dipper@utastro.UUCP (Debbie Byrd) (03/28/85)
If you look carefully, you may get a last glimpse of Venus after sunset. More -- after this. March 28 Goodbye Venus The planet Venus rounded the other side of the sun from our point of view last summer -- and came out of the sun's glare in late August or early September. Then it was a brilliant, remote point of light, visible low in the west after sunset. In early fall, Venus began a slow crawl up the dome of the evening sky -- appearing a little higher in the west with each new twilight. By December and January, the brightest planet was high in the west after sunset -- all the while steadily gaining on Earth in the race around the sun. It reached its highest point in the west on January 21. Then Venus began plunging downward in our sky again -- still all the while catching up to Earth. It didn't take as long to fall back into the sun's glare as it did to climb out of it. But things are happening faster for Venus now -- because the planet is very near Earth in space -- on the same side of the sun -- soon to pass directly in between us and the sun, on April 3. Tonight you may get a last look at Venus, in a very clear western sky a short time after sunset. It will appear strangely bright for an object so near the horizon. Although Venus may still be visible under ideal conditions now, it'll shortly disappear entirely from our evening sky -- to pass between us and the sun -- and quickly reappear in the east before dawn before the middle of April. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin
joels@tektools.UUCP (Joel Swank) (04/01/85)
What is the highest Venus ever gets?
jans@mako.UUCP (Jan Steinman) (04/02/85)
In article <181@tektools.UUCP> joels@tektools.UUCP (Joel Swank) writes: >What is the highest Venus ever gets? Depends on what he's smoking! :-) (Oh, I am really, really sorry for that one, folks!) -- :::::: Jan Steinman Box 1000, MS 61-161 (w)503/685-2843 :::::: :::::: tektronix!tekecs!jans Wilsonville, OR 97070 (h)503/657-7703 ::::::
msb@lsuc.UUCP (Mark Brader) (04/06/85)
joels@tektools.UUCP (Joel Swank) writes: > What is the highest Venus ever gets? Can't resist answering this one, because it's so easy. Venus can be seen at the zenith, meaning straight up, by daytime observers in the tropics. (Well, I can't say I've verified this personally, but I have seen Venus in the daytime, and there has to be SOME place where it's directly overhead, since the Earth is spherical.) If you restrict the question to nighttime observation and define nighttime as beginning when the sun would set if atmosphere effects are neglected, you are asking what the maximum Venus-Earth-Sun angle is. Simplifying the orbits to coplanar circles, this occurs when the Earth-Venus-Sun angle is 90 degrees. (Oddly enough, this situation was also described in net.puzzle a couple of months ago -- with respect to clock hands instead of planets!) The desired angle is then the arc sine of the ratio of the orbital radii. Taking the radii in gm, that's arcsin(108.1/149.5) = 46.3 degrees. However, the earth's orbit is not really circular, and if the perihelion radius is, as I think, 147.2 gm, the angle becomes 47.3. Fortunately Venus's orbit is very close to circular. However, Venus can only be observed at such an angle from the tropics. I'd have to brush up my spherical geometry before answering the question for other latitudes. But you didn't ask about other latitudes. Mark Brader
gwhawkins@watrose.UUCP (gwhawkins) (04/07/85)
> > What is the highest Venus ever gets? > Simplifying the > orbits to coplanar circles, this occurs when the Earth-Venus-Sun angle is > 90 degrees. (Oddly enough, this situation was also described in net.puzzle > a couple of months ago -- with respect to clock hands instead of planets!) > Mark Brader Before you go and brush up on your spherical geometry (I boo-booed and deleted his comment on that) you should brush up on your planar geometry. Your statement about highest angle above the horizon at 90 degrees is a gross oversimplification. All you have to do to show this is draw the orbit of Venus on paper (admittedly a big sheet of paper); pick a position for the earth; and draw the hypotenuse of your 90 degree triangle. You'll find that the hyp. passes inside the orbit of Venus. Using circular co-planar orbits and no atmosphere, etc., the maximum angle above the horizon is found by drawing a line from the earth TANGENTIAL to the orbit of Venus (again, a very long line). larry fast (Universty of Waterloo) broadcasting from exile
muffy@lll-crg.ARPA (Muffy Barkocy) (04/07/85)
In article <678@mako.UUCP> jans@mako.UUCP (Jan Steinman) writes: >In article <181@tektools.UUCP> joels@tektools.UUCP (Joel Swank) writes: >>What is the highest Venus ever gets? > >Depends on what he's smoking! :-) > >(Oh, I am really, really sorry for that one, folks!) >-- >:::::: Jan Steinman Box 1000, MS 61-161 (w)503/685-2843 :::::: >:::::: tektronix!tekecs!jans Wilsonville, OR 97070 (h)503/657-7703 :::::: *HE*? Tsk, tsk...surely you remember from mythology: Venus is female. In fact, as I recall, Venus and Earth are the only female planets in this solar system. Muffy
jans@mako.UUCP (Jan Steinman) (04/10/85)
In article <507@lll-crg.ARPA> muffy@lll-crg.UUCP (Muffy Barkocy) writes: >In article <678@mako.UUCP> jans@mako.UUCP (Jan Steinman) writes: >>In article <181@tektools.UUCP> joels@tektools.UUCP (Joel Swank) writes: >>>What is the highest Venus ever gets? >> >>Depends on what he's smoking! :-) > >*HE*? Tsk, tsk...surely you remember from mythology: Venus is female. Actually, I was thinking about Venus Flytrap (of "WKRP Cincinnati" fame) at the time, who is a much more likley smoker then the Goddess of Love. But then again, love can be smokin'! -- :::::: Jan Steinman Box 1000, MS 61-161 (w)503/685-2843 :::::: :::::: tektronix!tekecs!jans Wilsonville, OR 97070 (h)503/657-7703 ::::::
johnston@spp1.UUCP (Micheal L. Johnston) (04/11/85)
> > > What is the highest Venus ever gets? > > Simplifying the > > orbits to coplanar circles, this occurs when the Earth-Venus-Sun angle is > > 90 degrees. (Oddly enough, this situation was also described in net.puzzle > > a couple of months ago -- with respect to clock hands instead of planets!) > > Mark Brader > > Before you go and brush up on your spherical geometry (I boo-booed and deleted > his comment on that) you should brush up on your planar geometry. Your > statement about highest angle above the horizon at 90 degrees is a gross > oversimplification. All you have to do to show this is draw the orbit of > Venus on paper (admittedly a big sheet of paper); pick a position for the > earth; and draw the hypotenuse of your 90 degree triangle. > > You'll find that the hyp. passes inside the orbit of Venus. Using > circular co-planar orbits and no atmosphere, etc., the maximum angle > above the horizon is found by drawing a line from the earth TANGENTIAL > to the orbit of Venus (again, a very long line). > > larry fast (Universty of Waterloo) > broadcasting from exile Maybe I missed something but I thought Mark's posting was correct. The hypotenuse to his 90 degree triangle SHOULD pass inside the orbit of Venus since it's going straight to the sun. Your steps to find the maximum angle only draw a line, so I'll assume the second line is the line tanget to the earth's surface at the observation point to the sun at sunset time. (I think mark stated that 'how high' meant the angle at the time the sun goes down). This second line is the hypotenuse were talking about however, so if you're truly talking about a different angle, I missed. Remember, Mark's hypotenuse IS the earth's orbital radius. Venus' orbital radius is then the closing line and the arcsin of this ratio (Venus' figure on top) would be the angle in question. Mike Johnston