# CatalogNames

Description:
Astrographic Catalogue, see van Biesbroeck (1963)


Description:
New General Catalogue of Double Stars within 120 degrees of the North Pole, Aitken (1932)


Description:
Catalogue of Reference Stars for the AGK3, Smith (1980)


LongName:
Don C. Barry, "Chromospheric Age Dependence of…", APJ 334

Description:
"The Chromospheric Age Dependence of the Birthrate, Composition, Motions, and Rotation of Late F and G Dwarfs within 25 Parsecs of the Sun", Don C. Barry, The Astrophysical Journal, 334: 436-438, 1988 November 1


Description:
Bonner Durchmusterung, Schonfeld (1886), Argelander (1903)


Description:
Bruce Proper Motion Survey, Luyten (1963)


Description:
Photometric results of special search for interlopers.  APJ,142-1,412,1965.
PHOTOMETRIC RESULTS OF SPECIAL SEARCH FOR INTERLOPERS. APJ,142-1,412,1965.


LongName:
Catalogue of Components of Double and Multiple stars


Description:
Cordoba Durchmusterung, Thome (1892, 1894, 1900, 1914); Perrine (1932)


Description:
Catalogue of 20554 Faint Stars in the Cape Astrographic Zone -40 to -52 for the Equinox of 1900.0, Jones & Jackson (1939)


LongName:
Center for High Angular Resolution Astronomy


Description:
Cape Photographic Durchmusterung, Gill (1903)


LongName:
B. Edvardsson et al., "Chemical Evolution of the Galactic Disc", A&AP 275

Description:
"The Chemical Evolution of the Galactic Disc", B. Edvardsson, J. Andersen, B. Gustafsson, D.L. Lambert, P.E. Nissen, and J. Tomkin, Astronomy and Astrophysics, 275, 101-152 (1993)


Description:
Fourth Fundamental Catalogue, Fricke et al. (1963)


Description:
Preliminary Supplement to FK4, Fricke (1963)


Description:
Fifth Fundamental Catalogue, Fricke et al. (1988)


Description:
The FK5 extension. New Fundamental Stars, Fricke et al. (1991)


LongName:
Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)

Description:
Catalogue of Apparent Diameters and Absolute Radii of Stars, 2nd Edition, Fracassini M., Pasinetti-Fracassini L.E., Pastori L., Pironi R. <Bull. Inf. CDS 35, 121 (1988)>


Description:
Lowell Proper Motion Survey, Giclas et al. (1959-78)


Description:
General Catalogue of 33342 Stars for the Epoch 1950, Boss et al. (1937)


LongName:
General Catalog of Trigonometric Parallaxes


Description:
H.L.Giclas, R.Burnham, N.G.Thomas, A Proper Motion Survey in the Hyades, bull. Lowell Obs., No.118, 1962


Description:
Extension to the Catalogue of Nearby Stars, Gliese & Jahreiss (1979)


Description:
3rd ("Preliminary") edition of the catalog of nearby stars by Gliese et al. (1991)


Description:
Guide Star Catalog of the Space Telescope Science Institute, Lasker et al. (1990)


LongName:
Hatzes and Cochran, Astrophysical Journal vol. 413 (1993)


Description:
Henry Draper Catalogue, Cannon & Pickering (1918-49)


Description:
Henry Draper Extensions, Cannon (1925-36), Cannon & Walton Mayall (1949)


Description:
Henry, Kirkpatrick, Simons.  The Solar Neighborhood.  I. Standard Spectral Types (K5-M8) for Northern Dwarfs Within Eight Parsecs.  Astronomical Journal, vol. 108, no. 4 (Oct 1994), pp. 1437-1444


Description:
Hipparcos Input Catalogue, ESA-SP1136 (1992) - used by the HIPPARCOS mission satellite


Description:
Catalog of all stars surveyed by the HIPPARCOS mission satellite, which was designed to accurately measure stellar parallaxes.


Description:
M.L.Humason, F.Zwicky. A Search for Faint Blue Stars. APJ, 105-1, 85, 1947


Description:
International Reference Stars, comprises AGK3R and SRS Catalogues


LongName:
Proximity Zero, 2nd Edition, by Terry Kepner


Description:
W.J.Luyten. Catalogue of 832 Double Stars with Common Proper Motion in the Southern Hemisphere. Publ. Minnesota Obs. 3-3,33,1941.


