'Redshift' is the phenomenon of of the light changing it's color or light shifting it's position in visible spectrum of light.
So what does this mean and why it happens?
The picture below represents the 'electromagnetic spectrum' of light. The electromagnetic spectrum covers a wide range of wavelengths and photon energies. As we can see when we go from left to right in the spectrum the energy and the frequency increases while the wavelength decreases. So every radiation, seen or unseen must fit to a particular value on this scale.
But we are interested in the 'visible spectrum' as we are talking about the visible light. Lets look at the pictures below. The visible spectrum consists of 3 primary colors that is red, green and blue. That is why we always use the term 'RGB' while dealing with colors in computers which stands for red:green:blue composition.
As we can see the visible spectrum lies within the wavelength range of 400nm-700nm so when we choose different wavelengths between this value then the color of the light changes.
Christian Doppler proposed that there is a change in frequency of a wave (or other periodic event) for an observer moving relative to its source. Which is known as the 'Doppler effect'.
Let's say that a car is moving towards you. So you could hear the pitch of the sound is increasing as the car approaches you and the pitch getting reduced as the car recedes from you as we can see in the animation below. You can see the waves at the front of the car or he source 'pressed' against each other increasing the frequency, lowering the wavelength and at the back the opposite effect.
The same thing happens with a source of light. As a source of light moves towards or away from us then light wave changes it's frequency and wavelength so changing it's color slightly.
Well if you are thinking that we see many moving light sources everyday in our life so why can't we see a change in the color of light. That is because the source of light has to move with very high speeds like in kilometers per second for it's light to change it's color slightly.
What is 'redshift'?
If a source of light comes towards us at very high speed then the wavelength decreases, shifting the light towards the blue end of the spectrum, which is called 'blueshift'. So the light will appear a very little blue. And if a source of light recedes us at such tremendous speed then it's light will shift towards the red end of the spectrum, making it a little redder which is called 'redshift'.
As we know our universe is expanding at a very high rate which is given by the Hubble's constant. It's current value is 69.32 ± 0.80 (km/s)/Mpc measured by WMAP team,NASA. So light from any star or galaxy or supernova will be 'redshifted'.
By detecting the exact amount of shift in their radiation Scientists can know a lot of useful information like their compositions, distance from earth, speeds at which they are receeding etc.
So what does this mean and why it happens?
The picture below represents the 'electromagnetic spectrum' of light. The electromagnetic spectrum covers a wide range of wavelengths and photon energies. As we can see when we go from left to right in the spectrum the energy and the frequency increases while the wavelength decreases. So every radiation, seen or unseen must fit to a particular value on this scale.
 |
| Source - Wikipedia |
Christian Doppler proposed that there is a change in frequency of a wave (or other periodic event) for an observer moving relative to its source. Which is known as the 'Doppler effect'.
Let's say that a car is moving towards you. So you could hear the pitch of the sound is increasing as the car approaches you and the pitch getting reduced as the car recedes from you as we can see in the animation below. You can see the waves at the front of the car or he source 'pressed' against each other increasing the frequency, lowering the wavelength and at the back the opposite effect.
 |
| Source - Wikipedia |
The same thing happens with a source of light. As a source of light moves towards or away from us then light wave changes it's frequency and wavelength so changing it's color slightly.
Well if you are thinking that we see many moving light sources everyday in our life so why can't we see a change in the color of light. That is because the source of light has to move with very high speeds like in kilometers per second for it's light to change it's color slightly.
What is 'redshift'?
If a source of light comes towards us at very high speed then the wavelength decreases, shifting the light towards the blue end of the spectrum, which is called 'blueshift'. So the light will appear a very little blue. And if a source of light recedes us at such tremendous speed then it's light will shift towards the red end of the spectrum, making it a little redder which is called 'redshift'.
As we know our universe is expanding at a very high rate which is given by the Hubble's constant. It's current value is 69.32 ± 0.80 (km/s)/Mpc measured by WMAP team,NASA. So light from any star or galaxy or supernova will be 'redshifted'.
By detecting the exact amount of shift in their radiation Scientists can know a lot of useful information like their compositions, distance from earth, speeds at which they are receeding etc.
 |
| This image shows the Hubble Ultra Deep Field 2012, an improved version of the Hubble Ultra Deep Field image featuring additional observation time. The new data have revealed for the first time a population of distant galaxies at redshifts between 9 and 12, including the most distant object observed to date. These galaxies are shown at the top of the picture, and their locations are pinpointed in the main image. These galaxies will require confirmation using spectroscopy by the forthcoming NASA/ESA/CSA James Webb Space Telescope before they are considered to be fully confirmed. |
No comments:
Post a Comment