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1. Describe the relationships between various celestial objects including moons, asteroids,comets,planets,stars,solar systems,galaxies and space.

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NOS 1,2,8 & 10
E&S 2,5,8
CW  3
PW 3

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Unit Of Learning for Learning Outcome in Focus.

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Unit Of Learning for Learning Outcome in Focus.

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Lesson Plans 1 of the attached UOL- linked to the LO

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Lesson Plans 1 of the attached UOL- linked to the LO

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Most astronomers believe the Universe began in a Big Bang about 14 billion years ago. At that time, the entire Universe was inside a bubble that was thousands of times smaller than a pinhead. It was hotter and denser than anything we can imagine.

Then it suddenly exploded. The Universe that we know was born. Time, space and matter all began with the Big Bang. In a fraction of a second, the Universe grew from smaller than a single atom to bigger than a galaxy. And it kept on growing at a fantastic rate. It is still expanding today.

As the Universe expanded and cooled, energy changed into particles of matter and antimatter. These two opposite types of particles largely destroyed each other. But some matter survived. More stable particles called protons and neutrons started to form when the Universe was one second old.

Over the next three minutes, the temperature dropped below 1 billion degrees Celsius. It was now cool enough for the protons and neutrons to come together, forming hydrogen and helium nuclei.

After 300 000 years, the Universe had cooled to about 3000 degrees. Atomic nuclei could finally capture electrons to form atoms. The Universe filled with clouds of hydrogen and helium gas.

Last modified 20 June 2014

Story of the Universe

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Most astronomers believe the Universe began in a Big Bang about 14 billion years ago. At that time, the entire Universe was inside a bubble that was thousands of times smaller than a pinhead. It was hotter and denser than anything we can imagine.

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Useful notes and resources

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Exploring Our Solar System: Planets and Space for Kids - FreeSchool

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I found this helpful for creating my powerpoint along with the book

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The Big Bang Theory explains how the universe began with an infinitely hot and dense single point that inflated to form the ever-expanding cosmos we see today.

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This Website has many resources available for both teachers and students, Here are some of the resources I availed of;
https://www.open.edu/openlearn/
This was a sample poster I used to get the students to work together and apply their knowledge.
https://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html
The students were fascinated by this resource as it showed them exactly the dimensions of space.
https://www.bbc.co.uk/bitesize/guides/z8wx6sg/revision/1
This was a good revision recap page for the students, giving them interesting facts too.

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I found these facts helpful to answering the students questions and heighten their interest.

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This website was useful for worksheets and quizzes.

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A collection of classroom resources by Scoilnet

November 14th 2016 will see the closest full moon to Earth since 1948. We won't see another Supermoon like this until 2034. Lets hope for clear skies!

Best to view animations on a PC - flash/ swf player required for some resources. Recommended space websites for news on recent exploration include ESA, NASA Kids, NASA and Space Week Ireland.

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What you need...

To register for a Scoilnet Account you will need to have a Teaching Council number and a roll number for your school in Ireland.

If you already have a Scoilnet Account then you can sign in here.

The benefits...

A Scoilnet account will allow you to upload your resources or weblinks to Scoilnet as well as enabling you to share and add resources to a favourites listing. Users who have a Scoilnet Account will also be able to fully access Scoilnet Maps and Census@School from home.

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Official education portal of the Department of Education and Skills in Ireland. Curriculum focused resources and support for primary and post primary teachers.

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Reviewed papers used to further my depth of knowledge on the learning outcome.

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Reviewed papers used to further my depth of knowledge on the learning outcome.

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"JOURNEY OF THE UNIVERSE FROM BIRTH TO REBIRTH WITH INSIGHT INTO THE UNIFIED INTERACTION OF ELEMENTARY PARTICLES WITH SPIRAL STRUCTURE"

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Paper by Stephen Hawking I found interesting and useful also

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Paper by Stephen Hawking I found interesting and useful also

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Modern scientific thought owes itself to the contributions of many great men and women. Without these individuals, our universe would, quite literally, look very different. However, there are two scientists in the field of cosmology who stand out among all the rest: Edwin Hubble and Georges Lemaître.

By 1930, other cosmologists had concluded that the static (non-evolving) model of the universe was unsatisfactory. This discovery was largely due to the efforts of Edwin Hubble.

Using the world's largest telescope, which is located at Mt. Wilson in California, Hubble showed the distant galaxies all appeared to be receding from us. What's more, these far-flung galaxies were traveling away from us at speeds proportional to their distances. In other words, the farther they are from us, the faster they are flying away. Enter Lemaître.

Lemaître used these findings to draw attention to his earlier paper, in which he explained the relationship between the distance of a galaxy and the recession velocity of that same galaxy. By putting together Hubble's observations with Lemaître's paper, a majority of astronomers became convinced that the universe was, indeed, expanding.

This revolutionized cosmology and how we see the universe - and how we view our place within it.

Why was this find so notable? Shortly after this discovery, Lemaître reasoned that traveling back in time should lead to an epoch in which all the matter in the universe was packed together in an extremely dense state, which is known as a kind of primeval atom. And this was the birth of Big Bang cosmology.

