Sic Transit, Glorious

By Phil Plait | June 6, 2012 10:44 am

This is what I’ve been waiting for: the stunning video views of NASA’s Solar Dynamics Observatory of the Venus transit. Sit down, set this video to high-def, tune out everything else for 3 minutes 7 seconds, and soak in the clockwork glory of our solar system.

OK, you can breathe now. NASA has provided high-resolution versions for download, too.

SDO orbits the Earth about 40,000 kilometers (24,000 miles) above the surface of the Earth, with a nearly-continuous view of the Sun — so it had the best seat in the Universe for the transit. One of its most important tasks is to observe the Sun in ultraviolet, where our star’s magnetic activity is most obvious. The views in the video show the Sun different parts of the ultraviolet spectrum, colored to make them easier to see: magenta is at 1700 Angstroms (a unit of length astronomers like; 100 million Angstroms would comfortably fit across your fingernail), red is 304 Angstroms, and gold is 171 Angstroms. The orange segment is from the light we can see, about 3000 – 7000 Angstroms.

The Sun’s ethereal outer atmosphere, its corona, glows at at 171 and 304 Angstroms. In visible light the transit lasted about 7 hours, but in the UV it took longer since the silhouette of Venus can be seen against the softly luminous corona.

SDO was commanded to take images faster than usual, to provide as much coverage of the transit as possible, so the passage of the planet across the Sun is smooth and — I know, but it fits — other-worldly.

And I can’t help but think about a sad milestone today: one of America’s — one of the world’s — greatest writers, Ray Bradbury, has died. Among his many works was "The Long Rain", a short story which took place on Venus. It had a huge impact on me when I first read it as a kid, and it still makes me think about human nature, space exploration, and what happens when we mix the two.

Bradbury was more than a writer, he was a poet, and his works inspired generations of people to look beyond the borders of our world while still considering our humanity. We all must go someday, and for him to do so on the eve of the last transit of Venus to be seen for over a century is, somehow, fitting.

Ray Bradbury knew that no matter where we are, whether we are looking down into the water of another world, or looking up into the skies, what we are always seeing is a reflection of ourselves.

Sic transit gloria mundi.

Credit: NASA/SDO

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (29)

  1. josie

    The transit was great here in San Diego! Glorious sunny skies and my my work is on a coastal bluff so it was a good view. I got to show a few of my workmates through my filter fitted binoculars. Of course I also got a few questioning looks :)

    I read the long rain story “All Summer in a Day” when I was a kid; before I knew how to pronounce ‘Margot’. I like the name a lot better now, it sounds more feminine in my head.

  2. Mike

    There’s something interesting happening around the 2:15-2:20 point near the middle of the sun’s disk. There’s a bright spot that moves “north northeast”ward. Is it a comet? Is it a rapidly moving feature of the prominence that’s in that area?

  3. Rapha

    Phil, could you explain why the edge of the Sun’s disk is appearing inside the disk of Venus, as the planet is traveling through the edge of the Sun?
    It’s visible quite clearly at the 0:30-35 point roughly.
    I would have expected Venus to block off the Sun’s light completely, but instead we can see the arc made by the overlapping of the two disks.
    Diffraction would not produce a pattern of this kind, so what does?

  4. Pete Jackson

    @Rapha: Perhaps it’s a memory effect on the detector that they are using, much like a TV screen can retain a memory of an image that it has displayed for a long time. Or perhaps, it’s in your eye (or brain), which also retains a memory. Try freezing the frame between 0:30 and 0:35 to see if it is still there.

  5. Doug McLachlan

    Hi Phil, great coverage on the site. Thanks. Agree that it was somehow fitting that Ray Bradbury’s passing was poignantly timed.

    I did have a question that might speak to both transits and Bradbury’s hope for human exploration.

    There won’t be another transit of Venus seen from Earth for over a century but when would we be able to witness the next transit of Venus from the other locations? (I was initially thinking Mars but am open to other interesting suggestions too.) What about the next transit of the Earth as seen from Mars?

