Moon Phases for 2013

Moon Phases Mosaic

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.

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.

The table below lists the time and date of the Moon’s phases throughout 2013. The time of each phase is given in Greenwich Mean Time or GMT (a.k.a. Universal Time or UT). To convert GMT to Eastern Standard Time (EST) just subtract 5 hours. To convert GMT to other time zones, visit Time Zones.

                    Moon Phases for 2013 (GMT)

   New Moon      First Quarter      Full Moon       Last Quarter
-------------    -------------    -------------    -------------   
                                                   Jan  5  03:58    
Jan 11  19:44    Jan 18  23:45    Jan 27  04:38    Feb  3  13:56    
Feb 10  07:20    Feb 17  20:31    Feb 25  20:26    Mar  4  21:53    
Mar 11  19:51    Mar 19  17:27    Mar 27  09:27    Apr  3  04:37    
Apr 10  09:35    Apr 18  12:31    Apr 25  19:57    May  2  11:14    
May 10  00:29    May 18  04:35    May 25  04:25    May 31  18:58    
Jun  8  15:56    Jun 16  17:24    Jun 23  11:32    Jun 30  04:54    
Jul  8  07:14    Jul 16  03:18    Jul 22  18:15    Jul 29  17:43    
Aug  6  21:51    Aug 14  10:56    Aug 21  01:45    Aug 28  09:35    
Sep  5  11:36    Sep 12  17:08    Sep 19  11:13    Sep 27  03:56    
Oct  5  00:35    Oct 11  23:02    Oct 18  23:38    Oct 26  23:41    
Nov  3  12:50    Nov 10  05:57    Nov 17  15:16    Nov 25  19:28    
Dec  3  00:22    Dec  9  15:12    Dec 17  09:28    Dec 25  13:48    

I’ve generated a Moon phases table 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).

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 2013. For instance, the first synodic month of 2013 is 1 hour 7 minutes shorter than the mean while the fifth month (beginning May 10) is 2 hours 43 minutes longer than the mean.

              Synodic Months for 2013 

   Date/Time of        Length of     Dif. from
  New Moon (GMT)     Synodic Month   Mean Month 
------------------   -------------  -----------
2013 Jan 11  19:44    29d 11h 37m    -01h 07m
2013 Feb 10  07:20    29d 12h 32m    -00h 12m
2013 Mar 11  19:51    29d 13h 45m    +01h 00m
2013 Apr 10  09:35    29d 14h 53m    +02h 09m
2013 May 10  00:29    29d 15h 27m    +02h 43m
2013 Jun 08  15:56    29d 15h 17m    +02h 33m
2013 Jul 08  07:14    29d 14h 35m    +01h 51m
2013 Aug 06  21:51    29d 13h 45m    +01h 01m
2013 Sep 05  11:36    29d 12h 58m    +00h 14m
2013 Oct 05  00:35    29d 12h 15m    -00h 29m
2013 Nov 03  12:50    29d 11h 33m    -01h 11m
2013 Dec 03  00:22    29d 10h 53m    -01h 51m

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 must await a future blog post.

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 the above links covers lunar phenomena for the entire 21st Century.

The Moon phases and lunar phenomena tables were all generated with a computer program I wrote (THINK Pascal running on a Macintosh G4) using Astronomical Algorithms (Jean Meeus).

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.

One of the first projects I tacked 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 clever animation below illustrates the Moon’s phases throughout 2013 (at 1-hour intervals). NASA’s Lunar Reconnaissance Orbiter (LRO) team created the video using data from both LRO and Clementine (a 1990s lunar orbiter mission).

Besides presenting the Moon’s phase and apparent size, the video shows the Moon’s orbital position with respect to the Sun and Earth, and it’s distance from Earth. 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.

Watching the Moon’s phases wax and wane 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.

Fred Espenak

Events for January 2013

The following table gives the date and time of important astronomical events for January 2013. The time of each event is given in Greenwich Mean Time or GMT (a.k.a. Universal Time or UT). To convert GMT to Eastern Standard Time (EST) just subtract 5 hours. To convert GMT to other time zones, visit Time Zones. Some of the astronomical terms used in the calendar are explained in Definitions.

