CRATER, the "Cup"

Chart showing the constellation.

Crater is an ancient constellation representing the goblet of Apollo, and is a companion to Corvus the Crow on the back of Hydra the Water Snake.

To find Crater look north in the evening to find the bright stars Regulus and Spica. Find the distinctive quadrilateral of Corvus, and look west to find the upside-down cup or sundae dish shape.

Chart showing Crater - as seen high to the north at about 10.00 pm (NZST) mid April.

Crater and surrounding constellations

Constellation Puppis Constellation Pyxis Constellation Antlia Constellation Corvus Constellation Virgo Constellation Bootes Coma Berenices Constellation Leo Constellation Sextans Constellation Hydra Constellation Hydra Constellation Cancer Constellation Gemini Constellation Canis Minor Constellation Monoceros

Details of some of the objects shown in the chart.

α (Alkes) is a magnitude 4.1 yellow giant star 174 light years away.

β Crt is a magnitude 4.5 blue-white star 266 years away

γ Crt is a close double star of magnitudes 4 and 9 with colours of pale yellow, and ashy. They lie about 84 light-years away.

δ Crt is a pale yellow star magnitude 3.55 and about 195 light-years away.

Visibility

Being some distance south of the celestial equator, Crater remains visible in the evening from New Zealand until August when it will be low to the west as the sky darkens after sunset.

CORVUS, the Crow   (Pronounced Kor-vus)

Chart showing the constellation.

Corvus, the Crow, is a small constellation of ancient origin, to which Ptolemy assigned seven stars. It can be recognised by four prominent stars in a trapezium shape. The fifth star α Corvi is so much less bright than the others that it may have decreased in light since Bayer lettered them in 1603.

The ancient Greeks called this constelation "the Raven".

In legend, Corvus is associated with the neighbouring constellation of Crater, the Cup, and Hydra, the Water Snake. The crow is said to have been sent by Apollo to gather water in a cup, but instead it dallied to eat figs. When the crow returned to Apollo, it carried the water snake in its claws, claiming this creature to have been the cause of the delay. Apollo, realising the lie, banished the trio to the sky, where the Crow and the Cup lie on the back of Hydra. For its misdeed the crow was condemned to suffer from eternal thirst, which is why crows croak so harshly.

In another legend, a snow-white crow brought Apollo the bad news that his lover Coronis had been unfaithful to him. In his anger, Apollo turned the crow black. Apollo and crows are closely linked in legend, for during the war waged by the giants with the gods, Apollo turned himself into a crow.

To find Corvus look north early evening and find the trapezium shape. (Use the bright star Spica in Virgo to aid orientation.)

Chart showing Corvus as seen high in the sky to the north at about 10 pm NZST in mid May.

Corvus and surrounding constellations

Constellation Crater Constellation Virgo Constellation Hydra

Details of some of the objects shown in the chart.

α Corvi, Al Chiba is a magnitude 4.0 white star 68 light years away.

β Crv, Kraz is a magnitude 2.7 yellow giant star 290 light years away.

γ Crv, Gienah is a magnitude 2.6 blue-white star 190 light years away.

δ Crv, Algorab is a wide double star 120 light years away. The brightest component visible to the unaided eye, is a magnitude 3.0 white star, that is accompanied by a magnitude 8.4 star often described as purplish in colour.

ε Crv, Minkar is a magnitude 3.0 red star, about 300 light years away and 450 times as luminous as the Sun.

NGC 4038 and NGC 4039 are called the Antennae or Rat tailed or Ring-tailed galaxies. They are two galaxies in collision, and photographs show two tails of stars ejected from the interaction. The system is a strong radio transmitter. At magnitude 10.5 a reasonable telescope and dark skies are needed to see this. The rat tails are not visible in telescopes.

NGC 4782 and NGC 4783 are also two small elliptical galaxies in contact. The similar components with bright centres, appear in a field sprinkled thinly with faint stars. Photographs show diffuse material connecting the galaxies. At magnitude 11.7 a reasonable telescope and dark skies are needed for viewing these galaxies.

NGC 4361 is a planetary nebula with a visible central star. Only the central star can be seen in small telescopes, but larger telescopes will show the haze surrounding the star. An OIII filter effects a small improvement.

