Printer Friendly

Stars and constellations.

Patterns in the night sky

The sky is divided into 88 areas or constellations, whose names and boundaries were officially agreed on in a 1930 resolution of the International Astronomical Union. The constellation names are Latin, although several are derived from Greek. Table 15 lists all the constellations that can be seen from southern Africa.

Many of the constellation names are ancient, at least 2,000 years old and, in some cases, more than 4,000 years old. Among the oldest are the constellations of the zodiac, a band of stars along the ecliptic through which the Sun, Moon and planets move. Early stellar cartographers relied on mariners' accounts of the southern sky when inventing constellations that could not be seen from the north. It was only in the early 1750s, when the French astronomer La Caille visited Cape Town, that the southern sky was properly charted. He outlined and named many new constellations with names that are still used today. One of his creations, Mensa, is the only constellation that denotes a specific terrestrial object: Table Mountain, on the Cape Peninsula.

Within each constellation, the brighter stars are assigned letters of the Greek alphabet (Table 14). Most of the brightest stars also have their own names, usually of Arabic origin. For example a Canis Majoris, otherwise known as Sirius, is the brightest star in Canis Major. Table 16 (p 90) lists the brightest stars visible from southern Africa.

Crux, the Southern Cross

The Southern Cross has found its way into the heraldic consciousness of a number of southern nations. In Australia, Crux appears on several state flags and badges, including the national flag, which accurately depicts all five stars. The national flag of New Zealand also shows Crux, as four red stars, edged with white. Alpha is slightly larger, and delta slightly smaller, than the other two stars, in an attempt to reflect their differing apparent magnitudes. The unofficial flag of Christmas Island accurately depicts Crux, while the flags of Samoa and Papua New Guinea show a somewhat distorted figure. The national flag and arms of Brazil also include Crux.

Crux also appears on the coins of a number of countries (for some reason, coins of the northern hemisphere tend not to depict constellations). Brazilian, Australian and Western Samoan coins depict Crux (including e Crucis) accurately. Several New Zealand coins show the Southern Cross rather crudely as four stars in a symmetrical pattern.

Oddly, Crux has made no impact on southern African heraldry, which employs more earthbound symbols. Nevertheless, it does feature in the star-lore of the region. Some Bushmen knew the stars of Crux as "the giraffes", because these stars "are big, like giraffes". The /Xam Bushmen knew the Pointers ([alpha] and [beta] Centauri) as male lions, and the three brightest stars in Crux as female lions. In Sotho and Tswana tradition, [alpha] and [beta] Crucis, together with the Pointers, made up Dithutlwa, the four giraffes.

The lives and deaths of stars

A star begins its life by condensing out of the tenuous material making up a nebula--a vast cloud of (mainly) hydrogen gas. As its mass increases, a non-luminous globule is formed, which appears dark when seen silhouetted in front of the glowing nebula. Gravity causes the protostar to shrink, and the gravitational energy lost by the inflowing matter turns into heat, causing the centre of the globule to become very hot. When the temperature is sufficiently high, nuclear reactions start and the new star eventually starts to emit light.

If the protostar has a mass less than about one-tenth of a solar mass, the core never becomes hot enough for nuclear reactions to take place, and the still-born star will merely glow feebly for a very long time before losing all its energy.

If, on the other hand, the protostar has a mass between one-tenth and 1.4 solar masses, it continues to shrink and its temperature rises. At this stage its behaviour is rather erratic and it fluctuates irregularly, blowing away its original cocoon of gas and dust through a strong stellar wind that develops. This is known as the T Tauri stage, which lasts for several million years.

Meanwhile, the temperature in the core increases, and once it reaches about 10 million degrees, nuclear reactions are triggered. In the process, hydrogen is converted into helium, and the star is said to be in the main sequence phase.

For thousands of millions of years these reactions continue until the supply of hydrogen begins to run low. At the core, the star starts to use up helium to produce carbon, while the remaining hydrogen, in a shell around the hot core, continues to produce energy. Eventually the star becomes unstable and its outer layers expand and cool; it has become a red giant. The star then begins to "dissolve" as its outer layers are thrown off, creating the beautiful and varied objects called (misleadingly) planetary nebulae. Finally, when the outer layers have drifted off into space, the original core is all that remains, consisting of material incredibly tightly packed together into what is known as a white dwarf. A single teaspoonful of white dwarf matter would weigh about 5 tons. The white dwarf continues to radiate its stored energy into space for billions of years, ending up as a cold, dead, black dwarf.

