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STEREO Spacecraft To Explore Earth's L4 and L5
Hugh Pickens writes "Launched on October 25, 2006, NASA's twin Solar Terrestrial Relations Observatory (STEREO) spacecraft are about to enter the L4 and L5 Lagrangian points, special points in our orbit around which spacecraft and other objects can loiter because the gravitational pull of earth and the sun balances the forces from the object's orbital motion. (The spacecraft won't linger at the Lagrangian points; they are just passing through.) 'These places may hold small asteroids, which could be leftovers from a Mars-sized planet that formed billions of years ago,' said NASA Project Scientist Michael Kaiser. STEREO will look for asteroids with a wide-field-of-view telescope. 'If we discover the asteroids have the same composition as the Earth and moon, it will support Belbruno and Gott's version of the giant impact theory. The asteroids themselves could well be left-over from the formation of the solar system.' L4 and L5 are also good places to observe space weather. 'With both the sun and Earth in view, we could track solar storms and watch them evolve as they move toward Earth. Also, since we could see sides of the sun not visible from Earth, we would have a few days warning before stormy regions on the solar surface rotate to become directed at Earth,' says Kaiser."
'These places may hold small asteroids, which could be leftovers from a Mars-sized planet that formed billions of years ago,'
Can we not confirm the existence of these using telescopes on Earth or in orbit?
Get off my Lagrangian points you young hoodlums!
Genesis 1:32 And God typed
If its out there, the atheist community isn't going to be happy.
So your telling me that NASA is parking the worlds most expensive STEREO in the only free parking spots in the solar system? Next you're gonna tell me they used it to blast "In your eyes"...
L4 and L5 are stable, means that a force pushes objects back in the direction of those points regardless of the direction, because they are a local potential minimum.
L1, L2, L3 are indeed unstable, but there exists an orbit around those points, which is stable.
That (the lagrange points being unstable equilibria) is true of L1, L2 and L3 (all on the Earth-Sun line, L1 between Earth and Sun, L2 outside the Earth's orbit and L3 round the other side of the Sun). L4 and L5, OTOH, are stable equilibria and junk can collect there. The equivalent points for Jupiter have observable collections of asteroids in them.
actually 4 and 5 are stable, from wikipedia:
In contrast to the collinear Lagrangian points, the triangular points (L4 and L5) are stable equilibria (cf. attractor), provided that the ratio of M1/M2 is greater than 24.96.[5][6] This is the case for the Sunâ"Earth and, by a smaller margin, the Earthâ"Moon systems. When a body at these points is perturbed, it moves away from the point, but the Coriolis effect bends the object's path into a stable, kidney beanâshaped orbit around the point (as seen in the rotating frame of reference). However, in the Earthâ"Moon case, the problem of stability is greatly complicated by the appreciable solar gravitational influence.[7]
source
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utter rubbish, in an informal environment like this wikipedia is fine. Indeed you should not use it in papers and such, that' splain silly, but for a quick lookup of fact, together with a quick check if the content seems unreasonable or not, it's fine
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In space, no one can hear your STEREO
As a researching using STEREO data, I wrote a piece on some of the logistics of this, and what we may find.
http://scientificblogging.com/daytime_astronomer/secrets_l4l5_gravity_wells
The summary is: we've already seen a bit in an earlier roll so we know there's stuff there, we lose use of the in-situ to explore L4/L5 so we have to balance that with our core science, there's a higher risk to the detectors due to dust, but what the heck, we have to pass through it anyway. We may find any of: dust, the moon's progenitor, and earth-killer, more dust.
A.
I finally figured out what ZZ Top was singing about. Earth's and the Sun's gravitational limbo land.
First: The Earth's relationship with the Moon is such that their barycentre is inside the Earth, about 1700 km below the surface.
Second: L4 and L5 are potential minima, meaning the gravitational potential field increases as you move away from these points. Although the term "well" is misleading, it is certainly more applicable than "hill". It is this increasing potential that leads to the Lyapunov stability of L4 and L5 in the restricted three-body problem. The definition of this kind of stability is that if you are perturbed from equilibrium some small delta less than epsilon, then you will stay within that epsilon band.
Third: The Earth-Sun Lagrange points currently occupied by satellites are L1 and L2, for perpetual sunlight and perpetual shadow respectively. L1, L2, and L3 are all unstable, hence the necessity for station-keeping of these satellites. As far as I am aware, there are no satellites currently occupying L4 or L5.
Fourth: Large Impact Theory is just that, a theory. One of the objectives of this mission is to determine if there are small asteroids at L4 and/or L5, which could either lend support to or detract support from this theory. Regardless of whether this event happened or not, the L4 and L5 points still exist for any restricted three-body problem. Case in point: Jupiter-Sun L4 and L5 are filled with the Trojan asteroids.
-Aikon