Dust cloud reflections plus trigonometry puts Circinus X-1 at 31,000 light-years away
S. Heinz et al/U. of Wisconsin–Madison/CXC/NASA (X-ray); DSS (optical)
A cosmic bull’s-eye is helping astronomers pinpoint the distance to a neutron star. Concentric rings of X-rays bouncing off interstellar dust indicate that the stellar remnant is about 31,000 light-years away in the constellation Circinus, researchers report in the June 20 Astrophysical Journal.
The X-rays, seen blasting out of the neutron star in 2013, are reflections off dust clouds that sit between Earth and the star, designated Circinus X-1. Each of the four rings comes from a different cloud, Sebastian Heinz, an astrophysicist at the University of Wisconsin–Madison, and colleagues report. The rings are the largest and brightest known, thanks to an exceptionally powerful flare from the star and copious amounts of dust in that part of the galaxy.