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Spica the Semiquin Star
In 2026, the United States commemorates the 250th anniversary of its founding. At 250 light years away, the star Spica can be considered America's Semiquincentennial Star.
Traveling at 186,000 miles per second, the light that left Spica in 1776 as the founding fathers were signing the Declaration of Independence is just now reaching our eyes.
From the Big Dipper, follow the arc of the handle to the bright star Arcturus. Then spike down to Spica. Shown is July 4 at 10 PM.
Spica is the brightest star in the constellation Virgo, one of the constellations of the zodiac. Near the Fourth of July it appears about 30 degrees above the southern horizon after sunset.
Stars merit an integral role in historical celebrations. For the America flag, our founding fathers chose stars as the symbol of one of their greatest ideals--statehood. In addition to recognizing the prominence of stars in our iconography, you can proactively choose to value the real stars that inspired the stellar depictions.
Go easy on the night by supporting the Five Principles of Responsible Outdoor Lighting.
Consider that half of all human history has occurred between sunset and sunrise. Get outside at night, discover the starry firmament, and find the Anniversary Star Spica to celebrate the "semiquin." The other half of history--nighttime--awaits!
What is "Semiquin"?
Semiquincentennial combines three terms:
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semi (meaning half)
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quinquennial (meaning five years), and
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centennial (meaning 100 years).
When combined (0.5 x 5 x 100 = 250) it represents half of 500, or 250 years.
Astronomer Dr. James Kaler describes the star Spica:
SPICA (Alpha Virginis). 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. The star lies about 10 degrees south of the celestial equator, and practically on the ecliptic, the path of the Sun, and is regularly occulted, or covered over, by the Moon. The Sun passes Spica in the fall, rendering the star a harvest symbol that is reflected in its name, from Latin meaning "ear of wheat," the name actually going back to much more ancient times. Though at a distance of 250 light years (second Hipparcos reduction), Spica is still first magnitude (1.04), showing its absolute brilliance, the star visually 1900 times more luminous than the Sun. The apparent brightness is deceptive, however, as Spica actually consists of two stars very close together (a mere 0.12 Astronomical Units apart) that orbit each other in slightly elliptical paths with a period of only 4.0145 four days, which makes them difficult to study individually. Both are blue class B (B1 and B4) hydrogen-fusing dwarfs (the brighter nearing the end of its stable lifetime), making Spica one of the hottest of the first magnitude stars. The high temperature produces a great deal of radiation in the ultraviolet, which renders Spica vastly brighter than visually indicated. The brighter primary star has a temperature 22,400 Kelvin, a true luminosity of 12,100 Suns (after taking ultraviolet radiation into account), a radius 7 solar, (25 percent the separation between the two stars) and a mass 10.5 times solar, which may be enough to send it someday into a supernovaexplosion. The more poorly-known respective parameters for the secondary cooler star are 18,500 Kelvin, 1500 solar luminosities, almost 4 solar radii, and just 6 solar masses. Spica exhibits subtle brightness variations that were once thought to be caused by a grazing eclipse, each star slightly cutting off the light of the other each orbital period. The variation of 0.03 magnitudes is instead actually caused by the fact that the stars tidally distort each other and are not quite spherical, so as they orbit they present changing apparent diameters to the observer. The primary star is also a pulsating Beta Cephei (or Beta Canis Majoris) variable, which superimposes another variation of 0.015 magnitudes with a much shorter period of 0.17 days. The star is a strong source of X- rays, at least some of which seem to be produced when the winds that flow from the companions violently collide. Lunar occultaions yeild evidence that Spica is in fact multiple, with three other fainter components.
Written by Jim Kaler 4/10/98; last updated 7/03/09. Used with permission.
Bellatrix: Winter "Semiquin" Star
Spica is visible in the summer months, and being around 250 light years away can be deemed the USA's Semiquincentenial Star. Another candidate Anniversary Star about 250 light years away is bright Bellatrix, found in the winter constellation Orion.
Astronomer Dr. James Kaler writes about the star Bellatrix:
BELLATRIX (Gamma Orionis). If constellations could talk, they might well shout "unfair" at great Orion, the Hunter, one of only four constellations to have two first magnitude stars (the others Crux, the Southern Cross, Centaurus, the Centaur, and Canis Major, Orion's Hunting Dog). Moreover, it also has the fourth, seventh, and eighth-brightest SECOND magnitude stars. The brightest of these, Bellatrix, magnitude 1.64, follows immediately behind Castor (Alpha Geminorum), Gacrux (Gamma Crucis), and Shaula (Lambda Scorpii). (Numbers seven and eight within second magnitude are Alnilam and Alnitak, Epsilon and Zeta Orionis, the two brightest stars of the Belt.) As third brightest star in Orion, Bellatrix, at Orion's upper right corner, was appropriately assigned the Greek letter Gamma by Bayer. "Bellatrix," originally applied in medieval times to Capella and later transferred to Gamma Ori, translates from Latin as "the female warrior" (consistent with Orion as a giant warrior rather than as a hunter) and sometimes as the "Amazon Star." Blue-white luminous Bellatrix certainly lives up to its grand name. A class B (B2) "giant" (but see below), it is one of the hotter naked eye stars. With a temperature of 21,750 Kelvin it is in league with Spica, Adhara, and Shaula, as well as with the stars of the Belt. It seems not, however, to be physically a part of the Orion association of luminous O and B stars, as its distance of 252 light years (give or take 10) is only a quarter of the closest portion, the Orion Ia sub-association up and to the right of the Belt. Allowance for a large amount of ultraviolet light from the hot surface gives the star a luminosity of 7100 times that of the Sun. Combination with temperature yields a radius 5.96 times solar. The angular radius of Bellatrix, measured through interferometry, is only 0.00072 seconds of arc, which with distance gives a radius of 6.0 times solar, the beautiful agreement indicating that the various parameters are correct.
The theory of stellar structure and evolution clearly shows the star to be a hydrogen-fusing dwarf and to "weigh in" at 9.0 solar masses. That Bellatrix is classified as a B2 giant is not an error. It just means that the star has the spectrum of a giant in the standard classification scheme. Such dichotomies are common among the B stars, wherein true dwarfs are sometimes classed as giants or subgiants. With an age of 20 million years, the star has about seven million to go before the core hydrogen runs out and it becomes a true subgiant, then, as it evolves, a giant. Bellatrix's iron abundance is around 70 percent that of the Sun, which is typical for local class B stars. It was taken as a magnitude standard against which astronomers could follow the meanderings of variable stars. But Bellatrix perversely seems to vary a bit too, by a few percent over an undetermined period. At 9 solar masses, Bellatrix is on the edge of supernova candidacy. If it does not explode as one, it will become a massive white dwarf near the 1.4 solar mass limit above which white dwarfs collapse. Mass flow from a close companion might put the eventual white dwarf over the limit, again making the star a supernova. But no neighbor is close enough. Gamma Ori B has maintained a constant separation of 178 seconds of arc over the past 170 years and is likely a true, though very distant, companion. From its brightness it's probably an M0 red dwarf with a mass of about half that of the Sun. At a minimum distance of 13,800 Astronomical Units, it would take at least 525,000 years to orbit, making it a fragile connection indeed. From the perspective of Bellatrix A, the companion would be about as bright as Jupiter in our sky. Not that it matters, as the star is far too short-lived to support any sort of life. Much closer, at 6, 10, and 12 seconds of arc, are three 20th magnitude stars, but there is no evidence that they are anything but line of sight coincidences. If they are ever seen to orbit, they would then be cool red dwarfs.
Written by Jim Kaler 1/21/00; revised 5/23/14. Used with permission.