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what's up for februari Jupiter's moons

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Jupiter's largest moons were first seen

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400 years ago in early 1610 hello and

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welcome I'm Jane Houston Jones at NASA's

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Jet Propulsion Laboratory in Pasadena

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California on the 7th of January 1610 in

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Padua Italy Galileo looked up above the

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constellation Orion he aimed his

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telescope at the well-known starry

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wanderer the planet Jupiter which was

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near Orion that night what he saw

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through his telescope startled him and

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marked the beginning of modern astronomy

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Jupiter was not just one object as he

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wrote and drew in his journal there are

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three stars in the heavens moving about

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Jupiter as Venus and Mercury around the

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Sun he wrote Galileo's January seventh

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observation showed three stars the one

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start to the west was Ganymede and to

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the east there were two objects one was

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the moon Callisto and the other was a

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tight pairing of Io and Europa IO and

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Europa appeared so close together they

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looked like one object in Galileo's

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modest telescopic view on January eighth

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he saw a different line up altogether

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there were three stars on one side of

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the planet aya was the moon closest to

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the planet followed by Europa and

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Ganymede to cloudy nights and two

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additional observations later on January

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thirteenth Galileo identified a fourth

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object orbiting Jupiter the arrangement

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this night turned out to be Europa on

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the east and Ganymede I oh and Callisto

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on the west on january fifteenth all

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four stars were seen on one side of the

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planet

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everyone who aims a modest telescope or

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even binoculars that Jupiter will see

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the same view that Galileo did the views

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of tiny moons orbiting the king of the

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planets will surprise and delight all

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who look up Jupiter is hard to see in

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the evening sky this month but northern

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hemisphere observers may see Jupiter and

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Venus close together low on the south

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western horizon on Valentine's Day then

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it would be a few months wait until

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Jupiter becomes visible in the morning

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sky by August you can once again view

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Jupiter and the four Galilean moons

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after dinner or as soon as the Sun sets

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and the stars come out NASA's Galileo

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mission which ended in 2003 changed the

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way we look at our solar system it found

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evidence of subsurface salt water on

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Europa Ganymede and Callisto an intense

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volcanic activity on Io NASA's Juno

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mission will launch in 2011 on a mission

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to study Jupiter and the Europa Jupiter

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system mission a joint mission of the

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european space agency and nasa is slated

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to launch in 2020 it will primarily

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study Jupiter's moons Europa and

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Ganymede and Jupiter's magnetosphere you

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can learn all about NASA's missions at