by jjohnson » Thu Mar 31, 2011 2:22 pm
On March 18th this small but fast spacecraft passed the orbital path of Uranus, which was a quarter of the way farther around the Sun and thus nowhere near in sight. Launched in January, 2006, in 1,844 days it ticked off 1.8 billion (1.8x10^9) miles, nearly 20 AUs, averaging about 976,139 miles or 1,309,122 km per day. 829 Earth diameters every day. 15 km/s. As the NASA site says, it has covered a serious amount of space. Pluto will be reached in 2015.
Perspectives Section
So, how about our chances of travelling to the nearest star system away from us? 1 star away, in our galaxy of somewhere between 100 billion and 200 billion stars (all the rest of which are farther away, of course). How far is it to Alpha Centauri AB (they are a binary pair)? 4.37 light years (ly). Pretty close, on the galactic scale. Next door.
Let's say we could accelerate to the New Horizon's speed, and coast at that velocity all the way to Alpha Cen. We have the information at hand. Distance d = 4.37 ly. 1 ly = 5.8785x10^12 miles. Speed v = 976,139 mi/day.
speed times time = distance, so time = distance ÷ speed: t (days) = (4.37 ly x 5.8785x10^12) ÷ 9.76139 x 10^5
t = (2.5689 x 10^13) ÷ (9.76.. x 10^5) = 27,316995 ...days. Divide that by 365.25 days per year:
t = 72,052 years to our nearest neighboring star. Easy exercise. Daunting answer.
So next time Michio Kaku talks about "if we could send a probe to send back pictures of the black hole" that he tells us lurks at the center of our Galaxy, snacking on stars, think that it is 25,000 to 30,000 light years there, from here, and it would take a large multiple of that figure, in years, to get there by any known means, and an additional 25 to 30 thousand years to radio those JPEGs back.
"Yep," they'll say, "these here pictures definitely show that the event horizon around the black hole is smaller than the resolution of this probe's camera, and we need to get a grant to fund a more sensitive camera on the next one!"