Published: 2015-07-28 15:12:00
Updated: 2015-07-28 18:35:29
Posted July 28, 2015
By Tony Rice
Pluto has been in the spotlight this month with incredible images revealing the surface and atmosphere of the dwarf planet. Since passing Pluto and its moons two weeks ago, New Horizons has traveled over ten million miles at a speed of 30,800 miles per hour.
New Horizons will continue on this path, with its communications array aligned to Earth, until at least this time next year. It will take that long to complete the transfer of more than 6 Gigabytes of images and other scientific data collected during the brief encounter with Pluto.
Even at top efficiency, with both of New Horizons’ transmitters sending data, and the spacecraft appearing high in the sky over the array of dishes which make up NASA’s Deep Space Network, the data rate is about half that of the 56 kilobyte modem many of you may remember. Most of the time, communications are at about one quarter of that speed.
Pluto may seem far away but you can still find its location in the sky this week.
While not visible to the naked eye or with anything but the largest of amateur telescopes, you can find Pluto this week with the moon as your guide. Wednesday night, look for the rising, nearly full moon. Hold 3 fingers up with your outstretched hand with the moon on the left. Pluto will be about 5 degrees to the right.
Pluto is, of course, not visible to use because so little light is reflected back from the sun. Astronomers measure that brightness using a logarithmic magnitude scale with lower numbers representing brighter objects. Our sun appears at -27, the next brightest star at -1.5 and those really bright ISS passes are routinely in the -3 to -4 range. Wednesday’s moon will shine brightly at a magnitude of about -12 while Pluto is nearly invisible at a magnitude of +14, or about 25 billion times dimmer. That difference is a big reason why astronomers, professional or amateur, don't do much observing during full moons.
It’s a long way from the sun to Pluto and back to the Earth, but a surprising amount of sunlight does make it there. You can see what high noon might look if you were standing on the surface of Pluto by going outside about 5 minutes after the official sunset time to experience “Pluto Time” seen at 8:27 p.m. on Tuesday and 8:26 p.m. on Wednesday.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.