MAUVE: An ultraviolet astrophysics probe mission concept

For the past 30 years, NASA’s Great Observatories—the Hubble, Spitzer, Compton, and Chandra space telescopes—have revealed some amazing things about the universe. In addition to some of the deepest views of the universe provided by the Hubble Deep Fields campaign, these telescopes have provided insight into the unseen parts of the cosmos—i.e., in the infrared, gamma-ray, and ultraviolet spectrums.

With the success of these observatories and the James Webb Space Telescope (JWST), NASA is contemplating future missions that would reveal even more of the “unseen universe.”

This includes the UltraViolet Explorer (UVEX), a space telescope NASA plans to launch in 2030 as its next Astrophysics Medium-Class Explorer mission. In a recent study, a team led by researchers from the University of Michigan proposed another concept known as the Mission to Analyze the UltraViolet universE (MAUVE). This telescope and its sophisticated instruments were conceived during the inaugural NASA Astrophysics Mission Design School. According to the team’s paper, this mission would hypothetically be ready for launch by 2031.

The study was led by Mayura Balakrishnan, a graduate student from the Department of Astronomy at the University of Michigan. She was joined by researchers from the Laboratory for Atmospheric and Space Physics (LASP), the Institute for Gravitation and the Cosmos (IGC), the Center for Cosmology and AstroParticle Physics (CCAPP), the Kavli Institute for Astrophysics and Space Research, the European Space Agency (ESA), the Space Telescope Science Institute (STScI), NASA’s Goddard Space Flight Center, NASA’s Jet Propulsion Laboratory and multiple universities. The paper that details their findings is published in the Publications of the Astronomical Society of the Pacific.

In the past 50 years, ultraviolet observatories have revolutionized our understanding of the universe. However, observations of astrophysical phenomena in the ultraviolet (UV) wavelengths can only be performed at high altitudes or in space due to interference from Earth’s atmosphere—which is very efficient at absorbing UV radiation. As study co-author Dr. Emily Rickman, an ESA astronomer and Science Operations Scientist at the STScI, told Universe Today via email:

“UV astronomy provides us insight into highly energetic events that cannot be captured at other longer wavelengths, like in the visible or infrared wavelength regime, that have a much larger pool of facilities available. Through observing in the UV, our understanding of the universe has made significant advancement through studying star formation, galaxy formation, as well as highly energetic events on planets both within our solar system and in exoplanetary stellar systems.

“Some of the notable areas of this understanding have been in capturing UV radiation from stellar winds emitted from young high-mass stars, which help us piece together how such massive stars formed in the early universe. On the planetary side, UV astronomy has allowed us to observe active aurorae on Jupiter’s poles and how these are influenced by solar storms on the sun. These active aurorae on Jupiter were unexpected and opened up a whole new understanding of planets, their atmospheres, and how they interact within their environment.”

The first UV satellite, the Orbiting Astronomical Observatory 2 (OAO 2) launched in 1968, shortly before the highly anticipated launch of Apollo 8 (the first crewed mission to the moon). Among its many accomplishments, OAO 2 enabled the early characterization of the absorption of electromagnetic radiation by interstellar gas and dust (aka interstellar extinction). This was followed by the Extreme Ultraviolet Explorer (EUVE), which launched in 1992 and conducted the first all-sky survey of far-UV sources.

Then came the Far Ultraviolet Spectroscopic Explorer (FUSE) in 1999, which conducted the first systemic investigations of the intergalactic medium (IGM). Then there was the Galaxy Evolution Explorer (GALEX), which operated from 2003 to 2013 and has conducted the deepest all-sky UV survey to date. There’s also the Ultraviolet and Optical Telescope on the Neil Gehrels Swift Observatory and the three UV instruments on the Hubble Space Telescope—the Space Telescope Imaging Spectrograph (STIS), the Wide Field Camera 3 (WFC3), and the Cosmic Origins Spectrograph.

Unfortunately, none of these detectors can study the cosmos in the far- and extreme-ultraviolet wavelengths with the detail of a PI-led mission. As Rickman noted, this and other factors have limited UV astronomy so far:

“One of the biggest limitations really comes from the dearth of facilities capable of observing within the UV wavelength range. Because UV observatories have the requirement of being in space due to the Earth’s atmosphere blocking out most of the UV radiation, these space-based UV observatories are much more expensive to build and operate than ground-based observatories.

“Due to the limited number of UV observatories, the ones that are currently active, like the Hubble Space Telescope, are over-subscribed by astronomers all over the world, indicating the need and importance for such observatories to exist. In addition, the far extreme UV wavelength is not currently captured with existing instrumentation, providing a blind spot to some astronomical phenomena to be studied.”

While the proposed Habitable World Observatory (HWO) is expected to have advanced UV capabilities, this mission is still in the early stages of planning and is not expected to launch until the 2040s. To this end, the team proposed a UV space telescope concept called the Mission to Analyze the UltraViolet universE (MAUVE), a wide-field spectrometer and imager conceived during the inaugural NASA Astrophysics Mission Design School (AMDS) hosted by the JPL in response to the 2023 Announcement of Opportunity. As Rickman explained:

“The MAUVE mission concept focuses on three main themes within the context of the Astronomy and Astrophysics 2020 Decadal Survey. Those themes are “Are We Alone?/Worlds and Suns in Context,” “How Does the Universe Work?/New Messengers and New Physics,” and “How Did We Get Here?/Cosmic Ecosystem.”

Within the context of answering the question “Are we alone?” MAUVE seeks to study the atmospheric escape of sub-Neptunes, which is hypothesized to be due to either photoevaporation or core-powered mass loss. This will help us understand the habitability of extrasolar systems’ environments, as well as the formation and evolution of exoplanets and their atmospheres.”

“In addition, MAUVE would study the atmospheric composition of hot gas on giant exoplanets and whether they are influenced by equilibrium or disequilibrium condensation, which is vital in order for us to understand exoplanetary atmospheres, giving rise to clues of where life could exist in the universe. For understanding “How does the Universe work?'”

“MAUVE would study whether blue kilonovae are driven by radioactive cooling or rapid shock cooling, which is fundamental in understanding explosive phenomena in the universe, as well as studying whether type 1A supernovae arise from a white dwarf accreting material from a stellar companion, or from merging white dwarfs. And in order to study ‘How did we get here?’ MAUVE would look at if diffuse extragalactic emission results from faint galaxy cluster members and rogue stars, or from shocks of cluster mergers.”

These general themes, said Rickman, are key unanswered questions that astronomers are very interested in addressing as they underpin our understanding of the universe. By extending the wavelength range of existing UV observatories, MAUVE would be able to study the kinds of high-energy cosmological events that could answer some of these questions. In addition, said Rickman, MAUVE would be allocated a substantial amount (70%) of General Observer (GO) time:

“[This would allow] the wider community to propose their observing ideas that could be studied in this largely unexplored parameter space, answering fundamental questions like ‘How do star-forming structures arise and interact with the diffuse interstellar medium?’ ‘What are the most extreme stars and stellar populations?’ ‘How do habitable environments arise and evolve within the context of their planetary systems?’ The possibility to study these questions would provide a fundamental insight into some of the building blocks of our understanding of the universe.”