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| Chaiyah |
 Posted: Sat Jan 13, 2007 11:26 am Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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Amethyst
Joined: 18 Jan 2005
Posts: 25365
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Isn't that sort of using the term "comet" kind of, LOOSELY?
If it's that large, it's a transient planetary body, not just a comet.
S'pose all the Powers That Be are underground now?
I wonder.
: ) Em
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"You are a child of the Universe no less than the trees and the grass. You have a right to be here. And whether or not it is clear to you, no doubt the Universe is unfolding as it should" Desiderata |
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| Arrgy |
Posted: Sat Jan 13, 2007 11:31 am Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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Weed Whacker
Joined: 17 Jan 2005
Posts: 21163
Location: Obama Nation! |
| Arcane Son wrote: | | Arrgonaut wrote: |
If the comet is 150,000 miles around. That makes it 5+ times the size of earth?
Damn!!!  |
Where did you get that size estimate from Arrgonaut? Just curious. |
Thought i saw it on one of the first pages of this post. 
major  I got a lil exagerated...150 mi. but they don't know yet...looking.
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How strange is the lot of us mortals! Each of us is here for a brief sojourn; for what purpose he knows not, though he senses it. But without deeper reflection one knows from daily life that one exists for other people.
Albert Einstein
I want to be Robin Hood but I can't |
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| green dog |
Posted: Sat Jan 13, 2007 12:14 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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High Flier
Joined: 18 Jan 2005
Posts: 6876 |
| Kent Stedman wrote: | | The wave rings have me stumped so I asked around: |
They're refraction fringes, not gravity waves. Have you ever looked at the raw SOHO images available in the archive? Do you know how they're processed to enhance the detail and create the coloured images we usually see on the web site?
I don't know the process followed by SOHO (though it's probably available somewhere on the web). I did do a bit of work on those images when talking about the "Minbari image" with vianova a couple of years ago. To bring out the detail, I had to subtract the previous image from the most recent; this greatly increases the contrast. There are always thin refraction rings around the occulting disk; in subtracting images, they're mostly removed. When one of the images being subtracted is brighter than the other due to a change in the brightness near the limb of the Sun, then the rings from one image are brighter in that area and the subtraction doesn't remove them. There might also be fluctuations in the camera that vary the image brightness from one image to another. |
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| green dog |
Posted: Sat Jan 13, 2007 12:16 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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High Flier
Joined: 18 Jan 2005
Posts: 6876 |
| Shechaiyah wrote: | Isn't that sort of using the term "comet" kind of, LOOSELY?
If it's that large, it's a transient planetary body, not just a comet.
S'pose all the Powers That Be are underground now?
I wonder.
: ) Em |
400 years of progress, and we're still running to "duck and cover" when a comet swings by the Sun. Sigh. |
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| Kent Steadman |
Posted: Sat Jan 13, 2007 12:17 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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Nester
Joined: 15 Mar 2005
Posts: 732
Location: http://cyberspaceorbit.com/ |
SOHO TEAM NOTE:
"Please note that while we do have "real time" data from SOHO/LASCO, we do not have continuous, uninterrupted 24hr contact with the spacecraft. This means that there will be periods where the images are not updating. These periods typically last only a couple of hours, but sometimes our ageing data processing machines do crash and a technician has to manually restart the process. At weekends this can take time, so please be patient with us! You can always check the spacecraft contact schedule to see when the planned data gaps will occur."
