Starry, starry night
Paint your palette blue and grey
Look out on a summer's day
With eyes that know the darkness in my soul
– 'Vincent' by Don McLean, singer/songwriter
The brightest stars viewed from Earth (excluding the Sun) were noted by people in antiquity and were used to assist sailors on sea voyages. Some of the stars of the original 48 constellations put together by astronomer Ptolemy (c90–168 AD) in his treatise Almagest, provoked myths and stories which gained them legendary status. Vega, in particular, was worshipped by some cultures who thought it marked the entrance to Heaven. Although Vega wasn't the brightest star, it was used as the starting point against which all other stars' brightness was measured. Those dimmer than Vega were given a plus (+) score magnitude, while those few brighter than Vega were registered in the negative (-). The brightest of these well-known stars are referred to as 1st magnitude, and all are named (most have several names). Some astronomy texts mark 1st magnitude stars by printing their names in block capital letters.
The human eye can detect a star as dim as 6th magnitude, which is about 100 times fainter than a 1st magnitude star, and the dimmest stars registered by Hipparchus (c190 BC–120 BC), Ptolemy's precursor, but that was in the good old days before light pollution. French astronomer Charles Messier was clocking up distant galaxies1 as dim as +10 mag for his famous list of non-comets in the 18th Century. British astronomer Sir Norman Pogson standardised the magnitude system in the 19th Century. Today, even if you have perfect eyesight, you may still need binoculars to see faint magnitude +6 stars. A good telescope would allow you to see magnitude +11 stars, which would be 100 times dimmer than magnitude +6. Meanwhile, the magnificent piece of technology that is the orbiting Hubble Space Telescope is registering the light of magnitude +30 objects at mind-boggling distances.
The Sun, the Moon and the planets are also on this magnitude scale – the greater the score in negativity, the brighter the object – thus: the Sun is -26.74 magnitude2, the full moon is -12.74 mag, Venus varies in range over her seasons but can be as bright as -4.9 mag, and Jupiter has been registered to -3.86 mag3. The Moon and the planets are not producing this light themselves, they are reflecting the Sun's light back to us, like mirrors. The light emitted by stars, however, is their own, and this is what we measure. Usually their magnitude doesn't change unless they are variable stars or something happened to the star in the meantime, such as that it went supernova.
The top ten brightest stars viewable from Earth now are listed here. Five of the ten, Sirius, Rigel, Arcturus, Procyon and Betelgeuse, can be viewed from any part of the Earth except the polar regions. Vega and Capella are well known to denizens of the Northern Hemisphere, but can still be seen over much of the Southern Hemisphere. Canopus, Rigil Kentaurus and Achernar are mainly visible from the Southern Hemisphere, although at latitudes up to as far as 29°N all three can still be seen.
Sirius, Bayer designation alpha Canis Majoris, is actually a binary system comprising a white main sequence star, Sirius A, and a dim white dwarf star, Sirius B. The apparent magnitude is -1.4, although this is variable. It is so bright because of its nearness to Earth; at 8.58 light years4 distant, Sirius, known as the 'Dog-Star', is the fifth-closest to us. An interesting geometric asterism5 is the rhombus created by connecting Sirius, Rigel, Aldebaran and Betelgeuse.
The ancient Egyptians knew Sirius as Sopdet – literal meaning 'the star of Isis'. They used the pre-dawn (heliacal) rising of Sirius to predict the flooding of the river Nile, which they called Akhet (the inundation). This was essential to all life in Egypt. They even assigned a special god to oversee this important celebration, and Sirius featured heavily in their calendar.
The ancient Dogon people, an African tribe, had knowledge of the Sirius system, including its companion star, which should have been beyond their capabilities. The Dogon claimed that extra-terrestrials, half-humanoid/half-fish creatures called the Nommo, travelled to Earth from a planet belonging to the Sirius system, and became their teachers. Dr Carl Sagan and other scientists have tried to debunk such stories, but that hasn't precluded the popularity of sci-fi novels such as the VALIS trilogy by Philip K Dick6, which featured the Nommo.
Canopus (alpha Carinae) is a white supergiant registering -0.72 mag. It is over 13,000 times more luminous, and over 60 times the size of the Sun. Its distance from our own Solar System is 310 light years.
One of the most recognised Southern Hemisphere stars to seafarers is Canopus, which shines like a beacon from the 'masthead' of the enormous group of stars which represented the immortalised ship transporting Jason and the Argonauts in their fabled search for the Golden Fleece. The first true GPS system was developed by the US Navy in 1960. Before that celestial navigation was used universally, and even today on small private craft a knowledge of the stars is considered vital in case of instrument failure.
Canopus (also 'Kanopus') in legend was King Menelaus' helmsman when the Spartans were on their way to the Trojan War. When the king became threatened by a snake, Canopus sacrificed himself to save his liege. An Egyptian seaport honours the hero Canopus by carrying the same name, and possibly the word 'canopic' stems from it when referring to the ancient Egyptian funerary equipment known as Canopic Jars, which protected the removed body organs of the deceased during the mummification ritual.
Because Canopus was so distinct and important, it was revered in many cultures, so it has garnered quite a few monikers from around the world:
- Agastya (Hindu Indian)
- Al Fahl (Bedouin)
- Atutahi (New Zealand Maori)
- Kahi Nub (Coptic Egyptian)
- Karma Rishi (Tibetan)
- Laou Jin (Chinese)
- Mera-boshi (Japanese)
- Schif-stern (German)
- Suhail (Arabian)
- Süheyl (Turkish)
- Waa (Aborigine Australian)
Canopus was thought to guide Russian pilgrims as they journeyed to visit a shrine, so they named it after their object of worship – 'the Star of Saint Catharine'.
Arcturus (alpha Boötis) is a -0.04, 1st magnitude orange giant star just 36 light years distant. It is the 3rd-brightest star in the sky overall. Arcturus means 'bear guardian' in Greek; it was known by Homer, Hesiod and Ptolemy. In this fabulous Astronomy Picture of the Day image, Arcturus is in the centre of the picture between Jupiter and 'The Plough' asterism (the most recognisable part of the constellation Ursa Major). Arcturus is quite possibly an extra-galactic star which was once part of another galaxy, long since cannibalised by the Milky Way. Astronomers suspect this because there is a tidal stream of 53 old stars, including Arcturus, which are related in some way. The stream isn't part of the Milky Way because it's on a different level. These adopted stars are collectively known as the Arcturus Stream, in their brother's honour.
Researching the historical references to Arcturus caused some bad and unlucky stories to surface. In the interests of balance, just a few will be noted here, along with a couple of good mentions.
Ancient Arabian astronomers delineated a huge lion constellation, which covered approximately a third of their visible sky. Arcturus, which they knew as Haris al-Sama (Keeper of Heaven), marked one of the great beast's shin-bones. Australian Aborigine people call the star Marpean-kurrk and it is associated with spring. While Marpean-kurrk could be seen, the aborigines knew they could search for the larva of Formica (wood ants), an important source of protein in the barren desert lands. The Inuit, indigenous people living in the frozen Arctic, must have the most spectacular views of the night sky thanks to their remoteness from light pollution. Their name for Arcturus is Uttuqalualuk, a fond name for an ancestor who watches over them. In their Latin Dictionary, Charlton T Lewis and Charles Short's entry for Arcturus claimed that ancient Romans regarded it as a harbinger of doom, and that its appearance in the night sky foretold tempestuous weather the following day. Therefore, any Roman captain worth his salt would have to be clued up on astronomy, so as not to risk losing his fleet to the elements just as they're locking oars and setting sail.
The famous poet Alexander Pope wrote about Arcturus' malignant influence (sending too much rain in spring) after farmers have toiled fields and tended seedlings, only for all the crops to rot or be washed away. In the same poem, Windsor Forest, he recounts the gory death of a beautiful pheasant – the matted blood from the wound clashes with the vivid green, purple and gold of his 'shining plumes'.
Arcturus is associated with the World's Fair held in Chicago from 1933 to 1934. Usually a famous person would be hired to engage the crowds on the opening day and start things off with a bang, but in this case Arcturus was chosen to open the event because it was thought (incorrectly) that its light had travelled the distance between it and Earth since the last Chicago World Fair in 1893. Close, but no cigar. One of the attractions was the landing of a German airship, the swastika-decorated Graf Zeppelin, on 26 October, 1933. For many American people this impressive aerial show left them uncomfortable, perhaps it even elicited a sense of foreboding – Adolf Hitler had been elected leader of the new Nazi Party and made Reichskanzler (Chancellor) of Germany just a few months previously.
