Herschel Virginis
Posted: Sun Jul 10, 2005 1:12 pm
Here is a link which might be of interest to some of you:
http://www.etsu.edu/physics/etsuobs/sta ... epplu.html
Here is an extract which seems particularly interesting:
Unlike Pluto, Uranus and Neptune require just a bare minimum of optical aid. What's really surprising is how long it took for astronomers to discover these big denizens of the outer solar system, each about one-sixth as massive as the planet Saturn.
In fact, Galileo himself came very close to discovering Uranus with his 1-inch telescope as he watched the nightly shifts in Jupiter's satellites and noticed occasional field stars. Uranus was just 2? from Jupiter in early February 1610, the second month of his observations. Galileo did plot much fainter Neptune on January 28, 1613, believing it to be a faint star near Jupiter. Careful scientist that he was, he even jotted down that it seemed to have moved since the previous night!
On at least 22 occasions before 1781, the year William Herschel finally recognized Uranus as a new planet, other astronomers mistook it for a star. John Flamsteed even named it 34 Tauri. And there's a lingering puzzle about the identity of a 6th-magnitude star recorded two millenniums ago in Ptolemy's Almagest. The nearest candidate star is 76 Virginis, 1.3? away. But the astronomical historian Keith P. Hertzog has pointed out that Uranus passed 1/2? from the very spot in 128 B.C., about the time when Ptolemy's predecessor, Hipparchus, was making the observations on which the Almagest was based.
Is this a stretch? Did the ancient Greeks observe Uranus? Maybe so, maybe not. But there's no dispute that Uranus really is a naked-eye planet, especially on moonless nights far from any city lights. While counting meteors, the 19th-century English amateur William F. Denning liked to keep tabs on Uranus for months at a time, noting its night-by-night shifts among the stars.
Here is another link:
http://www.sptimes.com/2004/03/21/Persp ... r_sp.shtml
And another extract:
There may be 10 planets now. Or perhaps there are only eight. Or hundreds.
Last week a group of scientists announced they had discovered a very distant, Plutolike object in an vast, elliptical orbit of the sun. It is the most distant object ever found orbiting the sun, some 8-billion miles away at its closest point, 84-billion at its most remote. Each solar orbit lasts about 10,500 years.
Were you standing on this remote rock, the sun would appears so small from even the closest part of the orbit that you could block it out with the head of a pin, said Mike Brown of the California Institute of Technology and leader of the team that made the discovery.
The icy orb will continue to approach the sun for the next 72 years or so, then begin its long journey out to the far reaches of the solar system. The last time it was this close to the sun, Earth was just coming out of the last ice age, said Brown. "The next time it comes back, the world might again be a completely different place."
The new discovery's official identification is 2003 VB12 but Brown and his team dubbed it Sedna, for the Inuit goddess of the ocean. They did not claim planetary status for their discovery, but noted if Pluto is a planet, then Sedna deserves the title, too.
This reignites an old and surprisingly controversial issue: Just what is a planet anyway?
"Tell me about it," grumbled Marsden, who put aside his mnemonics and became a widely respected astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "This has been going on a long time."
The problem is that there never has been a precise definition of a planet, and so there is no agreement on how many there are.
Since 1930, when Pluto was discovered, most school texts list the familiar nine. But there is a growing belief among cosmologists that Pluto is so distant and so different from the other eight that it is something else altogether - probably the largest of many similar bodies in the so-called Kuiper Belt, a ring of icy, rocky objects circling the sun in an orbit beyond Neptune. The Kuiper Belt is thought to be remnants of the formation of the solar system and the source of comets.
Sedna is also a Kuiper Belt Object, or KBO. If Sedna is to be a planet, that would make 10, and the number would likely grow as modern astronomical equipment locates similar objects in the Kuiper Belt. But if Sedna is denied planet status, then should Pluto, similar in composition and only a little larger, be dropped from the list? Many astronomers think so.
"We're not calling (Sedna) the tenth planet," said Marsden. "It should be called 2003 VB12. But then we don't think Pluto should be a planet either."
What excites astronomers about Sedna is the mystery of how it came to be so distant from the sun, far from where the eight major planets formed. They also wonder about its peculiar elliptical orbit, "unique among Kuiper Belt Objects," according to astronomer David Jewitt of the Institute for Astronomy at the University of Hawaii.
