January Apogee Moon

   Our Moon reaches apogee, (furthest from Earth), for this orbit, on Thursday January 21st. For this apogee the 9-day old waxing gibbous Moon will be at a distance of 31.70 Earth diameters, 251,282 miles (404,400 km) from the Earth.

   On the date of the apogee, and high above the southwestern horizon, is the 8-day old waxing gibbous Moon. The Moon will be about 7o to the east from the planet Mars, and about 9o from the outer planet Uranus.


   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 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

   
   
   
   

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Moon-Mars-Uranus Conjunction

   Wednesday evening January 20th the 8-day old first quarter Moon will be about 4o from the outer planet Uranus and about 6o from Mars. Over the next couple of days Mars and Uranus will be separated by about 1-2o as the faster moving Mars passes by Uranus.
   Earlier in the evening outer Planet Neptune and two Dwarf Planets, Eris and Ceres are also above the horizon. However with apparent magnitudes ranging from 8.0 to 19.0 none of these three would be visible without some sort of optical assistance,

   
   
   

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Moon – Mars Conjunction

   Over the next two evenings the 12-13 day old waxing gibbous Moon will pass by the ‘Red Planet’ Mars coming within about 7-8o on Wednesday October 28th and within about 3-4o on Thursday evening October 29th.

   
   
   

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Mars at 2020 Opposition

Mars at Opposition   Tuesday October 13th Mars will reach a point in its orbit around the Sun where it is at opposition relative to the Earth. At opposition The Earth is between the Sun and Mars, or for that matter, between any of the outer planets and the Sun. At opposition both the Earth and the planet at opposition will have near identical heliocentric longitude. The opposition of Mars sometimes happens around the time that Mars is at its respective perihelion, closest to the Sun. If opposition happens during or near when the Earth is at its respective aphelion, furthest from the Sun, (first few days of July) then Mars will appear larger relative to when these dates are further apart.

Where is Mars Now?

What is opposition?
orbital-positions   The outer planets reach opposition when the Earth has moved into a position with the Sun on one side and the outer planet on the other side. Because all planets orbit in the same direction (toward the east), and all follow orbits that are slightly more elliptical than circular, oppositions occur at regular intervals of about 12 months (except for Mars). Mars is considerably closer to Earth and is moving faster than the other outer planets, so it takes approximately 26 months for Earth to catch up with Mars for an opposition.

   
   
   

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Moon May Get Stung!

   Sunday morning October 11th the 23.6-day old waning crescent Moon will be about 2o from the open star cluster M-44, also known as the Beehive Cluster. This is a group of a few hundred stars located within the constellation Cancer the Crab.
click on graphic to see it larger
   Despite the large difference in apparent magnitude (Moon: -11.4 : Beehive Cluster: 3.4) The Beehive Cluster could still be visible with an optical aid or camera.

   
   
   
   
   
   
   
   
   

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Taurus Eyes the Moon!

   Late Tuesday evening October 6th the 20-day old waning gibbous Moon will be 4-5o from the reddish star Aldebaran in the constellation Taurus the Bull.

   Aldebaran with its reddish color is known from mythology as the ‘angry eye‘ of the Bull. Aldebaran is also one of the two end stars in the v-shaped group of stars making up the face of the bull. This group of stars is an open star cluster, the Hyades, and is one two open star clusters easily seen with the unaided eye within the constellation. The tiny dipper-shaped Pleiades is the other open star cluster.

   
   
   

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Jupiter Corrects Its Reversal

jupiter-ani   On Saturday September 12th in a move that comes about annually, Jupiter will once again reverse its direction from moving toward the west to moving toward the east.
   For about the past 4 months Jupiter has appeared to be moving westward (toward the right) rather then toward the east. This happens as the faster moving Earth catches up with and then passes by Jupiter. This apparent westward motion of Jupiter is known as retrograde motion and for Jupiter it’s retrograde motion comes to an end on September 12th when Jupiter resumes its normal orbital motion toward the east, or to the left as we view Jupiter from the Earth.
   Since retrograde is a reference to motion and means backward or reverse motion, then the opposite of retrograde would be prograde motion. So it would be correct to describe Jupiter as having resumed prograde motion. However you would probably get a blank look from those you say this to! So stick with “direct motion” or just say that Jupiter orbits the Sun to the east as we see it from Earth.
   Jupiter is located over the southern horizon after sunset local time. It is about 7-8o to the west from Saturn.

   
   
   
   

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Neptune at Opposition – 2020

   Friday September 11th the outer planet Neptune reaches a position in its orbit around the Sun when it is on the opposite side of the Earth from the Sun. This coincidentally is known as opposition, and it is an orbital position which only the planets further from the Sun than the Earth may reach.
   At opposition an object orbiting the Sun beyond Earth’s orbit rises and sets in a fashion similar to our Moon when it is at full phase, in that the object at opposition rises at sunset and sets at sunrise.
   Currently Neptune rises at sunset and by late evening is over the southeastern horizon. Neptune has an apparent magnitude of 7.88 so it is beyond unaided-eye visibility but could be visible with large aperture telescopes or with a camera.

   
   
   

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Planetary Line-Up Ecliptic Style

   Look at the arrangement of the planets in the graphics below. One of the defining aspects of our solar system is the arrangement of the planets outward from the Sun. Not by size or distance but rather how their respective orbital paths around the Sun are all vertically arranged near the Earth’s orbital path, or as it is typically referred to as the Ecliptic or the Plane of the Ecliptic. The 8 classic planets all orbit the Sun with an orbital path that is up to about 8o from the ecliptic. This is called inclination. The table shows inclination relative the Earth’s orbit and also relative to the Sun’s center, its equator.
    Click on this link to read a previous posting (Tales Along the Ecliptic) about the ecliptic and inclination.
   During this week as the Moon moves eastward it will pass by the outer ringed planet Neptune Tuesday and Wednesday evenings September 1st and 2nd as the graphics show. However given the tremendous difference in apparent magnitude between the two (full Moon: -12.64 ; Neptune: 7.81) Neptune will not be visible, at least not while the Moon in nearby.


   Keep following the Moon as it orbits eastward toward the planet Mars when on September 5th Mars and the waning gibbous Moon will be less than 1o apart.
   
   
   

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Uranus is Backing Up

July 22nd to December 22nd :  Uranus at 30-day intervals   Well that’s a good to know!
   Saturday August 15nd the outer ringed planet Uranus appears to halt its regular eastward orbital motion and begins moving toward the west, in retrograde motion. Retrograde motion is an apparent motion to the west that any outer planet relative to the Earth appears to do whenever the faster moving Earth passes by. Sort of like passing a car on the highway. You know both vehicles are moving in the same direction but from your perspective it could appear that the other car is moving backward as you go by.
   Regardless, retrograde motion for the outer planets happens at regular intervals as the Earth pass each one. It is always more than a year and always a little further to the east when the retrograde motion begins each time. This is because the outer planet is also moving eastward.
   Mars, another outer planet, begins its retrograde motion next month.
   
   

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