 Date    GMT   Astronomical Events for January 2013
------  -----  --------------------------------------------
        (h:m)
Jan 01  21:13  Regulus 5.9°N of Moon
Jan 02  00:59  Earth at Perihelion: 0.98329 AU
Jan 03  14     Quadrantid Meteor Shower
Jan 04  03     Mercury at Aphelion 
Jan 05  03:58  LAST QUARTER MOON 
Jan 05  19:54  Spica 0.6°N of Moon
Jan 07  01:28  Saturn 3.7°N of Moon
Jan 07  23:50  Moon at Ascending Node 
Jan 08  22:55  Antares 5.9°S of Moon
Jan 10  10:26  Moon at Perigee: 360048 km
Jan 10  11:36  Venus 2.8°S of Moon
Jan 11  19:44  NEW MOON 
Jan 18  09     Mercury at Superior Conjunction 
Jan 18  23:45  FIRST QUARTER MOON 
Jan 21  01:19  Moon at Descending Node 
Jan 22  02:57  Jupiter 0.5°N of Moon: Occultation
Jan 22  10:52  Moon at Apogee: 405313 km
Jan 22  11:13  Aldebaran 4.0°S of Moon
Jan 24  12     Mars at Perihelion 
Jan 27  04:38  FULL MOON 
Jan 29  02:57  Regulus 5.8°N of Moon

Astronomical events calendars for complete years and five time zones are available through the links below.

Time Zones Calendars of Astronomical Events
Greenwich Mean Time 2013 2014 2015 2016 2017 2018 2019 2020
Eastern Standard Time 2013 2014 2015 2016 2017 2018 2019 2020
Central Standard Time 2013 2014 2015 2016 2017 2018 2019 2020
Mountain Standard Time 2013 2014 2015 2016 2017 2018 2019 2020
Pacific Standard Time 2013 2014 2015 2016 2017 2018 2019 2020

For additional time zones and years, see Astronomical Events Calendars.

The sky events tables were all generated by a computer program I wrote (THINK Pascal running on a Macintosh G4) using Astronomical Algorithms (Jean Meeus).

Fred Espenak

Moon Halo

Have you ever seen an enormous hazy ring surrounding the Moon? This is an atmospheric phenomenon that goes by a number of names including Moon Ring, Moon Halo, and Winter Halo.

The halo appears as a whitish ring over 80 times the diameter of the Moon, and centered on the lunar orb. It only occurs when a thin veil of high cirrus clouds covers the sky, which often precedes a change in the weather as a cold front approaches. The cirrus clouds are composed of hexagonal ice crystals suspended in the upper atmosphere. Each ice crystal acts like tiny 6-sided prism with 60° sides.

Moon Halo

A halo around the Moon can form when the ice crystals in high altitude clouds refract the Moon’s light into a ring. For complete details about this image, see Moon Halo. Photo copyright 2012 by Fred Espenak

As bright moonlight shines through the ice crystals, some of the light rays are refracted or bent through an angle of approximately 22°. The actual angle of refraction depends on the color of the light. For instance, red light is refracted about 21.54° while blue light is refracted 22.37°. Since the Moon’s light is simply reflected sunlight, it consists of all the colors of the rainbow. This gives the inner edge of the halo a reddish tinge while the outer edge is bluish.

The resulting Moon halo has an apparent radius of 22° (or a diameter of 44°). It is several degrees thick because the Moon itself is 1/2 degree in diameter, and the ice crystals are randomly oriented in the cirrus clouds. These factors tend to spread the ring out a few degrees.

Moon halos are best seen when the Moon is within several days of Full Moon. Because the Moon is then at its brightest, it is easier to see a faint Winter Halo if the weather conditions are right. This 22° halo phenomenon is also visible around the Sun but is frequently overlooked because of the Sun’s intense glare. By covering the Sun with your outstretched hand it’s easier to spot a Sun Halo.

