Dark Energy Camera Unveils Billions of Celestial Objects in Unprecedented Survey of the Milky Way

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Dark Energy Camera Unveils Billions of Celestial Objects in Unprecedented Survey of the Milky Way

Astronomers have released a gargantuan survey of the galactic plane of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. Credit: DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA, Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

NSF’s NOIRLab releases colossal astronomical data tapestry displaying the majesty of our Milky Way in unprecedented detail.

This unprecedented collection was captured by the Dark Energy Camera (DECam) instrument on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab. CTIO is a constellation of international astronomical telescopes perched atop Cerro Tololo in Chile at an altitude of 2200 meters (7200 feet). CTIO’s lofty vantage point gives astronomers an unrivaled view of the southern celestial hemisphere, which allowed DECam to capture the southern Galactic plane in such detail.

Astronomers have released a gargantuan survey of the galactic plane of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. The data for this unprecedented survey were taken with the US Department of Energy-fabricated Dark Energy Camera at the NSF’s Cerro Tololo Inter-American Observatory in Chile, a Program of NOIRLab. The survey is here reproduced in 4000-pixels resolution to be accessible on smaller devices. Credit: DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA, Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

DECaPS2 is a survey of the plane of the Milky Way as seen from the southern sky taken at optical and near-infrared wavelengths. The first trove of data from DECaPS was released in 2017, and with the addition of the new data release, the survey now covers 6.5% of the night sky and spans a staggering 130 degrees in length. While it might sound modest, this equates to 13,000 times the angular area of the full Moon.

Most of the stars and dust in the Milky Way are located in its disk — the bright band stretching across this image — in which the spiral arms lie. While this profusion of stars and dust makes for beautiful images, it also makes the Galactic plane challenging to observe. The dark tendrils of dust seen threading through this image absorb starlight and blot out fainter stars entirely, and the light from diffuse nebulae interferes with any attempts to measure the brightness of individual objects. Another challenge arises from the sheer number of stars, which can overlap in the image and make it difficult to disentangle individual stars from their neighbors.

Astronomers have released a gargantuan survey of the galactic plane of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. The data for this unprecedented survey were taken with the US Department of Energy-fabricated Dark Energy Camera at the NSF’s Cerro Tololo Inter-American Observatory in Chile, a Program of NOIRLab. For reference, a low-resolution image of the DECaPS2 data is overlaid on an image showing the full sky. The callout box is a full-resolution view of a small portion of the DECaPS2 data. Credit: DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA/E. Slawik, Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

Despite the challenges, astronomers delved into the Galactic plane to gain a better understanding of our Milky Way. By observing at near-infrared wavelengths, they were able to peer past much of the light-absorbing dust. The researchers also used an innovative data-processing approach, which allowed them to better predict the background behind each star. This helped to mitigate the effects of nebulae and crowded star fields on such large astronomical images, ensuring that the final catalog of processed data is more accurate.

This image, which is brimming with stars and dark dust clouds, is a small extract — a mere pinprick — of the full Dark Energy Camera Plane Survey (DECaPS2) of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. The data for this unprecedented survey were taken with the US Department of Energy-fabricated Dark Energy Camera at the NSF’s Cerro Tololo Inter-American Observatory in Chile, a Program of NOIRLab. Credit: DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA, Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

“Since my work on the Sloan Digital Sky Survey two decades ago, I have been looking for a way to make better measurements on top of complex backgrounds,” said Douglas Finkbeiner, a professor at the Center for Astrophysics, co-author of the paper, and principal investigator behind the project. “This work has achieved that and more!”

“This is quite a technical feat. Imagine a group photo of over three billion people and every single individual is recognizable!” says Debra Fischer, division director of Astronomical Sciences at NSF. “Astronomers will be poring over this detailed portrait of more than three billion stars in the Milky Way for decades to come. This is a fantastic example of what partnerships across federal agencies can achieve.”

DECam was originally built to carry out the Dark Energy Survey, which was conducted by the Department of Energy and the US National Science Foundation between 2013 and 2019.

This dataset was presented in the paper “The Dark Energy Camera Plane Survey 2 (DECaPS2): More Sky, Less Bias, and Better Uncertainties” to appear in the Astrophysical Journal Supplement.

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