Astronomy facts for kids
Astronomy is a natural science that studies everything beyond Earth's atmosphere. It looks at objects like stars, galaxies, planets, moons, asteroids, comets, and nebulae. Astronomers also study big events like supernovae explosions and gamma ray bursts. This includes understanding the physics and chemistry of these objects and events.
A related field, physical cosmology, studies the entire Universe and how it has changed over time. The word "astronomy" comes from Greek words meaning "star" and "law." Someone who studies astronomy is called an astronomer.
Astronomy is one of the oldest sciences. Long ago, people used stars to find their way and know when to plant crops. Today, there are two main types of astronomy: observational and theoretical. Observational astronomy uses telescopes and cameras to look at space objects. Theoretical astronomy uses math and computer models to guess what might happen. Both types often work together.
It's important to know that astronomy is different from astrology. Astrology is the belief that stars and planets affect human lives, which is not a science.
Contents
Exploring the History of Astronomy
Ancient Discoveries of the Cosmos
Early astronomers used only their eyes to study the stars. They made maps of constellations and stars for religious reasons. These maps also helped them figure out the time of year. Ancient civilizations like the Maya and Ancient Egyptians built simple observatories. They also started thinking about Earth's place in the universe.
For a long time, people thought Earth was the center of everything. They believed the planets, stars, and Sun all moved around it. This idea was called the geocentric model of the Universe.
Ancient Greeks tried to explain how the Sun and stars moved. They took careful measurements. A mathematician named Eratosthenes was the first to measure Earth's size. He also proved that Earth is a sphere. Another mathematician, Aristarchus, suggested that the Sun was at the center. He thought Earth moved around it. This was called the Heliocentric model. But most people still believed in the geocentric model.
Many constellation and star names we use today come from the Greeks. Later, Arabic astronomers made great progress during the Middle Ages. They improved star maps and found new ways to estimate Earth's size.
From Renaissance to Modern Astronomy
During the renaissance, a priest named Nicolaus Copernicus studied how planets moved. He thought Earth was not the center of everything. He said Earth was a planet and all planets moved around the Sun. This idea, called heliocentrism, was actually an old one.
A physicist named Galileo Galilei built his own telescopes. He used them to look closely at stars and planets for the first time. Galileo agreed with Copernicus. Their ideas were also improved by Johannes Kepler and Isaac Newton. Newton invented the theory of gravity. At this time, the Catholic Church disagreed with Galileo. He had to live under house arrest for the rest of his life.
After Galileo, people made better telescopes. They used them to see farther objects like the planets Uranus and Neptune. They also saw that other stars were like our Sun. These stars came in many colors and sizes. Astronomers also saw thousands of other faraway objects, such as galaxies and nebulae.
Astronomy in the Modern Era
The 20th century brought big changes to astronomy. In 1931, Karl Jansky found radio waves coming from space. This started radio astronomy. It was the first time astronomers used a different part of the electromagnetic spectrum to study the sky. Now, parts of the spectrum that Earth's atmosphere didn't block were open for discovery.
This new way of looking at the Universe led to amazing discoveries. For example, pulsars were found. These objects send out regular pulses of radio waves. At first, people thought these pulses might be from aliens because they were so regular!
After World War II, more observatories were built. These places had large, accurate telescopes. They were often run by governments in good viewing spots. For instance, Bernard Lovell started radio astronomy at Jodrell Bank. He used old military radar equipment. By 1957, Jodrell Bank had the world's largest steerable radio telescope.
In the late 1960s, special observatories were built at Mauna Kea in Hawaii. This is a great place for telescopes because it's high up and has clear skies. Mauna Kea now has very large and accurate telescopes, like the Keck Observatory.
The next big change in astronomy came with rockets. This allowed telescopes to be placed in space on satellites.
Space telescopes let humans see the Universe more clearly. Earth's atmosphere blurs images from ground telescopes. This is why stars "twinkle." Pictures from space telescopes, like the Hubble Space Telescope, are much clearer. This is true even if ground telescopes are very large.
Space telescopes also gave access to the entire electromagnetic spectrum. This included X-rays, gamma rays, ultraviolet light, and parts of the infra-red spectrum. These rays had been blocked by Earth's atmosphere. With these new views, many new discoveries were made. Since the 1970s, satellites have been launched to map the sky in almost all parts of the electromagnetic spectrum.
Amazing Discoveries in Astronomy
Astronomical discoveries are usually about two things: bodies and phenomena. Bodies are objects in the Universe, like planets or galaxies. Phenomena are events and happenings in the Universe.
Types of Astronomical Bodies
Astronomical bodies can be found in different places:
Solar System Objects
These are found around stars, like our Sun.
Galactic Objects
These are found inside galaxies.
- Stars
- Diffuse Objects:
- Nebulas (giant clouds of gas and dust)
- Clusters (groups of stars)
- Compact Stars:
- White dwarves (small, dense stars)
- Neutron stars (even denser stars)
- Black holes (areas where gravity is so strong nothing can escape)
Cosmic Objects
These are larger structures in the Universe.
- Galaxies (huge groups of stars)
- Galaxy clusters (groups of galaxies)
- Superclusters (even bigger groups of galaxy clusters)
Astronomical Phenomena (Events)
These are events that happen in space.
- Burst Events: These are sudden, quick changes in the sky, often big explosions.
- Supernovas (huge star explosions)
- Novas (smaller star explosions)
- Periodic Events: These happen regularly, like a repeating cycle.
