ASTR 1P01 Lecture Notes - Lecture 9: Atomic Nucleus, Photon, Chemical Element

• School: Brock University
• Department: Astronomy
• Course: ASTR 1P01
• Professor: Bozidar Mitrovic

Document Summary

Measuring the distances for not too distant stars can be found from stellar parallax: trigonometry. 1au/d = sinp=p (measured in radians) =2pi/360 (measured in degrees) Change the unit for distance so that d=1/p or p=1/d. D in parsecs (pc), p in seconds of arc or arcseconds. 1 pc = 3. 26 (=3. 3) ly = 206,265 au. Note that the larger the distance (d), the smaller the parallax angle (p) and vice versa: even for the closest star (proxima centauri) the parallax angle is less than 1 arcsecond. P=0. 769 arcsecond: the stellar parallax was first measured in 1838 by f. bessel, due to the atmospheric blurring, the found based measurements of parallax have an uncertainty of. For p=0. 02 arcseconds the error is 10% Hence we cannot use parallax measurements from the ground based observatories for stars whose distances are greater than 160 ly. The distances for 10,000 stars were determined using parallax from ground based observatories.