Astronomer Discovers the Most Distant Stars Ever Observed From Earth 291
Cryolithic writes to tell us The Vancouver Sun is reporting that a University of B.C. astronomer recently used NASA's Hubble telescope to see a cluster of stars one billion light-years from Earth, the farthest stars ever observed from Earth. From the article: "That's interesting, he explains, because given that light travels at a finite speed -- 300,000 km a second -- the light emitted from the star cluster he and Kalirai saw was emitted one billion years ago. That means the cluster as it appeared to them two months ago was the way it looked one billion years ago. In other words, they were looking one billion years back in time."
it travels as fast as it travels (Score:3, Informative)
Re:Looking back in time. (Score:1, Informative)
Re:only 1 billion ly? (Score:5, Informative)
Re:only 1 billion ly? (Score:2, Informative)
Re:paraphrasing Douglas Adams (Score:3, Informative)
A correction/explanation (Score:5, Informative)
From the article:
"That's because the older a star gets, the redder it gets, he says. Younger stars are bluer."
Kinda true, but the point is something else. A young *cluster* of stars will look blue because brightest stars in a young cluster are blue, massive stars. These blue bright stars burn their fuel (Hydrogen) very fast and have short lives (~100 Million years). When blue bright stars go away, more numerous, but much fainter, red stars start to dominate the color of the cluster. Therefore, as the *cluster* gets older, it gets redder.
Re:1 billion light years? (Score:5, Informative)
Re:1 billion light years? (Score:4, Informative)
Re:only 1 billion ly? (Score:3, Informative)
Re:Looking back in time. (Score:5, Informative)
Re:only 1 billion ly? (Score:3, Informative)
Re:it travels as fast as it travels (Score:2, Informative)
http://www.glenbrook.k12.il.us/gbssci/phys/class/
KFG
Re:Sounds familiar... (Score:3, Informative)
Re:1 billion light years? (Score:3, Informative)
The pulse rate of these stars is very tightly correlated with their absolute luminosity. A three-day period Cepheid has an absolute luminosity about 800 times the Sun. A thirty-day period Cepheid is about 10,000 times as bright as the Sun. The scale has been calibrated much more precisely than those approximations, using nearby Cepheid stars, where the distance can be determined accurately from parallax observations.
Minor variations in rate are closely connected to certain metallic ions found in these stars in various proportions, and this can easily be determined as well for new Cepheids, by spectroscope. True Cepheids are population 1 stars, but there is also a related type, called either Type 2 Cepheids or W Virginis variables. These are the older, population 2 versions of the same phenominon. At first, the mix of types 1 and 2 made distance estimate figures rather blurry for distant galaxies, but once it was recognized that they could be divided into the two types, not only did type 1 Cepheids give us some very accurate estimates, but type 2 can be used to get an independant estimate and so check the first one.
All Cepheids are tremendously bright, and can be picked out individually at distances enormously greater than can a sun sized star. The time for a brightness cycle is long enough that a lot of detailed measurements are possible, but short enough that it will repeat many times in a single researcher's working lifetime, making them ideal in many ways.
Re:only 1 billion ly? (Score:3, Informative)
we get the age and size from the frequency of the microwave background radiation.
The background is measured at 3.5 kelvin (degrees above absolute zero) which relates to the microwave frequency by wiens law (sorry very rusty on the details, frequency of the light given off by an object at a certain temperature is defined by the laws of thermodynamics, the hotter it is the shorter the wavelength).
when the big bang occurred particle physics can give a value for the temperature of the universe.
When you look at the oldest light it came from the glow of the universe at that temperature - and it started out with a wavelength related to that temperature.
That oldest light has been stretched by the red shift by the expansion rate of the universe and is now at a very long wavelength which we see as the microwave background radiation in every direction in space.
we can measure the rate of expansion of the universe by looking at standard candles (supernova which pop with the same brightness - so we know how far away they are by their brightness) and measure their red shift. So we know how much red shift occurs for a certain distance.
so if we look at how much red shift the oldest light has suffered from its original high frequency we can work out how far away it comes from - or how old it is - because it has traveled to us at the speed of light 3*10exp8 m/s.
The figure that comes out of this pile of logic is apparently around 13 billion years. Maybe someone can verify or correct that this is the logical linkage used in the calculation.
Re:Looking back in time. (Score:3, Informative)
Not quite. There are several possibilities. One is that the particles do actually exchange information using particles that travel faster than light. This information creates the statistics when the experiment is repeated several times, but cannot be directly observed or used to transmit tangible information. I consider this unlikely, because it just moves the wrinkle in the rug to the faster-than-light particles, which cannot even be observed.
A second possibility is that the particles have complex internal states that affect their statistics, but which cannot be directly observed. The internal states are synchronized when they are entangled, after which they evolve independently without further communication. For example, the universe could be a cellular automaton [wikipedia.org] and the particles persistent digital excitations; entanglement would be some sort of partial cloning of the digital state. (In terms of the EPR paradox [wikipedia.org], this is a non-local hidden variable approach.) This theory is also unsatisfying, because nothing suggesting this has been observed, and observing it would probably be damn difficult. On the other hand, it does explain how particles could exhibit randomized behavior that can only be desribed statistically (imagine encrypted messages for which you know neither the algorithm or the key).
A third possibility is that when particles are entangled, they still remain in contact in some geometric sense. For instance, time is stopped in a photon's frame of rest, so its origin and destination are in one sense located at the same point in space. This seems like a reasonable starting point to me: one of the rules of quantum mechanics is that if you add up the likelihood of finding a particle over all points in the universe, you always get exactly 100%. But how do you define a continuous sums-to-100% process over the entire universe, when there's a speed limit? In some sense, a single particle is already pulling an everywhere-at-once trick. Entangling two particles isn't really much of a leap.