Live fast, die young: the story of stellar evolution

The lifetime of a star depends (mainly) on its initial mass. The more massive the star is, the hotter and brighter it will become but with a correspondingly shorter lifespan. The table shows the relationship between stellar mass (measured in units of solar mass) and lifetime (in years), and gives examples of such stars (designation and spectral type).

If the original protostar is more massive than 1.4 times the Sun, its evolution is far more rapid and energetic. In the core, temperatures become so high that nuclear reactions create elements heavier than carbon. Eventually, the core consists mainly of iron, at which point the nuclear furnace has reached its limit. The star suddenly and catastrophically collapses, followed by an enormous explosion known as a supernova outburst. This outburst is so bright that for a short while the supernova outshines its entire host galaxy! Most of the star's material is violently ejected into space during the explosion, leaving a tiny super-dense core made up only of neutrons. A teaspoonful of neutron star stuff weighs about 5 million million tons.

Truly massive protostars also end their lives in a supernova outburst, but their heavier cores collapse even further to create a black hole, an ultra-compact mass from which not even light can escape.

For the record

* The first comprehensive catalogue of southern stars was compiled in Cape Town by Abbe de La Caille and published in 1763. He also outlined and named 14 new constellations, still in use today. The constellation Mensa, originally called Mons Mensa by La Caille, is named after Cape Town's Table Mountain. It is the only constellation named after a terrestrial feature.

* The first stellar distance measurement (using the parallax method) was made in Cape Town by Thomas Henderson in 1832. He showed that <x Centauri was the nearest star to the Sun. In 1915, R T A Innes discovered this star's dim companion, Proxima Centauri, which turned out to be even closer.

* Measuring the amount of light received from a star (photometry) has been an ongoing undertaking for astronomers in South Africa. The first visual photometry was carried out in 1833 by Sir John Herschel while at the Cape. In the 1940s and 1950s AW J Cousins and R H Stoy did groundbreaking work in setting photometric standards; subsequent photometric work by Cousins is of fundamental significance to all photometry worldwide and is therefore also fundamental to measuring distances in the Universe.

Pronouncing star names

Today's star names derive from a variety of past cultures, mostly from the Middle East and the Mediterranean. Since medieval times (500 CE to 1500 CE) they have been jumbled up and passed down to us in Latinized form.

The most ancient names have Sumerian and Babylonian roots, which influenced the stellar nomenclature of the ancient Greeks (well-established by 800 BCE). Babylonian astronomy and astrology influenced the Greeks down to the Hellenistic period, to as late as 100 CE to 200 CE. In turn, the Greeks passed on a portion of their star lore and nomenclature to the Romans.

The Bedouin, desert nomads of the Arabic peninsula, were another rich source of ancient star names, giving us some of the oldest known names such as Aldebaran, Rigel, and Vega.

Some 70% of star names in use today are Arabic in origin and about 20% are Greek or Latin, with the remainder either rooted in Persian, Hebrew, or Turkish, or fabricated (typically during the Renaissance).

The adjacent table gives, for each selected star, a guide to pronouncing its name near to how it would have been spoken in its native tongue.

African star lore

* The /Xam Bushmen considered Sirius to be "the grandmother of Canopus" since Sirius rises after Canopus, just as the elderly follow behind the more agile youths. Aldebaran was seen as a male hartebeest, and Betelgeuse as its mate. Procyon was a male eland and Castor and Pollux represented his wives.

* The Pleiades (M 45, Seven Sisters) was commonly observed by peoples throughout Africa. For the Xhosa, the dawn rising of the Selimela was a traditional indicator of male coming-of-age. The Sotho and Tswana call it Selemela, and the Zulu isiLimela, who believed that these stars die in winter dusk and are reborn in the rainy season (the Pleiades reappear in the evening sky in October). A Khoikhoi myth tells how the !Khunuseti (Pleiades) once sent their husband (Aldebaran) to shoot three zebras (Orion's belt), but if he failed, he was not to return. He went with one arrow, and shot with his bow, but missed. He couldn't retrieve the spent arrow (Orion's sword) because it fell near a lion (Betelgeuse) who was also watching the zebras. So the poor man stayed out in the cold veld, too frightened to return home.

