[meteorite-list] Asteroid 136849 approaching (over 1 km in diameter)

[mexicodoug at aim.com]

Dear Listees,

Thought I'd pass along to anyone interested in seeing a typical Hammer 
of God asteroid (no, it is not called Kali, but it really does have a 
devil of an orbital period: 666 days), in the form of Chinese 
discovered potentially threatening asteroid (136849) 1998 CS1 (That's 
CS1, not CSI :)).  This asteroid is likely well over 1 kilometer in 
diameter and will be paying us a quite "close" visit on January 17 at 
about 5:00PM London time, when it will be about 4.35 million kilometers 
away (2.7 million miles) from Earth.  That's about 11 Lunar Distances 
(11 times the distance from the Earth to the Moon).

For comparison, 4179 Toutatis, which made for a great deal of drama on 
29 Sep 2004, is about twice the diameter of 136849 1998 CS1 and passed 
by Earth at 4 LD's.  It was supposedly 10th magnitude, 5 times 
brighter, but was not as optimally placed to see for many of us.

Due to 136849's phase, it will actually be brightest tomorrow night 
(sometime between 10 PM and 12:30 AM) or whenever is just before 
Moonrise if you are in the northern hemisphere north of at least 15 
degrees latitude or so.  If you are South of that you need to put up 
with the fairly bright Moon but can try to look at it starting a couple 
of hours after Moonrise 'til dawn.

I think I'll give it a shot if conditions are ok, since it would be 
nice to see something this big, this close - about
 the same level of 
difficulty as Toutatis was.  For me timing critical as it will barely 
rise 15 degrees above the horizon when the Gibbous Moonriserises a 
little before midnight local time.  But if you are a Hamburger 
(Germany) or Juneauean (Alaska), you can observe for at least two hours 
before Moonrise preferably in thermal knickers...

The predicted visual magnitude will be 12.25, well within the range of 
amateur telescopes.  It will be moving against the starry background at 
about 40 arcseconds per minute which is a third more that the diameter 
of Jupiter, for comparison, and a very comfortable speed for 
observation.  It's roughly between the Big Dipper of Ursa Major (the 
Plough) and Leo.

For statical thoughts, anything coming within 11.31 LD's of Earth is 
ROUGHLY about one half-millionth a 'chance' to hit Earth by just 
looking at cross sectional area, and Earth occupies about one three 
hundred and twenty millionth of the volume of the sphere centered on 
Earth with a radius of 11.31 LD.  And to think a LD (Lunar Distance) 
makes it seem so familiar and close!  In 2080, it will pass by at 9.4 
LD's if all goes according to plan...after a few close ones with Venus, 
too...

BTW today, the STARDUST spacecraft just passed Earth a couple of hours 
ago at 0.023 LD's, I think!

Here's the orbit of 136849:
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=136849;orb=1

Here´re the discoverers:
http://ww
w.bao.ac.cn/bao/station/xl/index-e.html

Best wishes and Great Health,
Doug