In October 2007, the underwhelming comet 17P/Holmes produced the most spectacular cometary burst ever seen. Debris from this event will be visible this month through amateur telescopes in the Northern Hemisphere. Here’s when and how to look for it.
Finnish astronomer Markku Nissinen recalls the days almost 15 years ago when skywatchers first noticed the intense glow of a 2.1-mile (3.4 km) wide comet. Within days, the sheath of dust and gas surrounding the icy object known as 17P/Holmes became as wide as the Sun, and the comet’s brightness increased a millionfold.
“We didn’t know what happened at the time,” Nissinen told Space.com. “It was really amazing. It’s really amazing how it’s expanded. Since then, I have never seen anything like it.”
17P/Holmes has fascinated Nissinen ever since.
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“This comet is a Jupiter-family comet, but it’s different from all the other Jupiter-family comets we’ve seen,” Nissinen said. “In all known history, this comet has produced three such [powerful] outbreaks. None of the other members of the Jupiter family have ever done this. There is something completely different about this.”
About 600 comets of the Jupiter family are known, icy rocks that follow elliptical orbits around the Sun, with their farthest points being between the orbits of Mars and Jupiter. According to (will open in a new tab) Swinburne University in Australia, the Jupiter family is getting quite dim as they visit the central solar system every 20 or more years. Near the Sun, comets heat up and deplete the volatile compounds responsible for creating their bright cometary tails.
Astronomers don’t know what caused the unusual 17P/Holmes outburst in 2007, but they hope that observing the dust cloud and meteoroids that the event caused may shed some light on the mystery.
(Image courtesy of the Finnish Geospatial Institute)
Earlier this year, Nissinen and Maria Gritsevich, a planetary scientist at the University of Helsinki in Finland, published a study that analyzed the trail of this cometary debris and determined its trajectory through space.
They have discovered that this trail of dust and micrometeoroids will be visible this summer even in amateur telescopes, and now they are urging skywatchers to point their lenses at the trail to help better understand the mysterious comet.
Earth will cross the orbital plane of the debris trail in mid-August, they said, but skywatchers will have to wait until the full moon on August 11 as the moonlight eclipses the dust.
Amateur astronomers with telescopes with apertures of at least 11 inches (30 centimeters) equipped with CCD cameras should be able to detect trails with little technical skill, Gritsevich said, adding that skywatchers should focus on the trails for the next two nights. and then subtract the images to get rid of any noise.
“Most amateur astronomers can do that now,” she told Space.com. “People these days have advanced surveillance systems and they know how to do image subtraction, so it’s relatively easy.”
Richard Miles, a British amateur astronomer who heads the Asteroids and Remote Planets Section of the British Astronomical Association, told Space.com in an email that the best time to try his luck finding the trail would be after August. 22 when the moon wanes enough.
“Detecting a dust trail seen from the side as the Earth passes through the 17P/Holmes orbital plane requires sensitive cameras and fast optics,” Miles wrote. “The surface brightness of the dust trail is extremely low, probably <25 magnitudes per square arc second of the sky, which in normal dark skies is only a few percent brighter than the background sky."
Gritsevich and Nissinen have published an updated version of their calculations as a paper to be presented at the Europlanet Science Congress in September. You can read the article here (will open in a new tab)including detailed coordinates for where to look for trails.
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