Among the most famous constellations in the sky is a "modern" one that is quite invisible from most of the populated northern hemisphere: Crux , the Southern Cross. Some 60 degrees below the celestial equator, Crux is well-visible only roughly south of the Tropic of Cancer (a good reason to go to Hawaii). From nearly all the temperate southern hemisphere, Crux is circumpolar (never setting).

Aldebaran may have its own solar system. Recent, though still-unconfirmed, observations show that the star may be slightly shifting back and forth in response to a small body with a mass at least 11 times that of Jupiter and a two-year orbital period. We do not yet know if the body -- if it exists at all -- is a massive planet or a low-mass "brown dwarf," a failed star that is too small to run supporting thermonuclear reactions in its core.

Spica, the luminary of Virgo , becomes prominent in the southeast in northern spring evenings, and can easily be found by following the curve of the Big Dipper 's handle through Arcturus and then on down. Though a large constellation, Virgo, the Virgin, does not have much of any prominent stellar pattern, relying on Spica to tell us where it is.

A brilliant jewel set within the Milky Way , Antares guides us to one of the great constellations of the sky, the Zodiac 's Scorpius (or Scorpio), the celestial scorpion, one of the few constellations that actually looks like what it represents. Antares, a class M (M1.5) red superiant gleaming redly at the scorpion's heart, has a color similar to Mars .

In northern spring evenings, the "twin" stars Castor and Pollux of the constellation Gemini descend the northwestern sky looking like a pair of eyes staring down at the Earth. They are twins only in mythology, these warriors, Pollux fathered by Zeus and divine, Castor mortal, both placed in the sky to allow them to be together for all time.

It is quite close, only 25 light years away, from which we calculate a luminosity 16 times greater than the Sun. Almost the same distance as Vega, it is over a full magnitude fainter to the eye as a result of somewhat lower mass, which results in a lower surface temperature and smaller size.

Deneb makes the western apex of the famed Summer Triangle , which also incorporates Vega and Altair . All three of these white class A stars have similar surface temperatures, Deneb radiating at 8400 Kelvin. Though Vega and Altair are quite luminous, they are first magnitude primarily because they are close to us, averaging only 25 light years away. Deneb, on the other hand, may be as far as 2600 light years. Based on that distance, its luminosity of 160,000 Suns makes it about the intrinsically brightest star of its kind in the entire Galaxy.

Mimosa is a magnificent blue-white, very hot class B (B0.5) giant star 350 light years away with a temperature that soars to 27,600 Kelvin. Such heat causes the star to radiate most of its light in the invisible ultraviolet. To the eye, Mimosa would appear 3000 times brighter than the Sun ; if all the radiation is taken into account, the luminosity climbs over 11 times higher to 34,000 solar. From these figures we calculate a radius of 8.1 times that of the Sun, in good agreement with the value of 8.4 solar found from the small angular radius.

Regulus, glowing at the heart of Leo the Lion, one of the great constellations of the zodiac, is near the end of the list of first magnitude stars. At a distance of only 77 light years, it shines in our sky at magnitude 1.35, just marginally brighter than the next one down, Adhara , the second brightest star of Canis Major .

The names of all the first magnitude stars ring clearly to us; even the names of those in the southern hemisphere are well known. Adhara has escaped the fame it deserves. Also known as Epsilon Canis Majoris, it is actually the second brightest star in the constellation, and helps form the western leg of Canis Major , the larger dog. Look just below Sirius to find an outstanding triangle of bright stars. Adhara is at the lower right.

Castor and Pollux make a most attractive sight at the northern end of Gemini, Pollux an orange giant star, Castor a contrasting white. To the naked eye, Castor shines down to us as a seemingly ordinary hydrogen-fusing "class A" star that appears much like Vega, the "A" stars fairly hot, with temperatures between about 7000 and 10,000 degrees Kelvin. Castor has no physical relation with Pollux, and at a distance of 50 light years is half again as far away as its mythological companion. The telescope reveals Castor's real claim to fame as a remarkable multiple star.

In our "western" star lore, the stars with proper names come from the set that could be seen from the lands of the ancient middle east and Arabia, and do not include those of the far southern hemisphere, which is largely invisible below the horizon from northern lands. Yet those who needed the stars to find their way, the old navigators, also needed quick names for some of the stars and just made them up. "Gacrux" is a prime example of such a star, its name deriving strictly from its Greek letter name, Gamma Crucis, the third-brightest star in the constellation Crux , the Southern Cross.

In temperate northern summers, Scorpius glides above the southern horizon, its lower curved tail almost out of sight, while in the temperate southern winter, the constellation passes high overhead. At the end of the tail lies a pair of stars that represent the scorpion's "stinger," once called Shaula, from Arabic meaning exactly that. In more modern times, the name moved to the brighter of the pair, the fainter now called Lesath .