What Is the Solar System and How Many Planets Are There In the Solar System? Generally, the solar system could be said to contain everything that revolves around the Sun, which lies at its center, hence its name, solar means “sun”. The solar system is made up of comets, meteors, and dust; the minor planets, […]
Luminosity (L) is the measure of energy, or power emitted by a star. It is measured the same way we measure the energy output of a lightbulb. Lightbulbs come in different strengths: 40 watts, 60 watts, or 100 watts, for instance. A watt is a unit of energy emission. The Sun’s luminosity, or energy output, […]
What Is Astronomy, What Does Astronomy Mean In Greek, and Why Is the Study of Astronomy Important To Us?
Astronomy is the study of matter and processes that exist primarily beyond Earth’s atmosphere. It covers the whole universe, the heavens, the celestial sphere, from microscopic atoms to the vast cosmos. Astronomers study the heavenly or celestial bodies such as planets, stars, comets, galaxies, nebulae, and intergalactic material to determine how they formed, how they […]
There are two kinds of time in astronomy, solar time and sidereal time. Ordinary clocks, and most people on earth use solar time, based on Earth’s rotation and orbit in relation to the Sun. The foundation of sidereal time is Earth’s rotation only, in relation to stars other than the Sun. Neither method of keeping […]
What Is the Ionosphere, What Is the Temperature of the Ionosphere, and How High Is the Ionosphere Above Earth?
The ionosphere layer of the atmosphere overlaps the mesosphere and thermosphere and is the uppermost part of the atmosphere. The temperature of the ionosphere ranges from about 200K, or -73 ºC (-99.4 ºF) to 500K, or 227 ºC (440.6 ºF). So basically at the bottom it is 200K. At the top it is 500K. K […]
What Is the Difference Between Planets, Planetesimals, and Asteroids, and How Did the Kuiper Belt Get Its Name?
Some comets may come from the Kuiper Belt, but most probably originate in the Oort Cloud. The celestial bodies in the Kuiper Belt, however, prompt debate over the differences between planets, planetesimals, and asteroids. Astronomer Gerard Kuiper studied the satellites of the outlying planets and, in the 1940s, discovered the moons Miranda and Nereid of […]
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves certainly have a lot to do with radios and astronomy. People cannot see radio waves without re-creating them in a visual format, such as by electronically digitizing the waves in a computer, which in turn […]
What Is a Comet Made of, Why Do Comets Have Irregular Shapes, and What Does the Word Comet Mean In Latin?
A comet is often described as a dirty snowball. A comet’s nucleus, or solid core is, in fact, made of 50 percent dust and gases, and 50 percent ice. The dust is made up of rock and metal; the ice is actually frozen gas. Both are believed to be left over from when the solar […]
Where Did the Moon Come From, How Did Earth Get Its Only Satellite, and How Long Ago Was the Moon Created?
There are many theories about how the Moon formed. The current favorite says that a huge asteroid, maybe the same one that is thought to have tilted Earth’s axis, hit Earth, throwing off a mass of debris into a broken ring around the planet. Over time, the debris coalesced, creating the Moon. At first the […]
Summer in the southern hemisphere causes the most weather activity on Mars. The temperature increase shrinks the southern polar ice cap, at the same time, the northern ice cap, experiencing winter, grows larger, which increases the air pressure. Increased air pressure causes severe winds to blow toward the equator. The winds can reach up to […]
Tall, vertical streams of gas, called spicules, are like huge fiery geysers shooting up into the Sun’s chromosphere and then disappearing. Spicules are usually associated with regions of high magnetic flux. They rise about 6,000 miles, or 10,000 km and last between 5 and 15 minutes. Spicules were discovered in 1877 by Father Angelo Secchi […]
Meteors are pieces of celestial debris of any size. They can be found just about anywhere in the solar system. Cornets are a great source of meteors because they leave particles along their paths. When Earth orbits through the cometary residue, earthlings can see the dust fall in meteor showers, also known as shooting or […]
When you look up into the night sky, you see only some of the stars on the celestial globe. Some are on the other side of Earth from you, beneath your celestial horizon. To orient, or line up, your stargazing position in reference to the celestial globe, you have to imagine where your celestial horizon […]
How Many Explorer Satellites Were Launched Into Space and What Was the Purpose of the Explorer Space Program?