Fred Espenak

Andromeda Galaxy

Andromeda Galaxy - M31

The Andromeda Galaxy or M31 is the nearest spiral galaxy to our own Milky Way Galaxy. For complete details about this image, see Andromeda Galaxy. Photo copyright 2012 by Fred Espenak

One of the greatest debates of American astronomy occurred in 1920. It centered on the true nature of the spiral nebulae – pinwheel shaped hazy patches of light visible in the night sky. Harlow Shapley believed they were located relatively nearby inside our own Milky Way. In contrast, Heber Curtis insisted the spiral nebulae are actually ‘island universes’ far outside the Milky Way and are comparable in size and nature to our own galaxy.

Edwin Hubble (namesake of the Hubble Space Telescope) settled the Great Debate by using Cepheid variable stars to measure the distance to the Great Andromeda Nebula – the biggest and brightest the spiral nebulae. Using the 100″ Hooker Telescope, Hubble showed that Andromeda was actually a galaxy like the Milky Way and was located at a distance of about 1.5 million light-years.

Modern measurements of the Andromeda Galaxy place it at a distance of approximately 2.5 million light-years from Earth. Located in the constellation Andromeda, the Andromeda Galaxy can be seen with the naked eye from a dark moonless sky as a hazy oval patch about twice the diameter of the Full Moon. During December evenings, Andromeda passes overhead around 8 pm from mid-northern latitudes. A pair of 7×50 binoculars provides a good view of the galaxy.

Constellation of Andromeda

The constellation Andromeda was known to the ancients as the Chained Maiden. In this wide angle view of the constellation, the Andromeda Galaxy is visible as a hazy oval. For complete details about this image, see Andromeda. Photo copyright 2012 by Fred Espenak

The 18th century French comet hunter Charles Messier included the Andromeda Galaxy as entry M31 in his famous catalog of deep sky objects. In August of 1764, Messier gave the following description:

“The beautiful nebula of the belt of Andromeda, shaped like a spindle; M. Messier has investigated it with different instruments, and he didn’t recognise a star: it resembles two cones or pyramides of light, opposed at their bases, the axes of which are in direction NW-SE; the two points of light or the apices are about 40 arc-minutes apart; the common base of the pyramids is about 15 (arc-minutes).”

The Andromeda Galaxy is the closet spiral galaxy to the Milky Way and it resembles how our own galaxy would appear from a great distance. Recent research indicates that M31 was formed from the collision and merger of two smaller galaxies about 10 billion years ago. Some 2 to 4 billion years ago, M31 experienced a close encounter with the Triangulum Galaxy (M33). The encounter triggered high levels of star formation in M31, and disturbed M33’s outer disk.

M31 is accompanied by two satellite elliptical galaxies known as as M32 (NGC 221) and M110 (NGC 205). Both are easily seen and photographed with amateur telescopes. Research with larger telescopes has identified a total of 14 dwarf satellite galaxies gravitationally associated with M31.

Andromeda Galaxy - M31

This close-up of the Andromeda Galaxy clearly shows its two satellite elliptical galaxies known as as M32 (NGC 221) and M110 (NGC 205). The image was shot with a 12″ ASA telescope from Bifrost Observatory in Portal, Arizona. For complete details, see Andromeda Galaxy. Photo copyright 2012 by Fred Espenak

The Andromeda Galaxy and its satellites, along with the Milky Way Galaxy and the Triangulum Galaxy (M33), are all part of the Local Group of about 54 nearby galaxies. The gravitational center of the group is located somewhere between the Milky Way and M31.

The Andromeda Galaxy is approaching the Milky Way at about 2 billion miles per year and is expected to collide with us in about 4.5 billion years. Although the outcome is uncertain, it is likely that the galaxies will merge to form a giant elliptical galaxy. This is a common event among interacting galaxies. In any case, the collision will take place near the end of the Sun’s expected lifetime.

