1400 km/s
Ok, that's an acceptable speed for wandering around the neighbourhood and leaving the galaxy altogether.
Not going at anything near c though, so not a Puppeteer fleet getting the hell outta here.
The so-called Cosmic Cannonball, a neutron star moving at over three million miles an hour, has been captured in this new satellite image - or at least the red rose of supernova remnant that encases it. Puppis A supernova remnant captured by WISE Puppis A supernova remnant captured by WISE. Credit: NASA/JPL-Caltech/UCLA …
X-rays images work by emitting a beam of X-rays and looking at the shadow they cast on a detector. Does one with x ray vision emit such a beam and look for the reflections? Do surfaces/materials reflect much x-ray or is it all absorbed? Wouldn’t the emitter blind the receivers or would the X-ray source be pulsed? How big would your eyeballs have to be to be able to focus X-rays? I sense a thesis.
X-ray imaging works by looking at a shadow, since what we're looking at (bone and the like) doesn't normally emit enough x-rays to get a good image. HOWEVER, gas clouds, supernovae, and the like DO emit x-rays and thus would be quite detectable by someone who's vision worked in the x-ray band rather than in the "visible light" band. Basically, your vision would work the same, just objects would likely have a different "brightness" to them.
Forgot fluoroscopy...
http://en.wikipedia.org/wiki/Fluoroscopy
...which still leaves your head full of radiation if you look directly at the source.
search "shoe store fluoroscopes"
horrible idea.
http://www.straightdope.com/columns/read/599/were-those-old-shoe-store-fluoroscopes-a-health-hazard
I still don't see how your eyes could focus on their own fluorescence.
The so-called Cosmic Cannonball, a neutron star moving at over three million miles an hour, has been captured in a new satellite image ...
...the neutron star, which is too faint to be seen in the photograph, ..."
So it's been captured in an image that doesn't show it?
I've captured an image of a leprechaun for you...