Description:
Luyten catalogue of 1849 stars with proper motions Exceeding 0''.5 annually


Description:
Luyten Half-Second Catalogue, Luyten (1979)


Description:
Luyten Palomar Catalogue (proper motion survey with the 48-inch Schmidt) Luyten (1963-87)


Description:
Luyten Two-Tenth Catalogue, Luyten (1957) (see also NLTT)


Description:
J.R. Mould, Astrophysical Journal vol. 226 (1978), p. 923


Description:
New Catalogue of Suspected Variable Stars, Kholopov ed. (1982)


LongName:
Catalogue of Positions and Proper Motions


Description:
Smithsonian Astrophysical Observatory Star Catalogue (1966)


Description:
Southern Reference System Catalogue, Smith et al. (1990)


Description:
A Catalgue of [Fe/H] Determinations, 1991 ed., by Strobel, Hauck, Francois, Thevenin, Friel, Mermilliod, and Borde.


LongName:
VLT Interferometer, ESO Paranal Observatory


Description:
Catalogue of White Dwarfs, McCook & Sion (1977)


Description:
Washington Catalog of Visual Double Stars 1984.0, Worley & Douglass (1984)


Description:
Catalogue of Stars within 25pc of the Sun, Woolley et al. (1970)


LongName:
4th Catalog of Orbits of visual Binaries


Description:
Yale Photographic Catalogues, Trans. Astron. Obs. Yale University, Vols 3-32 (1926-83)


# Orbits

Source:
Korzennik, Brown, Fischer, Nisenson, Noyes


Source:
Scholz, McCaughrean, Lodieu, and Kuhlbrodt (2003)


# Planets

MassSource:
Korzennik, Brown, Fischer, Nisenson, Noyes


# Systems

PointsOfInterest:
The "8" in the Detected Planets entry is not an error.  Pluto is not a "planet," but a huge, close-orbiting, low-eccentricity Kuiper Belt object.  With a big moon.  Of course, some die-hards out there still insist that it really is a planet, more for sentimental reasons than anything else.  They're welcome to live in their little fantasy world.  Neener neener.


PointsOfInterest:
Although the third brightest star in the system can be called "Alpha Centauri C," as per the usual naming convention, it is usually referred to as Proxima Centauri, since the dimmest star of this triplet happens to be THE closest star to our own sun.  Proxima is a flare star; its flares about double the star's brightness, occurring sporadically from hour to hour.  In fact, at any given moment, more than one flare may be operating.  This varying brightness gave it the name "V645 Centauri" among variable star enthusiasts.  Unfortunately, such flares are lethal to any life that might otherwise arise on planets in its comfort zone (if Proxima has any).

     Life on planets orbiting Alpha Centauri A or B, however, is almost as likely as life in our own star system.  Since the smallest gap between A and B is 11.3 Astronomical Units, any planets closer to A or B than one-quarter of this distance (2.9 A.U.s) would be in stable orbits.  Furthermore, 2.9 A.U.s is wider than the comfort zone of either of these stars, so any planets in the comfort zones of A or B would also be within the stable orbit region.  These stars are young enough to have developed when the galaxy was rich with life-supporting and solid-planet-supporting heavy elements, yet old enough for any life there to have evolved into complex forms.

     Both Don C. Barry, and B. Edvardsson et al., estimated the age of this star system at 4.2 thousand-million years.  The earliest estimate of this system's age, by Flannery & Ayres in the 1-April-1978 Astrophysical Journal, however, was 6 thousand-million years, which is closer to the most recent estimate.


PointsOfInterest:
Besides moving across the terrestrial sky faster than any other star (almost a third of a degree of arc per century!), Barnard's Star, we are certain, has planets.  Although we have never actually seen these planets, wobbles in Barnard's Star's course indicate that it has two invisible companions, one with a mass of 0.7 times that of Jupiter (0.0007 x Sol) orbiting it at 3 Astronomical Units, and one with a mass of 1.15 times that of Jupiter (0.0015 x Sol) orbiting it at 5 A.U.s with an orbital period of 24 years.  However, since this is an old Population II star which formed before the galaxy became enriched with heavy elements, these planets are going to be carbon and metal poor, probably little more than heavy balls of hydrogen and helium.  (One catalog even states that, despite its velocity’s moderate z-component, Barnard's Star actually belongs to the *very* old galactic halo population.)

     The British Interplanetary Society once proposed Project Daedalus, a mission to send an unmanned spacecraft to Barnard's Star using a deuterium/helium-3 nuclear fusion reaction to provide thrust.  Such a mission would require both a larger spacecraft-construction infrastructure, and better hot-fusion technology, than are currently available.


