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    Re: A wonderful dawn with all four planets
    From: Frank Reed
    Date: 2016 Jan 22, 12:02 -0800

    Well, for pet peeves, I'll go with the fact that the NY Times story quoted the Farmer's Almanac. Blech! Whoever wrote the article for the NYT clearly does not know much about astronomy and also managed to screw up the significance of the ecliptic in this. But not to worry, Norm, it's usually discussed by astronomy educators whenever possible, and there's a nice new article today by Kelly Beatty at Sky & Telecope that emphasizes the ecliptic and the plane of planets.

    While you're at it, you can explain the zodiac signs (this is where many astronomy educators panic). The signs are simply thirty degree wide bands of ecliptic longitude. You start at the location where the ecliptic crosses the celestial equator. The first thirty degree band from that point is the sign of Aries. The next thirty degree band is called Taurus, followed by Gemini, and so on. The key concept for positional astronomy here is that the zodiac signs are really a type of coordinate system extending the sexagesimal system. Thus if the ecliptic longitude of a planet is 41° 24', I can equally well write that as 11° Taurus 24'. For quick communication, this is possibly, arguably easier and more efficient. It's a bit like when phone numbers used to be given with "central office names" like "Pennsylvania 6 5000". Until the early nineteenth century astronomers still used this system, but it was rapidly falling out of fashion. Today it stinks of vile astrology -- at least from the point of view of most astronomers! Fashion is fashion. But with the taint of astrology on it, I no more expect this fashion to come back in the field of astronomy than I expect to hear a phone number called out as "Klondike 5 3226" anytime soon (folks in the mid-Atlantic states may need to Google that number this weekend).

    Finally where is "Planet Nine"? The new large planet which very likely exists having been detected by its gravitational perturbations of objects in the Kuiper Belt and beyond must have certain orbital elements in order to produce the pattern of distorted orbits that we see out there. According to FindPlanetNine.com, ruling out the areas that have already been covered reasonably well by searches, Planet Nine has about a 50% chance of being inside a 30° wide circle centered roughly on Orion's belt. Its estimated visual magnitude is around mag. 20-22 so you may need binoculars to spot it. Really big binoculars. If you're out looking for the five "naked eye" planets before dawn next week, the edge of that 30° wide circle is just setting (Orion's belt near 30° below the horizon as Mercury is rising), but maybe you can point that out to any other brave souls you manage to convince to watch the planets so early in the morning.

    Frank Reed
    The planets in 1825: Mercury, Venus, Earth, Mars, Ceres, Juno, Pallas, Vesta, Jupiter, Saturn, and the Georgian.

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