You are hereTHIS MONTH'S SKY - February 2010
THIS MONTH'S SKY - February 2010
THIS MONTH'S SKY
Celestial Events -- February 2010
TWO FOR ONE!
This month we feature two events that can be seen on the same evening this month -- February 16th.
If you are in NYC that evening, join us at 6 PM on the Brooklyn Heights Promenade at the end of Montague Street to see Jupiter and Venus below the crescent Moon, after which we will head to Cadman Plaza to see asteroid Vesta at 8 PM.
If you have questions, contact me (Rich Rosenberg) at president@aaa.org.
JUPITER AND VENUS MEET NEAR THE HORIZON
| It seems only yesterday when Jupiter was at opposition, rising at sunset and up the whole night. It was actually back in August, and in the intervening months the giant planet has moved further and further west. As February begins Jupiter sets in evening twilight.
Meanwhile, Venus, after a long period in the morning sky, has entered the evening sky, but so close to the Sun that it cannot yet be seen. On Tuesday, February 16 the two planets meet, one falling towards the Sun, the other escaping from it. This conjunction is spectacular, as Venus and Jupiter are only 33' (arc minutes) apart. (For comparison, the diameter of the Sun or Moon is about 30'.) |
Moon, Venus, Jupiter |
However, the observation will not be easy. Venus and Jupiter will be very low in a bright sky. Seeing them will probably require binoculars. We will require the southwest sky to be clear down to the horizon
Fortunately, there is a crescent Moon to help us find our targets. About 30 minutes after sunset (6 PM for NYC) look to the southwest for the Moon. It will be 24° above the horizon and almost directly above Venus and Jupiter.
Venus will be only 2° above the horizon. It is brighter than Jupiter, so hunt for it first. If you find Venus, Jupiter will be 33' to its upper right. Both will fit in a medium-power telescopic field.
After this meeting, Jupiter will be too near the Sun to be seen. It will have a conjunction with the Sun on February 28, entering the morning sky. On the other hand, Venus begins a several months long visit to the evening sky.
FINDING AN ASTEROID THE EASY WAY
| Now that you've seen Venus and Jupiter (hopefully), it's time to spot an asteroid. All you'll need is binoculars.
Asteroids, also called minor planets, are solar system bodies too small to be considered planets. Most of them lie in the region between Mars and Jupiter. The first asteroid to be discovered was Ceres in 1801. Three others were found quickly, including Vesta (number 4). Initially, these four were considered planets. However, after a long gap, more and more asteroids were found. With the advent of photography most astronomers came to believe they were not deserving of being called planets. (Sound familiar?) Although Ceres is much larger, Vesta is usually the brightest asteroid as seen from Earth because of its closer orbit and its high albedo (reflectivity). This year Vesta is at opposition on February 17, only a day after Jupiter and Venus can be spotted (see above). Why not combine the two events? While you needed a view to the southwest to see Jupiter and Venus, spotting Vesta will require an open area to the east. By about 8 PM the constellation Leo the Lion, in which Vesta currently resides, will be sufficiently high up. The brightest star in Leo is Regulus, a first-magnitude star that should be easy to spot (see Map 1). Regulus is the lowest star in a sickle-shaped asterism that looks like a lion's mane. Go up two stars from Regulus to the star Algieba. With binoculars, look at Algieba. You should see a fairly bright star to the lower right (see Map 2). This is the star 40 Leonis. In between Algieba and 40 Leonis will be Vesta! |
Map 1
Map 2
Map 3 |
Vesta will shine as bright as a sixth-magnitude star (6.1 to be exact). This means it would be visible with the naked-eye from a dark location. That won't be the case in New York, but with even small binoculars you should have no problem spotting it. In fact, if you use a telescope to enlarge the field of view, you may be able to notice Vesta's position change over time! Because solar system objects are relatively near to Earth, it is possible to see their motion, something stars are unable to do.
