The Moon
Earth's Moon is the brightest and largest object in our night sky. The Moon makes Earth a more livable planet by moderating our home planet's wobble on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humans for thousands of years.The Moon was likely formed after a Mars-sized body collided with Earth several billion years ago.
Earth's only natural satellite is simply called "the Moon" because people didn't know other moons existed until Galileo Galilei discovered four moons orbiting Jupiter in 1610. In Latin, the Moon was called Luna, which is the main adjective for all things Moon-related: lunar.
Despite music that may suggest otherwise, the Moon's far side gets as much sunlight as its near side. Like Earth, the Moon has a day side and a night side, which change as the Moon rotates. The Sun always illuminates half of the Moon while the other half remains dark.
The time it takes for the Moon to rotate once on its axis is equal to the time it takes for the Moon to orbit once around Earth. Thanks to this synchronous rotation, the same side of the Moon always faces our planet. If the Moon did not rotate on its axis at all, or if it rotated at any other rate, then we would see different parts of the Moon throughout the month. The Moon is always half-lit by the sun (except during a lunar eclipse). The side of the Moon facing the Sun appears bright because of reflected sunlight, and the side of the Moon facing away from the Sun is dark. Our perspective on the half-lit Moon changes as the Moon orbits Earth. When the side nearest to us is fully lit, we call this a full Moon. When the far side is fully lit and the near side is dark, we call this a new Moon. When we see other phases, we are looking at the division between lunar night (the dark part) and day (the bright part).
Earth would be a very different world if it had no Moon. The Moon's gravity keeps our planet from wobbling on its axis too much, which helps to stabilize our climate. The Moon also plays an important role in creating Earth's ocean tides.
Image courtesy of Warren Cameron, Carterton, NZside gets as much sunlight as its near side.
Earth's Moon is the brightest and largest object in our night sky. The Moon makes Earth a more livable planet by moderating our home planet's wobble on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humans for thousands of years.The Moon was likely formed after a Mars-sized body collided with Earth several billion years ago.
Earth's only natural satellite is simply called "the Moon" because people didn't know other moons existed until Galileo Galilei discovered four moons orbiting Jupiter in 1610. In Latin, the Moon was called Luna, which is the main adjective for all things Moon-related: lunar.
Despite music that may suggest otherwise, the Moon's far side gets as much sunlight as its near side. Like Earth, the Moon has a day side and a night side, which change as the Moon rotates. The Sun always illuminates half of the Moon while the other half remains dark.
The time it takes for the Moon to rotate once on its axis is equal to the time it takes for the Moon to orbit once around Earth. Thanks to this synchronous rotation, the same side of the Moon always faces our planet. If the Moon did not rotate on its axis at all, or if it rotated at any other rate, then we would see different parts of the Moon throughout the month. The Moon is always half-lit by the sun (except during a lunar eclipse). The side of the Moon facing the Sun appears bright because of reflected sunlight, and the side of the Moon facing away from the Sun is dark. Our perspective on the half-lit Moon changes as the Moon orbits Earth. When the side nearest to us is fully lit, we call this a full Moon. When the far side is fully lit and the near side is dark, we call this a new Moon. When we see other phases, we are looking at the division between lunar night (the dark part) and day (the bright part).
Earth would be a very different world if it had no Moon. The Moon's gravity keeps our planet from wobbling on its axis too much, which helps to stabilize our climate. The Moon also plays an important role in creating Earth's ocean tides.
Image courtesy of Warren Cameron, Carterton, NZside gets as much sunlight as its near side.
The Sun
The Sun's gravity holds the solar system together, keeping everything – from the biggest planets to the smallest particles of debris – in its orbit. The connection and interactions between the Sun and Earth drive the seasons, ocean currents, weather, climate, radiation belts and auroras. Though it is special to us, there are billions of stars like our Sun scattered across the Milky Way galaxy.
