Astronomers eye comet pair

Astronomers are hopeful that comets SWAN and ATLAS will continue to brighten to the point they are visible with the naked eye. Here's how, when, and where to look for them.

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Comet C/2020 F8 (SWAN) on May 2nd
Tony Rice
, NASA Ambassador

Comet SWAN

Comet C/2020 F8 (SWAN) was discovered in March by the the Solar Wind Anisotropies (SWAN) camera aboard the NASA's Solar Heliospheric Observer (SOHO) spacecraft. The camera, a joint project with NASA and atmospheric science agencies in France and Finland, normally watches solar wind looking for variations.

The comet was discovered by Michael Mattiazzo,an amateur astronomer who carefully reviews the SOHO data made available to the public each day. This is his eighth discovery.

Study of Comet Swan's trajectory reveals it orbits the Sun about every 25 million years. The last time this comet would have passed through our neighborhood would have been late in the Paleogene period while the continents continued to drift toward their present positions and  elephants with trunks first appeared.

Currently Comet SWAN is visible only to observers in the southern hemisphere, but if it continues to brighten at its current pace, it could be visible from darker locations in our area by the end of May. Look low on the northeastern horizon 30-60 minutes before sunrise.

Comets ATLAS and SWAN have been brightening again (image: Rice, data: Minor Planet Center)


Discovered on December 28, 2019 by astronomers using the ATLAS (Asteroid Terrestrial-impact Last Alert System) robotic astronomical survey system in Hawaii, Comet C/2019 Y4 (ATLAS) was on its way to becoming the brightest comet since Hale-Bopp in the mid 1990s. Comet Atlas was even following a similar trajectory as the Great Comet of 1844 which was brighter than Venus at its peak (magnitude -5.1)

The comet brightened rapidly in the coming months, raising hopes that it might become bright enough to be seen with the naked eye. Those hopes crumbled with the comet as it fell apart on April 11, the day Comet C/2020 F8 (SWAN) was discovered.

The Hubble Space Telescope imaged the breakup of Comet C/2019 Y4 (ATLAS) on April 23, 2020. (Credit: Hubble NASA ESA STSci D Jewitt, UCLA)

While astronomers are not exactly sure why the comet broke up, this is not an uncommon end for comets as they draw closer to the Sun. As these icy bodies like comets are warmed, gasses are released from inside, sometimes causing them to break apart.


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