The Gegenschein as seen from Chile. (Credit: Yuri Beletsky & the ESO)
This weeks’ Astro-challenge to the world (and myself) is to sight that most elusive of astro-beasts, the Gegenschein. Surprisingly, more pictures of Sasquatch on Mars or Paris Hilton in prison exist than of this faint phenomenon. Sometimes called “counter-glow,” this faint glowing patch occurs near the antihelion or spot opposite to the Sun. This week is a good time to check this item off of your life list, as the Moon is at new phase and the antihelion is riding high in the sky around midnight local in the northern hemisphere. The winter sky also is relatively devoid of an interfering Milky Way. Absolutely dark, clear skies are a must for this one! No less a seasoned astro-blogger than myself has yet to see this phenomena… but I promise I’ll try along with you, the astro-blog reading public! I suspect a polling of your local astronomy club would reveal less than 10% of amateurs have ever seen, or even heard of this phenomenon. It also doesn’t hold up well to scrutiny with techie toys, which may be another reason for its continued unpopularity. In theory, an old fashioned time exposure shot from a well aimed, well tracked wide camera centered on the Taurus-Aries region should reveal it. Let us know of any successes/ failures/thoughts on life, or silhouettes of Bigfoot with Paris in the Gegenschein. Good luck!
Our Astro-word of the week is, non-coincidentally, Gegenschein. This dim patch opposite to the Sun is caused by a focused reflection of the Sun on interplanetary dust trapped in the solar ecliptic. It’s also thought that some of this material is also “clumped up” at the anti-sunward (L2) Lagrange point. About 10 degrees or 20 full Moons in diameter, this luminosity is also relatively distinct because we see the particles in full phase. In German, Gegenschein literally means ”counter-shine.”