The orbit is "weird," said Marsden, noting that the eight major planets in this solar system have orbits that may be slightly elliptical but are essentially circular. "Until you can answer how it got there, where it came from, can you really call it a planet?"
The planetary census has changed over the years, he noted. Textbooks in 1845 identified 11. Some were dropped over the years, however, and Pluto was added as the ninth in 1930.
"It seemed reasonable enough at the time to call Pluto the ninth planet," said Marsden. "Percival Lowell had predicted its presence, and when it was found he touted it as Earth-sized. It was a guess and it was erroneous. We later learned it's a good deal smaller than Earth.
"In 1978 we got a good hold on Pluto's size, and the final straw for Pluto's planethood came in 1994 when we discovered there are lots of other objects just like it - at least 60 or so. We call them Plutinos."
Brown, Sedna's discoverer, also said Pluto should be reclassified.
"Either Pluto is not a planet, or many other things are planets," he told Space.com. "Which is a better choice? I want my planets to be more special, not less special, so I favor Pluto not being a planet. Emotionally, though, I have to admit that I have grown up thinking Pluto as this special oddball planet at the edge of the solar system. While I now know scientifically that Pluto is less special, it's still hard to let go."
Help may be on the way. The International Astrophysical Union - the body that must okay the planetary status of 2003 VB12 - is forming a small committee to try to establish what a planet is, Marsden said.
"If you accept that there are eight, you have four terrestrial and four gas giants, nicely separated, generally on the same plane. Their orbits are circular. They nicely fit together as major planets.
"You can call all these other (Kuiper Belt) objects planets if you want to," he said, "but I like to think of planets as something scarce and unusual."
So, where does the desperate student go for help? Maybe back to mnemonics.
"If you don't want to include Pluto - and I don't," said Marsden, "just change the word "nine' to the word "nothing' and leave it at that. "My Very Energetic Mother Just Sent Us Nothing.' No Pizza."
But if Sedna is eventually declared a planet?
"You come up with something for Sedna," he said. "I don't think it's a planet anyway."
http://www.etsu.edu/physics/etsuobs/sta ... epplu.html
Here is an extract which seems particularly interesting:
Unlike Pluto, Uranus and Neptune require just a bare minimum of optical aid. What's really surprising is how long it took for astronomers to discover these big denizens of the outer solar system, each about one-sixth as massive as the planet Saturn.
In fact, Galileo himself came very close to discovering Uranus with his 1-inch telescope as he watched the nightly shifts in Jupiter's satellites and noticed occasional field stars. Uranus was just 2? from Jupiter in early February 1610, the second month of his observations. Galileo did plot much fainter Neptune on January 28, 1613, believing it to be a faint star near Jupiter. Careful scientist that he was, he even jotted down that it seemed to have moved since the previous night!
On at least 22 occasions before 1781, the year William Herschel finally recognized Uranus as a new planet, other astronomers mistook it for a star. John Flamsteed even named it 34 Tauri. And there's a lingering puzzle about the identity of a 6th-magnitude star recorded two millenniums ago in Ptolemy's Almagest. The nearest candidate star is 76 Virginis, 1.3? away. But the astronomical historian Keith P. Hertzog has pointed out that Uranus passed 1/2? from the very spot in 128 B.C., about the time when Ptolemy's predecessor, Hipparchus, was making the observations on which the Almagest was based.
Is this a stretch? Did the ancient Greeks observe Uranus? Maybe so, maybe not. But there's no dispute that Uranus really is a naked-eye planet, especially on moonless nights far from any city lights. While counting meteors, the 19th-century English amateur William F. Denning liked to keep tabs on Uranus for months at a time, noting its night-by-night shifts among the stars.
Here is another link:
http://www.sptimes.com/2004/03/21/Persp ... r_sp.shtml
And another extract:
There may be 10 planets now. Or perhaps there are only eight. Or hundreds.
Last week a group of scientists announced they had discovered a very distant, Plutolike object in an vast, elliptical orbit of the sun. It is the most distant object ever found orbiting the sun, some 8-billion miles away at its closest point, 84-billion at its most remote. Each solar orbit lasts about 10,500 years.
