Saturday, June 30, 2007

Barnard’s Star

Star type
g M3.8 V

Distance from Earth
g 5.941 ly

Star Service No.
g NA

g 10 by

g 15%-20%; >17%; NA

Brightness (xSol)
g 4/10,000th; old inactive red dwarf; will last another 40 by before cooling into a black dwarf

g 10%-32% of elements heavier than hydrogen

Comparison to Sol
g NA

Picture of star
g See picture
g See photo at upper right of page

Star system features
g Approaching Sol rapidly at 140 kilometers per second and will get as close as 3.8 ly around 11,800 CE

Known planets
g None; was once thought to have two Jupiter-class planets; for separation range of 0.017 AU to 0.98 AU, can not be planet greater than 0.12 Jupiter-mass and mass greater than 0.86 Jupiter mass

Habitable zone
g 0.034 AU to 0.082 AU, but cannot be a planet greater than 7.5 Earth-masses and mass greater than 3.1 times Neptune’s mass; orbits star in 5.75 to 21.5 days; at 1 AU, sun would be dim and very red,100 times brighter than the full Moon, and so planet would freeze solid at surface; rocky planets sparse in heavier elements of the atomic table; greater probability of gas giants made mostly of hydrogen and helium in cold, outer orbits. Probability of a habitable planet is 0.1%.

Orbital map
g NA

View from star
g Sol would have an apparent magnitude of +1.1
g Astronomers could discern that Sol possesses a Jupiter-sized planet by watching the star's wobble over a 12-year period. Jupiter would pull Sol away from its average path through space by up to 0.003 arc seconds in a pattern that repeated about every 12 years.

Nearby stars
(Star systems with 10 light years)
g Ross 154, 5.5 ly
g Sol, 6 ly
g Alpha Centauri AB, 6.5 ly
g Alpha Centauri C, 6.6 ly
g BD-12 4523 AB, 9.1 ly
g 61 Cygni AB, 9.5 ly
g Struve 2398 AB, 9.5 ly

Map locating star system
g See stellar map

Location in Earth sky
g Northernmost part of Constellation Ophiuchus, the Serpent Holder, west of Cebalrai or Kelb al Rai (Beta Ophiuchi); not visible to the naked eye

Other names
g V2500 Ophiuchus
g NSV 9910
g Gl 699
g Hip 87937
g BD+04 3561a
g LHS 57
g LTT 15309
g LFT 1385
g G 140-24
g Vys/McC 799
g Munich 15040

Sci-fi mentions
g Project Daedalus (British Interplanetary Society proposal)
g In The Legion of Space (1934), novel by Jack Williamson, Barnard's Star is home to the ancient and dreadful race of the Medusae.
g The Black Corridor (1969), novel by Michael Moorcock. Barnard's Star is the destination for a group of people fleeing from social breakdown on Earth.
g Spacecraft 2000 to 2100 AD (1978), a Terran Trade Authority book by Stewart Cowley. A fictional planet near Barnard's Star is the location of a mysterious apparition that takes the form of an unidentified spacecraft.
g The Hitchhiker's Guide to the Galaxy (1979), novel by Douglas Adams. Barnard's Star is a way station for interstellar travellers.
g Hyperion (1989-1997), novels by Dan Simmons. Barnard's Star has a farm-like habitable planet which is the homeworld of Rachel and Sol Weintraub, both being members of the 7 pilgrims.
g Rocheworld (1990), novel by Robert L. Forward. The Barnard's Star system contains one Giant planet called Gargantua and a binary rocky planed system called Roche. The first manned interstellar mission is sent to Barnard's Star using a ship with a huge solar sail impulsed by a Laser.
g The Garden of Rama (1991), novel by Arthur C. Clarke and Gentry Lee. There is a way station at Barnard's Star for the arrival and departure of massive cylindrical world ships.
g Frontier: Elite II and Frontier: First Encounters, computer games. Barnard's Star is an important Federation industrial system with heavy mining and refining industry close to Earth and the other Core Systems. It proved to be the ideal beginners trading place—no pirates and high profits, exporting robots or computers to Sol and importing Luxury Goods from there could make you a millionaire in no time at all.
g The star was a favorite of Robert L. Forward who featured it in three books. The Flight of the Dragonfly(1984) introduces Rocheworld and the Cheela species. In Timemaster (Tor Books:1992), a billionaire makes a six year journey to the star system to open a wormhole in 2049. In Marooned on Eden, co-written in 1993 with his wife Margaret, the starship Prometheus takes a crew on a 40 year mission to Zuni, and inhabitable moon around Rocheworld's neighbor, Garagantua.

