image: Renderings of AXIS (left) and PRIMA.
Credit: Images courtesy of Christopher Reynolds and Alberto Bolatto. Composite by Mark Sherwood.
On October 3, 2024, NASA announced that two space probes proposed by University of Maryland astronomers have advanced to the next round of consideration for a $1 billion mission slated to launch into orbit in 2032.
The selected probes include the Advanced X-ray Imaging Satellite (AXIS) mission with UMD Astronomy Professor Christopher Reynolds as its principal investigator and the PRobe far-Infrared Mission for Astrophysics (PRIMA) with UMD Astronomy Professor Alberto Bolatto as a co-investigator and NASA Goddard Space Flight Center researcher and UMD Astronomy Adjunct Professor Jason Glenn as its principal investigator.
“It's a huge achievement for three of our astronomy faculty members to be leading the charge on missions that will explore the cosmos in an entirely new way,” said Amitabh Varshney, dean of the College of Computer, Mathematical, and Natural Sciences.
"This is terrific news—Chris, Alberto and Jason are true leaders in their fields,” added Andrew Harris, chair of UMD’s Department of Astronomy. “They, along with colleagues at NASA Goddard and other institutions, have made the scientific cases that drive these exciting missions forward to the next stages possible."
This announcement follows NASA’s creation of a new class of astrophysics observatories, called probes, which are smaller than “flagship” missions like the James Webb Space Telescope but still capable of tackling the big questions in astrophysics. NASA plans to select either a far-infrared or X-ray observatory to investigate the birth of planets, as well as the evolution of galaxies and black holes, in the early universe.
Over the next year, each team will receive $5 million to flesh out their plans and prototypes for AXIS and PRIMA even further. NASA will then re-review the proposals and select one mission to move forward in 2026.
Read more below about the proposed missions and what the UMD astronomers behind them hope to discover.
AXIS
AXIS will be able to peer “further and wider” into the early cosmos than previous X-ray observatories, according to Reynolds.
Thanks to new technologies that have been developed at NASA Goddard over the last few years, AXIS would be 10 times more sensitive to X-rays than the Chandra X-ray Observatory was at its launch in 1999. The biggest innovation was the development of X-ray mirrors large enough to collect numerous X-rays but sensitive enough to capture extremely high-quality images—a tricky balancing act that can yield vital planetary information.
X-rays come from extremely hot processes such as the explosion of stars or the accretion of black holes, so tracing them back to their source can paint a picture of galactic formation. As scientists search for life beyond Earth, X-rays could even offer clues about potentially habitable planets.
In extreme cases, stars with intense flares and coronal mass ejections could strip surrounding planets of their atmospheres, making those places uninhabitable. On the opposite end of the spectrum, using X-rays to find “quieter” and less active stars could help researchers find nearby planets that are potentially habitable.
“Because AXIS is so sensitive, it can detect quite easily the X-rays from other stars and categorize how active they are, how powerful their flares are and how powerful their corona is,” Reynolds said. “Then, it can start to connect that to the properties of any planets that might exist around it.”
Reynolds, who is also the director of the Joint Space-Science Institute, a research partnership between UMD and NASA Goddard, said another goal of AXIS is especially relevant to his research: observing some of the earliest black holes in the universe.
“The AXIS observatory is designed to be able to detect X-rays from the first supermassive black holes in the first 500 million years of the universe,” Reynolds said. “Some scenarios predict that we should see lots of black holes in that era, and others say that we shouldn’t. It's very much an unanswered question of when those first supermassive black holes emerged and what were their progenitors.”
Reynolds also hopes to study how central black holes, which sit in the middle of galaxies, influence the formation of stars and other celestial objects around them. While Webb has already made significant strides in black hole research, Reynolds explained that AXIS could complement or even expand on its findings.
“We have a much wider field of view than James Webb, so the patch of sky we're looking at is much larger. That means that we can survey the sky in a more efficient and faster way,” Reynolds said. “We are looking forward to the next generation of X-ray astronomy.”
PRIMA
PRIMA has similar goals to AXIS—including exploring the formation of black holes and stars—but it would see the early universe a lot differently. PRIMA is designed to pick up on far-infrared radiation, which, according to Bolatto, is an “underserved” wavelength in astronomy missions.
The Herschel Space Observatory, which was operational from 2009 to 2013, was the last space observatory capable of detecting these longer wavelengths. Bolatto said that one advantage of a far-infrared observatory is its ability to “cut through the muck” of cosmic dust and gas in a way that past and present telescopes, including Webb, could not do as efficiently. This would allow PRIMA to simultaneously study the growth of black holes and their host galaxies when they are heavily obscured, which is a common experience in the early universe.
While astronomers ultimately want to peer past space dust to see other objects, PRIMA researchers will also pause to analyze the odd amalgamation of rock, minerals and other materials in their path.
“We don't know how dust happens,” Bolatto said. “We sometimes measure very large quantities of dust in the very early history of the universe, but it’s not clear where it comes from. So understanding how that process happens is part of what we’re trying to achieve.”
With PRIMA, researchers also want to look back to a time before the planets formed. They plan to analyze protoplanetary disks—collections of gas and dust orbiting young stars that are the birthplace of planets—to determine how much water is needed for different types of planets to form. Doing so could even uncover where Earth’s water came from, a mystery that has not been definitively solved.
“We can see protoplanetary disks now, but measuring how massive they are is incredibly difficult with radio astronomy or with near-infrared probes,” Bolatto said. “With PRIMA, we will be able to measure the mass of protoplanetary disks directly in a much better way than anybody has been able to do up till now.”
Bolatto noted that PRIMA’s cutting-edge technologies should enable plenty of new discoveries. Like Webb, PRIMA’s telescope would be cryogenically cooled to reduce infrared background noise, but it will reach even colder temperatures—about 4.5 K, or -450 degrees Fahrenheit—to improve the instrument’s sensitivity.
PRIMA would also be outfitted with a wide-field camera, a high-resolution spectrograph to study the chemical composition of cosmic objects not seen before and state-of-the-art kinetic inductance detectors developed by NASA’s Jet Propulsion Laboratory in collaboration with Goddard to measure far-infrared radiation. Goddard would also equip PRIMA with a high-resolution spectrometer, enabling scientists to detect water in protoplanetary disks as well as galactic winds caused by supermassive black holes.
Glenn said that he and his colleagues are excited to see what comes next for PRIMA.
“The PRIMA team is excited and grateful for this opportunity to develop a concept for the first NASA Astrophysics Probe Explorer,” Glenn said. “Our extraordinary team of scientists and engineers is going to enable humankind to understand how black holes and galaxies evolved together and how planets got their atmospheres."
Bolatto added that PRIMA could be a gamechanger for astrophysics if it’s ultimately selected to become the next probe mission.
“The excitement is that we are going to get to see a completely new sky because there are things that we couldn't dream of doing 10 years ago that we will be able to do with the technology we have now,” Bolatto said. “The amount of science that can come out of PRIMA would be fantastic.”