NASA’s Hubble Space Telescope images of the Crab Nebula
Nearly 1,000 years after people first saw a bright new star appear in the sky, scientists have measured how much the remnants of that explosion continue to expand today.In July 1054, astronomers in China recorded a bright “guest star” near Tianguan, now known as Zeta Tauri.
The object was so bright that it remained visible in daylight for about a month before continuing to shine in the night sky for several more months.It is now known that this event was a supernova, a powerful explosion of a massive star. The remaining cloud of gas and dust is called the Crab Nebula.According to a report published by Space Daily, astronomers used the Hubble Space Telescope to compare new images of the Crab Nebula with images taken more than two decades ago.The comparison shows that the filaments of gas in the nebula continued to move outward, allowing scientists to directly measure changes in the remnants of the ancient star explosion.Many things in space change so slowly that people cannot notice the differences during their lifetime. The Crab Nebula is unusual because it is small, relatively close and still very active.The results were published in the Astrophysical Journal by William P. Blair of Johns Hopkins University and his team.
The Crab Nebula
The Crab Nebula is located about 6,500 light-years from Earth in the constellation Taurus. Also known as Messier 1, or M1, it is the first object listed in Charles Messier’s famous catalog of deep-sky objects.Although people saw the exploding star in 1054, the nebula itself was discovered through a telescope by John Bevis in 1731.Later, Charles Messier noticed them while searching for comets, and added them to his catalog to help astronomers avoid confusing such objects with comets.
Compare Hubble images
Instead of monitoring the nebula continuously for centuries, scientists compared Hubble images taken in 1999 and 2000 with new observations taken during the Hubble 31 mission.Because Hubble can take very detailed images, the researchers were able to see that many of the nebula’s outer filaments had moved outward over the 24-year period. These small changes helped them gauge how the remains continued to expand.
The wreckage is still moving
The study found that many of the Crab Nebula’s outer filaments have suitable motions of 0.3 arcseconds per year or more. While this motion appears small because the nebula is so far away, it represents gas moving at extremely high speeds. NASA says the gas filaments are moving outward at a speed of about 5.5 million kilometers per hour.
The Crab Nebula is not just the remnants of an ancient explosion. At its center is a Crab pulsar, a rapidly rotating neutron star left behind by a supernova.NASA says the pulsar rotates about 30 times per second. As they rotate, they produce strong magnetic fields that accelerate charged particles. These particles create the blue synchrotron glow seen inside the nebula, while older stellar material forms a network of glowing filaments around it.Because the pulsar continues to pump energy into the nebula, the remnants are still changing rather than drifting away from the original explosion.
New thread structures
The new Hubble observations were also compared with recent images taken by the James Webb Space Telescope. This helped researchers study different parts of the nebula, including gas, dust and synchrotron emissions.The team also identified two previously unidentified groups of filaments located almost facing each other around the pulsar. The researchers report the structures but say more work is needed to understand exactly how they form.
