כּוֹכַב לֶכֶת (kokhav lekhet) — planet

Etymology

The word כּוֹכַב לֶכֶת is a Hebrew calque of the Greek planētēs (πλανήτης), meaning "wanderer." Ancient astronomers observed that most stars appeared fixed in the sky — their positions relative to one another never changing as the celestial sphere rotated — but a handful of bright objects "wandered" independently across the background of fixed stars. The Greeks called these planētai (wanderers). Hebrew translates this descriptively: kokhav (star) + lekhet (going, walking), literally "a going star."

The concept of seven planets — Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn — was known in Babylonian and Greek astronomy but appears only indirectly in the Hebrew Bible, where the Sun and Moon are named but the other planets are absent (though Isaiah's "Queen of Heaven" and "Helel ben Shahar" may refer to Venus). The two-thousand-year prohibition in Jewish law against studying astrology — bound up as it was with pagan star-worship — appears to have kept Hebrew writers from naming the planets for centuries. Jewish writers who did discuss the seven planets in the first century CE, such as Josephus and Philo of Alexandria, wrote in Greek for non-Jewish audiences.

The paradigm shift came in third-century Babylonia, attributed to the Amora Shmuel — personal physician to Rabbi Judah the Prince before emigrating to Babylonia, where he became one of the two foremost sages of the first generation of Amoraim. Shmuel was a skilled astronomer (the Talmud quotes him saying he knew the pathways of the sky as well as the streets of his own city, Berakhot 58b). He appears to have been the one who devised Hebrew names for the planets that stripped away pagan associations: the Sun became חַמָּה ("the hot one") rather than the Canaanite god Shemesh; the Moon became לְבָנָה ("the white one") rather than the god Yareach; Mercury became simply כּוֹכָב ("the star"); Venus became נֹגַהּ ("gleam"); Mars became מַאְדִּים ("the reddish one"); Jupiter became צֶדֶק ("justice," based on astrological attribution); and Saturn became שַׁבְּתַאי (associated with the Sabbath day, its ruling day of the week).

This system endured through the Copernican revolution of 1543, the invention of the telescope in the early 17th century, and the subsequent discovery of Uranus (1781), Neptune (1846), and dozens of asteroids and minor planets. As each discovery arrived, Hebrew needed new names. The Academy of the Hebrew Language in 2009 finally gave Uranus and Neptune Hebrew names: Uranus became אוֹרוֹן ("small light," echoing its foreign name) and Neptune became רַהַב (a biblical name for the Canaanite sea-deity, parallel to Roman Neptune). Pluto, demoted to "dwarf planet" status in 2006 after the discovery of the similarly-sized Eris, had already acquired the Hebrew designation פְּלוּטוֹ without a Hebrew replacement being required.

Key Quotes

"נהירין לי שבילי דרקיעא כשבילי דנהרדעא" — Shmuel, Babylonian Talmud, Berakhot 58b ("The pathways of the sky are as clear to me as the streets of Nehardea")

"כוכבי לכת... כוכב שהוא אינו קבוע" — Talmudic literature, c. 3rd century CE (earliest use of the compound)

Timeline

• Pre-biblical period: Babylonian astronomy defines seven wandering celestial bodies
• 1st century CE: Josephus and Philo mention seven planets in Greek writings for non-Jewish audiences
• 3rd century CE: Shmuel of Babylonia coins Hebrew names for the seven planets; term כּוֹכַב לֶכֶת established in Hebrew
• 1543: Copernicus publishes heliocentric model; traditional seven-planet system disrupted
• 1781: William Herschel discovers Uranus (eventually named after the Greek sky-god)
• 1801–1807: Ceres, Pallas, Juno, Vesta discovered; later reclassified as asteroids
• 1846: Neptune discovered; named by Urbain Le Verrier
• 1930: Pluto discovered by Clyde Tombaugh, named by 11-year-old Venetia Burney
• 2006: Pluto reclassified as "dwarf planet" (כּוֹכַב לֶכֶת גַּמָּד); planet count drops to eight
• 2009: Academy of the Hebrew Language coins אוֹרוֹן (Uranus) and רַהַב (Neptune)

Related Words

• כּוֹכָב — star
• לֶכֶת — going, walking (from root ל-כ-ת)
• חַמָּה — Mercury (also: the Sun, heat)
• לְבָנָה — the Moon (also: white)
• נֹגַהּ — Venus (also: gleam, brightness)
• מַאְדִּים — Mars (also: red)
• צֶדֶק — Jupiter (also: justice)
• שַׁבְּתַאי — Saturn
• אוֹרוֹן — Uranus (coined 2009)
• רַהַב — Neptune (coined 2009; also: biblical sea-deity)
• לַוְיָן — satellite/moon (artificial; coined by Yitzhak Avinery 1957)