Question

1 parsec is approximately equal to ( when AU is an astronomical unit)

1. 2* 10⁵ AU
2. 2* 10⁶AU
3. 2* 10⁸ AU
4. 2* 10¹⁰ AU

Answer 1

• One parsec is the distance at which one AU subtends an angle of one arc second.
• It is equal to 3.26 light years

$$\begin{gathered} \mathrm{One}\mathrm{parsec}=3.26\mathrm{light}\mathrm{years} \\ =3.26\mathrm{light}\mathrm{years}\times \frac{63239.7\mathrm{AU}}{1\mathrm{light}\mathrm{year}} \\ =206161.4\mathrm{AU} \\ \mathbf{=}\mathbf{2}\mathbf{\times }{\mathbf{10}}^{\mathbf{5}}\mathbf{}\mathbf{AU}\mathbf{}\mathbf{\left(}\mathbf{approx}\mathbf{\right)} \end{gathered}$$