As Orion strides forward, bow in hand, he seems to confront the constellation Taurus, the bull. A small telescope will reveal, near the tip of the bull’s southern horn, a faint patch of light. It is called the Crab Nebula, and in a large telescope, it appears to be an explosion in progress, as shown on page 9. If the Orion Nebula is a stellar nursery, then the Crab Nebula next door may be the grave site of a star that suffered a death of unimaginable violence.

That heavenly cataclysm may have been recorded by Chinese astronomers who described a “Guest Star” in Taurus that suddenly appeared on July 4, 1054, and shone so brightly that it was seen during the daytime for 23 days. “For a few weeks,” notes astronomer Robert Burnham, “the star was blazing with the light of about 400 million suns.” Astronomers call such a spectacular stellar suicide a supernova. Even now, nearly a thousand years after the observation, the bombshards from that blast are racing through space at a speed estimated at 50 million miles [80 million km] per day.

The Hubble Space Telescope has been at work in this area too, peering deep into the heart of the nebula and discovering “details in the Crab that astronomers never expected,” according to Astronomy magazine. Astronomer Paul Scowen says the discoveries “should have theoretical astronomers scratching their heads for some time to come.”

Astronomers, such as Harvard’s Robert Kirshner, believe that understanding supernova remnants like the Crab Nebula is important because they can be used to measure the distance to other galaxies, which is currently an area of intense research. As we have seen, disagreements over the distances to other galaxies have recently touched off a lively debate over the big bang model of the creation of the universe.

At the heart of the Crab Nebula lies one of the strangest objects in the known universe. According to scientists, the tiny corpse of a deceased star, compressed into unbelievable densities, spins in its grave 30 times per second, sending out a beam of radio waves that were first detected on earth in 1968. It is called a pulsar, described as a spinning supernova remnant so compressed that the electrons and protons in the atoms of the original star have been squeezed together to produce neutrons. Scientists say it was once the massive core of a supergiant star like Betelgeuse or Rigel in Orion. When the star exploded and the outer layers were blasted into space, only the shrunken core was left, a glowing white-hot cinder, its nuclear fires long extinguished.

The Crab Nebula in Taurus—a stellar grave site?