* Canopus: The second brightest star in the night sky is known as inKwenkwezi in Zulu and U-Canzibe in Xhosa. North Sotho villagers traditionally kept an early-morning watch for the first dawn rising of Naka, their name for Canopus. The man who saw it first was awarded a cow by the chief. The appearance of Naka marked the beginning of the dry season, a time of war, initiation ceremonies, rainmaking rituals and divination. The Xhosa Ikhwezi, Zulu iKhweziand Sotho-Tswana nalediya masa all refer to the "morning star", which "is for counting the years of manhood", and is believed to be another name for Canopus.

Double stars

Single stars, such as our Sun, are the exception. The majority of stars are double (or multiple) and are gravitationally bound with component suns that move in elliptical orbits around common centres of mass. Some stars that seem to be located next to one another as seen from Earth, are not physically related and appear double only because of perspective; these are known as "optical doubles". Long-term observation of a true double star allows its orbit to be calculated, which in turn provides an opportunity for the masses of the stars to be determined. This knowledge is essential in the testing of theories of stellar evolution.

Visual double stars are among the easiest of all astronomical objects to observe. A well-equipped observatory and large telescope is not required. There are thousands of visual double stars that are within the range of small telescopes. Double stars can also be easily observed from locations suffering from moderate light pollution.

There are many so-called "neglected" double stars that need to be confirmed. The only special instrumentation needed is an eyepiece to which a cross-hair has been fitted. For more serious work, some means of accurately measuring the position angle and angular separation between the two stars is needed. Further details are available from the Double Stars group of the Deep-Sky Observing Section (see p 113 for contact details).

Variable stars

Variable stars are stars that change brightness (most stars--including the Sun--vary in brightness if measured accurately). By studying their behaviour, much can be learnt about their physical properties such as size, mass, luminosity, temperature, structure, composition and evolution. This information can then be used to understand other stars.

Over 150,000 variable stars are known and many thousands more are suspected to be variable. Professional astronomers are not able to gather data on the brightness changes of thousands of variable stars; there are simply too many stars, and too few resources. Amateur astronomers, using visual, photographic, photoelectric and CCD techniques, can make significant contributions to science by observing these stars. Some 2,000 variables are suitable for visual monitoring in the southern hemisphere.

Visual estimates of magnitude are made by comparing the variable with two or more comparison stars, respectively brighter and fainter than the unknown variable. Suitable comparison stars are shown on special charts, which have been prepared for each variable star. The use of these charts is essential for accurate, standardized observations and intending new observers are therefore advised to obtain the necessary data by contacting the Variable Stars group of the Deep-Sky Observing Section (see p 113 for contact details).

The observed brightness estimates are used to generate light curves and are made available to a large number of professional observatories where astronomers are interested in investigating certain properties of the stars more fully.

Amateur observers also play an invaluable role by alerting the operators of orbiting satellite observatories whenever outbursts of certain eruptive variables are seen to occur, so that the orbiting observatories can be trained on the outburst for detailed study.

For the record

* Early variable star observers in southern Africa included A W Roberts**, J F Skjellerup (1917-1923), A W Long (1919-1927), H E Houghton (1919-1942), W H Smith (1922-1931) and G E Ensor (1924-1938). In later years, prolific observers included R P de Kock (1940-1974)*,

A W J Cousins (1936-1947), T H Bicknell (1945-1965), S C Venter (1947-1965), M D Overbeek (1951-2001)**, T P Cooper (1984+), J Hers (1976+), J A Smit (1986+), R W Jones (1988+), and L A G Monard (1995+). A single asterisk denotes over 100,000 observations; a double asterisk denotes over 200,000 observations.

* A bright naked-eye nova in Pictor was discovered on 1925 May 25 by R Watson, an amateur astronomer living in Beaufort West. He promptly alerted the Cape Observatory, enabling Harold Spencer Jones to obtain a series of spectra with the McClean telescope as the nova faded.

* A D Thackeray discovered RR Lyrae variables in the Magellanic Clouds. This provided direct confirmation that there was something wrong with the calibration of the cosmic distance scale and hence the age of the Universe. He, in effect, doubled cosmic distances. Subsequently they have been increased by a further factor of about four.

* A W J Cousins, after observing variables for 30 years as an amateur astronomer, turned professional and did ground-breaking work in photometry. In 1992 he discovered the y Doradus class of variables.

