even once in our life time ?
2006-11-26 01:28:14 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
225 million years is the best guestimate, so for a star that is 4.5 billion years old, that means it has completed 20 or 21 orbits so far,
Some of the effects of this rotation include:
a) we get a different north pole star, every few thousand years. Polaris hasn't got a permanent job. It is merely the current occupant of pole position.
Polaris has a visual magnitude of 1.97 (second magnitude). In 3000 BC the faint star Thuban in the constellation Draco was the North Star. At magnitude 3.67 (fourth magnitude) it is only one-fifth as bright as Polaris. The first magnitude star Vega will be the North Star by AD 14,000.
b) which stars are nearest to us will vary over time. Barnard's Star, currently 5.96 light years away (and the fourth nearest star) is moving towards us fast and will be 3.8 light years away (nearer than Proxima and Alpha Centauri therefore) and it will be the nearest star around AD 11,800.
So those astronomy textbooks will need rewriting, and not just because of Pluto's status being changed!
2006-11-26 02:44:48 · answer #1 · answered by Anonymous · 6⤊ 1⤋
It takes roughly 225 million years.
2006-11-26 09:37:34 · answer #2 · answered by Gene 7 · 2⤊ 0⤋
its believed to take about 200 to 250 million years
2006-11-26 09:37:45 · answer #3 · answered by blondnirvana 5 · 0⤊ 0⤋
A lifetime doesn't even come close. A rough figure for a galactic "year" at our distance from the galactic center is 25,000 years. So don't hurry out to buy next "year"s galactic calendar.
2006-11-26 09:58:49 · answer #4 · answered by JIMBO 4 · 0⤊ 2⤋