To passionate stargazers, Comet 21P/Giacobini-Zinner – or Comet 21P, for short – might ring a very familiar bell. The bright-green comet is believed to be the source of the Draconid meteor shower, which graces the sky each year in early October.
Last year, Comet 21P treated sky watchers to a rare and fantastic appearance on September 10, when it paid a close visit to Earth about a month before the peak of the Draconids. As The Inquisitr reported at the time, the comet came within 36.4 million miles of Earth — or about a third of the distance from our planet to the sun. That was its closest approach to Earth in 72 years.
A few days after its close flyby, the European Space Agency (ESA) unveiled a spectacular photo of the green comet, captured on the eve of its momentous approach. The icy celestial body was later spotted in deep space by professional astrophotographer Miguel Claro, who snapped a glorious image of Comet 21P.
Scouring the skies from the Cumeada Observatory in Portugal’s Dark Sky Alqueva Reserve, Claro got a glimpse of the beautiful green comet as it was passing by a bright star cluster on the day of its close approach to Earth. The astrophotographer spent quite some time imaging the comet and ended up producing a stunning photo, which has now been published on the Space website.
The breathtaking photo shows Comet 21P streaking across a sparkling field of stars as it crosses paths with an open star cluster known as Messier 37, or M37. Nestled some 4,500 light-years from our solar system, this is the richest and brightest open star cluster in the Auriga constellation.
As The Inquisitr previously reported, open star clusters are collections of up to a few thousand stars of the same age, formed from the same giant molecular cloud and loosely bound together by gravity.
The newly released deep-space image shows the Comet 21P making its way through the Auriga constellation, with its greenish coma lighting up the sky as it meets up with the glimmering star cluster.
“The comet is approximately 1 degree from the colorful open star cluster M37,” explains Claro, noting that the star cluster “shines with an apparent magnitude of 6.2” — or around the faintest threshold of luminosity that can be picked up by observers with the naked eye.
The new image is a composite photo combining 25 exposures of 160 seconds each. The frames were taken on September 10, 2018, as the comet was closing in for its encounter with Earth. Its close flyby of our planet occurred a few minutes before Comet 21P hit perihelion, or its closest orbital point to the sun.
Comet 21P/Giacobini-Zinner is what astronomers call a periodic comet. The icy celestial body zips around the sun once every 6.6 years and, in the process, it passes through our neck of the cosmic woods, just like it did last year.
As it was leaving the solar system, Claro pointed his telescope at the green comet once again. The astrophotographer captured remarkable footage of Comet 21P heading back out toward the outskirts of the solar system, as seen in the video below.
The footage is a short time-lapse showing a sequence of three hours taken during the night of September 14, 2018, while Comet 21p Giacobini-Zinner was still bright and moving fast against the starry sky of Alqueva, Portugal.