Notes from 3-D Star Map

These are the additional notes used by the 3-D Star Map, which I am providing here so the text can be searched as needed. The map itself gives some additional details like distances, spectra, and membership in groups.

Joshua Grosse


Scorpius-Centaurus association

The Scorpius-Centaurus or Sco OB2 Association is the nearest region where massive stars have been forming, called OB associations. These are great expanding groups originating from giant molecular clouds.

This group extends over half a thousand light-years. It is divided into three main subgroups, including many of the brighter stars in the constellations Scorpius, Lupus, Centaurus, and Crux:

Lower Centaurus-Cruxe.g. α, β, δ Cru; α Mus
Upper Centaurus-Lupuse.g. η, κ, ν Cen; α, γ, η Lup; μ¹ Sco
Upper Scorpiuse.g. α, σ, τ Sco; possibly β¹ Sco

All these brighter members are blue B type stars except Antares, a red supergiant and the most luminous. It is followed by Acrux at the closer end, a multiple system only recently recognized as belonging.

The whole group is about 20 million years old, with stars forming in stages triggered by shock-waves as others become supernovae. The youngest are the Upper Scorpius subgroup at only 5 million years old.

This is also connected to the Ophiuchus cloud complex where smaller stars are still forming. These associations and clouds are part of the Gould Belt, a vast expanding arc of gas and young stars around the sun.

See de Zeeuw et al. (1999), A Hipparcos Census of the Nearby OB Associations, and Rizzuto et al. (2011), Multi-Dimensional Bayesian Membership Analysis of the Sco OB2 Moving Group for details.


Ursa Major moving group

The UMa moving group are a dissipating cluster of stars, with similar composition and proper motion but no longer gravitationally bound. They are most likely between 400 and 600 million years old.

Stars from this group have been scattered over several hundred light-years. The central nucleus that remains is about 35 light-years across with under two dozen known members. The brightest are all type A stars.

These are all given names: Merak, Phecda, Megrez, Alioth, and the Mizar system. They mark the celebrated figure of the Big Dipper or Plough along with the more distant stars Dubhe and Alkaid on either end.

Scattered members are harder to recognize, in part since the group moves with one of the main kinematic streams in local space. Some brighter stars thought to belong are α CrB, β Aur, δ Aqr, and the giant ζ Leo.

See King et al. (2003), A Reexamination of the Membership, Activity, and Age of the Ursa Major Group for details.


Hyades

The Hyades are the nearest open star cluster, i.e. a group that are bound gravitationally, although the UMa moving group are closer. They are most likely between 600 and 650 million years old.

At this age there are no blue stars and all the brightest members are giants, namely γ, δ, ε, θ¹, and θ² Tauri. These appear in the sky with Aldebaran, a much closer star, as a V marking Taurus’s head.

The cluster has a tidal diameter of about 60 light-years, with a halo of related but unbound stars. The more distant Praesepe cluster also have similar composition and motion, so likely shares a common origin.

The cluster’s name is Greek from hyein, to rain, as their morning setting marked the rainy season. They were personified as nymphs but not usually given names.

See Röser et al. (2011), A deep all-sky census of the Hyades for details.


Cassiopeia-Taurus association

The Cassiopeia-Taurus association is a moving group including relatively massive stars, thought to represent an older or fossil OB association that has been dispersed over several hundred light-years.

The α Persei cluster is most likely a central remnant of this group around the supergiant Mirfak. These are somewhere between 50 and 100 million years old, and are scattered over about 18º of sky.

Most of these form an unbound halo which grades into the broader moving group. The other brighter members are all type B stars; some examples are ε Cas, η Aur, μ Eri, μ Tau, and perhaps γ Cas, ε Per, and ζ Tau.

This group lies near the centre of the Gould Belt, a vast arc of nearby associations and gas, suggesting that they share a related origin.

See de Zeeuw et al. (1999), A Hipparcos Census of the Nearby OB Associations, Makarov et al. (2006), Precision Kinematics and Related Parameters of the α Persei Open Cluster, and Jameson et al. (2008), The ages of L dwarfs for details.


Pleiades

The Pleiades are one of the nearest and brightest open star clusters. They cover about 9-10º of sky, for a projected diameter of 60 or 70 light-years, and are somewhere between 100 and 125 million years old.

The brighter members are all blue B type stars. Six are easily seen with the unaided eye: Atlas, Alcyone, Merope, Maia, Taygeta, and Electra. In good conditions Pleione, Asterope, Celaeno, and a few more are also visible.

The light from these stars is reflected by a great deal of gas and dust, particularly around Merope. This comes from an otherwise dark molecular cloud that the cluster has passed into.

The name is Greek, likely from plein, to sail. They were personified as seven nymphs, daughters of Pleione and the titan Atlas, who give their names to the main nine stars.

See Stauffer et al. (2007), Near- and Mid-Infrared Photometry of the Pleiades and van Leeuwen (2009), Parallaxes and proper motions for 20 open clusters for details.


Sol

Planetary system – This is our home solar system and so of course the best understood. The main objects are four giant planets with gaseous envelopes:

Mass (MJ)Distance (AU)Period
Jupiter1.005.0 - 5.411.9 years
Saturn0.309.0 - 10.129.4 years
Uranus0.0418.4 - 20.184.3 years
Neptune0.0529.8 - 30.4164.8 years

Jupiter is outside a belt of asteroids around 2 to 3½ AU from the sun. Further in there are four rocky planets, from 0.0002 to 0.003 MJ in mass.

There is also a disk of icy debris extending from Neptune’s orbit to about 55 AU from the sun, thought similar to debris disks around other stars though much less massive than others known.


Sirius (α CMa)

Binary with dwarf – Sirius is a visual binary with a faint white dwarf companion, the closest one to the sun, of type DA2. The two have magnitudes -1.5 and 8.4.

The apparent separation varies from 3 to 11” with a period of 50.1 years. The true orbit has a=7.5”, e=0.59 giving a distance from 8 to 31½ AU.

This is easily the brightest star in the night sky. The name is from ancient Greek Seirios, translated as scorching or sparkling, considered a mark of the summer heat. It is also called the Dog Star or Nile Star.


Canopus (α Car)

Canopus is the 2nd brightest star in the night sky. The name has uncertain meaning but traces back to ancient Greek Kanōpos or Kanōbos, also the name of an Egyptian city and applied to its patron god Serapis.


Rigil Kentaurus (α Cen)

Multiple; planetary companion – Rigil Kentaurus or Alpha Centauri is the nearest star system to the sun, with three component stars:

MagnitudeSpectrumHIP
A = α¹ Cen0.0G2V71683
B = α² Cen1.3K1V71681
C = Proxima11M6Ve70890

There is also a candidate planet with an orbital period of 11.2 days, calculated to be 0.05 AU from Proxima. Its mass is at least 0.004 MJ. Earlier reports of a planet around B have proven a data artifact.

A and B form a visual binary with apparent separation varying from 2 to 22” and an orbital period of 79.9 years. The true orbit has a=17.6”, e=0.52, giving a distance from 11 to 35 AU.

Proxima, the closest of the three stars, is about 2º apart from the main pair. This is an active flare star, occasionally brightening up to a magnitude within a few minutes.

Taken together A and B appear as the 3rd brightest star in the night sky. The name is from Arabic rijl qanṭūris, the centaur’s foot.

See Anglada-Escudé et al. (2016), A terrestrial planet candidate in a temperate orbit around Proxima Centauri for details.


