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Glom
2010-Sep-08, 07:20 AM
Two asteroids with pass through the geosphere today, one getting close to geostationary distance. Apparently, you still need a telescope to view them though. But despite being called asteroids, the largest is smaller than 20m across. Don't asteroid need to be 100m across to be called asteroids.

http://www.nasa.gov/topics/solarsystem/features/asteroid20100907.html

Hornblower
2010-Sep-08, 09:39 AM
Two asteroids with pass through the geosphere today, one getting close to geostationary distance. Apparently, you still need a telescope to view them though. But despite being called asteroids, the largest is smaller than 20m across. Don't asteroid need to be 100m across to be called asteroids.

http://www.nasa.gov/topics/solarsystem/features/asteroid20100907.html

I never heard of any such standard. If it can be seen with a telescope I would call it an asteroid. If not, I would call it a large meteoroid.

AndreasJ
2010-Sep-08, 10:09 AM
There seems to be various cut-off sizes for asteroids v. meteoroids in circulation. The WP page on meteoroids mentions 10 m and 50 m, and I believe I've heard 100 m before.

Jeff Root
2010-Sep-08, 10:26 AM
If it can be seen with a telescope I would call it an asteroid.
If not, I would call it a large meteoroid.
Yay!!! That's the standard I worked out, myself.

Here's a link to my still-unfinished web page on the subject:

http://www.freemars.org/jeff/meteor/

-- Jeff, in Minneapolis

Swift
2010-Sep-08, 01:55 PM
Glom, I think you are missing one "a" from your title. :D

Nick Theodorakis
2010-Sep-08, 03:05 PM
Glom, I think you are missing one "a" from your title. :D

No, it just looks that way because he has one too many "h"s.

If in asteroid is less than 100 m, the IAU is recommending they be called "dwarf asteroids." Or maybe "asteroidoids."

Nick

DonM435
2010-Sep-08, 04:40 PM
Glom, I think you are missing one "a" from your title. :D

No, I'd sy tht he used this pges llottment of the letter "" for the entire dy!

Buttercup
2010-Sep-08, 05:37 PM
My challenge to Outer Space: BRING IT ON!

:p

AndreasJ
2010-Sep-08, 05:43 PM
My challenge to Outer Space: BRING IT ON!

We'd like to propose a deal: you lot produce one year, just one year, that no crackpot proclaims to be the last, and we send a biosphere-killer for New Year's Eve that year.

xylophobe
2010-Sep-09, 01:21 PM
Hi Jeff,

I like your website, but I have a question.

Under the "Origins" section it shows a disk of particulate matter that is swept clean by planets that are forming and so I wonder how the planet can sweep its orbit clean since the dust particles should all be traveling at the same orbital velocity as the planet since both the planet and the particles are orbiting at the same distance from the sun? If the particles were traveling slower then they would fall to a lower orbit.

Jeff Root
2010-Sep-09, 02:38 PM
I don't know the details.

I do know that planets are believed to sweep their orbits clear of dust,
as you have undoubtedly heard elsewhere.

I just learned a few days ago in another thread that the density of gas
in the disk is great enough to give it significant pressure. I should have
realized that long ago. The pressure means the gas molecules constantly
bump into one another, and that causes them to orbit at less than their
keplerian speeds without falling inward. So the planets, orbiting with
keplerian speeds, gain on the gas molecules. The dust is entrained in
the gas to a large extent, as happens in Earth's atmosphere, (To the
extent it is *not* entrained, the gas and dust separate like the gas and
dust tails of comets.) So the dust is slowed down with the gas. The
planets can either capture the matter or send it outward, inward, or
away from the plane of the disk.

Looking at it purely ballistically, any particle is likely to be in an orbit
that is nearly but not exactly circular. It is most likely to interact with
a forming planet when at periastron or apastron, at which point its
orbit will be changed markedly. This tells me that a rather broad swath
should gradually be cleared.

I take clues from the rings of Saturn, but there are some major differences
between the very thin disk of particles in Saturns rings and the thicker
protostellar disk composed primarily of gas, so the clues only go so far.

-- Jeff, in Minneapolis

Noclevername
2010-Sep-12, 12:23 PM
Two asteroids with pass through the geosphere today, one getting close to geostationary distance.

:eek:(shudder) Yet another example of why we need a Meteor Guard.

Jeff Root
2010-Sep-12, 01:30 PM
Well, they *did* have a pass. The guard must have let them through.

-- Jeff, in Minneapolis

astromark
2010-Sep-13, 07:26 AM
Meteor, Asteroid, Meteoroid. Lump of scree or just a Rock... and some 'other' names spring to mind.

I do not care for the argument of what to call it. As long as we call it and track it passing by... a miss is another chance...

Ah! is hardly a clue as to the threads content is it ? I would have named it ' Hay, look at that.'... but thats not my call is it.

Only a few years back we would not have known of this event until it happened or never.

The equipment and hardware to detect such small asteroids zipping past Earth has improved and is improving still..

Glom
2010-Sep-13, 07:40 AM
Glom, I think you are missing one "a" from your title. :D

Not in British English it isn't!

Jens
2010-Sep-13, 10:02 AM
Under the "Origins" section it shows a disk of particulate matter that is swept clean by planets that are forming and so I wonder how the planet can sweep its orbit clean since the dust particles should all be traveling at the same orbital velocity as the planet since both the planet and the particles are orbiting at the same distance from the sun?

I'm not exactly sure of the answer either, but I think one issue is what Jeff Root brought up, that they will never be in exactly the same orbit. They may be very close, but no two things would ever have precisely the same orbit. The other issue is that they will be affected by other bodies as well, so each body will receive a slightly different effect from say Jupiter, so that they would not maintain exactly the same orbit anyway. So in the long-run, any small bit of dust will get close enough to the earth that it will be thrown out of the area.