Moon in 2015

Moon Phases Mosaic

A mosaic made from 9 individual photos of the Moon captures its phases over one synodic month. For complete details about this image, see Moon Phases Mosaic. The individual images included in this composite can be found in the Moon Phases Gallery. For more composites, see Moon Phases Mosaics. Photo copyright 2012 by Fred Espenak.

As the Moon orbits Earth, its changing geometry with respect to the Sun produces the Moon’s characteristic phases (New Moon, First Quarter, Full Moon and Last Quarter). One orbit of the Moon relative to the Sun (the synodic month) has a mean duration of 29.53 days.

                    Moon Phases for 2015 (GMT)

   New Moon       First Quarter       Full Moon        Last Quarter
-------------     -------------     -------------     -------------   
                                    Jan  5  04:53     Jan 13  09:47    
Jan 20  13:14     Jan 27  04:48     Feb  3  23:09     Feb 12  03:50    
Feb 18  23:47     Feb 25  17:14     Mar  5  18:06     Mar 13  17:48    
Mar 20  09:36 T   Mar 27  07:43     Apr  4  12:06 t   Apr 12  03:44    
Apr 18  18:57     Apr 25  23:55     May  4  03:42     May 11  10:36    
May 18  04:13     May 25  17:19     Jun  2  16:19     Jun  9  15:42    
Jun 16  14:05     Jun 24  11:03     Jul  2  02:20     Jul  8  20:24    
Jul 16  01:24     Jul 24  04:04     Jul 31  10:43     Aug  7  02:03    
Aug 14  14:54     Aug 22  19:31     Aug 29  18:35     Sep  5  09:54    
Sep 13  06:41 P   Sep 21  08:59     Sep 28  02:50 t   Oct  4  21:06    
Oct 13  00:06     Oct 20  20:31     Oct 27  12:05     Nov  3  12:24    
Nov 11  17:47     Nov 19  06:27     Nov 25  22:44     Dec  3  07:40    
Dec 11  10:29     Dec 18  15:14     Dec 25  11:11                      

The table above lists the date and time of the Moon’s phases throughout 2015. The time of each phase is given in Greenwich Mean Time or GMT (a.k.a. Universal Time or UT). I’ve generated a table of the Moon’s phases covering 100 years at Moon’s Phases – 21st Century (GMT). Similar 100-year tables for other time zones include Eastern Standard Time (EST), Central Standard Time (CST), Mountain Standard Time (MST), and Pacific Standard Time (PST). To convert GMT to other time zones, visit Time Zones.

What surprises many people is that the length of the synodic month can vary by over 6 hours from its mean value of 29.5306 days (29 days 12 hours 44 minutes). The table below gives the date of New Moon, the length of the synodic month, and the difference from the synodic month’s mean value for every synodic month in 2015. For instance, the fourth synodic month of 2015 (beginning Apr 18) is 3 hours 28 minutes shorter than the mean while the tenth month (beginning Oct 13) is 4 hours 57 minutes longer than the mean.

              Synodic Months for 2015 

   Date/Time of          Length of        Dif. from
  New Moon (GMT)       Synodic Month      Mean Month 
------------------     -------------     -----------
2015 Jan 20  13:14      29d 10h 34m       -02h 10m
2015 Feb 18  23:47      29d 09h 49m       -02h 55m
2015 Mar 20  09:36      29d 09h 21m       -03h 23m
2015 Apr 18  18:57      29d 09h 16m       -03h 28m     shortest
2015 May 18  04:13      29d 09h 52m       -02h 52m
2015 Jun 16  14:05      29d 11h 19m       -01h 25m
2015 Jul 16  01:24      29d 13h 29m       +00h 45m
2015 Aug 14  14:53      29d 15h 48m       +03h 04m
2015 Sep 13  06:41      29d 17h 24m       +04h 40m
2015 Oct 13  00:06      29d 17h 41m       +04h 57m     longest
2015 Nov 11  17:47      29d 16h 42m       +03h 58m      
2015 Dec 11  10:29      29d 15h 01m       +02h 17m   

The year 2008 had even greater extremes in the synodic month – from 5 hours 48 minutes shorter, to 6 hours 49 minutes longer than the mean value. So what causes these variations? The explanation lies in the fact that the Moon’s orbit is elliptical. If New Moon occurs when the Moon is nearest to Earth (perigee), then the synodic month is shorter than normal. On the other hand, if New Moon occurs when the Moon is farthest from Earth (apogee), then the synodic month is longer than normal. Furthermore, the orientation of the Moon’s ellipse-shaped orbit slowly rotates in space with a period of about 18 years. A more detailed discussion on this topic can be found at Moon’s Orbit and the Synodic Month. You can also find the duration of every synodic month this century at Length of the Synodic Month: 2001 to 2100.

Because the Moon orbits Earth in ~29.5 days with respect to the Sun, its daily motion against the background stars and constellations is quite rapid. It averages about 12.2° per day. A table giving the Moon’s daily celestial coordinates throughout the year can be found at Moon Ephemeris for 2015. This table lists a lot of other details about the Moon including its daily distance, apparent size, libration, phase age (days since New Moon) and the phase illumination fraction.

When a Full Moon occurs within 90% of the Moon’s closest approach to Earth in a given orbit, it is called a Super Moon. The Full Moon then appears especially big and bright since it subtends its largest apparent diameter as seen from Earth. The table below lists the Super Moons occurring in 2015.

              Super Moons for 2015

   Full Moon     Distance  Diameter  Relative
    (GMT)          (km)    (arc-min) Distance

Jul 31  10:43     365112     32.73    0.930
Aug 29  18:35     358993     33.29    0.985
Sep 28  02:50 t   356878 m   33.48    1.000
Oct 27  12:05     359324     33.26    0.982
Nov 25  22:44     366149     32.64    0.921

The Relative Distance listed in the Super Moon table expresses the Moon’s distance as a fraction between apogee (0.0) and perigee (1.0). For more information on Super Moons and a complete list of them for this century, see Full Moon at Perigee (Super Moon): 2001 to 2100.

Besides its obvious phases, the Moon also undergoes some additional extremes in its orbit including: Perigee and Apogee, Ascending/Descending Nodes, and Lunar Standstills. Each of these links covers lunar phenomena for the entire 21st Century.

Moon Phases Mosaic

As the Moon orbits Earth, its changing geometry with respect to the Sun produces the characteristic phases. This composite image is a mosaic made from 25 individual photos of the Moon and illustrates its phases over one synodic month. For complete details about this image, see Moon Phases Mosaic. The individual images included in this composite can be found in the Moon Phases Gallery. For more composites, see Moon Phases Mosaics. Photo copyright 2012 by Fred Espenak.

One of the first projects I tackled upon completing Bifrost Observatory in 2010 was to photograph the Moon’s phases every day for a complete month. Of course, the weather doesn’t always cooperate (even from sunny Arizona) so it actually took several months to complete the project. You can see the results at the Moon Phases Gallery. Clicking on any of the thumbnails pictures will give you an enlarged image with complete technical details. You can also visit Moon Phases Mosaics to see composites showing the Moon’s phases over a complete synodic month.

The NASA/Goddard Scientific Visualization Studio has used images from the Lunar Reconnaissance Orbiter (LRO) mission to create clever animations of the Moon’s ever changing phases and librations in 2015. The example below illustrates the Moon’s phase and libration at hourly intervals throughout 2015, as viewed from the northern hemisphere. Each frame represents one hour.

Besides presenting the Moon’s phase and apparent size, the video shows the Moon’s orbit position, sub-Earth and subsolar points, distance from the Earth at true scale, and labels of craters near the terminator. As the Moon orbits Earth, it appears to wobble and tip on its axis. This motion is called libration and it allows us to see about 59% of the Moon’s surface. The major cause of libration is due to our changing line of sight because of the Moon’s elliptical orbit. For more Moon animations from NASA/Goddard, see Moon Phase and Libration, 2015.

Finally, what discussion of the Moon would be complete without mentioning eclipses in 2015? There are two eclipses of the Moon and both of them are total. The first occurs on April 04 and the second, six months later on September 28. Both of them are visible from parts of North America. By coincidence, the September 28 eclipse also happens to be the closest Super Moon of 2015.

There are also two solar eclipses in 2015. The first is a total eclipse in the North Atlantic on March 20 (visible from the Faroe Islands and Spitzbergen). The second is a partial solar eclipse visible from most of southern Africa and Antarctica on September 13. For complete details on all these events, see Eclipses During 2015 (EclipseWise.com).

Watching the Moon’s phases wax and wane as well as the occasional lunar eclipse can best be enjoyed with the naked eye and binoculars. And you don’t even need a dark sky since the Moon is easily visible from the heart of brightly lit cities.

The Moon phases and lunar phenomena discussed here were all generated with computer programs I’ve written (THINK Pascal and FORTRAN 90 running on a Macintosh G4) using Astronomical Algorithms (Jean Meeus).

Fred Espenak


3 thoughts on “Moon in 2015

  1. Dear sir,
    Shalom!
    What a wonderful work you done. We thank you all.YHWH gave you good knowledge . We appreciate you so much.
    (1) http://eclipse.gsfc.nasa.gov/SEhelp/julian.html
    (1) is extremely useful to me to verify the day of Week and Days completed between any two dates.
    (2) http://www.astropixels.com/ephemeris/phasescat/phasescat.html
    (2) is useful to verify Scriptural Data which is produced from the Creation of Sun, Moon and stars (19th February, 4231 BCE, Tuesday) to CE 2139 in which The Messiah will come rule the whole World.
    The length of Scriptural Lunar month is 29.53135314 days and Tropical year is 365.2244898 days strictly according to Jeremiah 31:35-37, 33:19-26. So all the Jewish people and Christians who follow from (2) are keeping the feasts of YHWH in the wrong dates. I am willing to disprove all your calculations. Please give a chance to me. I am eagerly waiting for your reply.

    Thank you,
    Manasseh, Evangelist and Astronomer,
    India.

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