Along with the full-disk view of the Sun we will provide several zoomed views. These views are shown by the boxes that are drawn on the image. You can also see that the EUV telescopes will see Mercury blocking the corona before it moves onto the disk. All of the boxes are built in a 16x9 ratio that nicely fits into an 1080p screen.
- The Ingress box will show the images from when Mercury moves over the edge of the Sun at the beginning of the transit. This includes 1st and 2nd contact (when Mercury first touches the edge of the Sun and when Mercury moves completely onto the Sun in visible light.) It will also show Mercury against the corona of the Sun before 1st contact in the EUV channels;
- The Tracking box will follow Mercury as it moves across the disk;
- The Egress box images will show the data when Mercury moves into that box as it exits the Sun. It will not be available until about 1715 UTC. This box will show 3rd and 4th contact (when Mercury starts leaving the disk of the of Sun and the last instant it touches the edge of the Sun, again in visible light);
- The Full Passage box will be updated throughout the transit so that you can watch the entire path of Mercury across the Sun.
Each view is available as a self-updating movie, by clicking on the picture shown on the website, and as an mp4 movie, which can be seen by clicking on the View/Download mp4 button below the image. Depending on its settings, your browser will either show the movie or download it. The mp4 movies will also be regularly updated as new images arrive, but are not automatically updated on your browser.
Transits were important for two developments in astronomy, that Kepler's theory using ellipses for planetary orbits was better than the Ptolemaic theory and fixing the size of the solar system. Transits of Mercury and Venus can happen because they are the only planets that orbit between the Earth and the Sun. By using ellipses to describe the orbits of the planets Kepler was able to predict when transits would occur. The Ptolemaic theory that used circular orbits did not have the accuracy needed to do predict these events, even after epicycles and equants were introduced. In 1627, Kepler predicted that a transit of Mercury would occur on November 7, 1631. Pierre Gassendi watched from his Paris observatory and saw a small black dot move across the face of the Sun on that day. A real triumph for the Kepler calculations!
Later transits, especially of Venus, would be used to measure the distance between the Earth and the Sun — the astronomical unit that we now know is 149,597,870,700 meters (or 92.75 million miles).
But on November 11, 2019, we celebrate the success of Kepler's ideas. As we watch Mercury move across the Sun, you could also remember our successes in using Kepler's ideas to slingshot the Voyager spacecraft through a Grand Tour of the outer planets, or to use Venus to send the Parker Solar Probe ever closer to the Sun, or even the incredible accuracy of GPS positions we take for granted as we move about in our everyday lives.
Never look at the uneclipsed Sun with unprotected eyes!
You can safely watch the transit at https://mercurytransit.gsfc.nasa.gov.
My thanks to the SDO scientists, engineers, and web programmers that made this SDO Data Event possible.
Enjoy!
