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Comets: Related Pages.
Most comets are believed to originate in a cloud (the Oort cloud) at large distances from the Sun consisting of debris left over from the condensation of the solar nebula.
Comets Seem to Be Icy Dirtballs Oct 13, 2005 - The traditional view of comets is that they're "dirty snowballs"; mostly water ice, covered by a layer of dust picked up as they travel through the Solar System. But after Deep Impact's collision with Comet Tempel 1, scientists are reversing that description: they're more like "icy dirtballs". When Deep Impact smashed into the comet, it released more dust than water vapour. This means that comets are mostly dust and rocks, held together by a water ice "glue". What the Ground Telescopes Saw During Deep Impact Sep 16, 2005 - Researchers have had a few months to crunch through the data collected during Deep Impact's collision with Comet Tempel 1. The latest research published in the Journal Science used findings from three giant telescopes atop Mauna Kea in Hawaii. The observations determined that as much as 25 fully-loaded tractor trailer-trucks worth of material was excavated out by the impact. The comet seems to have a complex mix of silicates, water and organic compounds beneath its surface. The Risk of a Comet Strike is Low Sep 13, 2005 - Although astronomers have discovered plenty of comets, they've always thought it was just a fraction (less than 3%) of the number of comets out there - and one of them might have our names on it. Fortunately, this scenario doesn't seem so likely, according to new research from scientists at the Australian National University, astronomers have probably found more like 20% of comets. That means that small comets, capable of destroying a city, probably only hit the Earth once every 40 million years, and big continent-busting comets probably only hit us once every 150 million years. Sep 8, 2005 - When Deep Impact excavated a crater in Comet Tempel 1, it released a spew of material that has existed since our Solar System first formed, billions of years ago. By analyzing this material, scientists have come up with better recipes for how to make planets, comets and asteroids. They were expecting to see water ice and silicates, but they were surprised to see materials like clay and carbonates (ingredient in seashells), since it was believed they required liquid water to form. Surprising Insights Into Comet Tempel 1 Sep 7, 2005 - Even though Deep Impact smashed into Comet Tempel 1 several months ago, scientists are still analyzing the data gathered before and after the collision. Very few close up pictures of comets have ever been taken, so the data gathered by Tempel 1 is very valuable, and sometimes surprising. The nucleus of Temple 1 has layers that show in topographic relief, ranging from smooth surfaces to impact craters. It's also extremely porous, which allows the surface to heat up and cool down almost instantly when hit by sunlight. Aug 19, 2005 - The most successful comet hunter in history is actually the ESA/NASA SOHO spacecraft, which spends its time gazing at the Sun. Since many comets streak past the Sun all the time, they often get caught in SOHO's cameras. Toni Scarmato from Calabria, Italy discovered both SOHO's 999th comet, and then 5 minutes later he discovered its 1,000th as well. Almost all the discoveries have been made using SOHO's LASCO instrument, which images the Sun's large corona. Jul 25, 2005 - The powerful Palomar observatory has released its before and after images of Comet Tempel 1 after it was struck by Deep Impact. In the earliest images taken after impact, the photos show a plume of material extending 320 km (200 miles) from the comet's centre. This dust plume lasted for several nights, and allowed astronomers to measure its rotation. Two days later another, smaller plume was visible, which could have vented from an outburst of gas and dust coming from the impact site. Jul 21, 2005 - NASA's Deep Impact spacecraft completed its primary mission - excavating a crater in Comet Tempel 1 - on July 4. It was a smashing success, and the spacecraft is now disarmed, like a bee without its stinger. But the flyby spacecraft is still working great and looking for work. NASA is now encouraging proposals from scientists who have some good ideas about what Deep Impact could be used for next. Until a new goal is decided, the agency will put the spacecraft into a parking orbit in the vicinity of the inner planets. Comet Tempel 1 Settles Down Again Jul 15, 2005 - After getting smashed by Deep Impact two weeks ago, Comet Tempel 1 has finally settled back down and appears normal again. Right after the impact, material streamed off the comet, travelling 700 to 1000 km/h (430 mph to 600 mph). This created a large, diffuse halo around the comet which faded away over the next few days. The same jets astronomers could see before the impact are still streaming away, so it appears Tempel 1 suffered very little damage. How Much Material Was Blasted Off By Deep Impact? Jul 11, 2005 - One of the instruments tuned into Deep Impact is NASA's Swift satellite, normally designed to detect and analyze gamma ray bursts. Swift has been watching the expanding debris cloud, and detected increasing numbers of X-rays every day. This has enabled scientists to accurately measure the total amount of material released. So far, it appears that several tens of thousands of