An astrophoto of Comet Catalina by Damian Peach, showing the comet's 2 tails -- one is a neutral dust tail blown back by solar wind pressure and the other is an ion tail, shaped by the sun's magnetic field.
Full resolution version can be found on SEN.com .
Sen/D. Peach (used with permission)
7 Intimate Close Encounters with Comets: Photos
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On Aug. 6, 2014, the European Space Agency's Rosetta spacecraft completed its decade-long journey to reach Comet 67P/Churyumov-Gerasimenko, becoming the first spacecraft to ever orbit a comet. The mission will reach its epic climax when it releases a small robotic lander, called Philae, onto the cometary surface in November. The lander will drill into the surface while Rosetta tags along with the comet's orbit as Churyumov-Gerasimenko makes close approach of the sun. Although Rosetta is unprecedented in that no other mission has achieved orbital insertion around a comet, it's certainly not the first robotic probe to make an intimate cometary encounter. So here's a rundown of 7 encounter of 6 comets by 5 spacecraft since the first close encounter with Halley's Comet in 1986.
NASA/ESA
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Unquestionably the most famous comet in history, Halley's Comet was a prime target for space agencies in 1986 during its 75- to 76-year orbit through the inner solar system. Comet science is still a developing field, but in 1986, very little was known about the composition of these interplanetary vagabonds. In October of that year, the 15-kilometer-long Halley's Comet was visited by the European Space Agency's Giotto mission. The half-ton probe came within 600 kilometers (373 miles) of the comet's nucleus, taking the first photographs of the outgassing vapor from discrete areas of the surface producing its tail and coma (the gas surrounding the nucleus). It was this mission that confirmed the "dirty snowball" theory of cometary composition: a mix of volatile ices and dust. However, Giotto was only able to get so close to the famous comet with the help of the "Halley Armada," a number of international spacecraft all tasked with observing this rare event. Giotto captured the closest imagery, but two Russia/France probes (Vega 1 and 2) and two Japanese craft (Suisei and Sakigake) observed from afar.
ESA
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At roughly half the size of Halley's comet, Comet Borrelly was found to have similar attributes to its famous cousin. The nucleus was also potato-shaped and blackened. Outgassing vapor was also observed coming from cracks in the nucleus crust where volatiles were exposed to sunlight, sublimating ices into space. NASA's Deep Space 1 probe flew past the comet with a close approach of 3,417 kilometers on Sept. 22, 2001.
NASA
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Comet Wild 2 -- pronounced "Vilt" after its Swiss discoverer Paul Wild who spotted it in 1978 -- underwent a dramatic alteration in 1974. It is calculated that due to a close pass of Jupiter in 1974, the 5 kilometer-wide comet now orbits the sun every 6 years as opposed to its leisurely 43 years before the gas giant bullied it. The orbital modification meant that Wild 2 was an ideal target for NASA's Stardust mission to lock onto. On Jan. 4, 2004, the Stardust probe gave chase, getting so close to the comet that it was able to collect particles from Wild 2's coma. This image was taken at a distance of less than 240 kilometers (149 miles). The Stardust sample return canister came back to Earth safely, landing in Utah on Jan. 15, 2006. The microscopic particles captured from the comet continue to provide a valuable insight into the organic compounds comets contain. Interestingly, the Stardust spacecraft was granted a mission extension (dubbed New Exploration of Tempel 1 -- NExT). In 2011 it rendezvoused with its second comet, Tempel 1 -- the scene of NASA's 2005 Deep Impact mission -- to analyze the crater that Deep Impact's impactor left behind on the cometary surface.
NASA
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NASA's Deep Impact mission reached the eight-kilometer-wide (five-mile-wide) comet Tempel 1 in 2005. On July 4, the probe deliberately smashed its impactor into the comet's nucleus, producing a cloud of fine material. A crater -- 100 meters wide (328 feet) by 30 meters (98 feet) deep -- was left behind. A treasure trove of compounds were spotted by the Deep Impact spacecraft and the explosion could be observed from Earth. In 2011, the recycled Stardust-NExT mission visited comet Tempel 1 for the second time.
