Mercury at Eastern Elongation

orbital-positions    On Friday November 24th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – from superior conjunction, behind the Sun, out to the left (east) from the Sun to eastern elongation, then reverse and move westward through (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!

   Currently Mercury is visible over the south to southwestern horizon at sunset shining with an apparent magnitude of -0.27. About 3o above Mercury is the planet Saturn with an apparent magnitude of 0.50.

   
   
   
   
   

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 East Elongation

orbital-positions    On Sunday December 11th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   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.
click on animated graphic to see it larger    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!
   This animated graphic shows Mercury at its eastern elongation and its orbital path. The horizon is removed in one graphic so Mercury’s orbit around the Sun could be visualized better.

   
   
   
   

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 Eastern Elongation

orbital-positions    On Monday April 18th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   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!
   In less than a month, on May 9th, Mercury will move into inferior conjunction as it crosses the ecliptic moving south setting up a transit by Mercury across the Sun.


   Currently Mercury is very visible shining at nearly 0 magnitude over the western horizon at sunset.

   
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Mercury at East Elongation

orbital-positions   Tuesday December 29th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective Mercury, and Venus for that matter, appear to move out to the left (east) from the Sun for a period, then reverse and move westward between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
   Mercury is currently visible as an ‘evening star’ over the western horizon at sunset. Further to the east and higher above the horizon is the dwarf planet Ceres and the outermost planet Neptune. Both are dim and are just beyond the light grasp of the naked eye but could be seen through binoculars as a star-like point of light.
ceres-ani
   If your viewing is done with a telescope then keep a close eye, or eyepiece, on Ceres as over a several day period, December 29th to January 2nd Ceres will be moving past M-30, a globular star cluster (fuzzy blur on left edge of field of view). This is a simulated view through a 25mm eyepiece on an 8″ Reflector.

   
   
   
   
   
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.

Venus at its Brightest

   Have you noticed that bright shining ‘star’ in the morning skies? At this time of the year you could be thinking I am referring to Sirius, the brightest night time star. While Sirius, no kidding, has an apparent magnitude of -1.4 it is out shined by the inner planet Venus now rising about 2-3 hours before sunrise local time. Venus currently has an apparent magnitude of -4.54 and coincidentally Venus is at its greatest brilliance.

Venus monthly: January-December 2015

Venus monthly: January-December 2015

   This is not the first time that Venus has been at its greatest brightness as this point in Venus’s orbit occurs as a function of the planet’s orbital position relative to the Earth and the Sun. Venus increases in its apparent size as it moves from superior conjunction, behind the Sun through eastern elongation to inferior conjunction. During this time Venus goes through phase changes starting with a waning gibbous phase following superior conjunction to a new phase at inferior conjunction. At this point Venus is at its greatest apparent size however we will not see Venus until it moves away from inferior conjunction. As Venus moves toward western elongation and then to superior conjunction its apparent size decreases while it goes from a large crescent shape to a smaller waxing gibbous phase.
   Venus was at inferior conjunction this past August 15th so it was last at its greatest brightest on July 12th when it was a large but thin waning crescent shape. Now Venus is moving past inferior conjunction and is at a orbital position similar to the one it had in July making Venus appear at its greatest brightness.

   
   
   
   

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 at East Elongation

orbital-positions   Friday September 4th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective Mercury, and Venus for that matter, appear to move out to the left (east) from the Sun for a period, then reverse and move westward between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
   Mercury is currently visible as an ‘evening star’ over the western horizon at sunset. Saturn is also visible over the southern horizon west of Antares. Not bright enough to be visible are two of the dwarf planets in our solar system, Makemake and Haumea.

   
   
   
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.

Venus at Eastern Elongation

inner-planets-positions   Saturday June 6th Venus reaches the point in its orbit called greatest eastern elongation. As this graphic shows an inner planet, Venus or Mercury, is more or less at a right angle (90o) from the Sun and Earth at eastern elongation. From the surface of the Earth, your backyard, for example, Venus is to the left, or eastern side of the Sun and is setting after the Sun.

   At eastern elongation the angle between Venus and the Sun is at its greatest, which for this elongation Venus will be 45.4o from the Sun. In terms of viewing Venus, this is as about as late as Venus will set, about 4 hours after sunset local time, meaning for some Venus may set close to midnight local time. This animated graphic shows Venus at sunset on June 6th, and then with Venus’s orbit shown, and then with the horizon removed to see where the Sun is relative to Venus.

venus at eastern elongation   From eastern elongation forward Venus will be moving westward toward the Sun, and each day setting closer and closer to the time of sunset. By September Venus will have orbited to inferior conjunction – between the Earth and the Sun. During this part of the inner planet orbit, from eastern elongation to inferior conjunction, the distance from Earth decreases and the apparent size of Venus increases. Venus also goes through phase changes much like our Moon, and so from eastern elongation to inferior conjunction Venus wanes from a small appearing gibbous phase to an increasingly thinner crescent phase.
   
   
   
   

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.