Were you standing on this remote rock, the sun would appears so small from even the closest part of the orbit that you could block it out with the head of a pin, said Mike Brown of the California Institute of Technology and leader of the team that made the discovery.
The icy orb will continue to approach the sun for the next 72 years or so, then begin its long journey out to the far reaches of the solar system. The last time it was this close to the sun, Earth was just coming out of the last ice age, said Brown. "The next time it comes back, the world might again be a completely different place."
The new discovery's official identification is 2003 VB12 but Brown and his team dubbed it Sedna, for the Inuit goddess of the ocean. They did not claim planetary status for their discovery, but noted if Pluto is a planet, then Sedna deserves the title, too.
This reignites an old and surprisingly controversial issue: Just what is a planet anyway?
"Tell me about it," grumbled Marsden, who put aside his mnemonics and became a widely respected astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "This has been going on a long time."
The problem is that there never has been a precise definition of a planet, and so there is no agreement on how many there are.
Since 1930, when Pluto was discovered, most school texts list the familiar nine. But there is a growing belief among cosmologists that Pluto is so distant and so different from the other eight that it is something else altogether - probably the largest of many similar bodies in the so-called Kuiper Belt, a ring of icy, rocky objects circling the sun in an orbit beyond Neptune. The Kuiper Belt is thought to be remnants of the formation of the solar system and the source of comets.
Sedna is also a Kuiper Belt Object, or KBO. If Sedna is to be a planet, that would make 10, and the number would likely grow as modern astronomical equipment locates similar objects in the Kuiper Belt. But if Sedna is denied planet status, then should Pluto, similar in composition and only a little larger, be dropped from the list? Many astronomers think so.
"We're not calling (Sedna) the tenth planet," said Marsden. "It should be called 2003 VB12. But then we don't think Pluto should be a planet either."
What excites astronomers about Sedna is the mystery of how it came to be so distant from the sun, far from where the eight major planets formed. They also wonder about its peculiar elliptical orbit, "unique among Kuiper Belt Objects," according to astronomer David Jewitt of the Institute for Astronomy at the University of Hawaii.
The orbit is "weird," said Marsden, noting that the eight major planets in this solar system have orbits that may be slightly elliptical but are essentially circular. "Until you can answer how it got there, where it came from, can you really call it a planet?"
The planetary census has changed over the years, he noted. Textbooks in 1845 identified 11. Some were dropped over the years, however, and Pluto was added as the ninth in 1930.
"It seemed reasonable enough at the time to call Pluto the ninth planet," said Marsden. "Percival Lowell had predicted its presence, and when it was found he touted it as Earth-sized. It was a guess and it was erroneous. We later learned it's a good deal smaller than Earth.
"In 1978 we got a good hold on Pluto's size, and the final straw for Pluto's planethood came in 1994 when we discovered there are lots of other objects just like it - at least 60 or so. We call them Plutinos."
Brown, Sedna's discoverer, also said Pluto should be reclassified.
"Either Pluto is not a planet, or many other things are planets," he told Space.com. "Which is a better choice? I want my planets to be more special, not less special, so I favor Pluto not being a planet. Emotionally, though, I have to admit that I have grown up thinking Pluto as this special oddball planet at the edge of the solar system. While I now know scientifically that Pluto is less special, it's still hard to let go."
Help may be on the way. The International Astrophysical Union - the body that must okay the planetary status of 2003 VB12 - is forming a small committee to try to establish what a planet is, Marsden said.
"If you accept that there are eight, you have four terrestrial and four gas giants, nicely separated, generally on the same plane. Their orbits are circular. They nicely fit together as major planets.
"You can call all these other (Kuiper Belt) objects planets if you want to," he said, "but I like to think of planets as something scarce and unusual."
So, where does the desperate student go for help? Maybe back to mnemonics.
"If you don't want to include Pluto - and I don't," said Marsden, "just change the word "nine' to the word "nothing' and leave it at that. "My Very Energetic Mother Just Sent Us Nothing.' No Pizza."
But if Sedna is eventually declared a planet?
"You come up with something for Sedna," he said. "I don't think it's a planet anyway."
