New "pinprick" dataset of the MilkyWay. (DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA.) Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

Milky Way survey reveals billions of celestial objects

It is the largest such catalog ever produced from a single camera, “in terms of the number of objects observed,” according to researcher Andrew Saydjari.

A massive survey of the Milky Way galaxy’s plane captured an astronomical tapestry of 3.32 billion celestial objects — making this dataset the largest of its kind ever collected, according to a NOIRLab news release.

The survey, which is being called the Dark Energy Camera Plane Survey (DECaPS2), will help researchers model the three-dimensional structure of the Milky Way’s stars and dust in unprecedented detail.

“This is quite a technical feat. Imagine a group photo of over three billion people and every single individual is recognizable,” said Debra Fischer, division director of Astronomical Sciences at the U.S.-based National Science Foundation (NSF), in a statement. 

She added that astronomers “will be poring over this detailed portrait of more than three billion stars in the Milky Way for decades to come.”

The Milky Way. | SkyNews
The Milky Way. (DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA. Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)
(DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA/E. Slawik Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)) | SkyNews
Close-up view of survey section. (DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA/E. Slawik) Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

Most stars and dust in the Milky Way are at its disk where the spiral arms lie. The dark tendrils of dust and light from diffuse nebulae makes observing the galactic plane hard to observe for astronomers. The number of stars can also overlap in images, making it difficult to distinguish individual stars from their neighbours.

But observing the galactic plane is the best way for astronomers to understand the Milky Way, and this region of space at near-infrared wavelengths cuts through much of the light-absorbing dust. 

A team of international astronomers in Canada, the United States and Germany took two years to complete the task. The data was collected by the Dark Energy Camera at the NSF’s Cerro Tololo Inter-American Observatory in Chile. 

The effects of nebulae and crowded star clusters was mitigated, thanks to advancements in data processing. Astronomers used this approach to predict the backgrounds behind each star, making the final processed data more accurate.

The result is an optical and near-infrared survey of the Milky Way as seen from the southern sky. The first dataset, DECaPS, was released in 2017. The new data brings total coverage of the night sky to 6.5 per cent. It spans 130-degrees in length, or 13,000 times the angular area of the full Moon. The dataset takes up more than 10 terabytes of data from 21,400 individual exposures.

“One of the main reasons for the success of DECaPS2 is that we simply pointed at a region with an extraordinarily high density of stars and were careful about identifying sources that appear nearly on top of each other,” said Andrew Saydjari, a researcher at Harvard and Smithsonian Center for Astrophysics, in a statement.

Saydjari, who is also the  lead author of a paper on DECaPS2 in the Astrophysical Journal Supplement, also noted that the approach his team took allowed them to  produce the “largest such catalog ever from a single camera, in terms of the number of objects observed.”

The dataset can be viewed with the Legacy Survey Viewer, the World Wide Telescope, and Aladin.