Just over the border of Corvus in the constellation Virgo lies the famous Sombrero galaxy, M 104. It is a spiral galaxy with a large nucleus and a dense lane of dust lying about 35 million light years away.

Visibility

Corvus is due north and high in the sky soon after 9 pm in mid May. It remains visible for at least part of the evening until about mid September when it will ve low, to the west-south-west as the sky darkens following sunset.

Contributed by Paul Rodmell, Southland Astronomical Society

CORONA BOREALIS "the Northern Crown" and CANES VENATICI "the Hunting Dogs"
(Pronounced koh ROH-nah BOH-ree-AL-liss and KAY-neez veh-NAT-ih-sigh)

Chart showing the constellation.

Corona Borealis was known to the ancient Greeks as the "wreath". Only later was the adjective "northern" added to distinguish it from its southern counterpart. It represents the jewelled crown given as a wedding present by Bacchus to Ariadne, and cast into the sky by him, upon her death. Another legend has it as the golden crown given to Ariadne by Theseus after the quest in the labyrinth to kill the Minotaur. It is a lovely arc of 4th magnitude stars, with a second magnitude star (Gemma) set as a central gem.

Canes Venatici is a constellation introduced by the Polish astronomer Hevelius in 1690 in his great star atlas Uranometria. The sprinkling of faint stars was taken from the constellation Ursa Major, the Great Bear. It represent the dogs Asterion and Chara held on a leash by Boötes the herdsman as they pursue the Great Bear round the north pole.

To find these constellations look low to the north in the evening sky, find the bright reddish star Arcturus in Boötes and look either side. Canes Venatici is to the left (west) and the more easily seen Corona Borealis is the arc of stars to the right (east).

Chart showing Corona Borealis and Canes Venatici.

The chart shows the sky to the north at about 11.30 pm (NZST) in mid May or 9.30 pm mid June. The horizon shown is for central New Zealand.

Corona Borealis and Canes Venatici Constellation Serpens Constellation Ophiuchus Constellation Hercules Constellation Bootes Constellation Virgo Coma Berenices

Some stars and interesting objects in the Constellations

α Coronae Borealis (Gemma or Alphecca) is a magnitude 2.2 blue-white star 75 light years away. It is an eclipsing binary of the Algol type, but it varies only 0.1 in magnitude, which is too slight to be seen visually.

R CrB is a remarkable star. It is hydrogen poor and carbon rich. Its variability was discovered by Pigott in 1795. Violent changes are happening in its corona and chromosphere, and these are reflected in its brightness, which can be between 6th magnitude and 14th magnitude. It is a prototype star for a class of variable stars.

α Canum Venaticorum is popularly called Cor Caroli, meaning Charles' heart. This is a reference to King Charles I of England. It is said to have shone brightly in 1660 on the arrival of Charles II in England at the Restoration of the Monarchy. It is a double star, the brighter having a magnitude of 2.9, with a magnitude 5.5 companion, visible in small telescopes. The brighter star is representative of the a CVn class of variable stars, with strong varying magnetic fields. These are probably evolving away from the main sequence of stars.

β CVn at magnitude 4.2 is the only other prominent star in the constellation. It is a yellow star 27 light years away and has a similar brightness to the Sun.


Visibility

The two constellations are a long way north of the equator and are low as seen from New Zealand. α CVn is above the horizon for only a little over 6 hours from Wellington, while α CrB is up for just over 8.5 hours.

Canes Venatici rises first and is due north and highest at about 10 pm mid May and 8 pm a month later. From mid New Zealand α CVn has a maximum altitude of about 10°. From Auckland it is rather higher at 15°, but from Invercargill it only rises 5° above the horizon. The constellation is so far north that, for most parts of New Zealand, the lower parts do not rise above the horizon.

Corona Borealis is due north about 150 minutes after Canes Venatici, that is about 10.30 pm mid June and 8.30 pm mid July. The constellation is smaller than Canes Venatici and not as far north. Consequently it rises a little higher in southern skies with α CrB being about 22° above the horizon as seen from Wellington.

