Sidereal Motion

By Phil Plait | February 25, 2011 6:56 am

A few days ago I posted a video by José Francisco Salgado showing the sky over telescopes in Chile.

He’s just put up another one, this time showing the motion of the sky over several observatories: "Sidereal Motion".

Sidereal motion is literally the movement of the stars; the apparent rising and setting caused by the rotation of the Earth. You don’t notice it second-by-second as you watch the sky, but over minutes and hours the inevitability of our planet’s angular momentum makes itself known.

José also has breathtaking images of observatories as well as a website linking to his work. He has an artist’s eye for the heavens, and his creations are truly lovely.


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CATEGORIZED UNDER: Astronomy, Cool stuff

Comments (19)

  1. Mike Dwyer

    Thanks for using Vimeo to host the video this time. The hive overmind doesn’t let us in to YouTube while on the clock.

    Was that Kitt Peak near Tucon? Love that place. We take a bicycle ride up there every Summer Solstice. Two hours up and 15 minutes down. We always have to buy a shirt so we don’t get too cold on the way down.

  2. Murff

    I wish we could see the Milky Way clearly during the daytime, it’s an awesome sight!

  3. literally the movement of the stars

    Ooh, nice usage – a case where what something is literally, is different from what it is actually. Well played.

  4. I wonder what the effect on our various cultures would be if the earth spun a little faster? I wonder if the faster movement of the stars would convey a different sense of motion? Might people have reasoned that it was our planet spinning and not the vault of heaven more quickly and with less fuss?

    In any case, I always love those shots showing the Milky Way arcing overhead. And the one with the two Megellanic Clouds was neat.

  5. Pete Jackson

    If astronomy had developed first in the southern hemisphere instead of in Europe and the United States, there would never have been a controversy about where the center of the Milky Way galaxy lies. In the southern sky, you can see clearly how the Milky Way looks like an edge-on spiral galaxy with dark dust clouds running through the middle of the Milky Way disk, and the nuclear bulge in Sagittarius.

  6. Carey

    “And a cast of billions of stars”

    That line at the end made me laugh :)

  7. Adam

    Great video! What is the astronomical object shown in the intro. I don’t recognize it. Thenagain, I don’t always wear my H-alpha glasses.

  8. Ross

    That was incredible!

  9. Amazing video! But, the title says this is a trailer. I want to see the full one :)

  10. WOW! I help write the My Wonderful World blog for National Geographic and we just posted a blog about the GLOBE at Night program to raise awareness about light pollution. I am so impressed that we can now see the stars actually move across the sky. Amazing! Thanks for posting this and feel free to check out the blog for more information on the GLOBE program.

  11. @ Adam:

    I’m not certain, obviously, but I think that intro is a composite at least partially made up of a close view of M16, the Eagle Nebula in Serpens.

  12. Sean H.

    I really wish I could get to the southern hemisphere sometime to see the Large and Small Magellanic Clouds. One of these days perhaps. Lovely images.

  13. Messier Tidy Upper

    Magnificent videoclip. Beautiful. :-)

    @4. kuhnigget :

    I wonder what the effect on our various cultures would be if the earth spun a little faster? I wonder if the faster movement of the stars would convey a different sense of motion? Might people have reasoned that it was our planet spinning and not the vault of heaven more quickly and with less fuss?

    Interesting idea. It’d certainly make taking photos of star trails much quicker and easier! ;-)

    It’d probably moderate our climate too – less hours of heat and cold building up, though it may mean stronger winds and currents perhaps?

    I think our planet’s rate of roatation has slowed and was once much faster -especially before the Moon was formed. Eventually, in the far distant future, our Earth will be tidally locked with the Moon as the Moon already is for us. One side of our globe will forever be without Moonlight – the other will always have the Moon in its sky. H.G. Well’s Time Machine novel noted that if memory serves.

    Not sure if our planet will get tidally locked with the Sun as well but that may be the case too.

    Finally, it is an odd co-incidence that Earth and Mars both have days of around 24-25 hours.

  14. Kris

    At 1:16 – 1:21 you can see two nebulae on the left. Are these Magellanic Clouds?

  15. @ Kris #15:

    Yes. Nifty, huh?

  16. Paul A.

    I have found a way to see the stars move at night. I look up through a tree at the stars and pick a star that is very close to a leaf or branch and then hold my head very still. Then I can watch as the star disappears. I also like to watch the trailing edge of the moon disappear behind straight objects like the edge of a building or through a window.

  17. «bønez_brigade»

    Kitt Peak, huzzah!

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