- Pulsars (spinning neutron stars that send out regular radio pulses)
- Variable stars (stars whose brightness changes over time)
- Noise Phenomena: These signals come from very old events. They seem to come from everywhere and don't change much. The most famous example is:
- Cosmic background radiation (leftover heat from the Big Bang)
How Astronomers Study Space
Instruments for Observation
- Telescopes are the main tools for observing. They gather light from a large area and focus it into a small area. This makes distant, dim objects look bigger, closer, and brighter.
- Spectrometers study the different wavelengths of light. This helps astronomers figure out what something is made of.
- Many telescopes are in satellites. These are called space observatories.
Techniques for Better Views
Astronomers use special techniques to get clearer pictures of space. When light from a distant source reaches a sensor, it's measured. For very dim sources, there might not be enough light to see them. One technique to make them visible is integration.
Integration (Longer Exposures)
Astronomical objects don't move much in the sky. As light particles hit a camera over time, they land in the same spot. This makes the object brighter and easier to see than the background. Telescopes can track objects as they move across the sky. This makes the object appear still to the telescope. This allows for very long exposures, sometimes hours, days, or even months. In the digital age, computer programs can combine many digital pictures. They correct for movement and stack the images to make them brighter.
Aperture Synthesis (Combining Telescopes)
With radio telescopes, smaller telescopes can be linked together. They work as one giant telescope. Its size is like the distance between the two farthest small telescopes.
Adaptive Optics (Clearer Images)
Adaptive optics means changing the shape of a telescope's mirror or lens. This is done while looking at an object. It helps to correct for blurring caused by Earth's atmosphere, making images much clearer.
Fields of Astronomy by Object
Solar Astronomy (Our Sun)
Solar astronomy is the study of the Sun. The Sun is our closest star, about 92 million miles away. It's the easiest star to study in detail. Learning about our Sun helps us understand how other stars work and form. Changes in the Sun can even affect Earth's weather and climate. The Solar wind, a stream of charged particles, constantly flows from the Sun. When the Solar Wind hits Earth's magnetic field, it causes the northern lights. Studying the Sun also helped scientists understand how nuclear fusion works.
Planetary Astronomy (Planets and More)
Planetary Astronomy studies planets, moons, dwarf planets, comets, and asteroids. It also looks at other small objects that orbit stars. The planets in our own Solar System have been studied deeply by many spacecraft. Examples include Cassini-Huygens (which visited Saturn) and the Voyager 1 and 2 probes.
Galactic Astronomy (Distant Galaxies)
Galactic Astronomy is the study of distant galaxies. Studying faraway galaxies helps us learn about our own galaxy, the Milky Way. It's hard to observe our own galaxy because of all the gas and stars inside it. Galactic Astronomers try to understand how galaxies are built and how they form. They use different types of telescopes and computer simulations.
Fields of Astronomy by Light Type
Radio Astronomy (Radio Waves)
- Radio telescopes are used in this field.
Magnetohydrodynamics (MHD)
Hydrodynamics is used in astronomy to create mathematical models of how gases behave. Strong magnetic fields around many space objects can greatly change how these gases act. This affects everything from how stars form to how gases flow around dense stars. This makes MHD a very important tool in astronomy.
Other Special Fields
Gravitational Wave Astronomy
Gravitational wave astronomy studies the Universe using gravitational waves. So far, almost all astronomy has used the electromagnetic spectrum (light, radio waves, etc.). Gravitational Waves are ripples in spacetime. They are made by very dense objects changing shape. These objects include white dwarves, neutron stars, and black holes. Because gravitational waves are so hard to detect directly, this field is still quite new.
See Also
In Spanish: Astronomía para niños
- Solar system
- Planet
- Satellite (natural) (word for moons of other planets)
- Comet
- Meteor
- Asteroid
- Star
- Black hole
- Galaxy
- Universe
- List of comets
Images for kids
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The Paranal Observatory of European Southern Observatory is shooting a laser guide star to the Galactic Center.
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Astronomical Observatory, New South Wales, Australia 1873.
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A celestial map from the 17th century, by the Dutch cartographer Frederik de Wit.
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The Suryaprajnaptisūtra, a 6th-century BC astronomy text of Jains at The Schoyen Collection, London. Above: its manuscript from c. 1500 AD.
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Greek equatorial sundial, Alexandria on the Oxus, present-day Afghanistan 3rd–2nd century BC.
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An astronomical chart from an early scientific manuscript, c. 1000.
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The Very Large Array in New Mexico, an example of a radio telescope.
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ALMA Observatory is one of the highest observatory sites on Earth. Atacama, Chile.
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X-ray jet made from a supermassive black hole found by NASA's Chandra X-ray Observatory, made visible by light from the early Universe.
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This image shows several blue, loop-shaped objects that are multiple images of the same galaxy, duplicated by the gravitational lens effect of the cluster of yellow galaxies near the middle of the photograph. The lens is produced by the cluster's gravitational field that bends light to magnify and distort the image of a more distant object.
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Mz 3, often referred to as the Ant planetary nebula. Ejecting gas from the dying central star shows symmetrical patterns unlike the chaotic patterns of ordinary explosions.
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An ultraviolet image of the Sun's active photosphere as viewed by the TRACE space telescope. NASA photo.
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The black spot at the top is a dust devil climbing a crater wall on Mars. This moving, swirling column of Martian atmosphere (comparable to a terrestrial tornado) created the long, dark streak.
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