EarthSky | Spica, vivid beacon of Virgo, is 2 stars


Artist’s idea of the two giant, sizzling stars within the Spica system by way of UA Little Rock.

Spica is an in depth double star

The star Spica – aka Alpha Virginis – is the brightest star within the constellation Virgo the Maiden. From a distance of 262 light-years away, Spica seems to us on Earth to be a lone bluish-white star in a quiet area of the sky. But Spica consists of two stars and possibly extra. The pair are each bigger and warmer than our sun, and so they’re separated by solely 11 million miles (lower than 18 million km). They orbit their frequent heart of gravity in solely 4 days.

Earth is 93.3 million miles (150 million km, or 1 astronomical unit aka AU) from our sun. Spica’s two stars are solely .12 AU from one another, a small fraction of the Earth-sun distance.

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And so the 2 stars within the Spica system are individually indistinguishable from a single level of sunshine, even with a telescope. The twin nature of this star was revealed solely by evaluation of its mild with a spectroscope, an instrument that splits mild into its part colours.

Hot, sizzling, sizzling

Spica’s two stars are so shut, and so they orbit so rapidly round one another, that their mutual gravity distorts every star into an egg form. It’s thought that the pointed ends of those egg-shaped stars face one another as they whirl round.

The pair of stars are each dwarfs, brightening close to the tip of their lifetimes.

Spica is taken into account one of many hottest 1st-magnitude stars. The hottest of the pair is 22,400 Kelvin (about 40,000 F or 22,000 C). That’s blistering in distinction to the sun’s 5,800 Kelvin (about 10,000 F or 5,500 C). This star would possibly sometime explode as a supernova.

The mild from Spica’s two stars, taken collectively, is on common greater than 2,200 occasions brighter than our sun’s mild. Their diameters are estimated to be 7.8 and 4 occasions our sun’s diameter.

Spica is one in every of a number of vivid stars that the moon can occult (eclipse). Based on observations of how the star’s mild is extinguished when the moon passes in entrance, some astronomers suppose that it could not simply be a spectroscopic binary star. Instead, they really feel that there could also be as many as three different stars within the system. This would make Spica not a single or perhaps a double, however a quintuple star!

Brilliant blue-white star Spica with four rays against star field.
Our eyes see the star Spica as one star, although it’s actually at the least 2. We see it as distinctly blue-white. Photo by Fred Espenak at AstroPixels.
Crescent planet with two close, giant blue-white suns.
Artist’s idea of the celebs within the Spica system, as seen from a hypothetical planet. Image by way of

How to search out Spica

The finest night views of Spica come from northern spring to late northern summer time, when this star arcs throughout the southern sky within the night. In the month of May, as seen from the Northern Hemisphere, you’ll discover Spica within the southeast in early night. From the Southern Hemisphere, Spica is nearer to due east. From all of Earth in May, as evening passes, Spica seems to maneuver westward. Spica rises earlier every night in order that – by the tip of August – Spica might be considered solely briefly within the west to west-southwest sky as darkness falls.

There’s a fool-proof strategy to discover Spica, utilizing the Big Dipper as a information. Scouts and stargazers bear in mind this trick with the saying: Follow the arc to Arcturus, and pace on (or drive a spike) to Spica.

Look for the Dipper within the northern sky. It’s highest within the night sky in northern spring and summer time. Notice that the Big Dipper has a bowl and an extended, curved deal with. Follow the arc of the Dipper’s deal with outward, away from the Dipper’s bowl. The first vivid star you come to is orange Arcturus. Then drive a spike (or pace on) alongside this curving path. The subsequent vivid star you come to is Spica.

Spica shines at magnitude 1.04, making it the brightest mild in Virgo. It’s the Fifteenth-brightest star seen from anyplace on Earth. It’s just about the identical brightness as Antares within the constellation Scorpius, so generally Antares is listed because the Fifteenth and Spica because the sixteenth brightest. No matter.

Identify this stunning blue-white star with the Big Dipper’s assist to identify it within the sky. If you do, this star can be your buddy for all times.

Sky chart of Big Dipper with lines to Arcturus and Spica.
In northern spring, look northeast to southeast within the night. You’ll discover the Big Dipper within the northeast night sky. Follow the arc to Arcturus, and drive a spike (pace on) to Spica.
Star chart showing Big Dipper with line to Arcturus continuing to Spica.
In northern summer time, look northwest to southwest. You’ll discover the Big Dipper within the northwest night sky. But you’ll be able to nonetheless comply with the arc to Arcturus, and drive a spike (pace on) to Spica.

History and mythology of Spica

The identify Spica is from the Latin phrase for “ear” (of grain). The basic connotation is that Spica refers to an “ear of wheat.” Indeed, the star and the constellation Virgo itself had been generally related to the Greek goddess of the harvest, Demeter.

There are many names and tales for Spica’s constellation – Virgo – in mythology, and by affiliation with Spica as nicely. Fewer tales seek advice from Spica independently. Many classical references seek advice from Virgo’s stars as a goddess or with some affiliation with wheat or the harvest, resulting from the truth that the sun passes by means of Virgo within the fall. In Greece and Rome she usually was Astraea, the very personification of Justice; or Persephone, daughter of Demeter. In Egypt, Virgo was recognized with Isis, and Spica was thought of her lute bearer. In historic China, Spica was a particular star of spring referred to as the Horn.

One Arabic identify was Azimech, derived from phrases that means Defenseless One or Solitary One. This title could also be in reference to Spica’s solitary standing with no different vivid stars close by. But Spica is just not probably the most solitary star. That honor goes to Fomalhaut, generally referred to as the Autumn Star.

Spica’s place is RA: 13h 25m 12s, dec: -11° 09′ 41″

Antique colored etching of winged young woman in long dress holding a wheat ear, with labeled scattered stars.
Here’s a classical illustration of the constellation Virgo the Maiden, by way of Urania’s Mirror/ Wikipedia.

Bottom line: Spica is the brightest star in Virgo. Spica is at the least two stars orbiting extraordinarily shut collectively, distorting one another into egg shapes.

Virgo? Here’s your constellation

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