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2011:  Jan  Feb  Mar  Apr  May  Jun 

 1.6.x & 1.4.1 LINKS

Throughout this website you will find pairs of links labeled "1.6.x" and "1.4.1".  Click here for a brief explanation.


CELESTIA's clock displays Coordinated Universal Time, UTC.  Click here for a brief explanation.


The eastern skies just before sunrise put on quite a show in early May, as four planets (Mercury, Venus, Mars and Jupiter) occupy the western part of Pisces.  Chasing Mars into Aries, both Mercury and Venus pass Jupiter on the 11th, an impressive double conjunction!

Note: in the 1.6.x and 1.4.1 links in this column below, planets east ("left") of the Sun are visible in your sky after sunset, while planets west ("right") of the Sun are visible before sunrise.

Run the links below as often as you like, and keep an eye on CELESTIA's clock near the top right corner of the program's window.  Don't forget that you can use your keyboard's   J  K   and   L   keys respectively to reverse, slow down and speed up time in CELESTIA.


Mercury seems to let Venus "cath up" with it in May, both appearing to pass Jupiter on the 11th, and then Mars about a week and a half later!  What a gathering!  (1.6.x)   (1.4.1)

SATURN: 2011 May

Slow-moving Saturn remains in retrograde motion in Virgo for the whole month of May, but is slowing by month's end  (1.6.x)   (1.4.1)

URANUS: 2011 May

Lagging behind in eastern Pisces, slow-moving Uranus remains west of the 4-planet "gathering" noted above  (1.6.x)   (1.4.1)

NEPTUNE: 2011 May

Slow-moving Neptune lingers in Aquarius, as the Sun, Mercury, Venus, Mars and Jupiter all leave the blue planet behind  (1.6.x)   (1.4.1)


The following will help you enjoy this page's many links that run events directly in CELESTIA.  If you're new to the program, these tips will also help you learn to use it.

You'll find more information about many of CELESTIA's controls on our  Learning Center  page.



Here are the Sun's positions along the Ecliptic at 00:00 UTC on the days shown.

The slightly curved lines above and below the Ecliptic show the extent of the Zodiac, which you may download from our  Bonuses  page and add to any version of CELESTIA.  Note that the curve in the Zodiac lines is the result of CELESTIA's rendering in perspective.

W A R N I N G !     It is never safe to look directly at the real Sun with the naked eye!  Moreover, looking at it through a telescope or binoculars—even for an instant—can cause permanent blindness!  NEVER DO IT!  Consult the professionals at your local planetarium or observatory to learn how you can safely "observe" the Sun and any SOLAR eclipse!

Of course, you can safely view CELESTIA's depiction of the Sun's apparent path in the sky in May.  Here are the links:  (1.6.x)   (1.4.1).  Note that versions 1.6.x and 1.4.1 differ in the way their "follow" and "lock" features work.  If you "follow" Earth and then "lock" the Sun to it, versions 1.6.x and 1.4.1 respectively maintain the "attitudes" of the Ecliptic and the the Celestial Equator.  This means that the Ecliptic remains "level" when you run the first link, but begins to tilt when you run the second!  Differences like this will be discussed on our  Help  page.


During your voyages in CELESTIA, would you like to be able to position yourself directly over the center of the half of Earth in sunlight or the half in darkness at any time this month?  On our  Tips  page, you'll find that it's quite easy to do so!  If you're any kind of sky watcher at all, you probably know just how helpful this can be!



In UTC per CELESTIA 1.6.x:
  New: May 3, 06:51.  1st Qtr: May 10, 20:33.
  Full: May 17, 11:09.  Last Qtr: May 24, 18:52.
(Celestia 1.4.1 usually indicates respective phase times within about one minute of those in version 1.6.x.)

NOTE: New, 1st Quarter, Full and Last Quarter Moons respectively are defined to occur when the Geocentric Ecliptic Longitudes of the Moon and the Sun differ by 0°, 90°, 180° and 270°.

To watch a short video demonstrating the Phases of the Moon,  click here.

The above diagram is produced with our "Moon Phases Calendar" script.  The numbers of the days of the month were added with an image-editing program.

