You may notice that when you are stargazing in your yard at 10:00 every night, the stars appear slightly to the west of where they were the night before. Stars rise 4 minutes earlier every night, and set 4 minutes earlier. Therefore, over the months, the starry night changes. Over the period of a year, […]
Space
Why Do Stars Always Appear To Rise In the East and Set In the West and What Is a Circumpolar Star?
Many of the stars you will see in the night sky follow a path across the sky from horizon to horizon. Circumpolar stars, however, appear to circle the northern and southern celestial poles without ever rising or setting. This is because the celestial sphere appears to rotate on the axis between its poles, in fact, […]
What Would Happen If You Stargazed At the North Pole and Which Stars and Constellations Would You See?
If you were looking at stars from Earth’s North Pole, the terrestrial globe would line up precisely with the celestial globe. Your celestial horizon would mirror the celestial equator. The North Star would be at your zenith, straight above your head. All the other stars in the northern hemisphere of the celestial sphere would appear […]
What Is a Celestial Meridian and How Do You Determine Your Celestial Meridian?
Your celestial meridian is an imaginary line that begins at the northern point of your celestial horizon and travels over your head, through your zenith, and down to the southernmost point of your celestial horizon. The line makes a hemispherical arc from north to south through your zenith. There is no special term for the […]
How Do You Use Your Specific Location on Earth To Reference Your Position On a Celestial Globe?
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 […]
Where Is the North Star, What Is the Name of the North Star, and Will the North Star Always Be the Polestar?
Fortunately for us, the North Star, also known as Polaris, will be the polestar, marking the celestial north pole, during our lifetimes. But this will not always be the case. Earth does not rotate smoothly on its axis. Imagine a spinning top. As the top slows down, it wobbles a little. Instead of its axis […]
What Are Constellations, How Did Constellations Get Their Names, and How Many Constellations Are There?
Constellations are simply groups of stars that people have named for the sake of convenience. People have been mapping constellations for thousands of years, usually naming them after mythological characters or common items that the group of stars resembles. For instance, the constellation Leo looks like a seated lion. If you were to connect the […]
How Do You Use Hand Measurements To Estimate Distances In the Sky While Stargazing?
While stargazing, it is sometimes difficult to estimate distances in the sky. Here are a few helpful shortcuts. Raise your index finger in the air; its width is approximately 1°. Make a fist and raise it to the sky: the width is about 10°. If you spread out your fingers against the background of the […]
What Is a Celestial Globe, Who Invented the Armillary Sphere, and What Does Armillary Mean In Latin?
Just as we use a terrestrial globe to show geography on Earth, we can use a celestial globe to locate stars in space. All the visible stars are on the surface of the globe. When you are looking at a celestial globe, you need to imagine yourself inside the globe looking out. Since stars “move” […]
How Do Astronomers Locate Stars On a Celestial Globe Using Declination and Right Ascension?
A celestial globe is marked with imaginary vertical and horizontal lines called declination (dec) and right ascension (RA). These lines correspond to latitude and longitude lines on a terrestrial globe. Just as you can locate a town by finding the intersection of its latitude and longitude, Sonora, Texas, sits approximately at 30° north latitude and […]
What Is Right Ascension and How Do Astronomers Determine a Star’s Right Ascension Using the Celestial Equator?
Right ascension, or RA for short, is the astronomical term for the location of an object on the celestial sphere when using the equatorial coordinate system. On the terrestrial globe we use longitude lines to express east-west location on Earth. The prime meridian and the International Date Line are the imaginary vertical lines splitting Earth […]
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 […]
What Is a Stargazer’s Zenith and What Does the Word Zenith Mean In Arabic?
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, […]
What Is the Celestial Horizon and How Is the Celestial Horizon Different Depending On Your Location?
When you are stargazing, the farthest you can see along the ground in any direction is called your celestial horizon. Just as the Sun rises over the horizon, so do all stars appear to rise and set over your celestial horizon. On a map, your celestial horizon corresponds to Earth’s horizon around you, but when […]
How Is Temperature Measured In Space and Who Invented the Kelvin Scale For Temperature?
