Hubble Space Telescope Watched This Explosion for 25 Years!

The Hubble Space Telescope has now been looking at the Crab Nebula for 25 years. This long-term imaging means that we can watch a supernova expand in real time, see the shells of dust and gas moving on human time scales. We now have an unparalleled, detailed look at the aftermath of a supernova, and can watch how it's evolved over the last quarter of a century. The Crab Nebula is probably the most famous supernova remnant in the night sky. It's the remains of a star that exploded in 1054 when medieval astronomers noted a new, bright star in the sky, that for weeks was visible even during the day. Now we know they were looking at this supernova as it happened, and what's left of the star is the Crab Nebula. It's a beautiful, expanding cloud, located 6,500 light-years from Earth in the Taurus constellation. We often think of the night sky and space as being unchanging, static, immutable things. However, Hubble has now been in service for 35 years, and by repeatedly imaging objects like the Crab Nebula over that length of time, we can reveal that they're in motion and we can see it happening. What's really cool is that the material in this image is actually moving really, really fast, but it only looks like tiny changes to us because the distances involved are so massive. Hubble first imaged the nebula over 25 years ago in 1999, and the new image captures the intricate filamentary structure and its motion outwards over those years. The material is moving out from the star at a pace of 3.4 million miles an hour. It looks like it hasn't moved far, but that's only because the distances here are absolutely enormous. The entire nebula is about 11 light-years in diameter, although the neutron star at the center, the remnant of the exploded star that created the nebula, is just 30 kilometers across. This means that although the material looks like it's expanded only a little bit, it's really traversed millions and millions of kilometers in that time. For an even better comparison, the old 1999 image has been reprocessed to match the colors of the new images, hence why the time lapse looks so seamless and beautiful. The color variations across the images show a combination of changes in temperature, density of the gas and dusty debris, as well as the exact chemical composition of the material. Something pretty cool to notice is that the filaments around the edge of the nebula look like they've moved more than those in the center, and rather than stretching out over time, they look like they've simply moved outwards. In other well-known supernova remnants, the expansion outward is driven by shock waves from the initial explosion, but here it's a little bit different, which might contribute to the slightly unusual expansion that we're seeing here. There's something called synchrotron radiation powering the outward wind here. It's caused by the central pulsar's magnetic field interacting with the material of the nebula. The newer image taken with Hubble actually also uses a better camera than the original 1999 image, so you can actually see the resolution get better with the newer Hubble images too. This is because Hubble is the one telescope that astronauts have visited to upgrade and fix, and the Wide Field Camera 3 was installed in 2009, which is what was used for the latest Hubble image. That new high-resolution observation also provides extra insight into the 3D structures of the crab, which can usually be pretty difficult to learn about from 2D images. Shadows from some of the filaments can be seen on the haze of synchrotron radiation in the center of the nebula, giving us a sense of position and proximity. Counter-intuitively, some of the brightest filaments in the new Hubble image show no shadows, telling us they must be actually on the far side of the nebula, and much further away than the closest filaments. Excitingly, Hubble data can now also be paired with recent data from other telescopes to get detailed observations in more wavelengths of light. For example, JWST released an infrared image of the nebula in 2024, which shows the crab in incredible detail, and in a way that Hubble simply cannot access. This is something we can look forward to more of in the future, so stay tuned for even more exciting images and updates from the crab nebula, centuries after humans first saw the explosion. Leave me any questions and comments you have down below, and subscribe if you want to learn more spacey goodness together. Until next time, stay safe team, I'll see you soon. Bye!