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Saturn is a gas giant planet, and the sixth planet from the Sun in our solar system. It is the second-largest planet in our solar system.
The radius is about nine times that of Earth, so it’s volume is about 95 times larger than Earth.
It has only one-eighth the average density of Earth.
Named after the Roman god of wealth and agriculture.
Its astronomical symbol (♄) represents Saturn’s sickle.
How to get into backyard astronomy
the best places to place a telescope
what do the planets look like from Earth?
These are the relative sizes of the planets in our solar system, compared to the size of the moon. Note that this only shows their relative size, not their location! They are never lined up like this.
what do comets and asteroids look like from Earth?
what do stars look like from Earth?
the largest objects in the night sky
Look up at the night sky – Are there immensely huge things that are just a bit too faint for the human eye to see? You betcha! Check out this amazing composite photo. This shows the actual apparent size of deep space objects, in our night sky, if they were brighter.
The images are in scale with one another, including the Moon, but not to the Milky Way background.
1. The Moon.
2. Andromeda Galaxy.
3. Triangulum Galaxy.
4. Orion Nebula.
5. Lagoon Nebula.
6. Pinwheel Galaxy.
7. Sculptor Galaxy.
8. Supernova remnant 1006.
9. Veil Nebula.
10. Helix Nebula.
11. Sombrero Galaxy.
12. Crab Nebula.
13. Comet Hale-Bopp (c. 1997)
16. International Space Station.
What is a “moon”?
Earth has a moon, Luna, but most of the other planets in our solar system also have moons.
(adapted from Wikipedia)
Interestingly, the Moon was called a “planet” until Copernicus’ publication of De revolutionibus orbium coelestium in 1543.
Until the discovery of the Galilean satellites around Jupiter, in 1610, there was no opportunity for referring to such objects as a class. Galileo chose to refer to his discoveries as Planetæ (“planets”.) It was only later discoverers who chose other terms to distinguish them from the objects they orbited.
The first to use of the term satellite to describe orbiting bodies was the German astronomer Johannes Kepler in his pamphlet Narratio de Observatis a se quatuor Iouis satellitibus erronibus (“Narration About Four Satellites of Jupiter Observed”) in 1610. Kepler derived the term from the Latin word satelles, meaning “guard”, or “companion”, because the satellites accompanied their primary planet in their journey through the heavens.
The term satellite became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of the word “moon”. In 1957, however, the launching of the artificial object Sputnik created a need for new terminology. The terms man-made satellite and artificial moon were very quickly abandoned in favor of the simpler satellite, and as a consequence, the term has become linked primarily with artificial objects flown in space – including, sometimes, even those not in orbit around a planet.
Because of this shift in meaning, the term “moon,” which had continued to be used in a generic sense in works of popular science and in fiction, has regained respectability and is now used interchangeably with natural satellite, even in scientific articles.
To avoid ambiguity, the convention is to capitalize the word Moon when referring to Earth’s natural satellite, but not when referring to other natural satellites.
Many authors define “satellite” or “natural satellite” as orbiting some planet or minor planet, synonymous with “moon” – by such a definition all natural satellites are moons, but Earth and other planets are not satellites.
Mars and its moons, 3D visualization
Pull out from Jupiter Showing Moon Orbits, showing 63 moons
Jupiter And The Galilean moons
Saturn and its major moons
Uranus and its major moons
Neptune and its major moon Triton
Neptune and its rings
Pluto and its moon Charon
How’s this for an idea for a science-fiction story?
The sun has unexpectedly started to swell into a red giant – which would engulf and destroy the Earth. So, “to save humanity, the world’s governments have banded together and constructed thousands of rocket engines across the Earth’s surface. Once installed, they propel the planet out of its solar system and onto a 2,500 year journey to resettle in Alpha Centauri.” (Grant Watson.)
The Wandering Earth (Chinese: 流浪地球) is a 2019 Chinese science fiction film directed by Frant Gwo, loosely based on the novella of the same name by author Liu Cixin. Here’s an image of one of the many “Earth Engines.”
Our question – Could this be done in real life?
What science in the film did they get wrong?
Thrusting the Earth out of orbit with rockets: consider, how much reaction mass would we need to do this?
Even if you could build engines large enough, mining the Earth (as these engines do in the film) causes a problem. There would barely be any Earth left by the point you mined enough dirt to thrust the planet to Proxima Centauri, 4.2 light-years away. “It would take about 95 percent of the mass of Earth to do this,” Elliott estimates.
Stopping the rotation of the Earth?
Gravitational slingshot around Jupiter
Surviving the radiation around Jupiter
We could eventually move human civilization to Mars, which become habitable.
