By Daniel Dunaief
Ever since Ancient Romans and Greeks looked to the stars at night, humans have turned those pinpricks of light that interrupt the darkness into mythological stories.
Two years from now, using a state-of-the-art telescope located in Cerro Pachón ridge in Northern Chile, scientists may take light from 12 billion light years away and turn it into a factual understanding of the forces operating on distant galaxies, causing the universe to expand and the patterns of movement for those pinpricks of light.
While they are awaiting the commissioning of the Vera C. Rubin Observatory, researchers including Brookhaven National Laboratory Physicist Anže Slosar are preparing for a deluge of daily data — enough to fill 15 laptops each night.
An analysis coordinator of the Large Synoptic Survey Telescope’s dark energy science collaboration, Slosar and other researchers from around the world will have a unique map with catalogs spanning billions of galaxies.
“For the past five years, we have been getting ready for the data without having any data,” said Slosar. Once the telescope starts producing information, the information will come out at a tremendous rate.
“Analyzing it will be a major undertaking,” Slosar explained in an email. “We are getting ready and hope that we’ll be ready in time, but the proof is in the pudding.”
The Vera C. Rubin Observatory is named for the late astronomer who blazed a trail for women in the field from the time she earned her Bachelor’s Degree from Vassar until she made an indelible mark studying the rotation of stars.
Slosar called Rubin a “true giant of astronomy” whose work was “instrumental in the discovery of dark matter.”
Originally called the Large Synoptic Survey Telescope (LSST), the Rubin Observatory has several missions, including understanding dark matter and dark energy, monitoring hazardous asteroids and the remote solar system, observing the transient optical sky and understanding the formation and structure of the Milky Way.
The study of the movement of distant galaxies, as well as the way objects interfere with the light they send into space, helps cosmologists such as Slosar understand the forces that affect the universe as well as current and ancient history since the Big Bang.
According to Slosar, the observatory will address some of its goals by collecting data in five realms including examining large structures, which are clustered in the sky. By studying the statistical properties of the galaxies as a function of their distance, scientists can learn about the forces operating on them.
Another area of study involves weak lensing. A largely statistical measure, weak lensing allows researchers to explore how images become distorted when their light source passes near a gravitational force. The lensing causes the image to appear as if it were printed on a cloth and stretched out so that it becomes visually distorted.
In strong lensing, a single image can appear as two sources of light when it passes through a dense object. Albert Einstein worked out the mathematical framework that allows researchers to make these predictions. The first of thousands of strong lensing effects was discovered in 1979. Slosar likens this process to the way light behind a wine glass bends and appears to be coming from two directions as it passes around and through the glass.
The fourth effect, called a supernova, occurs when an exploding star reaches critical mass and collapses under its own weight, releasing enough light to make a distant star brighter than an entire galaxy. A supernova in the immediate vicinity of Earth would be so bright, “it would obliterate all life on Earth.”
With the observatory scanning the entire sky, scientists might see these supernova every day. Using the brightness of the supernova, scientists can determine the distance to the object.
Scientists hope they will be lucky enough to see a supernova in a strongly lensed galaxy. Strong lensing amplifies the light and would allow scientists to see the supernova that are otherwise too distant for the telescope to observe.
Finally, the observatory can explore galaxy clusters, which are a rare collection of galaxies. The distribution of these galaxies in these clusters and how they are distributed relative to each other can indicate the forces operating within and between them.
The BNL scientist, who is originally from Slovenia, is a group leader for the BNL team, which has seven researchers, including post docs. As the analysis coordinator of the dark energy science collaboration, he also coordinates 300 people. Their efforts, he said, involve a blend of independent work following their particular interests and a collective effort to prepare for the influx of data.
Slosar said his responsibility is to have a big-picture overview of all the pieces the project needs. He is thrilled that this project, which was so long in the planning and development stage, is now moving closer to becoming a reality. He said he has spent five years on the project, while some people at BNL have spent closer to 20 years, as LSST was conceived as a dark matter telescope in 1996.
Scientists hope the observatory will produce new information that informs current understanding and forms the basis of future theories.
As a national laboratory, BNL was involved in numerous phases of development for the observatory, which had several different leaders. The SLAC National Accelerator in Stanford led the development of the camera that will be integrated into the telescope. BNL will also continue to play a role in the data analysis and interpretation.
“Fundamentally, I just want to understand how the universe operates and why it is like this and not different,” said Slosar.