Neutron Star Measures Just 22 Kilometers Across

A typical neutron star with a radius of eleven kilometres is about as large as a medium-sized city. Credit: NASA's Goddard Space Flight Center

How big is a neutron star? These extreme, ultra-dense collapsed stars are fairly small, as far as stellar objects are concerned. Even though they pack the mass of a full-sized star, their size is often compared to the width of a medium-to-large-sized city. For years, astronomers have pegged neutron stars at somewhere between 19-27 km (12 to 17 miles) across. This is quite actually quite precise, given the distances and characteristics of neutrons stars. But astronomers have been working to narrow that down to an even more precise measurement.

An international team of researchers has now done just that. Using data from several different telescopes and observatories, members of the Max Planck Institute for Gravitational Physics, theAlbert Einstein Institute (AEI) have narrowed the size estimates for neutron stars by a factor of two.

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Astronomers Map the Surface of a Pulsar

Simulation of a possible quadrupole magnetic field configuration for a pulsar with hot spots in only the southern hemisphere. Credits: NASA's Goddard Space Flight Center

When stars exhaust their supply of fuel, they collapse under their own weight and explode, blowing off their outer layers in an event known as a “supernova”. In some cases, these events leave behind neutron stars, the smallest and densest of stellar objects (with the exception of certain theoretical stars) that sometimes spin rapidly. Pulsars, a class of neutron star, can spin up to several hundred times per second.

One such object, designated J0030+0451 (J0030), is located about 1,100 light-years from Earth in the Pisces constellation. Recently, scientists using NASA’s Neutron star Interior Composition Explorer (NICER) were able to measure the pulsar’s size and mass. In the process, they also managed to locate the various “hot spots” on its surface, effectively creating the first map of a neutron star.

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Astronomers Finally Find the Neutron Star Leftover from Supernova 1987A

A composite image of SN 1987A from Hubble, Chandra, and ALMA. Image Credit: By ALMA (ESO/NAOJ/NRAO)/A. Angelich. Visible light image: the NASA/ESA Hubble Space Telescope. X-Ray image: The NASA Chandra X-Ray Observatory - http://www.eso.org/public/images/eso1401a/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=30512379

Astronomers at Cardiff University have done something nobody else has been able to do. A team, led by Dr. Phil Cigan from Cardiff University’s School of Physics and Astronomy, has found the neutron star remnant from the famous supernova SN 1987A. Their evidence ends a 30 year search for the object.

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