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Space EU

Billion Star Surveyor 'Gaia' Lifts Off 77

mrspoonsi writes "BBC Reports: 'Europe has launched the Gaia satellite — one of the most ambitious space missions in history. The 740m-euro (£620m) observatory lifted off from the Sinnamary complex in French Guiana at 06:12 local time (09:12 GMT). Gaia is going to map the precise positions and distances to more than a billion stars. This should give us the first realistic picture of how our Milky Way galaxy is constructed. Gaia's remarkable sensitivity will lead also to the detection of many thousands of previously unseen objects, including new planets and asteroids. Gaia will use this ultra-stable and supersensitive optical equipment to pinpoint its sample of stars with extraordinary confidence. By repeatedly viewing its targets over five years, it should get to know the brightest stars' coordinates down to an error of just seven micro-arcseconds. "This angle is equivalent to the size of a euro coin on the Moon as seen from Earth," explained Prof Alvaro Gimenez, Esa's director of science.'"
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Billion Star Surveyor 'Gaia' Lifts Off

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  • Total map size (Score:5, Interesting)

    by mrspoonsi ( 2955715 ) on Friday December 20, 2013 @05:23AM (#45744039)
    The article states it will map 1% of our Milky Way, and there are 170 billion Galaxies in the universe, so that is: 0.0000000000005% mapping of the known universe (if my figures are correct).
    • Don't forget that every time we try to count them, there turns out to be more than expected.

      While this telescope is focused on high accuracy of closer stars, so it may not be finding any more galaxies, I wouldn't be surprised if it finds even more stars in the Milky Way than we previously estimated. This seems to happen every time we take a closer look.

      From the article

      it is likely also to see a colossal number of objects that have hitherto gone unrecorded - such as comets, asteroids, planets beyond our Solar System, cold dead stars, and even tepid stars that never quite fired into life.

      It seems even the definition of star isn't always clear.

      • Re:Total map size (Score:4, Insightful)

        by FlyHelicopters ( 1540845 ) on Friday December 20, 2013 @08:16AM (#45744539)
        What you say is very true...

        Anyone who doubts this should go to YouTube and search for "Hubble Ultra Deep Field".

        Amazing video...

      • It will find galaxies, sort of. Gaia doesn't really care what it is looking at, it simply tags every point of light in its field that is bright enough. Things that aren't stars are then to be discarded when the data is processed. There was a recent paper published suggesting that some of these discarded galaxies could be surveyed in order to get even more science value out of Gaia.

        • by j-b0y ( 449975 )

          Very little that Gaia observes is truly discarded -- just the main astrometric system needs a mix of stable, well behaved stars and very distant quasars, that could be between 10% and 50% of the objects detected. There will be an attempt to classify objects -- which you need to do in order to grab the quasars for the astrometric system

          • I meant to say some of the data is discarded. The paper I read discussed reconstructing a galaxy images to take into account the information Gaia throws away before downloading it to the ground station.
    • Re:Total map size (Score:5, Informative)

      by wjcofkc ( 964165 ) on Friday December 20, 2013 @08:28AM (#45744593)
      While it is true that we don't know for sure how many galaxies there are in the Universe, 170 billion is likely low balling it a bit too much. The most widely accepted estimate stands at 500 billion - but still, this is murky water. A good article on how that number was arrived at can be found here:

      500 Billion --A Universe of Galaxies: Some Older than Milky Way [dailygalaxy.com]
    • Actually Gaia will map 1% of the stars, but a substantial (my guesstimate ~50%) volume of the region containing most of the stars, which will allow to map the principal structures of the Galaxy: its spiral arms and its stellar bar, as well as to constrain the distribution of dark matter. It is comparable to study one object, like the sun, to better understand all the stars; Gaia will map one galaxy well, ours, with the aim to better understand all spiral galaxies.

  • by yo303 ( 558777 ) on Friday December 20, 2013 @05:23AM (#45744041)

    What is that in Metric? Wait, I mean American?

    • by Anonymous Coward on Friday December 20, 2013 @05:43AM (#45744095)

      What is that in Metric? Wait, I mean American?

      Well, the diameter of a Euro is about 23.25 mm, giving it a surface area of about 425 mm squared. Given the ugly assumption that all 151,785,778 items in the library of congress are A4 sized (total SA ~ 9,466,878,973,860 mm squared), a Euro coin is about 4.5x10-11 of a Library of Congress.

      I should probably do some work.