Sixty-five Explorer satellites, all unmanned, were launched from Earth between 1958 and 1984, seven failed to launch successfully. They were all sent into space to collect data and conduct experiments on specific phenomena. The areas of study included radiation belts, magnetic fields, solar wind, electromagnetic rays, the ionosphere, and Halley’s comet. In the aftermath of […]
Who Was Galileo Galilei and Why Is the Italian Astronomer the Father of Modern Observational Astronomy?
Galileo Galilei seemed to be larger than life. Born in Pisa, Italy, in 1564, at the culmination of the Renaissance, Galileo was not just the first person to focus a telescope on the stars; he also turned the view of the world upside down. Galileo was a master of astronomy, mathematics, physics, philosophy, and publicity. […]
More than 5,000 minor planets, or orbiting asteroids have been cataloged since 1801, when the largest, numbered 1 and named Ceres (1 Ceres), was sighted by Italian astronomer Giuseppe Piazzi. Some 200 more are discovered every year. Astronomers estimate that 50 percent of all asteroids that are 6 miles or larger in diameter have been […]
Why Do We Send New Probes To the Same Planets and How Many New Moons Did Voyager 1 Discover Orbiting Jupiter?
Advances in understanding and technology, as well as the failure of some probes to perform their tasks, make it important to send probes time and again to the same planet. We don’t know what we will find when we receive information from a distant probe. Every probe sent to Jupiter, for example, raises more questions […]
Why Did NASA Put the Hubble Space Telescope In Space and Why Do Space Telescopes Take Sharper Images?
Since telescopes were first used by Galileo in the early seventeenth century, astronomers have dreamed of placing them where Earth’s atmosphere would not get in the way of viewing the universe. The Hubble Space Telescope (HST) fulfills that dream. The Hubble Space Telescope, a reflecting telescope, is not the largest telescope made on Earth. Its […]
How Are We Able See So Much Detail On the Surface Of the Moon and How Do Shadows Help Us Distinguish Features?
The Moon is relatively close to Earth, and so it is the most obvious object in the sky, aside from the Sun. It is also huge for a satellite, being one-quarter the size of Earth. The Moon’s gravity is not strong enough to hold an atmosphere, so there are no winds to fill the craters […]
How Is a Star’s Declination Determined and How Do Astronomers Use Declination To Locate a Star In the Sky?
Declination (dec) on the celestial globe is like latitude on the terrestrial globe. The celestial equator mirrors Earth’s equator, halving the sphere into northern and southern hemispheres at 0°. The degrees of lines of declination increase north and south to 180° at each celestial pole, just like latitudes increase to 180° at the terrestrial North […]
Like Mercury, Venus is relatively close to the Sun. It is often called the evening or morning star because it is so bright at sunset and sunrise. Venus is the brightest planet in the sky, even brighter than the stars; therefore, it is a pretty easy object to find in the night sky. As a […]
Sunspots have great magnetic forces, which fluctuate in intensity and polarity as does Earth’s magnetic field. When the magnetic field of a sunspot loses its stability, it can cause a violent explosion, called a flare. Flares look like sudden brilliant stars within a star, generally lasting less than an hour. The explosion sends shock waves […]
How Many Moons Does the Planet Uranus Have and How Did the Moons Orbiting Uranus Get Their Names? Before the space age, we knew of five satellites orbiting Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. The names came from the works of Shakespeare and the poet Alexander Pope. Ten more moons, discovered by the spacecraft […]
The planet Venus makes one rotation on its axis in 243 Earth days. Its solar day, the time it takes the Sun to reappear in the same place in the sky, is 118 Earth days. On Earth, the two are almost identical, 24 hours, so the Sun rises at approximately the same place every morning. […]
