Bright space rock E3 is about to make its closest approach to Earth in 50,000 years. OC/2022 E3 is a comet of oort cloud which was discovered by the Zwicky Transient Facility on March 2, 2022. The comet reached its perihelion (when it is closest to the Sun) on January 12, 2023, at a distance of 1.11 AU (166 million km) and the closest pass to Earth will be on February 1, 2023, at a distance of 0.28 AU (42 million km).
The comet can glow brighter than magnitude 6 and become visible to the naked eye as a small fuzzy speck against a dark enough sky, but it can only be seen from Portugal with binoculars.
The comet that passed close to the Earth at the time of the Neanderthals
C/2022 E3 has been visible since the 12th, but it will only be visible from Portugal from today, thanks to cloud breaks and the change in the Moon's cycle. Thus, to observe the comet, it will have to be in a place where there is almost no artificial light around. If you can spot it, using binoculars, you might even be able to see the tail. According to NASA, the best time to see the comet is before dawn.
The comet is currently heading towards the constellation of boots and close to Hercules (can see an interactive sky map here). The comet's location makes it difficult to see for observers in the southern hemisphere. From its current location in the night sky, its projected path maps it past Ursa Minor (the Little Dipper), passing Camelopardis at its closest approach.
Comets shine due to a combination of their chemical makeup and sunlight. Comets passing close to the Sun are illuminated and heated by its energy. As a result, the molecules on its surface evaporate and become fluorescent. the heads of comets glow green when they contain cyanogen or diatomic carbonaccording to NASA.
The green comet could reach magnitude 5 when it is closest to Earth, according to EarthSky. Does this mean that the smaller the number, the brighter the object. The full moon's apparent magnitude is around -11, and the faintest objects seen by the Hubble Space Telescope are around magnitude 30. The faintest stars our naked eye can see are magnitude 6.
The approaching space rock isn't the only recent green comet; in 2018, the comet 46P/Wirtanen was quite bright for observers to see with the naked eye, and in 2021 the comet Leonard glowed green while the ball of ice made its cosmic trajectory.
So keep your eyes on the clear nights ahead. If you see something with a faint green glow, it's probably our new cosmic visitor.