    • by idji ( 984038 ) on Friday December 20, 2013 @05:44AM (#45744097)
      This is a EUROPEAN satellite, and so a EURO is very appropriate.
      Yes, the Europeans are going back to fundamental mapping of what is out there, like James Cook, Galileo, Johannes Kepler.

      Onwards to L2 Gaia!!!
    • by Teun ( 17872 ) on Friday December 20, 2013 @05:45AM (#45744101) Homepage
      US$ 1.3639
      • by rnturn ( 11092 )

        Well, at least today it is. I prefer my units of measurement to be in wavelengths of an excited atom or, at the very least, the distance between two scratches on a platinum bar.

        (I think the point folks have been trying to make it that it would have been much more informative to say a ``N millimeter'' coin/object/whatever. Much of the world has probably never seen -- or ever will see -- a Euro coin except, maybe, in a photograph.)

    • by Anonymous Coward

      its diameter is .915 inch or 1.16 milli-furlongs :-)

    • by KritonK ( 949258 )

      In Metric, it is 23.25 mm.

      In American, it is 0.95836768342951360263 times the diameter of a quarter. Or, in more standard units, 0.00021188757655293088 football fields. Approximately.

    • Given how close the moon is, this doesn't sound very accurate at all. Luckily, Gaia is still very confident. Good girl.
      • Woa, so you know how to build a sensor that can pinpoint a location at a distance of 384,400 km more precise than +/- 23.25 mm? Color me impressed!
        • by yo303 ( 558777 )

          This being a European project you should be coloured impressed.

          • This being a European project you should be coloured impressed.

            Sure, I shouldn't kulør d'impressed seid?

        • by GauteL ( 29207 )

          I was wondering how impressive it was and attempted to resolve this with trigonometry to find the likely error distance 1 light year away.

          This got me in trouble with precision (the angle is of the order 1.0e-11 in Radians) but knowing that the angle is a constant here, the error should scale linearly with the distance.
          If we use 400,000 km as the distance to the moon, 1 light years is roughly 2.0e7 times the distance to the moon (Google search calculator).

          Thus an error of 20mm = 2.0e-5 km error at 400000 km

          • Hmm, that is impressive. Thanks for doing the math. I was (obviously) going on a gut feeling there :)
      • by Teun ( 17872 )

        Given how close the moon is,

        Now I appreciate the US concept of distance is, especially for those from the mid-west, different to that of someone living in say Luxembourg or Belgium but to call the moon close is a bit of a stretch.
        I mean, even with your low fuel prices such a 480,000 mi round trip might get expensive...

  • ...is whether it can detect Apollo 11 mission stuff on the moon. That would shut a few mouths. The Hubble telescope lacks sufficient resolution in the visible light range.
    • by j-b0y ( 449975 )

      Well, Gaia won't ever observe the Moon, nor Venus and Mercury which are always on the sun-ward side of the solar-shield. Jupiter is so bright that it really messes with the detectors when it transits the focal plane, but it should be possible to do some interesting general-relativity experiments with the light-bending effects of Jupiter's mass for stars that are close (not not too close) to Jupiter when Gaia observes near it.

      • In fact Gaia is sufficiently sensitive that General Relativity light deflection due to the sun and planets must be taken into account in all directions!

  • Excellent! (Score:5, Informative)

    by Hartree ( 191324 ) on Friday December 20, 2013 @10:34AM (#45745295)

    This is a mission I've been watching and waiting for for a while. The original Hipparcos mission did this sort of mapping for a much smaller volume of space.

    Think of this as being like how finding the precise latitude and longitude of a large number of places on earth would have been to navigators of a much earlier era. No big new ideas, but it makes navigating so much easier and precise.

    This does this for astronomy and cosmology in a greatly expanded region of space.

    Something some don't realize is that our measurements of distance to stars and other objects in astronomy are very indirect. We use red shift to measure it in many cases, but that's an indirect method that relies on assumptions and estimates of the Hubble constant.

    We also use what are called "standard candles". These are objects we know the brightness of from the physics of the processes going on. Certain kinds of supernovae are some of the best known. But, again, like measuring the distance to the next town by how bright the streetlights are, it's indirect and can have errors from intervening dust, for example..

    This will use parallax, the same method as used in surveying to find distance from the change in angle between two separated observations of a far object. It's a direct method that relies on few assumptions.

  • Gaia is the first God, the God of all Gods and a women.
    http://en.wikipedia.org/wiki/Gaia_(mythology) [wikipedia.org]

I am more bored than you could ever possibly be. Go back to work.