LEPUS (pronounced LEP-uss) and COLUMBA (pronounced koh-LUM-bah)

Chart showing Lepus and Columba

Lepus, the Hare, is one of the ancient constellations, to which Ptolemy assigned twelve stars. It can be recognised by four prominent stars in a trapezium shape, located at the foot of Orion. Since we are in the Southern hemisphere, Orion appears upside-down; the foot of Orion is above Orion, and so is Lepus.

Columba, the Dove, appeared first as a constellation in Bayer's atlas of 1603,and has been accepted since 1679 when it was included on a list by the Frenchman Augustine Royer. It may represent the dove in Noah's Ark, or the dove that the Argonauts sent ahead to help them pass safely between the Symplegades, the Clashing rocks at the mouth of the Black Sea.

To find these constellations in the evening, look north to find Orion's "belt" stars, that outline the bottom of the "pot", and look above and to the west.

Chart showing Chart showing Lepus and Columba at about 11pm NZDT on February 1.

Chart for Lepus and Columba

Constellation Caelum Constellation Horologium Constellation Eridanus Constellation Puppis Constellation Canis Major Constellation Orion Constellation Monceros

Details of some of the objects shown in the chart.

α Leporus (Arneb, the hare) is a magnitude 2.6 yellow-white supergiant star 950 light years away.

β Lep (Nihal) is a magnitude 2.8 yellow giant star 320 light years away. It has a faint companion star.

γ Lep is an attractive duo able to be seen in binoculars, consisting of a yellow magnitude 3.8 star and an orange companion of magnitude 6.4, 27 light years away.

δ Lep is magnitude 3.8 yellow giant star 160 light years away.

R Lep is a variable star changing every 440 days or so between 6th and 10th magnitude. When near maximum, this star shines like a crimson jewel in a field well sprinkled with stars. It is known as Hind's Crimson Star after the English observer John Russell Hind who described it as 'like a drop of blood on a black field'. Small aperture telescopes show the colour well when it is bright.

M 79 (NGC 1904) is a small but rich globular cluster first discovered by Méchain in 1780. It is visible as a fuzzy 8th magnitude star in small telescopes. Larger telescopes will show the outlying stars faintly, and gleaming points of light right to the centre. Nearby in the same low-power fine field is the binary star Herschel 3752, consisting of a beautiful deep yellow pair.

α Columbae (Phact) is a magnitude 2.6 blue-white star 120 light years away.

β Col is a magnitude 3.1 yellow giant star 86 light years away.

NGC 1792 is bright elongated spiral galaxy in a fine interesting field, with fairly bright stars near the edges.

NGC 1808 is a long bright oval galaxy in a fine interesting field of scattered stars. Visually through a telescope it appears to have a small bright lengthened core, but in photographs it is a large barred spiral with peculiar dust lanes and an unusual starburst nucleus.

NGC 1851 is a beautiful globular cluster rising sharply to a bright centre. It is round but somewhat asymmetrical in larger telescopes.


Visibility

The two constellations are "above", that is to the south of, Orion and so are visible for much of the Summer months in New Zealand. Columba is very high in the sky early in the evening in January and February, with some part passing directly overhead for much of New Zealand.

RIANGULUM AUSTRALE, (pronounced tri-ANG-gyah-lum OSS-tray-lee),
NORMA, (pronounced NOR-mah) and
CIRCINUS (pronounced SUR-sih-nuss)

Chart showing the constellations.

Triangulum Australe, the southern triangle, was introduced in 1603 by the German celestial cartographer Johann Bayer, as a southern equivalent of the long-established northern triangle Triangulum. It was apparently suggested though by Pieter Theodor about a century earlier. It is an easily found constellation near the Southern Cross.

Norma, the Surveyor's Level, was invented by Nicolas Louis de Lacaille, in the 1750's. Originally it was Norma et Regula, the carpenter's level and square, and some stars in the constellation were part of Ara and Lupus, but since Lacaille's time the outline of Norma has been altered, so that the stars which formally were α and β Normae, have now been placed in neighbouring constellations. Norma lies in a rich area of the Milky Way.

