Yes, you read that right. In honor of Pluto’s imminent debut on computer screens worldwide, I’ll award it planetary status for the next few months. After all, when the New Horizons spacecraft nearing Pluto now was launched in January 2006, the (in)famous demotion to dwarf planet had not yet occurred.
If you are an aficionado of rocket launches, you will note that the New Horizons booster rocket fairly leaped off the launch pad. In fact, this spacecraft left the Earth faster than any other in history, passing the moon’s orbit in nine hours and reaching its encounter with Jupiter in less than fourteen months.
The Jupiter fly-by not only redirected New Horizons’ trajectory, it sped the spacecraft up by “stealing” a little energy from the massive planet in what is sometimes called a gravity assist maneuver. The mass differential between the spacecraft and the planet means that Jupiter will never miss that stolen energy. Without this maneuver, it would have taken even longer to reach this outer region of our solar system.
So why was every third-grader’s favorite planet demoted, anyway? Rather than the last planetary outpost, Pluto is better regarded as the threshold of a different region, the Kuiper Belt. These are icy remnants of the primordial solar system, so distant and small that their very existence was not confirmed until 1992. As more and more of them were discovered, the realization dawned that Pluto was just the nearest and one of the largest of these objects. Their remoteness makes knowledge of their detailed nature not much beyond speculation. But Pluto is about to help us better understand what they are about. As unaltered specimens dating to the very earliest days of the solar system, they should help us better understand how it evolved over its 4.5 billion year history.
Closest approach to Pluto is at 7:50 am EDT on Tuesday, July 14th. It will take some time to transmit all the data collected back to Earth. Pluto is so distant that it takes the radio signal four and a half hours to reach us. The spacecraft will be busy as it whizzes by at almost nine miles a second.
The time given are UTC (Universal Coordinated Time) on July 14th; Eastern Daylight Time is four hours earlier.
And finally, here are the latest (as of July 2nd) pictures of Pluto and its largest moon Charon, each showing a different hemisphere of Pluto. These will quickly be outdated as an entire new world is unveiled for the first time in all human history.