Mass   Lifetime        Example

40.0   1 million       zeta Pup (O5)
18.0   7 million       phi-1 Ori (B0)
6.5    90 million      pi And-A (B5)
3.2    500 million     alpha CrB-A (A0)
2.1    2 billion       beta Pic (A5)
1.3    5 billion       eta Ari (F5)
1.0    10 billion      Sun (G2)
0.7    30 billion      61 Cyg-A (K5)
0.5    70 billion      Gliese 185 (M0)
0.2    500 billion     EZ Aqr-A (M5)
0.1    3 000 billion   Van Biesbroeck (M8)

Table 14. Greek alphabet

[alpha]     alpha
[beta]      beta
[gamma]     gamma
[delta]     delta
[epsilon]   epsilon
[zeta]      zeta
[eta]       eta
[theta]     theta
[iota]      iota
[kappa]     kappa
[lambda]    lambda
[mu]        mu
[nu]        nu
[xi]        xi
[omicron]   omicron
[pi]        pi
[rho]       rho
[sigma]     sigma
[tau]       tau
[upsilon]   upsilon
[phi]       phi
[chi]       chi
[psi]       psi
[omega]     omega

Table 15. Constellations visible from southern Africa

Constellation (English name)         Abbr    Culm

Andromeda (Chained Maiden)           And    Sep 30
Antlia (Air Pump)                    Ant    Feb 22
Apus (Bird of Paradise)              Aps    May 21
Aquarius (Water Bearer)              Aqr    Aug 26
Aquila (Eagle)                       Aql    Jul 12
Ara (Altar)                          Ara    Jun 12
Aries (Ram)                          Ari    Oct 20
Auriga (Charioteer)                  Aur    Dec 09
Bootes (Herdsman)                    Boo    Apr 30
Caelum (Engraving Tool)              Cae    Nov 30
Cancer (Crab)                        Cnc    Jan 30
Canes Venatici (Hunting Dogs)        CVn    Apr 07
Canis Major (Big Dog)                CMa    Jan 01
Canis Minor (Little Dog)             CMi    Jan 14
Capricornus (Sea Goat)               Cap    Aug 05
Carina (Keel of the Ship)            Car    Jan 30
Centaurus (Centaur)                  Cen    Apr 06
Cetus (Sea Monster)                  Cet    Oct 15
Chamaeleon (Chameleon)               Cha    Feb 28
Circinus (Compass)                   Cir    May 01
Columba (Dove)                       Col    Dec 17
Coma Berenices (Berenice's Hair)     Com    Apr 02
Corona Australis (Southern Crown)    CrA    Jun 30
Corona Borealis (Northern Crown)     CrB    May 20
Corvus (Crow)                        Crv    Mar 28
Crater (Cup)                         Crt    Mar 12
Crux (Southern Cross)                Cru    Mar 30
Cygnus (Swan)                        Cyg    Jul 29
Delphinus (Dolphin)                  Del    Jul 31
Dorado (Swordfish)                   Dor    Dec 07
Equuleus (Little Horse)              Equ    Aug 09
Eridanus (River)                     Eri    Nov 10
Fornax (Chemical Furnace)            For    Nov 04
Gemini (Twins)                       Gem    Jan 04
Grus (Crane)                         Gru    Aug 29
Hercules (Hercules)                  Her    Jun 13
Horologium (Pendulum Clock)          Hor    Nov 24
Hydra (Water Snake)                  Hya    Feb 09
Hydrus (Small Water Snake)           Hyi    Oct 26
Indus (Indian)                       Ind    Aug 13
Lacerta (Lizard)                     Lac    Aug 28
Leo (Lion)                           Leo    Mar 01
Leo Minor (Lesser Lion)              LMi    Feb 24
Lepus (Hare)                         Lep    Dec 13
Libra (Scales)                       Lib    May 09
Lupus (Wolf)                         Lup    May 09
Lynx (Lynx)                          Lyn    Jan 20
Lyra (Lyre)                          Lyr    July 02
Mensa (Table Mountain)               Men    Dec 13
Microscopium (Microscope)            Mic    Aug 04
Monoceros (Unicorn)                  Mon    Jan 05
Musca (Fly)                          Mus    Mar 31
Norma (Carpenter's Square)           Nor    May 21
Octans (Octant)                      Oct    --
Ophiuchus (Serpent Bearer)           Oph    Jun 11
Orion (Orion)                        Ori    Dec 26
Pavo (Peacock)                       Pav    Jul 13
Pegasus (Winged Horse)               Peg    Sep 01
Perseus (Perseus)                    Per    Nov 07
Phoenix (Phoenix)                    Phe    Oct 05
Pictor (Painter's Easel)             Pic    Dec 15
Pisces (Fishes)                      Psc    Sep 27
Piscis Austrinus (Southern Fish)     PsA    Aug 25
Puppis (Stern of the Ship)           Pup    Jan 09
Pyxis (Mariner's Compass)            Pyx    Feb 03
Reticulum (Reticle)                  Ret    Nov 19
Sagitta (Arrow)                      Sge    Jul 17
Sagittarius (Archer)                 Sgr    Jul 05
Scorpius (Scorpion)                  Sco    Jun 03
Sculptor (Sculptor's Workshop)       Scl    Sep 27
Scutum (Shield)                      Sct    Jul 01
Serpens (Serpent)                    Ser    Jun 21
Sextans (Sextant)                    Sex    Feb 21
Taurus (Bull)                        Tau    Nov 30
Telescopium (Telescope)              Tel    Jul 06
Triangulum (Triangle)                Tri    Oct 23
Triangulum Australe (S. Triangle)    TrA    May 22
Tucana (Toucan)                      Tuc    Sep 17
Ursa Major (Great Bear)              UMa    Mar 11
Vela (Sails of the Ship)             Vel    Feb 11
Virgo (Maiden)                       Vir    Apr 12
Volans (Flying Fish)                 Vol    Jan 18
Vulpecula (Fox)                      Vul    Jul 26

