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

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Discussion Overview

The discussion revolves around the uncertainty in distance measurements for young stellar objects (YSOs) located between 50 to 250 parsecs away. Participants explore the challenges of finding reliable error values associated with these measurements and the implications for a project on mass loss rates of protostars.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in finding error values for distance measurements in literature, noting that distances are often reported without associated uncertainties.
  • Another participant mentions that the uncertainty in distance measurements can depend on the object and the telescope used, citing the Hipparcos mission's precision and the expected improvements from the GAIA mission.
  • A participant shares their supervisor's estimate of an error of 5 to 10 parsecs but seeks to justify their choice of error values, noting that the error would vary significantly between different distances.
  • There is a discussion about the precision of distance measurements, with one participant affirming that while high precision is possible, it does not apply universally to all stars.
  • A participant references the Hipparcos catalogue as a resource for parallax measurements and their standard deviations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the standard error values for distance measurements, and multiple views on the precision of measurements and the variability of errors remain present.

Contextual Notes

Participants express uncertainty regarding the specific methods used for measuring distances to YSOs and the implications of varying error estimates based on distance.

Who May Find This Useful

This discussion may be of interest to researchers and students working on astrophysics, particularly those focused on stellar distances, measurement techniques, and the implications for astrophysical modeling.

Aiveenoka
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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
 
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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
 
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 :)
 
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.
 
Thank you very much mfb :)

It's amazing what is possible!
 

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