January Waning Crescent Moon at Most Distant Apogee, and in Conjunction with Mercury and Saturn

   Our Moon reaches apogee, (greatest distance from Earth), on Monday January 15th. At that time the waning crescent Moon will more or less be at a distance of 31.86 Earth diameters (406,464 km or 252,587 miles) from the Earth. This is the greatest distance between the Earth and our Moon for this year. The next most distant apogee occurs during July when the full Moon will be at an apogee distance of 31.84 Earth diameters (406,223 km or 252,415 miles).

   On the day of the apogee the 28-day old and very thin waning crescent Moon rises between Mercury and Saturn. However only about 2% of the Moon’s disk will be showing and moonrise is only about one-half hour before sunrise so the Moon may be a challenge to see.

   Does our Moon actually go around the Earth as the 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?”

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

Moon-Jupiter-Mars Conjunction

   Thursday morning January 11th the 24-day old waning crescent Moon will be a few degrees away from the outer planets Jupiter and Mars. Also becoming visible over the eastern horizon are the planets Mercury and Saturn – as this graphic shows.

   The conjunction between the Moon, Jupiter, and Mars will be close enough so that all three will fit within the field of view of binoculars.

   
   
   
   
   
   
   
   
   
   
   

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.

Venus at Superior Conjunction


    On Tuesday January 9th the inner planet Venus will have moved into superior conjunction – on the opposite side of the Sun from the Earth. Venus will reappear on the east side of the Sun later next month and start becoming visible in the evening skies over the western horizon.

   
   
   

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.

Jupiter-Mars Close Conjunction

   If you were outside this morning you may have noticed over the southeastern horizon a bright star like object (Jupiter) just below a reddish star-like object (Mars). Both planets are moving eastward and Mars, as a faster orbiting planet, will gradually catch up and pass the planet Jupiter.
   Saturday and Sunday mornings January 6th-7th the planets Jupiter and Mars will be about 0.20′ (20 minutes) apart as Mars moves past Jupiter. With an apparent magnitude of -1.8 Jupiter far outshines Mars’s apparent magnitude of 1.40. This graphic is set for 7 am CST (12 UT) and the planets Mercury and Saturn are just above the eastern horizon. And further to the west higher over the southern horizon is the 20-day old waning gibbous Moon.
   This animated graphic is set to 1-day intervals starting with today, the 5th, and ending on the 7th. Both Mars and Jupiter are close enough to easily fit within the 25 mm eyepiece of a 6″ Reflector, and should make a great view with binoculars. I’m thinking that with the naked eye the two should almost merge into one, with Mars lost in the glare from Jupiter.

   
   
   

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.

January Moon at Ascending Node

   Thursday January 4th the 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.

   On Thursday January 4th the 17-day old waning gibbous Moon will be within the boundaries of Leo the Lion and about 11o west from the ‘Heart’ of the Lion, the star Regulus.
   While you are outside looking at the Moon turn toward the eastern horizon to see the planets Jupiter and Mars.
This animated graphic is set for 6 am CST (12 UT).

   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 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.

2018 Quadrantid Meteor Shower

   The annual Quadrantid Meteor Shower reaches its peak Wednesday morning January 3rd officially at 14:19 UT (9:14 am CST). The Quadrantids are one of the best meteor showers of the year but does not get much attention possibly because it’s winter in the northern hemisphere, and this area of the sky is not easily seen from south of the equator.
   The ZHR (average hourly rate) for this meteor shower ranges from 60 to several hundred. Best time for viewing is before sunrise as your part of the Earth is rotating toward the east sort of putting you headfirst into the meteor shower. To find the radiant for this meteor shower look for the stars of the Big Dipper and then look below the end stars in the handle.
click on graphic to see it larger
   Adding to the thrill of seeing a shooting star are the the planets Jupiter and Mars about 1o apart and closing in on a very close 0.2o separation on the 6th. Look closely and you may see Zubenelgenubi, one of the stars making up Libra the Scales. All three fit comfortably within the field of view of binoculars and contrast nicely in their respective apparent magnitudes (magnitudes shown on graphic).

Boötes the Herdsman

Boötes the Herdsman

   The radiant is the area from where the meteors seem to radiate outward from. Meteor showers owe their name to the constellation region the radiant is located within, and as this graphic shows the radiant is within the boundary of the constellation Boötes the Herdsman. So why the name Quadrantids?
   On some of the older star charts there is a now ‘extinct’ constellation called Quadrans Muralis, the Mural. This was a constellation located between Boötes and Draco the Dragon that was created in 1795 by French Astronomer Jérôme Lalande. It is a picture, or mural, of a Quadrant that had been used to map the stars. The Quadrantids Meteor Shower was named for the no longer used constellation.

   
   
   

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.

Earth at Perihelion – 2018

Earth at Perihelion   Feel the Heat?
   Wednesday January 3rd at 5:35 UT (11:35 pm CST Tuesday January 2nd), 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 this year, 2018, the Earth is 0.98333 AU (147,099,586 km; 91,403,445 miles) (compared with last year 2017: 0.98331 AU (147,101,082 km; 91,404,374 miles) from the Sun. Approximately one-half year or one-half revolution later, on July 6th, the Earth is at aphelion and is 1.0167 AU (94,508,169 miles; 152,096,155 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.

sun2014-ani   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.

   
   
   

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.