The Outer Planets Vs The Inner Planets
The term “outer planets” refers to planets that orbit the Sun beyond the Asteroid Belt, including Jupiter, Saturn, Uranus, Neptune and Pluto. The inner planets are Mercury, Venus, Earth and Mars.
There are small, rocky inner planets giant, gas outer planets and dwarf planets, such as Pluto and Ceres. Pluto and its moon Charon have solid surfaces but, unlike the terrestrial planets, a significant portion of their mass is icy material .
Pluto and Charon are widely considered to be among the largest objects in the Kuiper Belt, a vast reservoir of icy objects located just outside of Neptune’s orbit and extending out to about 50 astronomical units from the Sun. The Kuiper Belt is thought to be the source of most short-period comets – those with orbits shorter than 200 years – so scientists really want to compare the composition and surface properties of Pluto and Charon to those of cometary nuclei.
The Changing Landscape Of The Solar System
The object Tombaugh had discovered was named Pluto, a name officially adopted by the American Astronomical Society, the Royal Astronomical Society in the UK and the IAU. It is a frigid world, billions of kilometres from Earth, and 30 times less massive than the then-smallest known planet, Mercury. But Pluto was not alone. It was found to have five satellites. The largest, Charon, was discovered in 1978. The smaller four were discovered using the Hubble Space Telescope in 2005, 2011 and 2012 and officially named Nix, Hydra, in early 2006 , Kerberos and Styx in 2013 by the IAU.
The view of our Solar System’s landscape began to change on August 30, 1992 with the discovery by David Jewitt and Jane Luu from the University of Hawaii of the first of more than 1000 now known objects orbiting beyond Neptune in what is often referred to as the transneptunian region. More generally these bodies are often simply labelled as Trans-Neptunian Objects .
A Mysterious Planet X Beyond Pluto In Our Solar System Check Awesome Truth
Until about the 18th century, we only knew about the existence of six planets in our solar system. Anything beyond Saturn was too far to be seen with the unaided eye or a basic telescope. Uranus was later discovered in 1781 and later in 1846 Neptune was also found. But there was one oddity in the discovery of Neptune. Unlike other planets, it wasn’t discovered through observation. Rather, scientists estimated that Neptune must exist based on mathematical calculations of its predicted position due to observed perturbations in the orbit of the planet Uranus. And today, the same math is pointing towards the existence of a 9th planet, far beyond the orbit of Pluto. So, what is this Planet X and what do we know about it? Does it even exist or is the maths wrong?
Don’t Miss: Do Solar Panels Work Without Electricity
Here’s Looking At You
The Moon is a familiar object in our night sky, and the Apollo astronauts’ photos have shown us what the Earth looks like from the Moon. What would Charon look like from Pluto, or Pluto from Charon? Charon is about half of Pluto’s size and located about 17 “Pluto radii” away. This means that the disk of Charon is about 3.5 degrees across when seen from Pluto, and Pluto is twice that size when seen from Charon.
This diagram shows one way to measure angles with your fingers. If you hold your arm out toward the sky, the width of a finger is about 1 degree. This means that from Pluto the disk of Charon is about 3 or 4 fingers across. Our Moon is about one-half of a degree across – the width of a skinny pinky finger. From Charon, the disk of Pluto is wider than an outstretched fist. Wouldn’t that be an amazing sight in the sky!
Geological Processes On Planetary Objects
The four main geological processes are impacts, volcanism, tectonics and erosion.
Impact craters: In the solar system’s formative years, when there was a lot of material left over from making planets, collisions were frequent and violent impacts frequently bombarded the surfaces of planetary objects. Craters produced by these impacts are readily visible on Earth’s Moon and other planetary objects. Observations of the Moon and dating of lunar rocks the Apollo astronauts brought back to Earth tells us the frequency of impacts seems to have dropped dramatically about 3.8 billion years ago. Measuring the density of craters on the surface of a planetary object allows scientists to estimate the surface’s age and when it was “resurfaced.”
