Venus-Jupiter Conjunction – Behind the Scenes

June 30

June 30

   Have you been following the motions of the Venus and Jupiter in the evening over the western horizon. The two planets, one an inner planet (Venus) and the other an outer planet (Jupiter), have moved noticeably closer to each other with the closest on Wednesday July 1st at 2 UT. For my time zone, CDT, this was at 10 pm CDT on Tuesday June 30th. At that time they were separated by about 0.5o, about the diameter of the full Moon, or your finger held out at arm’s length. As the days passed the two planets moved apart.

rotating-earth_at-night   So what is happening?
Several things, all involving the motions of Venus, Jupiter, the Earth and the Sun’s apparent motion, and of course the Earth’s rotation. The latter, Earth’s rotation, is the cause of the apparent east to west motion that all celestial objects follow across your skies. Other than being aware of the setting times this sky motion is not a major part of the conjunction between Venus and Jupiter.

   Starting with the Sun we can see over time that the Sun appears to move eastward at a rate of nearly 1o each day, which is the result of the Earth’s orbital motion, aka revolution, of nearly 1o each day. Keep this daily rate in mind because the other planets each move eastward at their own respective daily rate based on distance from the Sun. Venus as an inner planet takes 224.7 days to orbit the Sun so 360o / 224.7 = 1.6o; Earth takes 365.25 days to orbit the Sun so 360o / 365.2 = 0.98o; Jupiter takes 4331 days to orbit the Sun so 360o / 4331 = 0.083o.
Planetary Fact Sheet from NASA.

   What the preceding paragraph boils down to is that Venus and the Sun will catch up with slower moving Jupiter and pass by Jupiter. Venus as a Sun orbiter will move out away from the Sun toward the East and at some point will curve around and head back toward the Sun. Jupiter as an outer planet only moves eastward (excluding when it or any outer planet is in retrograde motion). So the Sun will catch up with Jupiter coming between the Earth and Jupiter, officially on August 26th when Jupiter is at solar conjunction. Venus will also catch with Jupiter but due to Venus being an inner planet it will pass Jupiter twice – east bound and then west bound which is currently the direction Venus is moving. Venus will pass between the Earth and the Sun around the middle of August putting Venus at inferior conjunction.

   This animated graphic shows the sky at the same time and illustrates how the sky shifts toward the west due to Earth revolution as well as the changing positions of Venus and Jupiter. Were you to measure how much the sky shifts daily, by carefully observing the altitude of Regulus, for example, above the horizon and measuring this altitude each evening at the same time from the same location, you would see that Regulus has shifted westward about 1o daily. You may also noticed that Regulus was at its previous days position 4 minutes earlier. So the net effect is that as each day passes the two planets are lower and lower above the horizon, and setting closer and closer to the time of sunset.

   See some pictures of the two planets taken nearly daily since June 19th.

   
   
   
   

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.

Venus and Jupiter in a Very Close Conjunction

   Wednesday July 1st at 3 UT (Tuesday June 30th at 10 pm CDT) the two planets Venus and Jupiter, as we see them from the surface of the Earth, will be about 0.34o from each other. This is less than the diameter of the full Moon, which coincidentally is less than 24 hours after this close conjunction between Venus and Jupiter.

   While the ‘celestial action’ is obviously over the western horizon be sure to watch for the near full Moon to be rising in the east. The waxing gibbous Moon is located to the left or east from the planet Saturn and the reddish star, Antares in the constellation Scorpius the Scorpion.

   Venus has moved within about 0.30o from Jupiter. See some pictures of the two planets taken nearly daily for about the last two weeks.

   
   
   
   

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.

Ceres at Opposition

   Monday June 29th Dwarf Planet Ceres reaches opposition. This places the Earth in between Ceres and the Sun, much like the arrangement of the Sun, Earth, and Moon during full Moon phase. When at opposition an outer planet is visible for most if not all of the night hours as it rises around sunset and then sets around sunrise.

   Ceres, at 7th magnitude, is currently within the boundaries of the constellation Capricornus the Sea Goat and is about 1o west from 4th magnitude Omega Capricorni. Ceres is bright enough to see with binoculars and regular observing will show Ceres moving away from Omega Capricorni.

