The Sky This Week
U.S. Naval Observatory's Weekly Blog

Saturn is Back!

by Geoff Chester, USNO Public Affairs
27 July 2021

Saturn, imaged 2018 August 24 at the U.S. Naval Observatory
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor telescope

The Moon spends much of the week passing through the dim constellations of the autumn sky as she wends her way northward along the ecliptic.  Last Quarter occurs on the 31st at 9:16 am Eastern Daylight Time.  Luna keeps a lonely vigil until the first few days of August, when you can find her near the Pleiades star cluster before dawn on the 2nd.  On the following morning she lies northeast of the bright star Aldebaran.

August 1st is, for many of us, the unofficial date when we start our annual summer vacations.  It is also one of the ancient dates known as “cross-quarter” days that were once widely observed in medieval Europe.  These dates fell roughly mid-way between the dates of the astronomical seasons and provided important anchors in the lives of serfs and their masters.  The traditions associated with three of these cross-quarter days are still observed today as Halloween, Groundhog Day, and May Day, but hundreds of years ago these, along with the solstices and equinoxes, were the dates when landowners collected their rents from their tenants.  Cross-quarter days became ingrained in many pagan European cultures, and were especially important to the Celts.  The August date was celebrated as Lughnasadh in honor of the pagan god Lugh, who brought the bounty of the annual harvest to humankind.  As Christianity swept through Celtic lands the date became known as Lammas, or “Loaf-mass”, the day that freshly baked loaves of bread made from the first grain harvest would be brought to church to be blessed.  Lammas is still observed by the Church of England and is one of the key celebrations in the “Book of Common Prayer”.
 
It is usually around this time of year when most of us begin to notice the earlier daily setting of the Sun.  Sunset occurs about a minute later each successive evening as August begins, but by the end of the month the difference approaches two minutes.  Earlier sunsets mean that we have a bit more time each evening to enjoy the splendors of the summer sky, which for me is dominated by the bright star clouds of the Milky Way.  By 10:30 pm the densest of these clouds may be seen crossing the meridian in the southern part of the sky.  Gazing in this direction brings our line-of-sight to the center of our home galaxy, looking like a cloud of steam rising from the “spout” of the “Teapot” asterism in Sagittarius.  This “steam” consists of the unresolved light of millions of stars that blend into an amorphous haze and begins to resolve in a pair of binoculars.  My favorite views, though, are through my four-inch telescope with a low-power eyepiece.  Not only is the view chock full of uncountable stars, it is punctuated by compact concentrations of glowing gas, star clusters, and curious voids where no stars appear at all.  These “dark nebulae” are actually cool clouds of gas and molecular compounds that obscure the light of the stars behind them.  This dark material is easily viewed with the naked eye as you look higher along the Milky Way’s luminous band, particularly between the stars that form the Summer Triangle asterism.  In the Southern Hemisphere, where the central parts of the Milky Way lie overhead, many cultures created “constellations” out of these dark rifts and whirls snaking their way through the star clouds.

Venus continues to slowly edge her way up from the western horizon during the evening twilight hours.  You should have no trouble spotting her by 9:00 pm local time.  She is drifting eastward among the stars of the constellation of Leo, the Lion, and is gradually setting her sights on the bright star Spica, which may be seen low in the southwestern sky.  

Much harder to spot is Mars, which is now losing ground on the ever-advancing Sun.  The red planet will require binoculars and a very clear sky to successfully track down.  On the evening of the 29th he will be just over half a degree northeast of the star Regulus, a few degrees above the western horizon at 9:00 pm.
 
Saturn reaches opposition at 2:00 am EDT on the morning of the 2nd.  This is the date when the ringed planet rises at sunset and sets at the following sunrise.   He should be well-placed for viewing in the telescope by 11:00 pm.

Giant Jupiter rises around an hour after Saturn and should be a tempting telescopic target by local midnight.  These two planets offer a great view in small telescopes.  Jupiter lords over his four bright Galilean moons, and Saturn exhibits his spectacular system of rings.  I’m looking forward to spending many warm late summer evenings with these worlds.
 
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