Key: Abbr: Official three-letter abbreviation. Culm:
Date of midnight culmination.

Table 16. The brightest stars

Star                                        RA (J 2015.5) Dec

[alpha] Eri, Achernar              01h38m17s   -57[degrees]09' 29'
[alpha] Tau, Aldebaran             04 36 49    +16 32 24
[beta] Ori, Rigel                  05 15 17    -08 11 05
[gamma] Ori, Bellatrix             05 25 58    +06 21 46
[beta] Tau, Al Nath                05 27 17    +28 37 12

[epsilon] Ori, Alnilam             05 37 00    -01 11 35
[alpha] Ori, Betelgeuse            05 56 01    +07 24 31
[beta] CMa, Mirzam                 06 23 23    -17 57 52
[alpha] Car, Canopus               06 24 18    -52 42 18
[gamma] Gem, Alhena                06 38 36    +16 23 06

[alpha] CMa, Sirius                06 45 50    -16 43 59
[epsilon] CMa, Adhara              06 59 14    -28 59 39
[delta] CMa, Wezen                 07 09 01    -26 25 08
[alpha] Gem, Castor                07 35 35    +31 51 13
[alpha] CMi, Procyon               07 40 07    +05 11 19

[beta] Gem, Pollux                 07 46 16    +27 59 16
[[gamma].sup.2] Vel, Regor         08 10 01    -47 22 59
[epsilon] Car, Avior               08 22 50    -59 33 36
[delta] Vel, Koo She               08 45 08    -54 45 55
[beta] Car, Miaplacidus            09 13 22    -69 46 54

[alpha] Hya, Alphard               09 28 21    -08 43 36
[alpha] Leo, Regulus               10 09 12    +11 53 27
[[alpha].sup.1] Cru, Acrux         12 27 28    -63 11 06
[gamma] Cru, Gacrux                12 32 02    -57 11 56
[beta] Cru, Mimosa                 12 48 38    -59 46 23

[alpha] Vir, Spica                 13 26 01    -11 14 30
[beta] Cen, Hadar                  14 04 56    -60 26 49
[alpha] Boo, Arcturus              14 16 23    +19 06 40
[[alpha].sup.2] Cen, Rigel Kent    14 40 48    -60 54 06
[[alpha].sup.1] Cen, Rigel Kent    14 40 47    -60 54 05

[alpha] Sco, Antares               16 30 22    -26 27 54
[alpha] TrA, Atria                 16 50 19    -69 03 14
[lambda] Sco, Shaula               17 34 40    -37 06 49
[theta] Sco, Sargas                17 38 26    -43 00 22
[epsilon] Sgr, Kaus Aust.          18 25 12    -34 22 32