What an amazing view it will be when the Andromeda Galaxy dominates the night sky a few hundred million years before the collision! (see Andromeda Collision for a preview)

Fred Espenak

Toutatis

Toutatis

Minor planet Toutatis (4179) is captured in a series of 60-second exposures (with a 60-second gap between exposures) on December 12 shortly before reaching its closest distance to Earth (7 million kilometers). Photo copyright 2012 by Fred Espenak

During the second week of December 2012, the minor planet Toutatis (4179) made a close approach to Earth passing within 7 million kilometers (4 million miles (on Dec. 12 at 06:40 UT). This is about 18 times the average Earth-Moon distance which is quite close relative to the scale of the Solar System.

The rapid motion of Toutatis is revealed in a video made from a series of 60-second exposures shot over a 102-minute period on December 13. Photo copyright 2012 by Fred Espenak

Toutatis is an irregular 5-kilometer chunk of rock that makes a close approach to Earth every four years. Its orbit is chaotic because of the large perturbations it undergoes from the gravitational interact with Earth and Jupiter. In fact, Toutatis is in a 3:1 orbital resonance with Jupiter, and a 1:4 orbital resonance with Earth (which is why it passes close to Earth every 4 years).

Toutatis was first sighted in February 1934, but it was then lost. It wasn’t until January 1989 until it was rediscovered by French astronomer Pollas.

According to Minor Planet Circ. 16444: “Named after the Gaulish god, protector of the tribe. This totemic deity is well known because of the cartoon series “Les aventures d’Asterix” by Uderzo and Goscinny. This tells the stories of two almost fearless heroes living in the last village under siege in Roman-occupied Gaul in 50 B.C., and whose only fear is that the sky may fall onto their heads one day. Since this object is the Apollo object with the smallest inclination known, it is a good candidate to fall on our heads one of these days… But as the chief of the village always says: “C’est pas demain la veille…” Citation written by the discoverer and A. Maury and endorsed by J. D. Mulholland, who with Maury obtained the discovery plates.”

I imaged Toutatis on two nights from Bifrost Observatory using the ASA N12 Astrograph. It was quite amazing to see how quickly the minor planet crossed the field of the camera – over 3 degrees per day.

The rapid motion of Toutatis is revealed in a video made from a series of 60-second exposures shot over a 102-minute period on December 13. Photo copyright 2012 by Fred Espenak on Vimeo.

Because of its close proximity to Earth, astronomers of NASA’s Goldstone dish were able to obtain radar images of Toutatis with unprecedented resolution.

According to Michael Busch (NRAO): “Toutatis appears to have a complicated internal structure. Our radar measurements are consistent with the asteroid’s little lobe being ~15% denser than the big lobe; and they indicate 20% to 30% over-dense cores inside the two lobes.” This suggests that Toutatis may be a loose composite of smaller space rocks. “Toutatis could be re-accumulated debris from an asteroid-asteroid collision in the main belt,” says Busch.

Fred Espenak

Radar Image of Toutatis from Goldstone

Radar Image of Toutatis from Goldstone

Sir Patrick Moore

Sir Patrick Moore, well-known broadcaster, astronomy popularizer and enthusiastic amateur astronomer died earlier today (Dec. 9, 2012) at age 89. I had the opportunity to spend some time with Patrick for a “Sky At Night” interview back in 2006. He was a most gracious and friendly host and I was very honored to meet him at his home in Selsey, England. We spoke at length about eclipses and his work as an astronomy popularized at the dawn of the television era.

Patrick Moore was an inspiration to several generations of astronomers in England and around the world. He wrote dozens of books on astronomy, created Caldwell Catalog of deep sky objects, and spread the wonders and joys of astronomy to millions of people through his frequent television broadcasts for the past 55 years. It is safe to say that the popularity of astronomy today among the general public is in no small part due to this man.

Astronomy has lost one of its most treasured friends but his legacy will live on.

Fred Espenak

Patrick Moore in 2006

Fred and Pat Espenak visited Sir Patrick Moore at his home in Selsey, England in January 2006. His enthusiasm for spreading the thrill of astronomy was undiminished in spite of his 80+ years.

