The interstellar neighbourhood: "The solar system moves through a local galactic cloud at a speed of 50,000 miles per hour, creating an interstellar wind of particles, some of which can travel all the way toward Earth to provide information about our neighborhood." Image Source:Adler/U. Chicago/Wesleyan/NASA (Hat tip: Emily Lakdawalla).
NASA reconfirmed today that Voyager 1 left our solar system and entered interstellar space. From The Atlantic:
The spacecraft sent back the following sound recording: "This is the sound of an explosion on our sun, [after it] traveled 12 billion miles, and [was heard by Voyager 1] ... in interstellar space."
Thirty-six years ago, from the ground in Florida, Voyager 1 launched into space. It traveled out of Earth's atmosphere, and it kept going. It passed Jupiter in 1979 and then Saturn in 1980. And then it kept going. ...
And today, in a historic announcement, NASA revealed that this piece of machinery, built by humans here on our planet, has officially sailed beyond the region of solar winds around our sun and into interstellar space.
The transition happened a year ago, around August 25, 2012, but scientists didn't realize it until recently, when they analyzed the vibrations made by an explosion on the sun in March of 2012, which arrived at the spacecraft in April 2013. As NASA explains, "The pitch of the oscillations helped scientists determine the density of the plasma. The particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere. Density of this sort is to be expected in interstellar space."
See my earlier posts on the Voyager spacecraft: here, here and here.