Saturday March 20th is an equinox day. While typically called the Vernal or Spring Equinox it is more globally appropriate to call this day the March Equinox as it is the start of Fall in the Southern Hemisphere. The official time for the equinox is 09:40 UT on the 20th which for my time zone is 5:40 am CDT. So for those in the northern hemisphere winter is ending and spring has ‘sprung’ (starts). 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.
Northern hemisphere spring, Astronomically speaking, is 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 22nd-26th. 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).
Friday evening March 19th look for the 6.7-day old waxing crescent Moon to be about 3o from the ‘Red Planet’ Mars, and about 5-6o from the reddish star Aldebaran in Taurus the Bull. All three should just barely fit within the field of view of 7×50 binoculars.
Thursday March 11th 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.
Friday March 5th the 22-day old last quarter Moon crosses the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.
On the date of the descending node the 22-day old last quarter Moon will be over the southern horizon at sunrise local time, and about 3-4o from the reddish star Antares in Scorpius the Scorpion.
Over the next few evenings the waxing gibbous Moon will move eastward passing by the open star cluster known as the Beehive Cluster this evening and then in a couple of days, as a full Moon, will be close to the heart of Leo the Lion the star Regulus.
While the Moon may be close to the open star cluster the waxing gibbous Moon with its considerably greater apparent magnitude will outshine the star cluster making it not visible. Wait a few days and then aim your binoculars or low power eyepiece for a better view.
Tuesday evening February 23rd the 12-day old waxing gibbous Moon will be about 2o from Pollux, one of the two ‘Twin’ stars of the constellation Gemini the Twins. The other brother is Castor, which is about 6o away from the Moon.
Saturday February 20th the 9-day old waxing gibbous Moon will be crossing the plane of the ecliptic moving north. 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 9-day old waxing gibbous Moon will be over the southwestern horizon later during the evening after sunset local time. Watch for the Moon to be about 8o from the reddish star Aldebaran in the open star cluster the Hyades in Taurus the Bull.
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 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.
Saturday morning February 20th in the hour or so before the Sun rises look for the innermost planet Mercury to be about 4-5o from Saturn and Jupiter. All three should fit within the field of view of binoculars, but the three planets will be low above the horizon.
According to the pseudoscience of astrology the Sun enters the constellation of Pisces the Fishes on Thursday February 18th. In fact the actual position of the Sun is still within the boundary of the constellation of Aquarius the Water Bearer, as this graphic shows. The Sun had just entered Aquarius 2 days ago.