The Universe is expanding and any student of astronomy will vouch to this fact. However according to a team of astronomers the acceleration of the universe may not be as quick as it was assumed earlier.
A team of astronomers have discovered that certain types of supernova are more varied than earlier thought of and in the process have led to the biggest mystery of the universe-how fast is the universe expanding after the big bang?
The distance of objects with the aid of our binocular vision and the best space-based telescopes and most sophisticated techniques works out in the range of ten or twenty thousand light years. However as compared to the vastness of space, this is just pea nuts.
For Distances greater than that it is imperative to compare the absolute and observed brightness of well understood objects and to use the difference to determine the object’s distance.
In astronomy it is difficult to find an object of known brightness since there are examples of both bright and dim stars and galaxies. However there is one event which can be used to work out its absolute brightness. Supernovas are the final stages of a dying star and it explodes with such violence, the flash can be seen across the vast universe.
Type la Supernovae occurs in a binary star system when a white dwarf scoops off mass from its fellow star. This reproducible mechanism gives a well determined brightness and therefore scientists term such Type la supernovae as ‘standard candles’.
Astronomers found that the Type la supernovae is so uniform that it has been designated as cosmic beacons and used to assess the depths of the universe. It is now revealed that they fall into different populations and are not very uniform as previously thought. .
Peter A. Milne of the University of Arizona said, “We found that the differences are not random, but lead to separating Ia supernovae into two groups, where the group that is in the minority near us are in the majority at large distances — and thus when the universe was younger, there are different populations out there, and they have not been recognized. The big assumption has been that as you go from near to far, type Ia supernovae are the same. That doesn’t appear to be the case.”
The discovery throws new light on the currently accepted view of the universe expanding at a faster and faster rate pulled apart by an unknown force called dark energy this observation resulted in 2011 Nobel Prize for Physics.
Milne said, “The idea behind this reasoning, is that type Ia supernovae happen to be the same brightness — they all end up pretty similar when they explode. Once people knew why, they started using them as mileposts for the far side of the universe.The faraway supernovae should be like the ones nearby because they look like them, but because they’re fainter than expected, it led people to conclude they’re farther away than expected, and this in turn has led to the conclusion that the universe is expanding faster than it did in the past.”
The researchers felt that the accelerating universe can be explained on the basis of color difference in between two groups of supernova leaving less acceleration than earlier assumed and in the process will require lesser dark energy.
Milne said, “We’re proposing that our data suggest there might be less dark energy than textbook knowledge, but we can’t put a number on it, until our paper, the two populations of supernovae were treated as the same population. To get that final answer, you need to do all that work again, separately for the red and for the blue population.
Type la supernovae are considered as a benchmark for far away sources of light they do have a fraction of variability which has limited our knowledge of the size of the universe.