To watch a short video of our Moon Phases Calendar in action,  click here.


Per CELESTIA 1.6.x:
    Perigee: May 15, 11:19 UTC; 362,140  km.
    Apogee: May 27, 9:57 UTC; 405,019  km.
(Celestia 1.4.1 usually indicates apogee and perigee times within about one minute of those in version 1.6.x.  Both versions of Celestia almost always indicate equal apogee distances and equal perigee distances.)

Note that this month's lunar perigee again occurs near the Full Moon, though not as close as last month.  The magnitude of the tides near mid-month should still be expected to be greater than usual.

Determined by our "Earth-Moon Distance" and "Moon's Apparent Path" scripts.  Note that distances given are those between Earth's and the Moon's centers. 

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Various astronomical "shadow events" occur throughout the Solar System!  This month's more interesting ones are featured here.


Here we highlight the most awe-inspiring eclipses taking place in our Solar System.  We also set them up so that all you need to do is click on their links.  Don't forget that you can generate lists of Earth's, Jupiter's, Saturn's, Uranus's, Neptune's and even Pluto's eclipses, using CELESTIA's own built-in "Eclipse Finder."  You'll find it in the program's menu under "Navigation".

Unless noted otherwise, the events identified below are displayed as if viewed from Earth, their magnifications shown in parentheses at the lower right of CELESTIA's window.  Events involving more than one moon are often cyclical, so usually only the first example is given, and then the period of the cycle.

Remember: you can press the   M   key to toggle Moon Labels on and off .


Jupiter is now in that part of its orbit where its equatorial plane, and the orbital planes of the four Galilean moons, are increasingly tilting with respect to the Sun.  While Io, Europa and Ganymede all produce solar eclipses each time they orbit Jupiter, this is not true of Callisto, whose increasingly tilting orbit has made it incapable of casting its shadow on Jupiter since last December.  It will not be able to cast its shadow on Jupiter again until 2013!

Five simultaneous solar eclipses (i.e. involving more than one major moon) occur on Jupiter this month, courtesy of Io and Europa.  Here are highlights of the 29 solar eclipses that Io, Europa and Ganymede spawn in May, as Jupiter's shadow now extends to the planet's west (right).

With the Galilean info below, it is easy to see why some events involving more than one moon repeat.  This info also lets you predict when events may recur.
   Io:  1.769 days
   Europa:  3.551 days
   Ganymede:  7.155 days
   Callisto:  16.69 days
   Io & Europa: 2 to 1
   Io & Ganymede: 4 to 1
   Europa & Ganymede: 2 to 1


Like Jupiter, Saturn is now in that part of its orbit where its equatorial plane, as well as the orbital planes of its major equatorial moons, are all tilting more and more relative to the Sun.  So fewer and shorter eclipses will occur on the ringed planet for some time.  Rhea, Titan and Iapetus have not been able to cast shadows on Saturn since Oct 2010, Feb 2010 and Jun 2007 respectively.  They will not cast their shadows on Saturn again until Mar 2024, Oct 2024 and July 2022 respectively.  In addition, last month Dione cast its last shadow on Saturn until Jul 2023.

While CELESTIA 1.6.x shows the shadows of Titan, Rhea, Iapetus, Dione and Tethys, version 1.4.1 displays only the shadows of Titan, Rhea & Iapetus.  So, 1.6.x and 1.4.1 respectively show 16 and no solar eclipses on Saturn in May.  In addition, version 1.6.x reveals no double simultaneous solar eclipses this month, as only Tethys produces a solar eclipse on Saturn now for a dozen years!  Moreover, Tethys is casting its shadow further and further south, and before long it too will not be able to produce a solar eclipse on Saturn for some time.

To aid in your viewing, here are the periods of Saturn's major moons.  These do not exhibit the resonances that Jupiter's Galileans display.  Still, you can use this info to predict subsequent eclipses of a single moon.
   Tethys:  1.888 days
   Dione:  2.737 days
   Rhea:  4.518 days
   Titan:  15.95 days
   Iapetus:  79.33 days


Neither Uranus nor Neptune will experience eclipses for decades.  Dwarf planet Pluto will experience no eclipses by Charon for about a century!

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News: 2011 May