So, let us take a moment to delve into the Big Bang - into the timeline of everything that has ever existed.

Cosmologists have come up with several possible speculations as to what existed before the big bang (if anything existed at all). If these seem rather presumptuous, it's because they are.

1. It's entirely possible that thew was no previous era. Assuming that this is true, it means that matter, energy, space, and time began abruptly. Perhaps this abrupt change sprang from a collision with a parallel universe. Or maybe something else. We really don't know.

2. Another theory is "Quantum Emergence." According to this view, space and time developed out of a primeval state described by a quantum theory of gravity. Notably, we don't have an explanation for quantum gravity just yet. So we can't say much beyond that.

3. There's the landscape multiverse of string theory, which deals with differences of quantum tunneling and quantum fluctuations between different energy states.

4. There's also the cyclic universe. In this theory, the Big Bang is just the latest "big bang" in an endless stream of big bangs - in the continual expansion, collapse, and renewed expansion of space and time.

But as I said, there is no ultimate contender, so let's leave that for a moment and take a look at what we *do* know.

10^ -43 seconds: this is the Planck era, the earliest known meaningful time.

10 ^-35 seconds: cosmic inflation creates what is known as quark-gluon plasma. Protons and neutrons cannot exist yet, only leptons and quarks (with their force carriers, gluons, W and Z bosons and photons). We know the quark soup exists because we have created similar conditions inside particle accelerators. It appears that it is this early quark soup that gave rise to dark matter. Additionally, The quark soup is likely the phase in which matter gained superiority over antimatter (lucky us). Ultimately, cosmologists speculate that the universe had equal amounts of each but, at some point, it developed one extra quark for every billion antiquarks. This imbalance ensured that enough matter survived annihilation as the universe expanded and cooled. (at 10 ^ -11 seconds this battle is starting to give favor to the rise of matter over antimatter).

At 10 ^-5 seconds: protons and neutrons are formed from quarks. Within the first 300 seconds of the existence of the universe, the elements helium, lithium, and heavy hydrogen (deuterium and Helium 3) form from the protons and neutrons by a process called nucleosynthesis.

Nucleosynthesis is the theory that accurately predicts the abundances of elements and isotopes measured in the primeval samples of the universe i.e., in the oldest stars and high-red shifted gas clouds. The abundance of deuterium plays a special role in this process: Its measured value implies that ordinary matter amounts to 4.9% of the total energy density in the universe (the remainder is dark energy and matter). This agrees with the data collected by Planck from the CMBR. This is an amazing triumph as two completely different measurements, one built on nuclear physics when the universe was a second old and the other based on atomic physics when the universe was 380 000 years old, agree with one another. This verification is a strong indication that our model of the universe is accurate.

So, let's take a look at our universe from this era. You've probably heard the old adage, "a picture is worth a thousand words." Well, in this case, the pictures is worth roughly 900 million dollars. I am talking about ESO's Planck Satellite and its " baby snapshot" of the universe i.e., the cosmic microwave background radiation (CMB). This image reveals the age, density, geometry, and overall composition of the entire early universe. On top of this, the image provides evidence supporting inflationary cosmology via the information that we can extract from it. In essence, quantum fluctuations causing temperature differences in this inflation field (on the subatomic scale) get exponentially blown up to astrophysical sizes. The most remarkable thing about this is that observations of the cosmic microwave background radiation (from WMAP and ESO's Planck observatory) agree with the prediction of inflation, providing the strongest evidence for this theory yet.

380, 000 years: when the nearly uniform soup cooled to about 3000 Kelvin, atoms formed nuclei and electrons. Photons ceased to scatter and streamed through space unhindered, turning the prior opaque universe into one with visible light.

380,000 years to about 1 million years:we enter a period called the Dark ages; existing between it is known as the final frontier of cosmology. We know little about this period except that the first stars and galaxies should have formed at about

100 million years: the limit of current observations, that is, the highest red-shifted objects detectable (the oldest objects that we can see) are at a time of when the universe was 600 million years old. Two future projects that have already begun construction, the James Webb Space Telescope and the Square Kilometer Array, are specifically designed to shed some light on this era and (hopefully) bring the dark ages to an end.

9 billion years: our solar system forms (yay us!).

10 billion years: when dark energy, a mysterious force that cosmologists have yet to wholly pin down, starts to accelerate. At 20 billion years the Milky Way will collide with the Andromeda galaxy (our solar system, or at least the inner planets, will be gone by that time, due to the sun's rapid expansion that will come once it exhausts its supply of fuel for nuclear fusion.)

The ultimate fate of our universe hinges on dark energy. If the universe continues to grow at about the same pace, this will result in all the last stars burning out in about 100 trillion years (so we've got some time left anyway). If this is true, at 30 billion years all other galaxies are pulled from our view and all evidence of the big bang is lost forever (it may be possible that future astronomers could deduce its existence using a few methods...but hopefully we keep good records).