PointsOfInterest:
Besides its proximity to our own sun, this tiny star is one of the least luminous known, even though astronomers suspect that such intrinsically faint stars are probably very common in space.  Alpha Centauri Proxima is another super-dim star of this ilk; and, like Proxima Centauri, Wolf 359 is now known to be a flare star (hence the CN Leonis variable star designation). Wolf 359's flare outbursts are rarer and not as violent as those of Proxima Centauri or UV Ceti.

MetallicityComment:
Galactic plane population (about the same as Sol)


PointsOfInterest:
The z-component of Lalande 21185's velocity suggests that it's from the galactic halo population; however, J.R. Mould's spectral analysis (printed in vol. 226, page 923 of the Astrophysical Journal (1978)) says that the ratio of iron to hydrogen in the star is a whopping 60% of our sun's iron-to-hydrogen ratio, which is awfully iron-rich for a halo population star.  The presence of emission lines in the star's spectrum would support the idea that this is a decently heavy-element-rich star as well.

     Wobbles in Lalande 21185's position were once thought to indicate an unseen object orbiting it, but subsequent analysis showed that no such wobbles were occurring.


PointsOfInterest:
While Sirius A is known for being the brightest star in the sky, Sirius B was the first White Dwarf to be discovered by humankind (that it took almost a century from the discovery of Sirius B to the acceptance of its White Dwarfness notwithstanding).  Sirius B's calculated average density is 92 000 times that of the sun; one cubic inch of material at that density would weigh over two tons at the surface of the Earth.  Electron-degeneracy theory predicts that below the surface layers, Sirius B has a uniform density and temperature throughout; however, the outer gaseous layers are probably not electron-degenerate, and thus would not be nearly as dense as the two-tons-to-the-cubic-inch figure previously quoted.  (For more information about white dwarfs, see the Lightweight Stars.)

     Sirius A is a young star.  It has to be; class A main sequence stars exhaust the nuclear fuel in their cores within 1000 million years and turn into red giants or Cepheid variables thereafter.  Thus, if there are any life-bearing planets orbiting Sirius A, any life on them will be primitive (it took about 1500 million years for the first oxygen-producing life to develop on Earth, and over twice that long for multicellular organisms to arise).

     Due to slight perturbations in the orbit of Sirius B, an additional, unseen companion to either Sirius A or Sirius B is suspected.


PointsOfInterest:
Properly, only the less bright star in this system (Luyten 726-8 B) bears the name UV Ceti, since it is a variable star — the UV indicates that this was the 35th variable star discovered in the constellation Cetus.  It is an extreme flare star; in less than a minute, it can quintuple its total brightness, afterwhich it will fall back down to normal brightness levels within two or three minutes; and then flare suddenly again after several hours.  In 1952, UV Ceti was observed flaring to 75 times its normal brightness in only 20 seconds!

     If van de Kamp's orbital data are to be believed, these two stars would have to be exceedingly small and light -- their masses would be only 0.044 x Sol for the "A" star and 0.035 x Sol for UV Ceti.  This would mean that, although each of these stars is brighter than Wolf 359, Wolf 359 would have a higher mass than both of these stars combined.  However, if we assume that Worley & Behall's orbital data are the more accurate, the two stars' total mass would be 0.23 x Sol, which is more in keeping with the measurements of both their luminosities and their diameters.


PointsOfInterest:
This star, or the primary (A) star of this close-orbiting pair if this star turns out to be a spectroscopic binary, is a slightly (but rapidly) variable star of the "Delta Scuti" class, pulsating over a period of 2.503 hours. Its total light output varies only by a factor of about 4% over the course of this pulsation, though.


PointsOfInterest:
B. Edvardsson et al. measured a metallicity of about 110% of Sol for this star, from an iron-to-hydrogen ratio of over 120% the Solar value. They also deduced an age of only 2900 million years, but indicated that this age may have been underestimated by as much as 1200 million years.


PointsOfInterest:
B. Edvardsson et al. measured a metallicity of about 110% of Sol for this star, based on an iron-to-hydrogen ratio of 95% the Solar value. But even this lower metallicity value seems high, considering that both Edvardsson and Barry measured an age close to 8 thousand-million years.


PointsOfInterest:
On June 29, 1999, Kürster et al. announced the discovery of a 2.26+ Jupiter-mass planet (now named Iota Horologii b) in an Earthlike orbit around this star, with an orbital period of 320 days and an eccentricity of 0.16.


PointsOfInterest:
The Wikipedia article on this star lists its diameter as 1.08 x Sol, smaller than listed in the Fracassini catalog.


PointsOfInterest:
This star and Zeta(2) Reticuli may actually form a binary system.  If so, the two stars are at least 5500 A.U. apart in space, which would give them a very very long orbital period.


PointsOfInterest:
This star and Zeta(1) Reticuli may actually form a binary system.  If so, the two stars are at least 5500 A.U. apart in space, which would give them a very very long orbital period.

     B. Edvardsson et al. arrived at a metallicity of 55% of Sol for this star, based on their measured iron-to-hydrogen ratio of 59% of the Solar value.


PointsOfInterest:
In addition to the Jupiter-mass planet discovered around this star on August 7, 2000 at the University of Texas MacDonald Observatory, tiny wobbles in the position of Epsilon Eridani also suggest that a second invisible companion is orbiting this star farther out.  Such a companion would be 1.07 light-hours (7.7 AUs) away, orbit the main star once every 25 years, and have a mass less than 0.05 x Sol.  It is debatable whether this object would be a brown dwarf or a star too dim to be seen from an Earth-based telescope.

     Asymmetric, primordial dust rings made up of 1-millimeter-size particles extend 60 AUs from this star.  The irregular shape of this ring may be due to yet another undiscovered planet orbiting just inside the ring, at 30 AUs.

     As of the late 1990s, this is officially the star about which Babylon 5 orbits.


PointsOfInterest:
B. Edvardsson et al. calculated a heavy element abundance of 63% of Sol for this star, based on their measurement of an iron-to-hydrogen ratio of 78% of the Solar value. Don C. Barry lists an age of 8400 million years.


AgeComment:
probably erroneous; would be older than the universe!


PointsOfInterest:
B. Edvardsson et al. calculated a highly questionable age of over 15 thousand-million years for this star. Barry's figure is more likely to be accurate.


PointsOfInterest:
The Gliese catalog lists this star as being about 55 light-years away, assuming that it is a main-sequence star.  This would give it an intrinsic visual luminosity of only about 0.1 x Sol, which would actually be on the dim side for a main-sequence K0.


PointsOfInterest:
B. Edvardsson et al. calculated a heavy element abundance of 102% of Sol for this star, based on their measurement of an iron-to-hydrogen ratio of 93% of the Solar value.


PointsOfInterest:
This star is surrounded by a 1500-A.U. disc of gas and dust.  In January 1998, the Hubble Space Telescope resolved the shapes of two bulges in this disc which almost certainly indicate the presence of either planets or brown dwarfs.


PointsOfInterest:
In late 1995, the existence of an extremely dim, cool companion (luminosity no higher than 0.000006 x Sol, surface temperature less than 1200 K) was confirmed by several joint observations.  This companion, dubbed Gliese 229B, is most likely a brown dwarf: a star-like object too small to sustain nuclear fusion reactions in its core.  Its mass is 20-50 times that of Jupiter (0.03-0.07 x Sol), although close-up Hubble Space Telescope photographs show a disc that would give it only about the same diameter as Jupiter.  Its orbital period is so long that no accurate measurements of the shape of its orbit have yet been made; at last sighting, it was 44 A.U.s away from the main star.  Theoretically, a solid planet orbiting Gliese 229B at a very short distance (300 000 km) would receive as much energy from it as the Earth does from our own sun; however, brown dwarfs cool off with age, and so such a planet wouldn’t remain warm for very long.

     Since the main star itself is a flare star, it is probably incapable of harboring planets with surface life as we know it.


AgeComment:
awfully old for such a high heavy element abundance


AgeComment:
which sounds too old for an F6 main sequence star


PointsOfInterest:
This star is some kind of rotating variable.


ArityComment:
singular (an unseen companion is suspected)


PointsOfInterest:
Duquennoy and Mayor have studied this spectroscopic-binary system using the same techniques currently used to search for extrasolar planets.  They measure a minimum mass of 54 x Jupiter (about 0.05 x Sol) for the B component.


PointsOfInterest:
In 1999, Korzennik, Brown, Fischer, Nisenson, and Noyes discovered an invisible companion orbiting this star. This companion has a mass at least 7.2 times that of Jupiter, and orbits with a semimajor axis of 0.88 A.U.s, an eccentricity of 0.7, and a period of 256 days.


