600.000years ago, mans ancestors might have looked up and seen a brihgt comet in the sky, wandering what it was. Now the same comet returns, passing close by Earth Oct. 16th to a new renevouz with the Sun.

The comet who has been named Elenin, will be brigth enough to be seen with the unaided eye from a dark location when it passes Earth, and will keep the same magnitude for an entire month, when it
Also known by its astronomical name C/2010 X1, the comet was first detected on Dec. 10, 2010 by Leonid Elenin, an observer in Lyubertsy, Russia, who made the discovery "remotely" using an observatory in New Mexico. At that time, Elenin was about 647 million km from Earth.

Since its discovery, Comet Elenin has – as all comets do – closed the distance to Earth's vicinity as it makes its way closer to perihelion, its closest point to the sun.
Eventhough 35mill. km is a close distance from Earth comet-wise, it is still 90x the distance of the Moon, and will pose no threath to Earth.

At present it is magnitude 10, which requires a 150mm telescope to see. Over the next month it will brighten gradually while moving from the constellation Virgo to Leo. When it is closets to Earth at Oct. 16th, it will have brigthened to magnitude 6, and should be just visible to the unaided eye.

"We're talking about how a comet looks as it safely flies past us," said Don Yeomans of NASA's Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory "Some cometary visitors arriving from beyond the planetary region – like Hale-Bopp in 1997 -- have really lit up the night sky where you can see them easily with the naked eye as they safely transit the inner-solar system. But Elenin is trending toward the other end of the spectrum. You'll probably need a good pair of binoculars, clear skies, and a dark, secluded location to see it even on its brightest night."

This intrepid little traveler will offer astronomers a chance to study a relatively young comet that came here from well beyond our solar system's planetary region. After a short while, it will be headed back out again, and we will not see or hear from Elenin for thousands of years.

Usually comets have a hard crust, but young comets like Eleni are more porousies, and more likely to show jets and outbursts. So with a lttle luck, Eleni could brigthen and/or show jets or break-offs like comet Holmes did in 2007.

So make a note in your calendar for Oct. 16, and try to follow it in late sept, when it re-emereges from the Sun. By that time, it will be well-situated in Auriga, high (20-25o) in the eastern horizon at magnitude 6-7 and with a noticable tale.

Sources and further reading:

Yoshidas Cometary page
NASA press-releases 1 and 2 and
Wikipedia