Astronomers Detect the Earliest Galaxies 127
FiReaNGeL writes "Astronomers, using NASA's Hubble Space Telescope, have uncovered a primordial population of compact and ultra-blue galaxies that have never been seen before. They are from 13 billion years ago, just 600 to 800 million years after the Big Bang. These newly found objects are crucial to understanding the evolutionary link between the birth of the first stars, the formation of the first galaxies, and the sequence of evolutionary events that resulted in the assembly of our Milky Way and the other 'mature' elliptical and majestic spiral galaxies in today's universe."
Very cool (Score:4, Informative)
Re:Wow, that's astounding (Score:3, Informative)
Re:Ultra-Blue? (Score:3, Informative)
Re:Ultra-Blue? (Score:3, Informative)
mdsolar said why they're called blue -- cus that's the color of light they're emitting.
They are extremely red-shifted (in fact astronomers typically talk about such distances/timescales in terms of degree of red-shift). It's not like if you were to peer at these galaxies in a telescope they'd look blue. In fact you probably wouldn't see anything at all; Hubble is almost certainly (huh? rtfa?) using it's near-infrared cameras for this.
Re:Ultra-Blue? (Score:4, Informative)
Re:Ultra-Blue? (Score:2, Informative)
-you don't know what it is made of
All you have to do is run a spec analysis on the light rays. Each element produces a specific light band pattern. This can be blue/red shift calibrated
-and you don't know how fast its relative motion is
Actually you can. That's EXACTLY what red/blue shift is.
How can you use red shift to predict relative motion? A shift implies a motion, and you don't know where it is moving from.
Doesn't matter where it is moving from. It matters how it is moving RELATIVE to you the observer.
How can you make any prediction about composition if you can't be sure of the shift?
Because the element based bands, while they can shift frequency, DO NOT CHANGE RELATIVE TO EACHOTHER!
How can you make and prediction about distance if you are making up numbers about the previous two?
They are not making them up.
I've got to read a book or two on cosmology sometime. I suspect there is a lot of 'splaining left out.
Or a few dozen...
And I would expect the oldest galaxies to have the least amount of hydrogen left, having had stars burning it the longest.
Yes but considering most of the observable universe appears to be hydrogen that's a SHIT LOAD of mass to burn through.
Re:just a thought (Score:3, Informative)
According to TFA, hydrogen re-ionization when most of the universe was still opaque, gassy hydrogen and was not burning in the form of stars, blocks almost all of the light from 400 million to 900 million years after the BB. The only reason these galaxies were visible is because they believe they had extremely efficient hydrogen ionization, which is also why they were so blue. Before 400 million years post BB you have stars and galaxies only just forming, so I don't think there would be much in the way of light at all to be seen.
Also remember that the Big Bang is not an explosion in space, it's an explosion of space, so there might not be any visible light emmitted at all from the very beginning.
Re:Really? (Score:5, Informative)
Here is a classic paper on galaxy formation: http://articles.adsabs.harvard.edu/full/1977MNRAS.179..541R [harvard.edu] you can get rough timescales from there. More modern treatments include early clustering of dark matter to speed the process along. Dark matter obviates the need to worry about cooling times to some extent though consideration of lithium hydride cooling may be important before the first prompt supernovae provide some metals (most likely pair-instability SNe). You can find out more in my paper linked above.
Re:Ultra-Blue? (Score:5, Informative)
Elements emit light at characteristic colors - frequencies of light. Eg, copper emits a bluish green color. By looking at the spectrum of the object, you can tell what the object is made of. If an object is moving, the spectrum will be shifted relative to normal due to the doppler effect. If it is shifted to higher frequencies the object is approaching you. If the spectrum is red shifted, it is moving away. The greater the shift, the greater the velocity.
Certain stars are close enough to Earth that we can triangulate their distance, using the orbit of the earth as the base of the triange. There is a certain class of star called a cepheid variable, some of which are in triangulateable range. Cepheids give off regular bursts of light, and due to the process by which they do that, the amount of light they give off is proportional to the frequency of the bursts. By using the inverse square law you can tell how far away a cepheid is by its brightness.
Thus, you can tell how far away a galaxy is by looking at its cepheid stars. So, by careful observation, you can detect the composition, speed, direction, distance, and age of a star. By looking at many stars, you can detect patterns like: the farther away a star is, the faster it is moving away from us.
Hubble NewsCenter link (Score:3, Informative)
The corresponding Hubble NewsCenter article [hubblesite.org] includes more details and more, larger images.
Re:Stupid question (Score:3, Informative)