Flying some 250 miles above the Earth’s surface, the astronauts on board the International Space Station (ISS) are often treated to spectacular views of our world that few mortals ever get to see first-hand.
From their unique vantage point, the astronauts capture stirring photographs of our planet — as shown in this Flickr album uploaded by European Space Agency (ESA) astronaut Thomas Pesquet, who crewed the orbital outpost during Expedition 50.
Another ESA astronaut has recently shared his own captivating snapshots taken from the space station after he caught sight of a rare optical phenomenon known as a glory.
According to the ESA, this beautiful phenomenon is usually spotted by pilots and mountain climbers venturing at high altitudes, who sometimes catch a glimpse of a glory while looking down at mists or clouds.
“Forming a miniature circular rainbow, glories are seen when the sun shines from behind and interacts with water droplets to refract light back to the observer,” explain officials from the space agency.
Such exquisite views are a rarity to witness on Earth and become even more extraordinary when they are seen from orbit. But ESA astronaut Alexander Gerst, who helms the ISS as part of Expedition 57, has managed to photograph a glory in space while looking down at the Earth from his perch on board the orbiting laboratory.
Gerst spotted the phenomenon on September 14 during his Horizons mission. The astronaut snapped two stunning pictures of the glory and posted them on Twitter earlier this week, reports Space.
Surprised to see a pilot's glory from the #ISS This phenomenon's often visible from airplanes, or when looking down into a foggy crater. Our shadow is (theoretically) right in the middle of the rainbow, but we don't have a core shadow due to our altitude. https://t.co/oFvFGpPooO pic.twitter.com/4VgydLtPRu— Alexander Gerst (@Astro_Alex) November 6, 2018
When pilots observe a glory during flight, they see the shadow of their airplane cast on a cloud below surrounded by a halo of light. But the aircraft’s shadow has nothing to do with how a glory is created, notes EarthSky.
This fascinating optical phenomenon forms under specific atmospheric conditions and is caused by sunlight interacting with tiny droplets of water that go in the composition of mist and clouds.
Often mistaken for a circular rainbow, a glory is made up of several concentric rings that dim progressively as they move further from the center — each shining blue on its inner rim and red on the outer one.
“The major source of the glory’s central illumination is light reflected once inside droplets. There are lesser contributions from light reflected 10, six, and five times,” explains Atmospheric Optics.
To see a glory on a wisp of cloud, you need to have the sun directly behind your head. This is because the phenomenon is centered on the antisolar point, directly opposite of the sun from an observer’s perspective.
“That’s why, in order to see a glory, the clouds or fog causing it have to be located below the observer, in a straight line with the sun and the observer’s eye,” notes EarthSky.
A similar thing occurred in Gerst’s case. The astronaut photographed a circular, rainbow-like gleam projected onto a cloud in Earth’s atmosphere. The difference is that his photos didn’t capture a shadow at the center of the rainbow since the ISS flies too high above the planet to project a shadow.