What distance is one Parsec

(Diagram needed)

As the Earth orbits the sun, the apparent position of a (relatively) nearby star varies with relation to a background of much more distant stars. The parallax angle is the angle between observed positions at each 'end' of the orbit (as observed in July as opposed to January).

The distance from the Sun (not the Earth although with vast distances this difference is fairly trivial) to the star being observed can be calculared by trigonometry, given that the distance from the Earth to the Sun is defined as 1 AU (Astronomical Unit) : d = 1/ tan(p) but the angle p is so small that the small angle approximation tan(p) = p gives

d = 1/p

The angle in question is incredibly small so one degree is subdivided into 60 arcminutes, each of which is divided into 60 arcseconds (so 1 arcsec = 1/3600 ths of a degree). A parsec is the distance of a star from the sun if the observed angle of parallax was 1 arcsec. This allows distance (in parsecs) to be given as 1/p (in arcseconds)

Answered by Katie G. Physics tutor

4794 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

Why does an α particle cause more ionisation than a β particle if they have the same kinetic energy?


Why does current split between branches of a parallel circuit, but voltage remains the same for each branch?


A sigma0 particle with mass 1193 MeV/c^2 decays into a lambda0 particle with mass 1116 MeV/c^2 a photon. Find the energy and momentum of the photon, assuming that the kinetic energy of the lambda0 particle is negligible.


What is the force on a moving charged particle in a magnetic field, and why is no work done by this force when it accelerates the particle?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences