Columba constellation is located in the southern sky. Its name means ‘dove’ in Latin. Columba is the 54th constellation in size, occupying an area of 270 square degrees. It lies in the first quadrant of the southern hemisphere (SQ1) and can be seen at latitudes between +45° and -90°. The neighboring constellations are Caelum, Canis Major, Lepus, Pictor, and Puppis.
[http://www.constellation-guide.com/constellation-list/columba-constellation/]
Columba with an olive branch in its beak as shown on Chart XVIII of the Uranographia of Johann Bode (1801).
Columba is a constellation formed in the late 16th century by the Dutch cartographer and astronomer Petrus Plancius, who took some stars that Ptolemy in his Almagest had catalogued as lying outside Canis Major. These unformed stars can be seen, for example, on the southern half of Albrecht Dürer’s star chart as two little groups, one to the south of Lepus and the other between the hind legs of Canis Major. Columba was first shown as a separate constellation in 1592 on a celestial hemisphere that Plancius tucked into the corner of his first great terrestrial map, although it was unnamed. It flies behind Argo Navis, the ship, and under the hind legs of Canis Major.
Columba is supposed to represent Noah’s dove, sent out from the Ark to find dry land, and which returned with an olive branch in its beak, a sign that the Flood was at last subsiding. To complete this Biblical tableau, Plancius even renamed Argo as Noah’s Ark on a globe of 1613. However, those familiar with the story of Argo might instead think of Columba as the dove sent by the Argonauts between the sliding doors of the Clashing Rocks to ensure their safe passage.
[http://www.ianridpath.com/startales/columba.htm]
[http://astropixels.com/constellations/charts/Col.html]
Constellations of Columba and Lepus
[http://www.davidmalin.com/fujii/source/Col.html]
Alpha Columbae is also named Phact, which derives from the Arabic ‘fākh(i)tah,’ meaning ‘ring dove.’ It is a third magnitude star with an apparent visual magnitude of 2.6, making it the brightest member of Columba. It is located at a distance of around 261 light-years.
This is believed to be a solitary star, although it has a faint optical companion at an angular separation of 13.5 arcseconds, making it a double star. The stellar classification of Alpha Columbae is B7 IV, with the luminosity class of IV indicating it has evolved into a subgiant star. The spectrum shows it to be a Be star surrounded by a hot gaseous disk, which is generating emission lines because of hydrogen recombination. Like most if not all such stars, it is rotating rapidly with a projected rotational velocity of 176 km s−1. It is a suspected Gamma Cassiopeiae type (GCAS) variable star, with its apparent magnitude varying from 2.62m to 2.66m.
[https://en.wikipedia.org/wiki/Alpha_Columbae]
Beta Columbae is also named Wazn, which means ‘weight’ in Arabic. It is the second brightest star in Columba. It has an apparent visual magnitude of 3.1, which is bright enough to be viewed with the naked eye even from an urban location. It is located at a distance of about 87.2 light-years from the Sun.
The spectrum of Beta Columbae matches a stellar classification of K1 IIICN+1, where the ‘III’ luminosity class indicates this is a giant star that has exhausted the supply of hydrogen at its core and evolved away from the main sequence of stars like the Sun. The notation ‘CN+1’ indicates a higher than normal level of cyanogen (CN) absorption in the atmosphere of the star. The interferometry-measured angular diameter of this star is 3.99 ± 0.05 mas, which, at its estimated distance, equates to a physical radius of about 11.5 times the radius of the Sun. Despite having expanded to this radius, Beta Columbae only has about a 10% greater mass than the Sun. The outer envelope of this star is radiating energy at an effective temperature of 4,545 K, resulting in an orange hue that is typical of a cool, K-type star.
Beta Columbae has a high proper motion across the celestial sphere and is moving at an unusually large speed of 100 km s−1 relative to the Sun. About 107,200 years ago it made a close approach to the Beta Pictoris system. The estimated separation of the two stars at this time was around 1.9 ly, and Beta Columbae may have perturbed outlying planetesimals within the debris disk surrounding Beta Pictoris.
[https://en.wikipedia.org/wiki/Beta_Columbae]
The big blue star once was the partner of AE Aurigae. The stars came into existence together in the Orion Nebula and since then drift away with high speed. Reason for this could have been a supernova explosion a long time ago.
[https://jumk.de/astronomie/big-stars/mu-columbae.shtml]
Mu Columbae is one of the few O-class stars that are visible to the unaided eye. The star is known to lie approximately 1,300 light years from the Solar System.
This is a relatively fast rotating star that completes a full revolution approximately every 1.5 days. (Compare this to the Sun, which at only 22 percent of this star’s diameter rotates only once every 25.4 days.) This rate of rotation is fairly typical for stars of this class.
Based on measurements of proper motion and radial velocity, astronomers know that this star and AE Aurigae are moving away from each other at a relative velocity of over 200 km/s. Their common point of origin intersects with Iota Orionis in the Trapezium cluster, some two and half million years in the past. The most likely scenario that could have created these runaway stars is a collision between two binary star systems, with the stars being ejected along different trajectories radial to the point of intersection.
[https://en.wikipedia.org/wiki/Mu_Columbae]
An ultraviolet image of NGC 1851
[https://en.wikipedia.org/wiki/NGC_1851]
There is one globular cluster in Columba, 7th-magnitude NGC 1851. It is 35,000 light-years from Earth and is resolvable in medium-sized amateur telescopes.
