Category Archives: Astronomy

Uranus at Eastern Quadrature – 2019

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   Thursday January 23rd the position of the planet Uranus with respect to the Earth and the Sun places this ringed planet at what is called eastern quadrature. Uranus is at a 90 degree angle from the Earth. Think first quarter Moon as that is a fair comparison of the relative positions of the Earth, the Sun, and Uranus – or any outer planet. At this position Uranus follows the Sun across the sky from east to west as the Earth is rotating, meaning that Uranus rises after the Sun and sets after the Sun.

   So, where is Uranus? Look over the southwestern horizon after sunset for the stars making up the constellation of Aries the Ram. In particular look for the brighter star Hamal. About 11-12o down to the left from Hamal is the outer ringed planet Uranus.

   With a 5.78 apparent magnitude Uranus is just bright enough to be seen with binoculars as perhaps a very small dot. In the graphic I have enlarged the planet to make it more easy to see. Uranus is at about the naked-eye limit of visibility (6th magnitude)so it would take extremely dark skies to see it without optical assistance. Off to the right and lower are the four stars making up the familiar “Square of Pegasus” asterism.

   
   
   

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January Moon at Descending Node

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   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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Sun Enters Capricornus not Aquarius- – 2019

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 Monday January 20th at 9 UT the Sun in its apparent eastward motion along the ecliptic enters the boundaries of the constellation Capricornus the Sea Goat. This is the actual location of the Sun.
   Interestingly, according to the pseudoscience of astrology, 6 hours later, at 15 UT Monday January 20th, the Sun should be entering the constellation of Aquarius the Water Bearer.

   
   
   

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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Moon, Mars, and Antares

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   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

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   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.

   
   
   

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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Mornings Have Hang Ups!

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   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

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   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.
   
   
   

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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