PointsOfInterest:
This star has at least one planet, discovered some time in late 1995 or early 1996.  The planet has at least 2.4 times the mass of Jupiter and follows an almost-circular path around the star at a distance of 315 million kilometers (2.1 AU) with an orbital period of 1082 days (2.98 years).  Assuming it was as reflective as Jupiter is, this planet would have an effective temperature of about 180 K (-135 degrees Fahrenheit).

     The star itself has a rotation period of 16 days.


MetallicityComment:
Galactic halo population (less than 10% of Sol)


PointsOfInterest:
In early 2004, the Harvard-Smithsonian Center for Astrophysics discovered that the internal structure of this white dwarf is a carbon-oxygen crystal resembling a diamond in structure.


PointsOfInterest:
B. Edvardsson et al. derived a ripe old age of over 13 thousand-million years for this star, which is probably too old, considering that an average G0 star can only remain on the main sequence for about 10 thousand-million years.


AgeComment:
probably incorrect, as this is much too old for such a high heavy-element abundance


PointsOfInterest:
This star may be in a long, wide orbit about Mizar. Mizar and Alcor have very similar proper motions, and the best distance data available today (from the Hipparcos mission) indicate that the two are separated by only about 3 light-years in space, and may actually be much closer together.


PointsOfInterest:
This star has at least one planet, discovered in late December 1995.  The planet has at least 6.6 times the mass of Jupiter and follows a rather eccentric elliptical orbit with a periastron distance of 0.26 AU, and apastron distance of 0.60 AU, and a period of 116.7 days.  With such a highly eccentric orbit and such a high mass, it may actually qualify as a small brown dwarf.  Its average surface temperature would be about 358 K (185 degrees Fahrenheit), assuming (a) it was about as reflective to starlight as Jupiter is, and (b) it wasn’t producing any of its own energy internally by gravitationally collapsing.


PointsOfInterest:
Arcturus is a classic example of a Red Giant; a light- to middle-weight star that has passed the end of its main sequence lifetime and is in a transitional period of bloating up and cooling off. The total amount of time a star can remain in the red giant stage is on the order of a couple million years, which is not nearly enough time for life as we know it to engage in any serious evolution (if Arcturus has any life-bearing planets at all).


PointsOfInterest:
B. Edvardsson et al. give an age of over 13 thousand-million years for this star, which is probably too old; an F9 star can only remain on the main sequence for about 9-10 thousand-million years.


PointsOfInterest:
Due to its closeness in apparent position, and early rough measurements of their parallaxes, this star was once believed to be gravitationally bound to the Wolf 630 system; however, given even the greatest possible error in the modern measurement of their parallaxes, Wolf 629 has to be at least one light-year away from Wolf 630 and is probably over 2 light-years away.

     Despite its velocity’s low z-component, this star is a subdwarf (luminosity class VI), indicating it probably has a low level of heavy elements (and thus would’ve come from the old population of the thick galactic disk or galactic halo).

AgeComment:
probably old (around 10 000 million years)


PointsOfInterest:
Delta Herculis has a class G dwarf companion about 8 arc-seconds to the north, but this companion is not gravitationally bound with it.


PointsOfInterest:
B. Edvardsson et al. list an age of over 17 thousand-million years for this star, which cannot be true — it would make this star older than our current estimates for the age of the universe!


PointsOfInterest:
B. Edvardsson et al. give a venerable age of over 15 thousand-million years for this star, which is questionable since G2 stars are only supposed to remain on the main sequence for about 12 thousand-million years.


PointsOfInterest:
Given this star's radial velocity and small proper motion, it will probably pass within one light-year of our Solar system in about a million years or so.


AgeComment:
inconsistent with such a high heavy-element abundance


PointsOfInterest:
This star is one of the fastest rotating stars known, completing an entire rotation in only 6½ hours (our own sun takes 25 days to rotate once, and isn't as big around). According to Gerard T. Van Belle and collaborators using the Palomar Testbed Interferometer, this spin causes Altair to be 11-17% bigger across at its equator than from pole-to-pole, and to be shaped like a flattened ellipsoid or "oblate spheroid."


PointsOfInterest:
As flare stars go, AX Microscopii is pretty mild, emitting flares less than once per day.  This, combined with the high eccentricity and inclination of its orbit around the galactic center, implies that the star is older than our own Sun.


PointsOfInterest:
The two brown dwarf companions to this star both belong to spectral class T.  The pair orbit each other at least two A.U.s apart, and have an observed separation from Epsilon Indi A of about 7 arcminutes (putting the pair at least 1500 A.U.s away from the star.)

    Epsilon Indi Ba has a surface temperature of roughly 1500° Celsius, and an intrinsic luminosity just 0.002% that of the Sun.


