Mercury at Superior Conjunction

mercury at superior conjunction
   Saturday February 17th the innermost planet Mercury reaches superior conjunction – on the opposite side of the Sun from the Earth. For those that are curious, Mercury at superior conjunction is approximately 1.384 AU (128,650,837 miles; 207,043,453 km) from the Earth – the combined distance of the Earth to Sun distance plus the radius of Mercury’s orbit.
   Mercury is not visible while in conjunction with the Sun but within the next week or so Mercury will reappear on the east side of the Sun and start becoming visible over the western horizon at sunset.

   
   
   

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 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.

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.

Mercury at Western Elongation

19jan-mercury-east-elongation
   On Monday January 1st Mercury, the innermost planet, will reach its orbital position known as greatest western elongation at 22.7o. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows. Even though it sounds confusing at western elongation for either Mercury or Venus the inner planet will be to the right of the Sun as we view them, meaning that at western elongation an inner planet rises in the east before the Sun rises. And at eastern elongation with the inner planet on the left side of the Sun the inner planet follows the Sun across the sky setting after the Sun sets.
orbital-positions
   From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – out to the left (east) from the Sun to eastern elongation, then reverse and move westward (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!


   Mercury is visible in the morning skies before sunrise along with Mars, Jupiter, and the stars Spica and Antares, as this graphic shows.

   
   
   
   
   

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 – Antares Conjunction

   Tuesday morning December 26th the innermost planet, Mercury, will be in a somewhat close conjunction with the heart of the Scorpius the Scorpion, the reddish star Antares. The two will be separated by about 8o and will be a bit too far apart to fit within the field of view of binoculars. Mercury has an apparent magnitude of -0.03 as compared with Antares 1.03 apparent magnitude.

   Looking higher above the horizon toward the south the planets Jupiter and Mars are visible as well as the blue-white star Spica in Virgo the Harvest Maiden. With a line-up of planets and Spica it is easy to visualize the ecliptic, the apparent path the Sun follows eastward throughout the year.
   
   
   

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.

Happy Holidays


   Have a safe, warm (or cool depending on your location), and happy holidays.
Animated graphic is set for 6:30 pm CST December 24th and 6:30 am CST December 25th

   
   
   

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.