A spacecraft is now in route to the dwarf planet Pluto, scheduled to arrive in the year 2015. Tonight’s moon can help you visualize this Pluto spacecraft’s whereabouts on the sky’s dome.
We’re talking about the New Horizons spacecraft, launched from Earth in 2006. Will you see the spacecraft itself tonight? No. Even with a high-powered telescope, this little craft cannot be seen from Earth now as it speeds toward the outer solar system. You’d have a better chance of spotting Pluto, in fact (which can’t be seen either, from Earth, with the eye alone). Pluto is some 1,500 times fainter than the faintest star visible to the unaided eye, but Pluto outshines the New Horizons spacecraft by billions of times.
We label the star cluster M25 on the feature chart, because it’s about 1.5o from the dwarf planet Pluto on the sky’s dome. The width of your little finger at an arm’s length measures the approximate angular distance between M25 and Pluto. You can actually see this cluster with the unaided eye on a dark, moonless night. As seen from North America at nightfall, Pluto is just south of tonight’s moon. The dwarf planet Pluto lodges in between M25 and New Horizons on the sky’s dome.
So what are we suggesting here? Nothing more than stretching your imagination to visualize a spacecraft speeding along in outer space. Tonight’s waxing gibbous moon, Pluto and the New Horizons spacecraft occupy nearly the same spot on the sky’s dome. Of course, the three are not close together in space. The moon lies about 229,000 miles from Earth tonight, and Pluto lies about 13,000 times the moon’s distance from Earth while the New Horizon spacecraft is heading for Pluto, at about 11,000 times the moon’s distance from Earth.
First, look at our chart. See the empty spot next to the words New Horizon? That spot marks the site of the spacecraft on tonight’s sky dome. If you look at tonight’s moon, you’ll be looking in the general direction. We’ve also drawn in the Teapot star formation in the western half of the constellation Sagittarius to help you find the spacecraft’s location in our sky. These stars in Sagittarius might or might not be visible in the moonlit glare tonight, but they are helpful for envisioning the general location of Pluto, or New Horizons, in front of the constellation Sagittarius. The New Horizons spacecraft and Pluto will remain in front of Sagittarius until New Horizons finally meets up with Pluto in July 2015. So if you can spot these stars, you can gaze at them for several years while contemplating New Horizons’ long journey.
Where is New Horizons now in space? The image below shows the craft’s whereabouts from another perspective – looking down on the solar system – as it is today, September 13, 2013.
At present, New Horizons resides about 27 times the Earth’s distance from the sun. Pluto lies at about 32 times the Earth/sun distance. The spacecraft travels about 3.4 times the Earth/sun distance closer to Pluto yearly.
Now flip your perspective again, and go back to the chart at the top of this page. It’s tough to flip perspectives like this. But it’s fun to try.
And, most of all, go outside tonight – September 13, 2013 – and gaze toward the moon. Let tonight’s moon guide you in your imagination to Pluto-bound New Horizons’ place in the starry sky.