Current speculation by cosmologists puts the age of the universe at about twelve to thirteen billion years. This is based largely on the apparent age of the oldest stars, or better clusters of stars, or at any rate sources that exhibit a large red shift.
Until recently it was thought that supernovae, and in particular type 1A supernovae, were relatively rare. They are very faint, since the signals originate well over two billion years ago. But new techniques have succeeded in harvesting a dozen or more per year. Many are missed, and we are nearing the end of the line of these early supernovae. But we can conclude that if we had started to collect data, say three billion years ago, we would by now have observed about 1012 such type 1A supernovae (not to mention all the other ones). It would appear that they are the source, not only of the heavier elements, but of the background radiation that is still permeating the universe. It turns out that the smaller the star, (but at least 1.4 solar masses), the longer it can burn before exploding as a supernova. Those with a mass near 1.4 solar masses have a lifetime of about three billion years. Stars that have a smaller mass do not end as supernovae.
The small stars are those that lasted the longest and whose supernovae are still visible at present, the larger ones would have exploded and been seen much earlier. The time it takes for the light to reach us from the explosion, as can be inferred from the red shift, is upwards of about three billion years. (The relation of time to red shift is approximately linear out to about a value of the red shift, z, of 0.3 under any view.)
One thing is clear. If the type 1A supernovae come from stars created near the beginning of time then the arithmetic which combines their life time (about three billion years) with the time until the light from the explosion reaches us (also about three billion years) gives us an estimate of the age of the universe of about 6 billion years. That is less than one-half of the 12 or 13 billion years that is currently believed. There is no way around this. Current estimates of the age based on Hubble’s Law, based in the end on relativity theory, cannot be reconciled with these numbers.
We should also note that if we postulate a center of expansion and decreasing velocity of expansion as a function of time, we have the problem that we can never look back to the origin of time. In a geometric model, we are never more than 3 billion light years from the assumed origin, so the light we see from this region would have originated 3 billion years after the beginning of time in order to reach us now, (that is at the age of 6 billion years). Looking back to the beginning of time is an impossible task.
The values of z observed from type 1A supernovae point to a smaller and denser universe. An observed value of z = 1, that is a Doppler factor z + 1 = 2 would be achieved by the recession of the star at the speed c/2, and no movement of the receiver. Recession velocities greater than one-half the speed of light would result in values of z greater than one.
The universe, and the Doppler shifts resulting from 1A data, can be shown to be consistent with a Newtonian model with a present age of about six billion years, and a diameter of five to six billion light years. The age is, in any case, constrained by the time line – the lifetime of the star + the time until we see the supernova. The time for the star formation is a minute fraction of a billion years and can be ignored.