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Friday, June 29, 2007

Alpha Centauri ABC

Star type
g Alpha Centauri C: M5.5Ve (main sequence red dwarf)
g Alpha Centauri A: G2 V (yellow)
g Alpha Centauri B: K0-1 V (reddish-orange dwarf)

Distance from Earth
g C: 4.223 ly
g A: 4.395 ly; To reach from Earth in 20 years, ship must average 0.21c; a one-way trip to Alpha Centauri would take, assuming a constant acceleration of 1g up to a high relativistic speed during the first half of the flight and a constant deceleration of 1g during the second half, only 3 years spaceship time, while 6 years will have passed outside the spaceship
g B: 4.395 ly

Star Service No.
g MW2

g C: 5 by-6 by, possibly 1 by
g A: 4.68 by; 6.8 by-7.6 by (if no convective core)
g B: 5.8 by

g C: 14.5%; 12.3%; 2700 K
g A: 123%; 109%-110%; 5800 K
g B: 86.5%; 90.7%; 5300 K

Brightness (xSol)
g C: 19,000 times fainter than the Sun (disk barely visible at 1AU), flare star
g A: 152% to 160%
g B: 45% to 52%

g C: 10%
g A: NA
g B: NA

Comparison to Sol
g See illustration

Picture of star
g C: See picture
g A: See picture

Star system features
g Alpha Centauri A and B form a close binary separated on average by only about 23.7 AUs of an orbital semi-major axis (which is only slightly greater than the distance between Uranus and the Sun); the star swings between 11.4 and 36 AUs away in a highly elliptical orbit (e= 0.519) that takes 79.9 years to complete; Alpha Centauri C is located about 13,000 AUs fromA and B and takes 500,000 years to orbit that pair in hyperbolic orbit). Any planets within 2 AU of either Star A or Star B can retain a stable orbit.

Known planets
g C: Potentially a 0.8 Jupiter mass with an orbital period of between 1-2.7 years
g A: None found
g B: A small rocky world, which likely has a lava-like consistency, orbits 4 million miles (6.4 million kilometers) from star — much closer to its star than Mercury is to our sun — making its year only 3.2 days long. Planet has a mass of slightly more than Earth's. The world would be way too hot to support Earth-liked life.

Habitable zone
g C: 0.02 to 0.06 AU (orbital period of 2-16 days; tidally locked to a flare star). Probably too small of a star to host a habitable planet unless that planet has a stabilizing moon. Probability of a habitable planet is 1.07%.
g A: 1.2-1.3 AUs (midway between the orbits of Earth and Mars; 1.34 year orbit; as viewed from a hypothetical planet around either star, Alpha Centauri B’s brightness increases as the two approach and decreases as they receded; the variation in brightness is considered to be insignificant for life onEarth-type planets around either star; under optimal conditions, either Alpha Centauri A and B could hold four inner rocky planets at same distances as in Solar System; AB system may be 1.3 to 2.3 times as enriched in elements heavier than hydrogen than our Solar System; either A or B could have one or two “rocky” planets in orbital zones where liquid water is possible; B star would provide more light than the full Moon does on Earth as its brightest night sky object). Probability of a habitable planet is 5.4%.
g B: 0.73 to 0.74 AU (just beyond orbit of Venus; orbital period just less than an Earth year, however). Probability of a habitable planet is 5.7%.

Orbital map
g See map

View from star
If our own Sun, Sol, were viewed from the Alpha Centauri system, it would be located in Cassiopeia near the border with Perseus and about degrees north of a double cluster near the nebula IC 1805/1848, visible as a bright yellow star that would be almost as bright as Capella (Alpha Aurigae) appears in Earth's night sky
g C: The sky around faint Proxima Centauri is dominated by two stars: the yellow and orange dwarf stars that lie at the heart of the Alpha Centauri system. Just a fifth of a light year distant, they shine with a magnitude approaching -7, far brighter than Venus ever appears from Earth. See sky map.
g A: SAA; Seen from Alpha Centauri A or B, Proxima would be a 4.5 magnitude star.
g B: SAA

