Moon Slides Down Ecliptic

   Over the next several mornings the Moon in its waning phases will appear to slide down the ecliptic, passing several planets along the way. These graphics show the Moon and the morning planets from January 30th through February 6th and are set for 6:30 am CST.

   
   
   
   

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.

January Moon at Apogee #2

30jan-apogee-moon   For the second time this month our Moon reaches apogee, (greatest distance from Earth), this time on Friday January 30th. At that time the Moon will more or less be at a distance of 31.7 Earth diameters (404,533 km or 251,365 miles) from the Earth.
   Does our Moon actually go around the Earth as this graphic shows? 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 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?”

   
   The 21-day old waning gibbous Moon rises before midnight local time and is close to the blue-white star Spica in Virgo the Maiden.

   
   
   

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.

Clear Skies = 6 Planets

   Finally had some warmer weather although still below freezing at least there was no wind like yesterday morning. This arrangement of the planets and the Moon makes it easy to visualize the ecliptic and the relationship that the planets, our Moon, and the sun have with this ‘reference line’.
Here are are a couple of pictures of the six visible planets taken from one of my morning viewing locations. Definitely not for dark sikes!
Picture specifications: 18 mm; 2.5 sec.; f9; ISO 400

 

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.

January Moon at Ascending Node

jan27-ascending-node    On Wednesday January 27th the 18-day old waning 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.
   The waning gibbous Moon rises around 11 pm local time and the evening of the 27th the Moon will near the planet Jupiter.
moon-orbit   Does our Moon actually go around the Earth as most graphics, like this one, 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 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?”

   
   
   
   
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.

Mercury Moves Forward

   Monday January 25th the innermost planet Mercury ends its retrograde motion and resumes its eastward or direct motion as it orbits the Sun.
mercury-orbit   All planets revolve around the Sun in the same direction which as we view from the Earth is toward the east. Planets have orbits that are tilted or inclined from nearly parallel with the Earth’s orbit (plane of the ecliptic), to about 7o above or below. This is known as inclination. Since the orbits are inclined from the Earth’s orbit there will be a highest and lowest separation or distance above and below the Earth’s orbit. There will be two places, (nodes), where the planet orbit intersects or crosses the Earth’s orbit. One is going down, (the descending node), and the opposite going up, (the ascending node). I post regularly during each month about our Moon’s node crossings.
mars-retrograde-ani   In addition when the Earth’s orbital speed is compared to an outer planet there will be a time period when the faster moving Earth passes the outer planet. This sets up a temporary illusion where it appears as if the outer planet has reversed direction and is now moving backward toward the west, or in retrograde motion.
   On the other hand the two inner planets, Mercury and Venus, also revolve around the sun toward the east and go through a period of retrograde motion. However theirs is not as a result of the Earth’s faster orbital speed but rather it is their faster orbital speed compared with the Earth’s that gives them their retrograde motion. And unlike the apparent retrograde motion for an outer planet, Mercury and Venus do actually move in retrograde motion as this animated graphic is showing.
   The size for Mercury is exaggerated and the animation is set to a 1-day interval. It is showing Mercury moving westward as venus is moving eastward. As Mercury moves along its orbit it eventually curves around and starts moving toward the east. This may be close to the day when Mercury reaches its furthest separation from the Sun on the west or right side of the Sun. That point is known as Greatest Western Elongation and is on February 7th. The counterpoint to this is when Mercury, or Venus, reaches their respective Greatest Eastern Elongation on the left or east side of the Sun.

   
   
   
   

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.