Volcanism: When the interior of a planetary object is heated then material underneath the surface melts and sometimes erupts onto the surface. On the terrestrial planets we are familiar with volcanos erupting molten rock as lava. On objects whose outer layers are ice rather than rock it can be water or other liquids that flow onto the surface, or sometimes gases that vent. The volcanism of these low temperature ices is called cryo-volcanism.
On a planetary scale erosion is a minor process but it can produce dramatic features . The most effective agent of erosion is liquid water, though wind and ice can also cause erosion.
Read Also: Can You Add More Solar Panels To An Existing System
What Does Pluto Look Like
Since Pluto is so far from Earth, little was known about the dwarf planet’s size or surface conditions until 2015, when NASA’s New Horizons space probe made a close flyby of Pluto. New Horizons showed that Pluto has a diameter of 1,473 miles , less than one-fifth the diameter of Earth, and only about two-thirds as wide as Earth’s moon.
Observations of Pluto’s surface by the New Horizons spacecraft revealed a variety of surface features, including mountains that reach as high as 11,000 feet , comparable to the Rocky Mountains on Earth. While methane and nitrogen ice cover much of the surface of Pluto, these materials are not strong enough to support such enormous peaks, so scientists suspect that the mountains are formed on a bedrock of water ice.
Pluto’s surface is also covered in an abundance of methane ice, but New Horizons scientists have observed significant differences in the way the ice reflects light across the dwarf planet’s surface. The dwarf planet also possesses ice ridge terrain that appears to look like a snakeskin astronomers spotted similar features to Earth’s penitentes, or erosion-formed features on mountainous terrain. The Pluto features are much larger they are estimated at 1,650 feet tall, while the Earth features are only a few meters in size.
NASA’s Hubble Space Telescope has also revealed evidence that Pluto’s crust could contain complex organic molecules.
And Then There Were Eight
Things went downhill for Pluto in 2006, when the IAU redefined what it means to be a planet, declaring that a planet must be a celestial body that orbits the sun, is round or nearly round, and clears the neighborhood around its orbit. Pluto failed on the third account because its orbit overlaps with Neptune.
The IAU reclassified it as a dwarf planet, also calling it a Trans-Neptunian Object, which prompted outrage from schoolchildren, small planet enthusiasts, and the internet in general.
For many space lovers, Plutos demotion felt sudden. But in the academic world of astronomy, it was a process that began just decades after the dwarf planets discovery.
In 1992, astronomers at the University of Hawaii observatory in Mauna Kea discovered a small, icy celestial body a bit farther away than the orbit of Neptune. Named Kuiper Belt Object 1992 QBI, the object prompted speculation that Pluto was just one of many planet-like objects in the Kuiper Belt.
The final blow came in 2003 when California Institute of Technology professor Mike Brown discovered Eris, a dwarf planet that actually has a bit more mass than Pluto. Astronomers began to suspect that more of these could-be planets were floating around.
Now Brown is dubbed The Man Who Killed Pluto because rather than give planet status to Eris and every celestial body larger than Pluto, the IAU decided to knock Pluto down a peg.
Recommended Reading: How To Remove Solar Panels
Inclined To Be Eccentric
Pluto’s 248-year long orbit is less circular – more elliptical or “egg-shaped” – than those of the other planets. Pluto’s orbit has an eccentricity of 0.25, which means that Pluto’s distance from the Sun is as little as 29.7 AU – temporarily bringing it closer to the Sun than Neptune – and as great as 49.7 au.
For about 20 years in each orbit, Pluto is actually closer to the Sun than Neptune. While all of the other planets have orbits that are close to the ecliptic, Pluto’s orbit is inclined by 17 degrees.
While Pluto’s orbit is close to Neptune’s, the planets won’t collide since their orbits are in an exact resonance. Pluto orbits the Sun twice for every three orbits of Neptune. As a result, Pluto and Neptune are never very close to each other. This is strong evidence against the idea that Pluto is an escaped moon of Neptune.
