The Motion of RX J185635-3754 - The Nearest Neutron Star to Earth
This photograph is the sum of three Hubble Space Telescope images. North is down, east is to the right. The image, taken by the Wide Field and Planetary Camera 2, is 8.8 arc seconds across (west to east), and 6.6 arc seconds top-to-bottom (south to north). An arc second is a unit of angular measure. There are 3,600 arc seconds in 1 degree and 360 degrees in a full circle.
All stars line up in this composite picture, except the neutron star, which moves across the image in a direction 10 degrees south of east. The three images of the neutron star are labeled by date. The proper motion is 1/3 of an arc second per year. The small wobble caused by parallax (not visible in the image) has a size of 0.016 arc seconds, giving a distance of 200 light-years.
NASA and F.M. Walter (State University of New York at Stony Brook)