Circinus, the Drawing Compasses, is another small and obscure constellation introduced by Lacaille, appropriately near Norma the Level. A nearby and interesting spiral galaxy (ESO 97-G13) was found in Circinus in 1977. It peers through a small hole in the absorption near the galactic plane.

To find these constellations look south to find the pointers to the Southern Cross. Circinus and Triangulum Australisare below and slightly to the left of the pointers, with Norma to the left of the Pointers and at the same level.

Chart showing Triangulum Australe, Norma, and Circinus in June.

The view is a little to the east of south at about 9 pm on June 1 or 7 pm on July 1.

Triangulum Australe, Norma, and Circinus

Constellation Lupus Constellation Centaurus Constellation Musca Constellation Chamaeleon Constellation Octans Constellation Apus Constellation Pavo Constellation Ara Constellation Scorpius

Some stars and interesting objects in the Constellations

Tiangulum Australe

α Trianguli Australis is a magnitude 1.9 orange giant star 55 light years away.

β TrA is a magnitude 2.9 white star 33 light years away.

γ TrA is a magnitude 2.9 blue-white star 91 light years away.

NGC 5979 is a planetary nebula in a crowded field of stars. Small telescopes will distinguish the pale greyish-blue disk from a star.

NGC 6025 is a fine open cluster of about 30 white and yellow stars, visible in binoculars, lying 2000 light years away.

Norma
γ2 Normae is a magnitude 4.0 yellow giant star 130 light years away. Next to it in the sky is the far more distant yellow supergiant γ1 Nor, at magnitude 5.0

δ Nor is a magnitude 4.7 white star 230 light years away

ε Nor appears as a double star in small telescopes, having components of magnitude 4.8 and 7.5, 490 light years away. Each of the components is a spectroscopic binary star, making this, in reality, a four star system.

ι1 Nor appears in small telescopes as a double star with magnitudes 4.9 and 8.5, lying 490 light years away, in a field sprinkled with stars.

NGC 5946 is a small, moderately bright globular cluster, lying in a beautiful star field. There a re a number of fairly bright wide pairs of stars in the cluster, especially south.

NGC 6087 is a very scattered open cluster of about 35 stars, 3600 light years away, visible in binoculars. There is a golden-yellow central star

Circinus
α Circini is a magnitude 3.2 white star 46 light years away. There is a wide companion magnitude 8.8 star visible in small telescopes.

γ Cir consists of a very close pair of blue and yellow 5th magnitude stars, able to be separated in telescopes of 150 mm or more aperture, under high magnification. The long period binary system has a likely period of several centuries.

NGC 5315 is a bright small planetary nebula, fairly well defined in a beautiful field of stars.


Visibility

Triangulum Australe and Circinus are circumpolar, that is never set, for places in New Zealand. Norma is a little nearer the equator and parts of the constellation dip below the horizon when it is to the south as seen from many parts of New Zealand.

The triangle is at its highest, to the left of, and slightly higher than, the Pointers at about midnight in early June or at 10 pm early July. Circinus is at its highest point about an hour earlier. At these times Norma will be above the other two constellations. Constellations reach their highest point in the sky four minutes earlier each day, so each succeeding month the constellations are highest 2 hours earlier.

PICTOR and CHAMAELEON (pronounced PICK-ter and kah-MEE-lee-un)

Chart showing the constellations.

These are relatively modern constellations with Chamaeleon originating in 1603, by Johann Bayer, and Pictor by Nicolas Louis de Laicalle in the 1750's. Neither is easily identified, or obvious. Pictor was originally Equuleus Pictoris, but the name was shortened by Gould in 1877. It represents the Painter's Easel. Chamaeleon represents the reptile of that name.

One of the nearest regions of star formation to the Sun lies in Chamaeleon, and both dark and bright reflection nebulosity are associated with it.

To find these constellations, look south late mid evening a little below the zenith. Use Achernar, Canopus and the Magellanic Clouds to help locate the constellations from the map. Most of the brighter stars are around magnitude 4, so a dark sky is needed.

Chart showing the constellations as seen looking south about 10.30 pm mid February.


Chamaeleon and Pictor.

