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

From: mexicodoug at aim.com <mexicodoug_at_meteoritecentral.com>
Date: Fri, 16 Jan 2009 17:58:15 -0500
Message-ID: <8CB46450BD4E78C-794-1087_at_mblk-d16.sysops.aol.com>

Dear List,

Drat's, I was completely rained out and will be again tonight, and then
it head a little too "north" for me. Did anyone see this potential
hammer asteroid inchworming from Ursa Major past Arcturus and towards
Corona Borealis (actually it is thought to be a non-carbonaceous stony
asteroid)?

There is still plenty of time for the next two or three days to see it
as it fades to Pluto brightness from its current status a being visible
through big binoculars or amateur scopes. The actual closest approach
is on January 17 at a couple minutes past 17:00 London time.

There is no chance this asteroid will hit Earth anytime soon, but is a
good illustration of what is being done to track potentially
Earth-threatening objects. Both the Puerto Rico's Arecibo (
http://www.naic.edu/public/the_telescope.htm ) and the Mojave Goldstone
dishes ( http://www.jpl.nasa.gov/images/dsn/goldstone/ ) Gigantic Radio
telescopes, on the NASA/NSF/UStaxpayer payroll, are dedicating serious
time to it to figure out its shape, and whatever else they can glean,
which while an academic question in this century, could help with
strategies to deflect it if necessary at a time in the far
future...Typically I think up to ten asteroids monthly (all PHA's,
potentially hazardous) are within range and under RADAR study at these
installations. It is also a Grrrrreat time to do some spectroscopy on
the relatively intense light detectable from Earth during
 this pass.
Basically, taking spectra of the reflected light and analyzing which
colors/wavelengths are strongest to get a handle on the composition.
Can't wait to find out what new is learned.

Hopefully Arecibo stays afloat...:-)

Here are the scheduling pages to see the crunching going on for over a
week of observations (as we speak errr...breathe) to see what is being
done about this object that will pass 11.31 LDs (Lunar Distances) from
Earth:

http://echo.jpl.nasa.gov/asteroids/1998CS1/1998CS1_planning.html

Regarding the distance and its associated dangers - Here is an
illustration of ONE Lunar Distance:

http://tinyurl.com/9vyyty

This is a rather big one and events concerning asteroids this size and
proximity happen at best a a few times a year in a fun year.

A couple of clarifying comments, the info on this web page indicates
the Japanese were the ones who discovered it first, at this place,

http://www.kumakogen.jp/culture/astro/astro_e.html

Well the Japanese data is two days after the Chinese data so I don't
know what's the problem with the crediting of the discovery. Second it
mentions that the asteroid measures 0.9 km in diameter plus/minus a
FACTOR OF TWO. That puts it between 0.5 and 1.8 km in diameter - so it
is very likely to be over 1 km in diameter the catastrophic arbitrary
threshold many talk about.

Best wishes and Great Health,
Doug





-----Original Message-

----
From: mexicodoug at aim.com
To: Meteorite-list at meteoritecentral.com
Sent: Wed, 14 Jan 2009 5:10 pm
Subject: Asteroid 136849 approaching (over 1 km in diameter)
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 starti
ng 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=2
0STARDUST 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?
?

Received on Fri 16 Jan 2009 05:58:15 PM PST