Arcturus (α Boo)

Arcturus is the 4th brightest star in the night sky, taking α¹ and α² Centauri together as third. The name is from ancient Greek Arktouros, the guard or watcher of the bear, since it follows Ursa Major.


Vega (α Lyr)

Vega is surrounded by a debris disk extending about 70 AU from the star. This is the 5th brightest star in the night sky; the name is from Arabic al nasr al wāqiʿ, the falling or swooping eagle, a small asterism.


Capella (α Aur)

Multiple – Capella is a multiple system. The main component is a bright spectroscopic binary, and there is also a faint pair of red dwarfs that share its proper motion:

MagnitudeSpectrum
Capella Aa0.7G5III
Capella Ab1.0G0III
Capella H10.1dM1
Capella L13.7dM5

The bright pair, Aa and Ab, have an orbital period of 104 days. From interferometry the true orbit has a=0.06”, e=0, giving them a constant distance of 0.74 AU.

For the fainter pair, called H and L since other letters were used for field stars, the apparent separation has widened to about 3½”. They are about 12’ away from the main pair.

This is the 6th brightest star in the night sky. The name is Latin for the little nanny goat, as it marks one Auriga is depicted as carrying.


Procyon (α CMi)

Binary with dwarf – Procyon is a visual binary with a white dwarf companion, though a much fainter one than with nearby Sirius. The two have magnitudes 0.3 and 10.9.

The apparent separation varies from 2 to 5” with a period of 41 years. The true orbit has a=4.2”, e=0.41 giving a distance from 9 to 21 AU.

This is the 8th brightest star in the night sky. The name is from Greek prokuōn, before the dog, since it rises before the brighter dog star Sirius.


Betelgeuse (α Ori)

Betelgeuse is a semi-regular variable with magnitude from 0 to 1.3, so changing in brightness by almost 3½ times as it pulses. The main period is about 6 years.

This is the 9th brightest star in the night sky. The name is from Arabic yad al jauzāʾ, the hand of the “central one”, through a supposed derivation from ibṭ, armpit.


Achernar (α Eri)

Achernar is the 10th brightest star in the night sky. The name is from Arabic ākhir al nahr, the river’s end, originally used for Acamar.


Hadar (β Cen)

Binary – Hadar is a spectroscopic binary of two similar stars with an orbital period of 357 days. From interferometry the true orbit has a=0.025”, e=0.82, giving a distance from 0.5 to 5.5 AU.

This is the 11th brightest star in the night sky. The name is from Arabic ḥaḍāri, likely meaning settled land, for an uncertain star. It is also called Agena from Latin genu, knee, and the mistaken designation α.


Altair (α Aql)

Altair is the 12th brightest star in the night sky. The name is from Arabic al nasr al ṭāʾir, the flying eagle, a small asterism.


Acrux (α Cru)

Multiple – Acrux is a multiple system. The main component, designated α¹, is a spectroscopic binary with an orbital period of about 0.2 years. There are also two other nearby stars that share its proper motion.

The brighter of these, designated α², is about 4½” away forming a visual double with magnitudes 1.4 and 2. It has type B1V and is thought to be a spectroscopic binary as well.

The fainter star is about 1½’ from the others, but since it is only magnitude 4.8 despite a similar spectral type of B4IV, it is likely not really nearby.

Taken together these shine as the 13th brightest star in the night sky. The name is a contraction of their Bayer designation, Alpha Crucis.


Aldebaran (α Tau)

Aldebaran is a slow irregular variable with magnitude from 0.75 to 0.95, so changing in brightness by about 1.2 times as it pulses. Some radial velocity changes may also be from a candidate planet.

This is the 14th brightest star in the night sky. The name is from Arabic al dabarān, probably meaning the follower, since it follows the Pleiades in the sky and zodiac.


Spica (α Vir)

Binary – Spica is a spectroscopic binary with a fainter B2V companion. The orbital period is 4.01 days, associated with slight variations of the brighter star by about 0.1 magnitudes.

This is the 15th brightest star in the night sky. The name is from Latin for a spike or ear of grain, which Virgo is often depicted as holding.


Antares (α Sco)

Binary – Antares is a slow irregular variable with magnitude 0.9-1.2, so changing in brightness by about 1.3 times. It also has a B2.5V companion of magnitude 5, separated by about 3” and slowly narrowing.

This is the 16th brightest star in the night sky. The name is from Greek Antarēs, the rival of Ares or Mars, which passes nearby and shares its red colour.


Pollux (β Gem)

Planetary companion – Pollux has one known planet with an orbital period of 1.6 years, calculated to be 1.6-1.8 AU from the star. From limits to inclination the mass is between 2.8 and 13 MJ.

This is the 17th brightest star in the night sky. The name is the Roman equivalent for the Greek hero Polydeuces, twin brother of Castor, who together are guides for mariners.

See Reffert et al. (2006), Pollux and Its Planetary Companion, and Reffert & Quirrenbach (2011), Mass constraints on substellar companion candidates for details.


Fomalhaut (α PsA)

Planetary system – Fomalhaut is a young star with surrounding debris. The main portion is a dusty ring from 133 to about 160 AU, which is elliptical with e=0.1 and a sharp inner margin.

This suggests the influence of at least one shepherd planet. There is also unresolved material closer to the star, thought to include hot dust within a few AU and an ice-line belt about 10 AU out.

An object has been detected in visible light near the main ring, but with a highly eccentric orbit that will take it much further out. This is a dust cloud possibly associated with a planet anywhere below 1 MJ in mass.

The star is also likely part of a triple system as it shares proper motion with two nearby red dwarfs:

MagnitudeSpectrum
A = α PsA1.2A4V
B = TW PsA6.4-6.5K4V
C = LP 876-1012.6M4V

B varies slightly in magnitude as it rotates, with a period of 10.3 days, while C has its own smaller debris disk. They are respectively about 2º and 6º from the main star.

Fomalhaut itself is the 18th brightest star in the night sky. The name is from Arabic fam al ḥūt, the fish’s mouth.

See Kalas et al. (2013), STIS Coronagraphic Imaging of Fomalhaut, and Kennedy et al. (2013), Discovery of the Fomalhaut C debris disc for details.


Mimosa (β Cru)

Binary – Mimosa has an unseen companion, detected by radial velocity changes, with an orbital period of 5.0 years.

This is the 20th brightest star in the night sky. The name is of recent and uncertain origin, though it is shared by southern shrubs that often respond to touch, and so were given it from Greek mimos, mime.


Regulus (α Leo)

Regulus is the 21st brightest star in the night sky. The name is from Latin for the little king.


Adhara (ε CMa)

Adhara is the 22nd brightest star in the night sky. The name is from Arabic al ʿadhārā, the virgins, a small asterism.


Castor (α Gem)

Multiple – Castor is a multiple system. The main components, designated α² and α¹, are each a spectroscopic binary. There is also a third pair that shares their proper motion.

MagnitudeSpectra
Aa, Ab = α² Gem1.6A1V
Ba, Bb = α¹ Gem3.0A2Vm or A5V
Ca, Cb = YY Gem9.1dM1e + dM1e

Both α² and α¹ have red dwarf companions, with respective orbital periods of 9.21 and 2.92 days. Their apparent separation from one another varies from 1.8 to about 7” with a period of 4½ centuries.

YY Gem is about 70” from the others. This is an eclipsing binary, fading to magnitude to 9.6 when one star passes the other, with an orbital period of 19.5 hours. It may also brighten slightly from flares.

