AVAILABLE MONTHS

2010: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

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.

UTC: CELESTIA'S DISPLAY OF TIME

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

EARTH AT PERIHELION: 2011 Jan 3

Contrary to popular belief, the orbit of Earth actually carries us closest to the Sun (i.e. at "perihelion") in winter NOT in summer. This year, Earth is at perhelion on January 3, with versions 1.6.x and 1.4.1 of CELESTIA respectively indicating that this occurs at 18:40 UTC and 18:41 UTC, when the distance between Earth's and the Sun's centers dips to 0.983341046 AU or 147,105,727 km (91,407,261 miles). This is determined by our "Earth-Sun Distance" script.

APPARENT PATHS OF THE PLANETS

This month, the Sun chases Mars out of Sagittarius, while Jupiter and Uranus linger in western Pisces.

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 these links as often as you like, and keep an eye on CELESTIA's clock at the top right of its 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: 2011 Jan

Having finished its retrograde motion very near the end of last month, Mercury spends January moving eastward, "chasing" Mars and the Sun out of Sagittarius (1.6.x) (1.4.1)

VENUS: 2011 Jan

Venus continues moving to the east, exiting Libra, then proceeding through Scorpius and Ophiuchus (1.6.x) (1.4.1)

MARS: 2011 Jan

January finds Mars "chased" out of Sagittarius by the Sun, but not quite overtaken by it at month's end in central Capricornus (1.6.x) (1.4.1)

JUPITER & URANUS: 2011 Jan

Jupiter and Uranus remain in western Pisces for the entire month (1.6.x) (1.4.1)

SATURN: 2011 Jan

Saturn slows in central Virgo, managing to commence its retrograde motion by month's end (1.6.x) (1.4.1)

NEPTUNE: 2011 Jan

Slow-moving Neptune exits Capricornus and enters Aquarius near month's end (1.6.x) (1.4.1)

CELES-TIPS

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.

If CELESTIA's clock (i.e. the program's date and time) is not visible at the top right of its window, press the V key until you see it. This will also turn on information text in other corners as well. This text will help you keep track of several aspects of the event you're viewing.
Pressing the "un-shifted" L key and K key respectively will speed up and slow down CELESTIA's flow of time by a factor of 10 in version 1.6.x and 1.4.1.
Pressing Shift+L and Shift+K respectively will speed up and slow down CELESTIA's flow of time by a factor of 2 in version 1.6.x only.
Pressing the J key (either shifted or "un-shifted") will reverse CELESTIA's flow of time in version 1.6.x and 1.4.1.

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

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THE SUN

APPARENT PATH OF THE SUN: 2011 Jan

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 January. 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.

HALF OF EARTH IN SUNLIGHT & DARKNESS

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!

THE MOON

PHASES OF THE MOON: 2011 Jan

In UTC per CELESTIA 1.6.x:
New: Jan 4, 9:03. 1st Qtr: Jan 12, 11:32.
Full: Jan 19, 21:22. Last Qtr: Jan 26, 12:57.
(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.

LUNAR APOGEE & PERIGEE: 2011 Jan

Per CELESTIA 1.6.x:
Apogee: Jan 10, 05:38 UTC; 404, 977 km.
Perigee: Jan 22, 00:12 UTC; 362,793 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.)

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.

LUNAR ANALEMMA: 2011 Jan

Here is the lunar analemma, generated by the Moon's positions relative to the mean lunar orbit and the Ecliptic at 0:00 UTC every day of January.

This phenomenon can be observed using our "Moon's Apparent Path" script. The analemma's change of shape month after month begins to give us an idea of just how irregular the lunar orbit is.

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

SHADOW WORKS

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

All involving Ganymede and Io, 3 simultaneous solar eclipses occur on Jupiter in January. On a good number of other occasions, 2 or more Galileans can be seen near Jupiter. Here are highlights of the 30 solar eclipses that Io, Europa, Ganymede and Callisto produce this month, while the shadow of Jupiter stretches to the east (left). When Io and Europa enter the Jovian shadow this month, they do so hidden by Jupiter, but many times they can be seen emerging from it.

With this Galilean info, you can understand why some events involving more than one moon repeat. It also lets you predict when they may do so again.
Periods:
Io: 1.769 days
Europa: 3.551 days
Ganymede: 7.155 days
Callisto: 16.69 days
Resonances:
Io & Europa: 2 to 1
Io & Ganymede: 4 to 1
Europa & Ganymede: 2 to 1

Jan 1: Io, Europa & Callisto move behind Jupiter; then speedy Io passes Callisto (1.6.x) (1.4.1)
Jan 3: Ganymede and Io produce the first of three simultaneous solar eclipses with a 7-day repeating cycle on Jupiter this month (1.6.x) (1.4.1)
Jan 10: Io, Europa and Callisto are just east of Jupiter, all within about one Jovian diameter (1.6.x) (1.4.1)
Jan 14: Io and Ganymede are just off Jupiter's eastern limb (1.6.x) (1.4.1)
Jan 17: Ganymede and Io produce the third of their three simultaneous solar eclipses this month; also, Io passes Ganymede and both pass Callisto (1.6.x) (1.4.1)
Jan 21: Io and Ganymede "converge" on Jupiter (1.6.x) (1.4.1)
Jan 24: Io "overtakes" Ganymede just off Jupiter's eastern limb (1.6.x) (1.4.1)
Jan 26: Io and Callisto pass Europa a few Jovian diameters east of Jupiter (1.6.x) (1.4.1)

SATURN

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 29 and no solar eclipses on Saturn in January. Version 1.6.x reveals only 1 simultaneous solar eclipse this month, and it's NOT an obvious one!

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

Jan 1: Tethys casts its shadow on Saturn, as it now does about every 2 days (1.6.x only)
Jan 1: Dione casts its shadow on Saturn, as it now does about every 2¾ days (1.6.x only)
Jan 23: Dione and Tethys cast their shadows on Saturn simultaneously (1.6.x only)

URANUS, NEPTUNE & Dwarf Planet PLUTO

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

News: 2011 January

News: