PDA

View Full Version : DUCK! - Closest asteroid flyby ever



ToSeek
2004-Mar-18, 04:50 AM
Astro-Alert from Sky and Telescope:


Less than 24 hours from the time this message is being issued, a tiny, newly discovered asteroid will make the closest flyby past Earth that has ever been predicted by astronomers.

The object, dubbed 2004 FH, is probably only about 20 meters in diameter (the size of a house). An electronic circular issued late on March 17th by the Minor Planet Center in Cambridge, Massachusetts, indicates that it will definitely not hit the Earth. It will pass about 49,000 kilometers (30,500 miles) from Earth's center, which is one-eighth the distance of the Moon.

This object was discovered on March 16th by astronomers of MIT's Lincoln Near-Earth Asteroid Research (LINEAR) survey in Socorro, New Mexico. Further observations made on the 17th at Klet Observatory (Czech Republic), Starkenburg Observatory (Germany), and Modra Observatory (Slovenia) helped the Minor Planet Center compute its exact trajectory.

The flyby scenario for 2004 FH goes like this:

* At 18 hours Universal Time on March 18th, the asteroid will be 12th magnitude as it glides just south of the star Spica in Virgo, heading west.

* By 22 hours UT on the 18th, it will have brightened to 10th magnitude when it passes closest to Earth in the constellation Antlia.

* At 0 hours UT on March 19th -- which is around the time darkness falls on the East Coast of North America on Thursday, March 18th -- it will have faded back to 12th magnitude as it shoots by Sirius near the open star cluster Messier 41. By then it will be receding from Earth and heading back into space.

Because 2004 FH will be passing so close, it is not practical for me to include a detailed ephemeris in this message. Its path across the sky depends greatly on an observer's vantage point on Earth (owing to the parallax effect). Observers who wish to locate it in small telescopes should use the Minor Planet Center's Ephemeris Service to make detailed predictions for their own geographic location:

http://cfa-www.harvard.edu/iau/MPEph/MPEph.html

According to the orbit calculated by Gareth Williams, associate director of the Minor Planet Center, 2004 FH belongs to the Aten class of asteroids. It circles the Sun in just under 9 months in very nearly the same plane as Earth's orbit. At perihelion it swings well inside the orbit of Venus; at aphelion (as currently) it ranges just outside that of the Earth.


Roger W. Sinnott
Senior Editor
SKY & TELESCOPE
[/quote]

Kaptain K
2004-Mar-18, 05:16 AM
Wow! :o Close call!

Brady Yoon
2004-Mar-18, 05:22 AM
would this asteroid burn up int the earth's atmosphere?

Anthrage
2004-Mar-18, 05:23 AM
Heh. Objects of this size 'hit the earth' every year, about once a month. On September 27th of last year, one passed within 88,000km. It is somewhat amusing that objects which pass closer and closer get a good deal of press, but the ones of similar size that hit us are not on the radar whatsoever. :)

Of course, if it were up to me, both classes of objects would get the greater attention they deserve...hopefully the most important aspect of this, the very short lead time (understandable given the object's small size), and that of other such objects, impacting or not, will receive more than token press. It's really pretty disturbing.

Ah, The Daily Show had a bit on Senda. Hmmm...

Kaptain K
2004-Mar-18, 05:30 AM
Somebody correct me if I'm wrong, but I was under the impression that the "one a month" was for objects in the 5-10 meter range.

Kaptain K
2004-Mar-18, 05:31 AM
would this asteroid burn up int the earth's atmosphere?
Depends on its composition.

Anthrage
2004-Mar-18, 05:50 AM
The reports I've seen run from 10 to 15 a year, but I wouldn't suggest it is consistent by any means.

And yes, the object would burn up if it were of a less dense composition. If not, small fragments may survive entry.

As example, there was an object reported to be house-sized that entered the skies above spain on January 4th, 2004. Several fragments touched down as meteorites - one can be seen here (http://www.meteor-center.com/dossier/espagne2004/). Another report, and some video of the fireball, can be found here (http://www.xs4all.nl/~dmsweb/fireballs/20040104_fireball.html).

tracer
2004-Mar-18, 06:34 AM
The object, dubbed 2004 FH, is probably only about 20 meters in diameter (the size of a house).
A two-story, 5 bedroom house, at least.

Kaptain K
2004-Mar-18, 07:28 AM
And yes, the object would burn up if it were of a less dense composition. If not, small fragments may survive entry.
A solid nickel-iron meteor that size would probably survive atmospheric entry pretty much intact. It would also make a good sized hole in the ground! :o

John Kierein
2004-Mar-18, 10:16 AM
The closer it gets, the bigger it gets. Now they say 30 meters in diameter. That's more than 3 times bigger than 20 meters (in volume).

Maksutov
2004-Mar-18, 10:47 AM
The object, dubbed 2004 FH, is probably only about 20 meters in diameter (the size of a house).
A two-story, 5 bedroom house, at least.

Well, depends on which state is your baseline. In Alabama that would be a decent-sized, repossessed doublewide with green pine deck, which would, of course, burn to bits in the upper reaches of the ionosphere.

