4 July 2006
Conjunction of two bodies: when they appear to pass near each other in the sky. Usually geocentric conjunction is meant, I.e. As seen from the Earth; There are also the heliocentric conjunctions of the planets, when they overtake each other as seen from the Sun. And usually conjunction in right ascension is meant, when they have the same right ascension, I.e. One is celestially north of the other. There is also conjunction in longitude, when one is north of the other with respect to the ecliptic. The moment when they are closest (appulse) may be neither of these, since they are probably not moving exactly parallel to the ecliptic, or equator. From Ast. Cal. 1995 onward we give the time of applus instead -- e.g. "Mercury passes 1.5° N.W. Of Venus" -- because they are observationally more interesting. An applus may be so close that one body occults the other. See also quasi-conjunction. Note especially:
-- Conjunctions with the Moon: usually the statement (such as "Moon 1° north of Spica) refers to the center of the Moon as seen from the center of the Earth. From a place on Earth's surface it may appear very different; e.g. from a place in the north hemisphere the Moon may even pass south of the star.
-- Conjunctions with the sun are of two kinds: (1) inferior conjunction, when the body passes between Earth and Sun, and superior conjunction, when it passes on the far side of the Sun. Since only Mercury and Venus (and Earth-crossing asteroids and comets) can experience both kinds, the terms are usually only used for them; for all others, just "conjunction" is used and superior conjunction is implied.inferior conjunction of an inferior planet with the Sun; when it passes across the Sun-Earth line. It then becomes a morning star. Occasionally the planet actually transits in front of the Sun's disc. % superior conjunction: of an inferior planet (Mercury or Venus); when it passes on the far side of the sun, and becomes an evening star. See more fully under inferior conjunction.
transit: the crossing of a body (1) over the meridian, or (2) in front of another body. Mercury and Venus at their inferior conjunctions sometimes transit across the face of the Sun (Mercury about 4 times in 33 years, Venus 4 times in 243 years). Jupiter's satellites and their shadows transit across the face of the planet.
[quasi-conjunction and morning star are not defined in this version of the glossary]
The Firefly Astronomy Dictionary days:
conjunction The alignment of the Earth with tow other bodies in the Solar System so that from the Earth the other two appear in (nearly) the same position. The term is used mainly for alignments of the major planets (SEE the diagram on page 46.). A superior planet is at conjunction when on the opposite side of the Sun from the Earth. An inferior planet is at inferior conjunction when it lies between the Earth and the Sun, and at superior conjunction when it is on the far side of the Sun. Because planetary orbits are inclined at various angles to the plane of the ecliptic, alignments at conjunction are rarely exact, and conjunction is defined as to occur when the two bodies have the same celestial longitude. As seen from earth.
Two or more planets -- including in this case the Moon -- are also said to be in conjunction when they are close together in the sky.inferior planet Either of the planets Mercury and Venus, which orbit inside the Earth's orbit.
superior planet Any of the planets Mars, Jupiter, Saturn, Uranus, Neptune and Pluto, which orbit outside the Earth's orbit.
The simplest definition I have found in my quick search comes from The Grand Tour: A Traveler’s Guide to the Solar System.
- Conjunction
- When two or more planets appear close together in the sky.
They finally got the Space Shuttle launched this afternoon. There is one visible ISS pass this evening, assumedly with the Shuttle racing behind it, but it will be too cloudy to see them today or tomorrow. There are additional visible passes on 6Jul06 and 7'Jul06 then they are lost to us for the duration of the Shuttle mission.
| Observing Location | MetOval | ||||
|---|---|---|---|---|---|
| Observational Period | 2045-2145 EDT | ||||
| Atmospheric Conditions | When I left dinner I headed up to the oval to sit out on the benches and do a little reading. But I noticed that there was some blue in the sky so headed home to get my PDS so I would know when and where to look for ISS and hopefully the Space Shuttle behind it.
The air has cooled off considerably since sunset and does not feel anywhere near as humid as it was. There are patchy stratus clouds with some haze. There had been a ring around the moon but right now it is barely shining through the clouds.
| ||||
| Instruments | Naked-eye Observing | ||||
| Observing Party | Charlie Ridgway |
| Target | ISS visible pass |
|---|---|
| Constellation | |
| Category | Satellite |
| Time | 20060704.2137 EDT |
| Comments | The track posted in the Heavens Above table in AvantGo didn't seem right, NW to SW to SE. But when I estimated it in Planetarium it is because it is closer to the zenith when it is listed as SW. The track looks like it parallels the ecliptic pretty closely.
Unfortunately the clouds have filled in enough that I can no longer see the sky |
Since I couldn't see the sky I did some more reading in The Grand Tour. A while back I was asked by a passer-by if Jupiter didn’t shine by its own light. He had read something about that. I said I had never heard of it and that all planets shine by reflected light. Reading about Jupiter I found out what is going on. They say that Jupiter is mostly hydrogen which gets denser as you get closer to the center of the planet eventually changing to a liquid and possibly a solid. It also gets hotter as it gets denser and that the planet radiates heat. So it does radiate energy but it is in the IR, not the visible portion of the spectrum. In the chapter on Saturn they say that it produces more heat itself than it receives from the Sun.
posted by Charlie at 13:31
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