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posted by CoolHand on Monday June 20 2016, @09:42PM   Printer-friendly
from the better-than-our-pocket-telescope dept.

The James Webb Space Telescope (what could maybe be called a 'better Hubble telescope') is due to be launched in 2018.

Its primary mirror spans 6.5 metres, compared to Hubble's 2.5, giving it seven times more light-gathering power. It will also gather from the infrared spectrum instead of gathering visible light: this will allow it to 'see' past clouds of dust, to gather more information about the beginning of the universe.

It will NOT be fixable like the Hubble, though. It is going to be sitting out at L2 (Lagrange point 2 of the Earth-Sun system) which is 1,500,000 kilometers (930,000 mi) from Earth, directly opposite to the Sun. At this point, with the Earth, moon and sun behind it, the spacecraft can get a clear view of deep space.

Where exactly is L2 for the Earth-Sun system? You can work it out for yourself (

or look at pretty pictures

Why do you have to state 'L2 for the Earth-Sun system'?


In celestial mechanics, the Lagrangian points (/ləˈɡrɑːndʒiən/; also Lagrange points, L-points, or libration points) are positions in an orbital configuration of two large bodies where a small object affected only by gravity can maintain a stable position relative to the two large bodies. The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centripetal force required to orbit with them. There are five such points, labeled L1 to L5, all in the orbital plane of the two large bodies. The first three are on the line connecting the two large bodies and the last two, L4 and L5, each form an equilateral triangle with the two large bodies. The two latter points are stable, which implies that objects can orbit around them in a rotating coordinate system tied to the two large bodies.

ANY 3 body system will have 5 Lagrange points! (I did not know that).

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  • (Score: 3, Informative) by BsAtHome on Monday June 20 2016, @10:34PM

    by BsAtHome (889) on Monday June 20 2016, @10:34PM (#363080)

    Hm, Earth mass 5.9e24 kg, Moon mass 7.3e22 kg, Sun mass 2e30 kg, Telescope mass 1e4 (probably less).

    I guess they have their asses covered on the mass issue by 18 orders of magnitude.

    It would be quite a feat to launch a telescope with a significant mass to change the Lagrange points, considering that the mass has to be subtracted from the Earth's mass. But then again, we could all have some fun when our bellies are not feeling so heavy anymore (please fund the space agencies for a project of that kind).

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  • (Score: 1) by khallow on Monday June 20 2016, @11:01PM

    by khallow (3766) Subscriber Badge on Monday June 20 2016, @11:01PM (#363085) Journal
    Well, given that I just pulled an Earth-massed object out of my ass, we could just launch my ass. For science!
    • (Score: 2) by BsAtHome on Monday June 20 2016, @11:11PM

      by BsAtHome (889) on Monday June 20 2016, @11:11PM (#363087)

      Yes, please. Your volcanic ass is clouding my window. You might also consider temperature control. The glow is not good for my beauty sleep.