NASA's Astronomy Picture of the Day features a calm night scene photographed in Poland. A crescent Moon rides above the Tatra Mountains, and bright Venus sits near it, slightly lower toward the horizon. NASA's caption identifies the brilliant point to Venus's left as Spica.
Why planets seem to meet stars
NASA's explanation notes that the word planet comes from the Greek for wandering star. Because planets change position against the background of fixed stars, they can look, from Earth, as if they are drawing near other objects in the sky. Astronomers call these encounters conjunctions. NASA stresses that they are not coincidences, since they obey the exact rules of celestial mechanics.
Spica is more than one star
The caption places Spica in Virgo, the Maiden, and ranks it among the sky's brightest stars, lying only about 250 light-years from us. In 1890 astronomers determined that it is a binary, made up of two massive blue stars circling each other every 4 days. NASA adds that it has since been reported that Spica is actually a triple system.
NOIRLab's constellation guide calls Spica, also known as Alpha Virginis, the brightest star in Virgo. The guide describes it as a binary, matching the long-standing view NASA cites, and does not mention the triple-system report. According to NOIRLab, the star's name derives from the Latin term for an ear of grain, tying it to the harvest.
The constellation's older identity
NOIRLab says Virgo started out in ancient Mesopotamia as The Furrow with a Barley Stalk, linked to a goddess of fertility. The observatory states that the figure became The Maiden after the zodiac was devised in Babylon around 400 BCE, give or take 10 years.
Sources
- NASA Science (Public domain (US government work))
- www.noirlab.edu
