After two years collecting data and processing numbers, a team of astronomers took a picture of literally cosmic proportions. It is full of stellar perfection: the image shows reddish-brown dust clouds clustered along the center line of our Milky Way, replete with over 3 billion dots of light – almost all stars, a dim nearby galaxy here or there.
The project, based at the Harvard-Smithsonian Center for Astrophysics, is called the Dark Energy Chamber Survey and aims to index celestial objects located in our galactic plane. In January researchers published their second data release V A series of applications to the astrophysical journal, making it the largest catalog or index of stars ever assembled with a single instrument, and one of the few times we have pointed a camera at the center of our own galaxy. It’s a space selfie, if you will.
But while the stars are the main decoration, the other point of this review is capturing the elusive stuff drifting among them: dust. Because dust masks light, it distorts our view of the cosmos. Knowing how many are out there could help astronomers filter their effect on their data and more accurately estimate the chemical composition and positions of stars. Over the next decade, scientists will use this catalog to refine maps of galactic dust, track ancient star systems, and study the formation and structure of our Milky Way.
For the survey, the research team repurposed the Dark Energy Camera, or DECam, an optical instrument at the Cerro Tololo Inter-American Observatory in Chile, which was originally built to study faint objects far from the galactic plane. “We took this instrument, which was built for cosmology,” says Eddie Schlafly, an astronomer at the Space Telescope Science Institute, “and aimed it straight at the center of the galactic plane, where there are tons and tons of stars, dust and gas. and nebula. The goal, he said, was to allow as many separate light sources as possible.
This is a rather difficult task: most astronomers refuse to observe the galactic plane, because it is notoriously difficult to depict. The Milky Way is a spiral galaxy. So most of its stars are in a flat pancake,” says Andrew Saijari, a Harvard University graduate student who led the study. Unfortunately for observers on Earth, we are sitting right in the middle of this pancake. On this disk it is easy to see above or below our plane, where the stellar haze is thin. But looking into the center of the galaxy or back to the outer edge is difficult because the view is crowded. “Many stars can appear to be stacked on top of each other,” says Saijari.
Other things hanging around the galactic center don’t help. Some gases, for example, are hot enough to emit their own photons, a color similar to starlight. And dust can make celestial objects appear dimmer and redder than they really are. Both can distort astronomical measurements of the brightness and position of stars.