OK, Facts from Wikipedia:
Located at a distance of about 6,300 light years (2 kpc) from Earth, the nebula has a diameter of 11 ly (3.4 pc) and is expanding at a rate of about 1,500 kilometers per second.
Considering that 1500 kilometers per second is 3300 miles per second in a day that would mean that the nebula expanding 285,120,000 miles a day.
In a month that would be 59,875,200,000 billion miles.
Why doesn't this nebula look massive in the sky? How can it be so consistent with it's appearance?
2007-12-15 09:46:44 · 6 answers · asked by Jansen J 4 in Science & Mathematics ➔ Astronomy & Space
1500 km per second is only 932 miles per second, not 3300.
So it is expanding at the rate of 83 million miles a day.
And while that sounds like a lot to humans, its really only a small distance cosmologically speaking.
But since the nebula was first observed in a telescope in 1931 (the independantly found by Messier in 1758), it has changed its appearance somewhat over those centuries.
As to looking massive in the sky, it isn't huge because of its distance (6300 light years is a long way).
It only covers about 6 arcminutes of the sky (by comparison, the full moon subtends 30 arc minutes).
So it appears very small in the sky (and its not a bright star, its apparent magnitude is 8.4, so it can't be seen with the naked eye).
2007-12-15 10:14:06 · answer #1 · answered by Anonymous · 2⤊ 0⤋
That is because a light year is 5,900,000,000,000 miles, and at that rate the nebula's expansion in a year is much less than that as your figures show. There has been however a definite expansion of the Crab Nebula detected in photographs taken since the first time it was photographed. In a century the nebula grew considerably larger as stars that were outside the nebula are now seen in front of or behind it. The nebula is a very young supernova remnant. We're seeing it as it was some 950 years after it was formed by the supernova that left the neutron star that makes it glow. In thousands of years, it will probably expand into something resembling the Veil Nebula. The expansion of the nebula will slow down as it plows into more and more interstellar gas as it continues to grow larger.
2007-12-15 18:00:27 · answer #2 · answered by Anonymous · 1⤊ 0⤋
Hello, Jansen!
The distance to the Crab Nebula from Earth is, quite literally, astronomical!
At a distance of just over 6,000 light- years, its expansion rate is barely detectable...
Remember, too, that as a supernova remnant expands, it cools, and thus, loses its apparent brightness.
It was first witnessed on or about July 4 (how's THAT for a date?), by Chinese astronomers, and was so bright, the resultant flash could be seen during daylight!!!
Best Wishes!
Bobby
P.S. Why don't you check out my earlier question that was posted... I'd like to hear from you!
B
2007-12-15 17:56:23 · answer #3 · answered by Bobby 6 · 0⤊ 0⤋
1500km is 937.5 miles not 3300 which means it is expanding at 81million miles a day
2007-12-15 18:02:22 · answer #4 · answered by tentofield 7 · 0⤊ 0⤋
you have to use calculus to understant this ! you have to find the rate of the increase based on what an observer sees on the earth ! whcih would be a small small number !
2007-12-15 20:15:16 · answer #5 · answered by Ali 4 · 0⤊ 0⤋
>Maybe it's far, far away...and nebulous.<
2007-12-15 17:56:56 · answer #6 · answered by Druid 6 · 0⤊ 0⤋