Explore the invisible sky with IXPE’s revolutionary X-ray technology

NASAThe IXPE mission entered the General Observer phase in 2024 and focused on inviting global scientific contributions to study X-ray sources.

The science activities for NASA’s IXPE (Imaging Now, during the General Observer phase of the mission, IXPE’s observation program consisted primarily of being led by the broader scientific community.

“We are working to make X-ray polarization a standard part of the toolkit for X-ray astronomers around the world,” said Philip Kaaret, IXPE principal investigator at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “The response within the high-energy astrophysics community has been tremendous.”

Launch of the General Observer program

The General Observer Program, which officially launched in February, invites astrophysicists and space scientists around the world to propose exciting new research into black holes, neutron stars, active galactic nuclei and other high-energy X-ray sources using the IXPE telescope.

In the spacecraft’s first two years of operation, NASA’s research partners included more than 175 scientists in 13 countries – and interest continues to grow. Proposed studies submitted to the General Observer Program to date involve more than 1,400 researchers at 174 unique institutions in 30 countries.

“Our primary goal is to enable any interested party to use, analyze and interpret IXPE data,” said Kavitha Arur, program leader at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We want to maximize scientific results and cover the widest possible range of objectives.”

In June 2023, NASA extended an open invitation to researchers to propose new IXPE missions and observation targets. By the October 2023 deadline, the General Observer Program team had received 135 proposals for Cycle 1, which covered the first year of the program. Each proposal was extensively peer-reviewed by NASA astrophysicists and associated experts in the field.

Researchers proposed studies based on the number of seconds of IXPE target observation they estimated would be needed to obtain the data needed to verify a hypothesis or model.

For cycle 1, the team selected 39 proposals, accounting for a total observation time of approximately 15 million seconds. That figure includes some overlap between the selected targets – and the selected targets include a few surprises.

“Some of the selected proposals addressed types of targets that we had not considered before, such as tidal disruptions,” Kaaret said. A tidal disruption occurs when a star is pulled into a supermassive black hole and torn.

New research and objectives

Cycle 1 researchers will also use IXPE for the first time to a white dwarf, a remnant of the star’s core that is about the size of Earth, but with a mass comparable to that of our Sun. That white dwarf is part of the binary system T Coronae Borealis, about 3,000 light-years away from our solar system. ‘T CrB’, as it is known to astronomers, also includes an ancient red giant that emits a nova outburst about every 80 years. The nova was last seen in 1946 and astronomers expect another outburst between now and September 2024. To stargazers on Earth, this nova will appear to be a star that wasn’t there before.

That wide time frame makes T CrB a “target of opportunity” for IXPE – an unpredictable wrinkle in the carefully plotted Cycle 1 schedule. Such an event requires a quick response from the team so that IXPE can reference it without much advanced planning.

Challenges in planning observations

Allyn Tennant, head of IXPE’s scientific operations center in Marshall, is tasked with charting IXPE’s timeline. It takes into account the precise duration of each observation, the time required to download the findings and the necessary repositioning time between targets.

What does it take to execute such a complex plan? “A certain amount of thinking, a certain amount of swearing and a lot of replanning,” Tennant said.

“We started the program the first week of February and by the end of April, Allyn had already rescheduled the plan seven times,” Kaaret added. “It makes for some stressful weekends, but there are a lot of really exciting results coming out of these unexpected events.”

IXPE spends about a week on each goal on average, so it’s not difficult to plan about 40 goals in a 52-week period, Tennant said — until one encounters those opportunities. There is also the challenge of managing the inflow of data from each observation. The brighter the target, the greater the volume of incoming data that must be captured, verified, and distributed to investigators.

Collaborative efforts and future prospects

The spacecraft’s busy schedule also includes joint astronomical observations with other NASA instruments conducting their own science missions in orbit. These joint efforts further enhance the value of the data collected during IXPE’s General Observer Program surveys, but add an additional level of complexity when opportunity targets require schedule realignment.

During Cycle 1 and Cycle 2, IXPE will collaborate with NASA’s X-ray observatory NICER (Neutron Star Interior Composition Explorer), which studies neutron stars, black holes and other phenomena from its permanent vantage point aboard the spacecraft. International Space Station. In Cycle 2, beginning in February 2025, the program will also work with NASA’s orbiting Swift and NuSTAR (Nuclear Spectroscopic Telescope Array) imaging sensors, which monitor gamma-ray bursts and high-energy cosmic X-ray events, respectively.

Growing interest in the success of IXPE led USRA’s Science and Technology Institute to announce the first IXPO (International X-ray Polarimetry Symposium), to be held in Huntsville from September 16 to 19. Astronomers, engineers and X-ray technologists are encouraged to attend.

View the full list of selected IXPE Cycle 1 research proposals. Read more about program guidelines for submitting Cycle 2 proposals.

IXPE, led by NASA Marshall, is a collaboration between NASA and the Italian Space Agency. The Space & Mission Systems division of BAE Systems Inc., in Broomfield, Colorado, manages spacecraft operations jointly with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.