Jupiter’s 2012 Opposition

TauJup12-02w.jpg

This image is a wide angle view of the sky looking east around 8 pm local time on December 3. Orion has just risen (lower right) and above it is Taurus and the planet Jupiter (near center) shining as a brilliant white star. For complete details about the photo see Taurus & Jupiter – 2. Photo copyright 2012 by Fred Espenak.

Go out any clear evening in December and look east around 7 or 8 pm. You’ll see a dazzlingly bright star which is, in fact, the planet Jupiter. Earlier this week (Dec. 3) the giant planet was at opposition with the Sun. In other words, the Sun and Jupiter were in opposite directions in the sky as seen from Earth. While the Sun is highest in the sky around 12 noon, Jupiter is best seen at 12 midnight. If you could look down on the Solar System from above, you would see that the Sun, Earth and Jupiter are lined up (in that order).

For amateur astronomers, this is the perfect time to observe Jupiter because it is closest to Earth and is visible all night long. Jupiter’s distance is currently 4.07 AU from Earth and 5.05 AU from the Sun. Compare this to Jupiter’s position six months from now when it is in conjunction with the Sun and hidden in the solar glare. It will then be 6.14 AU from Earth and 5.12 AU from the Sun (see: Jupiter 2012 for a complete ephemeris of the planet during the year).

Jupiter is the largest planet in the Solar System and has an equatorial diameter of 143,000 kilometers. This is 11.1 times Earth’s diameter. Even giant Saturn is just 84% the diameter of Jupiter. Of course, if we compare Jupiter to the Sun, it’s diameter is a mere 10% of the Sun’s. At a mean distance over five times greater than Earth’s from the Sun, Jupiter takes 11.86 years to complete one orbit around our star.

Jupiter currently subtends an angle of 48.5 arc-seconds – the largest of the year. Even a modest telescope will reveal Jupiter’s disk, its cloud belts (appearing like pale stripes), and its four biggest moons Io, Europa, Ganymede, and Callisto (appearing like bright stars aligned in the same plane as Jupiter’s cloud belts).

The movie above is time-lapse of Jupiter, taken by NASA’s Voyager 1 spacecraft as it approached the planet in February 1979. It covers a period of 95 hours, and and shows how rapidly Jupiter’s clouds rotate. It also features appearances of three of Jupiter’s innermost moons: Io, Europa and Ganymede. You can also see the shadows of the moons race across Jupiter’s clouds tops.

Although I’ve done a lot of astrophotography, none of it involves close-ups of the planets. However, Damian Peach, an amateur astronomer from southern England is a master of high resolution planetary imaging. You’d be excused if you mistake Peach’s images for something shot by NASA’s Voyager. His images are that good! Take a look at some of Peach’s recent images of Jupiter.

TauJup12-01w

Jupiter reached opposition with the Sun just two hours before this image was made on Dec. 3. Jupiter appears as a brilliant white star above the Hyades star cluster in Taurus. The dipper-shapped Pleiades is to the upper right. For complete details about the photo see Taurus & Jupiter – 1. Photo copyright 2012 by Fred Espenak.

Even without a telescope, the view of Jupiter in Taurus is beautiful. Below Jupiter is the the v-shaped group of stars called the Hyades. The bright orange star in the Hyades is Aldebaran. To the upper right is a tiny dipper-shaped star cluster known as the Pleiades. I’ll have more to say about the Pleiades in a future blog.

Over the course of the next few months, Jupiter will slowly change position against the background stars of Taurus. And just in case you’re wondering, the placement of Jupiter in Taurus has absolutely no significance on the life and affairs of Earth’s inhabitants. Astrology has been around for thousands of years and yet, there is no scientific evidence to support any of its principles, postulates or claims. To put it more colloquially, astrology is a bunch of baloney! Read all about it in Phil Plait’s blog on astrology.

In the meantime, go out tonight and enjoy the view of Jupiter and Taurus.

Fred Espenak