Planets Align, Well Sort of

planets   In the news recently and on social media there has been a lot of ‘noise’ about a spectacular alignment of the five visible planets. This is one example of many graphics that show the planets aligned in a straight line out from the Sun or the Earth. That is somewhat misleading as the planets would very rarely if ever be arranged in a straight line outward from either the Sun or the Earth. So when you hear or see about this planetary alignment go out in the morning, if possible, and see how the planets are aligned. Not in a straight line as this graphic suggests but rather they are spread across your sky.
   Below are two graphics that hopefully will clarify how the planets are positioned in space relative to the Earth. The graphic on the left shows the sky at around sunrise local time with the visible planets spread out or aligned across the sky from east to west. The green line represents the Earth’s orbit but from our perspective on Earth it is the Sun’s apparent path, the ecliptic. It is also known as the plane of the ecliptic, and is a reference ‘line’ for the the orbits of the other planets. The planets all revolve around the Sun toward the east and each of the other 7 planets have orbital paths that are close to being parallel with the Earth’s orbit, or plane of the ecliptic. Their respective angle away from the plane of the ecliptic, is known as inclination, and none of these planets are inclined more than about 7from the ecliptic.
   The picture on the right shows the planets at the same time but looking down on the solar system. The white line on the Earth is the horizon and the arrows radiate outward from a center point toward each planet just like they do in the picture on the left. That center point represents where an observer would be at their time of sunrise.

   
   
   
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.

The Sun, Here not There

view-from-earth-not-in-aquarius   Wednesday January 20th the Sun, in its apparent eastward motion along the ecliptic, moves out of the constellation Sagittarius the Archer and into the constellation of Capricorn the Sea Goat. 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.
   A few hours after the Sun crosses into Capricorn, and according to the pseudoscience of astrology, the Sun enters the constellation of Aquarius the Water Bearer. When in fact, as written above, the actual position of the Sun is still within the boundary of the constellation of Capricorn the Sea Goat.
   
   
   

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.

Moon Near Aldebaran


   Tuesday evening January 19th the 10-day old waxing gibbous Moon will pass within about 1o from the reddish star Aldebaran in Taurus the Bull. Aldebaran is the brightest of the stars in Taurus, and is one of the end stars in the v-shaped open star cluster known as the Hyades.
   For some parts of the world the Moon will occult or pass in front of Aldebaran. jan19-binoHowever from my location the Moon will be right around 1o from Aldebaran, making at the least for interesting binocular viewing, or photographing. Unfortunately my weather forecast for Tuesday evening includes several inches of snow.
   The Moon rises around 2 pm local time and is well above the horizon by the time it gets dark.

   
   
   
   

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.

Mercury North of the Ecliptic

mercury-orbit   Monday January 18th the innermost planet Mercury will reach its greatest angle above the ecliptic at 7o North. The plane of the ecliptic, or the Earth’s orbital path around the Sun, is the reference ‘line’ for measuring each planet’s respective orbital path angle from. This is known as inclination and Earth’s has an inclination of 0o while Mercury has an inclination of 7o.
   Mercury was recently at inferior conjunction, between the Earth and Sun (like a new Moon phase) but due to the 7o inclination for Mercury’s orbit it was not directly between the Earth and Sun on the ecliptic. This inclination of Mercury’s orbit, like the Moon’s 6o inclination from the Ecliptic, means that not every new Moon or inferior conjunction of Mercury results in either a solar eclipse or a Mercury transit.
   As Mercury and the Earth continue revolving around the Sun the angular difference between the two orbits will change as Mercury’s orbit criss crosses the ecliptic in its regular pattern of ascending and descending nodes. Keep track of these as on May 9th, at descending node, Mercury will transit, cross the disk of the Sun in a Mercury transit.

   
   
   
   

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.

January Perigee Moon

jan15-perigee-moon   The Moon reaches perigee, (minimum distance from Earth), this month on Friday January 15th. At that time the Moon will more or less be at a distance of 28.9 Earth diameters (369,619 km or 229,670 miles) from the Earth.
   Does our Moon actually go around the Earth as this graphic shows? 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 on graphic to see it larger
   
   
   The 6-day old waxing crescent Moon is very visible over the southwest horizon a couple of hours before sunset 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?”

   
   
   
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.