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NightSky Friday: The Hare and the Dove

By Joe Rao
SPACE.com's Night Sky Columnist
posted: 07:30 am ET
30 January 2003

JANUARY 30

The attention of many skywatchers is now drawn to the star pattern that always takes center stage on cold wintry nights: Orion, the Mighty Hunter. He is the most spectacular group of the winter season, the most brilliant constellation to be found anywhere in the sky.

Orion tends to draw attention away from some of nearby dimmer groups, such as the two somber figures that lie beneath it: Lepus, the Hare and Columba, the Dove. able -->


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The sky as of 8:30 p.m. local time from mid-northern latitudes in late January. And, below, an illustration of the Hare and the Dove as the ancients saw them.

* Graphic made with Starry Night Software
 
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The Hare

Lepus is composed of a modest group of faint stars that seem to be arranged in the shape of a bow tie. The sword of Orion points toward it. Its an ancient pattern, and a surprising number of early peoples tended to associate this celestial Hare with the Moon, although to the Arabs the brighter stars in a crude rectangle represented four camels quenching their thirst. Since Orion particularly liked hunting hares, it seemed appropriate to place one below his feet in the sky.

Its brightest star, Arneb, is a double star whose components are about 3rd and 11th magnitude. On this scale, larger numbers represent fainter objects, and nothing beyond about magnitude 6.5 is visible to the unaided eye.

The pairing of these two stars is likely an illusion of sorts. The fainter companion is probably not a true physical companion but only appears that way because it just happens to be in the same line of sight as seen from Earth.

One interesting variable is labeled R Leporis. It is often compared to Mira Ceti, the "Wonderful Star" of Cetus, the Whale, because, like Mira, R Leporis appears to pulsate in size and has an irregular period of roughly 432 days, varying in brightness between about 7th and 9th magnitude. (You'll need binoculars or a small telescope to see it.)

The variable star was first noted in October 1845 by the astronomer J.R. Hind of London, who described it as "the most intense crimson, resembling a blood-drop on the black background of the sky." Other observers have noted that it appears as "an intense smoky red; a glowing coal; a ruby." Observing it nearly a century ago (in 1905), Agnes Clerke remarked that even the ruddy colors of Antares and Betelgeuse were "mere pale shades" when compared with the wine-red hue of R Leporis.

Hinds Crimson Star is a very cool giant, ranging from 3,500 to 4,000 degrees Fahrenheit (1,900 to 2,200 Celsius). Its spectrum shows that it belongs to a rare class of stars referred to as spectral class N and shows very strong features of molecular carbon.

The Dove

In contrast to Lepus, Columba is not among the 48 constellations usually attributed to the ancients. The origin of its naming is uncertain, but it is believed to have been created by Petrus Plancius, a sixteenth century Dutch theologian and mapmaker. It indeed does appear as a full-blown dove with olive branch in many of the old star atlases.

Interestingly, just to the east of Columba is the constellation of Puppis, which represents the stern of a large sailing vessel, Argo Navis. For observers in the northern United States as well as all of Canada and Europe, the various components of this celestial ship lie for the most part below the horizon. Although Jason used this ship to seek the Golden Fleece, it is sometimes associated with Noahs ark. And indeed, Columba represents the dove Noah sent forth after the flood to search for land, hence its original name: Columba Noachii (Noahs Dove).

Within Columba's boundaries is the place from which the Sun is moving, the "antapex of the Suns way." In 1718, Sir Edmund Halley determined that the stars were not fixed in position and that they moved across the sky in what is often called their proper motion. Relative to the nearby stars, the Sun, and thus we inhabitants of Earth are moving directly away from a spot in the sky in northern Columba at about 12.5 miles per second.

We are heading toward the opposite part of the sky, a region of space between the constellations Lyra, the Lyre and Hercules in the summertime sky.

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Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

DEFINITIONS

Degrees measure apparent sizes of objects or distances in the sky, as seen from our vantage point. The Moon is one-half degree in width. The width of your fist held at arm's length is about 10 degrees.

1 AU, or astronomical unit, is the distance from the Sun to Earth, or about 93 million miles.

Magnitude is the standard by which astronomers measure the apparent brightness of objects that appear in the sky. The lower the number, the brighter the object. The brightest stars in the sky are categorized as zero or first magnitude. Negative magnitudes are reserved for the most brilliant objects: the brightest star is Sirius (-1.4); the full Moon is -12.7; the Sun is -26.7. The faintest stars visible under dark skies are around +6.

 

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