Friday, 30 January 2015

Get out and look at Jupiter in February

February is a great month to view planet Jupiter and the Galilean moons. Why? Jupiter is at OPPOSITION on 6th February which means it is closest to Earth and therefore looks at its largest in telescopes.  Also, the maximum amount of light is reflected back to Earth from the planet.  At magnitude -2.4, it is very bright and stands out in the evening sky.  If you use a telescope, you will see the large disc of the planet, some of the cloud bands and check the dates below because you may get to see effects as seen in the image below:-
Image Credit : NASA/JPL/University of Arizona
The image was taken by the Cassini spacecraft and shows the sort of thing that you will see through a telescope this month.  The dark dot is the shadow cast on to the surface of the clouds of Jupiter by one of the Galilean moons.

When and where to look for Jupiter and its moons

Jupiter rises in the east at dusk and is visible all night, steadily tracking westwards through the night.  A telescope will allow many special effects to be seen in the month with the Galilean moons.


 2nd             - Io occults Europa @ 03.30 to 03.34
 3rd             - Io (and its shadow) transit Jupiter @ 19.30 to 21.47
 23rd & 24th  - Ganymede (and its shadow) transit Jupiter @ 19.26 to 00.45
 27th            - Io transits Ganymede @ 02.17 to 02.24

Occults means that one object blocks out the view of the one behind.
Transit is where one small object tracks in front of a larger object (like the shadow in the image above is in front of the planet).

Image Credit : Jonathan Foster (Star Learner)
The Galilean moons can be seen in binoculars and if you are a good photographer, make excellent opportunities for solar system images.  See what one of this year's Star Learners, Jonathan Foster, has found from his great photo of 9th January 2015.  If you measure the diameter along the line of the moons (the equator of the planet) you get 0.8 units.  Measuring at 90 deg through the poles you get 0.7 units.  So, your photo shows that the planet has been ‘stretched’ at the equator - which is what you get with spinning gas planets.  Now look at the moon that is ‘touching’ Jupiter.  It does not look like the moon on its own, which appears as a circle.  What you have is something called the ‘tear drop’ effect which is seen as two objects come alongside each other.  The classic one is in the transit of Venus across the Sun when Venus ’touches the edge of the Sun’.  So, Jonathan's picture has some amazing extras!

Have a great time looking at Jupiter.  Remember to wrap up warm!