Astronomy Picture of the Day . The Case of the Missing Supernova Companion . ... Credit Copyright: X-ray: NASA / CXC / SAO / J. Hughes et al., Optical: NASA / ESA / Hubble Heritage Team ( STScI / AURA ) Explanation: Where's the other star? At the center of this supernova remnant should be the companion star to the star that blew up. ... This indicates that the companion is intrinsically very faint -- much more faint that many types of bright giant stars that had been previous candidates. ...