Posted on 10/21/2002 2:37:19 PM PDT by blam
Monday, 21 October, 2002, 16:27 GMT 17:27 UK
Earth's little brother found
The asteroid was found almost by accident
By Dr David Whitehouse BBC News Online science editor
Astronomers have discovered the first object ever that is in a companion orbit to the Earth.
Asteroid 2002 AA29 is only about 100 metres wide and never comes closer than 3.6 million miles to our planet.
But it shares the Earth's orbit around the Sun, at first on one side of the Earth and then escaping to travel along our planet's path around the Sun until it encounters the Earth from the other side. Then it goes back again.
Researchers are speculating that 2002 AA29 could be visited by astronauts or used to understand the threat to our planet posed by such rocks from space.
Co-orbital object
2002 AA29 was discovered by the linear automated sky survey project on 9 January 2002.
Martin Connors of Athabaseca University in Canada writes in the journal Meteoritics and Planetary Science that it, "moves in a very Earth-like orbit," and is the "first true co-orbital object of Earth."
2002 AA29 has a bizarre horseshoe orbit around the sun
General Simon Worden of the United States Space Command described it as a "near Earth object that is close to being trapped by the Earth as a second natural satellite".
According to Helena Morais of the University of Lisbon and Allesandro Morbidelli of the University of Nice, writing in a paper to be published in the journal, Icarus: "2002 AA29 seems to be in a temporary horseshoe-like orbit with the Earth."
This puts 2002 AA29 is in the same class as 3753 Cruithne, a similar rocky body in a horseshoe orbit around the Earth.
But astronomers classify 2002 AA29 as the first real co-orbital body found associated with the Earth because it more completely shares the Earth's path around the Sun.
Co-orbiting asteroids have been found around other planets.
near Earth object that is close to being trapped by the Earth as a second natural satellite
General Simon Worden US Space Command
Over 1,200 so called "Trojans" have been found moving either ahead or behind Jupiter.
Eight such objects have been found associated with Mars.
But despite detailed searches no one has yet found any Trojan objects near the Earth.
It is clear that 2002 AA29 was discovered by accident at a time when it was at one end of its horseshoe orbit and, being at its closest to the Earth, was bright enough to be detected in an automated sky survey.
Detailed observations of its trajectory through space show that 2002 AA29 will reach its minimum close approach to the Earth - 12 times the distance between Earth and the Moon - at 1900 GMT on 8 January 2003.
Cat-and-mouse game
Thereafter it will travel ahead of the Earth moving faster than our planet does, until after 95 years it will catch up with the other side of the Earth and then reverse its motion.
Analysis of 2002 AA29's motions have revealed a remarkable event that happens to it every few thousand years.
In 550AD, and again in 2600AD and 3880AD, for a while it will become a true satellite of our planet, in effect Earth's second moon, although technically it will remain under the gravitational control of the Sun.
It remains a second moon to Earth for about 50 years until it escapes.
Although only about 100 metres across 2002 AA29 may play a role in the manned exploration of space out of all proportion to its size.
Already researchers are speculating that it could be visited by an unmanned spaceprobe or even become the first object after the Moon to be stepped on by astronauts.
The object could tell us a lot about the composition of asteroids.
Some have speculated that it could be nudged into a permanent Earth orbit where it could be studied at greater length.
That's what Pete's hoping for. It's just amusing to watch him work.
"Horseshoe" relative to Earth. It's actually always moving the same direction around the sun. Think of the "horseshoe" as an extreme example of Ptolomaic epicycles.
Astronomy Picture of the Day 5-04-02 [3753 Cruithne mentioned in replies]
NASA | 5-04-02 | Robert Nemiroff and Jerry Bonnell
Posted on 05/04/2002 7:26:04 AM PDT by petuniasevan
http://www.freerepublic.com/focus/chat/677904/posts
Cat-And-Mouse Asteroid Pulls Close To Earth [2002 AA29]
IOL | 1-3-2003
Posted on 01/04/2003 10:12:20 AM PST by blam
http://www.freerepublic.com/focus/f-news/816864/posts
Odd Asteroid [2003 GQ22]
spaceweather.com | april-15-2003 | spaceweather.com
Posted on 04/15/2003 2:06:02 PM PDT by green team 1999
http://www.freerepublic.com/focus/f-news/893881/posts
Say hello to our new moon [2003 YN17]
AFP | Fri Mar 26, 2004
Posted on 03/29/2004 12:13:58 PM PST by presidio9
http://www.freerepublic.com/focus/f-news/1107346/posts
page about 2003 CP20, which isn't currently a moon, but co-orbital:
http:.com//www.hohmanntransfer.com/cgi-bin/get.cgi?des=2003cp20
Dated: 25 July 2004
Disc: 3 Aug. 2000 at LINEAR, New Mexico, MPEC 2000-P32
http://www.hohmanntransfer.com/cat/an4.htm#an54509
2000 PH5 was discovered by MIT's LINEAR program on 3 Aug. 2000. It is estimated from its brightness to be about 110 meters/yards across, and is described by Ondrejov Observatory's NEO program as a "superfast rotator." Radar observations were reported 27-28 July 2001 from Goldstone at 5.3 lunar distances (LD) in the midst of a Spaceguard observing campaign. It flew over (north of) Earth on 25 July 2002 at about 4.7 LD.
Paul Wiegert reported in 2001 that he and his co-authors on 3753 Cruithne research will be showing that, like Cruithne, PH5 appears to be locked into an orbital resonance with the Earth.
Earth coorbital asteroid 2002 AA29
Martin Connors, Paul Chodas, Seppo Mikkola,
Paul Wiegert, Christian Veillet, Kimmo Innanen
September 2002
http://www.astro.uwo.ca/~wiegert/AA29/AA29.html
An international team of astronomers has found that an asteroid discovered earlier this year follows Earth's orbit around the Sun and will, in nearly 600 years, appear to orbit the Earth. In the October issue of the journal Meteoritics and Planetary Science, the astronomers announce that the asteroid, named 2002 AA29, follows a "horseshoe orbit" that makes it come near the Earth every 95 years. It will next come close on January 8, 2003, although even then it will be much further away than the Moon and only detectable using large telescopes. The combination of Earth's and Sun's gravity works so that even as Earth pulls in the asteroid, it speeds up and moves away from the Earth. In this way Earth is protected from impact, despite the similarity of the asteroid's orbit to Earth's.
The ESA Venus spacecraft is due to go into planetary orbit on 11 April. NASA has one on the way to Mercury, which will take several years to get there, and the Mars probe just launched is looking good. Amazing that nothing is going to the moon.
Nothing *yet*. :')
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