Constellations: Puppis 'the Stern' Content from the guide to life, the universe and everything

Constellations: Puppis 'the Stern'

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The shield of the Science, Mathematics and Engineering faculty of the h2g2 University.Constellations: Overview | Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum
Camelopardalis | Cancer | Canes Venatici | Canis Major | Canis Minor | Capricornus | Carina | Cassiopeia | Centaurus
Cepheus | Cetus | Chamæleon | Circinus | Columba | Coma Berenices | Corona Australis | Corona Borealis | Corvus
Crater | Crux | Cygnus | Delphinus | Dorado | Draco | Equuleus | Eridanus | Fornax | Gemini | Grus | Hercules | Horologium
Hydra | Hydrus | Indus | Lacerta | Leo | Leo Minor | Lepus | Libra | Lupus | Lynx | Lyra | Mensa | Microscopium | Monoceros
Musca | Norma | Octans | Ophiuchus | Orion | Pavo | Pegasus | Perseus | Phoenix | Pictor | Pisces | Piscis Austrinus
Puppis | Pyxis | Reticulum | Sagitta | Sagittarius | Scorpius | Sculptor | Scutum | Serpens | Sextans | Taurus
Telescopium | Triangulum | Triangulum Australe | Tucana | Ursa Major | Ursa Minor | Vela | Virgo | Volans | Vulpecula
Name:Puppis (Latin: 'the Stern')
Short form:Pup
Area:673 sq deg
Co-ordinates1:Right Ascension 08h, Declination −35°

Puppis, the Stern is a wholly southern constellation lying between Canis Major and Columba to its west, Hydra, Pyxis and Vela to the east, Carina to the south and Monoceros to its north. Its most prominent stars are of second magnitude and it is seen at its highest in the Southern Hemisphere's summer months. From the northern latitudes of the British Isles, only the northernmost part of the constellation rises above the horizon and is best seen during the winter months. It is relatively easily located from the close proximity of Sirius2, the brightest star in the night sky, which lies just a few degrees north-west of its boundary.

Mythology and History

Puppis3 is part of the one-time giant constellation Argo Navis. It represented the ship the Argo, which was built for the celebrated Jason and his 50 Argonauts of Greek mythology. The tale tells the adventures of the Argonauts and how they undertook a quest to retrieve the golden fleece of Aries the Ram from Colchis. Other stories link Argo Navis with the boat that carried Isis and Osiris in Egyptian myth, while Christian bibliology links it with Noah, his Ark, and the great deluge.

The complete Argo Navis was one of the 48 constellations listed in Ptolemy's star catalogue the Almagest. It was so large that to make it more manageable, the conventional reference to individual stars was being in 'the sail', 'the keel' or 'the stern'. Argo Navis is the only one of Ptolemy's constellations not to be accepted as a constellation in its own right. When the IAU4 delineated the boundaries covering the whole celestial globe they created four new constellations out of the old. These are now recognised as Carina the Keel5, Vela the Sail, Pyxis the Mariner's Compass, and Puppis.

Stars of Puppis

The four-way split created the anomalous situation with most of the other constellations whereby the brightest star in the constellation is given the Greek letter alpha, the next brightest beta, followed by gamma and so on through the complete Greek alphabet6. The split did not take into account the positions of the graded stars, so we now have, for example, alpha and beta in Carina, gamma and delta in Vela and the others spread around those two and Puppis.

Zeta Puppis is the brightest star in Puppis at +2.20 magnitude. Rho Puppis is a variable star which dims slightly every 3.35 hours. Xi Puppis is a G-class supergiant star which has an actual luminosity some 6,000 times that of our own Sun. Being 650 light years7 distant it only shows at a magnitude of +3.35.

Star Table

StarDesignationName or Catalogue NoBrightness (m)Distance (light years)Remarks
ζ Pupzeta PuppisSuhail Hadar (Naos)+2.201,399O
π Puppi PuppisAhadi+2.701,094K3
ρ Puprho PuppisTurais+2.8063Variable
τ Puptau PuppisEl Rehla+2.94183K
ν Pupnu PuppisKaimana+3.17423B
σ Pupsigma PuppisHadir+3.25184K
ξ Pupxi PuppisAsmidiske+3.35650Yellow supergiant

Star Clusters and Nebulae

The Milky Way passes diagonally through the centre of Puppis, with the result that there are many fine star clusters to be seen, three of which are listed in the Messier catalogue. M46 and M47 are close together at the northern end of the constellation and with binoculars can be seen together in the same field of view. All three clusters are naked eye objects appearing as fuzzy patches, but can be resolved into individual stars with binoculars or small telescopes.