Constellation Vela Constellation Puppis Constellation Carina Constellation Volans Constellation Dorado Constellation Horologium Constellation Eridanus Constellation Reticulum Constellation Mensa Constellation Hydrus Constellation Tucana Constellation Octans Constellation Apus Constellation Musca Constellation Crux Constellation Centaurus

Details of some of the objects shown in the chart.

α Pictoris is a white star of magnitude 3.3, 52 light years away.

β Pic is a magnitude 3.9 white star, 78 light years away.

γ Pic is a magnitude 4.5 orange giant star, 260 light years away.

 
α Chamaeleontis is a white star of magnitude 4.1, 78 light years

β Cha is a magnitude 4.3 blue star, 360 light years away.

γ Cha is a magnitude 4.1 red-giant star, 250 light years away.

δ Cha consists of a wide pair of unrelated stars, clearly seen in binoculars. δ1 Cha is a magnitude 5.5 orange star 360 light years away, while δ2 Cha is a magnitude 4.5 blue star 550 light years away.

Visibility

Pictor is entirely circumpolar from the South Island of New Zealand and so visible all night. From the North Island the more northerly parts of the constellation will set for a few hours. The constellation is highest about 10pm (NZDT) during February.

Chamaeleon is considerably nearer the south pole in the sky, bewteen declinations 85° south and 93° south. So it is reasonably well placed for viewing all the year. The constellation spreads through 90° round the pole; as a result the constellation is at its highest in the sky at 9pm NZST between mid March and mid June. In February when Pictor is at its highest, Chamaeleon is lower and somewhat to the left.

CETUS "The Sea Monster" (Pronounced SEE-tes).

Chart showing the constellation.

This is an ancient constellation depicting a sea monster that threatened to devour Andromeda, before Perseus rescued her.  Cetus is found in the sky basking on the shores of the constellation Eridanus, the River, and near Aquarius the Water Carrier.  The constellation is large but faint and lies in a rather barren part of the sky.

Cetus contains some interesting stars, particularly ο Ceti and τ Ceti.  UV Ceti, is a faint but famous prototype of a class of erratic variable variables known as flare stars.  These are red dwarfs that undergo sudden increases in light output lasting a few minutes.  The outbursts of the flare star component of UV Ceti take it from its normal 13th magnitude to as bright as 7th magnitude.

To find Cetus, look north between the Great Square of Pegasus and Aldebaran, about half way up from the horizon.

Chart showing Cetus - as seen about 10.30 pm (NZDT) mid November.

The horizon is for the south of the South Island of New Zealand

Cetus chart

Constellation Aquarius Constellation Sculptor Constellation Fornax Constellation Lepus Constellation Auriga Constellation Perseus Constellation Triangulum Constellation Aries Constellation Eridanus Constellation Orion Constellation Taurus Constellation Pisces Constellation Pegasus Constellation Andromeda

Some stars and interesting objects in the Constellation

α Ceti (Menkar, meaning nose) is a magnitude 2.5 red giant star 220 light years away. Binoculars show an unrelated magnitude 5.6 blue companion, lying over six times further away.

β Cet (Deneb kaitos, tail of the whale) is a magnitude 2.0 yellow giant star, the brightest in the constellation. It lies is a magnitude 96 light years away.

γ Cet (Kaffaljidhmah), is a beautiful close double star of magnitudes 3.7 and 6.4, with colours of white and yellow. The system lies 82 light years away.

ο Cet (Mira, the wonderful).  Mira is a long known red variable star recognised by the Dutch astronomer David Fabricius in 1596.  It varies in brightness between about 3rd and 9th magnitude with a period between 320 and 370 days, with a mean of 331 days as it swells and contracts.  At maximum the diameter is slightly more than 200 times that of the Sun, or roughly the diameter of Earth's orbit.  At maximum it is an unaided eye object, and at minimum at least good binoculars are needed to see the star.

τ Cet is one of the closer stars to the Sun, that is similar to the Sun. It is a yellow dwarf lying 11.9 light years away appearing at magnitude 3.5.

