Originally Posted by
rickair7777
Fortunately we're cataloging the dangerous ones. I'd feel better if we had a defense capability on the shelf, but at this point I think we have enough advance notice on any extinction size objects.
Interestingly, I recently learned that the Chicxulub Asteroid impact caused such mass extinction more so because of its angle of arrival, rather than its mass. I recall that it impacted at about a 30 deg angle, which caused it to "skip" several times, before coming to a stop, and that this caused much more heat to be released into the atmosphere than a 90 deg impact angle would have.
Of course none of this is first hand knowledge
Near earth supernovas and Gamma Ray Bursts are another one, but I don't think we'll be close enough in our galactic orbit for at least tens of millions of years to be near any stars that are massive enough to go supernova.