Astronomers can measure temperature in space by studying various electromagnetic radiation waves. In the United States, the Fahrenheit (F) scale is usually used to measure temperature. Most of the rest of the world uses the Celsius (C) scale. Scientists, however, use the Kelvin (K) scale, also known as absolute temperature. In 1848, Lord Kelvin, also […]
What Is Einstein’s Theory of Special Relativity and When Was the Theory Proposed By Albert Einstein?
While Isaac Newton’s laws of motion and gravity still have validity as a working model for basic astronomy, physicists rely on Albert Einstein’s complex relativity theories in their advanced work. The special theory of relativity, or STR for short, is the physical theory of measurement in inertial frames of reference proposed in 1905. In Einstein’s […]
Who Discovered Microwaves, Where Do Microwaves Come From, and How Are Microwaves Important In Astronomy?
Microwaves are not only found in ovens. In 1964, scientists Arno Penzias and Robert Wilson recorded microwaves emanating from every direction in the universe. Penzias and Wilson determined that their source was probably the entire universe. The waves came from everywhere. The only source that can be considered everywhere at once is the universe, if […]
What Are Celestial Objects, Where Do They Come From, and What Does the Word Celestial Mean In Latin?
Unless you are blinded by the bright lights of a city, the nighttime sky will show you bright lights of its own. The lights in the sky are objects emitting electromagnetic waves that we see as light. Lumped together, these objects, mostly stars, planets, satellites, comets, galaxies, and meteors, are often called celestial objects, or […]
How Do You Tell the Difference Between All the Stars In the Sky Without a Telescope or Binoculars?
There are many ways to look at the night sky. The most obvious is to stand outside and look up. On a clear, dark night, the sky, what astronomers call the celestial sphere, appears filled with individual points of light. Only by studied, careful observation can you distinguish a star from a planet or one […]
What Is a Celestial Sphere and How Is the Celestial Sphere Important In Positional Astronomy?
Even though we know that the heavens do not rotate around Earth, it only appears so because Earth is rotating on its axis, astronomers find this image useful in locating stars, planets, galaxies, and comets. The starry sky looks like a dome high above Earth. Imagine this dome completely surrounding Earth, as if Earth were […]
How Do Stars Move Across the Universe and Why Do Stars Move Across the Sky At Night?
Traditionally, people have thought of the stars as immovable and permanent, but they do move. We know the stars move because we know that the universe is expanding. But Earth is also moving in the expanding universe, so the movement of the stars is imperceptible, you can’t see it. “Wait a minute,” you might say. […]
What Is Light Made Of, Where Does Light Come From, and Why Is Light a Type of Electromagnetic Radiation?
Light is a familiar everyday phenomena that we take for granted. When the Sun or other stars shine, we see light. When we turn on a lamp, we see light. Technically, light is an energy disturbance in the air. Oscillating electric and magnetic fields radiate energy in waves. The wavelengths and frequency fall in the […]
How Dangerous Is Radiation and Are All Types of Radiation Dangerous or Hazardous To Our Health?
There are several types of electromagnetic radiation such as, radio waves, infrared light, visible light, ultraviolet light, and X-rays. Some radiation from elements can be deadly. The bombs that the United States dropped on Hiroshima and Nagasaki, Japan, at the end of World War H, were hydrogen and plutonium bombs, respectively. The radiation from other […]
What Is a Radio Telescope and How Do Radio Telescopes Help Astronomers Detect Objects In the Universe?
The word “telescope” generally refers to an optical telescope. But instruments designed to collect radio waves are called radio telescopes or radio dishes. Radio telescopes are basically directional radio antenna used in radio astronomy. Radio telescopes operate in the radio frequency portion of the electromagnetic spectrum where they can detect and collect data on objects […]
What Are Infrared Rays and Why Do Astronomers Use Infrared Telescopes To Detect Objects In the Universe?
Infrared rays are long, heat-intensive wavelengths that we cannot see. Telescopes outfitted with heat-sensitive reflectors, instead of mirrors or lenses, gather infrared rays, which are reproduced visually by special photographic equipment. The infrared image of an object is similar to what you see if you put your hand against a very cold window. An outline […]
What Is Radiation, Which Objects Emit Radiation, and How Is the Wavelength of Radiation Measured?
