The 1st Generation of Stars

Andy_Howell writes "Astronomers may have found members of the first generation of stars in the universe. Using the Hubble Space Telescope and the Keck I telescope, they observed a faint red blob that had been magnified into a double image by a gravitational lens. The blob was found to be a cluster of stars 13.6 billion light years away, seen when the age of the universe was less than a billion years old. The clump appears to contain only about a million stars, and is less than a few million years old. It is thought that swarms of these clumps came together over the age of the universe to create the galaxies we see today."

Comments

Age of the universe?

[sjbe]

The blob was found to be a cluster of stars 13.6 billion light years away, seen when the age of the universe was less than a billion years old.

Perhaps I've been out of touch with my astronomy studies for too long, I know there are a lot of discoveries being made. However I was under the impression that there was still a great deal of uncertainty about the age of the universe. It was generally agreed that it was somewhere between about 13 billion and 20 billion years old but exactly how old wasn't/isn't clear.

Is there something I don't know about or is this age prediction just an assumption? Have there been some consensus on this recently that I didn't hear about? Anyone know for sure? I'm always suspicious when I see "discoveries" like this whose results depend on something that hasn't been definitely proven.

Why Curisoty Based Research?

[JohnDenver]

"It is a profound and necessary truth that the deep things in science are not found because they are useful; they are found because it was possible to find them." -Robert Oppenheimer

Robert Moody from the Department Mathematical Sciences, University of Alberta illustrates the importance of curiosity based research in his paper using lasers as an example of why curiosity based research is necessary.

Carl Sagan in his book, The Demon Haunted World, also stresses the importance of curiosity based research using James Clark Maxell's discoveries as an example of how it effects our lives today by providing the necessary building blocks for radio, television, computers, lasers, etc.

Basic science is nice, but erstwhile star captains probably wouldn't find the universe's origins very relevant.

It may not seem very relivant at first, but there are those who would argue in order to even begin to piece together data for a theory of everything (which may be vital to even approach the idea of star captains), we need to gather as much data as possible to reduce our error bars of knowledge.

All in all, Good question... I'm sure some of you have better answers...

Re: Red Shift

[Captn Pepe]

IANAAstroPhysicist, so whether this explains the visibly red shift (since scientific spectrographs are much more sensitive than our eyes ), I cannot say.

Bingo! The article mentioned that this star cluster was found at a redshift of z=5.58 I believe. The formula of interest here is that

1+z=(Lamda_em - Lamda_ob)/Lamda_ob

This means that the light we observe from this star cluster is arriving at a bit less than a quarter of its original wavelength -- the red light seem in the picture was emitted as hard ultraviolet radiation from young massive stars! Yes, young stars are really hot.

If you think that's impressive, consider the quasars the Sloan Digital Sky Survey keeps finding out at z>6. We see them as faint red dots, but they are actually outshining entire galaxies, mostly in the form of hard X-rays. And then there's the cosmic microwave background, sitting out there at z~1300. That was once a sea of energetic photons, just slightly too cool to ionize all the hydrogen in the universe; now it is a 2.7 degree Kelvin hiss in your radio.

Executive summary: you'd better believe you can see cosmological redshifts.

Oh, and PS -- don't ever call it a "doppler shift", that really pisses off cosmologists (or at least the ones in my department). Doppler shifts are the result of objects moving toward/away from you emitting photons that are a different wavelength in your rest frame. In the case of cosmological redshifts, the objects in question are not only not moving away from us, but general relativity doesn't even have a concept of "relative velocities" on these scales. Instead, the photons are actually arriving with a different wavelength, because space expanded underneath them en route.

If you aren't sure there is a difference, try this thought experiment: an observer and an emitter are at relative rest in a static universe, when a photon is emitted. While the photon is in transit, the observer and emitter move farther apart, then come to rest again. The observer sees the photon at its original wavelength, since the motion occurred totally independantly of the photon. Now imagine that, while the photon was en route, the universe expands for a little while. The observer and emitter are in the same end state (i.e. farther apart and at relative rest), but the photon arrives with a reduced wavelength, because this time space expanded underneath the photon.