The Dimmest Constellation

You are probably familiar with at least the names of the twelve constellations of the zodiac:

Aries
Taurus
Gemini
Cancer
Leo
Virgo
Libra
Scorpius
Sagittarius
Capricornus
Aquarius
Pisces

But are you familiar with the twelve constellations that have no stars brighter than 4th magnitude?

Antlia
Caelum
Camelopardalis
Chamaeleon
Coma Berenices
Corona Australis
Mensa
Microscopium
Norma
Sculptor
Sextans
Vulpecula

All but two of these dim constellations are, at least in part, visible from southern Arizona; Chamaeleon and Mensa require a trip south to see.

The southern constellation Mensa, the Table Mountain (declination -70° to -85°) is a ghost of a constellation, exhibiting no star brighter than magnitude 5.1. That’s 17 times fainter than Polaris! In fact, that’s fainter than all the stars of the Little Dipper asterism! Mensa does have one claim to fame, however. The Large Magellanic Cloud, satellite galaxy of our Milky Way galaxy, straddles most of the border that Mensa shares with Dorado, the Swordfish.

Mensa is far and away the dimmest constellation. But Mensa is a small constellation, bested in size by 74 of the 88 constellations. So perhaps it is not too surprising that a small constellation is less likely to harbor a bright star. Another measure of faint, perhaps, is to determine which of these twelve constellations with no star brighter than 4th magnitude is largest. That might be more remarkable, because one is less likely to find no bright stars in a large area of sky than in a small area of sky. By this measure, Camelopardalis, the Giraffe, wins without a doubt. Camelopardalis is the 18th largest constellation, and yet contains no star brighter than magnitude 4.0. It is that empty region you might have not noticed midway between Capella and Polaris, best viewed at evening twilight’s end during the month of February each year.

Lovely Coma Berenices

One of the special joys of getting out under a dark rural sky this time of year is seeing the gossamer beauty of the surprisingly expansive star cluster called Melotte 111, also known as the Coma star clusterMel 111 makes up a large part of the constellation Coma Berenices, “Berenice’s Hair”.  This constellation, which entertains the North Galactic Pole as well as a gaggle of galaxies, can be found about midway between Denebola (some call the Coma star cluster the end of the “tail” of Leo the Lion) and Arcturus, as well as midway between Spica and the Big Dipper.  Coma Berenices is transiting the meridian this week as evening twilight ends.  At a distance of just 284 light years, the Coma star cluster is the third nearest star cluster to us, surpassed only by the open cluster remnant Collinder 285—the Ursa Major association (80 ly)—and the Hyades (153 ly).

Faintest Constellations

There are a dozen constellations with no star brighter than +4.0 magnitude.  Many of them are deep in the southern sky.  They are:

ANTLIA, the Air Pump
Brightest Star: Alpha Antliae, apparent visual magnitude +4.25

ANT-lee-uh

CAELUM, the Engraving Tool
Brightest Star: Alpha Caeli, apparent visual magnitude +4.45

SEE-lum

CAMELOPARDALIS, the Giraffe
Brightest Star: Beta Camelopardalis, apparent visual magnitude +4.02

cuh-MEL-oh- PAR-duh-liss

CHAMAELEON, the Chameleon
Brightest Star: Alpha Chamaeleontis, apparent visual magnitude +4.047

cuh-MEAL-yun, or cuh-MEAL-ee-un

COMA BERENICES, Berenice’s Hair
Brightest Star: Beta Comae Berenices, apparent visual magnitude +4.25

COE-muh BER-uh-NICE-eez

CORONA AUSTRALIS, the Southern Crown
Brightest Star: Meridiana, apparent visual magnitude +4.087

cuh-ROE-nuh aw-STRAL-iss

MENSA, the Table Mountain
Brightest Star: Alpha Mensae, apparent visual magnitude +5.09

MEN-suh

MICROSCOPIUM, the Microscope
Brightest Star: Gamma Microscopii, apparent visual magnitude +4.654

my-cruh-SCOPE-ee-um

NORMA, the Carpenter’s Square
Brightest Star: Gamma2 Normae, apparent visual magnitude +4.02

NOR-muh

SCULPTOR, the Sculptor
Brightest Star: Alpha Sculptoris, apparent visual magnitude +4.27

SCULP-ter

SEXTANS, the Sextant
Brightest Star: Alpha Sextantis, apparent visual magnitude +4.49

SEX-tunz

VULPECULA, the Fox
Brightest Star: Anser, apparent visual magnitude +4.45

vul-PECK-yuh-luh