Sunday, November 26, 2017

Measuring neutron star sizes by using thermonuclear explosion models

Neutron stars are made out of cold ultra-dense matter. How this matter behaves is one of the biggest mysteries in modern nuclear physics. Researchers developed a new method for measuring the radius of neutron stars which helps them to understand what happens to the matter inside the star under extreme pressure. A new method for measuring neutron star size was developed in a study led by a high-energy astrophysics research group at the University of Turku, Finland. The method relies on modelling how thermonuclear explosions taking place in the uppermost layers of the star emit X-rays to us. By comparing the observed X-ray radiation from neutron stars to the state-of-the-art theoretical radiation models, researchers were able to put constraints on the size of the emitting source. This new analysis suggests that the neutron star radius should be about 12.4 kilometers. "Previous measurements have shown that the radius of a neutron star is circa 10-16 kilometres. We constrained it to be around 12 kilometres with about 400 meters accuracy, or maybe 1000 meters if one wants to be really sure. Therefore, the new measurement is a clear improvement compared to that before, says Doctoral Candidate Joonas Nattila from the University of Turku who developed the method.

The new measurements help researchers to study what kind of nuclear-physical conditions exist inside extremely dense neutron stars. Researchers are particularly interested in determining equation of state of the neutron matter, which shows how compressible the matter is at extremely high densities.

"The density of neutron star matter is circa 100 million tons per cubic centimetre. At the moment, neutron stars are the only objects appearing in nature, with which these types of extreme states of matter can be studied," says Juri Poutanen, the leader of the research group.

The new results also help to understand the recently discovered gravitational waves that originated from the collision of two neutron stars. That is why the LIGO/VIRGO consortium that discovered these waves was quick to compare their recent observations with the new constraints obtained by the Finnish researchers.

"The specific shape of the gravitational wave signal is highly dependent on the radii and the equation of state of the neutron stars. It is very exciting how these two completely different measurements tell the same story about the composition of neutron stars. The next natural step is to combine these two results. We have already been having active discussions with our colleagues on how to do this," says Nattila.

Aerojet Rocketdyne Supports ULA Delta II Launch of Joint Polar Satellite System-1

Aerojet Rocketdyne, Inc., a subsidiary of Aerojet Rocketdyne Holdings, Inc. (NYSE:AJRD), helped propel the United Launch Alliance Delta II rocket, carrying the Ball Aerospace-built JPSS-1 satellite, the first of the new JPSS (Joint Polar Satellite System) constellation, into orbit for the National Oceanic and Atmospheric Administration (NOAA) and NASA. The mission will provide sophisticated meteorological data and observations of atmosphere, ocean and land to help NOAA's National Weather Service improve the 3 to 7 day weather forecasts aiding emergency personnel in pre-storm preparation. JPSS-1 launched from Vandenberg Air Force Base in California. Aerojet Rocketdyne propulsion included an RS-27A engine system and an AJ10-118K upper-stage engine. "The RS-27A and AJ10-118K engines continue Aerojet Rocketdyne's strong legacy of placing critical satellites into orbit with 100 percent mission success," said Aerojet Rocketdyne CEO and President Eileen Drake. "It's an honor to know we are helping to support climate research, weather and storm prediction for civil, military and international partners. Congratulations to everyone involved."

The RS-27A and AJ10-118K engines have helped place payloads into space aboard the Delta II launch vehicle for the U.S. Air Force, NASA and commercial spacecraft missions, including the Phoenix Mars Lander, Deep Impact, Kepler, NEAR Shoemaker and the Mars Exploration Rovers, Spirit and Opportunity, as well as the U.S. Air Force Global Positioning Block IIR fleet.

Aerojet Rocketdyne's role in the launch began during liftoff when the RS-27A engine ignited to provide 237,000 pounds of vacuum-level thrust to launch the Delta II rocket. The RS-27 family of engines has compiled one of the most consistent and successful launch records in the history of rocketry, with 240 launches since 1974.

After separation of the first stage, the AJ10-118K upper-stage engine ignited to place the payload into orbit, providing approximately 10,000 pounds of vacuum thrust for orbital insertion. The AJ10 family of engines has provided second-stage propulsion for more than 270 Delta flights, with 100 percent mission success.

The RS-27A and AJ10-118K engines have helped place payloads into space aboard the Delta II launch vehicle for the U.S. Air Force, NASA and commercial spacecraft missions, including the Phoenix Mars Lander, Deep Impact, Kepler, NEAR Shoemaker and the Mars Exploration Rovers, Spirit and Opportunity, as well as the U.S. Air Force Global Positioning Block IIR fleet.

The JPSS next-generation polar-orbiting, non-geosynchronous satellites will circle the Earth from pole-to pole and cross the equator about 14 times per day, providing full global coverage twice a day, according to NOAA. It is a collaborative program between NOAA and NASA.

The JPSS constellation will carry a suite of sensors designed to collect measurements of atmospheric, terrestrial and ocean conditions, including clouds, rainfall, snow and ice cover, vegetation, fire location, water vapor and ozone, as well as sea and land surface temperatures.

Tuesday, November 7, 2017

The Most Powerful Magnets in the Universe Are Collapsed Stars

When a large star dies, sometimes it becomes a neutron star, a tiny, 12 mile across ball that's made almost entirely out of neutrons. These dead stars are incredibly dense, and spin incredibly fast. Just one thimbleful of neutron star would weigh 100 million tons. Magnetars are a variation of neutron stars, and they somehow manage to be even scarier. Neutron stars already have extremely strong magnetic fields--about 2 trillion times more powerful than Earth's. Yet magnetars have magnetic fields 1,000 times stronger than that. Yeah, that's a pretty intense field. Magnetars are not just insanely powerful--they're also very, very dangerous. If you were a mere 1,000 kilometers from a magnetar, your entire body would dissolve as the magnetic field rearranged the sequence of atoms in your body. 

In addition to their terrifying magnetic powers, magnetars also have something called starquakes, which function similarly to earthquakes here on Earth--except with much more intense results. A crack in the crust of a magnetar is responsible for the brightest light we've ever observed from space. And if a magnetar was closer to us, like 10 light years away, and blasted us with the radiation from a starquake, it would destroy our ozone layer and probably kill all life on Earth.

But don't worry--thankfully, there aren't any magnetars near Earth. The closest one is about 9,000 light years away. Let's pray that it stays that way.