About Bob Riddle

Currently: Retired from the physical classroom (May 2017) but not yet finished learning and teaching. Column Editor, Scope on the Skies - Science Scope Magazine; NASA/JPL Solar System Educator Program - Solar System Ambassador Program, and Solar System Ambassadors Program.

Uranus at Western Quadrature – 2020

   Sunday August 2nd the position of the planet Uranus, with respect to the Earth and the Sun, places this ringed planet at what is called western quadrature. At that orbital position Uranus, and actually any outer planet, is at a 90 degree angle from the Earth as this graphic shows, and also this graphic. Think third quarter Moon as that is a fair comparison of the relative positions of Earth, Sun, and Uranus.
    At western quadrature Uranus leads the Sun across the sky from east to west as the Earth is rotating, meaning that Uranus rises before the Sun and also sets before the Sun.

   
   
   This is a short video clip from a much longer video that I made as part of a live musical performance called “Orbit” at the Gottleib Planetarium in Kansas City Missouri during May 2011.

   
   
   

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.


Also Follow me and other great resources at Feedspot.

A Saturday *2fer

   Saturday August 1st there will be two opportunities for planet and Moon viewing. (a ‘2fer’)
   On Saturday morning before the Sun rises watch for the innermost planet Mercury to be about 6-7o from Pollux, one of the two ‘twin stars’ of Gemini the Twins, as this graphic is showing. Venus, if you haven’t noticed, is shining very brightly higher above the southern horizon.
   Then Saturday evening after sunset look for the 12-day old waning gibbous Moon to be about 1-2o from the outer ringed planet Jupiter and about 4-5o from another outer ringed planet, Saturn.
   
   
   
   
   *2fer – suggesting that it is possible to get two instead of one (2 for 1) of whatever is being got.
   
   
   

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.


Also Follow me and other great resources at Feedspot.

July Moon at Descending Node #2

   Friday July 31st the 11-day old waning gibbous 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 has with the ecliptic. The ecliptic is actually 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.
   On the day of the node crossing the waning gibbous Moon will be a few degrees from the outer planet Jupiter and few more degrees from Saturn.

   Does our Moon actually go around the Earth as many graphics show? 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)

   
   
   
   
   

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.


Also Follow me and other great resources at Feedspot.

There’s a Comet in my Hair!

   Here’s perhaps a chance to catch an interesting picture of the comet. Over the southwestern horizon Comet 2020 F3 (NEOWISE) may still be visible although its apparent magnitude (5.50) and its tail have been steadily decreasing.

   The comet is currently passing by a small y-shaped group of stars (naked-eye view) that are part of the constellation Coma Berenices over the nights of Wednesday July 29th and Thursday July 30th. Both the comet and the stars will be within the field of view of binoculars as the comet passes by the stars.

   The stars of the small constellation Coma Berenices represent the hair cut from Berenice, an Egyptian Queen, whose hair was a religious offering as a bargain for her husband to return safely from war.
   
   
   
   
   
   
   
   
    And, unmistakable over the eastern horizon is the Moon, and just rising the planets Jupiter and Saturn.

   
   
   

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.


Also Follow me and other great resources at

Scorpion Grabs for the Moon!

   Wednesday evening July 29th the 9-day old waxing gibbous Moon will be 3-4o from the reddish star Antares. This star is the heart of Scorpius the Scorpion and shines with a 1.0 apparent magnitude. Rising in the east are two of the giant outer ringed planets, Jupiter and Saturn. Over the southwest is Comet 2020 F3 (NEOWISE).

   
   
   
   
   
   

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.


Also Follow me and other great resources at Feedspot.

Moon – Spica Conjunctions


   Over the next two evenings, July 25th and 26th, the Moon, as it waxes from crescent to first quarter, will be passing the bluish-white star Virgo. Virgo is the brightest star in the constellation Virgo the Harvest Maiden.

   The Moon often, as in monthly, passes by Spica. Sometimes coming very close and sometimes a bit further away as these two graphics show. Spica lies along the ecliptic and since the Moon’s orbital path follows the ecliptic, crisscrossing the ecliptic regularly, a conjunction between Spica and our Moon is not that unusual.

   Off to the east two of the outer planets, Jupiter and Saturn are rising. Both are easy to see even if you are standing across from a night Baseball game!

   
   
   

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.


Also Follow me and other great resources at Feedspot.

July Moon at Perigee

   Our Moon reaches perigee, (closest to Earth), for this orbit, on Friday July 24th. At that time the Moon will be at a distance of 28.87 Earth diameters, 228,913 miles (368,400 km) from the Earth.

   On the day of the perigee Moon the 4-day old waxing crescent Moon will be over the southwestern horizon after sunset. Off to the east and just rising are the planets Jupiter and Saturn. However look toward the northwest to see Comet 2020 F3 (NEOWISE) below the stars of the Big Dipper.

   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)

   
   
   
   
   
   

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.


Also Follow me and other great resources at Feedspot.

Sun Actually Not in Leo


   According to the pseudoscience of astrology, Wednesday July 22rd the sun will be entering the constellation of Leo the Lion. In fact the Sun is still within the boundaries of the constellation Cancer the Crab, having just entered that region two days ago.
   The difference between the two locations of the Sun, the correct astronomical vs. the incorrect astrological, is due to the effects of precession, or more specifically, the precession of the Earth’s axis. The Earth wobbles on its axis like a spinning top does as the top slows down. So, in approximately 26,000 years the Earth will have spun, or wobbled one time. This is a repetitive cycle and over the course of one precession cycle the poles of the Earth trace out a circle against the background stars over their respective pole. any star on or nearest to this precession circle is the pole star. Currently the north pole of the Earth points toward Polaris and within this century, due to precession, will point the closest it will be, and then over time the Earth’s north pole will shift away.
   Another effect of precession has been to cause the celestial grid system to shift moving the original signs of the zodiac by at least one constellation to the west. In other words the Sun is more to the east which in effect means that whatever your zodiacal sign may be according to astrology, you are really the constellation to the west, or before it according to Astronomy.
   Click here to read a little more about precession from a previous blog.
   The Science of Astronomy has its roots in astrology with the origins of astrology beginning several millennia ago possibly by the Babylonians. Regardless of its origins the basis for at least Sun astrology, the popularized version printed in newspapers, is the position of the Sun relative to stars in the background. However we now know that due to the effects of precession the Sun’s position is no longer as it was during the beginnings of astrology.
    The slideshow below shows the sun’s position within Cancer on July 22nd 2016 AD, and then shifts to show the sun in Leo 4,000 years ago on 22 July 2016 BC. Precession has shifted the sun’s position one constellation to the west.

This slideshow requires JavaScript.

   
   
   

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.


Also Follow me and other great resources at Feedspot.

Mercury at Western Elongation

   On Wednesday July 22nd Mercury, the innermost planet, will reach its orbital position known as greatest western elongation at 20.1o. 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.

   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!

   There is a lot to see and a few things you cannot see on the morning of Mercury’s western elongation. Going by relative apparent magnitudes Mercury (0.33), Venus (-4.43), Mars (-0.89) are all easily visible as bright to very bright star-like objects. On the other hand those not seen with the naked-eye but are still above the horizon in the morning skies include: Uranus (5.80), Eris (18.64), Neptune (7.84), Ceres (7.40)

   
   
   
   
   

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.


Also Follow me and other great resources at Feedspot.

Sun Enters Cancer – 2020

19july-view-from-earth   Monday July 20th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Gemini the Twins and into the constellation of Cancer the Crab. 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.

   
   
   

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.


Also Follow me and other great resources at Feedspot.