Imagine an observer looking down on the solar system from 18 billion miles above and watching Pluto from the time of the U.S. Declaration of Independence in 1776 through historic events of the past couple of centuries. By the time the planned New Horizons mission makes its flyby of Pluto in 2015, the dwarf planet will have made almost a complete orbit of the Sun.
The period around Pluto’s closest approach to the Sun – known as perihelion – was a busy time for Pluto events! Click the graphics below for a closer look.
These diagrams were made using data from the Jet Propulsion Laboratory’s Solar System Simulator.
Faq: Which Spacecraft Are Headed To Interstellar Space
Five spacecraft have achieved enough velocity to eventually travel beyond the boundaries of our solar system. Two of them reached the unexplored space between the stars after several decades in space.
- Voyager 1 went interstellar in 2012 and Voyager 2 joined it in 2018. Both spacecraft are still in communication with Earth. Both spacecraft launched in 1977.
- NASA’s New Horizons spacecraft is currently exploring an icy region beyond Neptune called the Kuiper Belt. It eventually will leave our solar system.
- Pioneer 10 and Pioneer 11 also will ultimately travel silently among the stars. The spacecraft used up their power supplies decades ago.
Read Also: What Can You Run Off A 100 Watt Solar Panel
An Atmospheric Freeze Out On Pluto
Pluto is currently moving away from the Sun, having reached its closest approach distance in 1989. Generally, the closer an object is to the Sun, the warmer it should be and the more rapidly its surface ice should sublime into space. The sublime of ices on the surface of Pluto is responsible for its tenuous atmosphere. As Pluto moves away from the Sun it will get colder and, eventually, its atmosphere will almost completely condense back onto the surface.
The actual situation is a bit more complicated than the simple illustration discussed above. Because of “thermal lag,” the time of Pluto’s closest approach to the Sun in 1989 was probably not when its surface temperature was greatest, just as the temperature on Earth is hottest at mid-afternoon rather than noon, or high summer is about a month after solstice. In the case of Pluto, the latest observations reveal that the atmosphere has thickened during the past decade. But this trend will definitely reverse as Pluto continues moving away from the Sun. Scientists don’t know exactly when the condensation will start to dominate sublimation – which is why they wanted to get to Pluto as soon as possible!
Alice Solar Occultation
Why Is Pluto No Longer A Planet
In 2006 the International Astronomical Union demoted the much-loved Pluto from its position as the ninth planet from the Sun to one of five dwarf planets. The IAU had likely not anticipated the widespread outrage that followed the change in the solar systems lineup. When the announcement was made , people around the world objected to the planets demotion on principle, saying that it altered tradition and history, rather than engaging with the scientific reasoning. So, what was the IAUs reason for demoting Pluto when it did? Why is Pluto no longer a planet?
The main event of the 2006 General Assembly of the IAU, the proposal that would come to demote Pluto, was a defining moment for the rest of the solar system as well. Fiercely debated by the members of the union, the resolution that was passed officially defined the term planet. What was once a loose word used to describe a large object within the solar system was now specific: planets are celestial objects large enough to be made rounded by their gravitational orbit around the Sun and to have shooed away neighboring planetary objects and debris. Pluto is now classified as a dwarf planet because, while it is large enough to have become spherical, it is not big enough to exert its orbital dominance and clear the neighborhood surrounding its orbit.
Read Also: Solar Panels For Sale Cheap
Nasa Spacecraft Completes Historic Flyby One Billion Miles Beyond Pluto
The researchers say Pluto should instead be classified as a planet under a definition used by scientists since the 16th century: that planets are any geologically active bodies in space.
As well as Pluto, that definition includes many other objects the asteroid Ceres, for example, and the moons Europa, Enceladus and Titan. But the researchers say the more the merrier.
We think theres probably over 150 planets in our solar system, said Philip Metzger, the studys lead author and a planetary physicist at the University of Central Florida.
The study comes amid research based on data from NASAs New Horizons probe, which flew by Pluto in 2015.
The probes revelations have revived debate about Plutos status, planetary geologist Paul Byrne of North Carolina State University said.
