On Mercury’s Double Sunrises…

Another cool reblog from Tumblr’s Child of the Cosmos

On Mercury’s double sunrises:

Mercury possesses the most eccentric orbit of any planet. It rotates on its axis three times for every two revolutions it makes around the Sun. But when it arrives at perihelion (its closest to the Sun) Mercury’s orbital velocity will exceed its rotational speed. As a consequence, a hypothetical observer standing on Mercury would see a sight unique in our entire solar system. Over the course of eight days (fours days before perihelion to four days after perihelion), the Sun would appear to reverse its course across the sky, then double back and resume its normal track across the sky.

If our observer were located on that part of Mercury where the Sun were to rise around the time of perihelion, the Sun would appear to partially come up above the eastern horizon, pause and then drop back below the horizon, followed in rapid succession by a second sunrise!

The third GIF shows Mercury’s orbit around the Sun. Viewed from the Sun, Mercury exhibits a peculiar motion. Its spin & elliptical orbit are synchronized, so it appears to stop rotating every time it reaches perihelion.

On why only two spacecrafts have visited the innermost planet:

Compared to other planets, Mercury is difficult to explore. The increased speed required to reach it is relatively high, and due to the proximity to the Sun, orbits around it are rather unstable.

A trip to Mercury requires more rocket fuel than that required to escape the Solar System completely. As a result, only two space probes have visited the planet so far.

Reblogged from Child of the Cosmos — On Mercury’s double sunrises… on Tumblr

Video via T0R0YD on YouTube

Cool! And speaking of our visits to Mercury, you might want to check out my Cosmos To NASA – April Fools! post! 😉

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