Neptune at West Quadrature

orbital-positions   On Thursday June 2nd the position of the planet Neptune with respect to the Earth and the Sun places this ringed planet at what is called western quadrature. At that orbital position Neptune, and actually any outer planet, is at a 90 degree angle from us as this graphic shows. Think third quarter Moon as that is a fair comparison of the relative positions. At this position Neptune leads the Sun across the sky from east to west as the Earth is rotating, meaning that Neptune rises before the Sun and also sets before the Sun.

   Neptune currently is within the boundaries of the constellation Aquarius the Water Bearer. At around 7th magnitude Neptune is too dim to see with the naked-eye but easily seen with a telescope or binoculars. In 7×50 binoculars Neptune may be visible below the 4th magnitude Lambda Aquarii, and just below the point of a small triangle arrangement of 6th magnitude stars.

   This is a short video clip from a much longer video that I made as part of a live musical performance called “Orbit” at the Gottleib Planetarium in Kansas City Missouri during May 2011.

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

May Moon at 2nd Descending Node

30may-descending-node
   Monday May 30th our 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.
   
   

   On the day of the node crossing the 24-day old thin waning crescent Moon rises about 1 hour before sunrise local time.

   
   
   
   
   
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.

Mars Closest To Earth – This Time

   Monday May 30th the planet Mars will be at its closest to the Earth for this opposition at a distance of 0.50321 AU (75,279,144 km; 46,776,292 miles). Mars has an orbital shape that is more elliptical then the Earth’s orbital shape and like the Earth Mars has a perihelion and aphelion distance each orbit. Combine this with its roughly twice the Earth’s orbital period around the Sun and there is an interesting dynamic that happens about every 26 months when Mars reaches opposition. If Mars is at its respective perihelion, closest to the Sun, and is also near its opposition, and the Earth is near its aphelion, furthest from the Sun, then Mars will appear at a different apparent size relative to other oppositions.
   Mars is unmistakably bright during its opposition and perihelion. At an apparent magnitude of nearly -2.0 Mars outshines nearby Saturn (0.0), and its stellar doppelganger the reddish star Antares (1.0).

   
   
   

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

Our Moon Near Dwarf Planet Pluto


   Wednesday morning May 25th the 18.5-day old waning gibbous Moon will be about 3o from Dwarf Planet Pluto. Given that the Moon has an apparent magnitude of -18.5 not much else will be visible in the surrounding area of the sky, despite what my graphic shows.

   However a 2nd magnitude star, Albaldah (in Sagittarius), is about 0.5o from Pluto. If you can see that star then you are in effect looking at Pluto also, as this simulated 25mm eyepiece view is showing.

   
   
   
   
   

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

Mars at Opposition

Mars at Opposition
   Sunday May 22nd Mars will reach a point in its orbit around the Sun where it is at opposition relative to the Earth. at opposition The Earth is between the Sun and Mars, or any of the outer planets. At opposition both the Earth and the planet at opposition will have near identical heliocentric longitude. The opposition of Mars sometimes happens around the time that Mars is at its respective perihelion, closest to the Sun. If this happens during or near July when the Earth is at its respective aphelion, furthest from the Sun, then Mars will appear larger relative to when these dates are further apart. However Mars will never be as large as the full Moon, as explained in previous posts: “Mars Closest to Earth this Time”, or “Mars Madness” to read this one.
   The ‘Red Planet’ Mars has been in retrograde Motion since this past April, and will continue to retrograde until the end of June.
   Retrograde motion is the apparent backward, or westward motion that a planet will appear to make at a regular point in its revolution around the Sun.

We typically think of retrograde motion as being done by an outer planet from the Earth. This happens when the faster orbiting Earth catches up and passes by an outer planet. As this is happening the outer planet appears to slow down and then reverse its orbital direction toward the west. After a period of time (days to months) the outer planet again appears to slow down and then return to its regular eastward, or direct motion.
An inner planet orbit    However the two inner planets Mercury and Venus also undergo retrograde motion. Approximately one-half of their respective orbits is eastward as is with all the other planets. This then brings the inner planets to what is know as eastern elongation in the evening skies. The other half of the orbit for Mercury and Venus is toward the west as they move from eastern elongation through inferior conjunction toward western elongation in the morning skies.

   
   
   

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

Moon Passes Mars and Saturn

   This weekend the Moon will pass by the planets Mars and Saturn, both of which are located near the reddish star Antares in Scorpius the Scorpion. The Moon reaches its full phase on Saturday and while it is within a few degrees from Mars the planet Mars will be at opposition. The next evening, Sunday May 22nd the Moon, now at waning gibbous phase, will have moved further east and will be within a few degrees from Saturn.

   
   
   

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

Sun Not in Gemini

  According to the pseudoscience of astrology the Sun enters the constellation of the Gemini Twins on Friday May 20th. When in fact the actual position of the Sun on this date is still within the boundary of the constellation of Taurus the Bull, as this graphic and the banner graphic show.

   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 more observing information for this month.

May Moon at Apogee

18may-apogee_moon   Our Moon reaches apogee, (greatest distance from Earth), on Wednesday May 18th. At that time the Moon will more or less be at a distance of 31.82 Earth diameters (405,933 km or 252,235 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 13-day old waxing gibbous Moon rises a few hours before sunset local time and is near 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.

May Moon at Ascending Node

15may-ascending-node    On Sunday May 15th the 9-day old waxing 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 9-day old waxing gibbous Moon rises around a few hours before sunset local time and is a few degrees east from Jupiter.
   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?”

   
   
   
   
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 Jupiter


   Saturday May 14th the 8.3-day old waxing Gibbous Moon will be within a few degrees from the planet Jupiter in Leo the Lion.

   
   
   
   
   

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