punasiirtymäarvo

Punasiirtymäarvo, often represented by the symbol z, is a fundamental concept in astronomy and cosmology that quantifies the redshift of light from celestial objects. Redshift itself refers to the phenomenon where electromagnetic radiation from an object undergoes an increase in wavelength. This stretching of light waves is observed when the source of the radiation is moving away from the observer, a consequence of the Doppler effect.

The punasiirtymäarvo is a dimensionless quantity derived from the observed wavelength of light and its emitted wavelength. Specifically, it is defined as z = (λ_observed - λ_emitted) / λ_emitted. A positive punasiirtymäarvo indicates redshift, meaning the object is moving away from us. Conversely, a negative punasiirtymäarvo would imply a blueshift, where the object is moving towards us.

This value is crucial for understanding the expansion of the universe. Observations of distant galaxies show significant redshifts, implying they are receding from our own galaxy. The greater the punasiirtymäarvo, the farther away the galaxy is and the faster it is moving away. This relationship, known as Hubble's Law, is a cornerstone of modern cosmology, providing evidence for the Big Bang theory and allowing astronomers to estimate distances to very remote objects. Beyond cosmic expansion, punasiirtymäarvo is also used to study the motion of stars within galaxies and the dynamics of binary star systems.