OrbitalHub

ESA dixit:

“When a small Solar System body such as a moon or an asteroid passes in front of a star and temporarily blocks its light, the occultation is an extraordinary chance for astronomers to study the properties of the foreground object. And, of course, the more accurate the prediction of both objects’ positions on the sky, the better the observations. This is why, when a group of astronomers were planning to observe the rare occultation of a distant star by Neptune’s moon Triton on 5 October 2017, they made a special request to the Gaia team.

The astronomers, led by Bruno Sicardy from Pierre and Marie Curie University and the Observatory of Paris, France, had used all available observations to compute the path that the moon’s shadow would sweep across our planet. Within less than three minutes, the occultation would first cross Europe and North Africa, rapidly moving towards North America. They knew that somewhere, within this couple of thousand kilometre-wide stretch, would lie a very special thin strip, only about 100-km across. Observers situated on this strip would be perfectly aligned with both Triton and the distant star, and therefore able to see the so-called central flash. This sharp brightening of the star happens half way through the occultation, and is caused by focussing of the starlight by deep layers in the moon’s atmosphere – about 10 km above surface. The central flash contains all-important information to study the profile of Triton’s atmosphere and the possible presence of haze in it.”

Chasing a Stellar Flash with Assistance from Gaia

Catching the Shadow of a Neptunian Moon

Video Credit: ESA