jao@valid.UUCP (John Oswalt) (02/05/86)
I know that Uranus's axis of rotation is tilted ~90 degrees from the
normal, perpendicular-to-ecliptic axis. This means that the axis
lies in the plane of the ecliptic, but which way does it point?
Does it point at the sun, or is it tangent to the orbit, or some
angle in between?
--
John Oswalt (..!{hplabs,amd,pyramid,ihnp4}!pesnta!valid!jao)jp@lanl.UUCP (02/07/86)
>I know that Uranus's axis of rotation is tilted ~90 degrees from the >normal, perpendicular-to-ecliptic axis. This means that the axis >lies in the plane of the ecliptic, but which way does it point? >Does it point at the sun, or is it tangent to the orbit, or some >angle in between? The answer to the last question is: Yes.
u553691091ea@ucdavis.UUCP (Tim Underwood) (02/07/86)
> I know that Uranus's axis of rotation is tilted ~90 degrees from the > normal, perpendicular-to-ecliptic axis. This means that the axis > lies in the plane of the ecliptic, but which way does it point? > Does it point at the sun, or is it tangent to the orbit, or some > angle in between? > > > > -- > John Oswalt (..!{hplabs,amd,pyramid,ihnp4}!pesnta!valid!jao) * Uranus' pole points towards the earth/sun at this time. In about 44 years ( I think it's orbital period is about 176 years) , it's pole will point tangent to it's orbit (i.e. it's pole, like ours, points towards some point in space reguardless of it's position in it's orbit). In 88 years Uranus' other pole will point towards the earth. As an extra, What is the Ulysses probe? Will it also go to Jupiter? Tim Underwood University of California, Davis Astronomy Club :wq . A A ** REPLACE THIS LINE WITH YOUR MESSAGE ***
wyatt@cfa.UUCP (Bill Wyatt) (02/07/86)
> I know that Uranus's axis of rotation is tilted ~90 degrees from the > normal, perpendicular-to-ecliptic axis. This means that the axis > lies in the plane of the ecliptic, but which way does it point? > Does it point at the sun, or is it tangent to the orbit, or some > angle in between? > John Oswalt (..!{hplabs,amd,pyramid,ihnp4}!pesnta!valid!jao) Well, it depends... Just as Earth's axis points at one point (more or less the star Polaris), Uranus's pole points at one place (I don't know just where). As Earth goes around the sun, the angle between the sun and the Earth's axis changes, causing seasons. The same thing happens to Uranus, except the Uranian `year' is ~84 years. The extreme axial tilt (currently the `north' pole is pointing essentially right at the sun) means that 1/2 of the planet (i.e. the opposite polar region) spends ~21 years in total darkness. Must make for some interesting climate cycles! -- Bill UUCP: {seismo|ihnp4|cmcl2}!harvard!talcott!cfa!wyatt Wyatt ARPA: wyatt%cfa.UUCP@harvard.HARVARD.EDU
bl@hplabsb.UUCP (02/08/86)
> I know that Uranus's axis of rotation is tilted ~90 degrees from the > normal, perpendicular-to-ecliptic axis. This means that the axis > lies in the plane of the ecliptic, but which way does it point? > Does it point at the sun, or is it tangent to the orbit, or some > angle in between? At what time of Uranus's year are you interested in? During the summer in the northern hemisphere, the north pole points towards the sun. During the winter, it points away from the sun.
henry@utzoo.UUCP (Henry Spencer) (02/09/86)
> I know that Uranus's axis of rotation is tilted ~90 degrees from the > normal, perpendicular-to-ecliptic axis. This means that the axis > lies in the plane of the ecliptic, but which way does it point? > Does it point at the sun, or is it tangent to the orbit, or some > angle in between? All of the above, depending on when you catch it. The axis points in a (roughly) fixed direction in space as the planet goes around the sun. At the moment Uranus's south pole points roughly at the sun; half an orbit later, the north pole will point at the sun. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
steve@jplgodo.UUCP (Steve Schlaifer x3171 156/224) (02/09/86)
In article <111@valid.UUCP>, jao@valid.UUCP (John Oswalt) writes: > I know that Uranus's axis of rotation is tilted ~90 degrees from the > normal, perpendicular-to-ecliptic axis. This means that the axis > lies in the plane of the ecliptic, but which way does it point? > Does it point at the sun, or is it tangent to the orbit, or some > angle in between? Right now, the spin axis is pointing more or less directly at the sun. As Uranus moves around the sun, however, the spin axis keeps its same orientation in space. This means that in about another quarter of its orbital period the spin axis will be at right angles to the direction to the sun. Similarly, in about half of its orbital period from now, the spin axis will again be pointing at the sun but with the opposite end in the sunward direction. The orbital period of Uranus (a Uranian year) is about 84 Terran years. -- ...smeagol\ Steve Schlaifer ......wlbr->!jplgodo!steve Advance Projects Group, Jet Propulsion Labs ....group3/ 4800 Oak Grove Drive, M/S 156/204 Pasadena, California, 91109 +1 818 354 3171
dave@quest.UUCP (David Messer) (02/09/86)
> I know that Uranus's axis of rotation is tilted ~90 degrees from the > normal, perpendicular-to-ecliptic axis. This means that the axis > lies in the plane of the ecliptic, but which way does it point? > Does it point at the sun, or is it tangent to the orbit, or some > angle in between? All of the above. The direction of the axis of rotation remains constant while Uranus revolves around the sun so sometimes the north pole is pointed at the sun, sometimes the south pole and sometimes the equator. I haven't checked so I am not sure but I believe that the north pole is currently pointing roughly sunward. -- David Messer UUCP: ...ihnp4!quest!dave ...ihnp4!encore!vaxine!spark!14!415!sysop FIDO: 14/415 (SYSOP)
steve@jplgodo.UUCP (Steve Schlaifer x3171 156/224) (02/10/86)
In article <161@ucdavis.UUCP>, u553691091ea@ucdavis.UUCP (Tim Underwood) writes: > > I know that Uranus's axis of rotation is tilted ~90 degrees from the > > normal, perpendicular-to-ecliptic axis. This means that the axis > > lies in the plane of the ecliptic, but which way does it point? > > ............ > > Uranus' pole points towards the earth/sun at this time. In about 44 years ( I > think it's orbital period is about 176 years) The orbital period is more like 84 years not 176 so the 44 above should be 21. > , it's pole will point tangent to it's orbit (i.e. it's pole, like ours, > points towards some point in space reguardless of it's position in it's > orbit). In 88 years Uranus' other pole will point towards the earth. Same here. The 88 should be 42. > As an extra, What is the Ulysses probe? Will it also go to Jupiter? Ulysses is a rename of the (joint ESA/NASA I think) International Solar Polar Mission (ISPM). It was originally designed as two spacecraft which would pass over the Sun's north and south poles at the same time but funding constraints eliminated one of the spacecraft. The current design calls for a single spacecraft to pass over the Sun's south pole. To get out of the ecliptic plane and over the pole, the mission design calls for a Jupiter gravity assist (flyby). -- ...smeagol\ Steve Schlaifer ......wlbr->!jplgodo!steve Advance Projects Group, Jet Propulsion Labs ....group3/ 4800 Oak Grove Drive, M/S 156/204 Pasadena, California, 91109 +1 818 354 3171