Science mission begins for NASA’s new X-ray eye on the universe – Spaceflight Now

Artist’s concept of imaging X-ray polarimetry explorer. Credit: NASA

A NASA astronomy satellite launched Dec. 9 from Kennedy Space Center on a SpaceX rocket has begun X-ray observing the universe, embarking on a mission to study the nature of black holes and the super-dense skeletons left behind by exploded stars.

The Imaging X-ray Polarimetry Explorer, or IXPE, mission launched Dec. 9 aboard a SpaceX Falcon 9 rocket, which delivered the satellite into a single equatorial orbit at an altitude of about 373 miles (600 kilometers). .

After separating from the Falcon 9 launch vehicle, the 727-pound (330-kilogram) IXPE spacecraft deployed its solar panels and went through a series of tests. On Dec. 15, less than a week after launch, IXPE extended an origami-shaped boom containing the satellite’s three X-ray telescopes, giving the satellite a length of about 17 feet (5.2 meters) from end to end.

The extendable boom is the right length to allow the telescopes’ mirrors to focus X-ray light onto detectors inside the spacecraft’s main body, giving the IXPE satellite the ability to record the high-energy waves emitted by black holes, neutron stars and invisible X-ray sources for telescopes tuned to observe in other wavelengths.

“Commissioning has been completed,” said Martin Weisskopf, IXPE principal investigator at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “The two most nerve-wracking elements of commissioning were deploying the solar panels and deploying the boom.”

After the boom extension was completed, ground crews spent about three weeks checking the observatory’s maneuvering and pointing capabilities and aligning the telescopes, according to NASA.

“All spacecraft functions were activated and checked during commissioning,” Weisskopf said during a Jan. 10 press briefing at a meeting of the American Astronomical Society.

This image from NASA’s Chandra X-ray Observatory shows Cassiopeia A, the remains of a star that exploded in a violent supernova about 350 years ago. NASA’s IXPE mission observes Cassiopeia A as the first scientific target. Credit: NASA/CXC/SAO

IXPE is one of many X-ray astronomy missions in NASA’s portfolio, but it is the first to be tuned to measure the polarization signal of X-ray light. Previous telescopes, which must in l space detect cosmic X-rays, imaged X-ray sources in high angular resolution, measured their spectroscopy, or chemical fingerprints, and studied the temporal variation of X-ray signals.

“By doing this mission, we are adding two variables to the astrophysics toolbox to understand these sources,” Weisskopf said before the IXPE launch. “It’s the degree of polarization and the direction associated with the polarization.”

The polarization of X-ray light is a measure of the direction of its electromagnetic field, a telltale signal that can tell astrophysicists about the extreme environments around black holes and supermassive objects, including the supermassive black hole at the center of the galaxy. of the Milky Way.

Weisskopf said Jan. 10 that IXPE’s detectors, which are the first designed to measure X-ray polarization from space, observed light calibration sources with known properties to help ground crews refine the alignment of mission telescopes.

IXPE’s three identical telescopes can measure the energy, position, time of arrival and polarization of each X-ray photon they collect.

Satisfied that the IXPE mission was ready for its science campaign, NASA officials gave the go-ahead for the spacecraft to begin the first of its regular astronomical observations on January 11.

IXPE’s first target is called Cassiopeia A, or Cas A, a giant debris cloud surrounding a super-dense neutron star about 11,000 light-years away. Cassiopeia A was formed around 350 years ago, when a star estimated to be five times more massive than the Sun exploded in a violent supernova.

The explosion sent material from the star’s interior out into space in all directions at nearly the speed of light, leaving behind the star’s collapsed core, a neutron star. IXPE observations will provide insight into the magnetic field surrounding the neutron star.

The observatory will observe Cassiopeia A for about three weeks. It is the first of 33 planned science targets selected for the first year of the IXPE mission, Weisskopf said.

Nine Merlin main engines propel SpaceX’s Falcon 9 rocket from pad 39A on December 9 with NASA’s IXPE mission. Credit: Michael Cain / Spaceflight Now / Coldlife Photography

Mission planners have also set aside observing time for the IXPE to turn its telescopes toward “targets of opportunity,” such as features or objects that suddenly light up in the sky, Weisskopf said. “So if anything interesting comes up, we can go watch it.”

The flight plan has time to observe approximately 40 targets in total during IXPE’s first year of operation. IXPE will aim its telescopes at each target for days or weeks at a time, collecting long X-ray exposures to allow scientists to sort out polarized signals from the background noise.

NASA is funding IXPE for a two-year core mission, which the agency says is worth $214 million, including development, launch and operations. The spacecraft does not need rocket fuel for pointing or orbiting maneuvers.

IXPE is a partnership between NASA and the Italian Space Agency, which provided the mission’s X-ray detectors and a ground station in Kenya to receive science data from the satellite as it flies overhead.

According to Weisskopf, the polarization of X-rays can tell scientists about the spin of a black hole. Theoretical calculations show that the degree of polarization of an X-ray signal varies with the energy of the magnetic field at its source.

“Black holes don’t have many properties, but one of them is spin,” he said. “So this is a very fascinating use of polarimetry to determine something about the nature of its source, and this story is true in many other cases.”

Other targets for IXPE include the supermassive black hole at the center of our galaxy, known as Sagittarius A*. IXPE measurements can confirm whether the black hole was much brighter a few hundred years ago, as some scientists believe.

IXPE will also examine more distant targets, such as blazers at the center of other galaxies. Blazars have powerful beams of radiation that happen to be aimed directly at Earth.

The mission will also study the polarization of X-rays from magnetars, which have the strongest magnetic fields of any star, some trillion times stronger than Earth’s magnetic field.

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