The Changing X-ray Brightness of SS 433 (Illustration)

This illustration shows the object known as SS 433, located in the Milky Way galaxy and only about 20,000 light-years from Earth. Researchers think SS 433 is an ultraluminous X-ray source, or ULX, a compact cosmic object that must have an X-ray luminosity that is about a million times the total luminosity output of the Sun (at all wavelengths). ULXs are so bright, they can be seen millions of light-years away, in other galaxies. SS 433 appears to be about 1,000 times dimmer than the minimum threshold to be considered a ULX. This faintness is likely a trick of perspective: The high-energy X-rays from SS 433 are initially confined within two cones of gas extending outward from opposite sides of the central object. These cones are similar to a mirrored bowl that surrounds a flashlight bulb: They corral the X-ray light from SS 433 into a narrow beam, until it escapes and is detected by NuSTAR. But because the cones are not pointing directly at Earth, NuSTAR can't see the object's full brightness. Animation available at https://photojournal.jpl.nasa.gov/catalog/PIA24574