Dark energy could also intensify, resulting in a "Big Rip" scenario. From superclusters to atoms, dark energy effectively tears everything apart. This would happen at approximately 50 billion years.

Alternatively, dark energy could slow down. This deceleration, ould give gravity the upper hand and lead to a collapse. And at 30 billion years, we could have what is known as a "Big crunch". This could result in a new big bang from the cyclic universe scenario.

The nature of universe is anything but simple, but cosmology has made leaps and bounds in such a short period of time because of technology and the rigors of the scientific method. If we can take anything from this invaluable knowledge, is that the march of scientific must continue...because the universe sure isn't going to slow down and wait for us to catch up.

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The Timeline of the Big Bang and Everything We Know

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Modern scientific thought owes itself to the contributions of many great men and women. Without these individuals, our universe would, quite literally, look very different. However, there are two scientists in the field of cosmology who stand out among all the rest: Edwin Hubble and Georges Lemaître.

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The Big Bang

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Edwin Hubble (article) | 2. The Big Bang | Khan Academy

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Read and learn for free about the following article: Edwin Hubble

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Relativity

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The Nobel Prize in Physics 1921 was awarded to Albert Einstein “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect”

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Gravity

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Isaac Newton | Biography, Facts, Discoveries, Laws, & Inventions

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Isaac Newton, the brilliant physicist and mathematician, revolutionized our understanding of the universe with his laws of motion and universal gravitation, forever changing the course of scientific inquiry.

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NASA.gov brings you the latest images, videos and news from America's space agency. Get the latest updates on NASA missions, watch NASA TV live, and learn about our quest to reveal the unknown and benefit all humankind.

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Strange Powerful Exploding Supernova Was Recent | Video

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(Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images)

The order of the planets in the solar system, starting nearest the sun and working outward is the following: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and then the possible Planet Nine.

The solar system extends from the sun, goes past the four inner planets, through the asteroid belt to the four gas giants and on to the disk-shaped Kuiper Belt and far beyond to the teardrop-shaped heliopause.

Scientists estimate that the edge of the solar system is about 9 billion miles (15 billion kilometers) from the sun. Beyond the heliopause lies the giant, spherical Oort Cloud, which is thought to surround the solar system.
Related: 10 incredible volcanoes in our solar system
Ever since the discovery of Pluto in 1930, kids grew up learning that the solar system has nine planets. That all changed in the late 1990s when astronomers started arguing about whether Pluto was indeed a planet. In a highly controversial decision, the International Astronomical Union ultimately decided in 2006 to designate Pluto as a "dwarf planet," reducing the list of the solar system's true planets to just eight.

If you insist on including Pluto, it would come after Neptune on the list. Pluto is truly way out there and on a wildly tilted, elliptical orbit (two of the several reasons it was demoted).
Related: 15 stunning places on Earth that look like they're from another planet
Astronomers, however, are still hunting for another possible planet in our solar system, a true ninth planet, after mathematical evidence of its existence was revealed on Jan. 20, 2016. The alleged "Planet Nine," also called "Planet X," is believed to be about 10 times the mass of Earth and 5,000 times the mass of Pluto.

Types of planets in the solar system

The inner four planets closest to the sun - Mercury, Venus, Earth and Mars - are often called the " terrestrial planets" because their surfaces are rocky. Pluto also has a rocky, albeit frozen, surface but has never been grouped with the four terrestrials.

The four large outer worlds - Jupiter, Saturn, Uranus and Neptune - are sometimes called the Jovian or "Jupiter-like" planets because of their enormous size relative to the terrestrial planets. They're also mostly made of gases like hydrogen, helium and ammonia rather than of rocky surfaces, although astronomers believe some or all of them may have solid cores.

Jupiter and Saturn are sometimes called the gas giants, whereas the more distant Uranus and Neptune have been nicknamed the ice giants. This is because Uranus and Neptune have more atmospheric water and other ice-forming molecules, such as methane, hydrogen sulfide and phosphene, that crystallize into clouds in the planets' frigid conditions, according to the Planetary Society. For perspective, methane crystallizes at minus 296 Fahrenheit (minus 183 degrees Celsius), according to the U.S. National Library of Medicine.

Solar system FAQs answered by an expert

We asked Maximilian Guenther, ESA Project Scientist and mission representative of ESA's Characterising Exoplanet Satellite (CHEOPS) mission a few frequently asked questions about solar systems.

What is (and isn't) a planet?

The IAU defines a true planet as a body that circles the sun without being some other object's satellite; is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star); and has "cleared its neighborhood" of most other orbiting bodies.

But that restrictive definition helped isolate what should and should not be considered a planet - a problem that arose as astronomers discovered more and more planet-like objects in the solar system. Pluto was among the bodies that didn't make the cut and was re-classified as a dwarf planet.

The problem with Pluto, aside from its small size and offbeat orbit, is that it doesn't clear its neighborhood of debris - it shares its space with lots of other objects in the Kuiper Belt. Still, the demotion of Pluto remains controversial.

