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Gliese 581 d

2008-04-08T18:31:01Z

87.123.34.228:

{{Planetbox begin
| name = Gliese 581 d
}}
{{Planetbox image
| image = [[Image:Gliese 581 d-v1.jpg|270px]]
| caption = Artistic representation of a panoramic view of <br>Gliese 581 d, showing speculative moons.
}}
{{Planetbox star
| star = [[Gliese 581]]
| constell = [[Libra (constellation)|Libra]]
| RA = {{RA|15|19|26}}
| DEC = {{DEC|−07|43|20}}
| dist_ly = 20.4
| dist_pc = 6.27
| class = M2.5V
}}
{{Planetbox orbit
| period = 84.4
| semimajor = .25
| eccentricity = .2
| ang_dist = 39.936
| t_peri = 2452954.1
| semi-amp = 2.67
}}
{{Planetbox character
| mass_earth = >7.7
}}
{{Planetbox discovery
| discovery_date = [[2007-04-24]]
| discoverers = [[Stéphane Udry|Udry]] et al.
| discovery_method = Radial velocity
| discovery_status = unpublished
}}
{{Planetbox end}}

'''Gliese 581 d''' ({{pronEng|ˈgliːzə}}), also known as '''Wolf 562 d''' and '''HIP 74995 d''', is a "[[super-Earth]]" or large [[terrestrial planet| terrestrial]] [[extrasolar planet]] orbiting the [[red dwarf]] [[star]] [[Gliese 581]].<br />
Gliese 581 d is near the outer edge of the habitable zone.

== Discovery ==
The planet was discovered by the team of [[Stéphane Udry]] of the Geneva Observatory in [[Switzerland]] using the [[HARPS]] instrument on the [[European Southern Observatory]] 3.6 meter telescope in [[La Silla]], [[Chile]] on [[April 24]], [[2007]]. Udry's team employed the [[radial velocity]] technique, in which the size and mass of a planet are determined based on the small perturbations it induces in its parent star’s orbit via gravity.

The team is confident that the planet exists but recognizes that unlikely events could mimic its existence. They believe the issue will be settled by upcoming studies.

== Climate and habitability ==
Although Gliese 581 d orbits outside the theoretical [[habitable zone]] of its star, scientists surmise that conditions on the planet may be conducive to supporting life[http://www.space.com/scienceastronomy/070618_mm_gliese_581d.html]. Scientists originally believed that Gliese 581 d would in fact be too cold for liquid water to exist, and therefore could not support life as we understand it. However, due to a theorized [[greenhouse effect]], research now suggests that atmospheric conditions on the planet could create temperatures at which water can exist, and therefore the planet may be capable of supporting life. However, these conditions are based on models of the planet, and have not been directly observed.

==References==
<references />

== External links ==
*[http://vo.obspm.fr/exoplanetes/encyclo/planet.php?p1=Gl+581&p2=d '''Extrasolar Planets Encyclopaedia''': Gl 581 d]
*[http://simbad.u-strasbg.fr/sim-id.pl?protocol=html&Ident=gl+581&NbIdent=1&Radius=10&Radius.unit=arcmin&CooFrame=FK5&CooEpoch=2000&CooEqui=2000&output.max=all&o.catall=on&output.mesdisp=N&Bibyear1=1983&Bibyear2=2005&Frame1=FK5&Frame2=FK4&Frame3=G&Equi1=200 '''SIMBAD''': V* HO Lib -- Variable Star]

{{Gliese 581}}

[[Category:Extrasolar planets]]
[[Category:Libra constellation]]

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[[ko:글리제 581d]]
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Wolf pack

2006-05-22T07:10:09Z

87.123.188.151:

:''This article describes the system of submarine warfare. For other meanings, see [[wolfpack]].''

The term '''wolf pack''' refers to the mass-attack tactics against [[convoy]]s used by [[U-boat]]s of the [[Kriegsmarine]] during the [[Second Battle of the Atlantic|Battle of the Atlantic]] and [[submarine]]s of the [[United States Navy]] against [[Japan]]ese shipping in the [[Pacific Ocean]] in [[World War II]].

[[Karl Dönitz]] used the term ''Rudel'' to describe his strategy of submarine warfare – ''Rudel'' can be translated as "pack" of animals, but it also translates as herd, pride, or swarm, depending on the type of animal associated with the word, so this has become known in [[English language|English]] as "wolf pack" (''Wolfsrudel''), a more accurate metaphoric, but not literal, translation.

U-boat movements were controlled by the ''[[Befehlshaber der Unterseeboote]]'' much more closely than American submarines, which were given tremendous independence once on patrol. Accordingly, U-boats usually patrolled separately, often strung out in co-ordinated lines across likely convoy routes, only being ordered to congregate after one located a convoy and alerted BdU, so a ''Rudel'' consisted of as many [[U-boat]]s as could reach the scene of the attack. American wolf packs, usually comprised three boats that patrolled in close company, organized before they left port under the command of the senior captain of the three. [[Charles Momsen|"Swede" Momsen]] devised the tactics and led the first American wolf pack to sea in October [[1943]].

