Mercury transits across Sun on November 11, NASA shares footage of rare event

In a rare event, Mercury crossed between the Earth and the Sun, on November 11, which was tracked by Solar Dynamics Observatory, a mission of the National Aeronautics and Space Administration (NASA). The observatory, which views the Sun in a variety of wavelengths of light in the extreme ultraviolet, tracked the journey which will not occur again until 2032. The transit lasted a little over 5.5 hours and ended after Mercury left the disk of the Sun but continued moving out through the corona for another 30 minutes.

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Kepler's vs Ptolemaic theory

Transits of only two planets can occur, Mercury and Venus, as they are the only planets that orbit between the Earth and the Sun. According to the Solar Dynamics Observatory, transits are important for two developments in astronomy, to establish that the Kepler's theory using ellipses for planetary orbits was better than the Ptolemaic theory and fixing the size of the solar system. While Kepler was able to predict the accurate time of transits by using ellipses to describe the orbits, Ptolemaic theory using circular orbits did not have the accuracy needed to do predict such events. 

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Success of Kepler's ideas

The real triumph of Kepler’s calculation came in 1631 when, as per his prediction of Mercury transit, French astronomer Pierre Gassendi watched a small black dot move across the face of the Sun from his Paris observatory on November 7, 1631. Later, Venus transits were used to measure the distance between the Earth and the Sun. NASA’s observatory said that November 11 was the day to 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,” said the Solar Dynamics Observatory.

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(With inputs from agencies)