2006-12-09 14:38:28 · 7 answers · asked by Sidd 2 in Science & Mathematics ➔ Astronomy & Space
The apparent change of position of a star on the celestial sphere is called the proper motion of the star.
Barnard's Star
Proper motion is not large. The star with the largest proper motion is called Barnard's Star. It moves 10.3 seconds of arc per year. Since the moon subtends about 1/2 of a degree (which is 1/2 x 60 x 60 = 1800 seconds of arc) on the celestial sphere, it takes Barnard's star about 1800/10.3 ~ 180 years to change its position by the angular diameter of the moon. All other stars have smaller proper motions.
2006-12-09 14:40:50 · answer #1 · answered by DanE 7 · 1⤊ 0⤋
Barnard's star has the largest proper motion of any known star—10².25 arc annually. It is a red dwarf star with a visual magnitude of 9.5; its intrinsic luminosity is only 1/2,300 that of the Sun.
Because of its high velocity of approach, 108 km (67 miles) per second, Barnard's star is gradually coming nearer the solar system and by the year 11,800 will reach its closest point in distance—namely, 3.85 light-years. The star is of special interest to astronomers because its proper motion, observed photographically between the years 1938–81, has shown periodic deviations of 1 micrometre, or 0².02 of arc. This “perturbation” is interpreted as being caused by the gravitational pull of two planetary companions having orbital periods of 13.5 and 19 years, respectively, and masses of about two-thirds that of Jupiter. The existence of planetary bodies outside the solar system, however, remains unproved.
2006-12-09 14:41:42 · answer #2 · answered by Anonymous · 1⤊ 0⤋
Star - Wikipedia, the free encyclopedia
... the properties of a star by observing its spectrum, luminosity and ... Other than the Sun, the star with the largest apparent size is R Doradus, with ...
Quick Links: Observation history - Star designations - Units of measurement
http://en.wikipedia.org/wiki/Star
2006-12-11 03:36:43 · answer #3 · answered by Krishna 6 · 0⤊ 0⤋
Barnard's star is correct for two reasons. It's one of the closest stars, and it's a population 2 star. Unlike us, it doesn't orbit the galactic centre in the plane of the galactic disc. All the nearby stars which orbit in the same plane as the Sun does, travel around the galactic centre at nearly the same speed as us. Barnard's star's galactic orbit is at an angle to ours, so it's velocity is different to ours.
2006-12-09 15:29:13 · answer #4 · answered by zee_prime 6 · 1⤊ 0⤋
Beyonce
2006-12-09 14:45:48 · answer #5 · answered by Anonymous · 0⤊ 1⤋
Sun.
2006-12-09 14:40:35 · answer #6 · answered by robert m 7 · 0⤊ 1⤋
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2006-12-09 22:52:09 · answer #7 · answered by Anonymous · 0⤊ 0⤋