By Timothy Kelly
1.5-million light year-wide jets of very high-energy plasma, subatomic particles and magnetic fields shooting from the supermassive black hole in galaxy Hercules A, shown in optical, x-ray (purple) and radio (blue). Photo: X-ray: NASA/CXC/SAO, Optical: NASA/STScI, Radio: NSF/NRAO/VLA).
On Aug. 18, NASA announced that a proposed space mission called STAR-X had been selected for further study. The study team has been awarded $3 million to further their work and one of Penn State’s own is on that team: Niel Brandt, the Verne M. Willaman Professor of Astronomy and Astrophysics. Now the team has nine months “to prove to NASA that we can actually execute this mission as planned,” according to Brandt.
“One of the ways this mission is fundamentally different than many previous x-ray missions,” said Brandt, “is that … it has been optimized … to [provide] a good imaging quality on average across a large field of view.”
The purpose of the mission is to make observations of extreme events in the universe that generate high-energy electromagnetic signals like x-rays and ultraviolet light.
In addition, “… [this mission] will repeatedly observe particular areas of sky that we already have studied… in other wavelengths. And we will conduct much better x-ray observations over those areas of sky,” said Brandt.
As Brandt noted, “This is something that has been a many-year endeavor … We have proposed this mission previously… and did not win.” Still, NASA originally recognized that STAR-X was a good concept despite some weaknesses.
Brandt said, “People worked for many additional years and we addressed all those weak points.” Each of the institutions involved, including Penn State, put in decades of extra research to build capabilities in specific disciplines to make a successful mission. They then resubmitted their proposal in December 2021 and it was accepted.
Why Penn State? This research is being done at Penn State for two reasons: experience and connections. Brandt said, “My main job for the past 25 years has been the analysis and interpretation of data from x-ray satellite missions.” Brandt has been a PI for the Chandra X-ray Observatory. He has worked with at least two of the STAR-X team members since 2000. That includes Ann Hornschemeier, the deputy PI of the STAR-X mission and lab chief for X-ray Astrophysics at Goddard. Hornschemeier earned a PhD in astronomy and astrophysics at Penn State, mentored by Brandt, in 2002.
“One of the ways this mission is fundamentally different than many previous x-ray missions,” said Brandt, “is that … it has been optimized … to [provide] a good imaging quality on average across a large field of view.” The STAR-X telescope will collect much larger samples of x-ray and UV sources across the universe and those samples will allow scientists to statistically characterize their sources, giving them a greater ability to test scientific hypotheses.
One area of research STAR-X intends to focus in on? The supermassive black holes at the center of many galaxies, also called active galactic nuclei.
Brandt said, “How can you learn about how black holes grow? Well, you have to observe the actual accretion process ... STAR-X, by catching examples of extreme accretion … can help us to understand how black holes have grown … and how these very massive black holes early in the history of the universe came to exist.”
The STAR-X space mission will result in a large volume of data becoming available to Penn State astronomers and astrophysicists. The mission has a “broad enough scope that many other people in the [astronomy and astrophysics] department could use the data from this mission for their own purposes,” said Brandt. Brandt also said if the mission is approved, he may be hiring people to analyze and interpret the data.
Now the team has nine months “to prove to NASA that we can actually execute this mission as planned,” according to Brandt.
STAR-X is a NASA Explorer mission. According to the NASA press release announcing the concept studies, “NASA Explorer missions conduct focused scientific investigations and develop instruments that fill scientific gaps between the agency’s larger space science missions.” If past and present involvement with NASA is any indication, Penn State will be contributing to these investigations for years to come.