The explosive green “devil comet” that recently roared close to Earth appeared to grow an impossible second tail as it passed us, new photos reveal. But this extra limb, known as an anti-tail, is actually an extremely rare optical illusion caused by the comet’s proximity to our planet.
12P/Pons-Brooks (12P) is a 17-kilometer-wide comet with a green hue, given off by pairs of carbon atoms, known as dicarbon, in its tail and coma – the gas cloud surrounding its icy crust or core. 12P is cryovolcanic, meaning it erupts occasionally when solar radiation superheats the comet’s icy innards, or cryomagma, building pressure in the core until the core splits and its innards eject into space. When this happens, the comet’s coma expands and reflects extra light, making the comet shine brighter than normal.
12P spends most of its highly elliptical, 71.3-year orbit around the Sun, out of view in the Oort Cloud – a reservoir of comets toward the Sun. edge of the solar system. But last year the comet sped through the inner solar system as it made its closest approach to the sun. And as it got closer to our home star, it erupted regularly.
During the comet first eruptions last yearthe extended coma grew, giving the impression that this was the case had grown a pair of demonic horns, which earned it its sinister nickname. But these horns did not appear in subsequent eruptions.
12P made its closest approach to the Sun since 1953 on April 21 this year, as it looped around our home star and headed back toward the outer solar system. The comet made its closest approach to Earth on June 2, when it reached a distance of about 1.5 astronomical units from our planet, which is about 1.5 times farther from Earth than the Sun.
On June 3, astrophotographers Michael Jäger, Gerald Rhemann and Lukas Demetz captured a striking photo of 12P from Namibia. In addition to its normal blurry tail, the comet in this photo also had a much longer and sharper tail, known as an anti-tail, that appeared to point in the opposite direction from the other tail.
Related: Explosive green ‘devil’s comet’ has a hidden spiral swirling around its icy heart, photo trick reveals
This secondary tail seemingly defies physics, because a comet’s tail forms when dust and gas are blown from its surface by solar wind, meaning the structure extends away from the Sun. But in the new photo, the antitail points directly toward the sun.
However, the comet had not actually grown a new tail. Instead, we see light reflecting off the gas and dust left in the comet’s wake. Normally this is invisible to us. But when Earth passes through the comet’s orbital plane, as it did on June 3, this trail of debris is illuminated by the Sun, the researchers said. Spaceweather.com.
This illusion is similar to how the Milky Way often appears as a bright band across an unpolluted night sky because we are looking at the plane of the galaxy from the side.
Comet antitails are rare. The last documented case was a anti-tail on green comet C/2022 E3 (ZTF)that made its closest approach to Earth in February 2023. Previously, anti-tails were also observed on Comet Kohoutek in 1973, Comet Hale-Bopp in 1997 and Comet PanSTARRS in 2013, LiveScience previously reported.
This isn’t the first time the tail end of 12P has made headlines. In April, as the comet prepared to swing around the sun, the main tail of 12P temporarily illuminated by a solar storm – a phenomenon known as a disconnection event.
When the comet was at its closest point to our home star, this was also the case visible to the naked eye of earth. However, it is no longer possible to see the comet in the night sky without one good telescope.
12P is now on the long journey back to the outer edges of the solar system and won’t return to the inner solar system until around 2095.