tonnes of debris were blasted off the comet into space; enough to bury a football field under 9 metres (30 feet) of dust. Deep Impact's Plume Was Bigger Than Expected Jul 11, 2005 - When Deep Impact's impactor slammed into Comet Tempel 1 on July 4, 2005, it released a tremendous cloud of fine powdery material from the comet's nucleus. Scientists are still studying the volumes of data acquired by Deep Impact, but it appears this plume was much brighter than anyone had expected; its surface was more like talcum powder than sand. The crater was probably on the large side of what was being predicted: 50 - 250 metres (165 - 820 feet). Gemini Sees Rocky Material on Tempel 1 Jul 7, 2005 - As Deep Impact's impactor probe smashed into Comet Tempel 1 this week, every available observatory, on land and in space was watching to help gather as much science as possible from this $333 million mission. The Gemini North telescope, located on Hawaii's Mauna Kea successfully captured images, before and after the collision that clearly show the debris cloud moving off the comet. They also found evidence that rocky materials were exposed on the comet's surface. Jul 6, 2005 - Scientists monitoring NASA's Swift satellite had a good view of Deep Impact's collision with Comet Tempel 1. Although the space-based observatory was designed to watch for gamma ray bursts, its instruments were handy for this observation since it can see in several wavelengths at the same time. One of its most important observations from the impact is a quick rise in ultraviolet light. This means that the impactor struck a hard surface, as opposed to something soft and snowy. SOHO Nears 1,000th Comet Discovery Jul 6, 2005 - NASA/ESA's Solar and Heliospheric Observatory, the most successful comet hunter in history, is expected to discover its 1,000th comet this summer. In fact, half of all comets ever discovered can be attributed to SOHO. This is because many comets close to the Sun were once part of an enormous comet that was broken up. SOHO can resolve chunks as small as the size of a house as they blaze up near the surface of the Sun. Many of SOHO's comets have been discovered by observers through the Internet. Deep Impact Made a Bright Flash Jul 5, 2005 - When Deep Impact's impactor spacecraft smashed into Comet Tempel 1, the two objects collided at a speed of 10 km/s (6.3 miles/s). The force of this collision generated a tremendous amount of heat and light which served to illuminate the whole area for the Deep Impact flyby spacecraft. The impactor spacecraft was able to capture images of Tempel 1 as it approached, and the last image was taken at an altitude of only 30 km (19 miles). Deep Impact Smashes Into Tempel 1 Jul 3, 2005 - NASA's Deep Impact mission completed its primary goal July 4th, when its impactor spacecraft smashed into Comet Tempel 1. NASA scientists are eagerly reviewing the impact data captured by the flyby spacecraft to learn what size crater was excavated, and the kind of material ejected into space. The 373 kg (820 lb) copper impactor crossed paths with Tempel 1 right on schedule, at 0552 UTC (1:52 am EDT). More than 60 observatories on Earth and in space were on hand to watch the collision and help gather data. As expected, Comet Tempel 1 was entirely unfazed by the impact, and hasn't changed its orbit in any detectable way. Jul 3, 2005 - NASA's Deep Impact spacecraft released its impactor "probe" Sunday morning, and changed its trajectory to pass a comfortable distance from Comet Tempel 1. When it was released, the impactor was 880,000 km (547,000 miles) away from Tempel 1. After releasing the impactor, Deep Impact began firing its engine for 14 minutes, which slowed down, and kept it out of the path of the onrushing comet. If all goes well, the impactor will strike Tempel 1 on Monday, July 4 at 0652 UTC (1:52 am EDT). Jun 30, 2005 - The European Space Agency's Rosetta spacecraft has captured its first photograph of Comet 9P/Tempel 1, Deep Impact's target. Rosetta is quite distant, so Tempel 1 is at the very limits of its detection abilities. The spacecraft will help analyze the gas, ice and debris that spew off of Comet Tempel 1 when Deep Impact smashes into it on July 4. This is just a job on the side, though, as Rosetta has a date with its own comet, 67P/Churyumov-Gerasimenko, in 10 years from now. Deep Impact Sees a Burst from Tempel 1 Jun 29, 2005 - NASA's Deep Impact spotted an outburst of ice and gas from the surface of Comet Tempel 1, which has been turned into a short animation of several frames. This is the second outburst astronomers have seen from the comet this month, and gives astronomers a great opportunity to fine tune instruments in space and here on Earth to get the most science out of the July 4 "encounter". Spacecraft Wakes Up for Comet Collision Jun 28, 2005 - The Submillimeter Wave Astronomy Satellite (SWAS) has been asleep for the past 11 months, but now it's being woken up for a very important task: to watch the collision between Deep Impact and Comet Tempel 1. SWAS completed 5.5 years of service to the astronomical community, and it was put into hibernation for just something like this. The spacecraft is especially good at measuring the abundance of water molecules in ice and dust, so it should be able to help analyze the ejected material when the spacecraft slams into the comet on July 4. Print Version Print This Article |
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