Taken together these shine as the 23rd brightest star in the night sky. The name Castor is from a Greek hero, twin brother of Polydeuces or Pollux, who together are guides for mariners.


Shaula (λ Sco)

Multiple – Shaula is a spectroscopic triple. The two main stars are both type B2 with an orbital period of 2.88 years. From interferometry the true orbit has a=0.05”, e=0.12, giving a distance between 5 and 15 AU.

The brighter star also has a closer companion with an orbital period of 6.0 days, probably a pre-main sequence star. This is an eclipsing pair, dimming by about half a magnitude, though the star itself varies by about the same.

This is the 24th brightest star in the night sky. The name is from Arabic al shaula, the stinger.


Gacrux (γ Cru)

Gacrux is the 25th brightest star in the night sky, though slightly variable. The name is a contraction of its Bayer designation, Gamma Crucis, out of analogy to Acrux.


Bellatrix (γ Ori)

Bellatrix is the 26th brightest star in the night sky. The name is Latin for a female warrior, first applied to Capella.


Elnath (β Tau)

Elnath or El Nath is named from Arabic al naṭḥ, the butting, originally used for stars in Aries. It was traditionally shared with the constellation Auriga, so given the designation γ Aurigae as well as β Tauri.


Miaplacidus (β Car)

Miaplacidus has a name of recent and uncertain origin. It may come from Latin placidus, calm along with Arabic miyah, waters, noted as a possible root in Star Names: Their Lore and Meaning by R.H. Allen.


Al Na’ir (α Gru)

Al Na’ir is named from Arabic al nayyir min dhanab al ḥūt, the bright one from the fish’s tail, from an earlier depiction as part of Piscis Austrinus.


Alioth (ε UMa)

Alioth is the brightest star in the nucleus of the UMa moving group, forming the middle of the Big Dipper or Plough. This is also a magnetic variable like Cor Caroli, with strong chromium and europium lines in its spectrum.

The name is from Arabic al jaun, the black horse or bull, through a later misspelling.


Dubhe (α UMa)

Multiple – Dubhe is a multiple system. The main component is a close binary with an F companion, and there is also a second spectroscopic binary which shares its proper motion.

The brighter pair have magnitude 3.6 and 5.7 and their apparent separation varies from 0.3 to 0.8” with an orbital period of 44 years. The true orbit has a=0.6”, e=0.4, giving a distance from over 10 to around 30 AU.

The fainter binary, HD 95638, has magnitude 7.2 and is about 6.3’ away. This is an F7V star with an unseen companion, which has an orbital period of 6 days.

Dubhe’s name is from Arabic ẓahr al dubb al akbar, the greater bear’s back, as given in Star Names: Their Lore and Meaning by R.H. Allen.


Kaus Australis (ε Sgr)

Kaus Australis is named with δ and λ Sgr from Arabic al qaus, the bow, formerly a small asterim. Latin australis marks it as the southern of the three.


Mirfak (α Per)

Mirfak is the bright central star of what is called the α Persei cluster after it. The name is from Arabic mirfaq al thurayyā, the Pleiades’ elbow, as part of an asterism depicting two arms from them.


Alkaid (η UMa)

Alkaid is named from Arabic al qāʾid, the leader, as the first star of the asterism banāt naʿsh, the daughters of the bier, which is the modern Big Dipper or Plough. It is also called Benetnasch from the same source.


Menkalinan (β Aur)

Binary – Menkalinan is an eclipsing binary of two similar stars, fading slightly from magnitude 1.9 to 2.0 with an orbital period of 3.96 days. The name is from Arabic mankib dhīʾl ʿinān, the rein-holder’s shoulder.


Alhena (γ Gem)

Binary – Alhena is a spectroscopic binary with a faint companion, which has an orbital period of 12.6 years. The name is from Arabic al hanʿa, meaning a brand on a camel’s neck.


Peacock star (α Pav)

Binary – The peacock star is a spectroscopic binary with an unseen companion, which has an orbital period of 11.8 days. The name is from English for the constellation Pavo.


Atria (α TrA)

Atria is named from a contraction of its Bayer designation, Alpha Trianguli Australis.


Delta Velorum

Multiple – δ Velorum is a triple system. The main component is an eclipsing binary with a smaller type A companion, fading from magnitude 2.0 to 2.4 with an orbital period of 45.2 days.

From interferometry this pair have a true orbit with a=0.017”, e=0.29, giving a distance from 0.3 to 0.5 AU. The farther star has magnitude 5.1, separated from them by about 2.5” and slowly narrowing.


Avior (ε Car)

Binary – Avior is a close binary with a B2V companion. The two have magnitudes 2.0 and 3.8, possibly eclipsing with a period of 2 years. The name was invented for use by aviators.


Algieba (γ Leo)

Binary; planet / dwarf companion – Algieba is a visual binary with a G7III companion. There is also what is probably a brown dwarf, though it might also be a large planet or small star.

The latter has an orbital period of 1.17 years, calculated to be about 1.0-1.4 AU from the brighter star. The mass is not known but with possible inclinations is at least 10 MJ.

The two stars, designated γ¹ and γ², have magnitudes of about 2 and 3½. The apparent separation has widened to a maximum of about 4½”, with a period of centuries and distance of perhaps 1-10 hundred AU.

The star’s name is from Arabic al jabha, the forehead, applied to a group of several stars including this and Regulus.

See Han et al. (2010), Detection of a planetary companion around the giant star γ¹ Leonis and Reffert & Quirrenbach (2011), Mass constraints on substellar companion candidates for details.


Hamal (α Ari)

Planet / dwarf companion – Hamal has a companion planet or brown dwarf with an orbital period of 381 days, calculated to be 0.9-1.5 AU from the star. The mass is not known but is at least 1.8 MJ.

The star’s name is from Arabic al ḥamal, the lamb, used for the constellation.

See Lee et al. (2011), A likely exoplanet orbiting the oscillating K-giant α Arietis for details.


Mirzam (β CMa)

Mirzam is an example of the β Cephei-type variables, blue stars with small fast pulsations. The name is from Arabic al mirzam, used for several stars that herald the rising of much brighter ones, in this case Sirius.


Mira (ο Cet)

Binary with dwarf – Mira is the archetype of the long-period variables, cooler giants that undergo very large oscillations over months or years. It is also a binary with a faint companion, VZ Cet, which is itself variable.

Usually Mira ranges in magnitude from about 2.5 to 10, though this varies, so changing over a thousand times in brightness. The main period is 322 days but with many shorter fluctuations.

This star likewise changes considerably in size and temperature, with spectral type about M2 at its brightest but cooling to M7 as it dims. Although very large at maximum, it is likely not particularly massive.

VZ Cet is about ½” away with an orbital period of centuries, and it varies from magnitude 9.5 to 12. This is though to be a white dwarf of type DA, with an accretion disk of gas from Mira giving most of its light.

Mira was the first variable star recognized, noted by Fabricius in 1596 as appearing where no star had been visible. It is named from Latin stella mira, wonderful star, as it was later called by Hevelius.


Alphard (α Hya)

Alphard is named from Arabic al fard, the alone or solitary one, since no other stars of comparable brightness appear nearby.


Polaris (α UMi)

Multiple – Polaris is a multiple system. The main component is a spectroscopic binary with a smaller main sequence star. There is also an F3V companion that shares their proper motion.

The closer pair has an orbital period of 30 years, with an apparent separation up to 0.2”. The farther star is 18” away forming a visual pair with magnitudes about 2.0 and 8, though the former is slightly variable.