Radiation is energy emitted by a source such as a planet, star, or your own body. We measure radiation in wavelengths. Radiation travels in rising and falling motions called waves, like waves in the ocean. Wavelengths are measured from the tip of one wave to the tip of the next. Our eyes can register light […]
Why Is Light White and How Do You Separate Light Into the Various Colors of the Spectrum?
We often refer to so called pure light as white, but light comes in a variety of colors depending on the length and speed, or frequency, of its waves. When light travels through a prism, or a solid, multisided chunk of glass, it is separated into its various colors, known as the spectrum. This separation […]
How Can An Object Emit More Than One Type of Radiation and Which Animals Can See Ultraviolet Radiation?
Many objects usually emit more than one type of radiation simultaneously. For instance, the Sun radiates everything from gamma rays to radio waves. People emit radio waves, but we can’t detect those waves without the proper receiving equipment. You’d have to use a radio telescope to do so, but all the other radio waves bouncing […]
What Are Radio Waves and What Do Radio Waves Have To Do With Radios and Astronomy?
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 […]
How Do You Make Your Own Rainbow At Home and Create a Spectrum of Colors With Light?
You have probably seen a rainbow, or light separating into colors through a cut-glass window. You can make your own color spectrum reflect on a wall or ceiling this way. Lean a mirror against the far end of a shallow pan filled with water, the whole mirror does not have to be underwater. Position the […]
Why Is Electromagnetic Radiation Described As Waves and Rays and What Is The Difference Between Them?
All radiation travels outward from its source in a wave-like pattern. The term ray is commonly used to describe the rapid, short waves of the upper part of the electromagnetic spectrum: gamma rays, X rays, ultraviolet rays, light rays, and infrared rays. A ray is the straight line along which the waves travel. Slower radiation, […]
What Is an Astronomical Unit and How Is the Astronomical Unit Used To Measure Distances In Space?
The astronomical unit (AU) measures the relatively short distances within our solar system. One AU is the mean distance from Earth to the Sun, about 93 million miles. We can say that Pluto’s average distance from the sun is 40 AUs rather than saying it is 3.72 billion miles. The units of light-years and parsecs […]
What Is a Light Year and How Long Does the Light From Our Closest Star Alpha Centauri Take To Reach Earth?
Perhaps the most common measure of space is the light-year. Strangely enough, a light-year can measure both time and space. Many people believe that time and space are inseparable, simply two sides of the same coin. It takes time for light to travel. Light’s unvarying speed in space is about 186,000 miles (297,600 km) per […]
What Are Newton’s Laws of Motion and Gravity and How Does Mass Affect an Object’s Gravitational Pull?
Much of astronomy deals with the physical laws of motion and gravity, which Sir Isaac Newton described in the seventeenth century. Newton’s laws of motion are: 1. Every body of matter remains at rest until it is moved by an external force. 2. When an external force compels an object to move, that object will […]
What Is a Parsec, How Long Is a Parsec, and Who Invented the Parsec As a Unit of Measurement?
A parsec (pc) is a measure of incredibly large astronomical distance. The word comes from the phrase parallax second. Parallax means the change in a star’s relative position in the sky when viewed from different places, and second refers to the smallest measurement of the change, stars move in arcs measured in seconds. Imagine a […]
What Is the Electromagnetic Spectrum and What Are the Different Types of Electromagnetic Radiation Called?
The electromagnetic spectrum is the scientific name for all of the types of known radiation in the universe. From shortest (highest frequency) to longest (lowest frequency) wavelengths, they are: Gamma rays, X rays, ultraviolet rays, visible light rays, infrared rays, and radio waves, which include microwaves, television and FM radio waves, shortwaves, and AM radio […]
When Was the First Telescope Invented and How Did Hans Lippershey Invent the First Optical Telescope?
At the beginning of the seventeenth century, Hans Lippershey, a Dutch eyeglass maker, discovered that when he looked through two lined-up lenses at different ends of a long tube, distant objects appeared closer and larger. He was probably not the only one to make this discovery, but his name has come down through history. Lippershey […]
How Did Astronomical Telescopes Evolve To Become Bigger and More Powerful To See Deeper Into Space?
