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Uncertainty of distance measurements for regions between 50-250 pc away

  1. Dec 6, 2012 #1
    Hi,

    I am in the middle of a project dealing with the mass loss rate of protostars and hence I am working with the distance that these sources are away from us. I need to find the error in these distance measurements, however I cannot. In any paper (I find) that cites distances it just gives the number with no error values attached, and so I am wondering if there is a standard error in measuring the distance.

    I am working with distances including 56pc (smallest), 140pc and 250pc (largest).

    Thank you,
    A
     
  2. jcsd
  3. Dec 7, 2012 #2

    mfb

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    Staff: Mentor

    It depends on the object you measure and the telescope used for that.

    The Hipparcos mission measured many stellar positions with an uncertainty of ~1milliarcsecond, this corresponds to the parallax of an object 2000pc away. If the parallax measurement has the same quality as the absolute position measurement (as relative measurement, I would expect a better accurary), this gives a relative uncertainty of ~1/80, ~1/14, ~1/8 for 56, 140, 250 pc respectively. GAIA is designed to improve parallax measurements to 10 microarcseconds*, reducing the relative error to <0.13% for the full range of your distances.

    * similar to a coin (~2cm) on the moon
     
  4. Dec 8, 2012 #3
    Hi mfb,

    Thank you for your reply.
    The objects that have been measured are young stellar objects (YSOs) and unfortunately I don't know what was used to measure.
    I had asked my supervisor about the error and he said it would be 5 or 10 pc or similar, however he is away now and so I cannot check anything with him. But I want to be able to back up my reasoning for taking the error to be whatever I use and I also didn't feel that I could "pick and choose" the errors, not to mention that the error for 56pc would be very different than for 250pc, hence I asked here.
    When you say the error is about 1/80 for 56pc do you mean 56 +/- 0.0125pc ? If that is the case, that is amazing! Technology is fascinating!

    Aiveenoka :)
     
  5. Dec 8, 2012 #4

    mfb

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    It is possible to measure distances with that precision. It does not mean that every star has been measured with that precision.

    A quick search lead me to this website: The hipparcos catalogue has the parallax (H11) together with its standard deviation (H16) as parameters.
     
  6. Dec 11, 2012 #5
    Thank you very much mfb :)

    It's amazing what is possible!
     
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