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Many of us thought it was nearly impossible to catch Charon (Pluto's moon) from a backyard telescope, but Antonello Medugno did it! There are two handicaps to get such a picture. First of all, faint brightness of both objects, and secondly the small apparent distance between them, just 0.7 arcseconds.

Recently Hubble telescope discovered that dwarf planet Pluto also has two additional moons: Nix and Hydra. These are much fainter than Charon, so they are unobservable in this picture.

2015-10-18 15:34:02       
Scott:To remove Pluto as a pleant would be a victory for the proponents ofnihilistic deconstructionism.No, I wouldn't say that at all. I, like everyone else here, grew up learning that there were nine pleants in our solar system. However, as an unsentimental, hard-nosed realist, I have maintained for several years that either Pluto should be "demoted" and considered the largest comet, or else Ceres should be "promoted" to a pleant instead of being considered the largest asteroid.Ceres was discovered in 1801, and for a brief moment was thought to be a tiny pleant orbiting between Mars and Jupiter. But by 1807, three additional objects were found orbiting in the same region, which complicated matters. So a new category, "asteroid" was created to describe them. More and more of them were discovered as the years passed. I have a high school astronomy textbook from around 1880 which lists and names about 150 known asteroids. (I won't even go into the mathematics used in that textbook, which would no doubt ruin the self-esteem of modern high school students.)All those early asteroids were discovered visually, by looking through a telescope, without the benefit of photography. Astrophotography didn't really come into its own until the 20th century.In 1930 Clyde Tombaugh discovered Pluto after several years of arduous work comparing photographs of the same area of sky taken on different nights, and looking for the "star" that moved. He was deliberately searching for a pleant because calculations of the motions of Uranus and Neptune suggested that there must be another pleant further out that was gravitationally affecting them. Although Pluto was hailed as the "ninth pleant", it quickly became apparent that it was too small to account for the gravitational effects. (No large pleant has yet been found, so it's possible that the positional measurements of Uranus and Neptune were in error.)For more than 50 years Pluto was the only object known in the region beyond Neptune. But around 1990 another was found, then another, and then the floodgates opened. I don't know what the current count is, but it's at least in the hundreds, if not thousands. This collection of objects is now known as the "Kuiper bBelt" for the 1950's astronomer who predicted its existence. It could also be called the "comet belt".So in my opinion Pluto bears the same relation to the Kuiper belt as Ceres does to the asteroid belt. Both are simply the largest members of their class of objects.Then along came 2003 UB313, which may be larger then Pluto and further complicates matters. I have read that some astronomers think that even larger Kuiper belt objects may yet be discovered, perhaps as large as Mars.Therefore I think it's best that we think of the solar system as consisting of eight pleants plus a myriad of asteroids and comets. Otherwise we get into arbitrary definitions of pleants based on size. Really, everything orbiting the sun could be called a "pleant", just as the billions of particles comprising Saturn's rings could be called "moons".But no matter what we call Pluto, the mere nomenclature doesn't detract from discoverer Clyde Tombaugh's work in the least. It was still a tremendous feat of observation and perseverance. And I am equally in awe of the 19th century asteroid discoverers, who did their work without the benefit of photography.
2012-10-07 22:28:52       
Obviously, many people, eliacpelsy planetary scientists, do care whether Pluto is called a planet and about the larger issue of planet definition. Those of us who adhere to the geophysical planet definition DO view Ceres as a planet. Its demotion was wrong, but we can excuse 19th century astronomers because their telescopes weren't powerful enough to resole Ceres into a disk. Today, we know it is spherical, probably geologically differentiated, and may even have a subsurface ocean that could harbor microbial life. That makes it a small planet.Whether or not the IAU is "the organization that decides such matters" is completely a matter of consensus. That consensus has been seriously eroded in the last few years. If enough people, eliacpelsy astronomers, reject the IAU definitions, then they become irrelevant. Besides, science is not decided by decrees from a central group of elders whose word becomes gospel truth. That's religion, and appealing to authority is a logical fallacy. No one voted on whether the universe is made up of one or many galaxies. Time and data gave us the answer. The IAU can vote the sky is green; that does not make it true.Significantly, the IAU violated its own bylaws by putting a resolution on the floor of the General Assembly without first vetting it by the proper committee, as its bylaws require.I for one don't believe everyone is anti-American. However, these comments were made and were done so at the General Assembly, not over beer at a pub. The atmosphere was very hostile and polarized; this was reported at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD by astronomers who had actually been present at the General Assembly.If you think science never gets political, just look back at the controversy over the discovery of Neptune.Both dynamicists and geophysicists tend to be insistent. Personally, I have no problem with having two ways of looking at the solar system. That itself teaches a valuable lesson. And we aren't arguing about the decision "afterward" unless you give that 2006 vote some special sanctity. The debate over Pluto's status began in 1930 immediately after its discovery, as Clyde Tombaugh discusses in his book "Out of the Darkness: The Planet Pluto." I expect the debate over how to define the term planet to go on for quite a while, given the many strange exoplanets we're discovering. And I don't see anyone's life's work being ruined, given this discussion has gone on for more than 80 years.And I could not disgree with you more about public perception. You underestimate the intelligence and capability of the public. People have no trouble understanding that the number of known exoplanets is in constant flux. My nephew understood at four that there are two ways of defining what a planet is. Things do not have to be in a simple, memorizable order like a nursery rhyme. Alan Boyle suggests starting by describing our solar system as having four plus four plus more planets, as in four terrestrials, four jovians, and many more dwarf planets. I think that is an ideal way to introduce kids and adults to the solar system.
2011-08-19 06:07:06       
Thanks guys, I just about lost it loikong for this.
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