Hi Trisha, Some of us have to sleep in the daytime after staying up all night observing, so I didn't get your message until now.... Here's the scoop on Mars and its "oppositions". Opposition for any object orbiting the sun as viewed from Earth happens when the Earth, the sun, and the object (asteroid, planet, comet, etc) are lined up with the object farther from the sun than Earth (the inner planets do not reach opposition). When this happens, several things of interest happen. First, the object is as close as it can be in that time period (more on that in a bit - it might get closer at other times...). Closer means brighter, and closest usually means brightest. Another affect happens that makes an object near opposition even brighter and that is the so-called "opposition affect." An object exactly opposite the sun scatters light straight back towards the sun more efficiently than in other directions. You can see this affect from airplanes or when the sun is low - you will see a bright halo around your shadow - around the planes shadow if you are sitting at a window where you can see the shadow or around your head if the sun is low and you're not on a plane. I've seen this best on a golf course early in the morning when there is dew on the grass. So asteroids, planets, the Moon, etc., will be that much brighter. Also, the object will be full (like the full moon) rather than gibbous or quarter or crescent - that makes a big difference for objects close to Earth, but almost no difference for the distant planets, since they are almost always very close to full regardless of where they are in their orbits. Ok, I've probably lost a few of you. I'll try to loose a few more of you in the next paragraph.... ;-) I'm trying really hard to think of a way to bring geocaching into this, but I haven't thought of a good way yet.... Back to Mars (well, I'd like to go there someday anyway...). The orbits of the planets are all nearly circular, but they are very slightly elliptical which means that they change their distance to the sun as they orbit the sun. Earth's orbit is slightly elongated as well and at the moment we are actually pretty close to our most distant from the sun (the seasons are dominated by the tilt of the rotation axis with distance from the sun falling a very distant 2nd). Mars orbits the Sun every 1.88 years and comes back into alignment with Earth every 2.14 years, approximately (this is called the synodic period and does not equal Mars' orbital period because the Earth orbits as well). The closest Mars and Earth could get to each other would happen if Mars came to opposition when the Earth was farthest from the Sun while Mars was closest to the Sun. This doesn't quite happen, but it is not far off. The closest the two orbits get to each other happen in the direction that Earth is at the end of August when the two orbits are about 34.4 million miles apart. So, when Mars comes to opposition at the end of August, it will be as close as it can come and Mars will appear at its largest. When it comes to opposition at the end of February, its opposition distance will be as large as it can be (around 65 million miles) and Mars will appear smallest at opposition (it can appear even smaller when observed away from opposition). The opposition you discovered happened on about August 27, 2003 and it was VERY spectacular. I got to look at Mars through the 90 inch telescope on Kitt Peak at about that time and Mars was very very big and bright. I don't expect to see Mars with my own eyes any better unless I'm about to drop into orbit around Mars itself. This year, Mars will be at opposition on about October 29 when it will be about 43 million miles from Earth and will appear about 20 arcseconds across (the Moon is about 1800 arcseconds across for comparison) - not too bad as Mars oppositions go, but not quite what it was in 2003. You can already see it in the morning sky - it's a bright red object all by itself about halfway up in the East before twilight starts. Jim. On Wed, 6 Jul 2005, Trisha Brasher wrote: > Well, Steve, turns out that it already happened in 2003. I remember > that....it doesn't seem that long ago. > > But, if it WAS real, at least you would have known!! :-) > > > ----- Original Message ----- > From: azcachemeister@getnet.com > To: listserv@azgeocaching.com > Subject: Re:[Az-Geocaching] Never MInd! > Date: Wed, 6 Jul 2005 10:11:21 -0700 (PDT) > >> >> On the contrary, thanks for the 'off topic' post. I may not have >> known about this otherwise! >> >> -----Original Message----- >> From: Trisha Brasher >> Sent: July 6, 2005 9:26:28 AM GMT >> To: Arizona Geocaching >> Subject: [Az-Geocaching] Never MInd! >> >> OH, I just read it more carefully and it says that Mars will look >> as big as the full moon WITH magnification. >> >> OK, my faith in the universe is restored. >> >> I was beginning to think about the "signs and wonders" in a Biblical sense! >> >> Sorry for the off-topic if that offends you, but many on the list >> have enjoyed the astronomy lessons in the past. >> >> Jim, any comments about the Mars stuff? >> >> Thanks >> Trisha ~ Lightning >> >> >> >> >> "My life is just a pencil in the hand of God, >> and it is He who is writing my story." ~ Mother Teresa >> >> ____________________________________________________________ >> Az-Geocaching mailing list listserv@azgeocaching.com >> To edit your setting, subscribe or unsubscribe visit: >> http://listserv.azgeocaching.com/mailman/listinfo/az-geocaching >> >> Arizona's Geocaching Resource >> http://www.azgeocaching.com >> >> . >> >> ____________________________________________________________ >> Az-Geocaching mailing list listserv@azgeocaching.com >> To edit your setting, subscribe or unsubscribe visit: >> http://listserv.azgeocaching.com/mailman/listinfo/az-geocaching >> >> Arizona's Geocaching Resource >> http://www.azgeocaching.com > > > > "My life is just a pencil in the hand of God, > and it is He who is writing my story." ~ Mother Teresa > > ____________________________________________________________ > Az-Geocaching mailing list listserv@azgeocaching.com > To edit your setting, subscribe or unsubscribe visit: > http://listserv.azgeocaching.com/mailman/listinfo/az-geocaching > > Arizona's Geocaching Resource > http://www.azgeocaching.com > Jim Scotti Lunar & Planetary Laboratory University of Arizona Tucson, AZ 85721 USA http://www.lpl.arizona.edu/~jscotti/