M 77 (NGC 1068) is a small softly glowing 9th magnitude face-on spiral galaxy appearing near δ Ceti. Merchain discovered this galaxy in 1780. It is classified as a Seyfert galaxy, a type of spiral galaxy with a bright nucleus. Seyfert galaxies show rapidly expanding gas in the central region. M77 lies about 50 million light years away.

Visibility

Cetus straddles the celestial equator with its tail extending into the southern hemisphere. It is highest in New Zealand skies at about 11:00 pm (NZDT) in mid November, an hour later at the beginning of the month and an hour earlier by the month's end.

It remains visible in the evening sky until about the end of February, by which date the constellation will be low and to the west as evening twilight darkens. Shortly before it sets, Cetus is in the west sprawled along the horizon across over 45° of sky.

DRACO the Dragon, Pronounced DRAY-koh,
CEPHEUS the King of Ethiopia, Pronounced SEE-fee-us,
URSA MINOR the Lesser Bear, pronounced UR-sah MY-ner

Chart showing the constellations.

Of these 3 northern constellation, only a small portion of Draco rises from the latitude of northern New Zealand. No part of any of these constellations rise further south in the country.

Draco, the Dragon lies coiled around the north celestial pole. It is an ancient constellation, to which the Greek astronomer Ptolemy, in 150 AD, assigned thirty one, mainly faint stars. Number 5 on his list now named γ Draconis is historically important because it passes close to overhead at Greenwich, and observations of this star led James Bradley in the 1720's to discover the aberration of light. This is the apparent change in position of an object resulting from Earth's orbital motion around the Sun.

γ Draconis, magnitude 2.2, just rises as seen from Auckland and places to the north.

Cepheus is an ancient constellation representing the legendary King of Ethiopia, husband of Cassiopeia and father of Andromeda, also nearby constellations. Ptolemy assigned eleven stars to this constellation. The most famous star is δ Cephei, the prototype of the Cepheid variable stars. These are used as standard candles in finding distances in the universe. This star's fluctuations in light output were discovered in 1784 by the English astronomer John Goodricke, a deaf-mute who died in 1786 at the age of 21

Ursa Minor is an ancient constellation, possibly introduced around 600 BC, by the Greek astronomer Thales. It is also commonly known as the "Little Dipper". Polaris, the Pole Star at present, is conveniently close to the north celestial pole, greatly aiding northern hemisphere astronomers in aligning amateur telescopes. A wobble in Earth's spin called precession will bring Polaris closest to the pole in 2100 AD. In ancient times, when the constellation was named, Polaris was well away from the pole. Later, in Hipparchus's time, 150 BC, Polaris was 12o from the pole.

Chart showing Draco to the north, at about 10 pm in late July. The horizon is for Auckland.

Draco, Cepheus and Ursa Minor.

Constellation Bootes Constellation Cygnus Constellation Delphinus Corona Borealis Constellation Hercules Constellation Serpens Constellation Lyra Constellation Vulpecula Constellation Sagitta

Two stars in Draco which rise at Auckland

β Draconis, Rastaban is a magnitude 2.8 star some 362 light years away. It is about 800 times brighter than the Sun.

γ Dra, Eltanim is a magnitude 2.2, reddish, star. It is about 150 light years away and about 200 times brighter than the Sun. The star only just rises in New Zealand but passes overhead in London. It was through observation of the star (observing with a telescope pointing up his chimney) that James Bradley discovered the aberration of light in 1729. This was the first observational evidence that the Earth moves round the Sun. The Earth's movement causes light from a star to appear to come from slightly different directions as it moves round the Sun.

Visibility

The most southerly parts of Draco are visible from the North Island of New Zealand, with γ Dra just rising at Auckland. The star transits, that is highest and due north at about 10 pm towards the end of July. The time of transit gets an hour earlier every 15 days.

Only the most southerly tip of Cepheus, containing no bright star, rises for places in the extreme north of New Zealand. It is at its highest, no more than 2° above the horizon from North Cape, at 10 pm in late September.

Ursa Minor, the north pole constellation, remains well below the horizon at all times from the latitude of New Zealand.

CENTAURUS   (Pronounced sen-TAUR-us)

Chart showing the constellation.