This is the noticeable star closest to our current north pole, which will come within half a degree, and so a great friend to those finding their way. The name is from Latin stella polaris, the polar star.


Deneb Kaitos (β Cet)

Deneb Kaitos is named from Arabic dhanab kaiṭus, the sea monster’s tail. It is also called Diphda from the older name ḍifdiʿ al thānī, the second frog, with Fomalhaut as the first.


Alpheratz (α And)

Binary – Alpheratz has a spectroscopic companion with an orbital period of 96.7 days. From interferometry the true orbit has a=0.024”, e=0.53, giving them a distance from 0.3 to 1.1 AU.

The brighter star is also a magnetic variable, with only small changes in magnitude but strong mercury and manganese lines in its spectrum.

This star was previously shared with the constellation Pegasus, so given the designation δ Pegasi as well as α Andromedae. It is also called Sirrah from Arabic surrat al faras, the horse’s navel.


Menkent (θ Cen)

Menkent is named from a contraction of Arabic mankib, shoulder, with qanṭūris for the constellation.


Kochab (β UMi)

Planet / dwarf companion – Kochab has a companion planet or brown dwarf with an orbital period of 1.43 years, calculated to be about 1-1½ AU from the star. The mass is not known but is at least 5 MJ.

This was the brightest star near the north pole before Polaris, passing 6º apart at their closest 2500 years ago. Its name is usually given as from Arabic al kaukab, the star.

See Lee et al. (2014), Planetary companions in K giants β Cancri, μ Leonis, and β Ursae Minoris for details.


Rasalhague (α Oph)

Binary – Rasalhague is a close binary with a type K companion, with apparent separation only up to about ½”. The two have magnitudes 2.1 and 5 with an orbital period of 8.6 years.

The name is also commonly written Ras Alhague, from Arabic raʾs al ḥawwāʾ, the serpent-carrier’s head.


Algol (β Per)

Multiple – Algol gives its name to the Algol-type eclipsing binaries, which have distinct drops in apparent brightness when one component blocks another. It is actually a multiple system with three stars:

MagnitudeSpectrum
Algol A2.1B8V
Algol B12½K0IV
Algol C12½A7m

A and B have an orbital period of 2.87 days. The magnitude of the pair drops to 3.4 when the larger sub-giant is in front, with much smaller eclipses when it is partly obstructed by the brighter star.

From interferometry the true orbit has a=0.002”, e ≈ 0, giving them a distance of around 0.06 AU. The larger star is less massive although more evolved, and so is thought to have lost material to its smaller partner.

The third star is farther away with an orbital period of 1.8 years, reflected by minute but regular changes in the motion of the A-B pair.

Algol’s name is from Arabic raʾs al ghūl, the demon’s head, as it marks the head of Medusa carried by Perseus. Its variation was recorded during the late 17th and explained by Goodricke in the late 18th century.


Beta Gruis

β Gruis is a semi-regular variable with magnitude from 1.9 to 2.3, so changing in brightness by about 1.4 times as it pulses.


Denebola (β Leo)

Denebola is surrounded by a debris disk extending about 80 AU from the star. The name is from Arabic dhanab al asad, the lion’s tail.


Alphecca (α CrB)

Binary – Alphecca is an eclipsing binary with a G5V companion, fading slightly from magnitude 2.2 to 2.3 with an orbital period of 17.4 days. The main star also has a debris disk extending out about 45 AU.

The name is from Arabic al fakka for the constellation, meaning broken, as it only forms part of a circle. It is also called Gemma, Latin for gem.


Lambda Velorum

λ Velorum is a semi-regular variable with magnitude from 2.1 to 2.3, so changing in brightness by almost 1.2 times as it pulses.

This star is often called Suhail from its Arabic name suhail al wazn. The term suhail is also used for Canopus and other bright southern stars, but its origin is obscure.


Mizar (ζ UMa)

Multiple – Mizar is a multiple system. The main components are two spectroscopic binaries, which form a visual pair with magnitudes 2.3 and 4.0. Their apparent separation is 15”.

The brighter pair are both A2V type stars with an orbital period of 20.5 days. From inferterometry the true orbit has a=0.001”, e=0.5, giving a distance from 0.1 to 0.4 AU.

The second pair are type Am with an orbital period of 175.5 days. Besides these four stars, astrometry suggests there may be an unseen component with a period of 35 years around the first pair.

Mizar is also a well-known double with Alcor, another binary 12’ away. These are both part of the Ursa Major moving group which share proper motion.

The name is from Arabic miʾzar, the girdle or apron, applied based on a misspelling of Merak. This was both the first known visual binary, noted by Castelli in 1616, and the first known spectroscopic binary.


Caph (β Cas)

Caph is named from Arabic al kaff al kaḍīb, the stained hand, an asterism corresponding to Cassiopeia.


Dschubba (δ Sco)

Multiple – Dschubba is a multiple system. The main star is a Be star like γ Cas, becoming active when it is farthest from a B3V companion. The total magnitude varies from 1.6 to 2.3, so changing about 2 times in brightness.

This companion star is a much fainter magnitude 4.6, with an orbital period of 10.8 years and apparent separation up to 0.2”. The true orbit has a=0.10”, e=0.94 giving a distance from 1 to 30 AU.

The variable also has a closer spectroscopic companion with an orbital period of about 20 days. A possible fourth, more distant star has been detected by occultation.

The name is from Arabic jabhat al ʿaqrab, the scorpion’s forehead, applied to the small group of stars around this one.


Eta Centauri

η Centauri is a Be variable like γ Cas. Its magnitude varies from 2.3 to 2.4, so changing in brightness by about 1.1 times as it expels shells of material.


Merak (β UMa)

Merak is surrounded by a debris disk extending a little over 45 AU from the star. The name is from marāqq al dubb al akbar, the greater bear’s flank or loin.


Ankaa (α Phe)

Binary – Ankaa is a spectroscopic binary with an unseen companion, which has an orbital period of 10.5 years. The name is from Arabic al ʿanqāʾ, a mythical bird, for the modern constellation.


Scheat (β Peg)

Scheat is a semi-regular variable with magnitude from 2.3 to over 2.7, so changing in brightness by about 1.5 times as it pulses. The name is from Arabic al sāq, the shin, originally for Skat.


Sabik (η Oph)

Binary – Sabik is a close binary with an A3V companion, with apparent separation only up to about ½”. The two have magnitudes 3 and 3½ with an orbital period of 87.6 years.

The true orbit has a=1.4”, e=0.95, giving a distance from within a few AU out to about 45 AU. The name is from Arabic al sābiq, possibly meaning the preceding one.


Phecda (γ UMa)

Phecda is a fast-rotating star with an envelope of expelled gas giving it an emission spectrum, like in the hotter Be stars. The name is from Arabic fakhidh al dubb al akbar, the greater bear’s thigh.


Alderamin (α Cep)

Alderamin is variously given as named from Arabic al dhirāʿ al yamīn, the right forearm, or al dhirāʿain, the two forearms, which actually applied to an asterism covering Gemini and Canis Minor.


Gamma Cassiopeiae

γ Cassiopeiae is the archetype of the Be variables. These are fast-spinning type B stars that lose material in equatorial shells, causing irregular drops in apparent brightness and temperature.

This star varies in magnitude from about 1.6 to 3, so changing in brightness by more than 3½ times. It is one of the only northern stars so bright that has no name in Western tradition.


