Sunday February 26th the new Moon will be crossing 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. The time for new Moon phase 14:59 UT while the time for the node crossing is 8 hours earlier at 6:40 UT. Given the close times for the two events means that there will be a solar eclipse. However the Moon, because of its elliptical shaped orbit, will be at a further distance from the Earth such that it will appear smaller in diameter than the Sun appears. This means that at mid-eclipse, or totality, the Moon will not completely cover the Sun, instead there will be a ring of sunlight around the Moon. The ring of sunlight is called the annulus and so this is an annular solar eclipse. The eclipse will be visible from parts of southern Argentina and western central Africa.
On my birthday in 1994 I was ‘honored’ to not only have an annular solar eclipse on that day but the eclipse path, the path of annularity, crossed right over where I live southeast of Kansas City Missouri. This animation is of the May 10th annular solar eclipse.
Thursday February 16th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Capricornus the Sea Goat and into the constellation of Aquarius the Water Bearer. 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, which will be Saturday February 18th when the sun is not in Pisces according to astrology.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.
Saturday January 7th the Dwarf Planet Pluto reaches a point in its orbit where it is on the opposite side of the Sun as viewed from Earth. This is known as solar conjunction.
Feel the Heat?
Wednesday January 4th at 14 UT (8 am CST), as the Earth continues its annual trek around the Sun, the Earth reaches a point in its orbit that is called perihelion. Perihelion is the minimum distance that separates the Earth from the Sun, and we are the closest to the Sun for the year at this point in the orbit. So the Earth, this year, is 0.98330 AU (147,101,082 km; 91,404,374 miles) (compared with last year 2016: 0.98331 AU (147,099,586 km; 91,403,445 miles) from the Sun. Approximately one-half year or one-half revolution later, on July 3rd, the Earth is at aphelion and is 1.01668 AU(94,506,310 miles; 152,093,163 km), its maximum distance from the Sun for 2017. This difference in distances is due to the shape of the Earth’s orbit being elliptical rather than circular. However the Earth has a mildly elliptically shaped orbit that is closer to being slightly out-of-round than the incorrect, very elliptical orbit that is often shown – like the illustration used here.
In Astronomy the shape of a planet’s orbit is called eccentricity, with 0 being a circle and 1 a straight line. Any value between 0 and 1 represents an ellipse. The shape of the Earth’s orbit is so close to being circular that the apparent size of the Sun does not appear to change as this animated graphic shows. The difference between perihelion and aphelion is about 3%.
Eccentricity for each planet is listed below for comparison.
Planet Eccentricity Mercury 0.2056 Venus 0.0068 Earth 0.0167 Mars 0.0934 Jupiter 0.0484 Saturn 0.0542 Uranus 0.0472 Neptune 0.0086 Pluto 0.2488
To read more about the Earth’s orbit and get some teaching ideas click here to download a PDF copy of my January 2011 Scope on the Skies column “Solar Explorations“.
Here is a good classroom activity about the Earth’s orbit and its effect on the apparent size of the Sun: Why Does the Size of the Sun Appear to Change? A Year of the Sun.
Comet 45P/Honda-Mrkos-Pajdušáková is a short period comet having an orbital path that takes it from beyond the orbit of Jupiter around the Sun approximately every 5.25 years. This current apparition has the comet starting to become brighter and more visible as it approaches its closest to the Earth on February 11th. On that date it will be visible in the morning skies before sunrise at a distance of 0.084 AU (7,808,288 miles; 12,566,221 km) from the Earth with an estimated apparent magnitude of 8.0.
Click here to read more and see some viewing graphics.
An important caveat about comet predictions:
“A comet is like a cat. Both have tails and both do what they want.”
According to the pseudoscience of astrology the Sun enters the constellation of Capricornus the Sea Goat on Wednesday December 21st at 10:44 UT (04:44 am CST, when in fact the actual position of the Sun is still within the boundaries of the constellation of Sagittarius the Archer.
In reality the Sun will have reached the celestial coordinates of 23.5o degrees south declination; 18 hours right ascension. With regard to the Earth’s surface this places the Sun over the Tropic of Capricorn, which is at 23.5o south latitude. We also know that it is the Earth’s tilt on its axis that is the cause for seasons on Earth rather than the distance between the Earth and the Sun. And of course we know that this signals the start of northern hemisphere winter and the southern hemisphere summer seasons.
And for those ‘insanely curious’ like me, while the Sun is at 23.5o South declination and ‘in’ Sagittarius the Earth is opposite at 23.5o North declination and at the feet of the Gemini Twins.
The animated graphic below sets the stage, so to speak, to illustrate the Sun’s actual location with respect to the zodiac constellations in the background. This is as opposed to the location of the Sun according to the pseudoscience of Astrology. The scene is set for 12:15 CST, or mid-day when the Sun is at an azimuth of 180o, or south, and is mid-way between rising and setting. Starting with the Sun at mid-day the scene changes as first the daytime sky is turned off, followed by the horizon being turned off.
This leaves a sky view like during a total solar eclipse except that the Sun is not blocked out by the new Moon. And like during that solar eclipse the zodiac constellations in the background become visible. Then the following are added starting first with Sagittarius, then Capricorn, and then the ecliptic and celestial equator are added to show the relationship between the two constellations and what makes them plus another 11 constellations the astronomical zodiac of 13 constellations. The animation ends with the addition of the constellation boundary lines and labels for the rest of the constellations in this setting.
It is the ecliptic, the apparent path of the Sun which, if it crosses the boundary of a constellation, makes that constellation one of the zodiac. And during December the Sun’s apparent path takes it across the constellation of Sagittarius rather than Capricorn.
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.