Green Comet Nishimura Makes a Rare Visit to Earth’s Skies


A newly discovered comet, named after the amateur astronomer who first spotted it, is making a close approach to Earth this week. The comet, which has a greenish hue, will be visible in the night sky for a few days before it swings around the sun and heads back to the outer solar system.

Comet Nishimura: A New Visitor from the Oort Cloud

Comet Nishimura, or C/2023 P1 Nishimura, was discovered on August 12 by Hideo Nishimura, a Japanese space photographer. He noticed a faint object in his images of the night sky and reported it to the Minor Planet Center, which confirmed it as a new comet.

Green Comet Nishimura Makes a Rare Visit to Earth’s Skies
Green Comet Nishimura Makes a Rare Visit to Earth’s Skies

The comet is believed to originate from the Oort Cloud, a vast reservoir of comets and other icy bodies that surrounds the solar system beyond the orbit of Neptune. The Oort Cloud is estimated to contain trillions of objects, some of which occasionally get perturbed by the gravity of nearby stars or other forces and fall toward the sun.

Comet Nishimura is one of these rare visitors from the Oort Cloud. It has a hyperbolic orbit, which means it spends most of its time in the outer solar system before rapidly plunging toward the sun and slingshotting around it. The comet’s orbit is estimated to last about 430 years, which means the last time it passed close to the sun was around the year 1590, before the invention of the telescope. There are no records of any comets observed during that time that match Nishimura’s orbit, so this may be its first appearance in human history.

How to See Comet Nishimura in the Night Sky

Comet Nishimura will reach its closest distance to Earth on September 12, when it will pass within 78 million miles (125 million kilometers) of our planet. That is about two-thirds of the distance between Earth and Mars at their closest point. The comet will then reach its perihelion, or closest point to the sun, on September 17, when it will pass within 21 million miles (34 million kilometers) of the star. It will then be slingshot back into the outer solar system, where it will remain for centuries.

The comet has been brightening as it approaches the sun, reaching an equivalent magnitude of a small star. This means it is potentially visible to the naked eye under dark skies, but binoculars or a small telescope are recommended for a better view. The comet’s coma, or cloud of gas and dust that surrounds its solid core, gives off a green light because it contains molecules of dicarbon, which emit green light when they are broken down by sunlight.

The best time to see Comet Nishimura is in the early morning hours before sunrise, when it will appear low in the eastern sky. Sky and Telescope has shared charts that can help sky-gazers locate the comet. The comet’s tail will always point away from the sun, so it will change direction as it moves across the sky.

Why Comet Nishimura is Important for Science

Comet Nishimura is not only a spectacular sight for stargazers, but also a valuable source of information for scientists. Comets are considered to be remnants of the early solar system, preserving clues about its formation and evolution. By studying their composition, structure, and behavior, astronomers can learn more about the origin and history of our cosmic neighborhood.

Comet Nishimura is especially interesting because it is a new visitor from the Oort Cloud, which is largely unexplored and poorly understood. By observing how the comet interacts with the sun and its environment, scientists can gain insights into the physical and chemical properties of these distant objects. For example, they can measure how much gas and dust are released from the comet’s surface as it heats up, and what kinds of molecules are present in them.

Comet Nishimura also offers an opportunity to compare it with other comets that have different origins and orbits. For instance, Comet NEOWISE, which dazzled sky-watchers last year, came from the Kuiper Belt, a ring of icy bodies beyond Neptune’s orbit. Comet 2I/Borisov, which was discovered in 2019, was an interstellar visitor that came from another star system. By comparing these comets with Nishimura and others, astronomers can test their theories and models of how comets form and evolve in different environments.

Comet Nishimura is a rare and remarkable guest in our skies. It offers us a chance to witness a piece of our solar system’s history and mystery. Don’t miss this opportunity to see it before it disappears for centuries.


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