Neptune at Eastern Quadrature

   Sunday November 29th the position of the planet Neptune with respect to the Earth and the Sun places this ringed planet at what is called eastern quadrature. Neptune is at a 90 degree angle from the Earth – think first quarter Moon as that is a fair comparison of the relative positions. At this position Neptune follows the Sun across the sky from east to west as the Earth is rotating, meaning that Neptune rises after the Sun and sets after the Sun.

   Where is Neptune now? The 8th planet from the Sun is currently within the constellation of Aquarius the Water Bearer and has recently completed its retrograde motion (November 18th).

   
   
   
   This is a 1 minute clip from a video I made showing Neptune and some of its moons as viewed from the Voyager 2 spacecraft. This clip is from a longer video of a tour of the solar system and was part of a live musical performance called “Orbit”. The performances were done in May 2011 at the Gottleib Planetarium in Science City at Union Station in Kansas City MO.

   
   
   
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.

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Jupiter at 15 Day Intervals

Jupiter at 15 Day Intervals (8 November – 8 May)

   A Backwards Jupiter, or when the giant planet starts retrograde motion. Tuesday December 9th the largest planet in our solar system, Jupiter, begins its retrograde motion. Retrograde motion is an apparent motion that the outer planets, relative to the Earth, have. It is an apparent motion that looks as if the outer planet stops it normal direct motion to the east and reverses direction to the west. After a period of time the apparent westward motion ends and the planet resumes its normal orbital path to the east. Retrograde motion happens as the faster moving Earth catches up with and then passes by the outer planet. It is during this time that the backward apparent motion happens.
   The two inner planets also have retrograde motion but it is a result of their orbit around the Sun and not the Earth passing them by. For approximately one-half of their orbit they move east, from western elongation through superior conjunction to eastern elongation. Then at eastern elongation the inner planet starts moving westward through inferior conjunction to western elongation.
   Read a little more about retrograde motion in my February 2012 Scope on the Skies column, drawkcab planets, in Science Scope Magazine.
Click on graphic to see it full size.

Click on graphic to see it full size.

   Where is Jupiter now? Jupiter is a few degrees west from the star Regulus in Leo the Lion. Jupiter rises around midnight local and is visible above the horizon the remainder of the night.

   
   
   
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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.

Uranus at Opposition

view-from-uranus   Tuesday October 7th the outer planet Uranus reaches a position in its orbit around the Sun when it is on the oppisite 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 the object 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.

   
   
   
[centup]
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.

Mars Madness?

   This year, during August, Mars will be at its closest to the Earth; so close, in fact, that it will appear as large as the full Moon.
   Have you heard this urban legend before? According to some tomorrow, the 27th, it will happen again. For the record the full Moon was the 21st, not that the Moon needs to be visible for this non-event. Consider that since 2003, emails describing this urban myth have circulated the internet usually during July or August. It all started during the opposition of August 2003 when Mars was about as close as it can be to the Earth (55,755,723 km [34,645,000 mi.]) in a 20-year cycle of varying distances at opposition. Since then, usually around August, misinformation about the appearance of Mars circulates around the internet.

Mars and Earth 3 March 2012 and 27 august 2013

Mars and Earth 3 March 2012 and 27 august 2013

   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. In the time that it takes the Earth to catch up with and move into an opposition position, the outer planets have also been moving eastward relative to the stars in the background. Over time, the constellation where the outer planet is located during opposition and its retrograde loop gradually shift to the east. An opposition is also near the time when the distance between the Earth and an outer planet is around the minimum distance. Keep in mind that because the shape of the orbit is elliptical, this minimum distance will be different each time.
Click on image to see full size

Click on image to see full size

   Since opposition for Mars was March last year (2012) and not during August as it was during August 2003, this should help dispel this particular urban myth that has appeared every July or August since that August 2003 opposition. However, there is an even more conclusive way to show that Mars could never be so close that it would appear as large as the Moon. To see how use the information in the data table and the math formulas below. You will see that Mars could not appear to be as large as our Moon unless some force somehow caused Mars to change its orbital position and literally move closer to Earth.
   On March 5, 2012, Mars was 100,781,093 km (62,622,472 mi.) from Earth. Mars is 6,792 km (4,220 mi.) in diameter. The Moon is 3,475 km (2,159 mi.) in diameter and is an average 384,400 km (238,900 mi.) from Earth. To calculate other dates, use other distance (km) values from the data table and the math formulas:

To calculate how large Mars will appear as compared to the Moon:

(Mars’s diameter ÷ Mars’s distance) ÷ (Moon’s diameter ÷ Moon’s distance)

To calculate how close Mars would have to be to appear as large as the full Moon:

(Mars’s diameter × Moon’s diameter) × Moon’s distance

   
   
   Click here to go to the Qué tal in the Current Skies web site for more observing information.

