The Scale of the Map

This is not just a pretty picture; it's a massive scientific dataset. The map covers about three-quarters of the sky, providing a deep, unobstructed view of the extragalactic universe beyond the dust and stars of our own Milky Way . It contains roughly 4 billion objects, ranging from stars in our solar neighborhood to galaxies billions of light-years away .

How It Was Built

Creating this map was a monumental effort that spanned more than a decade:

• 13 years of observations: The data was collected over 2,285 nights, resulting in 263,407 individual telescope exposures .
• Three ground-based surveys: The map combines data from the Dark Energy Camera Legacy Survey (DECaLS), the Mayall z-band Legacy Survey (MzLS), and the Beijing-Arizona Sky Survey (BASS) .
• Additional data: Observations from NASA's WISE satellite and other public sources were incorporated to fill gaps in wavelength coverage .
• A large team: More than 160 scientists contributed to data collection, with a core team of 20 producing the final public dataset .
• Supercomputing power: Merging the images required about a year of code development and eight weeks of processing on the Perlmutter supercomputer at the National Energy Research Scientific Computing Center (NERSC) at Berkeley Lab .

Key Scientific Purposes

The 2D map is more than a static image; it is a foundation for some of the most ambitious projects in modern astronomy.

1. Foundation for the DESI 3D Survey
The map serves as the target-selection layer for the Dark Energy Spectroscopic Instrument (DESI). DESI uses this 2D map to select millions of galaxies and measure their distances, building the largest high-resolution 3D map of the universe . This 3D map is designed to help scientists understand the nature of dark energy, the mysterious force driving the universe's accelerating expansion .

2. Dark Matter and Dark Energy Research
By providing a comprehensive view of the distribution of galaxies and matter in the sky, the map allows scientists to study the large-scale structure of the universe. This is critical for mapping dark matter and tracking how dark energy has influenced cosmic expansion over time .

3. Discovery of Rare Phenomena
The sheer volume of data makes it a powerful tool for discovering rare and transient objects. Astronomers are already using it to search for gravitational lenses, supernovae, asteroids, and other unusual celestial phenomena .

4. Reference for Next-Generation Observatories
The map will serve as a vital baseline for comparing data from upcoming observatories, including the Vera C. Rubin Observatory and NASA's Nancy Grace Roman Space Telescope . This deep, wide-field view provides a historical snapshot against which future observations can be compared.

5. AI Training
The immense dataset — with its billions of classified objects — is ideal for training artificial intelligence tools to analyze petabyte-scale astronomical data automatically .

A Lasting Legacy

The scientific community has already embraced the DESI Legacy Surveys data. To date, more than 1,800 scientific papers have been published using earlier versions of this dataset . Researchers expect this new, comprehensive 2D map will remain the definitive view of the universe in two dimensions for years to come .

The Scale of the Map

This is not just a pretty picture; it's a massive scientific dataset. The map covers about three-quarters of the sky, providing a deep, unobstructed view of the extragalactic universe beyond the dust and stars of our own Milky Way . It contains roughly 4 billion objects, ranging from stars in our solar neighborhood to galaxies billions of light-years away .

How It Was Built

Creating this map was a monumental effort that spanned more than a decade:

• 13 years of observations: The data was collected over 2,285 nights, resulting in 263,407 individual telescope exposures .
• Three ground-based surveys: The map combines data from the Dark Energy Camera Legacy Survey (DECaLS), the Mayall z-band Legacy Survey (MzLS), and the Beijing-Arizona Sky Survey (BASS) .
• Additional data: Observations from NASA's WISE satellite and other public sources were incorporated to fill gaps in wavelength coverage .
• A large team: More than 160 scientists contributed to data collection, with a core team of 20 producing the final public dataset .
• Supercomputing power: Merging the images required about a year of code development and eight weeks of processing on the Perlmutter supercomputer at the National Energy Research Scientific Computing Center (NERSC) at Berkeley Lab .

Key Scientific Purposes

The 2D map is more than a static image; it is a foundation for some of the most ambitious projects in modern astronomy.

1. Foundation for the DESI 3D Survey
The map serves as the target-selection layer for the Dark Energy Spectroscopic Instrument (DESI). DESI uses this 2D map to select millions of galaxies and measure their distances, building the largest high-resolution 3D map of the universe . This 3D map is designed to help scientists understand the nature of dark energy, the mysterious force driving the universe's accelerating expansion .

2. Dark Matter and Dark Energy Research
By providing a comprehensive view of the distribution of galaxies and matter in the sky, the map allows scientists to study the large-scale structure of the universe. This is critical for mapping dark matter and tracking how dark energy has influenced cosmic expansion over time .

3. Discovery of Rare Phenomena
The sheer volume of data makes it a powerful tool for discovering rare and transient objects. Astronomers are already using it to search for gravitational lenses, supernovae, asteroids, and other unusual celestial phenomena .

4. Reference for Next-Generation Observatories
The map will serve as a vital baseline for comparing data from upcoming observatories, including the Vera C. Rubin Observatory and NASA's Nancy Grace Roman Space Telescope . This deep, wide-field view provides a historical snapshot against which future observations can be compared.

5. AI Training
The immense dataset — with its billions of classified objects — is ideal for training artificial intelligence tools to analyze petabyte-scale astronomical data automatically .

A Lasting Legacy

The scientific community has already embraced the DESI Legacy Surveys data. To date, more than 1,800 scientific papers have been published using earlier versions of this dataset . Researchers expect this new, comprehensive 2D map will remain the definitive view of the universe in two dimensions for years to come .