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Info about cygnus x1

  1. Nov 25, 2013 #1
    Hello forum users.

    I am a composer that knows sadly very little about astronomy. For a piece, I have been doing some research, and I want to find out either the date that cygnus x1 reaches its highest excursion relative to the celestial equator, or how I might be able to calculate such by myself. If it helps, its coordinates on the celestial sphere are: right ascension 19h38m and declination 34.6°
    Thanks in advance.
  2. jcsd
  3. Nov 25, 2013 #2


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    Your question is not clear. It's declination of 34.6° means that it is 34.6° above the celestial equator and will stay there for a long time. It is 6000 light-years away, so its movement on the celestial sphere is very small, on the order of milli-arc-seconds per year. So it will take thousands to millions of years to move significantly. Are you asking about its motion on those time scales, or asking about the precession of the celestial equator due to the precession of the Earth's axis (which takes 26,000 years to make a full circle), or something else?
  4. Nov 25, 2013 #3
    thanks so much for your quick response. Maybe I did a poor job of framing it, but what I really meant is- what might be the equivalent of a solstice be for cygnus x1. We see constellations drift with the seasons, so for cygnus x1, is there a predictable date at which it will appear most northerly? If so, what is that date, or how might I be able to deteremine it. Thanks so much.
  5. Nov 25, 2013 #4


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    OK, I see your question. That depends on its right ascension, which is about 20 hours. A right ascension of 12 hours will be highest in the sky (we say transiting) at midnight on the spring equinox, about Mar 21, and the stars progress at about 4 minutes/day, or about 2 hours of RA/month. So an RA of 20 hours will be highest in the sky at midnight on about July 21. It's in the constellation Cygnus, which is high in the sky during the summer for northern hemisphere observers. This time of year it will transit around around 4 PM and should be visible in the west soon after sunset. Is this your question?
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