Event – Comet 17P/Holmes
All over the world astronomy enthusiasts have been stunned and surprised by the weirdest new object appearing in the sky these days. It's one of the brightest objects visible and if you know where to look, without a fuss it's easy to spot with your eyes alone. A small and very faint comet has surprised observers around the world by overnight becoming bright enough to see with the unaided eye. Observers worldwide had no trouble spotting Comet Holmes even through the full moonlight on the evening of October 25, 2007.
About a week ago periodic Comet 17P/Holmes brightness suddenly rocketed by nearly a million times virtually overnight. The comet erupted from a very dim magnitude 17 to about magnitude 2½. On an astronomer’s scale, smaller numbers mean brighter objects. From urban locations, a 3rd-magnitude object might be hidden by light pollution, but even under urban skies Comet Holmes would be clearly visible. Within a day its star-like nucleus had expanded into a perfectly round, bright little disk visible in binoculars and telescopes.
The first person to notice the out burst of Comet Holmes, according to Central Bureau for Astronomical Telegrams was J. A. Henriquez Santana at Tenerife, Canary Islands, October 23–24, 2007. The comet was then about 8th magnitude, but within minutes Ramon Naves and colleagues in Barcelona, Spain, caught it at magnitude 7.3. But it became easily visible to the naked eye as a bright yellow "star" in the northeast sky within Perseus. 17P/Holmes appeared as the third brightest "star" in Perseus by October 25.
History
Comet 17P/Holmes was discovered in November 6, 1892 by Edwin Holmes, in London England, whilst doing his regular observations of the Andromeda Galaxy (M31). That time it was no brighter than magnitude 17 in mid October—that's about 25,000 times fainter than the faintest star that can normally be seen without any optical aid. In order to view an object this faint, one would need a moderately large telescope.
The comet was undergoing magnitude changes similar to the 2007 outburst. 17P/Holmes brightened to about magnitude 4 or 5 and then faded over several weeks. The first elliptical orbits were independently calculated by Heinrich Kreutz and George Mary Searle. The 1899 and 1906 appearances were observed, but the comet was lost after 1906 until recovered on July 16, 1964 by Elizabeth Roemer (US Naval Observatory) and the comet has been observed on every return since.
Comet 17P/Holmes is part of Jupiter's "family" of comets—a group in which the far end of their respective orbits (aphelia) cluster around the orbit of Jupiter and takes 6.88 years to make one circuit around the Sun.
What are Comets?
Comets are one of most interesting obejects in the univers because of its life style. Think of a comet as a big, dirty, gassy snowball. Comets are formed in the ring of rocks, dust, and ice that orbits the Sun beyond Pluto called the Kuiper Belt. They form when rocks, dust, and ice condense. As a comet grows larger, it starts to be pulled towards and around the Sun. They take many years to go around the Sun – from a few dozen years to many thousands of years. This is because they start to orbit the sun from very far away. They make long, egg-shaped orbits around the Sun instead of almost circular ones like the planets.
When comets are very far away from the Sun, they are covered in a coating of icy, black rocks and dust. As a comet approaches the Sun, however, the ice starts to melt. This creates large amounts of water and gas that break through the coating, freeing some of the dust and rocks. Sometimes this water, gas, rocks, and dust can be seen from the Earth as one or two tails streaming away from the comet. Even when only one tail can be seen, there are two, one made from the lighter gas and water, and the other from the rocks, dust, and chunks of ice. Comets themselves are usually between a few miles and several hundred miles in size, but their tails can be several million miles long.
How to observe the comet 17P/Holmes
The comets that can be seen in the sky without telescopes are unusual. You might only have the chance to see one once or twice during your life. Most comets can only be seen with a telescope. But now we have got the opportunity to fullfill a lifetime experience with the comet 17P/Holmes. Many astronomy enthusiasts and general public around the world so keen on seeing this spectacular fussy object in the sky.
These days it’s visible in the sky from around 8pm to 4am in the morning (in local time). Around 11pm it’ll be on the Meridian line (an imaginary line which connects North and South in the sky) - visually you have to look straight up and then bit towards North. It lies on the star constellation Perseus which is to the North-west of the beautiful Pleiades (M45). By this time Moon is setting in the west, so that you will get good views. At the time I’m writing this article it lies about 1.5 astronomical units away from us. With a help of a star chart you’ll be easily able to find Perseus. (Free star charts can be obtain from www.skymaps.com)
But don’t expect to see a tail as in you have seen pictures of comets in books and magazines. Because the tail is pointing nearly away from us in space — we're looking down its length — since the comet is nearly on the opposite side of Earth from the Sun. From the comet's viewpoint, the Earth and Sun are only about 15° apart, and this phase angle will stay small for many months. So we'll keep looking down the tail.
But you can see a round, sharp-edged disk with a bright core in binoculars and telescopes. For naked eye it’ll look like a yellowish star. Comet Holmes is likely to remain bright and continue to enlarge in the coming days, as it makes its way slowly westward across Perseus. The comet will stay in Perseus all the way into next March.
Since this is a life time opportunity, you might not want to miss it. I would like to hear your views of the comets if any of you get a chance to observe it and would willing to give tips and help out anyone with a good telescope or binocular who would like to do advance observation.
Though it’s very much weather permitting let’s hope for clear skies!