   Learn more about Dwarf Planet Ceres by visiting the NASA Dawn mission web site where we have the Dawn spacecraft orbiting Ceres.

   
   
   

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.

Moon Saturn Conjunction

   Sunday evening June 29th the 12.5 day old waxing gibbous Moon is about 2o from the ringed outer planet Saturn. A great view with the naked-eye, binoculars or a telescope eyepiece.

   Meanwhile Venus has moved within about 1o from Jupiter. See some pictures of the planets and our Moon.

   
   
   
   

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.

Virgo Grabs the Moon

   Thursday evening June 25th the waxing gibbous Moon will be just out of reach from Virgo’s grasp, but still within about 3o from the bluish-white star Spica in Virgo the Maiden. This will make for an interesting binocular object as both will easily fit within the field of view of binoculars.
   Meanwhile Venus has moved within 3o from Jupiter. See some pictures of the planets and our Moon.

   
   
   
   

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.

June Moon at Ascending Node

may1-ascending-node   On Wednesday June 24th at 17:25 UT (12:45 pm CDT) our Moon will be crossing the plane of the ecliptic moving north. This is known as the ascending node, one of two intersections the Moon’s orbital path has with the ecliptic. The ecliptic is the Earth’s orbit and the Moon’s orbit is inclined about 6o from the ecliptic. So there are two node intersections, the ascending and descending nodes.

   
   
   
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.

June Apogee Moon

23jun-apogee   The Moon reaches apogee, (greatest distance from Earth), this month on Tuesday June 23rd at 17 UT (12 pm CDT). At that time the Moon will more or less be at a distance of 31.68 Earth diameters (404,132 km or 251,116 miles) from the Earth.
   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)

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

   The 7.5-day old waxing crescent Moon rises during the early afternoon hours and sets after midnight local time.

   
   
   

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.

Sun Enters Gemini

click on graphic to see it full size   Monday June 22nd at 2 UT, (Sunday June 21st – 8 pm CDT) the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Taurus the Bull and into the constellation of The Gemini Twins. This is the true or actual position of the Sun as opposed to the pseudoscience of astrology which usually has the astrological Sun one constellation ahead or east from the Astronomical Sun’s position.

   Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
   
   
   
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.

Sun Not in Cancer

   According to the pseudoscience of astrology the Sun enters the constellation of Cancer the Crab on Sunday June 21st at 16:38 UT (11:38 am CDT). When in fact the actual position of the Sun on this date is still within the boundary of the constellation of Taurus the Bull, but by very little. The Sun is very close to the eastern boundary for Taurus and the western boundary for the Gemini Twins, as this graphic and the banner graphic at the top of the page shows.
   Coincidentally this is also the June Solstice.
   Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
   
   
   
   
   
   
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.

2015 June Solstice

21june-ecliptic   Northern hemisphere spring comes to an end and its summer begins on Sunday June st at 16:38 UT (11:38 am CDT) when the Sun ‘reaches’ the celestial coordinates of 23.5o north declination and 6 hours right ascension. With respect to the Earth’s surface the Sun is described as over the Tropic of Cancer, 23.5o, north latitude of the Earth’s equator. At this same time the Sun is still within the boundaries of the constellation Taurus the Bull – but just barely. Interestingly about 12 hours later, June 22nd at 2 UT (June 21st – 9 pm CDT) the Sun ‘will move’ into the region of Gemini as it crosses the boundary between Gemini and Taurus.
   According to the pseudoscience of astrology the Sun, at this date, would be entering the astrological sign of Cancer the Crab.
Just had to include this!!   We know that it is the Earth’s orbital motion around the Sun that causes the sun’s apparent eastward motion among the stars in the background. This is how the Sun ‘reaches’ a celestial coordinate, how it ‘crosses’ the boundaries between constellations, or how it is ‘in’ a constellation.
   With respect to the southern hemisphere this is the end of their summer and start of their fall season. So thinking globally my preference has been to use the name of the month to designate the season change. Hence the use of the term June Solstice rather than summer solstice.

   
   
   
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.