Astronomie - Pluto ein Planet oder Zwergplanet?



Panel: Pluto a planet
WASHINGTON – Tucson scientist David Grinspoon joined a panel recently talking about NASA’s New Horizons mission to Pluto – but the scientists were most animated when talking about the feud over the status of the recently classified “dwarf planet.”
Long sought by Flagstaff’s Lowell Observatory as Planet X, and classified as the solar system’s ninth planet in 1930, Pluto took a hit in 2006 when it was downgraded to the new category, upsetting Pluto’s defenders.
“Dwarf people are people. Dwarf planets are planets,” said Fran Bagenal, a panelist and University of Colorado astrophysicist, when asked about Pluto’s current status.
Panelists – NASA officials, academics and contractors overseeing the New Horizons mission – were unanimous in their support of the position that the littlest planet should still be called a planet, without qualifiers.
Grinspoon, an astrophysicist with the nonprofit Planetary Science Institute in Tucson, moderated the panel that veered from the value of space exploration to the defense of Pluto to a discussion on Twitter with William Shatner – the actor who played Capt. Kirk in the original “Star Trek” TV series, who happens to be a science-fiction enthusiast.
It was Shatner who prompted the Pluto discussion, with a tweet to NASA about its planetary status. Panelist Jeff Moore, a planetary scientist from NASA’s Space Science Division, obliged Shatner by asking, if Capt. Kirk saw Pluto, would he tell Spock to land, or to keep flying?
Pluto’s status was called in to question after the discovery of Eris, a satellite in the solar system that is 28 percent larger than Pluto. When Eris was classified as a dwarf planet by the International Astronomical Union in 2006, Pluto was also put in the minor leagues.
New Horizons was launched on Jan. 19, 2006 – seven months before Pluto would be reclassified as a dwarf planet. The probe, roughly the size of a piano, has since taken flyby pictures of any planets, moons or asteroids it has come across on its journey to the edge of our solar system.
It reached Neptune on Monday, exactly 25 years after another space probe, Voyager 2, sent back the very first images of that planet, the eighth in the solar system. Voyager 2 continued past Pluto and got some images with its 0.64-megapixel camera, but New Horizons will travel four times closer with a 25-megapixel camera.
New Horizons is expected to begin its flyby of Pluto on July 14, 2015, where officials like Grinspoon hope it will provide exciting new information about Pluto, its moons and its status in the solar system.
“As far as deep-space exploration … that’s what NASA ought to be doing, pushing the envelope for a long-term societal investment,” he said.
Not only will the information be worth the investment of about $70 million, it will also be worth the wait, panelists said.
By the time New Horizons begins its main mission, it will have been almost a decade since its launch and panelists are eager to see what comes back from Pluto. Grinspoon reminded the audience that working on space probes can be a very long-term project, but that the longer it takes between discoveries, the greater the anticipation for that information.
And in keeping with the eclectic theme of the day, he cited rapper Eminem to make his point.
“As a famous rapper said, ‘You only get one shot,’” Grinspoon said.
Quelle: azdailysun
Rückblick Mai 2011:
Planet Pluto ist Vergangenheit
Die Internationale Astronomische Union hat bei einer Tagung in Pragentschieden, dass der Himmelskörper Pluto kein Planet mehr ist. Damit besteht unser Sonnensystem wieder aus acht Planeten. US-Wissenschaftler hatten bis zu letzt vergeblich versucht, den Planetenstatus des 1930 entdeckten Himmelskörpers beizubehalten.  Da es zuviele, demPluto ähnelnde Himmelskörper gibt, die teilweise sogar dessen Größe übersteigen, entschieden die Astronomen auf ihrer Tagung den "Neunten Planeten" seines Status zuentheben. Einer dieser größeren Zwergplaneten heisst Xena und befindet sich noch weiter entfernt als Pluto. Statt nun Xena ebenfalls zu einem Planeten zu erklären, setzten sie Pluto auf dieselbe Stufe herab - zu einem Zwergplaneten. Damit es künftig keine Diskussionen um den den Planetenstatus gibt, haben die Astronomen nun drei verschiedene Definitionen von Himmelskörperngeschaffen. Sie werden nun in Planeten, Zwergplaneten und Kleinkörpern kategorisiert. Ein Planet wird nun wie folgt definiert: "Ein Körper, der durch eigene Schwerkraft rund ist und der seine Sternenbahn freigeräumt hat." Für Zwergplaneten heißt es nun: "Ein Himmelskörper, der ebenfalls rund ist durch seine Schwerkraft, der aber seine Bahn nicht freigeräumt hat." Kleinkörper haben folgende Definition: "Kleinere Objekte, die um die Sonne kreisen, aber nicht rund sind."
Update: 6.10.2014
Harvard Astrophysiker upgraden Pluto zurück zur Planeten-Größe!
Eight years ago it was relegated to dwarf planet status. But Harvard astrophysicists are arguing that being small shouldn’t disqualify it
Age: 4.6bn years old.
Appearance: Slightly different to its appearance last week.
You know, I thought that too. Has it had its hair done? No, not that, you idiot. Between you and me I think it might look a little more, well ... planet-y than usual.
Surely that can’t be the case. We’ve been through this before, remember? I know, I know. Pluto had been a planet since its discovery in 1930, only to be unceremoniously relegated to dwarf planet status by the International Astronomical Union in 2006. And yet ...
And yet what? And yet the Harvard-Smithsonian Centre for Astrophysicists is lobbying hard for Pluto to become a planet again.
Why? We’ve just had all the textbooks reprinted. It’s all about the definition. According to the Harvard-Smithsonian news blog, even if Pluto is a dwarf planet, we should still treat it as a planet because: “A dwarf fruit tree is still a small fruit tree, and a dwarf hamster is still a small hamster.” The centre had a debate, and then there was a vote, and the result was overwhelmingly in favour of Pluto’s reinstatement as a planet.
What happens if we do let Pluto back in? Well, there’s a chance that other distant trans-Neptunian objects – such as Triton or Eris or 50000 Quaoar or 90377 Sedna – could also qualify for official planetary status.
But this is madness! The floodgates will open! We’ll never be able to turn back the tide of shifty-looking would-be planets looking to get an unjustified cut of our solar system! All right, Farage, rein it in.
Fine. But does any of this actually matter? If you’re a member of the International Astronomical Union or the Harvard-Smithsonian Centre for Astrophysicists – basically the Sharks and the Jets of the planetary-definition game – then yes.
And what does Pluto make of all this? Pluto is a massive clump of rock and ice trapped in a lonely silent orbit through the dark recesses of space several billion miles away from Earth. As such, it could not be reached for comment.
Do say: “Welcome back to the solar system, Pluto. We’ve missed you.”
Don’t say: “Now get out. We’ve changed our minds again.”
Quelle: theguardian