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New NASA mission to probe celestial lighthouses

Elizabeth Howell, News Writer
Apr 9, 2013, 7:00 UTC

Sen—Spinning in space are incredibly dense stars that shoot out X-rays at a predictable rate, like a lighthouse. A new NASA mission proposes to examine the nature of these neutron stars - also known as 'pulsars' - as well as how accurately we can use these beacons as celestial guiding points for deep space missions.

Called NICER (Neutron Star Interior Composition Explorer) the mission will use X-rays to look at emissions from these strange stars. The instrument will launch in 2017. It will be mounted on the International Space Station for observations from low Earth orbit.

Neutron stars are thought to form after the collapse of a massive star that is between 8 and 30 times the size of the sun, according to the University of Maryland's Coleman Miller, an astronomy researcher. After the supernova blows off most of its mass, what is left behind is a small core about the size of New York City, at 20 kilometres (12 miles) across. 

In this small space, the protons and electrons that make up matter are "literally scrunched together", stated NASA. One sugar-cube-sized bit of neutron star has a mass of a billion tons, the equivalent of Mount Everest's weight, the agency added.

Zaven Arzoumanian of NASA's Goddard Space Flight Center, is deputy principal investigator for NICER. He told Sen: "Everything in our world is made of atoms consisting of protons and neutrons making up the nucleus plus electrons in orbit around it. But they are mainly empty space.

"If you squeezed some gold, uranium or lead so hard that you eliminated all the empty space, you'd have something just like a neutron star. We want to understand how stuff behaves at such incredibly high densities."

NICER is one of NASA's astrophysics explorer-class missions that aim to examine the universe at low cost. This will cap NICER's mission costs at just US$55 million (£39.2 million). Simulataneously with NICER's announcement, the agency also said it will fund the Transiting Exoplanet Survey Satellite for US$200 million (£130.7 million).

The NICER instrument will include 56 small X-ray telescopes packed into a mini fridge-sized package. It will probably arrive at station in a Dragon cargo spacecraft manufactured and operated by SpaceX.

Once ready, the telescope array will examine X-rays that come from "hotspots" on the star's surface, as well as its magnetic field, NASA stated. Pulsars spin at a dizzying rate of anywhere from seconds to milliseconds. As they whip around in their rotation, the hotspots flash periodically within sight of Earth. X-ray brightness from the pulsar increases whn the hotspots comes within view, then dims as the hotspots turn away.

NICER will focus on the millisecond class of pulsars that spin as rapidly as 700 times a second. These pulsars have such a consistent rotation rate that they are considered accurate celestial clocks. In space, they could be used in a similar way to global positioning satellites that provide navigation data to the military and civilians, particularly in vehicles.

"To demonstrate the navigation technology’s viability, the NICER ... payload will use its telescopes to detect X-ray photons within these powerful beams of light to estimate the arrival times of their pulses," NASA stated.

"With these measurements, the system will use specially developed algorithms to stitch together an on-board navigation solution."