Approximately 2,600 years ago, the Greeks, like many humans before them looked up at the night sky and saw dots of light that kept moving from day to day and month to month. They called them 'aster planetes' or wandering stars. In 1610, Galileo Galilei pointed his telescope towards one of these wanderers, which the Romans had dubbed Jupiter after their main God, and discovered the largest 4 of its 67 moons.

This largest planet in our Solar System has fascinated humanity for a long time. And in 1989 NASA launched its Galileo spacecraft to study it and its moons. Galileo's mission was terminated in 2003 by sending it into the planet's atmosphere.

This illustration depicts NASA's Juno spacecraft successfully entering Jupiter's orbit (Photo: NASA)

Another spacecraft - Juno - left Earth in 2011 and yesterday, July 4 2016, after 5 years of traveling 1.74 billion miles (2.7 billion km), it entered into orbit around Jupiter. Because it had to travel through Jupiter's massive magnetosphere and debris field, the orbital insertion was full of trepidation. All of its instrument had to shut down and it had to technically "fly blind". Subsequently, it had to fire a rocket engine to slow its approach to the planet and get caught by its gravity i.e enter into engine burn, without which it would have shot past Jupiter. At this point it cartwheeled five times a minute, turned away from the sun and put on its brakes. Because Juno is totally solar powered, it then also had to turn around so that its solar panels faced the sun. All of this was achieved, information was received from the spacecraft after 48 minutes of nail biting wait and NASA JPL mission control announced:

"Roger Juno, welcome to Jupiter".

The main objective of the Juno mission is to study the formation and evolution of the planet and gain an understanding of our Solar System. The observations will also help scientists understand other planetary systems.

Juno team members celebrate after the spacecraft signaled a successful orbit insertion at Jupiter (Photo: NASA)

In addition to getting some awesome pictures, Juno will observe Jupiter's magnetosphere, measure water, gases and other elements in its atmosphere and study the very bright auroras at its poles, as well as its giant red spot. Jupiter's core is still a mystery because we do not know whether it is a solid or a gas and Juno will help us understand that as well.

As the mission's principle investigator, Scott Bolton said:

"By studying Jupiter, what you are really learning is the history of the elements that eventually made us".

After two days, Juno's instruments will come online and it will set off  on a 53 day orbit. It will now come close to Jupiter in August. At that time it will start sending back data about the environment around the planet. It will undertake approximately 37 orbits in the next 20 months, before the intense Jovian radiation breaks down its electronic and propulsion systems. The plan is to place Juno into a slowly degrading orbit, before the spacecraft fails completely, and plunge it into Jupiter. This is to ensure that it does not contaminate any of Jupiter's potentially life bearing moons, such as Europa. NASA's next mission is to this moon and is going to be launched in the 2020s.

View from NASA's Eyes on the Solar System (Photo: NASA)

Humans now have spacecraft orbiting Venus, Earth, the Moon, Mars, Ceres, Jupiter and Saturn. Mercury's orbiter, Messenger ended its operations in 2015, when it slammed into Mercury's surface. By this time it had obtained a lot of data for scientists to analyze.

The data that we will get from Juno will be new and extremely fascinating. It will help us understand how our Solar System came into being. I have said this before and I say it again: What a great time to be alive!