What science could actually work to change Earth’s orbit?
Astronomical engineering: a strategy for modifying planetary orbits
D. G. Korycansky, Gregory Laughlin, Fred C. Adams (7 Feb 2001)
The Sun’s gradual brightening will seriously compromise the Earth’s biosphere within ~ 1E9 years. If Earth’s orbit migrates outward, however, the biosphere could remain intact over the entire main-sequence lifetime of the Sun.
In this paper, we explore the feasibility of engineering such a migration over a long time period. The basic mechanism uses gravitational assists to (in effect) transfer orbital energy from Jupiter to the Earth, and thereby enlarges the orbital radius of Earth.
This transfer is accomplished by a suitable intermediate body, either a Kuiper Belt object or a main belt asteroid. The object first encounters Earth during an inward pass on its initial highly elliptical orbit of large (~ 300 AU) semimajor axis.
The encounter transfers energy from the object to the Earth in standard gravity-assist fashion by passing close to the leading limb of the planet. The resulting outbound trajectory of the object must cross the orbit of Jupiter; with proper timing, the outbound object encounters Jupiter and picks up the energy it lost to Earth.
With small corrections to the trajectory, or additional planetary encounters (e.g., with Saturn), the object can repeat this process over many encounters. To maintain its present flux of solar energy, the Earth must experience roughly one encounter every 6000 years (for an object mass of 1E22 g). We develop the details of this scheme and discuss its ramifications.
As for the Moon, reasoning by analogy with cases of stellar binaries and third-body encounters suggests that the Moon will tend to become unbound by encounters in which O passes inside the Moon’s orbit. (As well, there is the non-zero probability of collisions between O and the Moon, which must be avoided.) Again, detailed quantitative work needs to be done, but it seems that the Moon will be lost from Earth orbit during this process. On the other hand, a subset of encounters could be targeted to “herd” the Moon along with the Earth should that prove necessary.
It has been suggested (cf. Ward and Brownlee, 2000) that the presence of the Moon maintains the Earth’s obliquity in a relatively narrow band about its present value and is thus necessary to preserve the Earth’s habitability. Given that the Moon’s mass is 1/81 that of the Earth, a similarly small increment of the number of encounters should be sufficient to keep it in the Earth’s environment.
The fate of Mars in this scenario remains unresolved. By the time this migration question becomes urgent, Mars (and perhaps other bodies in the solar system) may have been altered for habitability, or at least become valuable as natural resources. Certainly, the dynamical consequences of significantly re-arranging the Solar System must be evaluated. For example, recent work by Innanen et al. (1998) has shown that if the Earth were removed from the Solar System, then Venus and Mercury would be destabilized within a relatively short time. In addition, the Earth will traverse various secular and mean-motion resonances with the other planets as it moves gradually outward. A larger flux of encounters might be needed to escort the Earth rapidly
Journal reference: Astrophys.Space Sci.275:349-366, 2001. Astronomical Engineering: A Strategy For Modifying Planetary Orbits, Springer Link
Cite as: arXiv:astro-ph/0102126 (or arXiv:astro-ph/0102126v1 for this version)
2016 Massachusetts Science and Technology/Engineering Curriculum Framework
8.MS-ESS1-2. Explain the role of gravity in ocean tides, the orbital motions of planets, their moons, and asteroids in the solar system.
HS-PS2-4. Use mathematical representations of Newton’s law of gravitation and Coulomb’s law to both qualitatively and quantitatively describe and predict the effects of gravitational and electrostatic forces between objects.
Next Generation Science Standards
HS-PS2.B.1 ( High School Physical Sciences ): Newton’s law of universal gravitation and Coulomb’s law provide the mathematical models to describe and predict the effects of gravitational and electrostatic forces between distant objects.
Ask questions that arise from careful observation of phenomena, or unexpected results, to clarify and/or seek additional information.
Ask questions that arise from examining models or a theory, to clarify and/or seek additional information and relationships.
Ask and/or evaluate questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of a design.
A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (2012)
PS2.B: TYPES OF INTERACTIONS: Gravitational, electric, and magnetic forces between a pair of objects do not require that they be in contact. These forces are explained by force fields that contain energy and can transfer energy through space. These fields can be mapped by their effect on a test object (mass, charge, or magnet, respectively). Objects with mass are sources of gravitational fields and are affected by the gravitational fields of all other objects with mass. Gravitational forces are always attractive. For two human-scale objects, these forces are too small to observe without sensitive instrumentation. Gravitational interactions are non-negligible, however, when very massive objects are involved. Thus the gravitational force due to Earth, acting on an object near Earth’s surface, pulls that object toward the planet’s center. Newton’s law of universal gravitation provides the mathematical model to describe and predict the effects of gravitational forces between distant objects.
