There was a time when Pluto - which NASA's New Horizons spacecraft at last explored in 2015, a mission I led - was considered the last planet. We now know there are thousands of other - possibly inhabited - planets.
Alan Stern
Just because Pluto orbits with many other dwarf planets doesn't change what it is, just as whether an object is a mountain or not doesn't depend on whether it's in a group or in isolation.
It's interesting - Pluto's almost a brand unto itself. It's the farthest. It's the most diminutive of the classical planets. It's been maligned by astronomers. It's always the one with all the question marks in the back of the textbook in the table. I think children identify with it because it's smaller, kind of cute.
New Horizons isn't just visiting Pluto; it's visiting this entire region. Whatever it finds, this will be a signal moment for planetary exploration - the capstone to our first reconnaissance of the planets of our solar system.
One of the implications of the discovery of the Kuiper Belt and its many small planets is that many scientists now think of the solar system as having not two but three zones.
Back before the Kuiper Belt was discovered, Pluto did look like a misfit that didn't belong with either the terrestrials or the giant planets.
Pluto is still active four and a half billion years into its history. It was expected that small planets like Pluto would cool off long ago and not still be showing geological activity. Pluto is, in fact, showing numerous examples of geological activity on a massive scale across the planet.
The Kuiper belt region, which I call the third zone because it lies beyond the rocky terrestrial planets and beyond the giant planets, is a bizarre frontier.
There are lots of really interesting little planets out there in the Kuiper Belt, but Pluto's the only one that's got all the cool attributes.
Pluto and its brethren are the most populous class of planets in our solar system.
Discovering that our solar system has many more planets than we ever expected, and that most of them are ice dwarfs rather than like Earth and the other rocky terrestrials, is just another step in the revolution in viewpoint that removed the Earth from the center of the physical universe and makes Earth all the more special.
I like the planets because they are real places that you can go to and send machines to. Faraway astronomy - galactic astronomy and extra-galactic astronomy - is really cool stuff, but to me, it's about destinations.
In the mind of the public, the word 'planet' carries a significance lacking in other words used to describe planetary bodies... many members of the public assume that alleged 'non-planets' cease to be interesting enough to warrant scientific exploration.
I used to be a strong believer that we would eventually colonize the solar system the way it's been done in science fiction many, many times: bases on the moon, Mars colonized, move out to the outer planets, then we go to the next solar system and build a colony there. I don't know now - I'm not as convinced that's the way it's going to pan out.
Alastair Reynolds
Unaware of the absurdity of it, we introduce our own petty household rules into the economy of the universe for which the life of generations, peoples, of entire planets, has no importance in relation to the general development.
Alexander Herzen
The key to proving that there's a black hole is showing that there's a tremendous amount of mass in a very small volume. And you can do that with the motions of stars. The way the star moves around the center of the galaxy is very much like the way the planets orbit the sun.
Andrea M. Ghez
For a long time, we've worked on detecting planets with whatever was at hand, making use of existing small telescopes or even amateur telescopes. It's time to move on to the next stage.
Andrew Gould
In the future we're going to have interplanetary, we're going to have two planets that human beings are living on.
Anne McClain
This time, instead of moving oceans and healing planets, let's get our bills in order and pay down the debt so we control our own future.
Artur Davis
I won't say that I'm an agnostic, since agnosticism maintains that one cannot know... but I'm not averse to the idea of some intelligence or some organizing force that set up the initial conditions of the universe in such a way that ultimately generated stars, planets and life.
B. F. Skinner
We are using resources as if we had two planets, not one. There can be no 'plan B' because there is no 'planet B.'
There's a lot of cruelty going on all the time, and I'm not just talking about inter-human cruelty. I'm talking about whole species becoming extinct, asteroids hitting planets, black holes gobbling up stars.
The sun and its retinue of planets drift as a group through the vast gulfs of space that separate the stars.
Good men are the stars, the planets of the ages wherein they live, and illustrate the times.
Wonder if there is life on another planet? Let's suppose there is. Suppose further, that only one star in a trillion has a planet that could support life. If that were the case, then there would be at least 100 million planets that harbored life.
