The Earliest Stars And Galaxies In The Universe

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Science@ESA (Episode 4): Following The Redshift (Part 1) - The Earliest Stars and Galaxies In The Universe. From HST (Hubble Space Telescope) to JWST (James Webb Space Telescope).

In this fourth episode of the Science@ESA vodcast series Rebecca Barnes will identify some of the key discoveries achieved with the famous Hubble Space Telescope, look at the concept of redshift, and meet a new telescope that will be used to uncover the early Universe.

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'Redshift' is a key concept for astronomers. The term can be understood literally - the wavelength of the light is stretched, so the light is seen as 'shifted' towards the red part of the spectrum. Something similar happens to sound waves when a source of sound moves relative to an observer.

This effect is called the 'Doppler effect' after Christian Andreas Doppler, an Austrian mathematician who discovered that the frequency of sound waves changes if the source of sound and the observer are moving relative to each other.

If the two are approaching, then the frequency heard by the observer is higher; if they move away from each other, the frequency heard is lower. There are many everyday examples of the Doppler effect - the changing pitch of police and ambulance sirens, or train whistles and racing car engines as they pass by.

In every case, there is an audible change in pitch as the source approaches and then passes an observer. Everyone has heard the increased pitch of an approaching police siren and the sharp decrease in pitch as the siren passes by and recedes.

The effect arises because the sound waves arrive at the listener's ear closer together as the source approaches, and further apart as it recedes. Light behaves like a wave, so light from a luminous object undergoes a Doppler-like shift if the source is moving relative to us.

Ever since 1929, when Edwin Hubble discovered that the Universe is expanding, we have known that most other galaxies are moving away from us. Light from these galaxies is shifted to longer (and this means redder) wavelengths - in other words, it is 'red-shifted'. Since light travels at such a great speed relative to everyday phenomena (a million times faster than sound) we do not experience this red shift in our daily lives.

The red shift of a distant galaxy or quasar is easily measured by comparing its spectrum with a reference laboratory spectrum. Atomic emission and absorption lines occur at well-known wavelengths. By measuring the location of these lines in astronomical spectra, astronomers can determine the red shift of the receding sources.

However, to be accurate, the red shifts observed in distant objects are not exactly due to the Doppler phenomenon, but are rather a result of the expansion of the Universe. Doppler shifts arise from the relative motion of source and observer through space, whereas astronomical redshifts are 'expansion redshifts' due to the expansion of space itself.

Two objects can actually be stationary in space and still experience a red shift if the intervening space itself is expanding. A convenient analogy for the expansion of the Universe is a loaf of unbaked raisin bread. The raisins are at rest relative to one another in the dough before it is placed in the oven.

As the bread rises, it also expands, making the space between the raisins increase. If the raisins could see, they would observe that all the other raisins were moving away from them although they themselves were stationary within the loaf. Only the dough - their 'Universe' - is expanding.

• http://www.esa.int/esaSC/SEM8AAR1VED_index_0.html
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Category:

Science & Technology

Tags:

• earliest
• stars
• galaxies
• early
• universe
• redshift
• red
• shift
• esa
• science
• astronomy
• vodcast
• podcast
• hubble
• spitzer
• james
• webb
• space
• telescopes
• hst
• jwst
• astronomers
• wavelength
• light
• speed
• spectrum
• doppler
• effect
• frequency
• quasars
• emission
• absorption
• lines
• expansion

[dynchaw]

Who the hell would votebot this video?? It's an information video from a group working to advance our understanding of the universe; How is that controversial enough to be attacked??

[Novacayn]

@Tofy710 You are offering no arguments, you are just quoting scripture that has no bearing on the discussion at all.

Your religion is a lie, you culture is diseased, your women are oppresed, your men are uneducated, if Allah and Islam are the true way than why are Muslim countries such shitholes? Why are the happiest most educated and finacially stable countries in the world made up of mostly non-believers? Answer some of these questions with real words. Not some out dated, unverified crap.

[IntenseBeatz]

is that why the sky is blue?

[Alexbl100]

@bank4fun theres age for everything...

[Y3DXGL90]

@greydawn Well whats more red shifted then Rebecca Barnes.

[greydawn]

Thanks for the video. I was looking for a nice visual explanation of redshift.

[bank4fun]

poor poor silly white people. they actually think there is an age of the universe.

[danielbluesmoke]

They CANCELED the James Web telescope... They saw that we acquired too much knowledge, and they thought that it's better to spend even more money on war! When humanity will self-destruct, I will laugh so hard! AAAAHAHAHAHAHAHA!!!

[randmnumber]

@dynchaw it's controversial because they feel it attacks their religion. These are idiots at the same level of creationists

[mrrn100]

There are only two infinite things: human stupidity and the Universe, and I'm not sure about the Universe.

-Albert Einstein

[supergiuovane]

@lllRavenlll Unfortunately delayed to 2015, but most probably 2016.. too bad

[cutieface2007]

her fucking accent is to thick i cant understand her