4: Rigil Kentaurus/Alpha Centauri A
In those days spirits were brave, the stakes were high, men were real men, women were real women and small furry creatures from Alpha Centauri were real small furry creatures from Alpha Centauri.
– Douglas Adams' essential read The Hitchhiker's Guide to the Galaxy.
Alpha Centauri is a triple star system and the closest star system to ours, at just over 4.3 light years distance. The three stars are catalogued alpha Centauri A, B and C. Rigil Kentaurus (alpha Centauri A) has a magnitude of -0.01, making it the 4th-brightest star. However, when the combined influence of alpha Centauri B and C are taken into account, the naked-eye magnitude jumps to -0.27, which is brighter than Arcturus in this list. Therefore, for the purpose of this Entry, Rigil Kentaurus' own magnitude of -0.01 has been used.
Alpha Centauri C is better known as Proxima7 Centauri. This 11th-magnitude red dwarf star is just 4.2 light years away, making it the closest star to our Sun. At the time of writing, November 2009, no extrasolar planets have been detected in the alpha Centauri system, but that doesn't stop people from speculating.
Alpha Centauri Sci-fi
Of course, in the science-fiction genre, the nearest stars to our own insignificant yellow dwarf star have been regularly tapped for material:
There is an Alpha Centauri outpost in Star Trek.
Sid Meier's Alpha Centauri is a video game sequel set in the 22nd Century.
In the first book by Robert Silverberg, Revolt on Alpha C (published in 1955), 20-year-old Space Patrol cadet Larry Stark visits the planet Alpha Centauri IV which had been colonised by humans for over a century before Stark's birth. There's a fight for independence from Earth and dinosaurs thrown into the mix for good measure, which must have made it a popular library book since the late 1950s.
Vega is the 5th-brightest star at +0.03 magnitude. Officially catalogued alpha Lyrae, the brightest star in the constellation Lyra, it is also known by other names: Dilgan 'Messenger of Light' (Babylonian), Tir-anna 'Life of Heaven' (Akkadian), Vagieh, Veka, Wega, Waghi, and 'the Harp Star'. Vega was the North Celestial Pole Star8 (pole position is cyclical) some 12,000 years ago and will be again in another 10,000 years. The temples at Abydos and Luxor in Egypt were aligned with this star.
Vega was the first star ever to be photographed, on the night of 16 July, 1850, by American inventor John Adams Whipple (1822–1891). It is one of the three stars which forms the Summer Triangle, an asterism coined by Sir Patrick Moore, the other two stars being Deneb (alpha Cygni) and Altair (alpha Aquilae). Vega is just 25 light years away and it has a protoplanetary (dust) disc. Beta Pictoris, Fomalhaut (alpha Piscis Austrini), Sadira (epsilon Eridani) and Vega are dubbed the 'Fabulous Four' debris stars – the debris was discovered by the IRAS (Infrared Astronomical Satellite).
Vegans Roll 'n' Rock
In the sci-fi novel and film Contact by Dr Carl Sagan, the extra-terrestrial message received by Earth hails from the Lyra constellation, specifically the Vegan stellar system. The heroine of the story, Dr Ellie Arroway travels to some distant galaxy via an intergalactic wormhole routing station of sorts near Vega.
Chevrolet launched a 'Vega' model in 1971, but the star had an earlier car named after it, one of the most beautiful of the classic cars, the Facel Vega from the 1950s.
In the Star Trek universe there are many mentions of a human settlement cohabiting with native Vegans.
There is a Russian counter-terrorism unit called Vympel (Vega Group).
In the Foundation universe created by Isaac Asimov, one of the planets is called Vega.
Places which took its name are: Vega in Bulgaria; Vega in Norway; Vega in Sweden and Vega in Texas.