PointsOfInterest:
This is the first sunlike star outside of our own solar system around which a planet was actually detected. On the 6th of October 1995, Michel Mayor and Didier Queloz of the Geneva Observatory in Switzerland detected a regular variation in the doppler-shift of the light coming off 51 Pegasi, indicating a closely orbiting companion. One week later, Geoffrey Marcy and Paul Butler confirmed it at Lick Observatory. The planet (unofficially dubbed Bellerophon by Marcy) has at most half the mass of Jupiter, and follows a nearly-perfect circular orbit at a distance of 8 million kilometers (0.05 AU) with a period of 4.2293 days. Being so close to the star would give the planet a surface temperature of over 1100 K if it is rotating (which it almost certainly is).


PointsOfInterest:
Tokovinin et al. have studied this spectroscopic-binary system using the same techniques currently used to search for extrasolar planets.  They measure a minimum mass of 60 x Jupiter (about 0.06 x Sol) for the B component.


PointsOfInterest:
This star may be orbiting the Gliese 897 system.


PointsOfInterest:
According to Freming et al. in 1988, this star is an X-ray source, and as such would probably not be amenable to life as we know it on planets orbiting it.


PointsOfInterest:
B. Edvardsson et al. derived an age of about 4.4 thousand-million years for this star.


PointsOfInterest:
The naming of the components of this star is a bit unusual, with A and C forming the close-orbiting pair and B orbiting the two of them at a greater distance. This is because the third (C) star is so close to the first (A) star that it wasn’t resolved until after the other two components had been catalogued and named.


PointsOfInterest:
Either the luminosity data or the orbital data for this star are in error.  According to the semimajor axis and the orbital period, these stars should have a total mass of 0.62 x Sol combined.  However, their luminosities indicate that 0.62 solar masses should be the mass of just the A star by itself, which would also be consistent with what one would expect as the mass of an early class K main-sequence star.


PointsOfInterest:
Very recently, Hubble Space Telescope observations have detected a low-mass companion to the A star. The short semimajor axis listed does not seem reasonable in light of a 60 year orbital period, and is probably based on a dubious observation.


PointsOfInterest:
Duquennoy and Mayor have studied the C pair in this system using the same techniques currently used to search for extrasolar planets.  They measure a minimum mass of 39 x Jupiter (about 0.04 x Sol) for the Cb component.


PointsOfInterest:
Mayor, Queloz, Udry, and Halbwachs have studied the A pair in this system using the same techniques currently used to search for extrasolar planets.  They measure a minimum mass of 50 x Jupiter (about 0.05 x Sol) for the Ab component.


PointsOfInterest:
The dimmer pair of this four-star star system is usually referred to as “Capella H”, because the C, D, E, F, and G letter designations were wasted on nearby stars that looked like they might be gravitationally bound to Capella A or B but in fact were not.

     Note that the comfort zones for either of Capella A or B are farther out than the orbital distance between these two stars.  However, a planet could orbit the Capella A-B pair far enough out for the two stars to act as a single gravitational source and near enough for it to receive enough energy to sustain life.


PointsOfInterest:
The A star, and most likely the B star also, is a flare star.


ArityComment:
The A star is a possible spectroscopic binary


AgeComment:
which sounds too old for an F9 main-sequence star.


PointsOfInterest:
Like Sirius, Procyon is a doublet consisting of a regular main-sequence star and a white dwarf.  Unlike Sirius, Procyon A is unusually bright for its color and may be a subgiant.  Procyon B's average density is estimated at over two tons to the cubic inch, making it denser than Sirius B.


ArityComment:
the A star is itself a possible spectroscopic binary


PointsOfInterest:
The A star has at least one planet.  The planet's mass is at least 0.8 times that of Jupiter, with a diameter anywhere from 0.35 to 1.35 times that of Jupiter -- all perfectly good values for a gas-giant planet.  Its orbit is nearly circular, too, indicating that this probably isn't a brown dwarf.  However, like the planet orbiting 51 Pegasi, 55 Cancri A's planet orbits very close to the star, at a distance of only 0.11 A.U.s (thus completing one orbit every 14.76 days).


ArityComment:
trinary, but the A star is a possible spectroscop


ArityComment:
the A star is a possible spectroscopic binary


PointsOfInterest:
The Hipparcos catalog lists a parallax of 8.48 +/- 0.73 milliarcseconds for this system, which would put it between 350 and 420 light-years away.  This is at odds with the data in the Gliese catalog, which puts this system much closer.


