This animation shows a neutron star—the core of a star that exploded in a massive supernova. This particular neutron star is known as a pulsar because it sends out rotating beams of X-rays that sweep past Earth like lighthouse beacons. (NASA/JPL-Caltech)
NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) mission recently made a remarkable discovery that could lead to a better understanding of how collapsed remnants like black holes can grow and feed on matter at very high rates, something that scientists think had to be done very early in the history of the universe.
The NuStar team, led by Dr. Fiona Harrison from the California Institute for Technology, was studying a supernova that had exploded in a nearby galaxy called Messier 82, or the Cigar Galaxy.
As they were making their observations the scientists also found some other very bright and incredibly luminous x-ray sources – ultraluminous X-ray sources (ULXs) – which they were quite sure were relatively massive black holes eating material at a very high rate.
Upon further investigation the team noticed that one of the objects was pulsing or flashing light. They then realized that it wasn’t a black hole they were observing but a pulsating neutron star (a dead star) called a pulsar.
And what they found wasn’t just any regular pulsar, but the brightest that had ever been seen, pumping out about 10 million times more energy than our sun and more than ten times brighter than any known object like it.
The team’s finding is challenging theorists to try and understand the physics of how this object, nicknamed the “Mighty Mouse” of pulsars, could be so bright.
Harrison, one of the first women to become a principal investigator of a NASA mission, said that this newly discovered object has so much mass packed into it that it’s equivalent to having the mass of the sun jammed into a region the size of the city of San Francisco.
“If you took a teaspoon of the neutron star it would weigh more than all the humans on Earth,” she said.
NuStar, one of NASA’s small ‘explorer missions’ is the first telescope that can offer finely focused images of the universe in the high energy part of the x-ray band (6 – 79 keV). Harrison said that since NuStar can focus so well it produces images that are 100 times crisper than any that had been offered in the high-energy part of the spectrum before.
X-ray electromagnetic radiation is emitted by some of the hottest, densest, most energetic regions in the universe.
Harrison helped create some of the instruments that are aboard the NuStar spacecraft.
One of the first things that Harrison and her colleagues had to do to get the NuStar mission off the ground was to develop x-ray lens that can focus the light as well as new kinds of detectors that work like digital cameras, but can make images in the high-energy x-ray range.
As members of the NuStar mission began their work, they found that the only available types of telescopes that would work in the part of the x-ray spectrum they would be focusing on were those that were based on ‘pinhole cameras’ which she said was a very crude technology.
In order to peer deep into the cosmos, Harrison said that ‘real telescopes’ were needed. So they worked with available x-ray mirror technology and developed and built telescopes that could be used to make observations at higher energies, as well as detectors that could actually stop the powerful beams of electromagnetic radiation to make images.
So as they prepared the NuStar for its June 13, 2012 launch, mission engineers and technicians packed it with instruments that were designed to collect images at energies beyond those of NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton or X-ray Multi-Mirror Mission space telescope.
Although NuStar completed its two-year primary mission, NASA moved the x-ray space telescope onto a two-year mission extension.
NASA officials said they plan continued observations with not only NASA’s NuSTAR, but with its Swift and Chandra spacecraft to see if they can find some kind of an explanation for the behavior of the newly discovered pulsar.
Also, since the discovery of this unique pulsar was a bit of a surprise, members of the NuSTAR team will continue to closely observe other ultraluminous X-ray sources in hopes of finding even more pulsars.
Dr. Fiona Harrison talked about the pulsar discovery, the NuStar mission itself, what it’s like being one of the first female primary investigators of a NASA mission and how she balances her very busy scientific schedule with an active home life as a wife and mother on a recent radio edition of VOA’s Science World.
You can listen to the interview through the audio player below.