Solar eclipse, from space!

By Phil Plait | October 19, 2010 7:00 am

For their Picture of the Week last, uh, week, the Solar Dynamics Observatory crew chose a fantastically cool shot: the Moon cutting across the disk of the Sun!


Wow! This phenomenal shot was taken on October 7, 2010, as the new Moon slipped between the Sun and the observatory. SDO is in Earth orbit, circling our planet 36,000 km (22,000 miles) up (technically, that’s the distance from the Earth’s center). The orbit is tilted so the Earth itself only rarely gets in the observatory’s way as it watches the Sun day in and day out.

But every now again, when the celestial objects literally align, the Moon can block the view. From the Earth, the Moon was new, meaning it was near the Sun but not blocking it. But from SDO’s point of view the geometry was just right to get this partial eclipse (technically called a transit). I drew a rough diagram to give you an idea of how this worked:


This isn’t to scale, but should help. You can see SDO and its tilted orbit (seen edge-on, so it looks like a line), allowing it to view the Sun without the Earth’s big face getting in the way (from SDO’s point of the view, the Earth is about 25° across, the apparent size of a dinner plate held at arm’s length). The Moon’s orbit is tilted as well, and in this case, it happened to be in the way of SDO’s line of sight to the Sun.

The shot itself is amazing. It’s false color: the camera was actually viewing the Sun in the far ultraviolet, where the solar magnetic field’s churning turmoil can be seen plainly. You can see gigantic loops of hot plasma arcing up over the surface of the Sun and then plunging back down. On the left is a spectacular example of that… mind you, the Sun’s disk is about 1.4 million km across — 860,000 miles. That loop is well over 200,000 km (120,000 miles) high! The Earth would be a dot compared to that.

When the Sun does something, it does it big.

If you want to see more pictures like this, put the SDO Picture of the Week RSS feed into your reader. I already have, and when another amazing shot like this pops up, you can bet I’ll write about it.

Tip o’ the X-ray specs to Lights in the Dark.

Related posts:

What does a lunar eclipse look like from the Moon?
STEREO eclipse

MORE ABOUT: eclipse, Moon, SDO, Sun, transit

Comments (35)

  1. MHS

    Also note the relief on the Moon’s edge! Awesome photo.

  2. Oli

    @1. MHS: I don’t see any relief…

  3. MHS

    @2. Oli: You can see mountains on the south side (assuming north is up), if you embigenate :)

  4. Zucchi

    These wonderful pictures are always bittersweet for me. Forty years ago I was convinced that by the 21st century, human presence would be all over the Earth-Moon system, and planning for Mars and beyond.

  5. Jason

    This is a very cool picture. I would love to see them get a Total eclipse image.

  6. @Oli: I futzed with the original image levels and sharpening (and flipped it) to bring out some detail in the moon’s limb on my post here. The image will link to my Flickr page where there’s a bigger pixel view too.

    Almost fell off my seat when I saw this (and the SDO video!)

    Love the diagram Phil….looks like something that could get one burned at a stake in the 1500s. 😛

  7. Oli

    @3. and 6.: Orite. I’d only looked at this smaller version when I made the comment 😉

  8. I’m with you, Jason! We want to see totality!
    (Never satisfied with merely awesome, we shoot for Hawesome!)

  9. blf

    Awesome pic – it’s now my desktop background.

  10. Messier Tidy Upper

    Excellent image. Thanks Solar Dynamics Observatory folks & the BA. :-)

    It still strikes me as one of the more amazing cosmic co-incidences – and we are exceedingly fortunate – that the Moon and our Sun have the same apparent diameter as viewed from the surface of the Earth. And it seems from Near-Earth Orbit’s like the SDO’s. 😉

    Almost certainly, our Earth is NOT unique in the universe. There are likely many Earth-like worlds although of course most probably won’t have intelligent, technological life. (After all in all Earth’s 4.5 billion years of existence we’re the only ones we know of and we’ve only been around for about 2 million years and technologically advanced for the past 2 centuries or so.)

    However, there’s a very good chance ,methinks that Earth-like planets having moon(s) like Moon will be staggeringly rare. Which means eclipses like ours will be phenomenally, astronomically, rare.