A CURIOUS WORLD: BLACK HOLES: What are black holes made of and how do they work?
Rebuilding the Interstellar Black Hole
Black holes are not as black as we once thought. They are theorized to die a slow death by evaporation, emitting energy known as Hawking radiation.
What’s inside a black hole?
Four types of black holes
PBS NOVA: Black Hole Apocalypse. Season 45, Episode 1
“Black holes are the most enigmatic and exotic objects in the universe. They’re also the most powerful, with gravity so strong it can actually trap light. And they’re destructive. Anything that falls into them vanishes…gone forever. But now, astrophysicists are realizing that black holes may be essential to understanding how our universe unfolded.”
“The Drake Equation is a way to estimate the number of communicating advanced civilizations (N) inhabiting the Galaxy. It is named after Frank Drake who first summarized the things we need to know to answer the question, “how many of them are out there?” The equation breaks this big unknown, complex question into several smaller (hopefully manageable) parts. Once you know how to deal with each of the pieces, you can put them together to come up with a decent guess.”
The search for extraterrestrial intelligence (SETI) is a collective term for any scientific searches for intelligent extraterrestrial life. It is primarily done by monitoring radio signals for signs of transmissions from civilizations on other planets.
What are radio waves?
Radio waves are just a part of the EM (electromagnetic) spectrum.
That sounds dandy, except, what exactly is the “electromagnetic spectrum”?
All parts of the EM spectrum – radio, visible light, etc. – are oscillating electric and magnetic fields. To learn the details, see Light is an electromagnetic field.
How are radio waves different from other parts of the EM spectrum?
They’re made of the same thing, behaving in exactly the same way. Only difference is that radio waves are hundreds of meters to thousands of meters long. Other parts of the spectrum have shorter waves.
What creates radio waves?
With a radio receiver we can hear radio waves coming from all around us. They are naturally produced, and comes from all over the Earth, and outer space. Radio waves are naturally created by:
* Wind whipping over a surface, creating static electricity
* atoms trapped in the magnetic fields around the Earth, and around all other planets as well.
* The Sun (puts out all frequencies of EM radiation!)
* All stars
* Ionized interstellar gas surrounding bright, hot stars
* There are even more complex radio waves naturally generated, you can read this paper: Natural and man-made terrestrial electromagnetic noise
By the late 1800’s humans had learned not only how to receive radio waves, but how to generate them. Today we artificially create radio waves for all sorts of purposes, including
Traditional, over-the-air, radio stations (AM and FM radio)
Traditional, old-fashioned, TV (television)
Cellphone communication (cell towers and the phones)
What is a radio telescope?
The technology of how we detect radio waves.
How does an antenna pick up radio waves?
“If we place a conducting material on the path of such a wave, the passing wave will create an oscillating electric field inside the material; and that field will accelerate charges back and forth through the conductor.”
History of SETI
This section has been adapted from “Search for extraterrestrial intelligence.” Wikipedia, The Free Encyclopedia. 4 Mar. 2019
There have been many earlier searches for extraterrestrial intelligence within the Solar System. In 1896, Nikola Tesla suggested that an extreme version of his wireless electrical transmission system could be used to contact beings on Mars. He conducted an experiment at his Colorado Springs experimental station.
In the early 1900s, Guglielmo Marconi, Lord Kelvin and David Peck Todd also stated their belief that radio could be used to contact Martians, with Marconi stating that his stations had also picked up potential Martian signals.
On August 21–23, 1924, Mars entered an opposition closer to Earth than at any time in the century before or the next 80 years. In the United States, a “National Radio Silence Day” was promoted during a 36-hour period from August 21–23, with all radios quiet for five minutes on the hour, every hour.
At the United States Naval Observatory, scientists used a radio receiver, miles above the ground in a dirigible, to listen for any potential radio messages from Mars.
A 1959 paper by Philip Morrison and Giuseppe Cocconi first pointed out the possibility of searching the microwave spectrum, and proposed frequencies and a set of initial targets.
In 1960, Cornell University astronomer Frank Drake performed the first modern SETI experiment, named “Project Ozma”, after the Queen of Oz in L. Frank Baum’s fantasy books. Drake used a radio telescope at Green Bank, West Virginia, to examine the stars Tau Ceti and Epsilon Eridani.
Soviet scientists took a strong interest in SETI during the 1960s and performed a number of searches. Soviet astronomer Iosif Shklovsky wrote the pioneering book in the field, Universe, Life, Intelligence (1962), which was expanded upon by American astronomer Carl Sagan as the best-selling book Intelligent Life in the Universe (1966).
