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Armilus
2004-Jun-26, 03:24 PM
What is the size of this asteroid that'll pass closer to us than the Moon on June 29? Will it's passing be visible with binoculars?
http://neo.jpl.nasa.gov/cgi-bin/db_shm?des=2004+MC

milli360
2004-Jun-26, 05:54 PM
What is the size of this asteroid that'll pass closer to us than the Moon on June 29? Will it's passing be visible with binoculars?
http://neo.jpl.nasa.gov/cgi-bin/db_shm?des=2004+MC
I answered this question (http://www.badastronomy.com/phpBB/viewtopic.php?t=14579) in Against the Mainstream, before I noticed it here in General Astronomy. This is probably the more appropriate place.

By my calculations, that's a miss by 900,000 miles, more than three times the distance to the moon.

JustAGuy
2004-Jun-26, 06:57 PM
What is the size of this asteroid that'll pass closer to us than the Moon on June 29? Will it's passing be visible with binoculars?
http://neo.jpl.nasa.gov/cgi-bin/db_shm?des=2004+MC
It looks to be Mag 23, so it's probably not very big at all, and you will definitely not be able to see it with binoculars.

Superluminal
2004-Jun-27, 01:30 AM
I checked the NEO site. Absolute mag. is 23, that is its mag. when at distance from both the Earth and sun of 1 AU. However, visual mag. when at perihelion and a distance from Earth of .016 AU is expected to be 15.46, probablly not much bigger than a small mountain.

beskeptical
2004-Jun-27, 08:26 AM
spaceweather.com says:

ASTEROID FLYBY: Asteroid Itakowa flew past Earth on June 26th, five times farther away than the Moon. Southern-hemisphere astronomers can still see it using backyard telescopes. It's glowing like a 12th magnitude star in the constellation Canis Major (ephemeris). Japan's Hayabusa spacecraft is en route to Itakowa now. After catching the asteroid in 2005, Hayabusa will gather samples from it and return them to Earth in 2007. and that it will be mag 13.

Brady Yoon
2004-Jun-27, 07:36 PM
How bright would a large asteroid like Ceres with an average albedo (say the moon) appear at the same distance as the moon?

milli360
2004-Jun-27, 08:00 PM
How bright would a large asteroid like Ceres with an average albedo (say the moon) appear at the same distance as the moon?
On May 1, 2005, from the Earth, Ceres will be mag. 7.0, and 250 million km from the Earth. The moon is about 400,000 km away, so if Ceres were at that distance it would by brighter by a factor of (2500/4)^2, or about 400,000 times, an increase of 14 magnitudes, so to about -7.0.

PS: 'Course, if it were that close, it would be closer to the Sun, and even brighter, maybe a magnitude.

Brady Yoon
2004-Jun-27, 08:06 PM
On May 1, 2005, from the Earth, Ceres will be mag. 7.0, and 250 million km from the Earth. The moon is about 400,000 km away, so if Ceres were at that distance it would by brighter by a factor of (2500/4)^2, or about 400,000 times, an increase of 14 magnitudes, so to about -7.0.

Gee, thanks for the quick replies. :) But Ceres would also be about 3 closer to the sun, and the reflected sunlight would respectively 9 times brighter. Wouldn't this also be a factor (a small one)?

milli360
2004-Jun-27, 08:10 PM
Brady Yoon:
But Ceres would also be about 3 closer to the sun, and the reflected sunlight would respectively 9 times brighter. Wouldn't this also be a factor (a small one)?
The same thought occurred to me after I posted, but not in time before your post. :)

It's not quite 3 times, more like 2.5, so it would be two magnitudes. Maybe -9.0 then. Some of the Iridium flares get that bright.

Armilus
2004-Jun-28, 12:49 AM
"Moreover the light of the Moon shall be as the light of the Sun, and the light of the Sun shall be sevenfold the light of Seven Days" (Isaiah 30). Praise the Lord!

milli360
2004-Jun-28, 03:57 AM
Praise the Lord

Armilus:
"Moreover the light of the Moon shall be as the light of the Sun
The magnitude of the even the full moon would have to increase 14 magnitudes, so about 400,000 times.

Ulster
2004-Jun-28, 02:57 PM
Today's asteroid will pass 3.7 lunar distances away. The estimated size is between 63-140 metres.

Armilus
2004-Jun-28, 04:19 PM
If a third of the asteroid reached the Earth's surface ie a 30 metre bolide, at what sort of speed would it impact and with what result eg in the center of London?

Kaptain K
2004-Jun-28, 04:43 PM
If a third of the asteroid reached the Earth's surface ie a 30 metre bolide, at what sort of speed would it impact and with what result eg in the center of London?
1) Minimum of 11 Km/sec (Earth's excape velocity).
2) There would be no London!

milli360
2004-Jun-28, 05:17 PM
Kaptain K:
1) Minimum of 11 Km/sec (Earth's excape velocity).

Why minimum?

Armilus
2004-Jun-28, 06:06 PM
A 15 metre radius bollide with a density of 5g/cc and a speed of 40,000 km per hour has approx 10^14 J of kinetic energy. Is that enough to wipe out London?

Ulster
2004-Jun-28, 07:21 PM
The relative velocity of 2004 MC is 8.69 km/s, or 31,000 km/hr. NASA estimates a potential impact energy of 21 Megatons.

Brady Yoon
2004-Jun-28, 08:58 PM
Why minimum?

I would like to know that too.