Comet's tail is longer than a billion km long

The ion tail of comet 153P / Ikeya-Zhang is at least 7.5 times the distance between Earth and the Sun, nearly double the previous record of the comet Hyakutake.

A team of scientists from the United Kingdom and the United States announced a new study about the length of comet tail 153P / Ikeya-Zhang on the arXiv database on May 31. To conduct the study, they had to reroute the data nearly 20 years ago.

Comet 153P / Ikeya-Zhang has an ionic tail longer than a billion km. (Photo: Gerald Rhemann).

The Cassini spacecraft launched into space in 1997. In 2002, when traveling between the orbits of Jupiter and Saturn, the ship recorded a large amount of protons in space. This has become a mystery that has not been solved for many years. In the new study, scientists believe that the number of protons Cassini recorded came from the ionized tail of comet 153P / Ikeya-Zhang.

Interactions between the Sun and comets can cause two types of tails to form. The more familiar type is the dust tail, produced when the Sun's radiation heats the comet core, releasing the amount of dust once trapped in this ice ball. The other is an ion tail, formed when the neutral gas in the comet core is ionized by radiation. In the case of comet 153P / Ikeya-Zhang, protons pulled from hydrogen gas during this ionization could have been blown by the solar wind towards Cassini.  

The location of the comet and the amount of proton Cassini discovered indicate that the spacecraft flew past the ion tail of comet 153P / Ikeya-Zhang. The team studied the protons more closely and found that, since leaving the comet head, they have traveled a distance 6.5 times the distance between the Earth and the Sun. Taking into account the change of the comet's path during the measurement, this ion tail is at least one billion km long, 7.5 times the distance from the Earth to the Sun.

Because the spacecraft have only passed the comet's tail a few times, the probability of this record is highly broken, the researchers said. They are expecting new results from the interaction between the Solar Orbiter spacecraft and the comet ATLAS.