Astronomers don’t always have evidence of a celestial object itself, but must rely on their knowledge of the neighborhood of a suspected object, such as a black hole or neutron star. For instance, they may see a patch of sky where everything, all light, all radiation, appears to be streaming to one point. Perhaps the […]
The 1960s saw a great debate among scientists and the U.S. government as to what kind of vehicle would work best for all three stages of the Apollo mission. The mission required a launch, a visit to the Moon, and a return to Earth. In the end, NASA decided to launch one spacecraft to orbit […]
Particles jettisoned from the Sun during a solar flare or contained in the solar wind can reach Earth in a matter of hours or days. Above Earth’s North and South Poles, the planet’s magnetic field is strongest and the atmosphere is filled with particularly highly charged atoms. The interaction of solar and atmospheric particles results […]
The eleven rings around Uranus are thin bands some 0.6 to 7.0 miles (1 to 11 km) thick. The exception is the farthest edge of the farthest ring, which ranges up to 60 miles (96 km). The rings are composed of extremely dark particles, which vary in size from micrometers to a fraction of a […]
What Is the Ninth Planet From the Sun, How Far Away Is Pluto, and Is Pluto a Planet, a Moon, or an Asteroid?
Some astronomers have questioned whether Pluto should be classified as a planet, rather than an errant moon or an asteroid. The does not generate light; it is less massive than a star; it wanders through constellations; and it orbits the Sun, just like the other planets. Pluto’s orbit, however, is decidedly peculiar. Pluto’s distance from […]
How Do Astronomers Know So Many Details About Mercury and When Did the First Spacecraft Visit Mercury?
Just looking at the planet Mercury doesn’t give astronomers very much information. Fortunately, electromagnetic waves, mostly radio waves, from Mercury are picked up around the world. They have helped establish the topography and composition of Mercury. Also, twice in 1974 and once in 1975, the spacecraft Mariner flew by Mercury and photographed as much of […]
John Glenn wasn’t the first person in space. The honor went to Soviet cosmonaut Yuri Gagarin, on April 21, 1961, almost a year before Glenn orbited the earth. The USSR reported a completely successful 1-hour and 48-minute orbit of the manned capsule Vostok 1. Later it was learned that trouble upon reentry caused the capsule’s […]
How Fast Does Jupiter Rotate On Its Axis and Why Does the Atmosphere On Jupiter Rotate At Different Speeds?
The planet Jupiter’s rotation is the fastest of all the Solar System’s planets. Jupiter does not rotate as a solid body does, all at the same speed, because it is made out of hydrogen and helium. Around the equator, the gas layer of Jupiter has a rotation period of 5 hours, 50 minutes, and 30 […]
Rills are extended crevices on the Moon’s surface. They can run up to at least 150 miles (250 km) and over a mile (1.6 km) wide. The thousands of rills that cut through the Moon’s terrain were probably formed from channels of molten lava. In fluvial geomorphology on earth, a rill is a narrow and […]
Say you are standing in your backyard. If you look straight up over your head, that is your zenith. It is the intersection of the imaginary north, south, east, and west lines rising from the horizon of your field of vision. In general terms, the zenith is the direction pointing directly “above” a particular location, […]
How Fast Do Jupiter’s Moons Orbit the Planet and What Is the Difference In Orbital Period Between the Moons?
Astronomers frequently use orbital period, or how long one revolution takes, to measure speed instead of miles, or kilometers per hour. The three families of satellites are clustered by period as well as distance. Of the four closest moons, none takes more than 1 day to orbit Jupiter. The four Galilean moons, also in the […]
How Are Stars Born, How Are New Stars Formed From Clouds of Dust and Gases, and How Do We Detect New Stars?
Space is full of clouds of dust and gases, known as nebulae. The dust and gases in nebulae have a certain mass, and we know, from Newton’s law of gravity, that any object with mass attracts other objects to it. The dust and gases are gradually pulled toward each other by the force of gravity. […]