24 June 2022

Dark Energy Explorers: Using Citizen Science to Enhance the Hobby-Eberly Telescope Dark Energy Experiment

Lindsay House
University of Texas at Austin

Dark energy is arguably the most significant scientific mystery of our time. Although it comprises approximately 70% of the universe, we have yet to identify what dark energy is. This would be analogous to us, here on Earth, not knowing what water is, only knowing that some mysterious substance covers 70% of the planet’s surface. Dark Energy Explorers is an online citizen science project working to understand the mystery of dark energy while simultaneously bringing accessible educational opportunities to people all over the world. In a little over a year, Dark Energy Explorers has produced 3.5 million classifications by more than 9,000 volunteers in more than 80 countries around the world. 

The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), shown in Figure 1, is central to the Dark Energy Explorer initiative. This instrument is working to constrain dark energy by collecting large amounts of data from regions of the early universe that have not previously had significant observations. HETDEX will obtain data of over one million redshifts of distant galaxies 9–11 billion light-years away, in addition to millions of other astronomical objects like stars, meteors, and black holes. We will use these galaxies to create a map of the large-scale structure of the universe, which will show the effects of dark energy at different epochs throughout history.


Figure 1. The Hobby-Eberly Telescope located at McDonald Observatory in West Texas.
Figure 1. The Hobby-Eberly Telescope located at McDonald Observatory in West Texas. [Martin Harris/McDonald Observatory]


In some cases, the human eye’s pattern recognition ability is more powerful than any existing computer algorithm. The data we collect of galaxies from the Hobby-Eberly Telescope are most effectively understood by human visual vetting. HETDEX has been collecting data since 2017 and will continue to do so until 2024. Thus far, data collection is 50% complete. 

With close to 100 terabytes of data collected already — data which are most accurately classified by the human eye — we had a serious time efficiency problem. To solve this problem, we designed, created, and launched the worldwide citizen science project, Dark Energy Explorers, in February 2021 on Zooniverse, the world’s largest citizen science platform. We developed an easy-to-understand tutorial to train members of the public to become a HETDEX astronomer by simplifying the classification process into digestible, jargon-free tasks. For example, a nearby galaxy appears as a large, bright dot on our telescope image, while distant galaxies are small and faint. Figure 2 shows an example of the mobile app interface and an example of each galaxy for the “Nearby vs Distant” workflow. In addition, we have another workflow for participants to choose called “Fishing for Signal in a Sea of Noise,” in which users differentiate between the real astronomical objects and telescope noise. 

The objects in Dark Energy Explorers have never been seen by anyone before, so it is a unique opportunity to excite scientists of all ages by allowing participants the first look at newly discovered galaxies. Our experienced participants who classify more than 50 galaxies receive a pop-up message from the HETDEX team that invites them to learn about general astronomy, dark energy, and HETDEX. This “level-up” incentive provides continued engagement with the project and educates the public about astrophysics topics. More than 40% of our volunteers have taken advantage of this feature. 

So far, Dark Energy Explorers has reduced our team’s visual vetting work by 90%, making this research viable; it would have otherwise been impossible with our small team. This project is an innovative approach to studying dark energy and to classifying large datasets that require visual vetting. 

HETDEX is only about 50% complete and will continue collecting data for the next few years. Therefore, there is still a huge need for classifications and volunteers to make them! If you're interested in becoming a Dark Energy Explorer or using it in your classroom, just follow the steps below to get started! We'd love to know if Dark Energy Explorers can work with your educational goals. When there is enough interest, we have run workshops for high school teachers and events with large groups of undergraduates. Together, our explorations might help unravel the mystery of dark energy!


Want to become a Dark Energy Explorer?

  1. Go to Zooniverse.org
  2. Create an account with username and password (this saves your classifications)
  3. Go to Projects > Space Science or Physics Projects > Dark Energy Explorers
  4. Once you are at Dark Energy Explorers homepage, select “Get Started” and then choose the workflow “Fishing for Signal in a Sea of Noise" or “Nearby vs Distant Galaxy”
  5. Complete the tutorial and you’re ready to be the first person to view these astronomical objects!
Figure 2. The above image is the mobile app version of Dark Energy Explorers. The left image shows an example of a "Nearby Galaxy or Star." The right image shows an example of a "Distant Galaxy."
Figure 2. The above image is the mobile app version of Dark Energy Explorers. The left image shows an example of a "Nearby Galaxy or Star." The right image shows an example of a "Distant Galaxy."