January 18, 2021

Coming Wirtanen Comet, which can be seen this Sunday at a glance | Science

Coming Wirtanen Comet, which can be seen this Sunday at a glance | Science


Elliptical orbit of Halley's comet. The largest blue circle represents the orbit of Neptune. The orbit of Comet 46PWirtanen only reaches the red circle, the orbit of Jupiter.
Elliptical orbit of Halley's comet. The largest blue circle represents the orbit of Neptune. The orbit of Comet 46P / Wirtanen only reaches the red circle, the orbit of Jupiter.

Those who see a comet crossing the night sky can feel emotion, amazement or feeling that a disaster is looming. In the past, people debated what comets were: an atmospheric phenomenon, a fire in the sky or a star with a tail like a broom.

This month we will have the opportunity to check which visual description best fits the perception of each one, because it is foreseen that the Comet 46P / Wirtanen Make an appearance in mid-December and it will be perfectly visible.

Analysis of a comet

Thanks to study that Edmond Halley made in the 17th century of what is known as Halley's comet, astronomers discovered that comets are within our solar system. They have very elliptical or elongated orbits around the Sun, which can reach far beyond Pluto.

Comet 67PChuryumov-Gerasimenko, photographed by the Rosetta Mission on September 19, 2014. The original objective of Rosetta was the 46PWirtanen, but NASA exceeded the deadline to launch it in time.
Comet 67P / Churyumov-Gerasimenko, photographed by the Rosetta Mission on September 19, 2014. The original objective of Rosetta was the 46P / Wirtanen, but NASA exceeded the deadline to launch it in time.

When comets are far from the Sun they are not special. They are often compared to dirty snowballs. But unlike a rocky asteroid, a comet also has volatile frozen gases, such as methane, carbon monoxide, carbon dioxide and ammonia along with its rock, ice and dust cores.

As this star approaches the Sun, the heat causes the volatile elements to stop being solid and become gases, in a process called sublimation. Thanks to water, methane, carbon dioxide and ammonia, tail is created, the fundamental characteristic of comets, and also a bright cloud, called hair, around its nucleus.

Comet Hale-Bopp has a blue ion tail and a curved powder tail.
Comet Hale-Bopp has a blue ion tail and a curved powder tail.

Actually, comets have two different queues: one tail of dust and another of ions or gas. The solar wind and the pressure of the radiation move away the tails of the Sun. The ultraviolet light ionizes part of the material of the tail, creating a charged gas that interacts with the solar wind and ends up pointing directly to the opposite side of the Sun. And the tail of Uncharged powder still follows the orbit of the comet, which makes it more curved.

When this process happens, it becomes brilliant and becomes a great spectacle. However, it turns out extremely difficult predict how bright a comet will be, because you never know exactly how gases will behave. Even measuring brightness is complicated. Unlike the brightness of a star, which concentrates on a single point from our perspective on Earth, the brightness of a comet is scattered over a larger area.

A visit of the 46P / Wirtanen

The astronomer Carl Wirtanen discovered the comet that bears his name in 1948. He was an expert hunter of stellar objects that used pictures of the night sky to observe that he moved quickly, at least speaking from the astronomical point of view.

The orbit of Comet 46P / Wirtanen keeps it quite close to the Sun. Its aphelion, or the point farthest from the Sun, is approximately 5.1 astronomical units (AU), which is just a little bigger than Jupiter's orbit. Its perihelion, or its closest approach to the Sun, is about 1 AU, roughly the distance from Earth to the Sun. It takes about 5.4 years in traversing this trajectory, which means that it is visible quite frequently compared to other famous comets.

In these moments he approaches his perihelion. It will reach its closest point to the Sun on December 16, the day that will shine the most.

The 46P / Wirtanen is an especially active comet – called hyperactive kite– and usually shine more than other comets of a similar size. This makes it a good comet for observation. The predictions claim that it will have a brightness up to a magnitude 3, a little brighter than Megrez, the most tenuous star of the Carro. However, some predictions say it will shine at a magnitude of only 7.6 which will make it impossible to observe it with the naked eye. The least bright object visible to the naked eye is of a magnitude of 6, in perfect observation conditions. The system used by astronomers goes the other way: cThe smaller the number, the brighter the object.

The "+" sign indicates where you can see Comet 46PWirtanen on the nights of December 14-19. The graph shows the points one hour after sunset for a latitude between 40 and 90 degrees.
The "+" sign indicates where you can see Comet 46P / Wirtanen on the nights of December 14-19. The graph shows the points one hour after sunset for a latitude between 40 and 90 degrees.

The best conditions to observe the 46P / Wirtanen is to do it in the darkest possible sky and when the comet is brightest (December 16). Will be between the constellation of Taurus and the group of stars of the Pleiades.

If it can not be seen with the naked eye, a pair of binoculars or a small telescope will help. Right now a telescope is necessary to see it. You can start following it using maps that show your position night after night. Its location in the sky also means that it is visible to all, except in the extreme southernmost latitudes.

The position of the comet near Taurus makes it ideal to observe it all night. Taurus is east after sunset and moves westward through the night.

The Conversation

Hopefully there are clear skies to observe it! Then you can decide for yourself if this comet is a good or a bad omen by 2019.

Shannon Schmoll is director of the Abrams Planetarium, Department of Physics and Astronomy, Michigan State University.

Disclosure clause. Shannon Schmoll does not receive a salary, does not work as a consultant, does not own shares, or receives financing from any company or organization that can benefit from this article, and has declared no relevant links beyond the aforementioned academic position.

This article was originally published in English on the web The Conversation.

Translation of News Clips.

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