To the naked eye Capella flashes different colours as one watches, sparkling like a multi-coloured jewel against the black sky. The constellation Auriga's alpha star is 42 light years distant, and registers at +0.08 magnitude. The Capellan system comprises a spectroscopic double9 – a binary pair of yellow giant stars orbited by another couple of red dwarf stars, all in the same group, spread over 57 light days10. Capella is an X-ray source; in fact the beginnings of stellar X-ray astronomy can be traced back to this discovery. So far no extrasolar planets have been detected, but it doesn't take much imagination to marvel at what the view in the night sky would be like for a Capellan astronomer living on a hypothetical planet orbiting one of the red dwarfs.
Hot to Trot Capella
'Capella' means 'little she-goat' – in constellation lore it represents the goat carried by the Auriga the charioteer on his left shoulder. The Romans knew this star as Amalthea, who in legend was the wet-nurse who breastfed Jupiter11, the king of the gods. Amalthea is the name now given to one of the gas giant planet Jupiter's many moons, and it also identifies one of the Jovian rings, the Amalthea Gossamer Ring.
The Cornucopia, or 'horn of plenty', is associated with Amalthea and the legend of Jupiter's infancy. In one story he broke off a goat's horn and presented it to his wet-nurse as a reward for her service. The cornucopia was overfilled with riches – fruit and other foodstuffs, flowers and precious jewels – and what was used was replenished. Today the cornucopia has become synonymous with the American Thanksgiving Day celebration. A giant golden cornucopia, packed with weapons, food and other life-saving necessities, was the centrepiece and starting point at the commencement of the 74th annual Hunger Games in The Hunger Games by Suzanne Collins.
If one chooses to believe in astrology, the star Capella signifies wealth and honour.
Rigel is a blue supergiant registering +0.1 magnitude, the luminary star in the magnificent constellation of Orion. Being the brightest doesn't always make you top dog though; for some reason unbeknown to us, the Bayer designation for Rigel is beta Orionis – Betelgeuse has the honour of being the alpha star in this particular star grouping.
The Winter Hexagon asterism is somewhat larger than the more well-known Winter Triangle. Find Betelgeuse on Orion's shoulder then look at the bright stars encircling it; make sure you look early enough to include bright Sirius. The six stars that make up the Winter Hexagon are Capella, Castor or Pollux of Gemini, Procyon, Sirius, Rigel and Aldebaran. The arm of our Milky Way galaxy runs through the middle of the asterism (between Capella and Sirius), so the Winter Hexagon is a prominent 'shape' to distinguish from a dark-sky viewing area.
In the book and films about Ben Hur, our hero Judah Ben-Hur survives the hardship years chained to the oars of slave galleys. After he saves the life of the Roman captain Quintus Arrius, he is given his freedom and adopted into Quintus Arrius' family. This gives Judah the opportunity to return to his homeland to search for his missing mother and sister. Fate throws Judah the chance to revenge himself against his childhood friend-now-enemy, the Roman tribune Messala, when he meets the hospitable Sheikh Ilderim. The Sheikh owns four Arabian horses who are named after stars: Rigel, Antares, Aldebaran and Altair, which he treats as companions, but he is frustrated that they do not race as a team. Judah demonstrates how he would arrange the horses according to their strengths, and the Sheikh is so impressed with the improvement that he asks Judah to be the charioteer in a great chariot race. At first Judah refuses, but in the end he does accept the challenge when he finds out that Messala would also be competing. Not only does Judah win the chariot race and thereby beat Massala, he also improves Sheikh Ilderim's financial position thanks to the pre-race betting.
Alpha Canis Minoris, better known as Procyon, measures +0.3 magnitude. It was originally Prokyon in Ancient Greek; the name means 'pre-dog' because it rose just before the 'dog star' Sirius. Not only is Procyon in our list of Top Ten brightest stars, it's also the 14th-closest at approximately 11.5 light years. The system consists of a yellow-white main sequence subgiant star, Procyon A, and a white dwarf companion, Procyon B, which was detected by Arthur von Auwers in 1840. Although it could not be seen, its presence was suspected due to the optical irregularities of the main component. It was first recorded visually by John M Schaeberle in 1896. Along with Sirius and Betelgeuse, Procyon forms the Northern Hemisphere's Winter Triangle. Procyon is one of the six stars that make up the Winter Hexagon asterism; the others are Capella, Castor or Pollux, Sirius, Rigel and Aldebaran.