    Perhaps even so rare we are the only one’s in the Milky Way to see such pefectly matching eclipses ..? Would anyone who’s good at maths and statistics (which, alas I’m not) care to calcluate the odds and enlighten us further on that, please?


    “The triple triumph of the Moon, then, is that it made it possible for man [sic] to exist; it made it possible for him [sic] to develop mathematics and science, it made it possible for him [sic] to transcend Earth and conquer space.”
    – Page 38, ‘The Tragedy of the Moon’, Isaac Asimov, Mercury Press, 1972.

    “This is surreal, how each grain of moondust falls into place in these little fans, almost like rose petals.”
    – Buzz Aldrin (during his first Moonwalk July 1969), Page 38, ‘Magnificent Desolation’, B. Aldrin, Bloomsbury, 2009.

    “There were no fires in the Martian desert. In fact, of all the worlds in the solar system only Earth with its oxygen-rich atmosphere knew fire.”
    – Page 43,‘Voyage’, Stephen Baxter, Harper-Collins, 1996.

  11. François

    Hey Phil,

    “That loop is well over 200,000 km (120,000 miles) high! The Earth would be a dot compared to that”,

    I think the Earth would be roughly 7 pixels wide at this scale. Crazy uh ?

    Makes me wonder how it can be possible to detect an object that small orbiting around a distant star.

    Thanks again for everything you do here, daily amazingly good job !

  12. NAW

    That is just so cool. And the video they have of it is great.

  13. Zetetic

    @ Zucchi:
    Tell me about it! *sigh*

  14. Grand Lunar

    My new desktop background. :)

  15. AJ in CA

    Wow. Beautiful!! Yet another example of why every single one of my desktop wallpapers comes from this blog 😉

    I’m wondering, is the apparent bumpiness of the limb of the moon actually its topography, or is it a blooming effect caused by variations in brightness on the sun’s disc?
    If those are actual lunar hills, that’s even cooler (if that were at all possible)!

  16. AJ in CA

    Messier Tidy Upper: Regarding the apparent size of the moon and sun – it gets even cooler.
    IIRC, tidal forces are transferring angular momentum from the earth to the moon, slowing down the earth and making the moon recede from the earth at a rate of about one kilometer every 26,000 years or so. So it’s not just that the moon is surprisingly large (large enough to be the right size to occult the sun from our POV,) it’s also the right time in earth’s history. A few hundred million years one way or the other, and the moon would be look a bigger (or smaller) than it does right now :)

  17. Davenmer

    @ #10 — and you think that happened by accident through evolution huh?? because of things like that, creation is so much more easily believed than the evolution theory.

  18. Lucas Costa

    Thank you for the amazing post, Phil.

    Reminded me of Sagan’s famous quote “A religion old or new, that stressed the magnificence of the universe as revealed by modern science, might be able to draw forth reserves of reverence and awe hardly tapped by the conventional faiths.”.

  19. AJ in CA

    @Lucas Costa: I’ve never heard that one, but that’s so true!

    Personally, I’ve recently begun (slowly) learning and practicing Theravada Buddhism. I was raised in a half Jewish, half Christian family, and always disliked the biblical bits that were clearly incompatible with what we’ve learned through science.

    I recently read a book by the Dalai Lama, sort of a beginner’s guide to Buddhism, and one part that stuck with me (apologies, I’m paraphrasing) was that one of the most important pursuits is wisdom, and that “wisdom is attained by carefully observing the world and understanding the causes and effects of phenomena.”
    It was a refreshing change from what I was accustomed to hearing from religious leaders, which was more along the lines of “Just study this one book over and over and eventually God will tell you whatever he thinks you need to know.”

  20. #16 AJ in CA:
    Yes, the bumpiness of the Moon’s limb is indeed its actual topography, seen in profile. This is exactly what causes Baily’s Beads, when we observe a total eclipse from Earth; in the last few seconds before Second Contact, and the first few after Third Contact, we see the thin sliver of sunlight broken up into “beads” by the mountains and valleys on the lunar limb.

  21. AJ in CA

    @Neil Haggath: That is so cool! Ya learn somethin’ new every day 😀 Thanks.

  22. John

    hey, the moon slows and recedes a klick per 26000 years, isn’t that the length of the Mayan calendar, another correlation to the Mayans?


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