Anti-tail

File:C2007N3Lulin2panel brimacombe.jpg

Comet Lulin antitail to the left, ion tail to right

File:Comet A3 2023 Tsuchinshan-Atlas.jpg

Comet C/2023 A3 (Tsuchinshan–ATLAS) as it appeared on October 14th 2024 with a prominent "anti-tail" pointing towards the horizon.

File:Anti-tail.jpg

Showing how a comet may appear to exhibit a short tail pointing in the opposite direction to its type II or dust tail as viewed from Earth i.e. an antitail

An antitail, also known as an anti-tail, is an apparent spike projecting from a comet's coma which seems to go towards the Sun, and thus geometrically opposite to the other tails: the ion tail and the dust tail. Despite a common misunderstanding, this phenomenon is not an optical illusion. The antitail consists of larger dust particles left behind by the comet. These dust particles are less affected by the Sun's radiation pressure and tend to remain roughly in the comet's orbital plane and eventually form a disc along the comet's orbit due to the ejection speed of the particles from the comet's surface. As Earth passes through the comet's orbital plane, this disc is seen side on, and appears as the characteristic spike. The other side of the disc can sometimes be seen, though it tends to be lost in the dust tail. The antitail is therefore normally visible for a brief interval only when Earth passes through the comet's orbital plane.

Most comets do not develop sufficiently for an antitail to become visible, but notable comets that did display antitails include Comet Arend–Roland in 1957, Comet Kohoutek in 1973, Comet Hale–Bopp in 1997, C/1999 H1 (Lee) in 1999, Comet Lulin in 2009, Comet PANSTARRS in 2013, C/2022 E3 (ZTF) in 2023, 12P/Pons–Brooks in 2024 and C/2023 A3 Tsuchinshan–ATLAS in 2024.

See also

• Coma – An extended envelope of escaping gas surrounding a comet's nucleus
• Limb brightening

External links

• Photo of Comet Arend–Roland in 1957 with prominent antitail.