You are hereTHIS MONTH'S SKY - January 2010
THIS MONTH'S SKY - January 2010
THIS MONTH'S SKY
Celestial Events -- January 2010
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On January 29th, the Sun, Earth and Mars are in a straight line. From the Sun, Earth would be passing Mars; from Mars, Earth would be passing the Sun, entering Mars' morning sky. Here on Earth, the Sun and Mars are opposite in the sky, and the event is called opposition. From our point of view, on the night of opposition Mars will rise as the Sun sets, and set when the Sun rises. It will be up all night. If the orbits of Earth and Mars were circles, Mars and Earth would be closest at this time. Since the orbits are elliptical, the two planets turn out to be nearest each other two days earlier. During the period before and after opposition, the brightness and size of Mars changes dramatically as viewed from Earth. This can be seen on Chart 1 to the right. This is due simply to the decreasing distance between the two planets. Usually outer planets such as Mars travel from west to east among the stars, a movement called direct motion. However, during the period before and after opposition, these planets reverse their direction (now called retrograde motion). Mars began moving retrograde on December 21 and will continue until March 11. This is due to an illusion. The effect is similar if you are riding in a fast car passing a slower one on a highway. From your point of view the slow car seems to be moving backwards with respect to stationary background objects. As a result of retrograde motion, Mars reverses its course, moving from Leo back into Cancer on January 9. All this is shown in Chart 2 to the right.
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Chart 1
Chart 2 |
Recall from the Sun's point of view, Earth is passing Mars at opposition. At their closest, Earth and Mars will be 61.7 million miles apart and its diameter 14.1" (arc seconds). Its magnitude will be -1.3. Actually, as oppositions of Mars go, this is a relatively poor one -- at the opposition of 2003 Mars was only 34.6 million miles away with a size of 25.1 arc seconds and had a magnitude of -2.9!
Look for Mars in the east. Its combination of brightness and color (actually more yellow-orange than red) is unique. On New Years' Day it moves from the constellation Cancer into Leo and spends the month moving closer to Regulus, Leo's brightest star.
Through a telescope you may be able to make out Mars' north polar cap (white with a tinge of blue). Another target is to try spot darker and lighter hues on the surface. With a fairly large telescope and good seeing, you may be able to match what you see with what are called albedo features, the best of which is Syrtis Major.
Map of albedo features: http://ralphaeschliman.com/mars/Alb-lamasm.pdf
MERCURY enters the morning sky on January 4 and fairly quickly becomes visible. It is best seen from the middle through the end of the month. During this time its magnitude increases from +0.5 (Jan 15) to +0.1 (Jan 20) to -0.1 (Jan 25) to -0.2 (Jan 30). Its size decreases from 8.5" (Jan 15) to 7.6" (Jan 20) to 6.9" (Jan 25) to 6.3" (Jan 30). However, this is made up by its phase, which increases from to 30% (Jan 15) to 47% (Jan 20) to 59% (Jan 25) 68% (Jan 30). Mercury is at greatest elongation west (25°) on Jan 27.
VENUS is in superior conjunction with the Sun on the 11th and is not visible all month.
MARS (magnitude -0.8 to -1.3, diameter 12.7" to 14.1") is at opposition on January 29 (actually closest to Earth on Jan 27). See "Mars at Opposition" above.
JUPITER (magnitude -2.1 to -2.0, diameter 35.0" to 33.4") moves from Capricornus into Aquarius on January 5. It is still a good target early in the month but sets at the end of twilight late in January.
SATURN (magnitude +0.9 to +0.7, diameter 17.8" to 18.7") is in western Virgo. It rises just before midnight on the New Year's Day and by 10 PM at the end of January. It keeps close company with Eta η Virginis all month, about 1° north of the star.
URANUS (magnitude +5.9, diameter 3.4") crosses from Aquarius into Pisces on January 14.
NEPTUNE (magnitude +8.0, diameter 2.2") is in Capricornus. On January 1 it is only 2° west of Jupiter, but the giant planet quickly moves away.
PLUTO (magnitude +14.1, diameter 0.1") is in Sagittarius and near the Sun.
The MOON begins January and 2010 a day after Full Moon. It passes well below of Mars on the 3rd and Saturn on the 6th. Last Quarter occurs on the 7th. A highlight this month is the near-occultation of the bright star Antares in Scorpius before dawn on the 11th (see "A Near Miss" above). Full Moon is on the 15th. Three days later the Moon passes well above Jupiter. On the 23rd it is at Last Quarter. The Moon will occult the Pleiades (unfortunately during daytime) on the 24th. Full Moon is on the 30th, with Mars close by.
THIS MONTH'S EVENTS
(Times in EST)
| January 2 | Earth is at perihelion, only 91,422,023 miles from the Sun. |
| January 3 | The Moon is 7° below Mars tonight. |
| The Quadrantid meteor shower peaks tonight. | |
| January 4 | Mercury is at inferior conjunction with the Sun, entering the morning sky. |
| January 6 | The Moon is 8° below Saturn tonight (they rise around midnight). |
| January 7 | Last Quarter Moon at 5:39 AM. |
| JANUARY 11 | THE MOON BARELY MISSES OCCULTING ANTARES IN THE PRE-DAWN SKY. THEY ARE CLOSEST ABOUT 7:35 AM. |
| Venus is in superior conjunction with the Sun, entering the evening sky. | |
| January 13 | The Moon is lower right of Mercury, a half hour before sunrise. |
| January 14 | Saturn is stationary, beginning retrograde motion. |
| January 15 | New Moon at 2:11 AM. There is an annular solar eclipse, visible in parts of Africa, India and the Far East. |
| January 18 | The crescent Moon is 8½°above Jupiter in the early evening. |
| January 23 | First Quarter Moon at 5:53 AM. |
| January 24 | The Moon is 6° west of the Pleiades. |
| January 25 | The Moon is 7° east of the Pleiades. During the daytime the Moon occulted the stars. |
| January 27 | Mars is closest to Earth (61,721,554 miles). |
| Mercury is greatest elongation west from the Sun (25°). | |
| JANUARY 29 | MARS IS AT OPPOSITION. |
| January 30 | Full Moon at 1:18 AM. |
| The Moon is 6° below Mars tonight. |
| For us in New York City, the Moon nearly occults (eclipses) the bright star Antares in the constellation Scorpius on the morning of January 11. Parts of Canada, New England and upstate New York will see an eclipse; we will see the Moon narrowly miss the bright reddish star.
The eclipse or near eclipse will take place after sunrise, unless you are in very northern Canada. To see the occultation or the near miss, take your scope out while it's still dark and aim it at Antares. Wait for the Moon to approach. From NYC the nearly-full Moon will barely miss the star, its edge getting within 1' (arc minute) at 7:33 AM. This is the last visible event of a series of occultations of Antares by the Moon. The changing path of the Moon means we'll have to wait a few years for the next one. For an explanation why the Moon's path changes, see the article "Why Is the Moon So High (or So Low)". |
Moon and Antares |
Click to get sky charts and a description of the sky for this month.
PLANETS IN JANUARY
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