Definition:Astronomical Distance Units/Parsec

Definition

The parsec is a derived unit of length.

It is derived as the distance at which $1$ astronomical unit subtends an angle of $1$ second of angle.

It is therefore exactly $\dfrac {648 \, 000} \pi$ astronomical units.

The parsec is the standard unit of measurement used by astronomers when discussing distances.

Conversion Factors

\(\ds \)

\(\)

\(\ds 1\)

parsec

\(\ds \)

\(\approx\)

\(\ds 30 \cdotp 85677 \, 58149 \, 13673 \times 10^{15}\)

metres

\(\ds \)

\(\approx\)

\(\ds 1 \cdotp 9174 \times 10^{13}\)

miles

\(\ds \)

\(=\)

\(\ds \dfrac {648 \, 000} \pi\)

\(\ds \approx 2 \cdotp 06265 \times 10^5\)

astronomical units

\(\ds \)

\(\approx\)

\(\ds 3 \cdotp 26\)

light years

Symbol

$\mathrm {pc}$

The symbol for the parsec is $\mathrm {pc}$.

The $\LaTeX$ code for \(\mathrm {pc}\) is \mathrm {pc} .

Linguistic Note

The word parsec is a contraction of the terms parallax second.

Sources

• 1964: Milton Abramowitz and Irene A. Stegun: Handbook of Mathematical Functions ... (previous) ... (next): $2$. Physical Constants and Conversion Factors: Table $2.4$ Miscellaneous Conversion Factors
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): parsec
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): parsec