Chances are you'll receive or give a card with hearts on it today. The heart symbol may originate from a now-extinct plant called silphium. During antiquity it was popular as a perfume, seasoning, medicine and aphrodisiac and may be related to modern fennel. The seed or fruit's shape, stamped on 7th century B.C. silver Cyrene coins, looks nearly identical to the symbolic hearts of Valentine's Day.
Or its origin may go back to the writings of Galen and Aristotle, who described the heart as having three chambers with a small dent in the middle. Its first known depiction of romantic love dates to the 1250s.
Whatever its beginnings, the cartoon heart has beaten loudly ever since, not only on Earth but throughout the cosmos. Like true love, you'll find it in the least obvious spaces and places.
This pair of interacting ring galaxies has a lot of heart. Ring galaxies form when one galaxy passes nearly perpendicularly through the center of another, creating a gravitational "wake" that causes the stars to spring outward into a circle like a wave moving across a pond. This unique pair was found during a citizen science survey called the Galaxy Zoo. (Sloan Digital Sky Survey)
NASA's Mars Reconnaissance Orbiter spacecraft took this picture of a heart-shaped pit in the Red Planet's Hydaspis Chaos region in 2008. (NASA / JPL-Caltech / MSSS)
Apollo 12 astronaut Alan Bean photographed this heart-shaped crater and the legs of fellow moonwalker Charles Conrad Jr. during their 1969 mission to the moon. (NASA)
Astrophotographer John Chumack. of Dayton, Ohio captured this heartful sunspot on April 12, 2016. The heart-shaped part, called the umbra, only appears black because it's several thousand degrees cooler than the sun's surface. (John Chumack / galacticimages.com)
You won't find a colder heart in the solar system that at Pluto. Photographed by NASA's New Horizons spacecraft on July 13, 2015, the large, pale-pink plain, which measures approximately 1,000 miles (1,600 kilometers) across, is partially covered in nitrogen ice. The photo was made when the spacecraft was 476,000 miles (768,000 km) from the surface. (NASA / JPL / SwRI)
Call it a broken heart. NASA's Mars Reconnaissance Orbiter photographed this ridged, heart-shaped feature near the volcano Ascraeus Mons in 2014. Standing above the landscape, it likely formed in a volcanic process. (NASA / JPL-Caltech / Univ. of Arizona)
Love takes many forms. The sun blows a plasma heart of high-speed electrons and protons in the wake of a solar flare on Jan. 26, 2012. (NASA/ESA)
Saturn's moon Rhea, made of a mixture of ice and rock, is stamped with love as a result of a long-ago cosmic impact. Don't embrace this heart too closely; its temperature is around -280°F (-175° C) (NASA / JPL / Space Science Institute)
IC 1805, nicknamed the Heart Nebula, is a vast, glowing cloud of dust and gas almost 200 light-years across and 1,500 light-years away. Massive, newborn stars in heart's center excite hydrogen gas in the nebula to glow red. The nebula is located in Cassiopeia. (Hunter Wilson)
"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.