Wolf packs fell out of use during the [[Cold War]]; modern submarines being so much more maneuverable and destructive than those of [[World War II]] that there is no need for them to hunt in packs. Instead, the [[United States Navy]] deploys its attack submarines on individual patrols, with the exception of one or (rarely) two attack submarines in each carrier group. American ballistic missile submarines have always operated alone. (Soviet ballistic missile submarines operated in well-protected [[bastion (submarine)|bastion]]s.) However, with the opening shots of the [[2003 invasion of Iraq]] in March 2003, the term "wolf pack" was brought back into use to describe the fleet of American and British [[nuclear submarine]]s which operated together in the [[Red Sea]] to fire [[BGM-109 Tomahawk|tomahawk missiles]] at [[Iraq]]. [[USS Providence (SSN-719)|USS ''Providence'']] was the first boat to fire its entire load of missiles and earn the nickname "Big Dog of the Red Sea Wolf Pack."

== References ==
* Karl Dönitz, ''Memoirs: Ten Years and Twenty Days'' (New York: World Publishing Company, 1958)

* Peter Maas, ''The Terrible Hours: The Man Behind the Greatest Submarine Rescue in History'' (HarperCollins New York, 1999)

* E. B. Potter and Chester W. Nimitz, eds; ''Sea Power: A Naval History'' (Englewood Cliffs, N.J.: Prentice-Hall, 1960)

[[Category:Naval warfare]]

[[de:Wolfsrudeltaktik]]
[[ja:群狼作戦]]
[[sr:Вучји чопор]]

Wolf pack

2006-05-22T07:09:49Z

87.123.188.151:

:''This article describes the system of submarine warfare. For other meanings, see [[wolfpack]].''

The term '''wolf pack''' refers to the mass-attack tactics against [[convoy]]s used by [[U-boat]]s of the [[Kriegsmarine]] during the [[Second Battle of the Atlantic|Battle of the Atlantic]] and [[submarine]]s of the [[United States Navy]] against [[Japan]]ese shipping in the [[Pacific Ocean]] in [[World War II]].

[[Karl Dönitz]] used the term ''Rudel'' to describe his strategy of submarine warfare – ''Rudel'' can be translated as "pack" of animals, but it also translates as herd, pride, or swarm, depending on the type of animal associated with the word, so this has become known in [[English language|English]] as "wolf pack" (''wolfsrudel''), a more accurate metaphoric, but not literal, translation.

U-boat movements were controlled by the ''[[Befehlshaber der Unterseeboote]]'' much more closely than American submarines, which were given tremendous independence once on patrol. Accordingly, U-boats usually patrolled separately, often strung out in co-ordinated lines across likely convoy routes, only being ordered to congregate after one located a convoy and alerted BdU, so a ''Rudel'' consisted of as many [[U-boat]]s as could reach the scene of the attack. American wolf packs, usually comprised three boats that patrolled in close company, organized before they left port under the command of the senior captain of the three. [[Charles Momsen|"Swede" Momsen]] devised the tactics and led the first American wolf pack to sea in October [[1943]].

Wolf packs fell out of use during the [[Cold War]]; modern submarines being so much more maneuverable and destructive than those of [[World War II]] that there is no need for them to hunt in packs. Instead, the [[United States Navy]] deploys its attack submarines on individual patrols, with the exception of one or (rarely) two attack submarines in each carrier group. American ballistic missile submarines have always operated alone. (Soviet ballistic missile submarines operated in well-protected [[bastion (submarine)|bastion]]s.) However, with the opening shots of the [[2003 invasion of Iraq]] in March 2003, the term "wolf pack" was brought back into use to describe the fleet of American and British [[nuclear submarine]]s which operated together in the [[Red Sea]] to fire [[BGM-109 Tomahawk|tomahawk missiles]] at [[Iraq]]. [[USS Providence (SSN-719)|USS ''Providence'']] was the first boat to fire its entire load of missiles and earn the nickname "Big Dog of the Red Sea Wolf Pack."

== References ==
* Karl Dönitz, ''Memoirs: Ten Years and Twenty Days'' (New York: World Publishing Company, 1958)

* Peter Maas, ''The Terrible Hours: The Man Behind the Greatest Submarine Rescue in History'' (HarperCollins New York, 1999)

* E. B. Potter and Chester W. Nimitz, eds; ''Sea Power: A Naval History'' (Englewood Cliffs, N.J.: Prentice-Hall, 1960)

[[Category:Naval warfare]]

[[de:Wolfsrudeltaktik]]
[[ja:群狼作戦]]
[[sr:Вучји чопор]]