The composite is linked above above, from this starting point for all this here on hubblesite.org. There are links to the individual images from the five telescopes involved, covering five spectral regions. Highly recommended.
- Very Large Array (radio)
- Spitzer Space Telescope (infrared)
- Hubble Space Telescope (visual)
- XMM-Newton (ultraviolet)
- Chandra X-ray Observatory (X-ray)
"We have also used the Atacama Large Millimeter/submillimeter Array (ALMA) to produce the first detailed radio continuum image of the center of the nebula at 100 GHz, although the ALMA observations were not contemporaneous with the others ..."The features near the center of the nebula were moving at ~ 20% light-speed, and over ~6 months of observations of a supernova remnant that is 'only' 6500 light years away, had moved ~2 seconds of arc. Which led to a corrupted image.
Too bad, but of course there is a lot going on in the immediate vicinity of a pulsar.
Before leaving that page, I have to point out this short linked video https://media.stsci.edu/uploads/video_file/video_attachment/4408/STScI-H-v1721a-1280x720.mp4. It morphs the images through the spectrum, and it's annotated by spectral band. There's also a version without the annotations.
If you'd like to see changes in the Crab Nebula, similar to what I mentioned mentioned, here you go. This is from Chandra as well, but the page won't load. So here it is on YouTube. Seven months of changes, very near the pulsar, in a few seconds.
So, what else goes on in a nearby supernova remnant?
A lot. As one might expect, there is a lot of very energetic physics packed into a small area, only 6500 light-years away. When the supernova which left the Crab Nebula behind was recorded by Chinese, Japanese, and middle eastern astronomers in 1054, it would have been easily brighter than any star or planet in the sky.
What began as a star on the order of 10 times the mass of the sun, left a neutron star only about 20 miles across, but weighing ~4.5 billion pounds per cubic inch. It's rotating 30 times per second, because angular momentum was conserved during the explosion. The energy it radiates doesn't stop in the X-ray regime that was observed by Chandra, but extends all the way up to ~10 TeV. That is similar to the LHC, whose initial energy was 7 TeV, but is now running at 13 TeV, but at a vastly higher power level. The LHC beam, after all, is about the diameter of a sewing needle.
The magnetic fields involved are enormous. That doesn't happen due to a conservation law, as in rotation; in fact exact mechanism is still unclear. What is clear is that their reach is large. Here's an image from NASA's Hubble Captures the Beating Heart of the Crab Nebula (recommended). That pearly blue glow is synchrotron radiation, produced by electrons spiraling in a magnetic field.
Everything near a pulsar that can be ionized is ionized due to those high-energy emissions. What's left are carbon and silicate dusts, and even those seem likely to be mostly charged, though electrostatically). So we have positively charged ions, and those now-free electrons. Those free electrons are pervasive, hence the blue glow.
That ionization, the pulsars intense gravitational and magnetic field, and rotation combine to give rise to those famous pulses that gave pulsars their name. The basic mechanism is
- some of the material ejected in the supernova is pulled back into the star
- the in-fall is caught in the magnetic fields, and pulled toward the poles
- it's beamed back out at the poles, rather like lighthouse beams
- the beam sweeps across us, in this case 30 times per second
4. is possible because the axis of rotation is not aligned with that of the magnetic field. That seems a bit counter-intuitive, but it's also the case with the sun, and even here on earth (and something that has to be considered when navigating by compass). That's too much to go into here; books have been written about the Crab. Search on 'dynamo effect' or 'dynamo theory'.
We have been learning about this for a millennium now. While the pace of discovery is accelerating, the story of the Crab Nebula is far from told.