Maksutov
2004-Mar-18, 10:57 AM
Remember, the vast majority of these that make it to the surface either land in an ocean or in a remote, unpopulated area. One of these days, though...

bmpbmp
2004-Mar-18, 11:17 AM
I heard that this one in particular was only 100 feet, is that right

majic
2004-Mar-18, 12:35 PM
I heard that this one in particular was only 100 feet, is that right

100 feet is 30 meters, which is 10 meters larger than the 20 meters stated in the original posting and the same as stated just a few posts above you ;-)

I dont understand the "was only", which makes it appear like you feel 100 feet is less than 20 or 30 meters :)

tngolfplayer
2004-Mar-18, 12:55 PM
I was trying to see if it would be visible here when dark comes, but I think it will making its return to space around dusk. According to this (http://cfa-www.harvard.edu/iau/MPEph/MPEph.html) anyway. I think my astro-alert said the brightest would be Mag 10.

HAVOC451
2004-Mar-18, 01:38 PM
Darnit! I wont be able to watch it go by from here. :(

Edoltc
2004-Mar-18, 02:26 PM
A solid nickel-iron meteor that size would probably survive atmospheric entry pretty much intact. It would also make a good sized hole in the ground!
How big! :o I mean, what would happen if this nickel-iron met hit the ground near a populated area. There is any study about the composition of 2004 FH?

Stagefright
2004-Mar-18, 03:15 PM
Astronomer Steve Chesley of JPL (on CNN):

The important thing is not that it's happening, but that we detected it
CNN story (http://www.cnn.com/2004/TECH/space/03/18/asteroid.ap/index.html)

Similarly sized asteroids are believed to come as close to Earth on average once every two years, but have always escaped detection.

Anthrage
2004-Mar-18, 03:53 PM
Hmmm - well, there are at least 3 in the last 6 that I can think of off the top of my head, mentioned in this post - once every two years is not accurate at all. Very odd.

jami cat
2004-Mar-18, 03:57 PM
So what happens after the trajectory shifts 15deg.?
http://www.space.com/scienceastronomy/asteroid_flyby_040318.html

Does it go around the sun and come straight at us next year?

Or, will it take a few more passes?

I wanna see fireworks :o

Kaptain K
2004-Mar-18, 04:41 PM
I wanna see fireworks
I wanna be far enough away to be able to say "What was that?" :o :wink:

Tito_Muerte
2004-Mar-18, 05:24 PM
Ah, The Daily Show had a bit on Senda. Hmmm...

heh heh...I saw that too...most excellent.

hedin
2004-Mar-18, 07:37 PM
The koo koo´s and the woo woo´s are having a feelday over this on GLP

Swift
2004-Mar-18, 08:39 PM
CNN.com's poll today was "Do you worry about an asteroid hitting Earth?". As of 3:37 EST, about 143,000 people had responded and only 14% said yes. I guess its good that the majority don't worry, but its not good to convince the governement to fund NEO research.

skrap1r0n
2004-Mar-18, 10:06 PM
This would be an interesting test to see if we could launch a missile and hit it. I'm sure theres an ICBM laying around somewhere. It would be fantastic to try to hit it and observe what happens.

roidspop
2004-Mar-19, 03:44 AM
I've tried to calculate how much energy the thing would deliver assuming it's 100 ft in diameter and traveling at 24 miles per second.

If it's made of rock, it would be carrying about 6.7 megatons worth of kinetic energy as it reached the upper atmosphere. If it were iron, that would rise to about 21 megatons.

In Richard Norton's book, "Rocks from Space", there's a chart that shows that a 1000 ton object, about 4 times smaller than this object, would retain 70% of it's initial velocity on impact. Another chart shows that at this speed, about 55% of the original mass could be retained to the ground. Assuming that the rock could reach the ground, it would deliver about 1.8 megatons...this probably wouldn't happen, though, since most rocky meteoroids blow apart high in the atmosphere. There'd be a big light show and a good shock wave, but probably no impact. The iron would be a different story. It would hold together very nicely and deliver about 5.3 megatons of energy on impact...instant tourist attraction.

A big iron meteorite struck in the Sikhote-Alin region of the Soviet Union on 12 February 1947...the biggest crater was about 87 feet in diameter and 20 feet deep; but the meteorite that caused this damage was much smaller than the one that missed us today.

Arithmetic errors and such aside...I'm glad it missed!

ToSeek
2004-Mar-19, 04:26 AM
You can play around with speeds, sizes, and types on this page. (http://janus.astro.umd.edu/astro/impact.html) A couple of quick entries gives a Tunguska-style atmospheric explosion for an ice or rock meteor of the given size, and a close to 1-km crater for an iron one.

hedin
2004-Mar-19, 10:49 AM
thanks for the great link ToSeek

ToSeek
2004-Mar-19, 02:32 PM
thanks for the great link ToSeek

It's one of my favorites. If you want to get Marvin mad, though, send a 9999 km iron asteroid into Mars. ;)

hedin
2004-Mar-19, 03:35 PM
LOL reminds me of Marvin The Paranoid Android from Hitchhiker´s Guide to The Galaxy

Edoltc
2004-Mar-19, 03:45 PM
Great link ToSeek

tracer
2004-Mar-22, 12:39 AM
If you want to get Marvin mad, though, send a 9999 km iron asteroid into Mars. ;)
Even better -- look at what Marvin does if you send a 999 km rock asteroid into Mars at 20 km/s.

ToSeek
2004-Mar-22, 02:48 AM
If you want to get Marvin mad, though, send a 9999 km iron asteroid into Mars. ;)
Even better -- look at what Marvin does if you send a 999 km rock asteroid into Mars at 20 km/s.

I should have mentioned that one, too.