Today, the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) - which recently completed the largest survey ever taken of the early universe - has released all of its immense, information-rich database to the public. Built from more than half a petabyte of raw and processed data, it will allow astronomers to study how the first galaxies formed and evolved, measure how gas and stars were distributed within these galaxies, map the large-scale structure of the cosmos, and investigate rare and unexpected objects not easily found in traditional surveys.
HETDEX observations make use of a technique called spectroscopy. With it, light is broken apart into its various wavelengths: a spectrum. Astronomers examine spectra (the plural of “spectrum”) for peaks and valleys which tell them about an object’s chemistry, movement through space, and distance from Earth.
The HETDEX database contains a whopping 600 million spectra for a period of history known as Cosmic Noon, 10 billion to 12 billion years ago.
“This is a spectral map of the universe. It turns every point of light into a barcode of physics,” said Erin Mentuch Cooper, HETDEX data manager and lead author on the paper announcing the release . “The real excitement is what happens when thousands of astronomers start exploring it.”
From 2017 to 2024, the Hobby-Eberly Telescope at McDonald Observatory surveyed a region of night sky equivalent to 2,000 full Moons, creating a map of the distant universe. HETDEX is using that map to solve the riddle of dark energy, the unknown substance causing our universe to expand more and more quickly over time. To do this, it is charting the location of over a million early galaxies. However, it has also gathered data on all of the space in between.
“The survey is untargeted,” explained Karl Gebhardt, HETDEX principal investigator, chair of UT Austin’s astronomy department, and co-author on the paper. “We aren’t picking and choosing specific objects to observe. Instead, we’re pointing one of the world’s largest telescopes at the sky and seeing what’s out there. We fully expect to find some really cool, wild stuff hiding in the data.”
The database consists of 431,000 data cubes that map information into three-dimensional space. When measured on the sky, each is roughly one thirtieth the size of the full Moon. Most correspond to regions around the Big Dipper and Orion.
“HETDEX gives us an unusually wide and detailed spectroscopic view of the universe at a time when most stars were being formed,” said Gebhardt. “Because the telescope and its instrumentation can capture tens of thousands of spectra at once, we can map galaxies across enormous cosmic volumes in a way that was not possible before. There’s a lot of potential here.”
In addition to raw data, the release also contains a catalog of every object HETDEX has found so far: over one million distant galaxies, half a million nearby star-forming galaxies, 18,000 supermassive blackholes, and over 150,000 stars. Scientists, students, and citizen researchers can download customized subsets of data based on sky location. Or, thanks to a close collaboration with UT Austin’s Texas Advanced Computing Center , they can perform large-scale analysis using high-performance, cloud-based supercomputing resources, dramatically lowering the barrier to entry for working with data of this scale.
While the release is based on half a petabyte of data, the team was able to process it down to a more manageable 10 terabytes. It also developed extensive tutorials and tools to help users – both human and AI - to make the most of this massive, complex dataset.
“It's been so important for me to make it as accessible as possible,” said Mentuch Cooper. “We’ve turned more than half a billion spectra into something you can actually explore. It’s like compressing a universe of information into something you can hold in your hands.”
Due to the depth of the HETDEX database, AI is expected to play a major role in sorting through it all. And, in fact, AI has already been pivotal in its creation. For example, software provided by RAIC Labs automatically removed contamination from satellites and meteors crossing in front of the telescope. HETDEX also used automated methods to comb through its observations and identify possible early galaxies. In parallel, more than 24,000 citizen scientists helped confirm the presence of these galaxies through the Dark Energy Explorers program.
Today’s release marks the first time the full HETDEX dataset and survey catalog have been made available together. While the core survey is now complete, observations are ongoing, calibrations continue to improve, and supplementary releases are expected for the future.
To access the data and learn more, visit hetdex.org .
The Astrophysical Journal
HETDEX Public Data Release 1: Source Catalog 2 and Datacubes from ∼ 90 deg2 of Integral-Field Optical Spectroscopy
3-Jun-2026