Re: Nasa's Voyager 2 probe 'leaves the Solar System'
Good questions OGF! The reality is that we are not only interested in what our house (the solar system) looks like, but what the conditions look like once we go through the front door (heliosphere).
So far, the outer reaches of the atmosphere behave (solar wind drops below the speed of sound) and not the empty vacuum once thought, other interesting intergalactic conditions exist. Since one of the instruments stopped working in Voyager 1, Voyager 2 may be able to not only provide us some information about the conditions outside the solar system, it will give us a better idea of what’s going on beyond our little bubble.
This data is being used as a platform for an even bigger project about to be launched called IMAP that will help us better understand how the heliosphere works in protecting us from cosmic rays. That protection is one of the least understood and most important phenomena in our existence. We simply don’t know how the doors, windows, and roof protect us so well.
The use of RTGs to power objects in space is a favorite method for satellites and exploration craft because it is so simple and dependable. Besides using long lasting stable isotopes to produce heat (alpha particles given of in decay bounce around and create heat), RTGs contain no moving parts. They actually depend on the super cold environment in space that you mention to produce electricity.
As OMAH shared, the RTGSs are made up of thermocouples that employ the Seebeck Effect, which voltage is generated when two dissimilar conductive metals are in contact. One end of each thermocouple is placed next to a hot isotope and the other is connected to a heat sink in the cold of space. The temperature difference between the conductive material creates the needed electrical energy. The isotope decay in the RTGs will probably last up to a hundred years or so, but the electricity use to power the remaining three units is dropping at about 4 watts a year, which is why the others have been turned off one by one. The ones chosen to remain are the ones that indicate non-visible wavelengths.
Knowing who we are and why we are, are some of the big questions. Invariably, these kind of explorations also give us technology that is helpful in everyday living.
It's reaaaaaaalllly good stuff!
(Good grief I hope my wordy, nerdy style hasn't killed yet another thread. Carry on
).