|Pluto's surface -- seen from New Horizons|
NASA's New Horizons probe successfully completed a flyby above dwarf planet Pluto in July, after a meandering 9-year, 3-billion-mile journey across our Solar System - - a first for humankind. Before 2015 we only know Pluto from a blurry picture of the dwarf planet taken by the Hubble Space Telescope, but now we have a full topographical map in high resolution. This is a huge step forward for science.
|Pluto -- as seen by the Hubble Space Telescope (2010)|
|Pluto -- as seen from New Horizons (2015)|
Why so difficult to see Pluto even with the huge, $2bn scope? Well first, it's really tiny. To understand how small Pluto is, check out the illustration below of the Solar System objects drawn to scale (but not to distance). The Sun is the big glowing yellow ball in the background, obviously. Earth is the third ball at the bottom left, followed by the moon, Venus, and gas giants Jupiter, Saturn, Neptune, and Uranus. Pluto is one the last 4 tiny dots on the right, along with some other Kuiper Belt Objects.
And Pluto is also far: its orbit is 30 times the distance from the Earth to the Sun.
Makes you think about how huge (and empty) the outer space is. You see, New Horizons is speeding at ~40,000 mph away from the Sun, one of the fastest man-made objects in space. Proxima Centauri, the closest star in our Milky Way galaxy, is 4 light years away. If we send a spaceship going at the same (constant) speed as New Horizons, it would take 60,000 years to reach Proxima Centauri (don't forget, thanks to the Sun's gravitational pull, the ship would continuously slow down unless it expends a lot of energy). And that's just the closest star in our own galaxy.