The IAU planet definition also put other small, round worlds into the dwarf planet category, including the Kuiper Belt objects Eris, Haumea and Makemake.

Ceres, a round object in the Asteroid Belt between Mars and Jupiter, also got the boot. Ceres was considered a planet when it was discovered in 1801, but it was later deemed to be an asteroid. That still didn't quite fit because it was so much larger (and rounder) than the other asteroids. Astronomers instead deemed it a dwarf planet in 2006, although some astronomers like to consider Ceres as a 10th planet (not to be confused with Nibiru or Planet X).

Below is a brief overview of the eight true planets in our solar system, moving from that closest to the sun to the farthest from the sun:
Related: Solar eclipses 2023: When, where & how to see them
The sun is by far the largest object in our solar system, containing 99.8% of the solar system's mass. It sheds most of the heat and light that makes life possible on Earth and possibly elsewhere. Planets orbit the sun in oval-shaped paths called ellipses, with the sun slightly off-center of each ellipse.

NASA has a fleet of spacecraft observing the sun, such as the Parker Solar Probe, to learn more about its composition, and to make better predictions about space weather and its effect on Earth.

Mercury: The closest planet to the sun

Mercury is the closest planet to the sun and the smallest planet in the solar system - it is only a little larger than Earth's moon. Mercury zips around the sun in only 88 days and because it is so close to our star (about two-fifths the distance between Earth and the sun).

Mercury experiences dramatic changes in its day and night temperatures. Mercury temperatures can reach a scorching 840 F (450 C) in the day, which is hot enough to melt lead. Meanwhile, on the night side, temperatures drop to minus 290 F (minus 180 C).

- Diameter: 3,031 miles (4,878 km)

Mercury's atmosphere is very thin and primarily composed of oxygen, sodium, hydrogen, helium and potassium. Because the atmosphere is so thin it cannot incoming meteors, its surface is therefore pockmarked with craters, just like our moon.

Over its four-year mission, NASA's MESSENGER spacecraft revealed incredible discoveries that challenged astronomers' expectations. Among those findings was the discovery of water ice and frozen organic compounds at Mercury's north pole and that volcanism played a major role in shaping the planet's surface.

Related: How was Mercury formed?

Venus: Earth's solar system twin

Venus is the second planet from the sun and is the hottest planet in the solar system. Its thick atmosphere is extremely toxic and composed of sulfuric acid clouds, the planet is an extreme example of the greenhouse effect.

The average temperature on Venus' surface is 900 F (465 C). At 92 bar, the pressure at the surface would crush and kill you. And oddly, Venus spins slowly from east to west, the opposite direction of most of the other planets.

Venus is sometimes referred to as Earth's twin as they are similar in size and radar images beneath its atmosphere reveal numerous mountains and volcanoes. But beyond that, the planets could not be more different.

The Greeks believed Venus was two different objects - one in the morning sky and another in the evening. Because it is often brighter than any other object in the sky, Venus has generated many UFO reports.

Related: How was Venus formed?

Earth: Our home planet, filled with life

Earth, our home planet, is the third planet from the sun. It is a water world with two-thirds of the planet covered by water. Earth's atmosphere is rich in nitrogen and oxygen and it is the only world known to harbor life.

- Diameter: 7,926 miles (12,760 km)

- Orbit: 365.24 days

- Day: 23 hours, 56 minutes

- Number of moons: 1

Earth rotates on its axis at 1,532 feet per second (467 meters per second) - slightly more than 1,000 mph (1,600 kph) - at the equator. The planet zips around the sun at more than 18 miles per second (29 km per second).

Related: 10 Earth impact craters you must see

Mars: The solar system's Red Planet

Mars is the fourth planet from the sun. It is a cold, desert-like planet covered in iron oxide dust that gives the planet its signature red hue. Mars shares similarities with Earth: It is rocky, has mountains, valleys and canyons, and storm systems ranging from localized tornado-like dust devils to planet-engulfing dust storms.

Substantial scientific evidence suggests that Mars at one point billions of years ago was a much warmer, wetter world, rivers and maybe even oceans existed. Although Mars' atmosphere is too thin for liquid water to exist on the surface for any length of time, remnants of that wetter Mars still exist today. Sheets of water ice the size of California lie beneath Mars' surface, and at both poles are ice caps made in part of frozen water.

- Diameter: 4,217 miles (6,787 km)

- Number of moons: 2

Scientists also think ancient Mars would have had the conditions to support life like bacteria and other microbes. Hope that signs of this past life - and the possibility of even current lifeforms - may exist on the Red Planet has driven numerous Mars missions and the Red Planet is now one of the most explored planets in the solar system.

Related: How long does it take to get to Mars?

The asteroid belt

Between Mars and Jupiter lies the asteroid belt. Asteroids are minor planets, and according to NASA there are approximately between 1.1 and 1.9 million asteroids in the main asteroid belt larger than 0.6 miles (1 km) in diameter and millions more smaller asteroids.