NGC 1792 is a spiral galaxy of magnitude 10.2 located in the Columba constellation. It was discovered by James Dunlop on October 4, 1826:
[https://en.wikipedia.org/wiki/NGC_1792]
NGC 1792, a starburst galaxy in Columba
NGC 1792 is a barred spiral galaxy, located about 43 million light-years away from Earth in the south-western corner of the small southern constellation of Columba (the Dove), while it is moving away from us at 1211-1222 kilometers per second. It is a member of the NGC 1808 Group of Galaxies.
This bright, large oval-shaped galaxy has a large core with a very bright nucleus. It appears brighter along the western side of the major axis, with some areas of lower surface brightness what gives us a hint of its spiral structure. The mass of NGC 1792 is very close to 18 billion solar masses.
The optical appearance of this starburst galaxy is quite chaotic, due to the patchy distribution of dust throughout the disk of NGC 1792. It is very rich in neutral hydrogen gas- fuel for the formation of new stars- and is indeed rapidly forming such stars.
The galaxy is characterized by unusually luminous far-infrared radiation, due to dust heated by young stars.
[http://annesastronomynews.com/photo-gallery-ii/galaxies-clusters/ngc-1792/]
NGC 1808 is a Seyfert galaxy of magnitude 10.8 located in Columba:
NGC 1808, a barred spiral galaxy in Columba
NGC 1808 is a barred spiral galaxy of some 35,000 light-years across, located about 40 million light-years away in the southern constellation Columba. NGC 1808 is undergoing so much star formation it has been deemed a starburst galaxy. The galaxy is moving away from us at 995 kilometers per second.
NGC 1808 is distinguished by a peculiar and complex nucleus, an unusually warped disk, and strange flows of hydrogen gas out from the central regions. The galaxy’s center is the hotbed of vigorous star formation.
The starburst must be at least 50 million years old, and can be no older than 100 million years old. Star formation has been rapid and continuous. Without an influx of fresh molecular gas into the central region, the star forming activity can only be maintained at this rate for another 6 to 20 million years.
NGC 1808 is called a barred spiral galaxy because of the straight lines of star formation on both sides of the bright nucleus. This star formation may have been triggered by the rotation of the bar, or by matter which is streaming along the bar towards the nuclear region (feeding the starburst). Filaments of dust are being ejected from the core into the galactic halo by massive stars that have exploded as supernovae in the starburst region.
The outer spiral arms of the galaxy are warped with respect to the inner arms (which display a prominent dark dust lane). This is evidence that NGC 1808 may have had a tidal interaction with the nearby galaxy NGC 1792. Such an interaction could have created the bar morphology, and hurled gas towards the nucleus of NGC 1808, igniting the exceptional burst of star formation seen there.
Stars are often born in compact clusters within starbursts, while dense gas and dust heavily often obscures these starburst region. In NGC 1808 are star formation regions in the bar and also many young star clusters in the nucleus of NGC 1808. The nucleus of the galaxy show two maxima. Either the galaxy has two nuclei (from a previous merger), or one of the dusty filaments happens to bisect the nucleus along our line of sight.
NGC 1808 is also a prominent radio source. The radio emission is produced by supernova remnants, of which supernova 1993af has been observed.
[http://annesastronomynews.com/photo-gallery-ii/galaxies-clusters/ngc-1808/]
Chandra Catches ‘Piranha’ Black Holes
These two galaxy clusters, known as CL 0542-4100 (in constellation Columba) and CL 0848.6+4453 (in constellation Lynx), are part of a sample used to count the fraction of galaxies with rapidly growing black holes, also known as active galactic nuclei (AGN). In the Chandra images of these two galaxy clusters, red corresponds to low-energy X-rays, the green to intermediate-energy, and the blue to high-energy X-rays. In each of these two fields, five AGN are found, although one of these may not be a member of the cluster. Many of the AGN are blue sources, as expected, since AGN are known to produce very high-energy X-rays. The diffuse emission is hot gas in the cluster and other point-like sources in the image are nearly all unrelated to the galaxy cluster.
The data show, for the first time, that younger, more distant galaxy clusters contained far more AGN than older, nearby ones. The four galaxy clusters in the distant sample, including the two shown here, are seen when the Universe is only about 58% of its current age. The nearby sample of galaxy clusters, obtained in an earlier study, is seen at about 82% of the Universe’s current age. It was found that the more distant clusters contained about 20 times more AGN than the less distant sample. AGN outside clusters are also more common when the Universe is younger, but only by factors of two or three over the same age span.
The reason for this difference is that earlier in the history of the Universe, these galaxies contained a lot more gas for star formation and black hole growth than galaxies in clusters do today. There was so much fuel in young clusters that the piranha-like black holes were able to thrive by growing much earlier than their counterparts in nearby clusters.
Distance Estimate: 5.7 billion light years.
[http://chandra.harvard.edu/photo/2007/agns/]
This Comet Lovejoy
Comet Lovejoy, C/2014 Q2, is framed like a cosmic Christmas tree with starry decorations in this colorful telescopic portrait, snapped on December 16th (2014). Its lovely coma is tinted green by diatomic C2 gas fluorescing in sunlight. Discovered in August of this year, this Comet Lovejoy is currently sweeping north through the constellation Columba, heading for Lepus south of Orion and bright enough to offer good binocular views. Not its first time through the inner Solar System, this Comet Lovejoy will pass closest to planet Earth on January 7, while its perihelion (closest point to the Sun) will be on January 30. Of course, planet Earth’s own 2015 perihelion passage is scheduled for January 4. A long period comet, this Comet Lovejoy should return again... in about 8,000 years.
[http://apod.nasa.gov/apod/ap141225.html]
[https://en.wikipedia.org/wiki/Columba_%28constellation%29]
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