Wielding state of the art technologies and techniques, a team of astrophysicists has added a novel approach to quantifying one of the most fundamental laws of the universe.
Cosmology is about understanding the evolution of our universe how it evolved in the past, what it is doing now and what will happen in the future.
Our knowledge rests on a number of parameters including the Hubble Constant that we strive to measure as precisely as possible.
In the early 20th century, Hubble became one of the first astronomers to deduce that the universe was composed of multiple galaxies. His subsequent research led to his most renowned discovery: that galaxies were moving away from each other at a speed in proportion to their distance.
Hubble originally estimated the expansion rate to be 500 kilometers per second per megaparsec, with a megaparsec being equivalent to about 3.26 million light years.
Hubble concluded that a galaxy two megaparsecs away from our galaxy was receding twice as fast as a galaxy only one megaparsec away.
This estimate became known as the Hubble Constant, which proved for the first time that the universe was expanding. Astronomers have been recalibrating it with mixed results ever since.
With the help of skyrocketing technologies, astronomers came up with measurements that differed significantly from Hubble’s original calculations slowing the expansion rate down to between 50 and 100 kilometers per second per megaparsec.
And in the past decade, ultra-sophisticated instruments, such as the Planck satellite, have increased the precision of Hubble’s original measurements in relatively dramatic fashion.
Gamma rays are the most energetic form of light. Extragalactic background light (EBL) is a cosmic fog composed of all the ultraviolet, visible and infrared light emitted by stars or from dust in their vicinity.
When gamma rays and EBL interact, they leave an observable imprint a gradual loss of flow that the scientists were able to analyze in formulating their hypothesis.
A common analogy of the expansion of the universe is a balloon dotted with spots, with each spot representing a galaxy. When the balloon is blown up, the spots spread farther and farther apart.
Matter the stars, the planets, even us is just a small fraction of the universe’s overall composition.
The large majority of the universe is made up of dark energy and dark matter. And we believe it is dark energy that is ‘blowing up the balloon.’ Dark energy is pushing things away from each other.
Gravity, which attracts objects toward each other, is the stronger force at the local level, which is why some galaxies continue to collide. But at cosmic distances, dark energy is the dominant force.
The analysis that have developed paves the way for better measurements in the future using the Cherenkov Telescope Array, which is still in development and will be the most ambitious array of ground-based high-energy telescopes ever.
The rate of interaction depends on the length that they travel in the universe. And the length that they travel depends on expansion. If the expansion is low, they travel a small distance.
If the expansion is large, they travel a very large distance. So the amount of absorption that we measured depended very strongly on the value of the Hubble Constant. What we did was turn this around and use it to constrain the expansion rate of the universe.