NASA
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The fifth space probe encounter with a comet happened on Nov. 4, 2010. NASA's recycled Deep Impact probe -- now the EPOXI mission -- visited comet Hartley 2, examining its strange-shaped nucleus. Described as a "peanut" or "chicken drumstick," this comet is an oddity. During its close approach of under 700 kilometers (435 miles), EPOXI photographed the comet's irregular topography: two rough lobes connected by a smooth center. Jets of gas could be seen being ejected from discrete locations. During the Hartley 2 flyby press conference at NASA's Jet Propulsion Laboratory (JPL), mission scientists expressed their surprise that these jets of vapor are being emitted from sun-facing and shaded regions on the comet surface. Needless to say, analysis of the Hartley 2 flyby data will keep scientists busy for some time to come. "This is an exploration moment," remarked Ed Weiler, NASA's Associate Administrator for the Science Mission Directorate, during the conference.
NASA
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On Feb. 14, 2011, the veteran Stardust-NExT (New Exploration of Tempel) mission made history by visiting a comet for the second time. Comet Tempel 1 was first encountered by NASA's Deep Impact mission in 2005 after smashing the cometary nucleus with an impactor. This second encounter provided scientists with an unprecedented opportunity to study the same comet after six years of orbiting the sun. Preliminary findings suggested Tempel 1 has undergone some erosion during those six years in deep space. Also, the impact crater left behind by Deep Impact was imaged during the Stardust-NExT flyby and it appeared to match the size and shape predicted after the 2005 impact. However, the crater appeared smoother than expected, so work is ongoing to analyze the 72 photographs taken by the flyby to understand the processes shaping the comet's nucleus.
NASA
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At 5:29 a.m. EDT (9:29 a.m. GMT) on Aug. 6, 2014, the European Rosetta spacecraft completed a 6.5 minute-long engine burn to insert itself into orbit around Comet 67P/Churyumov-Gerasimenko. Once under the influence of the comet's weak gravity, the spacecraft began to carry out a series of triangular loops, taking several days to complete. The long-duration mission is the first of its kind, where the spacecraft will study the comet from orbit, watching for surface changes as it approaches the sun, making perihelion (the point of closest solar approach). In November, a small lander called Philae will touch down on the surface to drill into the comet's material, revealing its small-scale composition. This photograph from Rosetta was captured on Aug. 3 when the probe was fast approaching the comet at a distance of less than 300 kilometers. READ MORE: Rosetta Probe Makes Historic Comet Rendezvous
ESA
Before we knew the true nature of comets, they were seen as harbingers of doom . The appearance of an unexpected bright object in the sky was seen as a bad omen and often identified as the cause of some terrible happenings here on Earth. Even our old friend Halley’s Comet was excommunicated by Pope Callixtus III as an instrument of the devil back in 1456!
Thankfully, we now understand comets much better and their appearance is welcomed as an exciting sight in the night skies of the 21st Century.
Comet Catalina — more formally known as C/2013 US10 (Catalina) — is the latest cometary visitor that has put in an appearance and sky watchers in the Northern Hemisphere have been looking forward to getting a glimpse as the festive comet gently drifts across the sky.
As its name suggests, C/2013 US10 (Catalina) was discovered in October 2013 by the Catalina Sky Survey when it was about a million times fainter than objects that can be seen by the naked eye. The survey utilizes two US telescopes, one which is 1.5 meters in diameter and the other 68 centimeters in diameter, and between them both they scour the sky every night on the look out for so-called near-Earth objects (or NEOs). In doing so, it often picks up all manner of other objects and C/2013 US10 (Catalina) was one of those special objects.
Since its discovery, the comet has been heading toward the sun reaching speeds of over 100,000 miles per hour (165,000 kilometers per hour). It made its closest approach to the sun on Nov. 15 and is now heading back out of the inner solar system but putting on a bit of a show on its way out.
Its closest approach to Earth will be on Jan. 17 when it rattles by at 68 million miles (110 million kilometers). That may sound close by astronomical distances, but it is still over 280 times more distant than the moon is to the Earth. If you want to try and spot the comet for yourself then there is a great opportunity to find it on the nights around the 31st December.
If you can drag yourself away from New Year celebrations, head outside and locate the bright red star Arcturus in the constellation of Bootes. Once you have found Arcturus, scan the area around the star with binoculars and you should easily find the elongated fuzzy blob of the comet.
Those of you with DSLR cameras or those with cameras cable of taking longer than usual exposures — perhaps 20 seconds or so should try and get a pic of the comet as it passes by.
What a great way to start 2016!