November 20
The River's Bank
Sun Position
The Sun enters Sagittarius today, near -20° declination. Northern Hemisphere days are at their shortest stretch of the season; Southern Hemisphere is in pre-solstice summer.
Sky Highlight
With the Leonids fading and the Taurids winding down, November 20 is a quiet night for showers. The absence of a major active shower makes it a fine night for deep-sky work: Andromeda, Perseus, Cassiopeia, Taurus, and the Milky Way's outer disk are all well-placed from northern latitudes, and the autumn galaxy season is in full swing.
Deep Sky Object
M31, the Andromeda Galaxy, about 2.5 million light-years away, the nearest large spiral galaxy. November places it nearly overhead from mid-northern latitudes. Under dark skies, it is the most distant object visible to the unaided eye, spanning several times the apparent diameter of the full Moon. From the Southern Hemisphere it is lower in the north but still a dramatic binocular object.
Featured Star
Angetenar (τ² Eridani) is an orange giant 210 light-years away, spectral class K1III, a quiet, unremarkable evolved star that marks one of the many bends in the long, winding river Eridanus. It appears on historical star catalogs under various transliterations of its Arabic name, which references the bank or edge of the celestial river.
Around This Date
- November 20, 1889Edwin Hubble was born; his later measurements of Cepheid variables in nearby galaxies would establish the scale of the universe.
- November 24, 1639Jeremiah Horrocks and William Crabtree made the first scientifically recorded observation of a transit of Venus, confirming Kepler's prediction of the event.
The Milky Way arcs over quiet Eridanus tonight, and the river's bank star glows orange and unhurried in the east.