In the March 1955 issue of Scientific American, John D. Kraus described an idea to scan the cosmos for natural radio signals using a radio telescope. Ohio State University soon created a SETI program.
In 1971, NASA funded a SETI study that involved Drake, Bernard M. Oliver of Hewlett-Packard Corporation, and others. The resulting report proposed the construction of an Earth-based radio telescope array with 1,500 dishes known as “Project Cyclops”. It was not built, but the report formed the basis of much SETI work that followed.
Why don’t any organisms detect radio waves?
(Honors Biology topic)
How difficult will this be?
It is very difficult to pick up Earth’s radio waves from another solar system. As such, we can imagine that it would very difficult to pick up radio waves here, from some other solar system. That’s why we aren’t really looking for random radio waves that happen to escape out into space. Rather, the current projects are looking for much more powerful signals, that we hope would be sent out on purpose.
“That’s a rather extraordinary claim, so I spoke to SETI expert and scifi novelist David Brin about it — and he’s not convinced detection is this easy. He told me that, even if an ETI had a one square kilometer array, they would have to point it a at Earth for the duration of an entire year. “Because it would take that long,” he told io9. “But why stare if you don’t already have a reason to suspect?”
Like SETI Institute’s Seth Shostak, Brin believes that Earth is not detectable beyond five light years. “With one exception: Narrow-focused, coherent (laser-like) planetary radars that are aimed to briefly scan the surfaces of asteroids and moons,” he says, “And not to be confused with military radars that disperse.””
How can we differentiate between natural or artificial (intelligent) signals?
Consider listening to the sound of radio static. Compare that to the sound of a song, or a person giving a speech. Both are sounds – how are they similar? How are they different?
Come up with ideas on how we could differentiate between natural or artificial (intelligent) signals.
“Humanity has received some odd signals in the past. We’ve also sent out some signals ourselves. How could we determine that a signal we’d received was artificial in origin? Or of course inversely, how could an extraterrestrial civilization determine a signal we had sent out was was artificial?”
Listening for Extraterrestrial Blah Blah: At the cosmic dinner party, intelligence is the loudest thing in the room. By Laurance R. Doyle, Illustrations by Tianhua Mao
The Water hole: What radio frequencies should we listen to?
Misconceptions about listening with radio telescopes
Radio signals diminish in strength very rapidly with distance – they decrease according to the inverse square law. What does that mean Consider cooking spray. Oil is sprayed through an opening. In this image, the cooking spray hits a piece of toast and deposits an even layer of butter, 1 mm thick.
When the butter gets twice as far, it becomes only 1/4 as this.
If it travels 3 times as far, it will spread out to cover 3 x 3,
or 9, pieces of toast.
So now the butter will only be 1/9th as thick.
(1/9 is the inverse square of 3)
This pattern is called an inverse-square law.
The same is true for a can of spray paint: as the paint travels further, it covers a wider area, so the paint per area is inversely less thick.
The same pattern of spreading out and weakening, the inverse square laws, is true for radio waves.
Animations of the inverse-square law – animated clip: Inverse-square law for light
Okay – so by the time that radio signals reach even the next solar system they would be unbelievably weak. The radio signals would be even millions of times weaker by the time they travelled across even 1% of the galaxy. Our radio telescopes could never pick up such radio signals.
So if that’s the case, what then are SETI researchers listening for?We are looking for a civilization that wants to be known, one that has deliberately built a high power radio beacon, aimed in one direction at a time. A tightly beamed signal would be millions of times stronger – if by chance we happen to be in its path.
Do SETI researchers believe that someone out there is deliberately sending a signal to us here on Earth specifically? No. However, we know that there are billions of stars, and tens of billions of planets. Many of these planets might support life. Therefore, at any given time there could be many thousands of other worlds with intelligent life
The hope is that some of them would want to communicate, sending a tight, beamed radio signal out into space. If so, then one day we might intercept such a communication.
Article: Is there anybody out there? Jason Davis, October 25, 2017, The Planetary Society
Goldilocks Zone/Circumstellar habitable zone
This section from evolution.berkeley.edu, A Place for Life: A special astronomy exhibit of Understanding Evolution
From the known properties of stars and of the chemistry of water, astronomers can define “habitable zones” around stars where liquid water (and hence life) could exist on the surface of planets.
Too close to the star, and water will boil; too far, and it will freeze. This so-called Goldilocks zone, where the temperature is just right, depends on both the distance from the star and the characteristics of the star itself.
The habitable zone around luminous giant stars is further from the star than the habitable zone around faint dwarfs.