Centaurus is a large and rich constellation representing a centaur in Greek mythology, reputedly the scholarly centaur Chiron, who was the tutor of many Greek heroes, and who, according to legend invented the main constellations. He was raised to the sky after being accidentally struck by a poisoned arrow from Hercules.

The constellation is of particular interest because it contains the closest stars to the Sun, α Centauri, a group of three stars linked by gravity. The line of the two stars α and β Centauri (known as "the Pointers") points to Crux, the Southern Cross.

One of the strongest radio sources in the sky, Centaurus A, lies in the constellation, associated with the galaxy NGC 5128.

Centaurus lies in a prominent part of the Milky Way, providing rich star fields and clusters for binoculars.

To find Centaurus look towards the south and up about 70° at this time of the year. You should be able to orient yourself by using the Pointers and Crux the Southern Cross, to help find the constellation.

Chart showing Centaurus as seen high in the sky to the south fairly early evening in June.

Centaurus and surrounding constellations

Constellation Lupus Constellation Triangulum Constellation Circinus Constellation Musca Constellation Carina Constellation Crux

Some stars and interesting objects in Centaurus


α Centauri (Rigel Kentaurus) is the brightest star in Centaurus and 3rd brightest in the sky. It lies very close at 4.3 light years away. To the unaided eye it shines as a star of magnitude -0.27, but small telescopes reveal that it consists of two individual yellow stars of magnitude 0 and 1.4. The brightest of these is very similar in nature to the Sun. These stars orbit each other every 80 years. Associated with these stars is an 11th magnitude red dwarf star called Proxima Centauri. This dim star is slightly closer to the Earth, but lies 2° away from α and is not even in the same telescopic field of view. This star probably takes about a million years to orbit its two brilliant companions.

β Cen (Hadar or Agena) is a magnitude 0.6 blue giant star 460 light years away.

3 Cen, also known as K Cen is a striking pair of blue-white stars of magnitudes 4.7 and 6.2 in a field of scattered stars.

ω Cen (NGC 5139) is the largest and brightest globular cluster visible to the unaided eye from a dark site when the Moon is absent and indeed was originally recorded by Ptolemy as a star. It appears to cover an area over two-thirds that of the full Moon. Small telescopes and binoculars begin to resolve its outer regions into stars. It is a showpiece for all size telescopes provided that the field of view is large enough to include some of the surrounding area.

Edmund Halley of comet fame discovered this globular cluster in 1677. It was often mistaken by the public in 1986 for Halley's Comet when the comet was in the vicinity. It is about 16,000 light years away, which makes it among the nearest globular clusters.

NGC 3766 which is a fine scattered open cluster of about 60 stars 1700 light years away visible to the unaided eye. This cluster is effective even in small aperture telescopes, with a pattern of star loops giving it a lobed appearance and containing orange, yellow, white and bluish stars. It merges into a rich star field.

The Coal sack, in Crux, Centaurus, and Musca, is a dark nebula contrasting well with the bright Milky Way. The Australian aborigines regarded the Coal Sack as the head of the "Emu" with the neck and part of the body being a dark rift in the Milky Way.

NGC 4945 is an edgewise late-type spiral galaxy appearing as a long narrow luminous haze in a beautiful starry field. This galaxy is a member of a small group of galaxies that includes NGC 5128 and M 83 in Hydra.

NGC 5460. This large scattered open cluster is well suited for small telescopes. There is a semi-circle of bright stars north of centre, that includes an orange star and a nice pair of stars. It lies about 2700 light years away. Appearing slightly north-east of the semi-circle is a small conspicuous lenticular galaxy, ESO 221-G26.

NGC 5128 is a remarkable galaxy appearing as a bright round luminous haze bisected by a dark bar seen relatively easily in binoculars from a dark sky site. This galaxy is the famous radio source Centaurus A.

NGC 3918 a small planetary nebula. This was discovered by John Herschel in 1834 who called it the Blue Planetary. Through a telescope, it appears similar to the planet Uranus. It lies in a fine starry field.

Visibility

The more southerly parts of the constellation, including the Pointers, is circumpolar for New Zealand, that is it never sets. The Pointers are low to the South in the evening in Summer.