PointsOfInterest:
Mayor, Queloz, Udry, and Halbwachs have studied the B pair in this system using the same techniques currently used to search for extrasolar planets.  They measure a minimum mass of 37 x Jupiter (about 0.04 x Sol) for the Bb component.


PointsOfInterest:
There is a thick disk of dust around one or both of these pairs of stars, due to their extremely young age.  It is probably a region of planet formation.


ArityComment:
the B star is a possible spectroscopic binary


PointsOfInterest:
The B star of this system was discovered only after 1980, and as such little information is available about it.  Unless it was captured by the A star's gravity while passing near it (which is highly unlikely), the B star formed at the same time out of the same material as the A star and would be just as heavy-element-deficient.
      Worse, according to a 1984 article in the Publications of the Astronomical Society of the Pacific (96:557-558, July 1984; by W. D. Heintz), there is no trace of a second star in this system and the apparent "flare star" activity seen in 1980 may have been superflares occurring on the A star.


AgeComment:
Barry gives an age of 3500 million years for the A star, but 2100 million years for the B star.


PointsOfInterest:
Despite the "A" designation in the LDS and GJ catalog numbers, this is a singular star. Component "B" does not exist.


PointsOfInterest:
The gaps between the two A stars and their orbital period have both been accurately measured. However, only the orbital period of the two B stars, and the gap between the A and the B star, are reliable numbers. The Ba-Bb gaps and the A-B period are probably in error. If these numbers are to be believed, they indicate that the two B stars have a total mass of over 130 suns, and the whole system of four stars have a total mass in excess of 13 000 x Sol!


ArityComment:
The C star may not be an actual member of the sys


PointsOfInterest:
This system is now recognized as being gravitationally bound to Struve 1999, which lies 4.7 arc-minutes to the south in Earth's sky.  The projected separation of these two systems in space would be about 8000 A.U.s.


PointsOfInterest:
This system is now recognized as being gravitationally bound to Xi Scorpii, which lies 4.7 arc-minutes to the north in Earth's sky.  The projected separation of these two systems in space would be about 8000 A.U.s.


ArityComment:
Both components are possible spectroscopic binari


PointsOfInterest:
Wolf 629 was once believed to be gravitationally bound to this trio; however, even given the greatest possible error in measuring their parallaxes, Wolf 629 has to be at least one light-year away from Wolf 630 and is almost certainly farther away than that.


PointsOfInterest:
If orbital data have been interpreted accurately, the suspected third member of this system should have a mass of only about 0.01 x Sol, or about 10 times the mass of Jupiter, which would not be quite massive enough to ignite as a star -- it would be a brown dwarf.

ArityComment:
there is partial evidence for a third unseen member


AgeComment:
Barry gives the age for the B star as 10200 million years.


PointsOfInterest:
There seems to be a short-period variation in the A star's radial velocity. Hence, it's probably a close-orbiting binary pair as shown. The "diameter" figure listed would thus be the computed diameter of a single star as bright as both components of this close-orbiting binary combined.


PointsOfInterest:
The orbit calculated by Wilson is the more likely of the two. It gives a combined mass of about 0.6 solar masses for both stars, for an average of 0.3 solar masses each -- an eminently reasonable value for M4.5 dwarfs. The Mourao orbit suggests a rather ludicrous combined mass of over 6 solar masses.


PointsOfInterest:
Small systematic variations in the way these two stars orbit one another suggest that there is a third, unseen body orbiting 61 Cygni A, with a mass 8 times that of Jupiter (0.008 x Sol).  Its orbital period is 4.8 years, which would give it an average orbital distance of 2.4 A.U.s.  Despite its low mass, which is much too low for a star and is even on the low side for a brown dwarf, this third member has been dubbed "61 Cygni C."  Theoretical calculations suggest that its diameter is less than 0.1 x Sol.


ArityComment:
Both the A and B stars are possible spectroscopic binaries


PointsOfInterest:
The B star has not been seen since 1933.


PointsOfInterest:
At least one of this pair is a possible flare star.


PointsOfInterest:
This binary pair may in turn be orbiting Gliese 898.


PointsOfInterest:
Algol A and B are close enough together to be a mass-exchange binary, where one star deposits material onto the other.  Algol A probably used to be less massive, while Algol B probably used to be more massive.  Probably, Algol B swelled up into its red giant phase at the end of its main-sequence lifetime, and in the process its surface got close enough to Algol A for Algol A's gravity to pull material off of it.


