Thursday, July 5, 2007

Sirius AB

Star type
g A: A0-1 Vm (slightly bluish, white main sequence dwarf star)
g B: DA2-5 /VII (white dwarf stellar remnant)

Distance from Earth
g 8.601 ly

Star Service No.
g NA

g 225 my to 250 my

(times Sol)
g A: 168% to 171%; 202% to 214% (one cubic inch of its material would weigh about 15 tons at Earth’s surface); NA
g B: About 7,300 miles, or about 92% of Earth; 100% to 103.4%; NA

Brightness (xSol)
g A: 21.61 times brighter
g B: 8,200 times fainter than Sirius A and 360 times fainter than Sol; much brighter source of x-rays than Sirius A

g A: Rich in elements heavier than hydrogen as it has about one to 7.4 times the iron abundance
g B: Young white dwarf, a remnant stellar core, which enriched Sirius A with elements heavier than hydrogen when it cast off its outer gas layers

Comparison to Sol
g See illustration

Picture of star
g A-B: See picture at above right, taken by Hubble telescope
g A: See picture
g B: NA

Star system features
g Past B: Carbon-core white dwarf, one that may have evolved from a 5.05 Solar-mass, B-type main-sequence star about 124 my ago, after 101 my to 126 my as a giant star; was once brighter than Regulus A, currently a B7 main-sequence star.
g Future A: Will exhaust its core hydrogen within only a billion years and turn into a red giant or Cepheid variable before puffing away its outer layers to reveal a remnant core as a white dwarf

Known planets
g A: Unknown
g B: Unknown but unlikely to have brown dwarf companion

Habitable zone
g A: 4.6 AUs (at about the distance of Jupiter from Sun), with orbital period would be 6.8 years long; orbit of any protoplanet forming around Sirius A at that distance could have been disrupted by the close orbit of Sirius B, and also probably during B's mass loss when it became a nova then a white dwarf. Even if it is possible for an Earth-type planet to orbit youthful Sirius A and develop life, it is likely to be primitive single-cell, anaerobic bacteria under constant bombardment by meteorites and comets as Earth was for the first billion years. Since there is unlikely to be free oxygen in the atmosphere of such a planet, it probably would not have an ozone layer (O3) although Sirius A puts out a lot more hard radiation (especially ultraviolet) than Sol. A planet at Earth-equivalent orbit would receive 28.3 kilowatts of solar energy per square meter.Probability of habitable planet: 3.6%.
g B: None likely

Orbital map
g Close binary, separated on average by only about 19.8 AUs of an orbital semi-major axis; distance separating Sirius A from its companion varies between 8.1 and 31.5 AUs as the two swing around in a highly eccentric orbit (e= 0.59) that takes 50.1 years to complete; possibly moving towards the galactic center
g Orbital map

View from star
g NA

Nearby stars
(Star systems with 10 light years)
g Procyon AB, 5.2 ly
g Ross 614 AB, 5.5 ly(?)
g Luyten's Star, 5.8 ly
g Kapteyn's Star, 7.5 ly
g Epsilon Eridani, 7.8 ly
g Sol, 8.6 ly
g LHS 1565, 8.9 ly
g Wolf 359, 9.0 ly
g DX Cancri, 9.2ly
g Proxima Centauri, 9.3 ly
g Alpha Centauri AB, 9.5 ly
g LTT 12352, 9.9ly

Map locating star system
g Stellar map of stars within 10 ly of Sun
g Stellar map of stars within 47 ly of Sun

Location in Earth sky
g North central part of Constellation Canis Major, the Larger Dog; Sirius is also the lower left member of the “Winter Triangle” of first magnitude stars, whose other components are Procyon at upper left and Betegeuse at right center; Sirius A is brightest star in the night sky, but Sirius B cannot be perceived with the naked eye

Other names
g A: Alpha Canis Majoris A
g A: Dog Star, Alp or Alf CMa
g A: 9 CMa
g A: HR 2491
g A: Gl 244 A
g A: Hip 32349
g A: HD 48915
g A: BD-16 1591
g A: SAO 151881
g A: FK5 257
g A: LHS 219
g A: ADS 5423 A
g B: The Pup

Sci-fi mentions
g Location of an Earth colony in Frederik Pohl's "The Day the Icicle Works Closed"
g In Alfred Bester’s “The Die-World,” is home of the Galactic Envoy, described as having a praying mantis face, who is the first alien to visit Earth
g Jinx is a habitable moon orbiting a gas giant primary around Sirius A in several Larry Niven stories; the Bandersnatch, native to the moon, are a genetically engineered species planted there; explorers find life on planet Sirius B-IV in his short story "Becalmed in Hell"
g One of Voltaire's characters in Micromegas (1752) is a giant eight leagues tall and possessing more than a thousand different senses from the Sirius star system
g Dogon (an East African tribe) mythology claims Nommos, amphibious creatures from the Sirius star system, landed their spaceship among them 4,000 years ago
g An octopuslike tentacled being covered with bright green fur inhabit 12 planets orbiting the Sirius binary in Frederik Pohl's "The Age of the Pussyfoot"
g In "Star Trek: The Animated Series", Harry Mudd visits Sirius IX after events of "I, Mudd" and before events of "Mudd's Passion"

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