Early in the morning of December 9, 2021, SpaceX launched the Imaging X-ray Polarimetry Explorer (IXPE) on a Falcon 9 rocket booster that had already flown four times before. The instrument will observe black holes and neutron stars.
The IXPE is about the size of a refrigerator and cost $214 million to manufacture. It includes three telescopes capable of measuring the polarization of light. Polarization is a measure of how much light oscillates compared to its direction is travel.
Scientists can use these measurements to study the structure and inner workings of some of the most dramatic objects in the universe, such as black holes or neutron stars.
According to IXPE principal investigator Martin Weisskopf, “What polarization tells us depends on the source. Black holes, for instance, don’t have a lot of properties but you can measure the spin by looking at the variation in the polarimetry of X-rays emanating from these sources.”
Existing orbital telescopes capable of making observations in the X-ray spectrum include the Chandra Space Telescope, which is capable of taking X-ray images of distant objects. IXPE is the first to be solely dedicated to measuring the polarization of X-rays.
The IXPE’s first target is the Crab Nebula, also known as Messier 1, which resides in the constellation Taurus. In the year 1054, Chinese astronomers reported the “guest star,” a supernova that created the nebula now known as the Crab Nebula and was visible from Earth for nearly a month.
The Crab Nebula is an especially attractive target for IXPE because the remains of the star became a rapidly spinning neutron star that emits beams of X-rays like a rotating lighthouse at a rate of 30 pulses per second.
This most recent launch marks the 28th launch of 2021 for SpaceX. NASA selected the legendary Pad 39A for the launch for its exceptional water suppression system, which could mitigate potential damage to the IXPE during launch.
Now that the IXPE is launched, it will maneuver into a nearly equatorial orbit with an inclination of 0.2 degrees. It will have a low enough orbit to provide it with some protection against radiation and communicate more reliably with ground stations.
The booster previously launched astronauts for the Crew-1 and Crew-2 missions to the International Space Station. It also launched a Cargo Dragon that sent supplies and scientific experiments to the space station in August and a radio satellite for SiriusXM.
SpaceX’s reusable rockets and spacecraft are an attractive option for saving money when launching cargo and people into space. NASA only pays $55 million per seat on the Crew Dragon, compared to $86 million per seat on the Russian Soyuz. Due to the cost savings and delays suffered by competing privately owned crew spacecraft, NASA recently expanded its Commercial Crew contract with SpaceX for three additional flights to the International Space Station.
SpaceX also has contracts to develop a Starship-derived lunar lander for NASA’s Artemis program and launch components for the Lunar Gateway. Remaining SpaceX launches for this year include a communications satellite for Turkey on December 18 and an International Space Station resupply mission on December 21.