The dwarf planet Ceres, about 590 miles (950 km) in diameter, resides here. A number of asteroids have orbits that take them closer into the solar system that sometimes lead them to collide with Earth or the other inner planets.

Jupiter: The largest planet in our solar system

Jupiter is the fifth planet from the sun and the largest planet in the solar system. The gas giant is more than twice as massive as all the other planets combined, according to NASA.

Its swirling clouds are colorful due to different types of trace gases including ammonia ice, ammonium hydrosulfide crystals as well as water ice and vapor.

A famous feature in its swirling clouds is Jupiter's Great Red Spot, a giant storm more than 10,000 miles wide, first observed in 1831 by amateur astronomer Samuel Heinrich Schwabe. It has raged at more than 400 mph for the last 150 years, at least.

Jupiter has a strong magnetic field, and with 75 moons, including the largest moon in the solar system, Ganymede.

Related: Jupiter's moons: Facts about the largest Jovian moons

Saturn: The ringed jewel of the solar system
Related: How far away is Saturn?
Saturn is the sixth planet from the sun and is famous for its large and distinct ring system. Though Saturn is not the only planet in the solar system with rings.

When polymath Galileo Galilei first studied Saturn in the early 1600s, he thought it was an object with three parts: a planet and two large moons on either side. Not knowing he was seeing a planet with rings, the stumped astronomer entered a small drawing - a symbol with one large circle and two smaller ones - in his notebook, as a noun in a sentence describing his discovery. More than 40 years later, Christiaan Huygens proposed that they were rings.

The rings are made of ice and rock and scientists are not yet sure how they formed. The gaseous planet is mostly hydrogen and helium and has numerous moons.

Uranus: The tilted, sideways planet in our solar system

Uranus is the seventh planet from the sun and is a bit of an oddball.

It has clouds made of hydrogen sulfide, the same chemical that makes rotten eggs smell so foul. It rotates from east to west like Venus. But unlike Venus or any other planet, its equator is nearly at right angles to its orbit - it basically orbits on its side.

- Diameter: 31,763 miles (51,120 km)

- Orbit: 84 Earth years

- Day: 18 Earth hours
Related: How did Uranus form?
- Number of moons: 27

Astronomers believe an object twice the size of Earth collided with Uranus roughly 4 billion years ago, causing Uranus to tilt. That tilt causes extreme seasons that last 20-plus years, and the sun beats down on one pole or the other for 84 Earth-years at a time.

The collision is also thought to have knocked rock and ice into Uranus' orbit. These later became some of the planet's 27 moons. Methane in Uranus' atmosphere gives the planet its blue-green tint. It also has 13 sets of faint rings.

Uranus holds the record for the coldest temperature ever measured in the solar system - minus 371.56 degrees F (minus 224.2 degrees C). The average temperature of Uranus is minus 320 degrees Fahrenheit (-195 degrees Celsius).

Neptune: A giant, stormy blue planet

Neptune is the eighth planet from the sun and is on average the coldest planet in the solar system. The average temperature of Neptune at the top of the clouds is minus 346 degrees Fahrenheit (minus 210 degrees Celsius).

Neptune is approximately the same size as Uranus and is known for its supersonic strong winds. The planet is more than 30 times as far from the sun as Earth.

Neptune was the first planet predicted to exist by using math, rather than being visually detected. Irregularities in the orbit of Uranus led French astronomer Alexis Bouvard to suggest some other planet might be exerting a gravitational tug. German astronomer Johann Galle used calculations to help find Neptune in a telescope. Neptune is about 17 times as massive as Earth and has a rocky core.

Related: There's something strange going on inside Neptune

Trans-Neptunian region

Astronomers had long suspected that a band of icy material known as the Kuiper Belt existed past the orbit of Neptune extending from about 30 to 55 times the distance of Earth to the sun, and from the last decade of the 20th century up to now, they have found more than a thousand of such objects. Scientists estimate the Kuiper Belt is likely home to hundreds of thousands of icy bodies larger than 60 miles (100 km) wide, as well as an estimated trillion or more comets.

Pluto, now considered a dwarf planet, dwells in the Kuiper Belt. It is not alone - recent additions include Makemake, Haumea and Eris. Another Kuiper Belt object dubbed Quaoar is probably massive enough to be considered a dwarf planet, but it has not been classified as such yet. Sedna, which is about three-fourths the size of Pluto, is the first dwarf planet discovered in the Oort Cloud. NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015.

Pluto: Once a planet, now a dwarf planet

Pluto was once the ninth planet from the sun and is unlike any other planet in the solar system.

It is smaller than Earth's moon; its orbit is highly elliptical, falling inside Neptune's orbit at some points and far beyond it at others; and Pluto's orbit doesn't fall on the same plane as all the other planets - instead, it orbits 17.1 degrees above or below.

It is smaller than Earth's moon; its orbit is highly elliptical, falling inside Neptune's orbit at some points and far beyond it at others; and Pluto's orbit doesn't fall on the same plane as all the other planets - instead, it orbits 17.1 degrees above or below, taking 288 years to complete a single orbit according to ESA.

