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May 9, 2017
Astronomy is the scientific study of objects in the universe and the events that shape them.
“Desiderata.”
“You are a child of the universe, no less than the trees and the stars; you have a right to be here.”
Astronomers use the term astronomical unit (shortened to AU) to define the distance between Earth and the Sun. It’s equivalent to 149 million kilometers (93 million miles). (Astronomy is done in metric units.) So,
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The light-year (shortened to ly) comes from multiplying the speed of light, 300,000 kilometers per second, by the total seconds in a year. The result is the distance light travels in a year: 9.5 trillion kilometers.
Astronomers also use the term parsec (or pc for short). One parsec equals 3.26 light-years.
Pleiades star cluster
The seven sisters
The nearest spiral galaxy, called the Andromeda Galaxy, is about 767 kiloparsecs or 2.5 m...
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The limit of the visible universe lies about 14 Gpc away from us (about 45.7 billion light-years).
The speed of light is the fastest velocity that anything can move in the universe. It is generally stated as 299,792,458 meters (186,282 miles) per second, in a vacuum. It has been measured very accurately and is the standard that astronomers and physicists use. However, as light passes through water, for example, it slows down to 229,600,000 meters (140,000 miles) per second. The letter c is shorthand for the speed of light.
When you look out in space, you’re looking back into time. The farther across space you look, the further back in time you see. This means the telescopes and instruments we use to study the cosmos are really time machines.
Spectroscopy gives information about how fast or slow an object is moving, and helps astronomers figure out how far away it is. An object moving toward us shows lines in its spectrum that are blueshifted, or shifted to the blue end of the spectrum. If it moves away from us, then the lines are redshifted —shifted toward the red end of the spectrum. The term redshift is often used to indicate an object’s distance, say a redshift of 0.5. Astronomers notate that as z = 0.5.
It contains the Sun, eight planets, several dwarf planets, comets, moons, and asteroids.
star 8 main planets 10 (and counting) dwarf planets 146 (and counting) moons 4 ring systems Countless comets Hundreds of thousands of asteroids
Planetary scientists often refer to the inner worlds of the solar system as the “terrestrial” planets, from the word terra, which is Latin for “earth.” It indicates worlds that have a similar rocky composition to Earth.
The big outer worlds are called the “gas giants.”
These planets consist mostly of very small rocky cores buried deep within massive spheres made of liquid metallic hydrogen, and some helium, covered by cloudy atmospheres.
The entire solar system is surrounded by a shell of frozen bits of ice and rock called the Oort Cloud.
planet is defined by the International Astronomical Union (IAU) as a celestial body that has its primary orbit around the Sun, has sufficient mass for its own gravity to mold it into a round shape, and has cleared the neighborhood around its orbit by sweeping up all the planetesimals, which means that it’s the only body of its size in its orbit.
Cryovolcanism, where icy material erupts from beneath the surface, occurs mostly on the frozen moons of the outer solar system.
The Sun is actually white, but it appears yellowish because its light travels through our atmosphere, which removes blue and red wavelengths from the incoming light. After we dive below the
The Sun fuses about 620 metric tons of hydrogen to helium each second, and that’s what provides all of the heat and light.
The Sun constantly emits a stream of charged particles called the solar wind. As this wind rushes past Earth, it runs into our magnetosphere. That’s the region of space around Earth that is bound by our magnetic field. Most of the wind slides right on by, but some of the charged particles get caught up in the magnetic field lines. They spiral in toward the polar regions since those areas are where the magnetic field lines originate. The charged particles energize molecules of gas in our upper atmosphere, called the ionosphere. This causes them to glow. That glow is called the aurora. If it
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X-class
class flare
heavy solar outburst causes ionospheric disturbances called geomagnetic storms. These can affect or even shut down communications and global positioning satellites, endanger astronauts in near-Earth space, and in some severe cases, shut down power grids on our planet.
Nearly three-quarters of our planet is covered with water in the form of the global ocean, lakes, and rivers. This is called the hydrosphere. The oceans influence long-term climate patterns and short-term weather changes, and they are a principal part of the carbon cycle—the method that our planet uses to exchange carbon between the atmosphere,
the oceans, and the surface.
How did life get its start here? Where did it begin? It’s hard to answer these questions precisely, but it’s clear the earliest living beings arose from chemical origins. Some suspect it began as mats of organic molecules in shallow ponds. Others suggest that life, which needs water, warmth, and organic (carbon-containing) material to survive, began in the deep oceans around volcanic vents. Still others think that complex organic molecules in our atmosphere were energized by lightning strikes, which sent them down the road toward
and light areas. Those dark areas are often referred to as maria—the plural form of the Latin word mare, which means “sea.” Early Moon watchers thought those regions were watery oceans, but a close look with a telescope or a pair of binoculars shows no water on the surface, just rocky plains. The low-altitude maria formed as volcanic vents called lunar domes emptied out their molten basaltic lava and flooded the surface. The light areas are called the lunar highlands. They are mostly hilly regions that lie at higher altitudes than the maria. The whole surface is peppered with impact craters,
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This also means that your suit would need to shield you from the Sun and radiation hazards. People living on the Moon would
probably live in the Moon, in underground cities sheltered from the harsh surface environment.
The Moon experiences “moonquakes” fairly often. They are thought to be caused by gravitational interactions with Earth, by impacts,
when the surface freezes and thaws.
often hear the adjective lunar used when referring to the Moon’s surface or structure, or missions to the Moon. That term comes from the Latin word Luna, one name for the Roman goddess of the Moon.
The Moon very likely formed about 4.5 billion years ago in a titanic collision between the newborn Earth and a Mars-sized object referred to as Theia.
the rocks on the Moon have characteristics identical to Earth rocks. This means that most (if not all) of the materials that formed the Moon originated as part of Earth.
The Moon also presents a perfect place to do astronomy. During its thirteen-day “night” period, astronomers could aim telescopes to study dim and distant objects without having to worry about light pollution.
You could have automated telescopes there. You'd have to protect them from being blown to smithereens however
Radio astronomers are also excited about having installations that are not disturbed by radio interference from Earth.
fourth rock from the Sun,
representing the god of war in at least a dozen cultures—has
The red surface color, due largely to the presence of iron oxides (rust) in the
Phobos and Deimos,
The core also cooled, which stopped the dynamo action and left Mars with
no way to generate a strong magnetic field.
The same happens on Mars. In the north polar region, spacecraft images show what’s called patterned ground where ice has frozen, softened, and then remelted. In other places where subsurface ice melted, the overlying layers of rock settled in, forming what is called chaotic terrain. The water released during
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the collapse carved out large flow channels.
Mars also experienced tremendous volcanic activity. The largest of its volcanoes—Olympus Mons—rides high atop a thick piece of the crust called the Tharsis Bulge. As the volcano and the bulge built up over time, tectonic stresses cracked the surface. The famous Valles Marineris is one such crack. It stretches across a third of the planet. This system of canyons has also been carved by wind erosion, and there is some evidence that parts of it were eroded by flowing
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biosignatures.
What is a biosignature
Jupiter is orbited by at least sixty-three known moons. The four largest are Io, Europa, Ganymede, and Callisto (in order of their distance from the planet). They were discovered in 1610 by astronomer Galileo Galilei and are called the Galilean Moons in his honor.
