Vulcan Astronomy

Vulcan Astronomy The Earth's sun (called Sol) is 16 light years from the Vulcan Suns, the bigger of which is called Vulcanis. The Humans also call Vulcanis, 40 Eridani A. The Vulcan year is approximately 250 Earth days in length and the day is roughly 27 Earth hours long. Eridani A is circled by its smaller companions, Eridani B and Eridani C.

Excerpt from United Earth Public Astronomical Archive, 2165
ENTRY: Vulcan (edited)

The Vulcan homeworld is a double planet in what the Terrans called the 40 Eridani system, dubbed Vulcan by Terran explorers unable to pronounce the native name (abbreviated T'Khasi). Vulcan is a large, dry world with only 14% surface water, high temperatures, and a thin atmosphere.Its sister world T'Khut (dubbed Charis by the Terrans) is a highly volcanic world, with frequent storms and no native life.

Vulcan Planet

Vulcan's sun is identified as 40 Eridani (and sometimes Omicron 2 Eridani) in human starcharts. 40 Eridani is 4 billion years old, about the same age as Sol. Vulcan's daytime star is a 4.4-magnitude multiple system about 4.9 parsecs (about 16 light-years) from Terra. Vulcan orbits the primary star, an orange main-sequence dwarf of spectral type K1 V with a solar cycle of roughly 11 years, just like Sol. The following is a list of 40 Eridani's general specifications.

Surface temperature: 5,000 deg K
Luminosity: 30 percent of Sol's
Diameter: 783,000 miles
Mass: 75 percent of Sol's
Density: 4 percent greater than Sol's
Absolute magnitude: 6.0

40 Eridani B and C, the other two stars in this trinary system, are both situated 400 AU (about 2 light-days or 40 billion miles) from 40 Eridani A, an enormous distance. 40 Eridani B and C orbit each other every 248 earth-years, at an average distance from each other of 44 AU. In turn, 40 Eridani B and C, together, orbit 40 Eridani A every 8000 or so earth-years.

40 Eridani B is a white dwarf of spectral type A VII.Below is Eridani B's other specs as compared to those of Sol.

Surface temperature: 13,000 deg K
Luminosity: 0.27% of Sol's
Diameter: 17,000 miles
Mass: 44 percent of Sol's
Density: 65,000 times greater than Sol's
Absolute magnitude: 11.2

The enormous density of 40 Eridani B is typical of a white dwarf. The stellar material of 40 Eridani B is 90,000 times denser than water; a cubic inch of it weighs 2 tons, and the surface gravity of the star is 37,000 times that of Terra.

40 Eridani C is a very faint red main-sequence dwarf of spectral type M4e V. Below is Eridani C's the star's other specs, as compared to those of Sol:

Surface temperature: 3000 deg K
Luminosity: 0.08% of Sol's
Diameter: 374,100 miles
Mass: 20 percent of Sol's
Density: 80 percent greater than Sol's
Absolute magnitude: 12.3

Vulcan orbit's its sun at a distance of 0.56 AU or 52,360,000 mi. At this distance, 40 Eridani A appears from Vulcan as a disk 0.86 arc-degrees in diameter.

40 Eridani B and C are much too far away from 40 Eridani A to appear as disks from Vulcan; they appear as very bright points of light to the naked eye. 40 Eridani B appears as a blazing silver-white star shining at magnitude -7.4 in the Vulcan sky. 40 Eridani C appears as a brilliant blood-red star of magnitude -6.3. Of course, the apparent distance between B and C would change as they orbit each other, but from Vulcan, B and C always appear near each other--in fact, even when B and C are as far apart as they ever get, they appear together in the Vulcan sky only as far apart as the width of your fist held out at arm's length.

Both B and C are bright enough to be easily visible in Vulcan's daytime sky, though (at their distance) they don't contribute much to Vulcan in the way of light and heat. At night, they shine with a combined magnitude of -7.8, some 22 times brighter than our brightest Venus. Enough to cast a dim shadow, around the time that B and C are in opposition, but dim enough to let night remain night.

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