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I Conversion help needed

  1. Jun 13, 2016 #1
    Can someone help me convert 1.2 parsecs into arcminutes?

    I'm currently doing an internship that does astrophysics research and the grad student told me to do this conversion. I need it to get the data that I need to make tables, but I'm just confused.

    I asked for help but they said that this information was all that I needed to make the conversion.

    Any help is greatly appreciated.
  2. jcsd
  3. Jun 13, 2016 #2


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    I'm not sure you can directly convert those quantities. A parsec is a unit of distance but an arcminute is an angle. Is there any other information you can give us? What information is going to be in these tables?
  4. Jun 13, 2016 #3
    The tables show the location of individual stars that are in a cluster around a more massive central star. And she wants the data for all tge stars that are 1.2 parsecs away from the center one but the website requires that I put it in arcminutes (90 max). I told her that I thought that I was missing some information but she said that I had everything that I needed.

    I showed her an equation that I came across which is theta=size (in AU) / distance (in parsecs)
    Then I can convert radians to arcminutes.

    She said yes that I just convert 1.2 parsecs into AU and then said that it was an easy conversion...

    I'm lost. I'm sorry that I don't have more.
  5. Jun 13, 2016 #4


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    You need to know the distance to the cluster. Then the angular distance of a star from the center of the cluster is just:

    angular distance of a star from the center of the cluster = distance of the star from the center of the cluster (in parsecs) / distance to the cluster (in parsecs)
  6. Jun 14, 2016 #5
    1 parsec =1/arsec (arcsec=1/60 arcmin)
    multiply by 1.2 to get 1.2/arcsec, then convert to arcmin.
    This gives you apparent angular size at 1.2 parsecs.
    AU and Parsec relationship : 1 AU = 149,597, 000 kilometers = 1.49597E10 meters
    1 pc= 3.0857E16 meters =2.0662E5 AU
    1AU = just under 5E-6 pc
  7. Jun 14, 2016 #6


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    have you a reference for this, it doesn't sound correct ?
    I cannot see how you can have a distance equalling an angular measurement without having more info
    namely the distance between you and the objects

    the angular measurement of separation of 2 objects a parsec apart is going to be very different for me, the observer if I am at 10 lightyears distance compared to if I am 100 lightyears distance from them

  8. Jun 14, 2016 #7


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    Yes. As davenn says, and as I said in Post #4, you need to know the distance to the cluster in order to do the calculation.

    @mmont012 - have you resolved the issue?
  9. Jun 16, 2016 #8
    She gave me a new piece of information; the distance of the cluster is 1.7 kpc. Thank you all for your help! It is truly appreciated!
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