same thing as Tyche (a hypothetical giant planet orbiting beyond Neptune proposed by a couple of astronomers to explain alleged irregularities in the orbits of some comets) or Nibiru (a wandering planet or star dreamt up by a couple of flaky authors in the 1990s).

3.At the time of discovery it was about 647 million km from the Sun (between Jupiter and Saturn’s orbits). Elenin is classed as a long-period comet. It takes 11 600 or so years to make a single lazy orbit of the Sun; most of this time it is very far from the Sun. It was discovered as it approaches the inner Solar System for one of its rare visits. As Comet Elenin gets nearer the Sun it is speeding up, a fact which concerns some commentators.  Spectulation about the comet being under technological control is unwarranted, its orbital motion is completely typical for such a comet, it is in no way anomalous as claimed in some parts of the internet. Astronomers are not baffled by it.

The nucleus of comet Hartley 2 seen by NASA's Deep Impact mission, Elenin's nucleus probaly resembles this object. (Image credit: NASA/JPL-Caltech/UMD)

4. The comet’s nucleus is a lump of rock and ice estimated to be about 3-4 km across, this is quite small by comet standards. As it gets closer to the Sun, solar heat warms a comet’s surface, melting and vaporising ice.  This forms a large but incredibly thin atmosphere called the coma around the comet’s nucleus. Elenin’s coma is already about 100 000 km across, this sounds enormous but is not particularly large by comet standards. Eventually, when the comet is much closer to the Sun, the coma will probably shrink somehat as the comet develops a couple of long tails, one of gas, the other of dust freed from the comet’s nucleus as the ice around it boils into space. By the autumn the tails will have developed and made the comet more conspicuous. These tails will be so thin as to be to all intents and purposes a vacuum.

5. Comet Elenin will make its closest approach to the Sun on 10 September 2011 at a distance of 0.48 AU (an AU is an astronomical unit, equal to the average distance the Earth is from the Sun). It will not collide (as claimed by some internet sources) with the Earth, nor pass between the Earth and Moon. On 16 October 2011, the comet will be at its closest to Earth, when it will be about 34.9 million km (21.7 million miles or 0.233 AU) from our planet. This is more than 90 times further than the Moon is from the Earth.

6. As Elenin will not hit Earth, some have claimed instead that its gravitational effect on the Earth’s interior will cause earthquakes and similar cataclysms on our planet, offering the recent disasters in New Zealand and Japan as harbingers of the horrors to come.  This is nonsense. I estimate the comet’s nucleus to have a mass of about 20 billion tonnes, which is vast in human terms, minute in astronomical terms. Compared to the gravitational effects of the Moon and other planets, Elenin’s effects will be immeasurably small. In fact, Dear Reader, your gravitational influence on the Earth as you sit reading these words is greater than Comet Elenin’s will be at its strongest!

7. Since it will not strike Earth, or shake up the Earth’s crust, other doomsayers state as though they actually know something that the comet’s magnetic field will pull our planet off its axis. Not only does magnetism not work like that, but comets (chunks of ice and rock, remember) do not have any magnetic field!

Comet Holmes seen by the Hubble Space telescope in autumn 2007, at its best Elenin may resemble this. (Image credit: NASA)

8. Astronomers are not expecting much from Elenin. At its brightest, Comet Elenin will be a far from spectacular sight. It will be a dim object just on the edge of visibility to the unaided eye even in the darkest sky. Binoculars will show it as a faint milky smudge from late August to October. Over the weeks it will move across the constellation from Leo, Gemini to Taurus (there is nice chart of this at http://www.curtrenz.com/comets03.html). Despite its unspectacular nature, amateur and professional astronomers worldwide will be closely scrutinising the comet. Such long period comets are of great interest for what they can tell us about conditions at the dark and distant edge of the Solar System.

9.Some claim that pictures of Comet Elenin are being ruthlessly suppressed by some government conspiracy but this is a lie.  Astronomers, including amateurs, have photographed the comet. You can find a collection them at Seiichi Yoshida’s comet webpages.

10. Comet Elenin’s approach is not being covered up by the media or authorities. Articles on it have appeared in astronomy magazines and there has even been a press release from NASA. It has not been announced all over the BBC and CNN simply because it is just another small and dim comet like so many others (around a hundred comets were discovered in 2010, did any of them get any media coverage?) The most mysterious part of the whole affair is why so obscure a celestial body has caught the imagination of conspiracy theorists.

Finally, if anyone alarms you with grim predictions of doom about this little comet don’t just accept them, challenge them, ask for evidence, calculations and sources. Fight back against fearmongering!

Update (2 August 2011)

I have now created a new post about Comet Elenin pictures where I will place interesting new images from the STEREO observatory as they come in. Come and see what it really looks like!

Resources

The announcement of the discovery

The Wikipedia page about the comet

Ian Musgrave on Elenin and earthquakes, and again, Elenin FAQ.