Comet Day (2061)
"Miss Murphy in first grade
wrote its name in chalk
across the board and told us
it was roaring down the stormtracks
of the Milky Way at frightful speed
and if it wandered off its course
and smashed into the earth
there’d be no school tomorrow."
~ Halley's Comet, Stanley Kunitz (1905-2006)
Although it is unlikely for this editor to make it to the return date for Halley's comet, predicted for July 28th of 2061, there are other celebrity and newly discovered comets that provide for excellent comet watching, particularly this month's special comet NEOWISE, shown below over Newgrange photographed by Anthony Murphy. This tartan illustrates the blue and green glow of a comet's dust tail and ionized gas tail formed by the solar wind flow against a dark sky. Comet NEOWISE is a long period comet with a near-parabolic orbit discovered on March 27, 2020, by astronomers during the NEOWISE mission of the Wide-field Infrared Survey Explorer (WISE) space telescope. By July 2020, it was bright enough to be visible to the naked eye and one of the brightest comets in the northern hemisphere since Comet Hale–Bopp in 1997. It is predicted to remain visible to the naked eye throughout most of July 2020. This comet will not return for another 6800 years! ☄️
A great comet is a comet that becomes exceptionally bright. There is no official definition; often the term is attached to comets such as Halley's Comet, which are bright enough to be noticed by casual observers who are not looking for them, and become well known outside the astronomical community. Great comets are rare; on average, only one will appear in a decade. Comets are officially named after their discoverers.
Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 74–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and the only naked-eye comet that might appear twice in a human lifetime. Halley last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.
During its 1986 apparition, Halley's Comet became the first comet to be observed in detail by spacecraft, providing the first observational data on the structure of a comet nucleus and the mechanism of coma and tail formation.
These observations supported a number of longstanding hypotheses about comet construction, particularly the "dirty snowball" model, which correctly predicted that Halley would be composed of a mixture of volatile ices – such as water, carbon dioxide, and ammonia – and dust. The missions also provided data that substantially reformed and reconfigured these ideas; for instance, it is now understood that the surface of Halley is largely composed of dusty, non-volatile materials, and that only a small portion of it is icy.
The vast majority of comets are never bright enough to be seen by the naked eye, and generally pass through the inner Solar System unseen by anyone except astronomers. However, occasionally a comet may brighten to naked eye visibility, and even more rarely it may become as bright as or brighter than the brightest stars. The requirements for this to occur are: a large and active nucleus, a close approach to the Sun, and a close approach to the Earth.
The first confirmed sighting of Halley's comet was in 240 BC. The next predicted perihelion of Halley's Comet is the 28th of July, 2061.
Designed by Carol A.L. Martin, this tartan illustrations the blue and green glow of the ionized gases of a comet in the dark sky.
For more great comets in history, click one of the most recent Great Comets, Comet Hale-Bopp, 1997.