Epsilon Cygni

ε Cygni is likely binary as it shares its proper motion with a faint M3 star, separated by 1.2’. It is named Gienah from Arabic janāḥ, wing, though this is also commonly used for γ Corvi.


Zosma (δ Leo)

Zosma is named from Greek zōsma or zōma, a loincloth or girdle, applied to the star in confusion over a medieval text.


Delta Centauri

δ Centauri is a Be variable like γ Cas. Its magnitude varies from 2.5 to over 2.6, so changing in brightness by about 1.1 times as it expels shells of material.


Ascella (ζ Sgr)

Binary – Ascella is a close visual binary with an A4IV companion, varying in apparent separation from 0.2 to 0.6”. The two have magnitudes 3.3 and 3.5 with an orbital period of 21.0 years.

The true orbit has a=0.49”, e=0.21, give a distance from 10 to 16 AU. The name is from Latin axilla, armpit, becoming ascella in derived languages like Italian.


Unukalhai (α Ser)

Unukalhai is named from Arabic ʿunuq al ḥayya, the serpent’s neck.


Sheratan (β Ari)

Binary – Sheratan has a faint companion with an orbital period of 107 days. From interferometry the true orbit has a=0.036”, e=0.90, giving a distance from 0.07 to 1.2 AU.

The name is from Arabic al sharaṭān, the two signs, originally applied to both it and Mesarthim. These formerly marked the sun’s position on the vernal equinox.


Ruchbah (δ Cas)

Binary – Ruchbah is an eclipsing binary with an unseen companion, fading slightly from magnitude 2.7 to 2.8 with an orbital period of 2.1 years. The name is from Arabic rukbat dhāt al kursīy, the lady of the chair’s knee.


Muphrid (η Boo)

Binary – Muphrid is a spectroscopic binary with an unseen companion, which has an orbital period of 1.35 years.

The name is from Arabic mufrad al ramīḥ, the lone one of the lancer, who was at first represented by Arcturus but later as a small asterism or this one star.


Porrima (γ Vir)

Binary – Porrima is a visual binary of two similar stars. The apparent separation varies from 0.4 to 6” with a period of 169 years. The true orbit has a=3.6”, e=0.88 giving a distance from 5 to 80 AU.

The name is from an attribute or sister of Carmentis, a Roman goddess of child-birth and prophecy. She is one of several figures that have been associated with Virgo, though only more recently with this star.


Cebalrai (β Oph)

Cebalrai is named from Arabic kalb al rāʿī, the shepherd’s dog, part of a group of figures with Rasalhague marking the shepherd and other stars sheep.


Zubenelgenubi (α² Lib)

Multiple – Zubenelgenubi forms a visual binary with nearby α¹ Lib, which shares its proper motion. The two have magnitudes 2.8 and 5.2, with an apparent separation of 3.8’.

Both of these are spectroscopic binaries, though the brighter pair have odd spectral lines and apparently uncertain period. Fainter α¹ has an orbital period of 14 years with one F3V spectrum seen.

The name is from Arabic al zubānā al janūbī, the southern claw, from an early depiction as part of Scorpius.


Cursa (β Eri)

Cursa is named from Arabic kursīy al jauzāʾ, the footstool of the “central one”, which applied to two small asterisms near Orion.


Rho Puppis

ρ Puppis is a δ Scuti variable with magnitude from 2.7 to 2.9, so changing in brightness about 1.2 times as it pulses. The main period is 3.38 hours.


Vindemiatrix (ε Vir)

Vindemiatrix is named from Latin for a female vintager, formerly the male form vindemiator, as its rising marked the beginning of the harvest.


Kaus Borealis (λ Sgr)

Kaus Borealis is named with δ and ε Sgr from Arabic al qaus, the bow, formerly a small asterism. Latin borealis marks it as the northern of the three.


Alpha Arae

α Arae is a Be variable like γ Cas, as well as showing smaller modulations on the order of 1 day. Its magnitude varies from 2.7 to 3.0, so changing in brightness by about 1.3 times as it expels shells of material.


Deneb Algedi (δ Cap)

Binary – Deneb Algedi is an eclipsing binary with an unseen companion, fading slightly from magnitude 2.8 to 3.0 with an orbital period of 1.02 days. The name is from Arabic dhanab al jady, the kid’s tail.


Alcyone (η Tau)

Alcyone is the brightest star in the Pleiades, one of the nearest open clusters. The name is from one of the daughters of Pleione in Greek mythology.


Cor Caroli (α² CVn)

Cor Caroli gives its name to the α² CVn-type variables, bluish-white stars with very strong magnetic fields. They share peculiar spectra with strong lines from elements such as silicon, chromium, and europium.

These are rotational variables rather than pulsating stars, i.e. the brightness is seen to change slightly because the surface is not even. The magnetic field and strength of different spectral lines also vary.

This star ranges from magnitude 2.84 to 2.98, so changing in brightness about 1.1 times, with a period of 5.47 days. Most other α² CVn stars show smaller changes.

The name is Latin for the heart of Charles, named by Hevelius in honour of the overthrown king Charles I of England.


Algorab (δ Crv)

Algorab is named from Arabic janāḥ al ghurāb, the raven’s wing, originally used for γ Corvi and later both stars.


Alnasl (γ Sgr)

Alnasl is named from Arabic al naṣl, the point or arrowhead.


Beta Trianguli

Binary – β Trianguli has a spectroscopic companion with an orbital period of 31.4 days. The true orbit has a=0.008”, e=0.44, giving a distance within ½ AU. There is also a debris disk extending out about 120 AU.


Seginus (γ Boo)

Seginus has a more or less meaningless name derived from a series of mistranslations and corruptions, apparently originating from the Greek name Boōtēs, the ploughman, for the constellation.


Rasalgethi (α Her)

Multiple – Rasalgethi is a triple system. The brightest star, designated α¹, is a semi-regular variable with magnitude 2.7 to 3.4, so changing in brightness by about 2.3 times as it pulses.

This is about 4.5” away from the fainter component, α², in turn a magnitude 5.4 spectroscopic binary. Its two stars have types G5III and F2V, with an orbital period of 51.6 days.

Rasalgethi’s name is from Arabic raʾs al jāthī, the kneeler’s head.


Altais (δ Dra)

Altais is named from Arabic al tais, the billy goat, ultimately applied from a misreading of the constellation name.


Talitha (ι UMa)

Multiple – Talitha is a multiple system with two pairs of stars. The brighter is a spectroscopic binary with an orbital period of 11 years, and the fainter is a pair of red dwarfs with a period of 40 years.

Together these form a visual double with magnitudes 3.1 and 9½, though the former is slightly variable. The apparent separation is about 4½” and slowly narrowing.

The name is from Arabic al qafza al thālitha, the third leap, originally applied to both it and κ UMa as one of three optical pairs depicted as gazelle tracks.


Wazn (β Col)

Wazn is named from Arabic al wazn, meaning weight, originally for an uncertain star and later applied to this and Wezen.


Errai (γ Cep)

Binary; planet / dwarf companion – Errai is a spectroscopic binary with a faint red dwarf companion, probably type M4V by mass. There is also a brown dwarf or less likely planet.

The latter has an orbital period of 2.5 years, calculated to be about 2 AU from the main star. Measurement of inclination limits the mass to between 5 and 30 MJ, based on the new minimum from Endl et al.

The red dwarf has an orbital period of 67 years. Astrometry gives this a true orbit with a=1½”, e=0.4 for a distance from 12-30 AU, relatively close to the substellar companion.