There was such interest from the New Horizons flyby, said Byrne, who was not involved in the study. But every time I gave a talk and I put up a picture of Pluto, the first question was not about the planets geology, but why was it demoted? Thats what stuck with people, and thats a real shame.
The researchers argue the IAU definition contradicted a definition of a planet that had stood for centuries.
Objects similar to Pluto, such as Eris and Makemake, had been found by 2006, and so the IAU engineered its definition to exclude them, Metzger said.
The result is that most planetary scientists now disregard the IAUs definition, he said.
As We Approach An International Holiday Known As Pluto Demoted Day An Expert Explains Why The Dwarf Planet Is Still Super Cool
At the edge of our solar system, theres a tiny, icy world with a diameter or length across at its widest point only 18.5 percent as large as Earths. You know it as Pluto.
When your parents were kids, Pluto was actually considered a planet. But 15 years ago, a group of scientists known as the International Astronomical Union voted to make the definition of planets more specific, and Pluto no longer made the cut. According to the IAU, Pluto is technically a dwarf planet, because it has not cleared its neighboring region of other objects. This means that Pluto still has lots of asteroids and other space rocks along its flight path, rather than having absorbed them over time, like the larger planets have done.
Believe it or not, each year on August 24, the international scientific community recognizes Plutos historic downgrade with a holiday called Pluto Demoted Day.
But just because Pluto lost its planet status doesnt mean it isnt fascinating, says Cathy Olkin, a planetary scientist at the Southwest Research Institute.
For instance, Pluto can be more than 4 billion miles away from Earth, depending on where it is in its wonky orbit, and the dwarf planets average temperature dips to -387 degrees Fahrenheit. Thats so cold, things get a little bit weird.
There are many different ways to decide what is a planet, Olkin says. has an atmosphere. It has moons. It goes around the sun.
You May Like: Are Ikea Cabinets Solid Wood
Objects Of The Outer Solar System
This mass vs. distance plot of outer solar system objects shows the enormous range in sizes of these bodies, from Jupiter to comets . Pluto, Charon and Neptune’s moon Triton fall in the 1/100 to 1/1000 Earth-mass range. Notice that some Kuiper Belt Objects appear to be much smaller than planets but much larger than comets.
Names Of The Planets In The Solar System
From the results of the IAU resolution on August 24, 2006, defines a planet, namely a space object that orbits around the Sun and has a large enough mass so that the objects gravitational force can reshape its shape to an almost spherical shape. In an IAU resolution, the number of solar systems has been formalized as eight, consisting of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
But in 2016, researchers discovered a planet which is Planet Nine or Planet X and is said to have a mass ten times larger than Earth and five thousand times the mass of Pluto. The following are the 8 planets in the Solar System that have been designated by the IAU:
Recommended Reading: How To File For Sole Custody In Ga
Was That The End Of The Matter
In a word, no. Some experts immediately questioned the part of the definition about a planet clearing its orbital neighbourhood.
This is because Earth shares its cosmic turf with more than 12,000 near-Earth asteroids. Thus, some have argued that Earth, Jupiter and other planets also fail to meet the IAU’s 2006 definition.
Speaking just after the vote, Prof Alan Stern, chief scientist for the New Horizons mission, called the outcome “an awful decision” and described the new definition as “internally inconsistent”.
Prof Owen Gingerich of Harvard, who chaired the planet definition committee, revealed that only 10% of the 2,700 scientists who had attended the 10-day meeting were present at the Pluto vote. The low turn-out has been blamed on timing the vote was held on the last day of the General Assembly when many participants had left or were preparing to fly out from Prague.
The debate has rumbled on ever since, on television, in the pages of books and in public talks.
Most recently, Alan Stern challenged Neil deGrasse Tyson to a debate on the matter in 2014. But the latter expert turned down the offer, stating: “I don’t have opinions that I require other people to have.”
The flyby of Pluto is unlikely to provide any information relevant to a change in Pluto’s status. But it will bring into clear focus once more what is, and what isn’t, meant by the term “planet”.