Galileo built many telescopes, each more powerful than the last, and in 1609 he was the first to use the instrument, called “Galileo’s ladder”, to study the sky. The great astronomer Sir Isaac Newton modified Galileo’s telescope by using mirrors instead of lenses. A musician and amateur astronomer named William Herschel, who discovered the planet […]
How Does a Simple Refracting Telescope Work and When Was the Cassegrain Reflecting Telescope Invented?
Let’s say we are looking at the Moon through a refracting telescope. Light from the Moon is gathered by the objective lens, which sits at the open end of the telescope. As the light enters the lens, it is bent just as light bends when it goes through water or a prism. The light bends […]
Why Was the Telescope Invented and What Are Optical Telescopes Used For?
Most of what we know about the universe comes from the study of light from space objects. The general purpose of a telescope is to gather light from objects in the sky, making them larger, brighter, and clearer so that we can study them in detail. Two major types of optical telescopes are used to […]
What Factors Determine the Power of an Optical Telescope and Why Is the Diameter of the Lens Important?
The size of the objective lens in a refracting telescope, or the primary mirror in a reflecting telescope, and the distance the light travels through the telescope’s tube are the most important elements in determining the power of the telescope. The diameter of a lens or mirror is called the aperture; the larger the aperture, […]
How Do Astronomers Measure Really Big Distances and Why Were Astronomical Units Invented To Express Distance?
Everyone relies on numbers to express distance, but when distances are immense, too many digits have to be used to make sense. For example, the distance between Los Angeles and New York is 14,710,080 feet, or 2,786 miles (5,280 feet = 1 mile). We don’t have to use as many digits in miles as in […]
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. […]
When Did Polish Astronomer Nicolaus Copernicus Propose That the Earth Rotated Around the Sun and Why?
The acceptance of the fact that Earth rotated around the Sun was a long time coming. In 1543, the Polish astronomer Nicolaus Copernicus published De Revolutionibus, which stated that the planets revolved around the Sun. His theories, however, disagreed with the teachings of the Roman Catholic Church, and the church was the most powerful social […]
How Did Early Astronomers Distinguish One Star From Another and Map the Locations of Stars In the Sky?
Besides mapping the locations of stars in the sky, astronomers also determined which stars were brighter than others. The Greek astronomer Hipparchus, a predecessor of Ptolemy, first classified stars according to their brightness. He listed six categories of brightness by magnitude. Magnitude defines how bright the stars appear to be from Earth. A star’s magnitude […]
How Did Astronomy Begin and Why Did Claudius Ptolemy Believe That the Earth Was the Center of the Universe?
Before the invention of the telescope in the early seventeenth century, astronomy was based on observations made by the naked eye. First, people mapped the positions of stars and planets in the sky. Most cultures had their own systems for mapping the sky, but astronomy as we know it today has its roots in classical […]
How Does a Reflecting Telescope Work and Who Invented the Reflecting Telescope?
A reflecting telescope uses mirrors, whereas a refracting telescope uses lenses to gather light. Light gathered into a reflecting telescope first travels the length of the telescope’s tube until it reaches a mirror placed at the tube’s end. The light bounces off that mirror, called the primary mirror, and journeys back along the tube to […]
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 […]
Where is the Planet Vulcan Located, How did Vulcan Get its Name, and Does the Planet Vulcan Really Exist?
In 1845, some astronomers believed that the only explanation for Mercury’s confusing and erratic orbit of the sun would be the presence of gravitational pull from an unseen nearby planet, which they named “Vulcan.” French mathematician Le Verrier, who came up with the hypothesis to explain Mercury’s orbit, died in 1877, still convinced of having […]
What Is A Solar Flare?
A solar flare is a large explosion in the Sun’s surface that can release intense amounts of radiation. The radiation emitted by solar flares can affect the Earth’s ionosphere and disrupt radio communications on earth. Solar winds are the steady flow of electrically charged particles sent out by the sun. Did you know that there […]
How Often Do Asteroids Hit the Earth?
Asteroids are actually very tiny planets which revolve in orbit around the sun. Thousands have been seen by astronomers and many have been named. But new asteroids are being discovered almost daily. Sometimes, because of the attraction of other planets, these asteroids change their orbit and collide with other asteroids. The fragments that break off […]