[alpha] Lyr, Vega                  18 37 28    +38 47 51
[alpha] Aql, Altair                19 51 32    +08 54 31
[alpha] Pav, Peacock               20 26 52    -56 41 01
[alpha] Gru, Alnair                22 09 12    -46 53 05
[alpha] PsA, Fomalhaut             22 58 30    -29 32 21

Star                               V       B-V     d

[alpha] Eri, Achernar              +0.46   -0.16   140
[alpha] Tau, Aldebaran             +0.85   +1.54   67
[beta] Ori, Rigel                  +0.12   -0.03   860
[gamma] Ori, Bellatrix             +1.64   -0.22   245
[beta] Tau, Al Nath                +1.65   -0.13   130

[epsilon] Ori, Alnilam             +1.7    -0.19   1 340
[alpha] Ori, Betelgeuse            +0.5    +1.85   570
[beta] CMa, Mirzam                 +1.98   -0.23   500
[alpha] Car, Canopus               -0.72   +0.15   309
[gamma] Gem, Alhena                +1.93   +0.00   105

[alpha] CMa, Sirius                -1.46   +0.00   8.6
[epsilon] CMa, Adhara              +1.5    -0.21   405
[delta] CMa, Wezen                 +1.84   +0.68   1 800
[alpha] Gem, Castor                +1.98   +0.03   51
[alpha] CMi, Procyon               +0.38   +0.42   11.5

[beta] Gem, Pollux                 +1.14   +1.00   34
[[gamma].sup.2] Vel, Regor         +1.78   -0.22   1 200
[epsilon] Car, Avior               +1.86   +1.28   630
[delta] Vel, Koo She               +1.96   +0.04   80
[beta] Car, Miaplacidus            +1.68   +0.00   111

[alpha] Hya, Alphard               +1.98   +1.44   177
[alpha] Leo, Regulus               +1.35   -0.11   79
[[alpha].sup.1] Cru, Acrux         +1.33   -0.24   325
[gamma] Cru, Gacrux                +1.63   +1.59   88
[beta] Cru, Mimosa                 +1.25   -0.23   280

[alpha] Vir, Spica                 +0.98   -0.23   250
[beta] Cen, Hadar                  +0.61   -0.23   392
[alpha] Boo, Arcturus              -0.04   +1.23   37
[[alpha].sup.2] Cen, Rigel Kent    +1.33   +0.88   4.36
[[alpha].sup.1] Cen, Rigel Kent    -0.01   +0.71   4.36

[alpha] Sco, Antares               +0.96   +1.83   550
[alpha] TrA, Atria                 +1.92   +1.44   415
[lambda] Sco, Shaula               +1.63   -0.22   365
[theta] Sco, Sargas                +1.87   +0.40   272
[epsilon] Sgr, Kaus Aust.          +1.85   -0.03   143

[alpha] Lyr, Vega                  +0.03   +0.00   25
[alpha] Aql, Altair                +0.77   +0.22   16.7
[alpha] Pav, Peacock               +1.94   -0.20   183
[alpha] Gru, Alnair                +1.74   -0.13   101
[alpha] PsA, Fomalhaut             +1.16   +0.08   25

The table lists, in RA order, all stars brighter than magnitude
+2.0 and south of declination +40[degrees]. Key: RA, Dec: Epoch
J2015.5. V: apparent (visual) magnitude. B-V: colour index;
red stars have positive values. d: distance, in light years.

Table 17. Pronunciation of star names

Star             Pronunciation


Key to pronunciation symbols

a (long) "arm", "father"
e (short) "end", "best"
e (long) "cafe", "Andre"
e (long) "even", "we"
I (short) "it", "pin"
o (short) "offer", "dog"
o (long) "beau", "Bordeaux"
u (short) "much", "come"
u (long) "clue", "noon"
u (short) "put", "good"

Origin of the name: (1) = Arabic, (2) = Greek,
(3) = Renaissance Latin

Source: Kunitzsch, P. & Smart, T. (2006) A Dictionary of Modern
Star Names. Sky Publishing, Cambridge, Massachusetts.
COPYRIGHT 2015 Astronomical Society of Southern Africa
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2015 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Sky Guide Africa South
Geographic Code:60AFR
Date:Jan 1, 2015
Previous Article:Meteors.
Next Article:Deep-sky.

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters