NASA is gearing up to launch a new set of X-ray eyes on the cosmos. The first space observatory of its kind, the Imaging X-ray Polarimetry Explorer, or IXPE, is built to study some of the most energetic objects in the universe – the remnants of exploded stars, powerful particle jets spewing from feeding black holes, and much more.
IXPE won’t be as big and strong as the Chandra X-ray
Observatory, NASA’s flagship X-ray telescope. But
what IXPE lacks in imaging power, it makes up by seeing an aspect of cosmic
X-ray sources that has gone largely unexplored until now – polarization.
“The launch of IXPE marks a bold and unique step
forward for X-ray astronomy,” said Dr. Martin Weisskopf, IXPE’s principal
investigator. “IXPE will tell us more about the precise nature of cosmic X-ray
sources than we can learn by studying their brightness and color spectrum
alone.”
The Imaging X-ray
Polarimetry Explorer mission is set to launch Dec. 9 on a Falcon 9 rocket from
NASA’s Kennedy Space Center in Florida. In space, IXPE will explore the
leftovers of exploded stars, black holes, and more by looking at a special
property of light called polarization. Credits: NASA
An X-ray Polarization Primer
X-rays are a form of high-energy light. They originate from places where
matter is under extreme conditions – violent collisions, enormous explosions,
10-million-degree temperatures, fast rotations, and strong magnetic fields.
They carry detailed information about the powerful phenomena that produce them.
But Earth’s atmosphere blocks cosmic X-rays from reaching the ground, so they
can only be collected by telescopes in space.
Polarized light carries unique details about where the light comes from and
what it passes through. Light is made up of interconnected waves of electric
and magnetic fields that interact with each other in a way that makes them
oscillate, or vibrate, at right angles to the path the light is traveling. The
vibrations can be up-and-down, side-to-side, or anywhere between. Polarized
light is made up of electric fields that vibrate in just one direction.
Light from a typical bulb, for example, produces electric fields that
vibrate every which way. If the light is scattered or reflected by particles or
surfaces, the light can become polarized – with vibrations aligned in just one
direction.
Seeking Answers to Fundamental Questions
By analyzing polarized X-rays with IXPE, scientists can learn more about
the structure and behavior of celestial objects, their surrounding
environments, and the physics of how X-rays come to be.
IXPE’s polarization measurements will also hold clues to questions
astronomers have wondered about for decades, such as:
- What is the spin of a black hole?
- What powers the mysterious brightness of pulsars – spinning dead stars
so dense that a spoonful would weigh as much as a mountain on Earth?
- Does our understanding of the fundamental laws of physics hold up
throughout the whole universe?
“IXPE will help us test and refine our theories of how the universe works,”
Weisskopf said. “There may be even more exciting answers ahead than the ones
we’ve hypothesized. Better yet, we may find whole lists of new questions to
ask!”
For Weisskopf, who is also the project scientist for Chandra, adding
polarization to the X-ray mix has long been a goal. Making such measurements is
difficult. It requires sensitive instruments, a rocket ride into space, and
long observing times.
IXPE’s powerful new X-ray vision is made possible by state-of-the-art
polarization detectors developed in Italy. IXPE carries three identical
telescopes. Each has a set of nested, cylinder-shaped mirrors that collect
X-rays and feed them to a detector, which takes a picture of incoming X-rays
and measures both the amount and direction of polarization.
“This is going to be groundbreaking in terms of X-ray data acquisition,”
Weisskopf said. “We’ll be analyzing the results for decades to come.”
IXPE is set to launch Dec. 9 on a Falcon 9 rocket from NASA’s Kennedy Space
Center in Florida. IXPE is a partnership between NASA and the Italian Space
Agency. Ball Aerospace is the main industry partner.
Written by Rick Smith, NASA’s Marshall Space Flight Center
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