news sciences: Look for Mercury, west after sunset

Before going to bed this evening, look eastrward to catch the moon and Regulus in the eastern sky. If your a night owl, up until late evening or around midnight, you might even catch the brilliant planet Jupiter above the hrorizon.

Before going to bed this evening, look eastward to catch the moon and Regulus in the eastern sky. If you’re a night owl, up until late evening or around midnight, you might even catch the brilliant planet Jupiter above the horizon.

Tonight – December 28, 2015 – or any evening around now, look for Mercury, the solar system’s innermost planet. This little world is bright, but it’s often obscured by the sun’s glare. On December 28, according to North American clocks (December 29 at around 0300 UTC), Mercury reaches its greatest eastern elongation from the setting sun. That’s its greatest distance from the sun on our sky’s dome for this evening apparition. It means that Mercury is staying out for a maximum period of time after sunset right now.

Look for this world low in the western sky and near the sunset point on the horizon, starting 50 to 60 minutes after sundown. Mercury’s precise setting time depends on where you live worldwide. At mid-northern latitudes, Mercury sets about 90 minutes after sunset; at temperate latitudes in the Southern Hemisphere, it’s closer to 80 minutes after the sun goes down.

Given an unobstructed horizon and a clear sky, you should be able to spot Mercury with the unaided eye. After all, this world shines on par with the sky’s brightest stars.

Sometimes, the murky haze of evening twilight obscures the view of Mercury. So bring along binoculars, if you have them!

If you live in the Northern Hemisphere, the stars of the famous Summer Triangle asterism may help guide you to Mercury. Although Mercury is actually brighter than any Summer Triangle star, Mercury sits much closer to glare of evening twilight. For that reason, one or more stars of the Summer Triangle – Vega, Deneb and Altair – may pop out into the darkening twilight before Mercury does. At mid-northern latitudes, look for Mercury to the lower left of the Summer Triangle. See the first chart below.

Or … Are you a morning person? Then check out the second chart below. Before dawn now, you can see four planets. Going upward from the sunrise – along the ecliptic, or sun’s path – they are Saturn, Venus, Mars and Jupiter.

Soon, Mercury will leave the evening sky and join the morning planets. Then all five visible planets will be up simultaneously – for the first time since 2006!

All five visible planets at once in January, 2016

EarthSky’s guide to the visible planets

From the Northern Hemisphere, you may be able to use the Summer Triangle to locate Mercury near the horizon. Simply draw an imaginary line from Vega and through Altair to Mercury. Binoculars could be helpful!

From the Northern Hemisphere, you may be able to use the Summer Triangle asterism – three bright stars in three separate constellations – to locate Mercury near the horizon. Simply draw an imaginary line from Vega and through Altair to Mercury. Binoculars could be helpful!

Are you a morning person? Then look for the four morning planets. Venus and Saturn appear low in the southeast, not far from the sunrise point on the horizon. Mars is to the south at this early morning hour whereas brilliant Jupiter shines to the right of Mars and Spica, outside the sky chart. The green line depicts the ecliptic - Earth's orbital plane projected outward onto the great dome of sky.

The morning planets Saturn, Venus and Mars. Jupiter is there, too, outside this chart.

Bottom line: Mercury is at greatest elongation – farthest from the sun on our sky’s dome – on December 29 at 0300 UTC (evening of December 28 for North America). After this, Mercury will dim somewhat and sink rapidly closer to the sun each day. Even so, Mercury should remain in good view in the evening sky for at least several more days.

from EarthSky http://ift.tt/1Izek6O