NASA Astronomy Picture of the Day 31 January 2023: Green Comet ZTF over Spain

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NASA Astronomy Picture of the Day 31 January 2023: A comet orbits the Sun, but unlike an asteroid, it's composed of ice and dust. When a comet gets close to the Sun, its ice and dust content start to vaporize. So, when seen in a telescope, a comet appears fuzzy and has a tail. If you are a fan of watching comets, there is some exciting news for you. A comet which was last seen by Neanderthals is all set to pass Earth this year. The comet is called Comet C/2022E3 (ZTF). It is a long-period comet that originated in the Oort cloud.

NASA's Astronomy Picture of the Day is an image of the Comet ZTF captured in a triple view in Caceres, Spain, by astrophotographers Javier Caldera & Miguel Gracia. Although comets pass Earth relatively frequently, there is something special about this one. The comet has a period of around 50,000 years, meaning the last time it flew past Earth closely, it was seen by Neanderthals during the Upper Paleolithic period on Earth.

According to NASA, this comet was discovered by astronomers using the wide-field survey camera at the Zwicky Transient Facility in 2022 in March last year. While it is already visible in the northeastern sky, the best view will be tomorrow, February 1, 2023 when it will be closest to the Earth.

Comet ZTF has a distinctive shape. The now bright comet visiting the inner Solar System has been showing not only a common dust tail, ion tail, and green gas coma, but also an uncommonly distinctive antitail. The antitail does not actually lead the comet -- it is just that the head of the comet is seen superposed on part of the fanned-out and trailing dust tail. The giant dirty snowball that is Comet C/2022 E3 (ZTF) has now passed at its closest to the Sun and tomorrow it will pass at its