Green comet Nishimura is about to disappear for 400 years – here’s how to see it before it goes

Comet Nishimura survived a close encounter with the Sun, giving us a brief window in which we could spot it in the sky before retreating into the outer solar system and not returning for 400 years.

The Nishimura object was discovered on August 12 of this year, and its unusual green glow attracted the attention of astronomers around the world. It made its closest approach to the Sun on September 17, and was visible in the Northern Hemisphere in the early morning hours before sunrise for several days before the encounter.

Comets are made of rock and ice, giving them the nickname dirty snowballs. As the comet approaches the Sun, much of the ice turns into electrically charged gas called plasma, forming the comet’s tail. There was uncertainty about whether comets could survive contact with the Sun as they passed within 33 million kilometers of the star’s surface.

“Some people don’t survive,” he says. Don Polacco At the University of Warwick in the UK, it could instead evaporate completely. Fortunately, Comet Nishimura escaped this fate. “It’s now moving away from the sun and back into the frigid depths of the solar system, where it will spend the next 400 years before moving closer to the sun again,” Polacco said. “We have one last chance to see Nishimura before he disappears completely.”

During the approach, Nishimura was hit by a severe solar storm. This burst of charged particles from the Sun briefly blew away the comet’s plasma tail by a so-called cutting phenomenon. Although the mechanisms behind these events are not fully understood, Laboratory research in 2018 showed that it could be due to the electrostatic field generated by the interaction of the plasma and the solar wind.

Comets appear green because their coma, or gas surrounding their core, contains a relatively rare type of carbon gas called diatomic carbon, which is two carbon atoms bonded together.

If you live in the northern hemisphere and want to see this for yourself, it will appear near the horizon just after sunset for the next few days. If you look to the western horizon as soon as the sun sets, you’ll see Mars. Nishimura is located just to the right of Mars.

It will take a little longer for people in the Southern Hemisphere to see the comet, perhaps a week or so. It can be seen in the western sky after sunset, but it will appear directly below Mars.

“There are reports that they can be seen with the naked eye, but it’s still best to use binoculars,” Polacco says. “After this it will get dark, so you will need a telescope.”