Donati's comet

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Donati's comet

(doh-mah -teez) (1858 VI) A spectacular comet famous for its coma with multiple haloes: parabolic envelopes with vertices toward the Sun and foci near the apparent nucleus. These haloes were regular and sharp and are thought to have been produced by repetitive ejection of material from a single active area exposed successively to solar radiation as the solid cometary nucleus rotated every 4.6 hours.

Donati’s Comet

 

a long-period comet having a period of about 150 years. One of the brightest comets, it moves around the sun in an elongated elliptical orbit having a perihelion of 0.58 astronomical units and an aphelion of 300 astronomical units. The comet was discovered on June 2, 1858, by Giovanni Donati. The remarkable duration of its visibility to the naked eye (from the middle of August to the beginning of December) has made it possible to study it in great detail. In the first half of October 1858, Donati’s comet attained a brightness of a star of zero magnitude and had three tails: tails of types I and II (following F. A. Bredikhin’s classification) measuring up to 70 million km long and a short, diffuse, type III tail. Up to seven luminous envelopes have been observed around the nucleus.