10:30 AM (Wednesday) | *Comet SWAN is out there, but don’t expect the “comet of the century”*

Comet SWAN was only 4 degrees above the horizon on Sunday morning, May 10th, when it was photographed by Dr. Fritz Hemmerich over the Canary Islands (Spain). Credit to spaceweather.com.

Overview

This information may fall under the “haven’t we heard this before” category, but there is a comet out there that may be visible during the next few weeks.  Comet SWAN (C/2020 F8) was discovered in late March and it has now crossed the equator and is visible in the northern hemisphere.  The comet has faded a bit since last week, but it is still a relatively easy binocular object in the hours just before sunrise at magnitude +6, but barely above the (northeastern) horizon.

Skymap showing the location of Comet SWAN just before sunrise on Thursday, May 14th.

Details

When attention was focused on Comet ATLAS back in March, another comet was discovered by an Australian amateur astronomer, Michael Mattiazzo, while he was exploring imagery from the Solar Wind Anisotropies camera on NASA’s Solar and Heliospheric Observatory (SOHO).  The comet’s name, SWAN, comes from the acronym for the camera and it may be visible in the northern hemisphere during the next few weeks as it sweeps past the sun.

A light curve of Comet SWAN from the Comet Observation Database (COBS) clearly illustrates the rapid rise in the comet's brightness from a few weeks ago, followed by the current downturn in recent days. (Image credit: COBS Comet Observation Database/CC BY-NA-SA 4.0)

According to space.com, at the time of its discovery in late March, the comet was undergoing a sudden outburst of hydrogen gas which is something the SOHO’s SWAN instrument is well adapted to picking up. Water/ice from the comet’s nucleus evaporates as the comet approaches the sun. Solar ultraviolet radiation splits up the water molecules and the liberated hydrogen atoms glow in ultraviolet light. The comet was 135 million miles away from the sun when it was discovered in late March, but it will eventually come to within about 40 million miles when it arrives at its perihelion (closest point) on May 27th.  On Tuesday, May 12th, Comet SWAN actually made its closest approach to Earth (~53 million miles) on this trip into the inner solar system.

Skymap showing the location of Comet SWAN just before sunrise on Saturday, May 16th.

In terms of viewing the comet, it won’t be too easy in the mid-latitudes of the northern hemisphere during the next several days and will most likely require binoculars or a small telescope and a clear view of the northeastern horizon.  The comet will be hanging very low in the northeastern sky just before dawn during the next several days. By late this month and into June, northerners will get a crack at viewing the comet during evening twilight. By then, it will be crossing pretty close to the bright star Capella, but again, it will be only a few degrees above the horizon (north-northwest).  One bit of hope, there have been a couple of “outbursts” by the comet in recent days including one just last week and such an occurrence could briefly make for easier viewing conditions - even with the unaided eye - but don’t expect the “comet of the century.”

Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com

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