    Countless ordinary (well, actually, commonly extraordinary) people make travel plans to watch solar eclipses from locations all over the world that used to be the exclusive domain of grand scientific expeditions. Will my daughter, aged 7, and son, aged 2, have a chance to watch Earth transit the sun from Mars during their lifetime?

  6. JeremyH

    That video once again proves, to my eye, that the Venus transit isn’t half as interesting as the sun itself. A black dot moving across the sun’s disc doesn’t amount to much outside its historical importance, whereas the sunspot and flare activity, the cell motion, and damned near everything else going on on the sun (especially in some of those filters) are absolutely fascinating.

  7. David Weingart

    Given the weather we had here on Long Island, NY, I was VERY grateful for last night’s online coverage and stayed up WAY past my bedtime to watch it until the very end.

    This is beautiful stuff.

  8. Joe

    Hey Phil – I always thought that the outer edges of the Sun was mostly uniform with random solar flares etc. But looking at that video there is a huge area towards the centre that is a very different colour than the rest for the entire transit of Venus. Is this just because of the angle of the camera, a flare, or is there always areas that are like this? If so, what causes them?

  9. Pete Jackson

    @Doug: According to Wikipedia, a transit of Earth and Moon across the sun will be visible from Mars in 2084. A bit out of the way, but there’s a lot of time to plan the trip! On the other hand, the prospects of good weather are excellent!

    If you’re really patient, a transit of both Earth and Venus across the sun will be visible at the same time in the year 571,471.

  10. HvP

    Rapha and Pete Jackson,

    I noticed the same thing. At first I thought it might be an optical illusion so I cut a hole in a small card and held it up to the screen to block out the Sun so I was only seeing the middle of Venus. The curve of the Sun still seems to be visible as an after image in the video.

    I doubt it would be due to a lingering afterimage in the camera sensor because although this appears to be full motion video it is actually a collection of many stills taken over a period of six hours. The effect is also plainly visible in a photo collage on the NASA site listed as “Sequence of images of 171 transit composited together to show path of Venus.”

    The curve seen in the middle of Venus seems to too perfectly match the limb that would be behind Venus for it to simply be an atmospheric refraction. I’m very curious about this myself. My best guess is that it is some sort of error in contrast adjustment in processing the image – with areas neighboring a dark background being lightened and areas neighboring a bright background being darkened to improve the contrast of the object.

    Or it may also be likely that sequence was motion tracked onto a still of the whole Sun as a background layer. This is a common technique used to line up overlapping frames so that the background elements don’t appear to jitter around the frame across many shots. It may be that some transparency was left on the top layers by mistake.

  11. Rapha

    @Pete: simply hit pause and you’ll see the Sun’s disk is still quite visible inside Venus’.
    @HvP thanks for your thoughts, like you I’m still waiting for a better explanation.
    It has to be a fairly straightforward one!

  12. HvP

    I’m waiting for the conspiracy theorists to claim that all the photos of the (supposed) transit were (poorly) faked by NASA and the international cabal of scientists – despite the many thousands of amateurs who witnessed this with simple homemade tools.

  13. Doug McLachlan


    Thanks. 2084 seems a very reasonable time to shoot for. My daughter will be a spry 79 year-old and my son will only be 74. I understand that we should be able to book them good seats for the trip with this much advance notice. Wonder what the luggage fees would be :-)

  14. Alph

    Nice video. In one part of the video, Venus transits the sun and appears at a fairly high latitude. I just sort of assumed that all planets circled the sun at it’s equator. Was that just an illusion of the telescope, or do planets not circle at the same plane?


  15. Rich W

    I always thought that the Earth and Venus on the same plane around the sun. But all of the transit images make it look like that’s not so. So, either they are in the same plane but something else is causing it to appear that they are not, or they aren’t in the same plane. Which is it? And if it’s the former, can someone point me to a website to explain the effect?

