January Moon at Descending Node


   Wednesday morning January 22nd the waning crescent Moon crosses the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.

   On the date of the descending node the 27-day old thin waning crescent Moon will be about 4o to the west from the outer ringed planet Jupiter. Both rise within an hour of local time for sunrise.

   
   
   
   
   

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Moon, Mars, and Antares

   Monday morning January 20th, as they all rise together, the 25-day old waning crescent Moon will be within 5o from the planet ‘red planet’ Mars and the red star Antares in Scorpius the Scorpion.

   
   
   

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Mars on the Move

   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.

click on animated graphic to see it larger

Mars passing Antares – January 17-23 – 6 am CST

   Watch over the next several mornings and you will be able to determine which one is Mars and which is Antares as one of them moves past the other – as this animated graphic is showing. Also, relative to Mars and Antares the Moon is waning in phase as it zips past the two.

   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.

   
   
   

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Mornings Have Hang Ups!

   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.

   
   
   

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Saturn at Solar Conjunction – 2019

   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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January Moon at Perigee

   Our Moon reaches perigee, (closest to Earth), for this orbit, on Monday January 13th. At that time the Moon will be at a distance of 28.69 Earth diameters, 227,396 miles (365,958 km) from the Earth.

   On the day of the perigee Moon the 19-day old waning gibbous Moon will be over the eastern horizon late in the evening.

   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*
   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

   
   
   

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From a Crab to a Lion

   Over the next two evenings, January 11th and 12th, the waning gibbous Moon moves from near the Beehive Cluster, M-44, an open star cluster in Cancer the Crab to near the bright star Regulus in Leo the Lion. M-44, with an apparent magnitude of 3.50 in a dark sky without the Moon nearby is visible to the unaided eye and is easily seen with optical assistance like binoculars, or a low-power wide field eyepiece.


   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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