Nearby stars
(Star systems with 10 light years)
g Sol: 4.4 ly
g Barnard’s Star: 6.5 ly
g Ross 154: 8.1 ly
g Wolf 359: 8.3 ly

Map locating star system
g See stellar map

Location in Earth sky
Southeastern corner of Constellation Centaurus (cannot be viewed from middle northern latitudes of around 40 degrees)
g A: Not visible with naked eye

Other names
g C: Proxima Centauri, V645 Centauri, Gl 551, Hip 70890, LHS 49
g A: Rigil Kentaurus, Alp Cen A, Alf Cen A, HR 5459, Gl 559 A, Hip 71683, HD 128620, CP(D)-60 5483, SAO 252838, FK5 538, LHS 50
g B: Alp Cen B, Alf Cen B, HR 5460, Gliese 559 B, Hip 71681, HD 128621, LHS 51

Sci-fi mentions
g Episodes “Metamorphosis” and “Tomorrow is Yesterday” in “Star Trek: The Original Series”
g “Lost in Space”
g Robert Silverberg’s “Revolt on Alpha C”
g Leigh Brackett’s “Alpha Centauri — Or Die!”
g Mary Russell’s “The Sparrow”
g A.E. van Vogt’s “Far Centaurus”
g Charles Pelligrino’s “Flying to Vahalla”
g Planet Ecaz was Alpha Centauri B in “Dune”
g Wunderland is Alpha Centauri A in Larry Niven’s “Known Space” series
g Alpha Centauri A is home to planet Cassida, and Alpha Centauri B to Newton in Gordon R. Dickson's “Childe Cycle” (more commonly known as the "Dorsai series")
g Proxima is Alpha Centauri A in Robert Heinlein’s “Friday”
g Planet Tiber orbits Alpha Centauri A in Buzz Aldrin & John Barnes’ “Encounter with Tiber”
g Alpha (aka New Earth) orbits Alpha Centauri A in Isaac Asimov’s “Foundation” series
g Robotic probe is sent there in Jack McDevitt's short story "Windows"
g Among the first 26 interstellar expeditions is one to each of the stars in this trinary in Frederick Pohl's short story "Father of the Stars"
g Centauri system is destination of the Skipstone in Barry N. Malzberg and Bill Pronzini’s “Inaugural”
g Alpha and Beta are mentioned in Poul Anderson’s “Starfarers”; first robot spacecraft departs for it in about 10 years after publication of a theory about to practically travel near the speed of light
g Mentioned in "Star Trek: The Next Generation" episode "Elementary, Dear Data"
g Troxxt set up a base on a planet orbiting Proxima Centauri in William Tenn's short story "The Liberation of Earth"
g Ship "The Traveler" was intended to carry a load of colonists to Alpha Centauri in Poul Anderson's "Gypsy"
g Inhabited moon Pandora orbits the fictional gas giant Polyphemus in the Alpha Centauri system in science fiction movie "Avatar"
g The Garnishee inhabit the planet Dormite, which orbits the binary pair Lapha and Promixa Centauri in Harry Harrison's "Star Smashers of the Galaxy Rangers".
g A habitable planet orbiting Rigel Centaurus (Star A or Proxima Centauri) climatically is a cold world in Alfred Bester's short story "Fondly Fahrenheit".
g Character visits "Alpha Centauri IV" as a high school graduation present in Robert Silverberg's novel "The Man in the Maze". In same book, colonists live on Star B's sixth planet and Star B's eighth planet is a gas giant with a low density core and gravity only slightly greater than Earth's.
g Planet Hellespont orbits one of the system's stars in Chris Berman's novel "Ace of Aces"
g Mentioned in Vylar Kaftan's short story "I'm Alive, I Love You, I'll See You in Reno."

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Thursday, June 28, 2007

Welcome to Our Stellar Neighborhood

Our Stellar Neighborhood is an ongoing project aimed at providing accurate and useful information to science fiction writers about stars in the Local Bubble. It also can be used by scientists and astronomy buffs, though the data isn't always the most relevant for them.

The site arranges the stars in order of distance from Earth. Of course, there is some controversy and uncertainty to some of those stars' actual distances, so most of the light year measurements given are simply averages.

