Tuesday, December 30, 2008

Moon passes Jupiter and Mercury

Last night, the Moon passed Jupiter and Mercury, which were very low in the southwestern sky at 6:00 p.m. Tonight, the Moon will be situated half way between brilliant Venus and twinkling Jupiter. If you look closely, you will see a dimmer Mercury directly to the left of Jupiter.

New Year's Eve evening, the Moon will be next to Venus and Mercury will be next to Jupiter.

Such is our view from Earth ...

Monday, December 29, 2008

The evening southwestern horizon

If skies are clear this week, there are three planets visible in our southwestern evening sky. As it has been doing all month, Venus climbs higher and becomes brighter. Jupiter has dropped closer to the horizon and tiny Mercury pushes slightly higher than Jupiter.

Tonight, the thin crescent moon sits just above the Jupiter - Mercury duo. Binoculars help give a better view.
By New Year's Eve, the moon moves next to Venus, giving a striking combination.

Such is our view from Earth ...

Sunday, December 21, 2008

Astronomically, winter is here

Today the Earth reaches the point in its orbit where its polar axis reaches its most extreme angle with respect to the position of the sun. Our planet's north pole is tilted at its greatest angle away from the sun, and our south pole is tilted at its greatest angle towards the sun. In other words, it is the first day of winter in the northern hemisphere and the first day of summer in the southern hemisphere.

Also, the time that the sun is above the horizon is the least for the next 365 days, being 9 hours 36 minutes for Roanoke. Compare this with the time on the first day of summer which is 14 hours 44 minutes.

Such is our view on Earth ...

Sunday, December 7, 2008

Line Up

Four planets and the Sun arrange themselves in a line up this week. Mars, on the far side of its orbit, is situated behind the Sun and so is Mercury. Because they appear close to the Sun, they can not be seen. Jupiter sets about 7:45 p.m. and can be found in the southwest 30 minutes after sunset. Venus, quite a bit brighter than Jupiter, follows it to the horizon setting around 8:00 p.m.

This time every year the Sun is located not in a familiar constellation of the zodiac, but a relatively unknown one, Ophiuchus. It drifts eastward through it until December 18 when it crosses the border into Sagittarius.

The final "bright" planet, Saturn, rises in the east about 11:45 p.m. in Leo. By dawn, it is high in the south. The 3rd quarter Moon is close to it on the 18th and 19th.

Such is our view from Earth ...

Wednesday, December 3, 2008

Position of Jupiter and Venus

From our point of view on Earth, Venus and Jupiter have appeared near each other over the past couple of weeks. Jupiter happens to lie almost on the ecliptic, which is the plane of the Earth's orbit projected onto the celestial sphere. Venus is a couple of degrees below it.

Monday evening's close triple conjunction had the Moon also 2ยบ below the ecliptic. About 1 pm on that day, the Moon occulted Venus, ie., it appeared to move in front of it. It was daytime here in Virginia, but it was early evening in London. They must have had a spectacular sight!

Such is our view from Earth ...