Being one of the 15 Behenian fixed stars, Procyon was important in ancient European and Arabic astrology. Apparently it was useful for magical purposes and understanding the work of alchemists.
Procyon has a regular showing in the science-fiction genre, here are just a couple of examples:
In Star Trek there is a blue, ringed gas giant planet called Procyon VIII which has an icy (but not too cold) moon named Andoria. The blue-skinned humanoid, semi-insectoid, white-haired, blue-blooded, antennaed Andorians are portrayed as enemy aliens who hate humans and Vulcans. However, in future recurrences over the different Trek series, including ST: Enterprise, not all of them are baddies. This is especially true for popular character Shran, a Commander in the Andorian Imperial Guard, who makes friends with Enterprise Captain Jonathan Archer and helps to bring about a new understanding between humans, Vulcans and Andorians.
Osiris, Isis and Thoth are planets belonging to the Procyon system in the Viagens Interplanetarias sci-fi stories written by Lyon Sprague de Camp. The planet Isis boasts inhabitants who have many legs and a trunk. Off-worlders who have encountered them describe Isidians as 'resembling a cross between an elephant and a dachshund' which is rather difficult to imagine; surely they meant a cross between an elephant and something much smaller but with more legs than a dog?
Achernar (alpha Eridani) is a variable blue dwarf star with an unusual spectrum. This star rotates so fast that it bulges in the middle, causing it to have a much larger diameter at its equator than from pole to pole. It's a record-breaker in so many ways; it's the fastest, hottest, bluest and flattest star on our list! Achernar lies at the southernmost end of the constellation Eridanus, with barely a degree separating it from neighbouring Hydrus, the water snake. There is a much less strange star, a white dwarf, gravitationally bound to Achernar, some 12 AUs12 distant. Together they register +0.45 magnitude.
MAR Barker (1929–2012) was the instigator of one of the very first role-playing games, Empire of the Petal Throne, but he will probably be better remembered for creating Tékumel. This work has been compared, in terms of quality, to JRR Tolkien's Middle-Earth. In the Tékumel universe, the Ahoggyá (Knobbed Ones) hail from a planet which orbits Achernar.
Achernar, Fomalhaut and Canopus represent the Tre Facelle (the three torches of Faith, Hope and Charity) in the 'Purgatorio' (Purgatory) section of La Divina Commedia, Dante Alighieri's defining work.
Betelgeuse (alpha Orionis) marks Orion the hunter's shoulder. It is a red supergiant which fluctuates between +0.4 and +0.6 magnitude. Betelgeuse is at the end of its stellar life, having used up all of its hydrogen. It's swelling big-time and will eventually blow itself apart as a Type II supernova. It is so huge that if you transplanted it in place of our Sun we wouldn't be able to admire it, because the Earth would be inside the star along with Mars, its moons, most, if not all of the Asteroid Belt, and possibly even the Jovian system. Betelgeuse could explode at any time, and from our comfortable vantage point over 600 light years distant, it will be a rare treat for modern astronomers. The visual death of Betelgeuse will be so bright and so vast that we should be able to see it during our daylight hours. This is what happened with the supernova which created the Crab Nebula almost a thousand years ago, and that was a lot further away than Betelgeuse. After its magnificent swan song, Betelgeuse will shrink to a dense white dwarf star, losing its place in our top ten brightest stars. It will have to make way for Hadar, beta Centauri. Altogether now, awww...
You do remember that the characters Ford Prefect and Zaphod Beeblebrox from The Hitchhiker's Guide to the Galaxy originally hailed from the vicinity of Betelgeuse don't you?
One of Sir Patrick Moore's pet hates is when anyone incorrectly pronounces the name of the famous star on the shoulder of Orion. He likes to mention Betelgeuse a few times a year on his TV programme The Sky At Night, just to remind everyone how it's supposed to be pronounced. Remember, it's bet-el-gerz – not 'beetle-juice'. 'Beetlejuice' is the name of a mischievous phantom who appears when you say his name three times in succession, but then he wreaks havoc and you can't get rid of him. So, remember not to say Beetlejuice three times, OK?Photograph courtesy of Masahiro Miyasaka