Jupiter Has 2 More

   Outer planet Jupiter has probably more moons than have been counted so far. The greater majority of these satellites of Jupiter orbit in retrograde relative to the rotation direction of the planet. Satellites of any planet that orbit their ‘parent’ planet in retrograde are called irregular satellites to distinguish them from satellites that formed with the planet, and consequently would orbit in the same direction as the planet’s rotation.
   Two recently discovered satellites, bringing the known or at least suspected number to 69, are described via their respective URL with a very official looking but somewhat confusing at first glance bulletin. The links are to the MPEC (Minor Planet Electronic Circular) at the Minor Planet Center.
   Both of these satellites were discovered or co-discovered by Astronomers Scott Sheppard, David Tholen, and Chadwick Trujillo. Given the small size and challenges in imaging these satellites it is amazing that they were discovered. Read more about the discoveries at Sky & Telescope‘s web site.

    MPEC 2017-L47 : S/2017 J 1 click here
    MPEC 2017-L08 : S/2016 J 1 click here

       Take a tour around Jupiter and its many satellites. The sizes of the Galilean satellites, Io, Europa, Ganymede, and Callisto have been made larger than they would actually be given the size Jupiter used in the video.

       
       
       

    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.

ISS Followed the Arc

   Last evening, Sunday June 11th the ISS, International Space Station orbited over my part of the world. The ISS appeared about 45o above the west-northwest horizon and followed a path that went below the bowl of the Big Dipper and in a straight line ‘followed the arc to Arcturus’ in the constellation Bootes the Herdsman. At its peak the ISS reached nearly the zenith and at its brightest had to be at least -3.0 in apparent magnitude. After a several minutes the ISS moved out of sunlight and faded from view above the southeastern horizon.
Camera settings were 18mm; ISO 800; F4.0; 2 sec.
   One dependable and accurate source of viewing information for the ISS is at NASA’s ISS Sightings web site. Here you may learn the time and direction the ISS will appear, its duration of visibility, and its time and direction it will stop being visible.

   In a similar manner the Heavens Above web site will also provide viewing information for the ISS but in addition it will display a star map showing the path across the sky. This sample graphic shows the ISS path for June 12th.

   Want to see what the Earth looks like from the ISS? Click on this link to go to the ISS HD Earth Viewing web site for a view from one of several cameras mounted on the ISS as this screen capture shows. There are two additional maps that show the current position and orbital path of the ISS.
   
   
   

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.

Moon / Saturn Conjunction and Jupiter Pauses Briefly

   Friday June 9th one of the outer planets, Jupiter, becomes stationary in its retrograde westward orbital motion around the Sun. It will now begin moving in direct motion, its orbital direction around the Sun toward the east – as we view it from the Earth. Jupiter’s retrograde motion is something that occurs to varying amounts as the Earth passes by each outer planet.
   This animated graphic is set to show the motion of Jupiter from early May through the end of June. At the start the graphic shows where Jupiter is relative to the star Spica, and then it zooms in to make the retrograde loop for Jupiter easier to see.
   The Earth passing by an outer planet is a result of the Earth having a faster orbital speed, and as the angles between Earth and an outer planet change there is the appearance of the outer planet slowing down and stopping its regular eastward motion. Then for a time ranging from a week or so to several months the outer planet appears to be moving backward or toward the west. After a time the planet resumes its eastward motion.

   On Friday the 9th the just past full Moon, a 15-day old waning gibbous Moon, will be rising about an hour after local time for sunset. Between 2-3o to the right, or west, from the Moon is the planet Saturn 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.

June Moon at Apogee


   Our Moon reaches apogee, (greatest distance from Earth), on Thursday June 8th. At that time the Moon will more or less be at a distance of 31.85 Earth diameters (406,401 km or 252,526 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?”


   On the day of the apogee Moon the 14-day old full Moon rises around local time for sunset and is 9-10o degrees from the reddish star Antares in Scorpius the Scorpion.

   
   
   

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.

Neptune at Western Quadrature

orbital-positions   On Sunday June 4th 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.

click on graphic to see it larger   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 near 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.

   
   
   

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

Moon/Spica Conjunction


   Sunday evening June 4th the 10-day old waxing gibbous Moon will be within about 6o from the blue-white star Spica in the constellation Virgo the Harvest Maiden.

   
   
   

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/Moon Conjunction

   Saturday evening June 3rd the 9.3-day old waxing gibbous Moon will be within 1-2o from the giant planet Jupiter. Both will very comfortably fit within the field of view of binoculars. Both rise in the east (except on Venus) at about 3 pm CDT and will be over the southern horizon a couple of hours before midnight local time.

   
   
   

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.