Planets & Moons
Earthīs companion planets and their moons
10 Amazing Facts about Saturn's Moons
Saturn lies in the outer Solar System, ten times farther away from the Sun than Earth is. It's best known for its fabulous ring system, but it also has an amazing system of moons including ring shepherds and the smallest round object in the Solar System.
Absolute Beginners - Seeing Mars and beyond
Three beautiful planets - Mars, Jupiter and Saturn - are all visible to the unaided eye. If you have binoculars or a telescope, you can also see some of the moons and other features. Hereīs a beginnerīs guide to the planets which lie beyond Earth.
Absolute Beginners - Seeing Mercury and Venus
We can see five planets with our unaided eyes. But people often ask how to find them and how to recognize them. Here is a beginnerīs guide for seeing Mercury and Venus.
Astronomers on the Mountain Tops
Big telescopes on high mountains, drawing astronomers to some exotic-sounding places. Is it as glamorous as it sounds? Not really, says one astronomer who describes some of the symptoms people suffer at high altitudes.
Ceres Facts for Kids
Bodeīs Law predicted a planet between Mars and Jupiter. The Sky Police were looking for it, but Giuseppe Piazzi found it. Then someone found another one. And another one. We know of hundreds of thousands of asteroids now. Discover Ceres - planet, asteroid and dwarf planet.
Chemical Cosmos - book review
"The Chemical Cosmos: A Guided Tour" is an astronomy book about chemistry - or perhaps a chemistry book about astronomy. Itīs an engrossing guided tour that will take you from the baby Universe through the first stars, the formation of solar systems and to our search for the origins of life.
Earth & Moon
Our home. And our close companion, object of awe, subject of poetry and the only other world on which humans have walked. What do we know about it?
Exploring Stars and Planets - book review
Looking for an astronomy book for readers 8-14? Philipīs has a brand new edition of Ian Ridpathīs best seller. Clearly written and illustrated with up-to-date images, itīs the story of the Solar System. But there are also glimpses into galaxies, exploding stars and the history of the Universe.
Millions of people have followed the treks of the Martian rovers Spirit and Opportunity as they explored the red planet. In 2009 Spirit became trapped and was last heard from in March 2010. After a year being unable to contact her, on May 24, 2011, with sadness, NASA formally ended her mission.
How to Tell a Planet from a UFO
Two English policemen chased a UFO through the Devon countryside. It was the planet Venus. A news reporter had quite a scoop when she found a UFO hovering over New York City. It was the planet Jupiter. Why are planets and stars often mistaken for spacecraft or aircraft?
One planet in the Solar System dominates the others, so it's fitting that it's named for Jupiter, the king of the Roman gods. Jupiter has moons galore and monster storms, and it spins so fast that its day is only ten hours long.
Jupiter Facts for Kids
King of the Roman gods, comet-killer, contains two and a half times the mass of all the other planets put together, has the shortest day of any planet in the Solar System. Itīs Jupiter! Find out more.
Jupiter's Galilean Moons
Four moons circling Jupiter. It was a sensation when Galileo discovered them in the early 17th century - and they're still sensational! One is bigger than a planet. Another seethes with volcanic activity and has mountains taller than Everest. And which one has ocean that could harbor life?
Literary Moons of Uranus
Solar System moons are named from mythology. Except for Uranus - its moons are named from English literature, primarily Shakespeare. How did this come about and what is the connection with the moons of Saturn?
Mars Facts for Kids
The red planet has no little green men, but itīs a fascinating place. It has a mountain three times the height of Everest and a deep valley that dwarfs the Grand Canyon. Although Mars has no liquid water on the surface, if the southern polar icecap melted, it could cover the planet 36 feet deep.
Mercury Facts for Kids
Now that Pluto is a dwarf planet, Mercury is the baby of the planets. Itīs close enough to the Sun for lead and zinc to melt during the day. Yet there may be frozen water in deep craters. Until space probes came along Mercury was a mystery hidden in the Sunīs glare, but thatīs changing!
From ancient times to the present, fifteen Solar System objects have been called planets. But there are only eight planets now. Find out what happened to the other seven and how the planets got their names.
Neptune Facts for Kids
Far beyond Uranus is another blue planet, one named for the Greek sea god. It could well have been named for a god of winds as itīs the windiest place in the Solar System. Here is an update on facts about Neptune, the planet that was discovered using math.
Rhea Moon of Saturn
Rhea was Saturn's wife in classical mythology. Rhea the moon zips around Saturn in four and a half days. Although it has an oxygen atmosphere, we won't be moving there anytime soon. Even in direct sunlight, it's -281 degrees Fahrenheit and the "atmosphere" is similar to a vacuum on Earth.
Saturn Facts for Kids
Saturn is golden in the sky and a telescope shows a ring system to take your breath away. If you could find enough water, Saturn would float, and its moons are amazing. But if you donīt like freezing weather, 1000-mph winds and lightning storms the size of continental USA, donīt plan any visits.
The Transit of Venus - book review
In the north of England in the early 17th century, there was an amazing circle of astronomers. They were well ahead of their time and included the first two people ever to observe a transit of Venus. What ended this brief flowering? Peter Aughton tells the story.
Top Astronomy Stories 2012
What were the big astronomy stories of the year 2012? Here is my choice of the top ten plus a non-story. What do you think?
Transit of Venus - Measuring the Solar System
On June 8, 2004 millions of people witnessed an event that no one still alive had ever seen: a transit of Venus. Another one will occur in June 2012 and then not again for over a hundred years. What is a transit of Venus? How did it help in working out the size of the Solar System?
Uranus and Neptune - Twin Planets
Uranus and Neptune are ice giants and twin planets. They are very similar in many ways, but they aren't identical twins. For example, Uranus orbits lying down and Neptune is much warmer than it should be.
Uranus Facts for Kids
This ice giant is twenty times further from the Sun than we are. It orbits lying on its side so that half the planet can be dark for over twenty years at a time. This is the planet Uranus, discovered by William Herschel in 1871 and nearly named George!
Venus Facts for Kids
Itīs the planet most likely to mistaken for a UFO. It spins backwards on its axis. A day is longer than a year. Itīs Venus! Some call it Earthīs twin, but I think youīll see that we donīt have all that much in common.
Volcanoes - Fire and Ice
A volcano can produce a fiery sky with ash and deadly gases. The biggest one on Earth is Mauna Loa, but it's dwarfed by Olympus Mons on Mars which is three times the height of Everest. There are many volcanoes in the Solar System, including ice volcanoes.
Voyager 1 Gas Giants and a Last Look Homeward
When a rare planetary alignment opened up the outer Solar System, Voyager 1 was sent forth. It observed the gas giants Jupiter and Saturn and their moons. At nearly 4 billion miles from the Sun, the probe turned and took one last picture of home before continuing its journey to the stars.
Whatīs in a Name
Things arenīt always what they seem. Many discoveries arenīt named for - or by - their discoverers. Halley didnīt discover Comet Halley. Kuiper said the Kuiper Belt didn-t exist. The Herschels called Uranus "the Georgian planet" after George III of England, but no one else did.
Why Planets Have Seasons Astronomy Homepage | Editor's Picks Articles | Top Ten Articles | Astronomy Site Map
For people living outside the tropics, June 21st is the longest or shortest day of the year, a solstice. It marks the first day of summer in the northern hemisphere and winter in the southern hemisphere. But why do we have seasons? And do other planets have them?
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