http://sohowww.nascom.nasa.gov/operations/schedule/schedule.html
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| green dog |
Posted: Sat Jan 13, 2007 12:26 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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High Flier
Joined: 18 Jan 2005
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| Kent Steadman |
Posted: Sat Jan 13, 2007 12:30 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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Nester
Joined: 15 Mar 2005
Posts: 732
Location: http://cyberspaceorbit.com/ |
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| green dog |
Posted: Sat Jan 13, 2007 12:40 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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High Flier
Joined: 18 Jan 2005
Posts: 6876 |
To me, it looks like some sort of reflection. The line joining the two bright centers goes right through the center of the disk, and the distance from the disk is the same for both centers:
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| Kent Steadman |
Posted: Sat Jan 13, 2007 12:47 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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Nester
Joined: 15 Mar 2005
Posts: 732
Location: http://cyberspaceorbit.com/ |
| Quote: | | To me, it looks like some sort of reflection. The line joining the two bright centers goes right through the center of the disk, and the distance from the disk is the same for both centers: |
Thankye
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| radstar |
Posted: Sat Jan 13, 2007 1:06 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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Airborne
Joined: 17 Jan 2005
Posts: 2657
Age: 61  Libra
Location: middle earth |
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| Guest |
Posted: Sat Jan 13, 2007 2:40 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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| Kent Steadman wrote: | | Quote: | | To me, it looks like some sort of reflection. The line joining the two bright centers goes right through the center of the disk, and the distance from the disk is the same for both centers: |
Thankye |
Kent,
If the comet is still approaching the sun, would that make it huge?
If it's between the sun and earth, isn't it still huge?
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| Circulator 38 |
Posted: Sat Jan 13, 2007 5:27 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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High Flier
Joined: 18 Jan 2005
Posts: 4712
Location: The city that rhymes with fun
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To astronomers a comet is a frozen body composed of various ices and dust, or, to quote astronomer Fred Whipple, it is a "dirty snowball." What is it that makes comets exciting to astronomers? Here are a few of the reasons:
- They are unpredictable. Comets can suddenly brighten or fade from view in a matter of hours. They can lose their tail or develop multiple tails. Sometimes they can even split into two or more pieces, so that, through a telescope, several comets can be seen moving together across the sky.
- Comets represent some of the oldest, basically untouched objects in the solar system. Their very composition seems to represent the original makeup of the vast nebula that ultimately condensed to form the sun and planets.
- Recent years have revealed comets have shaped the progress of life as we know it here on Earth. Many astronomers are convinced that early collisions between Earth and comets brought the vast amounts of water that now make up Earth's oceans. These oceans enabled life to get a foothold. On the flip side, the dinosaurs are certainly an example of how collisions between Earth and comets can also bring extinction to different lifeforms. Evidence is growing to show that other periods of mass extinction may have also been caused by such collisions. What would life on Earth be like today if extinction-causing collisions had never occurred?
- Finally, comets are like a time machine. It is thrilling to watch a comet like the famous Halley's Comet with a 75-year period and think about what life was like when the comet was last seen. Similar thoughts fill your mind when watching comets which may have last traveled through Earth's skies serveral hundreds, or thousands, or even millions of years ago.
In the not too distant past, comets were considered bad omens. Written records from China and Europe extending back nearly 3000 years tell of occasional great comets moving through the sky and the terrible events that people thought they caused. In more recent times, the verbal accounts of the natives of North, Central, and South America, as well as numerous islands scattered across the Pacific Ocean have been recorded. These also inform us that comets were a dreaded sight. Overall, different societies have blamed comets for wars, earthquakes, sicknesses, and even the deaths of leaders.
What is a comet?
As stated earlier, a comet is basically a ball of ice and dust. The typical comet is less than 10 kilometers across. Most of their time is spent frozen solid in the outer reaches of our solar system. The graphic below shows all of the components of a comet. At the stage being discussed at this point, the comet is nothing more than the nucleus. Except for a few suspected dead comets, and a couple of suspicious asteroids that occasionally show gas emissions like a comet, the nucleus is never really seen from Earth. By the time a comet becomes bright enough to be seen from our planet, it is usually exhibiting a coma.
The Nucleus
After the spacecraft Giotto photographed the nucleus of Halley's comet back in 1986, we now know that a comet's nucleus probably has a surface that is best described as a black crust. Although the length of the nucleus of Halley's comet is about 12km, it is believed that comet nuclei can range from 1 km to perhaps 50km across. Comet Hale-Bopp of 1997 had a nucleus that was perhaps 40km across.
