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Sirius

Alpha (α) Canis Majoris
Blue Star

Right Ascension 6h 45m 09s Best Seen 2/15 - 4/15
Declination -16° 42' 58" Magnitude -1.42
Constellation Canis Major

Actual
Compared
to Sun
Distance 8.60 ly --
Actual Brightness -- 21
Surface Temperature ~18,000 ºF ~1.8
Diameter (average) ~1.2 million miles ~1.4
Mass -- ~2
Surface Gravity -- --
Surface Composition (by mass) 74% hydrogen
24% helium
2% everything else
same
Spectral Type A1 V G2 V
Density (gram/cubic cm) -- --

What To Look For Through The Telescope


  1. Recommended eyepiece: 24mm or 40 mm.

  2. When people look through the telescope a bright bluish point of light should be seen.

Sirius Information:

  1. Sirius is the brightest star in the night-time sky (considering bright stars in both the Northern and Southern Hemisphere).

  2. Sirius is the 6th nearest known star.

  3. Sirius also has a white dwarf companion.

    Period 50 years
    Separation highly elliptical orbit, so separation varies between ~744 million miles to ~2.88 billion miles
    (~8 to ~31 times the Earth-Sun distance)
    Mass ~equal to sun
    Diameter 7,300 miles
    Density ~90,000 times the sun’s density (125,000 times that of water or 2.25 tons/in3)
    Luminosity ~1/400 of the sun’s
    Temperature 44,500 ºF (25,000K)
    Spectral Type A2-5 VII
  4. Over many, many years, the motion of Sirius through the sky can be detected. In 1718, Sir Edmund Halley was the first to reveal that stars were not permanent fixtures in the sky by detecting the motion of Sirius.

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References
Item Updated Notes
Coordinates 2002-07-17 SIMBAD
Magnitude 2002-07-17 with Scott’s The Flamsteed Collection
Distance 2002-07-22 with The Flamsteed Collection
Actual Brightness 2002-07-22 with The Flamsteed Collection
Surface Temperature 2002-07-22 assume A type stars’ top temp (A0 stars?) of 10,000K
Diameter 2002-07-22 assume temp 10,000K
Mass 2002-11-20 http://www.astro.uiuc.edu/~kaler/sow/sirius.html and http://chandra.harvard.edu/photo/cycle1/0065/
Surface Gravity --
Surface Composition 2003-01-06 OK for all stars
Spectral type 2002-07-22 SIMBAD
Other Information 2002-08-30 1. previous: 5th nearest known star – BUT with Hipparcos, 6th nearest
2. previous: “Sirius also has a white dwarf companion:
Period: 50 years
Separation: 22 billion miles (24 times the Earth-Sun distance)
Mass: ~equal to sun
Diameter: 16,000 miles
Density: 90,000 times the sun’s density (125,000 times that of water or 2.25 tons/in3)
Luminosity: 1/400 of the sun’s
Temperature: 15,000 to 16,000 oF Spectral Type: A5" – BUT can only find current info based on: http://www.solstation.com/stars/sirius2.htm and http://antwrp.gsfc.nasa.gov/apod/ap001006.html
3. Item 4 from Scott’s Starlist 2000
Changed composition (2013-07-30)
Changed from: 70% hydrogen, 28% helium, 2% everything else
to 74% hydrogen, 24% helium, 2% everything else