Comet SWAN Is About to Pass Earth and May Be so Bright It's Visible With Naked Eye

Last month, astronomers discovered a new comet dubbed C/2020 F8 (SWAN) or Comet SWAN. It is currently around 61 million miles away from Earth and is traveling at around 85,000 miles per hour towards the vicinity of our planet on its path around the sun.

On May 13, the comet it is set to make its closest approach to Earth when it will be located around 53 million miles from our planet. And a couple of weeks later, on May 27, it will reach its closest point to the sun, or perihelion—at distance of around 40 million miles from the star.

Comet SWAN appears to be greenish in color and while thought to be relatively small, it is exhibiting a vast trail of debris, which astronomer Phil Plait calculated to be at least 11 million miles long.

As comets move closer to the sun, they are blasted with increasing quantities of radiation. This warming leads to a release of gas and dust, creating a temporary atmosphere known as a coma, which forms around the nucleus of the object. In addition, two tails also form during this process—the gas tail and the dust tail.

The gas tail appears due to the effect of the solar wind—charged particles from the sun—on electrically charged gas particles released by the comet. Meanwhile, interactions between photons—particles of light—emitted by the sun, the solar wind, and vaporized dust in the comet's coma lead to the formation of the dust tail.

People living in the southern hemisphere will be treated to the best views of the comet, especially in the days centered around the Earth close approach. It should be visible until early June.

"Right now the comet is visible through binoculars and telescopes only from the southern hemisphere, but as May gives way to June it'll become visible in binoculars and telescopes from southern parts of the northern hemisphere," Rick Fienberg, a spokesperson from the American Astronomical Society, told Newsweek.

"The comet will never be particularly well placed for most of us in the United States, but observers in southern Florida and Hawaii could get some decent views from east-facing coasts. For those in the southern parts of the U.S., the comet will peek above the northeastern horizon at dawn in mid to late May," he said.

According to astronomy website TheSkyLive, Comet SWAN appears to have brightened slightly compared to last week and now has an observable magnitude of around 5.1, providing stargazers with some spectacular views.

"The best comet I've seen in some years!" astrophotographer Damien Peach said, describing his images of Comet SWAN.

A magnitude of 5.1 is potentially bright enough to be just about visible to the naked eye from the southern hemisphere in dark and clear conditions—and there have been several reports of naked-eye sightings from amateur astronomers in the past few days.

On the magnitude scale, brighter objects have smaller magnitudes than dimmer ones. For example, an object with magnitude 5 appears fainter in the sky than one with a magnitude of 4.

Generally, the dimmest astronomical objects visible with the naked eye have a magnitude of 6.5. But while anything brighter than this should technically be visible without optical aid, a host of factors, ranging from light pollution to cloudy weather, can determine whether or not the object can be seen unaided.

Because the moon is currently nearing its full phase, for example, naked-eye observations of the comet could be particularly difficult in the next few days, according to Fienberg.

"Naked-eye visibility depends on several things. The two most important are sky conditions—clarity, darkness—and the apparent size of the target. Let's assume that the comet's current apparent magnitude is 5.1. A magnitude-5.1 star, which is a point source, would be dimly visible in a clear, dark country sky but would be invisible in a city sky or even in a country sky on a night when the moon is bright—as it is now," he said.

"A magnitude-5.1 comet, however, has its light spread out over the coma and tail, such that while the total light might match that of a star of similar magnitude, no part of the comet is bright enough to be noticeable by naked eye because that light is not concentrated in a point but spread out over a larger area," he said.

Some astronomers are predicting that the comet could reach a magnitude of around 3.5 by mid-May as it gets closer to the sun and is blasted with increasing amounts of radiation, meaning it could be clearly visible with the naked eye in dark skies.

But the behavior of comets is notoriously unpredictable and it is possible that Comet SWAN could fade, or even break apart, as it approaches the star. Furthermore, there may be additional viewing problems, according to Fienberg.

"By mid to late May, the comet could brighten to naked-eye visibility—technically. The problem is it'll be very low in the northeastern sky at dawn, with the sky brightening as the comet rises, so even if the comet is by the numbers bright enough to be seen without optical aid in a dark sky, it may not be discernible in the growing twilight except in binoculars or a telescope," he said.

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Stock image: Artist's illustration of a comet. iStock

Comet SWAN was only officially described in mid-April by amateur astronomer Michael Mattiazzo, who discovered the object in data collected by the SWAN instrument aboard the Solar and Heliospheric Observatory—a spacecraft operated by NASA and the European Space Agency that was launched in 1995.

The discovery of Comet SWAN came just as another comet, C/2019 Y4 (ATLAS), broke up as it approached the sun. Comet ATLAS was the subject of much attention prior to its break-up, with some predictions suggesting that it could become the brightest comet for more than 20 years. However, this never materialized.

If you would like to track the movements of Comet SWAN, visit TheSkyLive website where you can find real-time information about the object's location in the sky.