Forgot your password?
typodupeerror
Space NASA Science

STEREO Spacecraft To Explore Earth's L4 and L5 66

Posted by kdawson
from the home-home-on-lagrange dept.
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."
This discussion has been archived. No new comments can be posted.

STEREO Spacecraft To Explore Earth's L4 and L5

Comments Filter:
  • May hold? (Score:2, Interesting)

    by palindrome (34830)

    '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?

    • Re: (Score:3, Informative)

      by aicrules (819392)
      Possibly, but the solar storm monitoring wouldn't be as effective.
    • Re:May hold? (Score:5, Informative)

      by Bakkster (1529253) <Bakkster.manNO@SPAMgmail.com> on Friday April 10, 2009 @08:30AM (#27530415)

      Since the L4 and L5 points don't move relative to our perspective, any objects we would see there would move very little compared to the background of stars. Movement across a series of telescope images is the usual method for detecting small objects in our solar system, and it can't be used for these locations.

      To detect objects here, you would need to look at images taken over a series of months and centered on the points to find objects that didn't move with the rest of our perspective. This would probably need to be done by a space telescope, since by the time a ground based telescope could see the points, the sun is already rising or still setting. Even then, the objects are only half lit by the sun, due to our angle of viewing, so they would be especially dim. In addition, sending a spacecraft to the area would allow the sattelites to determine the composition of the asteroids to see if they came from an Earth collision or are leftover from the solar system's birth.

      • Re:May hold? (Score:4, Informative)

        by Hynee (774168) on Friday April 10, 2009 @08:41AM (#27530589) Homepage

        Since the L4 and L5 points don't move relative to our perspective, any objects we would see there would move very little compared to the background of stars.

        They'd move as fast as the sun does through the background stars, for obvious reasons! That's ~1 deg/day.

        • Re:May hold? (Score:4, Insightful)

          by Hynee (774168) on Friday April 10, 2009 @09:12AM (#27530999) Homepage
          OK, I'll continue.

          To detect objects here, you would need to look at images taken over a series of months and centered on the points to find objects that didn't move with the rest of our perspective.

          Months would do it, so too would hours! 2.5 min / hour.

          This would probably need to be done by a space telescope, since by the time a ground based telescope could see the points, the sun is already rising or still setting.

          They would set and rise at most 4 hours after the sun, plenty of time for 1x 1 hour exposure a day.

          Even then, the objects are only half lit by the sun, due to our angle of viewing, so they would be especially dim.

          Half-lit by the sun is no problem, this would only give them +0.75 Magnitudes (dimmer by a factor of 2).

          In addition, sending a spacecraft to the area would allow the sattelites to determine the composition of the asteroids to see if they came from an Earth collision or are leftover from the solar system's birth.

          You can still get composition information from asteroid spectra, they can put them into groups of composition types from that. If the spectra hasn't been observed before, it's best to have a sample.



          I don't know what the problem with observing these points is, maybe the asteroids are likely too small.

          • by Bakkster (1529253)
            Yeah, I guess it's not quite as difficult as I thought. My additional guess would be that size and distance considerations makes it difficult enough that nobody has put quite enough effort into it. If the region of asteroids is large, it might be difficult to balance looking at a large enough area while still being able to see small objects. If STEREO does see something, it'll likely be small.
      • Re: (Score:3, Informative)

        by AaxelB (1034884)
        If I may add, the two points are also really far away. I thought they were somewere within the orbit of the moon, but they're actually just as far away as the sun. (This picture [wikipedia.org] cleared things up nicely.) We could probably tell whether asteroids are there, but for the reasons you mentioned we couldn't find out anything more useful.
        • by dwye (1127395)
          Actually, it depends on which L4 and L5 one writes. The O'Neill space colonies were going to be at the Earth-Moon L4 and L5 points, whereas this is looking at the Sun-Earth ones, the equivalent of Jupiter's Trojans, about 93 million miles away (about 150 million km, according to unix's units prgm).

          So you were right and wrong at the same time.

  • Loiter? (Score:5, Funny)

    by PinkyDead (862370) on Friday April 10, 2009 @07:55AM (#27530121) Journal

    Get off my Lagrangian points you young hoodlums!

  • by Nick Fel (1320709) on Friday April 10, 2009 @08:02AM (#27530159)
    If its out there, the atheist community isn't going to be happy.
    • On the contrary, it would simply provide evidence to back up a simple, intentionally ludicrous, hypothesis. Now, if they find God up there. . . I know, I know, WHOOOOOOSH. . .
  • by sprior (249994) on Friday April 10, 2009 @08:04AM (#27530177) Homepage

    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"...

