PUNE: An international team of researchers has made a deep and wide map of
dark matter in the universe which will help further study. Dark matter and dark energy take up almost 95% of the universe.
Dark matter is responsible for the formation of galaxies in the universe while dark energy accelerates the universe’s ongoing expansion.
The map is a three dimensional model of how the universe looked in a particular time frame. It tells scientists how the universe looked from about 6 giga years ago till how it was about 1giga years ago. One billion years make one giga year.
The paper is titled “Cosmology from cosmic shear power
spectra with Subaru Hyper Suprime-Cam first-year data”. The team will submit its findings to the Publication of Astronomical Society of
Japan for peer review.
Surhud More from the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune, who is the only Indian in this global team, designed the method to calculate the distance of about 10 million galaxies for making this map.
More also designed a blind analysis for the results. The study, More said, will help understand the properties of dark energy including the possibility of 'ripping apart' of galaxies.
He is from Mushet near Alibaug and studied at Fergusson College and IIT Bombay and went abroad for studies.
The mystery shrouding dark matter gives it its name. It doesn’t interact with light but its gravitational field can bend light and through this bending, scientists try to study dark matter.
More said one must look back at the universe at its inception. “Dark matter was spread across everything, fairly uniformly but with very tiny lumps. These lumps grow because of gravity and lead to the formation of stars and galaxies that we see today. Now, because dark energy is present in the universe, and it causes an accelerated expansion, the evolution and growth of lumps is affected. Through the map, we can study the amount of lumpiness and measure how they evolved over time. This in effect, helps us understand the evolution of dark matter and dark energy itself,” he said.
Albert Einstein’s general theory of relativity says this acceleration can be described by a constant number. Scientists are trying to find if dark energy behaves like Einstein's simple constant.
More added that dark matter, with all its gravity, should have reduced the speed of the expansion of universe. “Dark energy causes it to expand at an accelerated rate. At some point, dark energy could potentially cause the universe to rip apart. Hence, we need to study how dark energy will behave so as to know if and when this ripping apart will happen. The map that we have designed will help researchers understand it,” he said.
Light takes time to reach us and would have bent in different ways due to the influence of dark matter. Light has a constant speed which means we can deduce how far it is coming from and hence understand the galaxies at that time and distance, he added.
The Hyper Suprime-Cam is still taking images, and is scheduled to finish around 2020 and the amount of data collected and interpreted will further our understanding of the dark energy as well as the universe, More said.
Gravitational lensing is a phenomenon predicted by Einstein where gravity can bend the path of light, making far away galaxies appear distorted to observers on Earth.
The research team studied the minute distortions caused by gravitational lensing to reconstruct where matter is distributed in the universe.
The team can see how fluctuations of dark matter across the sky have changed over billions of years, and how dark energy has influenced this growth of structure, the IUCAA release said.
The new 3d map of dark matter made by using the Subaru Hyper Suprime- Cam data 
