Often referred to as Cosmic Lighthouses, neutron stars (also known as pulsars) are incredibly dense stars that shoot out X-rays at a predictable rate, like a lighthouse.
Read more on them here: NEW NASA MISSION TO PROBE CELESTIAL LIGHTHOUSES
A new NASA mission proposes to examine the nature of these neutron stars as well as how accurately we can use these beacons as celestial guiding points for deep space missions.
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 when the hotspots comes within view, then dims as the hotspots turn away.
(There are a) 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.
On May 6, 2014 a new article on an ultra-precise pulsar was published by Janet Fang
NEW NASA MISSION TO PROBE CELESTIAL LIGHTHOUSES
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.”
COSMIC LIGHTHOUSES WILL GUIDE SPACESHIPS THROUGH THE GALAXY
There are several different types of pulsars, but the ones best suited for the job are milli-second pulsars, which have extremely rapid rotation rates. “We concentrated on the milli-second pulsars for the purpose that they have the shortest periods which allows you to probe the distance with the highest accuracy,” explained Becker.
Knowing the exact time at which to expect a beam from a pulsar to arrive at Earth, and then comparing this to the time that the beam swept past a distant spacecraft, allows the location of the craft to be determined. Becker explained how the time difference in pulses can be extrapolated to find differences in distances.
“When we compare the pulse arrival time, we know where it should have been and where we measured it, and the difference in arrival time can be used (if multiplied by the velocity [of the spacecraft] and period of the pulsar) to compute the distance from the position you assumed you were during the measurement and where you were actually during the measurement. Then you correct your position according to your measurement and you do a new measurement. So it’s a kind of iterative process.”
The pulses as measured from Earth would also need to be corrected to the Solar System barycentre, i.e. the centre of mass of the Solar System, to take into account the different locations of radio telescopes.
As well as interstellar space, pulsar navigation could also be used for space exploration in the Solar System to provide back-up to Earth based systems. “The next step is going to Mars, and then you may ask the question do you really want to rely on being tracked only from Earth,” said Becker. If communications failed between Earth and a spacecraft en route to Mars, then the astronauts would be forced to navigate using the constellations. However, using this new system they would be able to navigate independent of radio communications with Earth.
Timing the signals from pulsars can also have applications much closer to home, as it can be used to assist current GPS satellites and the upcoming Galileo satellite navigation system, and Becker explained the advantages to this.
“These satellites are also controlled from Earth, and if you don’t control and correct the orbits of the GPS satellites for longer than 72 hours the signals get completely unreliable. It needs a control from the Earth, but if you have a satellite using this pulsar method and technology, you could use this to augment the GPS satellites or the Galileo satellites and they would refer to this external satellite doing the navigation. It would mean that you would not have any requirement to control the satellites any more from Earth; it would make it really autonomous.”
Astronomers have been collecting data on pulsars for decades, so some milli-second pulsars have already been timed to high precision. The next step for the pulsar navigation method is to design the technology that will allow it to be used aboard a spacecraft, and simulations are already being implemented to discover the best way to do this.
tem will use specially developed algorithms to stitch together an on-board navigation solution.”
photo credit: The densely packed matter of a pulsar spins at incredible speeds, and emits radio waves that can be observed from Earth, but how neutron stars emit these waves is still a mystery / Swinburne Astronomy Productions/CAASTRO