Question 17 : Space exploration today - Episode 1

Hey buddies !

Today, after a long period of silence, we are to talk about … space exploration !

First, we have to underline that I am to talk about space exploration, and not about space conquest ! You could find it idiot, but it is important. Most of astrophysicists cannot accept that ones use the word "conquest", which is mostly connoted with violence, whereas scientist explore, they never destroy neither conquer.

How can you read this tab ? In columns, you can find, from left to right : Mercure, Venus, the Moon, Mars, Jupiter, Saturne, Uranus and Neptune. In lines, phases of the space exploration with, from up to bottom : Observations from the ground, Fly-by, Orbit probes, Landers and/or Rovers, Human exploration. And what about the images ? They indicates that this object has been explored by the exploration phases in the line. We will come back to this later, but now let's begin with …

Episode 1 : Observations from the ground

What we can see in this tab is that all objects listed have been observed from the ground.

One can just go out during the night to see why the Moon has always been observed. As the nearest object from us, it is particularly visible from the ground, except during New Moon nights !

There is 5 planets that can be observed with naked-eyes :

• Mercure has been observed since the Antiquity. The first evidence we have about these observations are from the Sumerian, in the 3^rd millenary BC. As it is really close to the Sun, Mercure is however really difficult to observe.
• As the 3^rd most brilliant object of the sky, Venus has always been observed. It is because of its particular brilliance that it was nicknamed "Berger Star", as you already know (if not, come back in few days, I'll write an article about it soon !)
• Mars has been known since the Antiquity now, Egyptians in particular, who understood its retrograde movement (cf later article) !
• Jupiter has been known from millenaries too, because, and you already know it if you have observed Jupiter by night, it is really well visible by night. Galileo has observed Jupiter a lot, and discovered its 4 biggest satellites : Io, Ganymede, Europe and Callisto.
• The last planets visible with naked-eyes is Saturne, of course. Its rings has been observed by Galileo, who did not understand what they could be. The one who discovered it again, and understood their nature is Huygens in 1656.

About the others planets :

• Uranus has been observer during history, but it was never considered has a planet. Its official discovery by Sir William Herschel was in 1781, with a telescope.
• Neptune is not visible with naked-eyes neither, and was seen for the first time in a telescope, in 1612. The particularity of this planet is that it was discovered by calculations (cf later article), around the trajectory of Uranus. Observations were only made to confirm this prediction.

And let's finish with Pluto, which is not a planet I repeat :

Pluto has been observed for the first time in 1930, and was predicted because of the weird trajectory of Neptune.

It is how I finish our first episode of the space exploration serie. Let's come back for the next article about fly-bys =D ! See you soon !!