it takes many years to see the change of arms of a galaxy. so how was the rotation of arms measured?
jayaramas said:but it is said that stars in the arms are moving at fast rate.
the arms are nothing but collection of stars. so, how can arms have a different speed and if so, how can it be measured?
They are indeed going faster than general relativity predicts, hence the assumption that there is hidden (dark) matter.jayaramas said:but it is said that stars in the arms are moving at fast rate.
Scientists use a technique called spectroscopy to measure the rotation of galaxies. This involves analyzing the light emitted by stars in the galaxy, which can reveal the speed at which the stars are moving and thus the rotation of the galaxy.
Measuring the rotation of galaxies allows scientists to understand the distribution of mass within the galaxy. This can help us understand the formation and evolution of galaxies, as well as the nature of dark matter, which is thought to make up a significant portion of a galaxy's mass.
The time it takes for a galaxy to complete one rotation can vary greatly depending on the size and mass of the galaxy. For example, the Milky Way takes approximately 250 million years to complete one rotation, while smaller galaxies may rotate much faster.
Yes, galaxies can rotate in different directions. The direction of rotation is determined by the initial angular momentum of the gas and stars that formed the galaxy, which can be affected by factors such as collisions or interactions with other galaxies.
The rotation of galaxies is not directly related to the expansion of the universe. However, the expansion of the universe can affect the observed rotation of galaxies by stretching the light emitted by the stars, causing their spectra to shift towards longer wavelengths. This is known as cosmological redshift and can make it more difficult to accurately measure the rotation of distant galaxies.