Mercury transit to the sun will occur on Monday, a rare event that will not be seen again until 2032. Astronomers have been observing the heavenly traverse for nearly four centuries, but the first reliable observation, in 1
631 ., was so different from what scientists at the time expected it was almost thrown away.
Mercury transit observations were reported as early as the ninth century, but after Galileo introduced the telescope in 1610, it became clear that earlier observers may have seen sunspots rather than Mercury.
For transit on November 7, 1631, a number of astronomers created to capture the motion of Mercury in front of our star. Only one Catholic priest in Paris named Pierre Gassendi published his observations which showed that he could not believe exactly what he saw at that time.
"I was far from suspected that Mercury would project such a small shadow," Gassendi wrote.
The priest suggested that the little spot he saw was just a sunspot, because he expected the Mercury disk to cover about one-tenth of the sun, when in fact it looks more like a hundredth of the size of our star.
"It is really curious that early observers thought they were watching Mercury in the sun when they saw sunspots and that now Gassendi, when he was actually observing Mercury in the sun, thought he was looking at sunspots," Albert Van Helden writes in 1976 for the Journal of Astronomy History.
There was still quite a bit of disagreement about the arrangement and scale of the cosmos during Gassendi's time, which was the period when scientists fought whether the Earth revolved around the sun or vice versa. however, both camps are more il less agreed on the approximate size of the planets. And when it came to Mercury, they both made a mistake.
"Fortunately, he continued to observe for several hours and noticed that the tiny dark spot was moving much further. fast in the face of the sun and in a different way than there would be sunspots, "writes Todd Timberlake, author of Finding Our Place in The Solar System.
This persistence will pay off in the long run and will lead to some key adjustments in our understanding of Mercury's orbit and the size of planets It is. Mercury's unexpectedly small size will also eventually lead to a more accurate measurement of the distance between the Earth and the Sun. This, in turn, would give us a better idea of how vast the universe is.
This whole understanding was almost delayed when Mercury was momentarily written off as just another spot in the sun.