In late May and early June, Earthlings will get a glimpse of Comet SWAN and will do so with the unaided eye. Currently, the comet is barely visible to the naked eye in the southern hemisphere just before sunrise, giving skywatchers a relatively rare view of a comet bright enough to be seen without a telescope.
But the initial discovery of Comet SWAN was not made from the ground, but through an instrument aboard the NASA/ESA SOHO Observatory. The new comet was first detected in April 2020, by an amateur astronomer named Michael Mattiazzo using data from a SOHO instrument called Solar Wind Anisotropies, or SWAN. The comet appears to leave the left side of the image and reappear on the right side around May 3, due to the way 360-degree maps of the entire SWAN sky are displayed, just as a globe is represented by a 2D map.
SWAN maps the constantly flowing solar wind in interplanetary space by focusing on a particular wavelength of ultraviolet light emitted by hydrogen atoms. The new comet, officially classified C / 2020 F8 (SWAN) but nicknamed Comet SWAN, was seen in the images because it releases huge amounts of water, about 1.3 tons per second.
Since water is made of hydrogen and oxygen, this made Comet SWAN visible to SOHO instruments. Comet SWAN is Comet number 3,932 discovered with SOHO data. Almost all of the nearly 4,000 discoveries have been made using data from SOHO’s coronagraph, an instrument that blocks the bright face of the Sun using a metal disk to reveal the relatively weak outer atmosphere, the corona.
This is the twelfth comet discovered with the SWAN instrument since SOHO’s launch in 1995, eight of which were also discovered by Mattiazzo. Comet SWAN made its closest approach to Earth on May 13, at a distance of approximately 76 million km. The closest approach to the Sun from Comet SWAN, called perihelion, will take place on May 27.
Although it can be very difficult to predict the behavior of comets that get so close to the Sun, scientists expect Comet SWAN to stay bright enough to be seen as it continues its journey.
Comet SWAN Characteristics
A few days ago, the comet was as bright as some of the faintest stars in the night sky, visible to the unaided eye. In astronomical terms that a magnitude 5. Some indications suggest that the comet may become as much as three to four times as birth, or magnitude of around 3.5 as it makes its way northwards through the constellations of Triangulum and Perseus.
Comet Swan is 0.6 AU (90 million km; 230 LD) from our planet in the constellation of Cetus and less than 40 degrees from the Sun
Although there’s a kind of astronomical hysteria about seeing the comet with the naked eye, the northern hemisphere will have a hard time seeing the comet. It will become visible to the northern latitudes as it makes its way through the constellation of Pisces but as revealed by Forbes, “only in pre-dawn twilight skies currently lit-up by a bright moon.”
Compared to the combat of Comet Atlas which was calculated at around 15 arcminutes in diameter, which falls in terms of size, somewhere between the Sun (1,392,000 km diameter) and Jupiter (139,820 km), according to Space Weather Archive, comet SWAN’s coma isn’t small either.
According to simulations, Comet SWAN is making its way around the sun in a period of around 25 million years.
As explained by Space.com, this means that the last time the comet made its way through the inner parts of the solar system it was during the Oligocene Epoch.