The Moon and a Dwarf Planet

   Monday morning April 22nd, before the Sun rises, look toward the south-southwest for the 17-day old waning gibbous Moon. While the Moon is obviously easy to see at a -12.60 apparent magnitude, the nearby, (2-3o), dwarf planet Ceres with an apparent magnitude of 6.90 is outshined by the Moon and is not visible.
   As this graphic shows all of the naked-eye visible planets except Mars are arranged from west to east above the horizon. While not naked eye visible Neptune, with an apparent magnitude of 7.94, is also shown. This arrangement of planets then offers an opportunity to visualize the plane of the ecliptic, the Earth’s orbit extended onto the sky. The plane of the ecliptic is one of the primary frames of reference for our solar system, and one of the things the other 7 planets have in common is that their respective orbits are all within about 7o from the plane of the ecliptic. Even our Moon stays within about 6o from the ecliptic.
   
   
   

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Sun Not in Taurus

April 19th  According to the pseudoscience of astrology the Sun enters the constellation of Taurus the Bull on Saturday April 20th. When in fact the actual position of the Sun on the 19th is within the boundary of the constellation of Aries the Ram, as this graphic shows. Actually the Sun had just entered Aries the day before on April 19th.

   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.


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Virgo, Spica, and the Moon

   Over the next several mornings, April 17th-19th, and before the Sun rises, watch for the Moon to move past the bright bluish-white star Spica in the constellation Virgo the Harvest Maiden. The Moon will be phasing from a 12-day old waxing gibbous Moon on the 17th to a full Moon on the 19th. A few days further on the Moon will be in its waning phases and passing by 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.


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Mars Gets Eyed by the Bull

   Monday evening April 15th the ‘Red Planet’ Mars will be near the open star cluster the Hyades – a v-shaped pattern of stars making up the face of Taurus the Bull. Mars will also be about 5o from the ‘eye’ of the Bull, the reddish star Aldebaran. Both the Hyades and Mars will easily fit within the field of view of 7×50 binoculars, and should prove to be an interesting sight. Compare the 1.50 apparent magnitude of Mars with the brighter 0.90 apparent magnitude for Aldebaran.

   
   
   

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.


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April Moon at Ascending Node and an Anniversary

   Friday April 12th the 7-day old waxing gibbous Moon will be crossing the plane of the ecliptic moving north relative to the ecliptic. This is known as the ascending 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 7-day old first quarter Moon rises around mid-day and sets the following day.

   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*

Happy Anniversary
   This year is the 75th anniversary for the NSTA (National Science Teachers Association), and this graphic helps to celebrate the event by highlighting Alphecca Gemma, the brightest star in the constellation Corona Borealis, the Northern Crown. This star is 75 light years distant and so the light you see coming from that star left Alphecca Gemma the year that NSTA started.
   The date of April 12th was chosen because during this week Science Teachers and other educators will gather in St. Louis, MO for our annual conference. See you there?

*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 return to bobs-spaces.


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Moon – Venus, Mercury, Neptune – Triple Conjunction

   Tuesday April 2nd the 27-day old thin waning crescent Moon will join three planets, Mercury, Venus, and Neptune in a triple conjunction. All four will be grouped within an area about 8-10o across. This separation is slightly more than the field of view of 7×50 binoculars.
   The group of planets and our Moon have an interesting range of apparent magnitudes. The waning crescent Moon is -9.8, Venus -3.9, Mercury 0.82, and Neptune 7.95.

   
   
   

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.


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Planets Line Up in the Morning Skies

   Starting Monday April 1st, and continuing for a couple of weeks there will be an arrangement of 5 planets over the eastern to southern horizon in the hour or so before the Sun rises. Of these Neptune is the only one not bright enough to be visible to the unaided eye.

The Planets at 10-day Intervals During April
   The basic organization of our solar system is to have the other 7 planets follow orbits close to the plane of the ecliptic, and given how these planets are arranged and appear from the Earth this month makes it easy to visualize the ecliptic. This ‘view from above’ animated graphic shows the planets at 1-day intervals during April.

   
   
   

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.


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