From 1979 until early 1999, Pluto had been the eighth planet from the sun. Then, on Feb. 11, 1999, it crossed Neptune's path and once again became the solar system's most distant planet - until it was redefined as a dwarf planet. It's a cold, rocky world with a tenuous atmosphere.

Scientists thought it might be nothing more than a hunk of rock on the outskirts of the solar system. But when NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015, it transformed scientists' view of Pluto.

Pluto is a very active ice world that's covered in glaciers, mountains of ice water, icy dunes and possibly even cryovolcanoes that erupt icy lava made of water, methane or ammonia.

Related: Why isn't Pluto a planet anymore?

Planet Nine: A planet search at solar system's edge

In 2016, researchers proposed the possible existence of a ninth planet, for now, dubbed "Planet Nine" or Planet X. The planet is estimated to be about 10 times the mass of Earth and to orbit the sun between 300 and 1,000 times farther than the orbit of the Earth.

Scientists have not seen Planet Nine. They inferred its existence by its gravitational effects on other objects in the Kuiper Belt, a region at the fringe of the solar system that is home to icy rocks left over from the birth of the solar system. Also called trans-Neptunian objects, these Kuiper Belt objects have highly elliptical or oval orbits that align in the same direction.

Scientists Mike Brown and Konstantin Batygin at the California Institute of Technology in Pasadena described the evidence for Planet Nine in a study published in the Astronomical Journal. The research is based on mathematical models and computer simulations using observations of six other smaller Kuiper Belt Objects with orbits that aligned in a similar matter.

A hypothesis proposed in September 2019 on the pre-print server arXiv suggests Planet Nine might not be a planet at all. Instead, Jaku Scholtz of Durham University and James Unwin of the University of Illinois at Chicago speculate it could be a primordial black hole that formed soon after the Big Bang and that our solar system later captured, according to Newsweek. Unlike black holes that form from the collapse of giant stars, primordial black holes are thought to have formed from gravitational perturbations less than a second after the Big Bang, and this one would be so small (5 centimeters in diameter) that it would be challenging to detect.

Astronomers continue to come up empty in their search for Planet 9. A recent 2022 sky survey using the 6-meter Atacama Cosmology Telescope (ACT) in Chile found thousands of tentative candidate sources but none could be confirmed.

Related: The nonexistent planet Nibiru

The edge of the solar system

Past the Kuiper Belt is the very edge of the solar system, the heliosphere, a vast, teardrop-shaped region of space containing electrically charged particles given off by the sun. Many astronomers think that the limit of the heliosphere, known as the heliopause, is about 9 billion miles (15 billion km) from the sun.

The Oort Cloud lies well past the Kuiper Belt, considered to be located between 2,000 and 5,000 astronomical units (AU) from the sun. The outer edge of the Oort Cloud may reach as far as 10,000 up to 100,000 AU from the sun. One AU is equal to approximately 93,000,000 miles (150 million kilometers). The Oort Cloud is home to billions, or even trillions of objects, according to NASA Science.

Solar system formation and discovery

Approximately 4.5 billion years ago a dark cloud of gas and dust began to collapse. As it shrank, the cloud flattened into a swirling disk known as a solar nebula, according to NASA Science.

The heat and pressure eventually became so high that hydrogen atoms began to combine to form helium. The nuclear reactions released vast amounts of energy and our sun was formed.

The sun accumulated about 99% of the available matter and the remaining material further from the sun formed smaller clumps inside the spinning disk. Some of these clumps gained enough mass that their gravity shaped them into spheres, becoming planets, dwarf planets and moons. Other leftover pieces became asteroids, comets and smaller moons that make up our solar system.

Read more: How did the solar system form?

For millennia, astronomers have followed points of light that seemed to move among the stars. The ancient Greeks named them planets, meaning "wanderers." Mercury, Venus, Mars, Jupiter and Saturn were known in antiquity, and the invention of the telescope added the Asteroid Belt, Uranus, Neptune, Pluto and many of these worlds' moons. The dawn of the space age saw dozens of probes launched to explore our system, an adventure that continues today.
NASA solar system exploration
There have been five human-made objects so far, Voyager 1, Voyager 2, New Horizons, Pioneer 10 and Pioneer 11, that have crossed the threshold into interstellar space.

Related: How much of the solar system is made of interstellar stuff?

Additional resources

Explore the solar system in greater detail with these interactive resources from NASA. Discover the wonders of the solar system with this educational material from ESA. See where the planets are in their current orbit of the sun with this interactive orrery from NASA.

Bibliography

Prialnik, Dina K., Antonella Barucci, and Leslie Young, eds. The Trans-Neptunian Solar System. Elsevier, 2019.

Pirani, Simona, et al. " Consequences of planetary migration on the minor bodies of the early solar system." Astronomy & Astrophysics 623 (2019): A169.

Scholtz, Jakub, and James Unwin. " What if Planet 9 is a primordial black hole?." Physical Review Letters 125.5 (2020): 051103.