  16. Rick White

    @Alph and @Rich W;
    Venus’ orbit is offset from the earth’s orbit by 3 degrees if I remember correctly. That’s why we don’t get transits of Venus more often.

    I was thinking the same thing. UFOlogist idiots will see that and make up all sorts of fun “explanations”.

  17. Chris

    @15 and 16

    The planets don’t all orbit in the same plane. They are really close, but those few degrees are why we don’t have transits of Venus every other year. This is called the orbital inclination
    Only when both planets intercept the node will we have a transit. There is a little wiggle room because of the finite size of the sun and that’s why Venus doesn’t go straight across the middle of the sun.

    There is also the secondary effect of the observer’s latitude will cause the location of Venus to shift slightly. This is a parallax effect and how they determined the size of the Earth’s orbit all those years ago.

  18. John H

    @Doug & @Pete

    There was a transit of Earth visible from Mars on May 11, 1984. Arthur C. Clarke wrote a science fiction short story ( “Transit of Earth” ) in 1970 about an astronaut stranded on Mars observing this event.

  19. Matt B.

    The part at 2:00 where it changes filters gives me an idea: I’d like to see a video of the Sun that (as nearly as possible) continuously changes the wavelength of light that’s being viewed.

    In reference to Ray Bradbury, we can also use the Babylon 5 episode title “Sic Transit Vir”.

  20. Clint L

    Is it a trick of the brain/eye or real? In watching the video several times, I perceive a change in the vision of the parts of the sun past which Venus transits. It is like looking through heat haze at a distant object. A bit weird considering the heat in the distant object, but that is the effect I’m getting, a slight disturbance in the vision.
    It is like Venus has more than an atmosphere but something further out so it not only appears to leave a trail of disturbance but also pushes an envelope of disturbance.

    Or it is just my brain making up stuff from too many views of the video?

    Anyone else getting that?

  21. Paul

    The ghost effects inside the circle of Venus could be video compression artifacts.

  22. Don Gisselbeck

    It was cloudy and rainy in Missoula, Montana, but a few of us from the Missoula City Band played Sousa’s Transit of Venus March during the transit.

  23. Paul

    I was able to bring my telescope to my High School and have it set up in time for the transit to start 5 min after school ended. The skies had been overcast all day but the clouds broke about 30 min before things started and we had great visibility right through til the sun set. About 50 students and staff had the curiosity to come check it out during the 45 minutes I stayed at school and then another dozen or so neighbors when I set up again at home. It was fun to share the event with others.

  24. mike burkhart

    That was grate!

  25. John

    Great music with the video–who did it?

  26. Andrew

    A great video – I missed the whole event in the UK due to cloud at 5am! – but like some people who have commented earlier I can see what appears to be the limb of the Sun “inside” Venus between first and second contact. Some kind of video artefact, perhaps?

  27. #15 Alph, #16 Rich W:
    The orbits of Venus and Earth are inclined at 3.4 degrees to each other. If they were in the same plane, we would see a transit of Venus at every inferior conjunction, i.e. every 583.9 days! Because of this inclination, at most inferior conjunctions, Venus passes slightly above or below the Sun; a transit only occurs when a conjunction coincides with one of the nodes, the two points where the orbital planes intersect. In fact, it can be a little way off from the node to either side, due to the big apparent size of the Sun, which is why we don’t see it cross the centre of the Sun.
    It’s the same as why we don’t get a solar eclipse every month – because the Moon’s orbit is also inclined to that of the Earth.
    The time between successive inferior conjunctions of Venus, called the synodic period, is 583.9 days. 5 synodic periods is very nearly – but not quite – equal to 8 Earth years and 13 Venus years; so every 8 years ( 8 years minus 2.5 days, to be exact ), a conjunction occurs at very nearly the same place in the orbits. This explains why transits occur in pairs 8 years apart; the shift in position after 8 years is small enough that the conjunction again occurs close enough to the node for a transit to occur, but then after another 8 years, it’s just too far away from the node.
    Hope that helps.


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