Uncertainty of distance measurements for regions between 50250 pc awayby Aiveenoka Tags: distance, measurements, regions, uncertainty 

#1
Dec612, 01:07 PM

P: 7

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
Dec712, 10:09 AM

Mentor
P: 10,786

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 



#3
Dec812, 09:33 AM

P: 7

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 :) 



#4
Dec812, 10:42 AM

Mentor
P: 10,786

Uncertainty of distance measurements for regions between 50250 pc away
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. 



#5
Dec1112, 11:54 AM

P: 7

Thank you very much mfb :)
It's amazing what is possible! 


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