Two nations between whom there is no intercourse and no sympathy; who are as ignorant of each other's habits, thoughts, and feelings, as if they were dwellers in different zones, or inhabitants of different planets. The rich and the poor.
Saturn Return is just the return of your planets to their original position.
Nature hasn't gone anywhere. It is all around us, all the planets, galaxies and so on. We are nothing in comparison.
I have marvelous dreams! I meet Buddha, I meet Jesus, I meet Mohammed. I constantly dream of space, stars and planets: we are the children of stardust.
I'm an atheist, and the concept of god for me is all part of what I call 'the last illusion.' The last illusion is someone knows what is going on. Nearly everyone has that illusion somewhere, and it manifests not only in the terms of the idea that there is a god but that it knows what's going on but that the planets know what's going on.
Many different planets are many different distances from their host star; we find ourselves at this distance because if we were closer or farther away, the temperature would be hotter or colder, eliminating liquid water, an essential ingredient for our survival.
I believe there's life on other planets, but I don't believe that UFOs are saucers from another world.
By 1973, we had a space station, the Skylab, and we had multiple probes going up to planets. So, all this wonderful stuff happened in 10 to 15 years. About that time, there should have been enormous initiatives to make it affordable for people to fly in space, not just a handful of trained NASA astronauts and Russian cosmonauts.
When I was a little kid, we only knew about our nine planets. Since then, we've downgraded Pluto but have discovered that other solar systems and stars are common. So life is probably quite prevalent.
To an observer situated on the moon or on one of the planets, the most noticeable feature on the surface of our globe would no doubt be the large areas covered by oceanic water. The sunlit face of the earth would appear to shine by the light diffused back into space from the land and water-covered areas.
It's like there's a pulsating, hidden world, governed by ancient laws and principles, underlying everything around us - from the movements of electrical charges to the motions of the planets - and most people are completely unaware of it. To me, that's a shame.
I read about eastern philosophy and religion and existentialism. All that introspective thinking got me thinking about the great beyond. That turned my sights from inwards to outwards, and I started becoming interested in the makeup of the universe, and I started reading about astronomy, planets, and galaxies.
Every type of ring behavior we have seen around Jupiter, Uranus, or Neptune can be found in orbit around Saturn. And Saturn's ring system offers the greatest promise of understanding processes in operation within all disk systems, not just those found around planets.
No matter how you measure it, whether you measure the amount of mass or you measure the number of bodies, most of our solar system exists out beyond the orbits of the asteroids. So we could not have claimed to know our own solar system until Voyager had toured the giant planets.
Our solar system is actually a wild frontier, teeming with different, diverse places: planets and moons, millions of objects of ice and rock.
We can allow satellites, planets, suns, universe, nay whole systems of universes, to be governed by laws, but the smallest insect, we wish to be created at once by special act.
I want to prove that Holst's 'The Planets' can be as much of a sensory overload as a concert by the Grateful Dead, and just as exciting.
Life can be less mysterious than we make it out to be when we try to think about how it would be on other planets. And if we remove the mystery of life, then I think it is a little bit easier for us to think about how we live, and how perhaps we're not as special as we always think we are.
The world, when you look at it, it just can't be random. I mean, it's so different than the vast emptiness that is everything else, and even all the other planets we've seen, at least in our solar system, none of them even remotely resemble the precious life-giving nature of our own planet.
A time will come when men will stretch out their eyes. They should see planets like our Earth.
When I talk of the purpose of life, I am thinking not only of human life, but of all life on Earth and of the life which must exist upon other planets throughout the universe.
I used to think about how nice it would be to visit the planets. Of course, I didn't expect to see in my lifetime what has happened. I knew it would happen some day, but it came along faster than I at first thought.
The planets are never the same twice, they're always different, so they could compare the markings I had drawn with their current photographs and they knew that I was drawing what I was really seeing and it wasn't copied from somewhere.
The day is not far off when we will be able to send a robotically controlled genome-sequencing unit in a probe to other planets to read the DNA sequence of any alien microbe life that may be there.
What if life is not carbon-based? Can life exist as a gas or a plasma? Could planets or stars in some sense be alive? What about an interstellar cloud? Could life exist on such a small or large scale, or move so fast or so slowly that we wouldn't recognize it? Could you have an intelligent virus?
