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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 |
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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
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Recommended eyepiece: 24mm or 40 mm.
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When people look through the telescope a bright bluish point of light should be seen.
Sirius Information:
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Sirius is the brightest star in the night-time sky (considering bright stars in both the Northern and Southern Hemisphere).
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Sirius is the 6th nearest known star.
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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 -
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 |