Each star entry contains the following information, when available (note that this is a work in progress):
g Star type - The spectral type given follows the Harvard spectral classification system and when known adds the Yerkes spectral classification.
g Distance from Earth - Measurements are in light years.
g Star Service number - This is an irrelevant entry to everyone except me; the number identifies the star system in my Star Service science fiction series.
g Age - This gives the estimated age of the star, relevant for determining habitability. The younger the star, the less likely that Earth-like life has evolved; the older the star, the greater the chance that Earth-like life has vanished, particularly if it's a red giant or white dwarf. Indeed, though our own sun has a good 5-7 billion years left of existence, in another 500 million years when it brightens, the Earth may become uninhabitable as the oceans boil off.
g Diameter/Mass/Temperature - This data will help determine circumstellar habitable zones for Earth-like planets. When the star is more massive and hotter than the sun, the habitable zone is farther out than in our solar system. When it's smaller and cooler, the habitable zone is closer to the star. The measurements typically are given as a percentage of our sun, with Sol equalling 100%; therefore, 50% means the star is half as massive as the sun while 150% means it's 50% more massive.
g Brightness - A star's luminosity also will help determine circumstellar habitable zones for Earth-like planets. The brigher the star, the farther out the habitable zone must be for a planet to receive the degree of light that Earth does from the sun; the dimmer the star, the closer in the planet must be. The measurements typically are given as a percentage of our sun, with Sol equalling 100%.
g Metallicity - This refers to the proportion of a star's matter made up of chemical elements other than hydrogen and helium. Metallicity also can determine if an Earth-like planet might exist in that star system. The measurements typically are given as a percentage of our sun, with Sol equalling 100%. The closer the percentage to the sun's metallicity, the better the chance that terrestrial planets will exist. If the metallicity is greater than the sun's, that's always good for the formation of terrestrial planets.
g Comparison to Sol - These are links to graphics showing the relative sizes and colors of the star and our sun.
g Picture of star - These are links to photographs of the star. When copyrights allow, I'll post a picture of the star on its page's upper right corner.
g Star system features - This data provides interesting facts about the star system that might be mentioned in a story to increase its verismilitude.
g Known planets - This lists any exoworlds that we've definitely discovered or that our current research predicts should exist in the star system.
g Habitable zone - My favorite section! It lists, when known, the distance from the star (generally in AUs) that an Earth-like planet could exist. It also provides any information about what that planet might be like. The tag "habitable" appears for stars that are excellent candidates for circumstellar habitable zones for Earth-like planets.
g Orbital map - These are links to graphics visually showing how a known exoworld orbits the star or giving the star system's circumstellar habitable zones for Earth-like planets.
g View from the star - These are links to graphics showing how stars would appear in the night sky of a planet orbiting the star.
g Nearby stars - This lists all stars within 10 light years of this star. If the neighboring star is habitable (generally G-, F- or K-type), that information is given. Sometimes neighboring stars farther than 10 light years are listed, especially if the page's star is "geographically" at the center of several potentially habitable systems.
g Map locating star system - These are links to star maps that look down upon the galactic plane, typically with Sol at the map's center.
g Location in Earth sky - This describes where the star appears in our night sky. Not all of the stars are visible with the naked eye or even an amatuer telescope, but their location still is provided; usually a note is given indicating it's not visible with the naked eye.
g Other names - Unfortunately, the number of competing star catalogues means many stars have more than one name. Generally the popular name for the star is listed as its page name with other names listed in this section. All of these names come from actual star catalogues used by astronomers.
g Sci-fi mentions - Many of these stars appear in science fiction novels, short stories, movies, television shows and video games. Knowing how other authors have represented the star in fiction sometimes is useful and certainly entertaining. Warning: The lists in this section are far from complete.

Of course, this site contains a geocentric bias - it focuses on data that would point toward Earth-like planets containing Earth-like lifeforms. Other habitable zones almost certainly exist, particularly the moons around gas giants. In addition, alien life probably is far more different that ours and I'd bet has evolved in all kinds of solar and planetary environments so that their geocentric definition of a habitable zone wouldn't allow for us on Earth to exist. But science fiction stories involving space travel often are about places that humans can colonize or at least take off their spacesuits to interact with similar carbon-based, oxygen-breathing aliens, hence this site's focus.

A couple of other useful references I offer for science fiction writers are two online sites. Alien Life is a blog that provides the latest news and speculations in astrobiology. Inventing Reality is about writing science fiction.

Should you find errors on this site or have additional information that would be useful, please contact me.

This sight is dedicated to my son Kieran, who as a toddler never failed to point out to me the moon and the stars when they were out.

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