2019 March Equinox

   Wednesday March 20th is an equinox day. This means that for those in the northern hemisphere winter is ending and spring has ‘sprung’ (starts). For our counterparts south of the equator summer is ending and fall is beginning. From a geographical perspective we would describe the Sun as being over the Earth’s equator, and as this graphic shows there would be an equal amount of daylight and night on our planet as a result.
    At mid-day on the equator the sun is directly overhead and from that latitude you have no elongated shadow, just a ‘blob-like’ shadow at your feet as this picture of my feet taken at mid-day in Quito Ecuador shows.

    Regardless of your hemispheric preference get outside and cast a shadow!

  Northern hemisphere spring officially (well at least astronomically) begins at 22:01 UT on the 20th (5:01 pm CDT) when the Sun reaches the celestial coordinates of 0 hours and 0 degrees as it moves northward along the ecliptic crossing the celestial equator. At this location the Sun is just within the constellation of Pisces the Fishes and not entering Aries the Ram as the pseudoscience of astrology would have you believe.

    To learn more about the celestial coordinates click here to read a previous post about seasons and the equinox.

   Click here to see the online world sunlight map used to make the day/night graphic at the top of the page.


   Celebrate Solar Week March 18th-22nd. Click here to go to the Solar Week web site.

   
   
   
   During a trip to Quito Ecuador to visit one of the exchange student we had hosted, and her family, we spent the day at a Museum on the equator, Mitad del Mundo. I brought along my over-sized protractor knowing in advance that we would be at the museum. So at mid-day I had my wife stand on the equator (yellow line) and hold a string to the top of her head while Cathy, a sister of our exchange student, held the protractor. This was done during the summer so the Sun was over the northern horizon at mid-day and the Sun’s angle above the northern horizon was around 75o.

   Here is a short series of hourly pictures taken during the day on the September equinox on the equator in Quito Ecuador at Collegio Menor San Francisco de Quito, a private school that I visited and did the SunShIP project with (Sun Shadow Investigation Project).

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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.

Mercury at Inferior Conjunction

   Friday March 15th the innermost planet Mercury reaches inferior conjunction. At inferior conjunction Mercury will move between the Earth and the Sun – much like the position of the Moon at new phase. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.

   At this inferior conjunction Mercury will not be directly in line with the Earth and the Sun – on the ecliptic. Mercury has an orbital inclination of 7o with respect to the ecliptic. So like our Moon, Mercury during each complete orbit, will cross the plane of the ecliptic moving north (ascending node) and also moving south (descending node). For this inferior conjunction Mercury will be north of the ecliptic, but angling south approaching its descending node toward the end of the month.

   
   
   

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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Sun Enters Pisces – 2019

11 March 2014   Tuesday March 12th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Aquarius the Water Bearer and into the constellation of Pisces the Fishes. 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.


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Spring Forward!

   Sunday morning March 10th, in most of the United States of America, people will be setting their clocks one hour forward. This annual ‘event’ is often referred to by the phrase “Spring Forward”.
By setting clocks one hour forward it puts the U.S.A. on Daylight Saving Time. For you astronomical types, and you know who you are, I live at approximately    94oW, in the Central Time Zone. Using UT, Universal Time springing forward for me is a change from UT-6 to UT-5.
   
   You can learn a lot about time and calendars at the Time and Date web site.

   
   
   

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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Neptune and Vesta at Solar Conjunction

   Thursday March 7th the outer planet Neptune, and Asteroid Vesta reach a point in their respective orbit where they move behind the Sun as we view them from Earth. Neptune, or any of the other outer planets (Mars to Neptune), dwarf planets, or small solar system bodies beyond the Earth’s orbit, will all eventually reach this position on the opposite side of the Sun known as solar conjunction.
   For the two inner planets, Mercury and Venus, when they are at a similar position on the opposite side of the Sun, they are at superior conjunction.
   
   
   

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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March Moon at Apogee

   Our Moon reaches apogee, (greatest distance from Earth), on Monday March 4th. At that time the Moon will more or less be at a distance of 31.86 Earth diameters 252,520 miles (406,391 km) from the Earth.

   Does our Moon actually go around the Earth? 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*

   On the day of the apogee the 27.5-day old very thin waning crescent Moon will be over the southeastern horizon 30-60 minutes before sunrise local time.

*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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Mercury at Eastern Elongation

orbital-positions    On Tuesday February 26th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – from superior conjunction, behind the Sun, out to the left (east) from the Sun to eastern elongation, then reverse and move westward through (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!
   I’ve added Mercury’s orbit to the ‘horizon view’ graphic below. Mercury is never very far ‘out’ from the Sun at elongation because of how close to the Sun is Mercury.
   Currently Mercury is visible over the western horizon at sunset local time. Joining Mercury to the east (up to the left) is the planet Mars. A few degrees west from Mars, (to the right), is the star Hamal. This is the brightest star in the small constellation of Aries the Ram.
   Additionally, if your skies are dark enough it should be possible to see the “Square of Pegasus”, a part of the constellation Pegasus the Winged Horse. And look for the star Mirach, part of the constellation Andromeda the Princess. Just a few degrees to its right is a fuzzy looking smear of light – M-31, the Andromeda Galaxy.
   
   
   

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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