Stellar parallax

Stellar Parallax

Stellar parallax is the apparent shift of the position of any nearby star (or other object) against the background of distant objects. It is caused by the orbital motion of the Earth. This effect is so small that it was unobservable until the 19th century when Friedrich Bessel made the first successful measurement of stellar parallax.

History

The concept of parallax was first postulated by Aristotle who provided one of the earliest discussions on the apparent irregular motion of the planets. However, the first successful measurements of stellar parallax were made by Friedrich Bessel in 1838 for the star 61 Cygni using a Fraunhofer heliometer at Königsberg Observatory.

Measurement

Stellar parallax is typically measured in arcseconds (or milliarcseconds) and is considered the most fundamental measurement in determining the distance to a star. The distance is calculated using the formula:

d = 1/p

where d is the distance in parsecs and p is the parallax in arcseconds. This relationship is known as the parallax formula.

Applications

Stellar parallax is used in various fields of astronomy. It is used to measure the distances to the closest stars, the luminosity of stars, and the scale of the universe. It is also used in the field of exoplanet detection through the transit method.

Limitations

The main limitation of stellar parallax is that it can only measure distances to stars up to a few hundred light-years away. This is because the parallax angle becomes too small to measure with current technology for stars that are further away.

See also

• Astrometry
• Hipparcos
• Gaia (spacecraft)