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Alpha (α) Boötis
Arcturus
Red Giant Star
| Right Ascension | 14h 15m 39s | Best Seen | 5/1 - 9/1 |
| Declination | 19° 10' 57" | Magnitude | -0.06 |
| Constellation | Bootes | ||
| Actual | Compared to Sun | |
| Distance | ~37 ly | -- |
| Actual Brightness | -- | -- |
| Surface Temperature | ~7,500 °F | ~0.74 |
| Diameter | 20 million miles | 25 |
| Mass | -- | 1.5 |
| Surface Gravity | -- | -- |
| Surface Composition (by mass) | 74% hydrogen 24% helium 2% everything else |
same |
| Spectral Type | K2 III | 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 reddish-orange point of light should be seen.
Arcturus Information:
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Arcturus is the 2nd brightest star in the Northern Hemisphere’s night sky (3rd brightest when including the Southern Hemisphere’s bright stars.)
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Arcturus became famous when its light was used to open the 1933 World’s Fair in Chicago. That light had left Arcturus at about the same time as the previous Chicago Fair in 1893.
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Arcturus may have a companion, only four times as luminous as the sun. However, this is unconfirmed.
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References
| Item | Updated | Notes |
| Coordinates | 2003-01-06 | tweaked a bit |
| Distance | 2003-01-06 | OK with Scott’s The Flamsteed Collection and SIMBAD – NOTE: this is a combined mag of the two components |
| Actual Brightness | 2003-01-06 | previously said 115 – BUT Scott’s Flamsteed says there are two stars with different luminosities. However, I can’t find support for this companion anywhere else |
| Surface Temperature | 2003-01-06 | close enough to source which says precisely defined at 4290 K http://www.astro.uiuc.edu/projects/sow/arcturus.html |
| Diameter | 2003-01-06 | matches with http://www.astro.uiuc.edu/projects/sow/arcturus.html |
| Mass | 2003-01-06 | previously said 4 – but site says 1.5 http://www.astro.uiuc.edu/projects/sow/arcturus.html |
| Surface Gravity | -- | |
| Surface Composition | 2003-01-06 | OK for all stars |
| Spectral Type | 2003-01-06 | OK with Scott’s Flamsteed |
| Density | 2003-01-06 | previously said: .0003 times sun – BUT can find no support for this |
| Other Information | 2003-01-06-2003 | World’s Fair info from http://www.astro.uiuc.edu/projects/sow/arcturus.html Companion info from Scott’s Flamsteed |