The star’s name is from Arabic al rāʿī, the shepherd, part of a group of figures with other stars marking his dog and sheep.

See Neuhäuser et al. (2007), Direct detection of exoplanet host star companion γ Cep B, Reffert & Quirrenbach (2011), Mass constraints on substellar companion candidates, and Endl et al. (2011), News from the γ Cephei Planetary System for details.


Yed Posterior (ε Oph)

Yed Posterior is named with δ Oph from Arabic al yad, the hand. Latin posterior marks it as the latter of the two as they move west through the sky.


Nu Ophiuchi

Dwarf companions – ν Ophiuchi is orbited by two known brown dwarfs with a nearly 6:1 ratio in period. Radial velocity gives their properties as follows:

Mass (MJ)Distance (AU)Period
ν Oph bAt least 231.6 - 2.11.45 years
ν Oph cAt least 265.0 - 7.48.7 years

This ratio might be explained by formation and migration in a circumstellar disk, more similar to large planets than small stars despite their masses.

See Sato et al. (2012), Substellar Companions to Seven Evolved Intermediate-Mass Stars and Hou et al. (2014), The Probabilities of Orbital-Companion Models for Stellar Radial Velocity Data for details.


Edasich (ι Dra)

Planet / dwarf companion – Edasich has a candidate planet or brown dwarf with an orbital period of 1.4 years, calculated to be 0.4-2 AU from the star. Limits to inclination place the mass between 11.5 and 28 MJ.

The star’s name is from Arabic al dhīkh, the male hyena.

See Reffert & Quirrenbach (2011), Mass constraints on substellar companion candidates and Baines et al. (2011), Fundamental Parameters of the Exoplanet Host K Giant Star ι Draconis from the Chara Array for details.


Megrez (δ UMa)

Megrez is named from Arabic maghriz al dubb al akbar, the root of the tail of the greater bear.


Propus (η Gem)

Multiple – Propus is a triple system. The brightest star is a semi-regular variable with magnitude from under 3.2 to 3.9, so changing in brightness by about 2.0 times as it pulses.

This is also a slightly eclipsing binary with an orbital period of 8.2 years. It in turn forms a visual pair with the third star, which has magnitude 6.2, separated by about 1.6” and slowly widening.

Propus’s name is from Greek propous, here meaning the forward foot.


Muscida (ο UMa)

Planet / dwarf companion – Muscida has a candidate planet with an orbital period of 4.5 years, calculated to be about 3½-4½ AU from the star. The mass is not known but is at least 4 MJ.

The star’s name is from Medieval Latin, related to musum, muzzle.

See Sato et al. (2012), Substellar Companions to Seven Evolved Intermediate-Mass Stars for details.


Theta-2 Tauri

Binary – θ² Tauri is the brightest star system in the Hyades, the nearest open cluster. It itself is a spectroscopic binary with a fainter companion, also possibly associated with some other cluster stars.

This pair have magnitudes about 3.4 and 5, though the former is slightly variable. The orbital period is 140.7 days, and astrometry gives them a true orbit with a=0.02”, e=0.74, for a distance from 0.2-1.5 AU.


Eta Cassiopeiae

Binary – η Cassiopeiae is a visual binary with a K7V companion. The two have magnitude 3.5 and 7.3, described as yellow and red or purple in telescopes from contrast.

The apparent separation varies from 5 to 16” with a period of 5 centuries. The true orbit has a=12”, e=0.50 giving a distance from 35 to 110 AU.


Eta Ceti

Planetary system – η Ceti has two candidate planets, with properties based on radial velocity as follows:

Mass (MJ)Distance (AU)Period
η Cet bAt least 2.41 - 1½1.1 years
η Cet cAt least 322.0 years

The inclinations are not known, but for a stable system are most likely to be coplanar orbits seen close to edge-on, which would limit the masses to 4 and 5 MJ.

See Trifonov et al. (2014), A possible 2:1 resonant planet pair around the K giant star η Cet for details.


Tau Ceti

τ Ceti is surrounded by a debris disk extending a little more than 65 AU from the star. There has been a great deal of interest in finding planets but none are conspicuous.


Beta Cancri

Planet / dwarf companion – β Cancri has a companion planet or brown dwarf with an orbital period of 1.7 years, calculated to be about 1½-2 AU from the star. The mass is not known but is at least 7 MJ.

See Lee et al. (2014), Planetary companions in K giants β Cancri, μ Leonis, and β Ursae Minoris for details.


Wasat (δ Gem)

Multiple – Wasat is a multiple system. The main component is a spectroscopic binary with an orbital period of 6.2 years, with only one spectrum seen. There is also type K3V companion further out.

These form a visual pair with magnitudes 3.5 and 8.2, and an apparent separation of about 6” and slowly narrowing. The name is from Arabic wasaṭ, middle, applied to the star accidentally.


Epsilon Tauri

Planet / dwarf companion – ε Tauri is one of the Hyades and has the first candidate planet found in an open cluster. The orbital period is 1.6 years. It is calculated to be 1½-2 AU from the star, with a mass of at least 7 MJ.

This star is sometimes called Ain from Arabic ʿain al thaur, the bull’s eye, originally used for Aldebaran.

See Sato et al. (2007), A Planetary Companion to the Hyades Giant Epsilon Tauri and Kunitomo et al. (2011), Planet Engulfment by ~1.5-3 Solar-Mass Red Giants for details.


Zeta Leporis

ζ Leporis is surrounded by a debris disk extending only about 3 AU from the star, so probably more like the asteroid belt than most other disks.


Chi Draconis

Binary – χ Draconis is a close binary with a K0V companion. The two have magnitude 3.6 and 5.7 with a period of 250.5 days. The true orbit has a=0.12”, e=0.43 giving a distance around one AU.


Rotanev (β Del)

Binary – Rotanev is a close binary with a similar but fainter F6 companion. The two have magnitudes 4.1 and 5.0 with a period of 26.6 years. The true orbit has a=0.44”, e=0.36, giving a distance from 8½ to 18½ AU.

This star and Sualocin were named by Piazzi after his assistant Nicolaus Venator, hidden by spelling his name in reverse.


Nusakan (β CrB)

Binary – Nusakan forms a close visual binary with an F2V companion, with apparent separation only up to about 0.3”. The two have magnitudes 3.7 and 5.2 with an orbital period of 10.5 years.

The true orbit has a=0.20”, e=0.5, giving a distance from 3 to 11 AU. The brighter star is also a magnetic variable, with small changes in magnitude but strong strontium and chromium lines in its spectrum.

The name is from Arabic al nasaqān, the two lines, which actually applied to an asterism around nearby Serpens.


Alshain (β Aql)

Alshain is likely a binary as it shares its proper motion with a faint M3 star, 12” away. Both it and Tarazed are named from Persian shāhin-i tarāzū, the scale beam, a small asterism around Altair.


Epsilon Eridani

Planetary system – ε Eridani is a young star surrounded by large amounts of debris. This is divided into three regions: two asteroid belts about 3 and 20 AU out, and an outer disk of ice and silicates from 35 to 110 AU.

This arrangement suggests two or three large planets, one just outside each belt and possibly one just inside the disk. So far there has been one found with an orbital period of 6.8 years.

Astrometry gives this a mass of 1.5 MJ and an orbit with a=1.0”, e=0.7. This gives a distance from 1 to 6 AU, but this would cross the inner belt, suggesting the orbit is actually much less elliptical.

See Benedict et al. (2006), The Extrasolar Planet ε Eridani b, and Backman et al. (2009), Epsilon Eridani’s Planetary Disk for details.