Thilina Heenatigala
General Secretary
Sri Lanka Astronomical Association
All over the world astronomy enthusiasts have been stunned and surprised by the weirdest new object appearing in the sky these days. It's one of the brightest objects visible and if you know where to look, without a fuss it's easy to spot with your eyes alone. A small and very faint comet has surprised observers around the world by overnight becoming bright enough to see with the unaided eye. Observers worldwide had no trouble spotting Comet Holmes even through the full moonlight on the evening of October 25, 2007.
About a week ago periodic Comet 17P/Holmes brightness suddenly rocketed by nearly a million times virtually overnight. The comet erupted from a very dim magnitude 17 to about magnitude 2½. On an astronomer’s scale, smaller numbers mean brighter objects. From urban locations, a 3rd-magnitude object might be hidden by light pollution, but even under urban skies Comet Holmes would be clearly visible. Within a day its star-like nucleus had expanded into a perfectly round, bright little disk visible in binoculars and telescopes.
The first person to notice the out burst of Comet Holmes, according to Central Bureau for Astronomical Telegrams was J. A. Henriquez Santana at Tenerife, Canary Islands, October 23–24, 2007. The comet was then about 8th magnitude, but within minutes Ramon Naves and colleagues in Barcelona, Spain, caught it at magnitude 7.3. But it became easily visible to the naked eye as a bright yellow "star" in the northeast sky within Perseus. 17P/Holmes appeared as the third brightest "star" in Perseus by October 25.
History
Comet 17P/Holmes was discovered in November 6, 1892 by Edwin Holmes, in London England, whilst doing his regular observations of the Andromeda Galaxy (M31). That time it was no brighter than magnitude 17 in mid October—that's about 25,000 times fainter than the faintest star that can normally be seen without any optical aid. In order to view an object this faint, one would need a moderately large telescope.
The comet was undergoing magnitude changes similar to the 2007 outburst. 17P/Holmes brightened to about magnitude 4 or 5 and then faded over several weeks. The first elliptical orbits were independently calculated by Heinrich Kreutz and George Mary Searle. The 1899 and 1906 appearances were observed, but the comet was lost after 1906 until recovered on July 16, 1964 by Elizabeth Roemer (US Naval Observatory) and the comet has been observed on every return since.
Comet 17P/Holmes is part of Jupiter's "family" of comets—a group in which the far end of their respective orbits (aphelia) cluster around the orbit of Jupiter and takes 6.88 years to make one circuit around the Sun.
What are Comets?
Comets are one of most interesting obejects in the univers because of its life style. Think of a comet as a big, dirty, gassy snowball. Comets are formed in the ring of rocks, dust, and ice that orbits the Sun beyond Pluto called the Kuiper Belt. They form when rocks, dust, and ice condense. As a comet grows larger, it starts to be pulled towards and around the Sun. They take many years to go around the Sun – from a few dozen years to many thousands of years. This is because they start to orbit the sun from very far away. They make long, egg-shaped orbits around the Sun instead of almost circular ones like the planets.
When comets are very far away from the Sun, they are covered in a coating of icy, black rocks and dust. As a comet approaches the Sun, however, the ice starts to melt. This creates large amounts of water and gas that break through the coating, freeing some of the dust and rocks. Sometimes this water, gas, rocks, and dust can be seen from the Earth as one or two tails streaming away from the comet. Even when only one tail can be seen, there are two, one made from the lighter gas and water, and the other from the rocks, dust, and chunks of ice. Comets themselves are usually between a few miles and several hundred miles in size, but their tails can be several million miles long.
How to observe the comet 17P/Holmes
The comets that can be seen in the sky without telescopes are unusual. You might only have the chance to see one once or twice during your life. Most comets can only be seen with a telescope. But now we have got the opportunity to fullfill a lifetime experience with the comet 17P/Holmes. Many astronomy enthusiasts and general public around the world so keen on seeing this spectacular fussy object in the sky.
These days it’s visible in the sky from around 8pm to 4am in the morning (in local time). Around 11pm it’ll be on the Meridian line (an imaginary line which connects North and South in the sky) - visually you have to look straight up and then bit towards North. It lies on the star constellation Perseus which is to the North-west of the beautiful Pleiades (M45). By this time Moon is setting in the west, so that you will get good views. At the time I’m writing this article it lies about 1.5 astronomical units away from us. With a help of a star chart you’ll be easily able to find Perseus. (Free star charts can be obtain from www.skymaps.com)
But don’t expect to see a tail as in you have seen pictures of comets in books and magazines. Because the tail is pointing nearly away from us in space — we're looking down its length — since the comet is nearly on the opposite side of Earth from the Sun. From the comet's viewpoint, the Earth and Sun are only about 15° apart, and this phase angle will stay small for many months. So we'll keep looking down the tail.
But you can see a round, sharp-edged disk with a bright core in binoculars and telescopes. For naked eye it’ll look like a yellowish star. Comet Holmes is likely to remain bright and continue to enlarge in the coming days, as it makes its way slowly westward across Perseus. The comet will stay in Perseus all the way into next March.
Since this is a life time opportunity, you might not want to miss it. I would like to hear your views of the comets if any of you get a chance to observe it and would willing to give tips and help out anyone with a good telescope or binocular who would like to do advance observation.
Though it’s very much weather permitting let’s hope for clear skies!
Thilina Heenatigala
General Secretary
Sri Lanka Astronomical Association
Posts
0 comments:
Post a Comment