2011 Skywatching Guide: Planets in the Solar System

2011 Skywatching Guide: Planets in the Solar System

The planets of our solar system are at tomes some of the most rewarding and simplest skywatching targets to spot, if you know when and where to look. Here's a look at how to observe the planets of the solar system in 2011:

Tip: Astronomers measure distances in the sky in terms of degrees. For reference, your clenched fist held at arm's length covers about 10 degrees of the night sky. The brightness of a planet or other object in the sky is measured as its "magnitude." The lower an object's magnitude, the brighter it appears, so objects with negative signs in front of their magnitude numbers below are exceptionally bright.


Mercury is often a difficult planet to find, but there are certain short periods each year when it can be seen with the naked eye with little effort, either just after sunset or before sunrise.

In 2011, Northern Hemisphere observers will two periods when Mercury can easily be located. During the second half of March, Mercury can be seen low in the west-northwest soon after sunset. During early September, Mercury can be seen low in the east-northeast Just before sunrise.

Southern Hemisphere observers will find Mercury well placed in the morning sky during early May, in the evening sky in late July, and in the evening sky in mid-November.

Mercury is the closest planet to the sun and has a thin atmosphere, no air pressure and an extremely high temperature.

DateEventDegrees from SunMagnitudeN. HemisphereS. HemisphereVisibility
January 9Greatest Elongation West23–0.3PoorGoodMorning
February 25Superior Conjunction     
March 23Greatest Elongation East19–0.2ExcellentPoorEvening
April 9Inferior Conjunction     
May 7Greatest Elongation West27+0.4PoorExcellentMorning
June 13Superior Conjunction     
July 20Greatest Elongation East27+0.3FairExcellentEvening
August 17Inferior Conjunction     
September 3Greatest Elongation West18–0.2ExcellentPoorMorning
September 28Superior Conjunction     
November 14Greatest Elongation East23–0.3PoorExcellentEvening
December 4Inferior Conjunction     
December 23Greatest Elongation West22–0.4GoodGoodMorning


2011 is not a very good year for observing Venus. It spends most of its time in the morning sky or on the far side of the sun.

January 8Greatest Elongation West–4.3
August 16Superior Conjunction–3.8

Venus, second planet from the sun, is one of the brightest natural objects in the sky and has been considered Earth’s sister planet.


2011 is also a poor year for observing Mars. It spends most of the year on the far side of the sun, and only begins to get large enough to see any detail on it in the last few weeks of the year.

February 4Conjunction+1.1


The planet Mars, also called the Red Planet, is a terrestrial planet with a thin atmosphere and surface features similar to Earth.


Jupiter spends the first part of the year in the constellation Pisces, except for a brief incursion into the constellation Cetus from February 24 to March 8.

Let the astrologers make of that what they will. It moves into Aries on June 6. It moves back into Pisces on Dec. 3. It is best viewed in the morning sky from July until the Oct. 29 opposition, when it moves into the evening sky for the rest of the year. The angular diameter at opposition will be 49.6 arcseconds. Binoculars will show the four largest satellites. A small telescope will show one or two cloud bands across the visible surface of the planet.

April 6Conjunction–2.1
Oct. 29Opposition–2.9


Jupiter is the largest planet in Earth’s solar system and has 63 moons encircling it. The planet is a giant ball of gas and liquid.


Saturn will spend all of the year in Virgo. Saturn can be viewed in the morning sky until April 4, when it moves into the evening sky.

From September to November it will be behind the sun, reappearing in December in the morning sky. The rings will gradually be opening over the year, making them easy to see in any telescope magnifying more than about 30x.

Saturn’s largest moon Titan is readily visible in a small telescope, and several more moons may be seen in larger telescopes. At opposition, the planet’s angular diameter will be 19.3 arc seconds.

April 4Opposition0.4
Oct. 13Conjunction0.7


Saturn, the sixth planet from the Sun, was named after the Roman God Saturn. The planet Saturn is a gas giant and one of the Jovian planets.


Uranus spends all of 2011 in the southwestern part of Pisces. It is best viewed in fall. It is in opposition on September 26, when it moves from the morning sky into the evening sky. Although it may be seen with the naked eye in a very dark sky, usually binoculars will be required to make it out. Its angular diameter is less than 4 arcseconds.

March 21Conjunction5.9
Sept. 26Opposition5.7

The planet Uranus, seventh planet from the sun, is a giant ball of gas and liquid and was the first planet discovered with a telescope.


Neptune starts out 2011 in Capricornus, but on Jan. 23 it moves into Aquarius for the rest of the year. It is best viewed during the late summer and early fall. It is in opposition on Aug. 22, when it moves from the morning sky into the evening sky. Binoculars or a small telescope will be required to see it. The angular diameter is about 2 arcseconds.

Feb. 17Conjunction8.0
Aug. 22Opposition7.8


The planet Neptune is the eighth planet from the Sun and has a thick atmosphere and the fastest winds in the solar system.
All about our solar system, outer space and exploration

Source: RASC Observer’s Handbook 2011 and Starry Night Software

This 2011 Planets Skywatching Guide is provided by Starry Night Education


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