PointsOfInterest:
The figure listed for diameter is the star's diameter from pole-to-pole.  Measurements at the VLT Interferometer at the Paranal Observatory have shown the star to be 50-60% bigger across at its equator.  The star is shaped like a flattened ellipsoid due to very rapid rotation.


PointsOfInterest:
Canopus has been used for navigation on several interplanetary spacecraft missions.

     The HIPPARCOS mission obtained a distance of 313 light-years to Canopus, with a standard error of 4.8%.  If accurate, this would make its diameter approximately 60 x Sol, and its luminosity about 15 800 x Sol.


PointsOfInterest:
The A star is actually egg-shaped, and is only about two-thirds as tall as it is wide.  The "diameter" listed below is measured across its widest chord.
     Both stars are enveloped in a reddish nebula some 5 light-years in diameter, probably composed of metallic dust.


PointsOfInterest:
In 1994, Polaris A's variability disappeared altogether, only to return again in 1995. An unseen companion is suspected to be orbiting close to Polaris A (hence its designation as a close-orbiting binary pair below), with a period of 30.5 years, a semi-major axis of 3.1 A.U.s, and an eccentricity of 0.64, giving it a periastron gap about 5 times narrower than its apastron gap. This unseen companion would have to be at least 6 magnitudes dimmer than Polaris A. Periastron for the unseen companion happened in 1928.


PointsOfInterest:
The diameter listed below is only the average diameter for this star. Its actual diameter varies from 550 to 920 times Sol. This may be indicative of instabilities within the star which could turn it into a supernova at any time.


AgeComment:
Extremely young (Rigel A is either pre-main-sequence or post-main-sequence)


PointsOfInterest:
Deneb may be in the process of expanding from a class A main-sequence star to a red giant. Theoretically, this process should take only about 20 000 years, at a rate of about 0.3°C per year, for a massive star like Deneb. Hence, Deneb is under close scrutiny for any long-term changes in its spectrum or color temperature.


PointsOfInterest:
Epsilon Aurigae is an "eclipsing" binary star, where each star passes in front of the other at opposite points in their orbits. The B star, if it is a star at all, is so dim that no change in light output is measured when the A star passes in front of it and no "eclipse" is recorded. When the B star passes in front of the A star, the star's light output is significantly diminished, but some of the light from the A star can still be seen; it seems that the B star is partially transparent. The last eclipse began on July 22, 1982 and ended on June 25, 1984.


PointsOfInterest:
No anthology of popular science-fiction stars would be complete without the first suspected black hole to be discovered.  The name Cygnus X-1 properly only refers to the B star of this pair, as it's the X-ray source.  The "diameter" of Cygnus X-1 reported below is actually twice its Schwarzchild Radius, the distance from the center of a black hole at which its escape velocity equals the speed of light (also called the Event Horizon).

     The less interesting A star is a rotating ellipsoidal variable, perhaps in part due to its close proximity to its small-but-massive companion.


PointsOfInterest:
This star was misidentified as BD +48°1318 in the 1991 edition of the Gliese catalog.


PointsOfInterest:
This star was named "Cor Caroli Regis Martyris" in honor of the executed King Charles I of England.


PointsOfInterest:
The apparent visual magnitude of +6 listed for component A2 is just an educated guess, given its spectral and luminosity classes.  Components A1 and A2 have a combined apparent visual magnitude of +3.080; they are too close together to be able to measure their visual magnitudes separately.


PointsOfInterest:
Preliminary trigonometric parallax measurements for this star indicated that it was only some 7.8 light-years away, which would have made this star 300,000 times dimmer than the sun — the most intrinsically dim red dwarf ever discovered (beating out Wolf 359 by a factor of 6 in dimness).  Later observations refined this distance upwards to 12.4 light-years, however, meaning that this star isn't as dim as originally thought.

     The RECONS article on this star indicates that the distance to this object is still up for debate.  The strengths of the star's spectral bands of Calcium Hydride (CaH2) and Titanium Oxide (TiO5) indicate that it's probably not metal-poor, so this star is probably Luminosity Class V, not Luminosity Class VI.


PointsOfInterest:
This red dwarf spins at 27 kilometers per second, which was what probably caused it to throw of two giant radio flares in 2002.


PointsOfInterest:
The distance measured to this star by Hipparcos is inconsistent with the reported luminosity class of the A component.  Either this star is much further away than this, or the A component is a main sequence star and not a red giant at all.


PointsOfInterest:
ARICNS lists a distance to this star of 16.2 light-years, which would make it unbelievably dim.