Brown, Michael E., and Konstantin Batygin. " Observational constraints on the orbit and location of planet nine in the outer solar system." The Astrophysical Journal Letters 824.2 (2016): L23.

Raymond, Sean N., et al. " Building the terrestrial planets: Constrained accretion in the inner Solar System." Icarus 203.2 (2009): 644-662.

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Solar System Planets: Order of the 8 (or 9) Planets

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Explore the eight (or nine) planets of the solar system in order from nearest to the sun and discover the many wonders of our solar system along the way.

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Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, [...]

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Have you ever wondered what causes the moon phases? We all know that its appearance changes over time. But why? The good way to understand the phases of the moon is to examine an earth-moon-sun diagram:

©MoonConnection.com All Rights Reserved. This moon phases diagram is NOT public domain and may not be used on websites, copied, printed or republished except by permission. Please contact me for high resolution version available for small license fee.

Diagram Explanation

The illustration may look a little complex at first, but it's easy to explain.

Sunlight is shown coming in from the right. The earth, of course, is at the center of the diagram. The moon is shown at 8 key stages during its revolution around the earth. The moon phase name is shown alongside the image. The dotted line from the earth to the moon represents your line of sight when looking at the moon. The large moon image shows what you would see at that point in the cycle. For the waning gibbous, third quarter, and waning crescent phases you have to mentally turn yourself upside down when imagining the line of sight. When you do this, you'll "see" that the illuminated portion is on your left, just as you see in the large image.

One important thing to notice is that exactly one half of the moon is always illuminated by the sun. Of course that is perfectly logical, but you need to visualize it in order to understand the phases. At certain times we see both the sunlit portion and the shadowed portion -- and that creates the various moon phase shapes we are all familiar with. Also note that the shadowed part of the moon is invisible to the naked eye; in the diagram above, it is only shown for clarification purposes. Finally, please realize this diagram is only meant to demonstrate how the phases work; the small inner moons in the diagram do not show the fact that the same side of the moon always faces Earth.

So the basic explanation is that the lunar phases are created by changing angles (relative positions) of the earth, the moon and the sun, as the moon orbits the earth.

If you'd like to examine the phases of the moon more closely, via computer software, you may be interested in this moon phases calendar software.

Moon Phases Simplified

It's probably easiest to understand the moon cycle in this order: new moon and full moon, first quarter and third quarter, and the phases in between.

As shown in the above diagram, the new moon occurs when the moon is positioned between the earth and sun. The three objects are in approximate alignment (why "approximate" is explained below). The entire illuminated portion of the moon is on the back side of the moon, the half that we cannot see.

At a full moon, the earth, moon, and sun are in approximate alignment, just as the new moon, but the moon is on the opposite side of the earth, so the entire sunlit part of the moon is facing us. The shadowed portion is entirely hidden from view.

The first quarter and third quarter moons (both often called a " half moon"), happen when the moon is at a 90 degree angle with respect to the earth and sun. So we are seeing exactly half of the moon illuminated and half in shadow.

Once you understand those four key moon phases, the phases between should be fairly easy to visualize, as the illuminated portion gradually transitions between them.

An easy way to remember and understand those "between" lunar phase names is by breaking out and defining 4 words: crescent, gibbous, waxing, and waning. The word crescent refers to the phases where the moon is less than half illuminated. The word gibbous refers to phases where the moon is more than half illuminated. Waxing essentially means "growing" or expanding in illumination, and waning means "shrinking" or decreasing in illumination.

Thus you can simply combine the two words to create the phase name, as follows:

After the new moon, the sunlit portion is increasing, but less than half, so it is waxing crescent. After the first quarter, the sunlit portion is still increasing, but now it is more than half, so it is waxing gibbous. After the full moon (maximum illumination), the light continually decreases. So the waning gibbous phase occurs next. Following the third quarter is the waning crescent, which wanes until the light is completely gone -- a new moon.

The Moon's Orbit

You may have personally observed that the moon goes through a complete moon phases cycle in about one month. That's true, but it's not exactly one month. The time required for the moon to move to the same position (same phase) as seen by an observer on earth is called the synodic period or lunation and it is 29.5305882 days on average (+/- 0.27 days due to the varying distance between the earth and the moon). If you were to view the moon cycling the earth from outside our solar system (the viewpoint of the stars), the time required is 27.3217 days, roughly two days less. This figure is called the sidereal period or orbital period. Why is the synodic period different from the sidereal period? The short answer is because on earth, we are viewing the moon from a moving platform: during the moon cycle, the earth has moved approximately one month along its year-long orbit around the sun, altering our angle of view with respect to the moon, and thus altering the phase. The earth's orbital direction is such that it lengthens the period for earthbound observers.

Although the synodic and sidereal periods can be used in certain calculations, the moon phase can't be precisely calculated by simple division of days because the moon's motion (orbital speed and position) is affected and perturbed by various forces of different strengths. Hence, complex equations are used to determine the exact position and phase of the moon at any given point in time.