Gamma Ophiuchi

γ Ophiuchi is surrounded by a debris disk extending about 500 AU from the star.


Alula Australis (ξ UMa)

Multiple – Alula Australis is a multiple system with two visible stars, each of which is also a spectroscopic binary. These form a telescopic pair with magnitudes 4.3 and 4.8.

The apparent separation varies from 0.9 to 3.1” with an orbital period of 59.88 years. This was the first true orbit to be determined. It has a=2.54”, e=0.4, giving a distance from about 13 to 30 AU.

In both binaries the companion has low mass and only one spectrum is seen. The brighter is type G0V with an orbital period of 1.83 years, and the fainter is type G5V with a period of 4.0 days.

This and ν UMa are named from Arabic al qafza al ūlā, the first leap, as one of three optical pairs depicted as gazelle tracks. Latin australis marks it as the southern of the two.

Note – this system is missing from the Hipparcos results. Its parallax is taken from Siregar & Nugroho (2006), On the Orbit of Visual Binary ADS 8119 AB.


Beta Pictoris

Planetary system – β Pictoris is a very young star surrounded by thick debris disk. The main component extends about 250 AU from the star, though some material reaches several times farther out.

This system also has a secondary disk to about 130 AU with a tilt of 5º from the first. Both are seen nearly edge-on and show some asymmetry, with a slight fold between the two wings.

The dust is relatively clear within 50 AU from the star except for belts noted around 6, 16, and 30 AU out, thought to be from planetesimals. These suggest three large to medium-sized planets in the gaps.

So far the first has been detected optically, with a slighltly inclined orbit at least 8 AU from the star, possibly causing the tilted disk. The mass is expected to be between 6 and 12 MJ.

See Golimowski et al. (2006), Hubble Space Telescope ACS Multiband Coronagraphic Imagining of the Debris Disk around β Pictoris, Freistetter et al. (2007), Planets of β Pictoris revisited, and Chauvin et al. (2012), Orbital characterization of the β Pictoris b giant planet for details.


Mu Leonis

Planet / dwarf companion – μ Leonis has a companion planet or brown dwarf with an orbital period of 358 days, calculated to be about 1 AU from the star. The mass is not known but is at least 2 MJ.

This star is sometimes called Rasalas from Arabic raʾs al asad, the lion’s head, originally applied to both it and ε Leo.

See Lee et al. (2014), Planetary companions in K giants β Cancri, μ Leonis, and β Ursae Minoris for details.


C Hydrae

C Hydrae is surrounded by a debris disk extending only about 2 AU from the star, so probably more like the asteroid belt than most other disks.


Alpha Sagittarii

α Sagittarii is surrounded by a debris disk extending about 4½ AU from the star. It is sometimes called Rukbat from Arabic rukbat al rāmī, the archer’s knee.


Nu-2 Canis Majoris

Planet / dwarf companion – ν² or 7 Canis Majoris has a candidate planet with an orbital period of 2.2 years, calculated to be about 1½-2½ AU from the star. The mass is not known but is at least 2.4 MJ.

See Wittenmyer et al. (2016), Five companions orbiting giant stars for details.


Gamma Trianguli

γ Trianguli is surrounded by a debris disk extending about 240 AU from the star.


Alcor (80 UMa)

Binary – Alcor is a binary with a very faint M3-4V companion 1.1” away. It in turn forms a well-known visual double with Mizar, about 12’ apart and sharing proper motion as part of the Ursa Major moving group.

The name is from a misspelling of Arabic al jaun, the black horse or bull, though this properly applied to Alioth.


70 Ophiuchi

Binary – 70 Ophiuchi is a visual binary with a K4V companion. The two have magnitude 4.2 and 6.0, described as yellow and red or purple in telescopes from contrast.

The apparent separation varies from 1½ to 7” with a period of 88.4 years. The true orbit has a=4.5”, e=0.50 giving a distance from 11½ to 34½ AU.


Upsilon Andromedae

Planetary system – υ Andromedae was the first main sequence star besides our sun found to have multiple planets. Their properties, based on radial velocity and astrometry, are probably as follows:

Mass (MJ)Distance (AU)Period
υ And bAt least 0.70.064.6 days
υ And cBetween 8 and 160.6 - 1.0241 days
υ And dBetween 7 and 111.8 - 3.33.5 years

There is likely also a more distant fourth planet. Unlike our near-planar solar system the orbits for planets c and d are tilted about 30° apart. The inclination of planet b is not known.

This is also likely part of a binary system as it shares its proper motion with a faint red dwarf star, υ And B, somewhere between 700 AU and 0.5 light-years away.

See McArthur et al. (2010), New Observational Constraints on the υ Andromedae System for details.


Epsilon Coronae Borealis

Planet / dwarf companion – ε Coronae Borealis has one candidate planet with an orbital period of 418 days, calculated to be about 1.2-1.4 AU from the star. The mass is not known but is at least 6½ MJ.

See Lee et al. (2012), A planetary companion around the K giant ε Corona Borealis for details.


Kappa Andromedae

Dwarf companion – κ Andromedae has a brown dwarf companion detected in infrared about 1” away, with spectral type L1. Models based on age suggest a mass between 13 and 30 MJ.

See Jones et al. (2016), The Age of the Directly-Imaged Planet Host Star κ Andromedae and Todorov et al. (2016), The Water Abundance of the Directly Imaged Substellar Companion κ And b for details.


Gamma Doradus

This is the archetype of the γ Doradus variables, whitish stars with very small non-radial pulsations. It is also surrounded by a debris disk extending about 120 AU from the star.


Psi-1 Aquarii

Multiple; planet / dwarf companion – ψ¹ or 91 Aquarii is part of a triple system, sharing proper motion with a faint pair of stars 50” away:

MagnitudeSpectrum
A = ψ¹ Aqr4.25K0III
GJ 893.2 B9.9K6
GJ 893.2 C10.1

There is also a candidate planet with an orbital period of 182 days around the main star, calculated to circle about 0.7 AU from it. The mass is not known but is at least 3.2 MJ.

The B-C pair have an orbital period of 84 years, with apparent separation varying from about 0 to ½”. The true orbit has a=0.47”, e=0.45 giving a distance from 13 - 38 AU.

See Mitchell et al. (2013), A brown dwarf and a planet orbiting the K giant stars τ Gem and 91 Aqr for details.


82 Eridani

Planetary system – 82 Eridani has three relatively small planets detected by radial velocity, with properties reported as follows:

Mass (MJ)Distance (AU)Period
82 Eri bAt least 0.0080.1218 days
82 Eri cAt least 0.0070.2040 days
82 Eri dAt least 0.0150.3590 days

The inclinations and so masses are not known, but they are apparently lighter than other gas giants, and potentially might be larger rocky planets.

See Pepe et al. (2011), Very low-mass planets around HD20794, HD85512 and HD192310 for details.


Eta Corvi

η Corvi is surrounded by a debris disk extending about 100 AU from the star.


36 Ophiuchi

Binary – 36 Ophiuchi is a visual binary with two stars of magnitude 5.1, separated by about 5” and slowly widening. There may also be a spectroscopic or common proper motion companion.


Sigma Persei

Planet / dwarf companion – σ Persei has a companion planet or brown dwarf with an orbital period of 1.6 years, calculated to be about 1½-2½ AU from the star. The mass is not known but is at least 5½ MJ.

See Lee et al. (2014), Planetary companion in K giant σ Persei for details.