The black crust of the nucleus helps the comet absorb heat, which in turn causes some of the ices under the crust to turn to a gas. With pressure now building beneath the crust, the serene, but frozen landscape begins to bulge in places. Eventually the weakest areas of the crust shatter from the pressure beneath, and the gas shoots outward like a geyser and is referred to by astronomers as a jet. Any dust that had been mixed in with the gas is thrown out as well. As more and more jets appear, a tenuous gas and dust shell forms around the nucleus and this is called the coma.
The nucleus of Halley's Comet as photographed by Giotto in 1986. Note the active areas that are spewing dust and gas into space. This material will form the coma and tails of the comet.
This is a drawing of the region surrounding the nucleus of comet Hale-Bopp on 1997 March 10. This shows an intense emission or jet coming from the nucleus which is forming features called "hoods" or arcs within the coma. The hoods are features formed as a result of the rotation of the nucleus. In the case of Hale-Bopp, a new hood was formed nearly every 12 hours.
The Coma
Comets can typically display a coma several thousand kilometers in diameter, with the size being dependent on the comet's distance from the sun and the size of the nucleus. The latter is important because since jets generally spring up on the side of the nucleus facing the sun (that side gets warmest), and since large nuclei have a greater surface area facing the sun, then there is the potential for larger numbers of jets and greater amounts of gas and dust feeding the coma. One of the largest comets in history was the Great Comet of 1811. It was one of the few comets in history to be discovered with a relatively small telescope at an unusually great distance from the sun, in this case over half-way to the planet Jupiter's orbit. The nucleus has been estimated as between 30 and 40 kilometers in diameter. At one point during September to October 1811 the coma reached a diameter roughly equivalent to the diameter of the sun and was a very notable naked-eye object seen by people around the world.
Even though the coma can become quite large, its size can actually decrease about the time it crosses the orbit of Mars. At this distance the particles streaming out from the sun provide enough force so as to act as a wind and will literally blow the gas and dust particles away from the nucleus and coma. This disruption is the process responsible for a comet's tail, the most spectacular feature of a comet.
The Tail
When you have a large comet that moves well inside the orbit of Earth, you have the potential for a long tail. The current record holder for longest tail length is the Great Comet of 1843. Its tail extended more than 250 million kilometers. What this means is that if the comet's nucleus were placed in the center of the sun the tail would have stretched passed the orbits of Mercury, Venus, Earth, and Mars!
http://cometography.com/educate/comintro.html
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disclaimer: I do not necessarily agree with any article I post; I may be 100% opposed. I post for information only.
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| Sunsong |
Posted: Sat Jan 13, 2007 5:42 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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Airborne
Joined: 24 Dec 2005
Posts: 2462
Location: Black Hills |
| Quote: | | In the not too distant past, comets were considered bad omens. Written records from China and Europe extending back nearly 3000 years tell of occasional great comets moving through the sky and the terrible events that people thought they caused. In more recent times, the verbal accounts of the natives of North, Central, and South America, as well as numerous islands scattered across the Pacific Ocean have been recorded. These also inform us that comets were a dreaded sight. Overall, different societies have blamed comets for wars, earthquakes, sicknesses, and even the deaths of leaders. |
We haven't really come much past this belief. Movies like Deep Impact (excellent visual effects!) don't help. 
Thanks, Circ! I really liked the very last part, The Tail. I wonder if anyone has found any documented guesstimates on the dimensions of Comet McNaught, yet?
It looks to be quite grand. Already, the tail is beginning to sweep away from the sun's atmosphere. |
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| Circulator 38 |
Posted: Sat Jan 13, 2007 7:08 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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High Flier
Joined: 18 Jan 2005
Posts: 4712
Location: The city that rhymes with fun
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Century 2, Quatrain 41
The great star will burn for seven days,
The cloud will cause two suns to appear:
The big mastiff will howl all night
When the great pontiff will change country.
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disclaimer: I do not necessarily agree with any article I post; I may be 100% opposed. I post for information only.
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| Guest |
Posted: Sat Jan 13, 2007 7:56 pm Post subject: Remember Comet V1? Now we have Comet C/2006 P1 (McNaught)
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