The comet designated as 12P/Pons-Brooks will reach its closest point to the Sun on April 21, 2024 as part of its 71-year orbit. During this event, the absolute magnitude is expected to reach 4.5 to 5.0 making it bright enough to possibly see with the naked eye from suburban (and darker) locations throughout the Northern Hemisphere. It will come within 0.8 astronomical units of the Sun (1 AU being the average distance from the Sun to the Earth). This comet’s closest approach to Earth will come on June 2 at a distance of 1.55 AU but it will be brightest closer to the Sun as material erupting from it is better illumated.
Some reports of seeing 12P/Pons-Brooks have already been noted in early March by observers with binoculars and small telescopes in dark locations. NASA reports that the comet may be visible to the naked eye on this year’s April 8 solar eclipse, whose path of totality will pass across a long section of Mexico, the United States, and Eastern Canada.
The best way to view the comet in the Pacific Northwest is by looking toward the west shortly after sunet during March through its closest approach toward the sun. After April 21, the comet may become lost in the light of twilight until early May at which point it begins to set before the Sun does. As a general rule, Pacific Northwest residents in cities and towns larger than about 5,000 people will need to travel to more rural areas to see 12P/Pons-Brooks with the naked eye. Decreased pollution and other haze are helpful. Using a decent pair of binoculars will improve chances of seeing it in cities. Of course, this assumes clear skies.
Readers may remember Comet NEOWISE, which was visible to the naked eye during the summer of 2020. The peak magnitude of NEOWISE in 2020 was 0.5 to 1.0. This is much brighter than expectations out of 12P/Pons-Brooks. Note that lower absolute magnitude values represent brighter objects than those with higher values.
People viewing 12P/Pons-Brooks with the naked eye should not expect views like the featured image at the top of this article. When I observed NEOWISE from my suburban Kennewick neighborhood in 2020, it appeared as a faint oval-shaped smudge in the sky.
Comet 12P/Pons-Brooks is estimated to be about 30 km (20 mi) in diameter with an orbital period similar to Halley’s Comet, meaning that seeing it is a once or twice in a lifetime event. Its closest approach to the Sun takes it just outside the orbit of Venus while its furthest point of the sun is about 33.6 AU away around the same distance of Neptune.
The eight main planets and many other objects orbit the Sun on more or less the same plane. By contrast, 12P/Pons-Brooks has a steep orbital inclination meaning that if viewed from the side the comet’s path would rise well above and pass a bit below the plane of the main planets.
This object is an icy body. As it approaches the Sun its surface warms leading it to erupt dust, gas, and ice creating the distinctive tail that generally points away from the Sun. This tail does not exist when the comet is outside the Inner Solar System because of cooler temperatures reaching the comet surface. Outburst events with a larger than usual amount of eruptive material can cause it to temporarily brighten.
The discovery of 12P/Pons-Brooks is attributed to Jean-Louis Pons during its 1812 appearance. Other astronomers independently observed it later during that same pass. Comets noted in European and Chinese records in both 1385 and 1457 are likely to have been 12P/Pons-Brooks. Chinese observations of a comet from before that period may also have been it.
RESOURCES
CU Boulder Night Sky Light Pollution map
NASA Jet Propulsion Laboratory information page
The Sky Live page showing its location relative to any location on Earth
The featured image is of 12P/Pons-Brooks photogtaphed early March 2024 by Wikipedia user Nielander.
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