M46 is a rich open cluster of about 150 stars and just to its north is planetary nebula NGC 2438, the remains of a nova which in a larger telescope appears to be overlaying M46. In fact NGC 2438 is much closer to the Earth and is not associated with M46. It is simply a line-of-sight effect which gives an unusual 3D effect when seen together. M47 is a loose open cluster of about 75 stars of which four in a rhomboid shape are the most prominent. M93 is one of the southernmost of Messier's objects and lies about nine degrees directly south of M46 and M47. It appears as a loose irregular cluster of about 30 stars.

The Gum Nebula is mainly centred within neighbouring Vela, but the nebula spills over into Puppis. It is an ancient supernova remnant discovered by astronomer Colin S Gum and named after him. Even by supernova standards this must have been something quite spectacular. Estimated to have occurred about a million years ago, anyone watching in prehistoric times would have been treated to a flaring orb larger and brighter than the Moon. Residue of this supernova has expanded over time to cover a massive angular size of more than 40 degrees8, making it the largest nebula of its type that can be seen from Earth.

NGC 2440 is a planetary nebula which is the ejected material of a sun-like star expanding outwards, and is now over a light-year in diameter. The material glows in ultraviolet light from the central star which, with a surface temperature of 200,000 Kelvin, is one of the hottest known.

On 8 November, 1942, Nova Puppis erupted approximately five degrees due north of zeta Puppis, and within 24 hours brightened to a magnitude of -0.3. Although it was the third brightest nova of the 20th Century, it faded into obscurity almost as quickly. Described as a 'fast nova', within a month it had dimmed by some 18 magnitudes.

Star Clusters and Nebulae

CatalogueTypeBrightness (m)Distance (light years)Remarks
M46Open cluster+6.15,000Cluster approx 150 stars
M47Open cluster+4.41,700Cluster approx 75 stars
M93Open cluster+6.03,400Cluster approx 30 stars
NGC 2438Planetary Nebula+11.03,300Nova remnant
NGC 2440Planetary Nebula+11.04,000Central White Dwarf
Calabash NebulaProtoplanetary Nebula+9.54,200Central White Dwarf

Meteor Showers

Three meteor streams have their radiant in Puppis:

  • The Alpha Puppids occur only occasionally between 2 and 6 December. They produce meteors at a rate of up to six per hour but their radiant is spread across a large area and encroaches into the neighbouring constellation of Vela. For that reason this shower is sometimes known as the Puppid-Velids.
  • The Pi Puppids are another variable shower which do not occur each year, but when they do, their radiant is near pi Puppis, and the maximum rate of four per hour occurs between 18 and 25 April.
  • The Zeta Puppids are a weak shower whose maximum of three per hour occur in mid-November.

Extrasolar Planets

Several stars within Puppis have been found to have single or multiple planets in orbit around them:

  • HD 50499 has one candidate planet 1.7 times the mass of our own Jupiter. It orbits its sun in a period of just over seven years. Unusually its orbital period is measured in years rather than days.
  • HD 70642 b is another gas giant at almost twice Jupiter's mass but revolving around its star in 2,231 days.
  • NGC 2423-3 b is over ten times Jupiter's mass and completes an orbit every 714 days.
  • HD 69830, an orange dwarf, has no fewer than three candidate extrasolar planets. All three measure between 0.033 and 0.058 of Jupiter's mass making them closer to Earth's size than the predominant gas giants usually found. Planets HD 69830 b and HD 69830 c are close in to their parent star, but HD 69830 d revolves further out in a much more reasonable 197 days.
  • HD 48265 b is a superjovian planet orbiting a yellow dwarf star similar to our own Sun. It orbits just outside the system's habitable zone.
  • The star HD 60532 has two superjovian worlds in attendance.
  • WASP-23 b is a gas giant whose orbit is completed in less than three Earth days.
  • WASP-121 b is a hot Jupiter in an extremely tight orbit around its parent star.
  • WASP-122 b is a superjovian world in an extremely tight orbit around a sun-like star.

None of the planets featured are possibilities for the search for extra-terrestrial life because they are either the wrong type (gas) or their temperature range is too extreme for life as we know it to exist.

1Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.2Alpha Canis Majoris.3Also known as the 'Poop-deck'.4The International Astronomical Union.5Otherwise known as 'the Hull'.6This method of identifying stars within a constellation was originated by astronomer Johann Bayer.7A light year is the distance light travels in one year, roughly 5.88 trillion miles or 9.46 trillion km.8The full moon has an angular measurement of half a degree so this will give an indication of the massive displacement of this nebula.

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