Scientists think that within 10 million years of our solar system’s formation, Bennu’s present-day composition was. An ancient relic of our solar system’s early days, asteroid Bennu has seen more than 4.5 billion years of history. Every two weeks, we have to look in the opposite direction to see the Moon, and the ground beneath our feet is then tilted the opposite way as well. Bennu is a carbon-rich asteroid that is about one-third of a mile (half a kilometer) wide at its equator. The tilted ramp works the same as the tilted “platform” of the Earth beneath our feet. If you turn around, the horizon appears to tilt the opposite way. In front of you, the horizon looks higher on the right and lower on the left. Earth has a tilt of 23.5 degrees on its axis, which means that when we observe the Moon from Earth, it’s a little like we’re standing sideways on a ramp. The tilt of the Moon’s orbit contributes to this, but it’s mostly due to the tilt of our Earth. We call this motion “libration in latitude.”įinally, the Moon appears to tilt back and forth like a metronome. The 5 degree tilt of the Moon’s orbit also causes it to appear to nod, as though it were saying “yes.” The tilt sometimes brings the Moon above Earth’s northern hemisphere, and sometimes below Earth’s southern hemisphere, allowing us to see slightly more of the northern or southern hemispheres of the Moon. We call this motion “libration in longitude.” When the Moon is farthest from Earth and orbiting at its slowest, its rotation gets a little ahead, and we see a bit more of its western side. When the Moon is at its closest to Earth and moving most quickly along its orbital path, the Moon itself doesn’t rotate quite fast enough to keep entirely the same side facing us, and we get to see a little more of the eastern side of the Moon. The Moon’s rate of rotation around its own axis, though, always stays the same. Galaxies are so big and spread out at the ends that even though galaxies bump into each other, the planets and solar systems often don’t get close to colliding.Because the Moon's orbit is not perfectly circular, its distance from Earth and its speed in orbit both change slightly throughout the month. A satellite can also be man-made, like the International Space Station. A satellite can be natural, like Earth or the moon. An object in an orbit is called a satellite. But even if it happened tomorrow, you might not notice. An orbit is a regular, repeating path that one object in space takes around another one. It won’t happen for about five billion years. Our Milky Way galaxy will someday bump into Andromeda, our closest galactic neighbor. Sometimes galaxies get too close and smash into each other. The light that we see from each of these galaxies comes from the stars inside it. They have irregular shapes and look like blobs. And there are also galaxies that aren’t spirals or ovals. Other galaxies are smooth and oval shaped. They have curved arms that make it look like a pinwheel. Comets, such as the comet ISON pictured here, are thought to hold material from the time when the Sun and planets were. Best known for their long, streaming tails, these ancient objects are leftovers from the formation of the solar system 4.6 billion years ago. Some galaxies are spiral-shaped like ours. The Short Answer: Comets are large objects made of dust and ice that orbit the Sun. The universe is a very big place! Credit: NASA, ESA, CSA, and STScI This image covers a patch of sky approximately the size of a grain of sand held at arm’s length by someone on the ground. This is a picture taken by the NASA’s James Webb Space Telescope showing thousands of galaxies. Some scientists think there could be as many as one hundred billion galaxies in the universe. There are so many, we can’t even count them all yet! The Hubble Space Telescope looked at a small patch of space for 12 days and found 10,000 galaxies, of all sizes, shapes, and colors. There are many galaxies besides ours, though. The Milky Way galaxy fills the night sky in this photo. If it’s really dark, far away from lights from cities and houses, you can even see the dusty bands of the Milky Way stretch across the sky. Astrobiology research has a significant impact on how agencies such as the National Aeronautics and Space Administration (NASA) and the European Space Agency. When you look up at stars in the night sky, you’re seeing other stars in the Milky Way. Our galaxy, the Milky Way, also has a supermassive black hole in the middle. But where is our solar system? It’s a small part of the Milky Way Galaxy.Ī galaxy is a huge collection of gas, dust, and billions of stars and their solar systems. We live on a planet called Earth that is part of our solar system. A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems, all held together by gravity.
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