Central parts of the constellation are highest about 10.30 pm NZST in mid May and 8.30 pm, NZST, in mid June, when northerly parts of the constellation pass overhead in New Zealand. α Cen is highest about an hour later. By the end of June it will be at its highest point at 8.30 pm.

CARINA the Keel   (Pronounced kah-RYE-nah)

Chart showing Carina

Carina the keel was part of the extensive Argo Navis, the ship of the Argonauts, until subdivided in the 1750's by the French celestial cartographer Nicolas Louis de Lacaille. As a part of Argo Navis, Carina's origin goes back to Greek times, and is associated with the legend of Jason and the Argonauts who sought the Golden Fleece. Carina lies in the Milky Way, providing rich star fields and clusters for binoculars.

To find Carina look towards the south and up about 70° at this time of the year. You should be able to orient yourself by using Crux, the Southern Cross, and Canopus to help find the area around Carina.

Chart showing Carina high to the south about 11 pm NZDT mid March or 8 pm NZST mid April.

Carina. 5.6 kb

Constellation Centaurus Constellation Vela Constellation Crux Constellation Puppis Constellation Pictor Constellation Dorado Constellation Mensa Constellation Volans Constellation Chamaeleon Constellation Octans Constellation Apus Constellation Musca Constellation Triangulum Australe Constellation Circinus

Details of some of the objects shown in the chart.

α Carinae, Canopus at magnitude -0.72 is the second brightest appearing star in the sky. It is a yellow-white supergiant 1200 light years away. It is named after the pilot of the fleet of King Menelaos, and appropriately enough this star is now often used as a guide for navigating spacecraft.

β Car, Miaplacidus is a magnitude 1.7 star. It is 200 times more luminous than the Sun at a distance of 110 light years.

ε Car, Avior has a magnitude 2.2. It is a red star 5600 times more luminous than the Sun, 630 light years away.

ι Car, Turais also has a 2.2 magnitude but is not red. It is 4900 times as luminous as the Sun and 690 light years away.

θ Car is a magnitude 2.8 blue-white star 750 light years away at the centre of the open cluster IC 2602. This open cluster known as the southern Pleiades, is a fine bright cluster of about 30 stars easily shown in binoculars and small telescopes. The cluster is easily visible to the unaided eye from a dark sky site.

NGC 2516 is a bright beautiful open cluster visible to the unaided eye from a dark site when the Moon is absent. It is a glorious sight in binoculars or a small telescope, when its scattered groups and irregular sprays of stars can be seen. Three bright orange stars contrast well with the rest of the cluster members.

NGC 3372 is a great diffuse nebula visible to the naked eye as a brilliant patch of the Milky Way surrounding the giant star η (eta) Carinae. It is one of the showpieces of the southern sky. Small telescopes and binoculars will show its dark lanes, the most famous being the "keyhole" because of its distinctive shape. The erratic variable star η Car is surrounded by a shell of gas thrown off in the star's 1843 and later outbursts. With high magnification the fuzzy area surrounding the star appeared like a little man - hence the name "Homunculus" nebula. At present the star is brightening quite rapidly, but it still has some way to go to reach its magnitude of -1 that it attained in 1843.

NGC 3532 is a bright cluster of 150 stars covering 1o of the sky ( twice the diameter of the Moon). It is visible to the unaided eye and a glorious sight in binoculars. Small telescopes show small straight and curved lines and a number of bright orange stars.

NGC 3114 is another very beautiful open cluster suitable for binoculars and small aperture telescopes. The stars appear very numerous in elegant pairs, triplets and small groups, but there is little concentration towards the centre.

R Carinae is a red giant variable star of uncertain distance, varying between 4th and 10th magnitude every 150 days.

υ Car is a double star with white components of magnitudes 3.1 and 6.0 divisible in small telescopes.

Visibility

Carina is a circumpolar constellation as seen from the latitude of New Zealand. Thus it is visible throughout the year. The constellation is spread over a large arc of the sky so that Canopus in the east is due south and highest about 5 hours before the western end.

ε Car, near the centre of Carina, is highest in the sky, and due south, at about 10.30 pm NZDT in mid March and 7.30 pm NZST in mid April.