Also, looking at the diagram (and imagining it to scale), you may have wondered why, at a new moon, the moon doesn't block the sun, and at a full moon, why the earth doesn't block sunlight from reaching the moon. The reason is because the moon's orbit about the earth is about 5 degrees off from the earth-sun orbital plane.

However, at special times during the year, the earth, moon, and sun do in fact "line up". When the moon blocks the sun or a part of it, it's called a solar eclipse, and it can only happen during the new moon phase. When the earth casts a shadow on the moon, it's called a lunar eclipse, and can only happen during the full moon phase. Roughly 4 to 7 eclipses happen in any given year, but most of them minor or "partial" eclipses. Major lunar or solar eclipses are relatively uncommon.

Moon Software

If you want to follow the phases of the moon, you should definitely take a look at QuickPhase Pro, our flagship moon software product for your personal computer. This attractive and fun software covers thousands of years of past and future moon phases and is easy to use.

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Have you ever wondered what causes the moon phases? We all know that its appearance changes over time. But why? The good way to understand the phases of the moon is to examine an earth-moon-sun diagram: ©MoonConnection.com All Rights Reserved.

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Excellent research resources for students

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Excellent research resources for students

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Image: The Vela supernova remnant, seen in visible light.

"In my own view, the important achievement of Apollo was a demonstration that humanity is not forever chained to this planet, and our visions go rather further than that, and our opportunities are unlimited." - Neil Armstrong, 1999
Until Voyager reached the outer solar system we knew very little about the planets that inhabited this region of space. What we have discovered over years of exploration has both excited and mystified us. Come explore the science of the outer planets. Learn what we have already discovered, and discover what we have yet to learn.

Looking for something specific? See the site map to find it quickly.

Highlights

The Orbit Simulator shows the motion of the planets and other objects around the Sun.

The Orbit Simulator
(click to launch)

Use the Solar Wind Tunnel to explore how the sun affects magnetic fields, comets, and other orbiting bodies.

The Solar Wind Tunnel
(click to launch)

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Image: The Vela supernova remnant, seen in visible light. "In my own view, the important achievement of Apollo was a demonstration that humanity is not forever chained to this planet, and our visions go rather further than that, and our opportunities are unlimited."

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Resources for students performing inquiry investigations.

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Resources for students performing inquiry investigations.

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All resources are accessible and easy too use for the student or groups of students who are compiling their data analysis.

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Graphic Design and Illustration

Chris Grahl, d'Vinci Interactive

Content Development

Jaclyn Ricords, d'Vinci Interactive, Education Consultant

Executive Producers

Christina Riska Simmons, National Geographic Society
Mason Scuderi, d'Vinci Interactive
Sara Zeglin, National Geographic Society

Game Design and Development

Editors

Joan Gossett, National Geographic
Andrea Silen, National Geographic

Educator Reviewer

Janis Watson, Implementation Manager & Curriculum Specialist, The Creativity Labs @ Indiana University

Expert Reviewer

Lockheed Martin Space Systems Company

Production Manager

Elaine Larson, National Geographic Society

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Graphic Design and Illustration Chris Grahl, d'Vinci Interactive Content Development Jaclyn Ricords, d'Vinci Interactive, Education Consultant Executive Producers Christina Riska Simmons, National Geographic Society Mason Scuderi, d'Vinci Interactive Sara Zeglin, National Geographic Society Game Design and Development Editors Joan Gossett, National Geographic Andrea Silen, National Geographic Educator Reviewer Janis Watson, Implementation Manager & Curriculum Specialist, The Creativity Labs @ Indiana University Expert Reviewer Lockheed Martin Space Systems Company Production Manager Elaine Larson, National Geographic Society

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Another useful resource for individual research.

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Browse an exciting collection of scientific, historical and cultural facts about space, galaxies, the planets and other objects in the solar system. The latest discoveries, space-related features, graphics and diagrams can be found on the blog.

Start exploring below:

What is Outer Space

Space is the area beyond the upper limits of Earth's atmosphere. It is where all of the asteroids, comets, planets, stars, solar systems and galaxies in our universe are found. Space is a vacuum, meaning it contains almost nothing, but it is not completely empty.

Interesting Facts about Space

1. Space does not begin at a specific altitude above the Earth, but the Kármán line at 100 km is a commonly used definition.

2. The temperature in the void of space is about −270.45 °C.

3. Space is a hard vacuum, meaning it is a void containing very little matter.

4. There is no sound in space because molecules are too far apart to transmit sound.

5. The space between galaxies is not completely empty but has an average of one atom per cubic meter.

6. There are an estimated 100-400 billion stars in our galaxy, the Milky Way.

7. The universe is observed to be 13.8 billion years old and has been expanding since its formation in the Big Bang.

8. In the observable universe there are an estimated 2 trillion (2,000,000,000,000) galaxies.

9. The International Space Station is the largest ever crewed object in space.

10. Spacecraft have visited all the known planets in our solar system.

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Space Facts - Interesting Facts about Space!

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Interesting facts about space, galaxies, planets, moons and other solar system objects. Explore the universe through interesting diagrams, photos and more!