A new interactive map of the universe presents the entire span of the known cosmos in stunning detail and with pinpoint accuracy.
Astronomers created the map, which shows the positions and real colors of 200,000 galaxies, using two decades' worth of data collected by the Sloan Digital Sky Survey. The interactive map can be downloaded for free at mapoftheuniverse.net, allowing the public to access information that was previously available only to scientists.
"Growing up, I was very inspired by astronomy pictures, stars, nebulas and galaxies, and now it's our time to create a new type of picture to inspire people," Brice Ménard, a professor in the Johns Hopkins University Department of Physics and Astronomy and co-creator of the map, said in a statement. "Astrophysicists around the world have been analyzing this data for years, leading to thousands of scientific papers and discoveries."
Despite this effort, nobody had taken the time to create a map that is beautiful, scientifically accurate and accessible to the lay public.
"Our goal here is to show everybody what the universe really looks like," Ménard said.
The detailed map was possible thanks to the pioneering Sloan Digital Sky Survey, one of the most influential surveys in the history of astronomy. The survey is an ambitious effort to capture a huge proportion of the night sky through the 2.5-meter telescope at Apache Point Observatory in New Mexico. Every night for eight years, the telescope has aimed its 120-megapixel camera on 1.5 square degrees of the sky at a time — around eight times the area of the full moon — at slightly different locations, to capture a broad perspective of the universe.
Ménard and former Johns Hopkins computer science student Nikita Shtarkman used these data to recreate a slice of the universe containing 200,000 galaxies. Each dot on the map is a galaxy with billions of stars and planets. Our own galaxy, the Milky Way, is just one of these dots located at the very bottom of the map.
Let there be light
One notable aspect of this cosmic map is the striking colors that are in part created by the expansion of the universe. As the universe expands, the wavelengths of light traveling to Earth are stretched to redder regions of the electromagnetic spectrum. The more distant a light source, the more extreme this redshift.
At the very top of the map is the universe's first light, emitted around 13.7 billion years ago, shortly after the Big Bang, as the universe expanded and cooled enough to allow electrons to form atoms with protons. The reduction of free electrons meant that photons — individual packets of light that act as both particles and waves — were suddenly not being infinitely bounced around and were instead free to travel. In an instant, the universe effectively went from being opaque to transparent.
At the opposite end of the interactive map is the Milky Way, including the solar system and Earth as they exist today.
"In this map, we are just a speck at the very bottom, just one pixel," Ménard said. "And when I say 'we,' I mean our galaxy, the Milky Way, which has billions of stars and planets."
Ménard hopes that, in addition to displaying the universe in its full beauty, the interactive map will demonstrate the awe-inspiring scale of the universe.
"We are used to seeing astronomical pictures showing one galaxy here, one galaxy there, or perhaps a group of galaxies," he said. "But what this map shows is a very, very different scale. From this speck at the bottom, we are able to map out galaxies across the entire universe, and that says something about the power of science."