The New Horizons spacecraft passed Pluto on Tuesday, according to NASA, establishing that mankind — or at least one of its robot probes — has now visited the far reaches of our planetary system.
“It’s not just a dot now. It’s a real world,” said David Dundee, astronomer at the Tellus Science Museum in Cartersville.
Tellus was marking the event with a special Tuesday evening. With some luck and good weather, Dundee hoped to show visitors a view of Pluto through the museum’s 20-inch reflector telescope, as well as some of the first close-up images transmitted Tuesday from the NASA spacecraft.
“People will be able to put their eye up to the telescope and see a very tiny dot,” Dundee said. It was the first time, and perhaps the only, that Tellus planned to make Pluto the focus of a public viewing, he said, because it is so small and faint.
A tiny dot is about all astronomers with even the largest telescopes could see of Pluto until New Horizons arrived in the area.
The moment of closest approach for the spacecraft came around 7:49 a.m. Tuesday, culminating an epic journey from Earth that spanned more than 3 billion miles and 9½ years.
“This is truly a hallmark in human history,” said John Grunsfeld, NASA’s science mission chief. “It’s been an incredible voyage.”
The event captured a fair share of public imagination, judging by Facebook posts and Google’s use of a flyby graphic on its home page.
In a cosmic coincidence, the encounter occurred 50 years to the day after Mariner 4’s flyby of Mars, which yielded the first close-up pictures of the red planet.
“I think it’s fitting that on the 50th anniversary we complete the initial reconnaissance of the planets with the exploration of Pluto,” said the mission’s principal scientist, Alan Stern.
With the $720 million mission, the United States is now the only nation to visit every planet in the solar system.
Pluto’s status changed during the trip. It was No. 9 in the planetary lineup when New Horizons departed Cape Canaveral, Florida, on Jan. 19, 2006, but was demoted seven months later to “dwarf plant” status.
NASA believed New Horizons was pretty much straight on course for the historic encounter, sweeping within 7,700 miles of Pluto at 31,000 mph. It actually happened 72 seconds earlier and about 40 miles closer than anticipated.
NASA didn’t expect until late Tuesday to know for sure, after the spacecraft interrupted its flyby reconnaissance long enough to radio a message back to Earth, that New Horizons was OK. That message would take 4 1/2 hours to cross the 3 billion miles of space at the speed of light.
It will take more than a year, NASA says, before the spacecraft delivers all of the photos and data it has collected during its swoop through the dwarf planet’s complex binary system, which includes Pluto, a large moon Charon, and at least four smaller moons. All were expected to come under New Horizons’ scrutiny.
New Horizons already has beamed back the best-ever images of Pluto and Charon, uncovering some early surprises. Pluto is bigger, more complex and more colorful than many expected, with big dark patches and a large, tan, heart-shaped region covering much of one hemisphere.
“I was not expecting that,” said Rob Parks, a Georgia State University astronomer. “It looks very much like one of the moons of Jupiter.”
Parks is a recently-minted Ph.D who is studying stellar magnetic fields and the disks of dust and gas around other stars that might someday collapse into planets. But he said he couldn’t resist taking a peek several years ago at Pluto using Emory University’s 24-inch telescope.
“It’s really just a dot,” he said.
It will take more than a year to get back all the data from the flyby — 16 full months, or until October or November 2016.
On the eve of the flyby, NASA announced that Pluto is actually bigger than anyone imagined, thanks to measurements made by the spacecraft, a baby grand piano-size affair. It’s about 50 miles bigger, for a grand total of 1,473 miles in diameter. But that’s still puny by solar-system standards: Pluto is just two-thirds the size of Earth’s moon.
The Associated Press contributed to this article.
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