Mercury at Western Elongation

19jan-mercury-east-elongation
   On Monday January 1st Mercury, the innermost planet, will reach its orbital position known as greatest western elongation at 22.7o. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows. Even though it sounds confusing at western elongation for either Mercury or Venus the inner planet will be to the right of the Sun as we view them, meaning that at western elongation an inner planet rises in the east before the Sun rises. And at eastern elongation with the inner planet on the left side of the Sun the inner planet follows the Sun across the sky setting after the Sun sets.
orbital-positions
   From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – out to the left (east) from the Sun to eastern elongation, then reverse and move westward (inferior conjunction) between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun (superior conjunction) and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!


   Mercury is visible in the morning skies before sunrise along with Mars, Jupiter, and the stars Spica and Antares, as this graphic shows.

   
   
   
   
   

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.

January Super Full Moon at Perigee


   Our Moon reaches perigee, (closest distance from Earth), for this orbit on Monday January 1st. At that time the Moon will be at a distance of 27.98 Earth diameters (356,600 km or 221,581 miles) from the Earth making this full Moon the year’s Super Moon.
   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*


   On the day of the perigee Moon the full Moon is above the eastern horizon about 1 hour after sunset local time. The Moon is located near the feet of the Gemini Twins.

   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

   Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   
   
   

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

Happy New Year

   Start off this New Year with something unusual, something that “only happens once in a blue moon.” How? There are two full Moons this month, with the first full Moon on January 1st, and the second full Moon, the ‘Blue Moon’, on the 31st.
   A Blue Moon month is a somewhat unusual Astronomical event described as a month with two full Moons that occur about every 2 1/2 years. What makes this Blue Moon month more interesting is that the full Moon of January 1st will also be a ‘super-Moon’ as the time for full Moon is close to the time for when the Moon is at perigee or its closest for this particular orbit. And to make this year a little more unusual is that during March there will be again two full Moons, second Blue Moon month.
   Even more exciting is that the second full Moon of January will pass through the Earth’s shadow giving us an opportunity to view a total lunar eclipse. Due to the timing for the eclipse viewing from my location will be limited to seeing about the first half the lunar eclipse as the Moon will be setting while still totally eclipsed. For the western Missouri and Eastern Kansas area the Moon enters the Earth’s darker shadow at approximately 5:48 am CST and totality begins at 6:51 am CST, and maximum at 7:29 am CST, five minutes after sunrise.
   For information about the eclipse for your location use the Hermit Eclipse Web Site.
Happy New Year
Gëzuar Vitin e Ri
سنة جديدة سعيدة
З Новым годам
Sretna Nova godina
Gelukkig Nieuwjaar
Bonne année
Glückliches neues Jahr
Ευτυχισμένο το Νέο Έτος
שנה טובה
Athbhliain faoi mhaise daoibh
Buon anno
明けましておめでとうございます
Felix Novus Annus
Feliz Ano Novo
С Новым годом
Feliz Año Nuevo
Heri ya Mwaka Mpya
Gott Nytt År
สวัสดีปีใหม่
Yeni Yılınız Kutlu Olsun

Thank you for your support.

   Here are a couple of short videos for your New Year’s enjoyment!

   So, where would you park the Space Shuttle??

   The consequences of a Black Hole.

   New Year’s Day includes a full Moon, the first of two full Moons this month. So as a way to ‘ring’ in the new year and hopefully not offend anyone, you will find below some of the Moon cartoons I have collected over the years and more than likely used in my classes! Apparently I was into cows at one point!!

new year
   
   
   
   

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.

Taurus Eyes the Moon

   Saturday evening December 30th the 13-day old waxing gibbous Moon will be 1-2o from the reddish star Aldebaran. The star is often described as representing the angry eye of Taurus the Bull. Regardless Aldebaran is at one end of a v-shaped group of stars that make-up the face of Taurus. These stars are part of an open star cluster, the Hyades, consisting of several hundreds of stars located about 150 light years from the Earth.

   About 10o from the Hyades, on the shoulder of Taurus, is another well-known open star cluster – the Pleiades. This is a cluster of approximately 1,000 stars located at a distance of 400-450 light years. Easily seen with the naked-eye several of the brightest stars form a small dipper-shape.
   
   
   

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.

Moon in Conjunction With Uranus

   Wednesday evening December 27th the 10-day old waxing gibbous Moon will be a few degrees from the ringed planet Uranus. Given the dimmer 5.7 apparent magnitude of Uranus, and the considerably brighter Moon’s -12.42 apparent magnitude Uranus will not be visible. However Uranus at this apparent magnitude, and without the interference from ‘moonlight’, would be visible with the unaided-eye, and would certainly be visible with binoculars.
   Nearby, below the Moon as it rises, is the dwarf Planet Eris, which at 18th apparent magnitude is definitely out of the visible range of all but larger telescopes.

   
   
   

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.

Mercury – Antares Conjunction

   Tuesday morning December 26th the innermost planet, Mercury, will be in a somewhat close conjunction with the heart of the Scorpius the Scorpion, the reddish star Antares. The two will be separated by about 8o and will be a bit too far apart to fit within the field of view of binoculars. Mercury has an apparent magnitude of -0.03 as compared with Antares 1.03 apparent magnitude.

   Looking higher above the horizon toward the south the planets Jupiter and Mars are visible as well as the blue-white star Spica in Virgo the Harvest Maiden. With a line-up of planets and Spica it is easy to visualize the ecliptic, the apparent path the Sun follows eastward throughout the year.
   
   
   

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.

Happy Holidays


   Have a safe, warm (or cool depending on your location), and happy holidays.
Animated graphic is set for 6:30 pm CST December 24th and 6:30 am CST December 25th

   
   
   

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.

Mercury Ends Retrograde Motion

   
mars-retrograde-ani   When the Earth’s orbital speed is compared to an outer planet there will be a time period when the faster moving Earth passes the outer planet. This sets up a temporary illusion where it appears as if the outer planet has reversed direction and is now moving backward toward the west, or in retrograde motion.
   On the other hand the two inner planets, Mercury and Venus, also revolve around the sun toward the east and go through a period of retrograde motion. However theirs is not as a result of the Earth’s faster orbital speed but rather it is their faster orbital speed compared with the Earth’s that gives them their retrograde motion. And unlike the apparent retrograde motion for an outer planet, Mercury and Venus do actually move in retrograde motion as this animated graphic is showing.
   So, on Saturday December 23rd the innermost planet, Mercury, ends its retrograde motion for this particular orbit and resumes its eastward motion. In the animated graphic the size for Mercury is exaggerated and the animation is set to a 1-day interval. It is showing Mercury moving westward as Venus is moving eastward. As Mercury moves along its orbit it eventually curves around and starts moving toward the east. This may be close to the day when Mercury reaches its furthest separation from the Sun on the west or right side of the Sun. That point is known as Greatest Western Elongation and is on January 1st. The counterpoint to this is when Mercury, or Venus, reaches their respective Greatest Eastern Elongation on the left or east side of the Sun.

   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

December Moon at Descending Node


   Friday December 22nd the waxing crescent Moon will be crossing 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 day of the node crossing the 4.75-day old waxing crescent Moon will be over the southwestern horizon an hour or so after sunset local time.
   
   
   
   
      

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

Saturn Reaches 2017 Solar Conjunction

10dec-saturn-solar-conjunction   Thursday December 21st 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 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. 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.