# Velocity determination through redshift

• ShayanJ
In summary, astronomers use the shift in a star's spectrum to calculate its velocity by measuring the displacement of the spectral lines, which indicates the amount of redshift. This method relies on the unique "fingerprint" of each element in the spectrum and is a crucial tool in understanding the properties of distant stars.
ShayanJ
Gold Member
As you know,astronomers calculate the velocity of distant stars by measuring their light's redshift.This suggests that they have a way to know each star's light's wavelength in a different way from observing its light.What is that way?
thanks

They measure the shift in the star's spectrum. Each element produces a unique "fingerprint" as a pattern of lines in the spectrum. By looking at the position of these lines in the star's spectrum they can tell if they have been shifted from their normal position, this tells them the amount of red shift.

For Instance, if they find the pattern of lines associated with hydrogen closer to the red end of the spectrum than it should be, this tells then that the light has been red shifted. How far it has moved tells them by how much it has been red shifted.

## 1. How is velocity determined through redshift?

Velocity is determined through redshift by measuring the shift in wavelength of light emitted by an object. This shift is caused by the object moving either towards or away from the observer, known as the Doppler effect. The larger the redshift, the faster the object is moving.

## 2. What is the relationship between redshift and velocity?

The relationship between redshift and velocity is known as the Hubble's Law, which states that the farther away an object is from the observer, the faster it is moving. This relationship is used to determine the velocity of objects in the universe.

## 3. How is redshift measured?

Redshift is measured by comparing the observed wavelength of an object's light to its known rest wavelength. The difference between the two wavelengths is then used to calculate the redshift value, which can then be used to determine the object's velocity.

## 4. Can redshift be used to determine the velocity of all objects in the universe?

No, redshift can only be used to determine the velocity of objects that are moving away from or towards the observer. Other factors, such as gravitational forces, can also affect an object's velocity and must be taken into consideration.

## 5. Are there any limitations to using redshift for velocity determination?

Yes, there are some limitations to using redshift for velocity determination. Redshift can only provide an accurate measurement of velocity for objects that are relatively close to the observer. For objects that are very far away, the effects of the universe's expansion and other factors can distort the redshift value, making it less reliable for determining velocity.

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