Because of their motion, like planets asteroids change their position from night to night. Vesta is currently moving to the west (upper right in the evening). Although it will fade somewhat to magnitude 6.2 on Mar 1, 6.8 on Apr 1, 7.3 on May 1 and 7.7 on June 1, it will remain visible with binoculars all through this time period.
Incidentally, Algieba itself is a lovely double star. If you have a telescope, train it on the star with high power.
Click to get sky charts and a description of the sky for this month.
PLANETS IN FEBRUARY
MERCURY is in the morning sky this month. It begins the month 7° above the horizon 30 minutes before sunrise. Mercury brightens from magnitude -0.2 to -0.6, but is getting closer to the Sun and is lost about midmonth.
VENUS (magnitude -3.9, diameter 9.8" to10.0", phase 100% to 98% lit) slowly works her way from the Sun and becomes visible (probably binoculars will be needed) around the middle of the month. Just as it becomes possible to see, Jupiter, on its way down, meets it. This makes for wonderful though difficult close gatherings of the two on Feb 14-16.described above. In the remainder of the month Venus gets higher and easier to see.
MARS (magnitude -1.3 to -0.6, diameter 14.1" to 12.2") was at opposition January 29. It spends the month retrograding (moving east to west) in Cancer. Mars is still nearly at its largest so it's a good time to view it telescopically.
JUPITER (magnitude -2.0, diameter 33.4" to 33.0") is in Aquarius. It is at the end of its apparition, becoming swallowed up in dusk after the middle of the month. But it goes out with a bang, albeit one that will require some effort (see above). Jupiter is at conjunction with the Sun on the 28th.
SATURN (magnitude +0.7 to +0.6, diameter 18.8" to 19.4") is in western Virgo. It rises about 9:30 PM on February 1 and 7:30 PM on February 28. It is beginning its period of prime viewing.
URANUS (magnitude +5.9, diameter 3.4") is in Pisces. It is becoming difficult to spot and soon will be lost to view.
NEPTUNE (magnitude +8.0, diameter 2.2") is in eastern Capricornus. It is too close to the Sun to be seen this month and will be in conjunction with the Sun on February 14.
PLUTO (magnitude +14.1, diameter 0.1") is still in western Sagittarius.
Asteroid 4 VESTA (magnitude 6.4 to 6.2) in Leo is at opposition on February 18. (Its magnitude is 6.1 on that date.) On the 16th it will pass between the bright stars Algieba and nearby 40 Leonis, making it an easy target (see above).
THIS MONTH'S EVENTS
(Times in EST)
| February 2 | The Moon is well below right of Saturn this morning. |
| February 4 | The Moon is 5° below Spica this morning. |
| February 5 | Last Quarter Moon at 6:48 PM. |
| February 7 | The Moon is 4° east of Antares this morning. |
| February 11 | A thin crescent Moon is 7° right of Mercury this morning. |
| February 13 | New Moon at 9:51 PM. |
| February 14 | An extremely thin Moon is near Jupiter and Venus at dusk (Chart) |
| Neptune is in conjunction with the Sun, entering the morning sky. | |
| February 15 | The Moon is now about 12° above Jupiter and Venus. |
| FEBRUARY 16 | TONIGHT AT 5 PM LOOK 22° BELOW THE CRESCENT MOON FOR VENUS AND JUPITER JUST ABOVE THE HORIZON. |
| AT 8 PM ASTEROID 4 VESTA CAN BE SEEN BETWEEN THE STAR ALGIEBA (GAMMA γ LEONIS) AND 40 LEONIS WITH BINOCULARS. | |
| February 18 | Asteroid Vesta is at opposition this morning. |
| February 21 | The Moon is about 1½° from the Pleiades tonight. |
| First Quarter Moon at 7:42 PM. | |
| February 25 | The Moon is 5° below Mars tonight. |
| February 27 | The Moon is 4° below Regulus tonight. |
| February 28 | Jupiter is in conjunction with the Sun, entering the morning sky. |
| Full Moon at 11:38 AM. |
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