Eta Aquarid Meteor Shower

radiant   This weekend the Eta Aquarids Meteor Shower reaches its peak during the early morning hours before sunrise on Monday 6 May, however like all annual meteor showers there is a range of days, (19 April through 28 May), where meteors associated with the Eta Aquarids may be seen. This meteor shower radiates outward from the constellation Aquarius the Water Bearer; averages 55 per hour; are fast moving often leaving a glowing train that may lasts for several seconds. A ‘train’ is a persistent glowing streak of light left behind by the meteor as it vaporizes in the upper atmosphere. Interestingly the Eta Aquarids originate from debris left along the Earth’s orbit by Halley’s Comet.

   This region of the sky unfortunately rises only a couple of hours before sunrise and on the mornings of the 5th and 6th the waning crescent Moon will be above the eastern horizon. The slides below show the region of the sky set to 4:30 a.m. CDT on May 6th (2330 UT 5 May). Each slide depicts the constellations with and without the connecting lines forming the constellation pattern. I used several including the classical Astronomical patterns, and those by H.A. Rey in his book The Stars, A New Way To See Them. (You may know H.A. Rey as the author of Curious George)

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   Click here to go to the Qué tal in the Current Skies web site for more observing information.

Stairway to the Horizon-Part 3

January 5th to 10th  - 7 a.m. Local Time

January 5th to 10th – 7 a.m. Local Time

   This month, as in the previous few months at sunrise, you will be finding the Moon in its late waning phases passing by bright stars (Spica and Antares) and planets (Saturn and Venus) that are located near the ecliptic path. This occurs as the Moon moves eastward along its orbital path toward new Moon phase on the 11th. This animated graphic shows the sunrise skies at the same time each morning starting with tomorrow the 5th, and stepping one day at a time ending on the 10th with a very thin waning crescent Moon near Venus. (Click on the image to see it full size)
   You may have noticed that there is more going on in this animated image then just the Moon moving past the stars and planets. The stars are moving toward the right, westward a little bit (about 1 degree) each day due to Earth revolution around the Sun. Additionally watch Venus as it moves eastward and appears a little lower above the horizon each day. This is due to the orbital motion of Venus carrying it eastward toward superior conjunction, ‘behind’ the Sun as we would view it from Earth.

   
   
   
Click here to go to the Qué tal in the Current Skies web site for more observing information.

Uranus at East Quadrature

Uranus at East Quadrature

Uranus at East Quadrature


   Ok- as having once taught middle school grades 6 through 8 I have always enjoyed this part of the lessons about the solar system. That is, when I can explain to students about a debate over the pronunciation of this particular planet. Of course saying ‘Your Uh Nuss’ is not as humorous as the kids preferred ‘Your Anus’! I like to describe this debate (with tongue in cheek), that there are two sides to the pronunciation debate – sort of split down the middle if you will. Eventually we get to the planet and its characteristics. Eventually.
Uranus in the Evening Sky

Uranus in the Evening Sky

   So what about this East Quadrature? This is a position of an outer planet with respect to the location of the Earth and the Sun. Outer planets at eastern quadrature are located at a 90o angle from the Earth and the Sun as shown in the first graphic above. This is one of the three positions that are used to describe an outer planet location during the Earth’s orbit around the Sun — not the outer planet’s orbit. An outer planet will be at eastern quadrature, then approximately 3 months later at opposition (Uranus-Earth-Sun), 3 months later at western quadrature, 3 months later at superior conjunction (Earth-Sun-Uranus), then the pattern repeats.
Uranus in Motion

Uranus in Motion

   So where exactly is Uranus (the correct answer is not behind you!!)? This outer planet currently rises before sunset local time and is over the southern horizon as shown in the second graphic above. It is too dim to be seen with the naked eye, or at least right at the fringes of what we can see – so if your skies are really dark then you may be able to discern the faint glow of reflected sunlight from Uranus.
   With binoculars it will become, in a sense, one of the stars in your binocular field of view. In this simulated 7×50 binocular view Uranus is slightly brighter that the 6th magnitude stars nearby. To verify that you are actually viewing Uranus use this animated graphic as a star field guide. Wait a couple of weeks to allow the slower moving planet to move in its orbit. Then observe this same area to see if there have been any changes. This graphic starts with the Uranus near a pair of equal in brightness stars on 26 November. The graphic dissolves into showing the position of Neptune today, and then dissolves one last time to show where Uranus is with respect to the pair of stars.

   Here is a couple minute long clip from a video I produced that was used during a live music performance by the group Dark Matter under a 60-foot diameter planetarium dome.

   
   
   
Click here to go to the Qué tal in the Current Skies web site for more observing information.