  • AFAIK, Lagrange points are points of -unstable- balance, that is any object placed there that has even minimal speed will proceed to move out and gain speed doing so; only maneuver thrusters would allow a satellite to "linger" there pushing it back when it slips out, and I wonder what cosmic odds would it take for a passing meteor to -stop- there, as in, hit a meteor with exactly the same momentum coming from opposite side at exactly that location...

    • by Anonymous Coward on Friday April 10, 2009 @08:14AM (#27530243)

      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.

      • by kmac06 (608921)
        Actually L4 and L5 are local potential maxima (in a rotating reference frame, maybe? It's been a while since I took mechanics), but orbits around these points are kept stable by some combination of the Coriolis force and gravity.
    • Re:I wonder, how. (Score:5, Informative)

      by hcpxvi (773888) on Friday April 10, 2009 @08:15AM (#27530249)
      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.
    • Re: (Score:2, Informative)

      by fredrik70 (161208)

      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 se

    • IANAAP but I think that is only true for L1-L3. IIRC L4 and L5 would be relatively stable as long as a body had the correct momentum when it entered them.
  • "The asteroids themselves could well be left-over from the formation of the solar system."

    No way. The Lagrange points are theoretical solutions to the 3 body problem. The Earth-Sun system is not 3 body. The Earth's relationship with the moon is such that their common center is outside the Earth. Fluctuations in the gravity field of the co-orbiting the Earth-moon would guarantee no permanently stable solution.

    The L4 and L5 points are not gravity wells. They are the tops of gravity hills (see the top map at h [wikipedia.org]

    • by kill-1 (36256)

      First of all, the Lagrange points are only the solution of a special case of the three body problem (m3 is negligibly small). Then, L4 and L5 actually are stable. The arrows in the Wikipedia article "indicate the gradients of increasing potential". Note the word "increasing".

    • by AikonMGB (1013995) on Friday April 10, 2009 @09:52AM (#27531681) Homepage

      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 [wikipedia.org].

      -Aikon

  • When I read the headline I thought if this worked out that there might be help for my L4 and L5 back problems.
    • The earth is getting pretty old, even if you believe the Christians (what do they think, 6000 years?). I'd say it needs some lumbar support by now.

  • by Anonymous Coward

    In space, no one can hear your STEREO

  • The team is inviting the public to participate in the search by viewing the data and filing a report at: >

    There's a missing link in the article for where you can help out. The link meant to posted is:

  • The new STEREO spacecraft is an improved version of MONO. The next spacecraft, scheduled to be released in 10 years, will be called SURROUND.

    Sorry, I'll be here all week.

  • "These places may hold small asteroids, which could be leftovers from a Mars-sized planet that formed billions of years ago"


    So... Mars?
  • by ghostlibrary (450718) on Friday April 10, 2009 @09:42AM (#27531517) Homepage Journal

    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 [scientificblogging.com]

    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.

  • La Grange? (Score:2, Funny)

    by Ranhert (877588)

    I finally figured out what ZZ Top was singing about. Earth's and the Sun's gravitational limbo land.

  • These places may hold small asteroids

    which will turn the STEREO spacecraft into interplanetary techno-confetti upon impact.

  • "These places may hold small asteroids..."

    Really? We don't KNOW?

    Checking wiki, apparently we're not even sure of what's in the L4/L5s in the Earth/Moon system. A Japanese probe failed to find the expected Kordylewski clouds.

    I'm well aware of the vasty nature of space, but I guess I'm sometimes startled about how ignorant we are about our own very local neighborhood...

    • by RoboRay (735839)

      Considering that the L4 & L5 points are 60 degrees around our orbit of the sun, I wouldn't call it "our own very local neighborhood." They're as far away from earth as the sun.

      • by RoboRay (735839)

        Oh, I missed that you were referring to the lunar Lagrange points, rather than the Earth's (as discussed in the article. Never mind.

  • Powered by THX Dolby Surround Sound.
  • "which could be leftovers from a Mars-sized planet that formed billions of years ago"

    I wonder which planet that could be!

  • It's full of stars!

  • Who knows, maybe they'll see our Antichthon [imdb.com]!
  • Does anyone remember Independence War and Independence War 2? The first one is almost 11 years old and the second is almost 8 years old. They used Lagrange points for a type of FTL travel. It was a cool game and being I was still in high school, I didn't know much about that level of astrophysics.

Somebody ought to cross ball point pens with coat hangers so that the pens will multiply instead of disappear.

Working...