A question about supernovas and the Crab Nebula

Status
Not open for further replies.
S

soul

Guest
It is said that supernovas can only come from red giants. If that is so then how come the supernova that occurred approximately 1000 years ago was seen to have happened from a blank piece of sky in the constellation Taurus. It was the "quest star" according to the Chinese. Wouldnt a red giant have been visible or any star for that matter but especially a red giant in that part of the sky BEFORE the supernova. I mean after all a red giant at that close proximity (the crab nebula is not that far away in cosmic terms) would have been seen would it not ? This question been on my mind some time. Please help to answer.
 
T

thalion

Guest
^<br />Good post; mine just follows up on what you did.<br /><br />IIRC, a red supergiant like Betelguese or Antares typically has an absolute magnitude of about -5.5. Using a ballpark estimate for the Crab Nebula's distance at 6500 ly (~2000 pc), and the familiar distance modulus formula of:<br /><br />m-M = 5logD-5<br /><br />where:<br /><br />D = parsecs<br />m = apparent magnitude<br />M = absolute magnitude<br /><br />--I derived a distance modulus of 11.5 magnitudes for the nebula. Assuming its progenitor had an absolute magnitude of -5.5, it would have been only magnitude 6, near the commonly-held threshold of naked-eye vision. This is of course neglecting interstellar dust absorping its light, which I'm guessing would knock it down at least another magnitude or two.<br /><br />In short--its progenitor was probably quite inconspicuous.
 
S

soul

Guest
interesting responses...im learning more everyday. I just thought because it was not all that far in cosmic terms it would have been seen being such a big red super giant star. My mistake. Thanks for the responses. <br /><br />Just curious are you both astronomers or just very informative people in this area ? You both seem to know your stuff.
 
T

thalion

Guest
<<Just curious are you both astronomers or just very informative people in this area ? You both seem to know your stuff. >><br /><br />"I'm just a guy." <img src="/images/icons/wink.gif" /><br /><br />I've never even taken a college astronomy course; I'm just someone who's been interested in the field for most of my life, and who has been a voracious reader of the available material. I'm also an amateur astronomer, though these days it's more armchair (hides).
 
Status
Not open for further replies.

ASK THE COMMUNITY

Latest posts