HD 60532

Planetary system – HD 60532 has two candidate planets in a stable resonance with a 3:1 ratio in period. Their properties, based on radial velocity and astrometry, are as follows:

Mass (MJ)Distance (AU)Period
HD 60532 bAt least 1.00.5 - 1201½ days
HD 60532 cAt least 2.51.5 - 1.61.66 years

The inclinations are uncertain, but the most likely are co-planar orbits seen about 20° from face-on. This would give masses around 3 and 7½ MJ.

See Laskar & Correia (2009), HD 60532, a planetary system in a 3:1 mean motion resonance for details.


G Canis Minoris

Planet / dwarf companion – G Canis Minoris or HD 66141 has a candidate planet with a period of 1.3 years, calculated to be about 1.1-1.3 AU from the star. The mass is not known but is at least 5½ MJ.

See Lee et al. (2012), Detection of an exoplanet around the evolved K giant HD 66141 for details.


Tau Geminorum

Dwarf companion – τ Geminorum has a brown dwarf companion with an orbital period of 306 days, calculated to be 1.1-1.2 AU from the star. The mass is not known but is at least 20 MJ.

See Mitchell et al. (2013), A brown dwarf and a planet orbiting the K giant stars τ Gem and 91 Aqr for details.


Omicron-2 Eridani

Multiple with dwarf – ο² or 40 Eridani is a visual triple with a faint pair of companions about 28” away. These are a brighter white dwarf, the first discovered, and a red flare star, also called DY Eridani.

MagnitudeSpectrum
ο² Eri A4.4K1V
ο² Eri B9.5DA
ο² Eri C11dM4

The B-C pair has a very slow orbit around the main star. Their apparent separation varies from 2 to 9” with a period of 250 years, and their true orbit has a=7”, e=0.4 giving a distance from about 20 to 50 AU.

This star is sometimes called Keid from Arabic al qaiḍ, the eggshells, originally applied to several stars in an asterism called the ostrich’s nest.


Epsilon Reticuli

Binary with dwarf; planetary companion – ε Reticuli has one known planet with an orbital period of 1.2 years. There is also a faint white dwarf that shares its proper motion.

These two stars are about 13” apart. There has been no sign of relative motion since the discovery of the companion, which suggests that any orbital motion is seen edge-on.

The planet is calculated to have a nearly circular orbit about 1½ AU from the main star. Its mass is at least 1.6 MJ, and is not much more if it also has an edge-on orbit. Limits to inclination place it below 14 MJ.

Note the main star is somewhere between a subgiant and giant, listed as one or the other in different sources.

See Butler et al. (2006), Catalog of Nearby Exoplanets, Reffert & Quirrenbach (2011), Mass constraints on substellar companion candidates, and Farihi et al. (2011), Evolutionary Constraints on the Planet-Hosting Subgiant ε Reticulum for details.


Tau Boötis

Binary; planetary companion – τ Boötis is a binary with a faint M2V companion. There is also a planet with an orbital period of 3.31 days around the brighter star, calculated to be only 0.05 AU apart.

This star rotates with about the same period so is probably in a tidal lock with its smaller partner. Limits to inclination, based on detected planetary carbon monoxide, place its mass between 5 and 6½ MJ.

The two stars have magnitudes about 4.5 and 11, though the former is slightly variable. The apparent separation has narrowed to less than 1”, with a period of centuries and distance of perhaps 20-400 AU.

See Rodler et al. (2012), Weighing The Non-Transiting Hot Jupiter τ Boo b for details.


Xi Boötis

Binary – ξ Boötis varies in magnitude from 4.5 to 4.75 as it rotates, so changing in brightness by about 1.1 times, with a period of 10.1 days. It is also a visual binary with a K4V companion of magnitude 6.8.

The apparent separation varies from 2 to 7” with a period of 150 years. The true orbit has a=4.9”, e=0.51 giving a distance from 16 to 50 AU.


g Lupi

g Lupi is surrounded by a debris disk extending about 100 AU from the star.


Chi Virginis

Planet / dwarf companion – χ Virginis has a companion planet or brown dwarf with an orbital period of 2½ years, calculated to be perhaps 2-3 AU from the star. The mass is not known but is at least 10 MJ.

Some uncertainty here comes from what may be a closer planet or a cooler spot on the star. If the former it would have a period of 130 days, so about ½ AU from the star, with mass at least 2½ MJ.

See Soto et al. (2015), Discovery of new planetary candidates and updated orbits from archival FEROS specta for details.


Epsilon Indi

Dwarf companions – ε Indi is accompanied by two brown dwarfs, the nearest to the sun. These form a close pair 6.7’ away from the main star, with relatively cool spectral types T1 and T6.


Eta-2 Hydri

Planet / dwarf companion – η² Hydri has one candidate planet with an orbital period of 1.7 years, calculated to be about 1.3-2.5 AU from the star. The mass is not known but is at least 6 MJ.

See Soto et al. (2015), Discovery of new planetary candidates and updated orbits from archival FEROS specta for details.


Delta Scuti

This is the archetype of the δ Scuti type variables, whitish stars undergoing small but rapid fluctuations with multiple periods. These are common though most only vary a few hundredths of a magnitude.

δ Scuti itself has less subtle variations from magnitude 4.6 to 4.8, so changing in brightness by about 1.2 times. The most notable variations have periods of 4.65 hours and 4.48 hours.


Xi Aquilae

Planet / dwarf companion – ξ Aquilae has one candidate planet with an orbital period of 137 days, calculated to be about 0.6 AU from the star. The mass is not known but is at least 2 MJ.

See Sato et al. (2008), Planetary Companions around Three Intermediate-Mass G and K Giants and Kunitomo et al. (2011), Planet Engulfment by ~1.5-3 Solar-Mass Red Giants for details.


11 Comae Berenices

Dwarf companion – 11 Comae Berenices has a brown dwarf companion with an orbital period of 326 days, calculated to be 1-1½ AU from the star. The mass is not known but is at least 16 MJ.

See Liu et al. (2008), A Substellar Companion to the Intermediate-Mass Giant 11 Comae and Kunitomo et al. (2011), Planet Engulfment by ~1.5-3 Solar-Mass Red Giants for details.


61 Virginis

Planetary system – 61 Virginis has three relatively small planets detected by radial velocity, with properties reported as follows:

Mass (MJ)Distance (AU)Period
61 Vir bAt least 0.0160.054.2 days
61 Vir cAt least 0.060.238 days
61 Vir dAt least 0.070.3 - 0.6123 days

The inclinations and so masses are uncertain, but the eccentricities agree with a tidally-fixed configuration of coplanar orbits. This at least suggests b should have strong tidal friction typical of rocky planets.

There is also an outer debris disk detected in infrared, preliminarily given from about 100 to 200 AU out. This is one of relatively few nearby disks found around older stars.

See Vogt et al. (2010), A Super-Earth and Two Neptunes Orbiting the Nearby Sun-like Star 61 Virginis for details.


Kappa Coronae Borealis

Planetary system – κ CrB has one or two candidate planets. The closer has an orbital period of 3.5 years, calculated to be about 2½-3 AU from the star. A smaller may be present with at least twice the period.

There is also a debris disk around 20 to 220 AU or possibly divided into belts, seen near 60° from face-on. The closer planet has mass at least 2-3 MJ and if it orbits in this same plane is not appreciably more.

See Bonsor et al. (2013), Spatially Resolved Images of Dust Belt(s) Around the Planet-hosting Subgiant κ CrB for details.