Of course, as noted previously, life may also exist outside these zones, for example in subsurface oceans on icy moons heated from the moon’s interior.
We know that there are around 200 billion stars in our Galaxy. Recent research has revealed that most of them have planets, and that tens of billions of these planets are likely similar in size to Earth, made of rock, and orbit in their stars’ habitable zones.
The question that remains to be answered is what fraction of those potentially habitable worlds host life.
Habitable Zones of Different Stars. NASA/Kepler Mission/Dana Berry.
Habitable zones for binary star systems
What about planets in a solar system with two stars?
Most stars in the Galaxy have at least one stellar companion—binary or multiple star systems. Stars like our Sun with no stellar companion are in the minority.
It would probably be difficult for there to be stable, only slightly elliptical planet orbits in a binary or multiple star system.
Complex life (multi-cellular) will need to have a stable temperature regime to form so the planet orbit cannot be too eccentric. Simple life like bacteria might be able to withstand large temperature changes on a planet with a significantly elliptical orbit but complex life is the much more interesting case.
Suitable binary stars would be those systems where either:
(a) the binary stars orbit very close to each other with the planet(s) orbiting both of them at a large distance (called a “circumbinary planet”)
or (b) the binary stars orbit very far from each other so the planet(s) could reside in stable orbits near each of the stars—the one star’s gravity acting on a planet would be much stronger than that of the other star.
A cool article on this subject: I Built a Stable Planetary System with 416 Planets in the Habitable Zone
Strong magnetic fields may be necessary
Earth has a strong magnetic field. Turns out that this might be necessary on a planet if complex life is to evolve.
Why does Earth have such a strong magnetic field? Earth’s core is still hot and molten. Metal still moves inside it, and moving metal has moving free electrons. Electrons moving around – by definition – are an electrical current. And it turns out that electrical currents create their own magnetic field!
Inside the earth
This field protects the Earth’s atmosphere from some of the Sun’s radiation.
Without such a field most of a planet’s atmosphere is likely to be blown away into space, as happened to Mars.
Mars now has very little atmosphere, and its surface is constantly irradiated by solar radiation.
The Drake Equation
An equation named after Frank Drake, who first summarized the things we need to know to answer the question, “how many possible extraterrestrial civilizations are out there?” The equation breaks this complex question into several smaller (hopefully manageable) parts.
(for the entire SETI unit)
Common Core, English Language Arts Standards » Science & Technical Subjects
CCSS.ELA-LITERACY.RST.9-10.1 – Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions.
CCSS.ELA-LITERACY.RST.9-10.2 – Determine the central ideas or conclusions of a text; trace the text’s explanation or depiction of a complex process, phenomenon, or concept; provide an accurate summary of the text.
CCSS.ELA-LITERACY.RST.9-10.4 – Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context.
CCSS.ELA-LITERACY.RST.9-10.5 – Analyze the structure of the relationships among concepts in a text, including relationships among key terms (e.g., force, friction, reaction force, energy).
CCSS.ELA-LITERACY.RST.9-10.6 – Analyze the author’s purpose in providing an explanation, describing a procedure, or discussing an experiment in a text, defining the question the author seeks to address.
2016 Massachusetts Science and Technology/Engineering Curriculum Framework
HS-PS2-5. Provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current.
6.MS-PS4-1. Use diagrams of a simple wave to explain that (a) a wave has a repeating pattern with a specific amplitude, frequency, and wavelength, and (b) the amplitude of a wave is related to the energy of the wave.
HS-PS4-1. Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling within various media. Recognize that electromagnetic waves can travel through empty space (without a medium) as compared to mechanical waves that require a medium.
HS-PS4-5. Communicate technical information about how some technological devices use the principles of wave behavior and wave interactions with matter to transmit and capture information and energy.
Next Generation Science Standards: Science & Engineering Practices
● Ask questions that arise from careful observation of phenomena, or unexpected results, to clarify and/or seek additional information.
● Ask questions that arise from examining models or a theory, to clarify and/or seek additional information and relationships.
● Ask questions to determine relationships, including quantitative relationships, between independent and dependent variables.
● Evaluate a question to determine if it is testable and relevant.
● Ask and/or evaluate questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of the design
Common Core Math Standards (Inverse-square law)
CCSS.Math.Content.7.RP.A.2a ( Grade 7 ): Decide whether two quantities are in a proportional relationship, e.g., by testing for equivalent ratios in a table or graphing on a coordinate plane and observing whether the graph is a straight line through the origin.
CCSS.Math.Content.7.RP.A.2c ( Grade 7 ): Represent proportional relationships by equations.