The Sun rotates on its axis as it revolves around the galaxy. Its spin has a tilt of 7.25 degrees with respect to the plane of the planets’ orbits. Since the Sun is not solid, different parts rotate at different rates. At the equator, the Sun spins around once about every 25 Earth days, but at its poles, the Sun rotates once on its axis every 36 Earth days.
The Sun has many names in many cultures. The Latin word for Sun is “sol,” which is the main adjective for all things Sun-related: solar.
From our vantage point on Earth, the Sun may appear like an unchanging source of light and heat in the sky. But the Sun is a dynamic star, constantly changing and sending energy out into space. The science of studying the Sun and its influence throughout the solar system is called heliophysics.
The Sun is the largest object in our solar system. Its diameter is about 1.4 million kilometres. Even though the Sun is the center of our solar system and essential to our survival, it’s only an average star in terms of its size. Stars up to 100 times larger have been found. And many solar systems have more than one star. By studying our Sun, scientists can better understand the workings of distant stars.
The hottest part of the Sun is its core, where temperatures top 15 million °C). The part of the Sun we call its surface – the photosphere – is a relatively cool 5,500 °C. In one of the Sun’s biggest mysteries, the Sun’s outer atmosphere, the corona, gets hotter the farther it stretches from the surface. The corona reaches up to 2 million °C – much, much hotter than the photosphere.
The Sun is about 150 million kilometres from Earth. Its nearest stellar neighbour is the Alpha Centauri triple star system: red dwarf star Proxima Centauri is 4.24 light-years away, and Alpha Centauri A and B – two sunlike stars orbiting each other – are 4.37 light-years away. A light-year is the distance light travels in one year, which equals about 9.5 trillion kilometres.
The Sun's gravity holds the solar system together, keeping everything – from the biggest planets to the smallest particles of debris – in its orbit. The connection and interactions between the Sun and Earth drive the seasons, ocean currents, weather, climate, radiation belts and auroras. Though it is special to us, there are billions of stars like our Sun scattered across the Milky Way galaxy.
The Sun rotates on its axis as it revolves around the galaxy. Its spin has a tilt of 7.25 degrees with respect to the plane of the planets’ orbits. Since the Sun is not solid, different parts rotate at different rates. At the equator, the Sun spins around once about every 25 Earth days, but at its poles, the Sun rotates once on its axis every 36 Earth days.
The Sun has many names in many cultures. The Latin word for Sun is “sol,” which is the main adjective for all things Sun-related: solar.
From our vantage point on Earth, the Sun may appear like an unchanging source of light and heat in the sky. But the Sun is a dynamic star, constantly changing and sending energy out into space. The science of studying the Sun and its influence throughout the solar system is called heliophysics.
The Sun is the largest object in our solar system. Its diameter is about 1.4 million kilometres. Even though the Sun is the center of our solar system and essential to our survival, it’s only an average star in terms of its size. Stars up to 100 times larger have been found. And many solar systems have more than one star. By studying our Sun, scientists can better understand the workings of distant stars.
The hottest part of the Sun is its core, where temperatures top 15 million °C). The part of the Sun we call its surface – the photosphere – is a relatively cool 5,500 °C. In one of the Sun’s biggest mysteries, the Sun’s outer atmosphere, the corona, gets hotter the farther it stretches from the surface. The corona reaches up to 2 million °C – much, much hotter than the photosphere.
The Sun is about 150 million kilometres from Earth. Its nearest stellar neighbour is the Alpha Centauri triple star system: red dwarf star Proxima Centauri is 4.24 light-years away, and Alpha Centauri A and B – two sunlike stars orbiting each other – are 4.37 light-years away. A light-year is the distance light travels in one year, which equals about 9.5 trillion kilometres.
The Sun is located in the Milky Way galaxy in a spiral arm called the Orion Spur that extends outward from the Sagittarius arm. The Sun orbits the center of the Milky Way, bringing with it the planets, asteroids, comets, and other objects in our solar system. Our solar system is moving with an average velocity of 450,000 miles per hour (720,000 kilometers per hour). But even at this speed, it takes about 230 million years for the Sun to make one complete trip around the Milky Way.
