Friday morning January 17th, before sunrise, the last quarter Moon will be about 5-6o from the blue-white star Spica in Virgo the Harvest Maiden. However the celestial highlight coming up is further east or lower and closer to the eastern horizon where there are two reddish-colored objects of about the same apparent brightness or magnitude. One object is the planet Mars and the other is the star Antares in Scorpius the Scorpion.
There is an interesting connection between the star Antares and the planet Mars, based on their similar reddish color. There are times like this year when the two are close and part of the mythology surrounding the two suggests that the star was given its name so as to not confuse it with the planet Mars. The name Antares comes from the Greek word translated to ‘Rival of Mars’.
Whenever that was historically Mars was probably known as one of the ‘wandering stars’ from the Greek word ‘planetai’. So with its reddish color, like blood, this ‘wandering star’ came to represent Mars, the ‘G-d of War’. Antares, on the other hand is a red supergiant star with a diameter estimated to be such that if it were at the center of our solar system Antares would fill the solar system out to around the main asteroid belt between Mars and Jupiter.
Northern Hemisphere winter in addition to chilly or cold mornings may sort of warm you, at least in your mind. If you are outside looking at the sky, over the eastern horizon is a large triangular shape of three bright stars. One star each from three different constellations. Deneb in Cygnus the Swan, Vega in Lyra the Harp, and Altair in Aquila the Eagle. This is the asterism (star pattern but not a constellation) the Summer Triangle. There, warmer now?!
So if you are outside checking out the Summer Triangle, or perhaps Mars and nearby Antares and you have an optical aid like binoculars or a lower power wide-field eyepiece in your telescope aim them and your eyes toward the star Altair. In dark enough skies you can make out the stars making up Sagitta the Arrow a few degrees away from Altair.
As Altair is rising and with binoculars move the field of view up to the left until the stars of Sagitta fill the field of view. This small constellation, yes a constellation, could be used as a sort of pointer stars to look a few degrees away for a small open star cluster, Brocchi’s Cluster, or more commonly known as the ‘Coathanger Cluster’.
So if mornings with stars like this don’t warm you up then wait a few months of Earth revolution and these same stars will be showing up in the warmer evening skies of Northern Hemisphere summer and fall.
Monday January 13th the planet Saturn will have reached the astronomical coordinates that officially place it at solar conjunction. From our perspective the planet is behind the Sun, or on the opposite side of the Sun from the Earth.
In reality it is not as much as Saturn moving behind the Sun as it is the Sun passing in front of Saturn – or so it seems. As a distant outer planet Saturn moves more slowly around the Sun than the Earth does. One year on Saturn is equal to 29.7 years (10,832 days) on Earth. So in one Earth day Saturn would travel how much of the 360o orbit around the Sun? That would amount to approximately 0.033o each day.
The Sun, in its apparent motion along the ecliptic moves at the rate the Earth is moving which is 0.99o each day. So with the Sun’s apparent motion (0.99o/day) it quickly, relative to Saturn, passes Saturn while both are moving eastward. This animated graphic starts with Saturn and the Sun above the horizon a couple of hours after sunrise. The animation is set for 1-day intervals showing the Sun moving eastward away from Saturn. The sky is purposely left dark to show Saturn more easily.
So with that in mind you could start watching for Saturn to reappear in the morning skies later next month.
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Tuesday evening January 7th the 13-day old waxing gibbous Moon will be about 3-4o from the reddish star Aldebaran. Aldebaran is known as the ‘angry’ red eye of the constellation pattern Taurus the Bull.
Aldebaran is located at one end of a v-shaped cluster of stars making up the face of the Bull. This group of stars are all part of an open star cluster known as the Hyades. They are one of two naked-eye visible open star clusters within the boundaries of the constellation. The other one is the little dipper-shaped group known as the Pleiades.
Friday evening December 28th over the western horizon around sunset look for the 3-day old waxing crescent Moon to be about 2o from the inner planet Venus. Both will easily fit within the field of view of binoculars.
I should clarify that the view of the conjunction as described above is based on my latitude and longitude in the midwest U.S.A. The separation between the Moon and Venus will vary depending on your location. At other geographic locations, like southern South America and Antarctica, the crescent Moon occults Venus.
The occultation begins at 2 UT or for my time zone at 9:00 pm CST.
This animated graphic is set for a latitude of 56oS to show the Venus Occultation. Venus was also enlarged to make it more visible in the graphic.
For the past several months the outer planets Jupiter and Saturn have been the brightly shining ‘evening stars’ over the western horizon at sunset. They have recently been joined by the inner planet Venus, but at the same time as Venus has become more prominent each evening Jupiter and Saturn have been setting earlier as they gradually move closer to the horizon at sunset.
And now Jupiter is no longer in the ‘picture’. So what happened to Jupiter, and will soon happen to Saturn? All solar system objects orbiting the Sun beyond Earth’s orbit move at a slower pace around the Sun than the Earth. The Sun has an apparent motion toward the east which is the same as the Earth’s actual motion. So what happens is that over time the Sun catches up with Jupiter, then Saturn. Eventually the Sun passes them and the planets become visible in the morning skies rising ahead of the Sun.
At some point along their respective orbital path they will be on the opposite of the Sun from the Earth. This is known as solar conjunction, and that is where Jupiter will officially be on Friday December 27th.