AK Learning Box

  Types of Galaxies A galaxy is a huge collection of gas, dust, and billions of stars all held together by gravity. All galaxies are made up of these same things. However, they come in many different shapes and sizes. Here are a few types of galaxies: Spiral galaxies  look like giant pinwheels. The arms of the pinwheel are made up of stars and lots of gas and dust. Gas and dust are some of the main ingredients needed to form new stars. Young stars burn much hotter than older stars, so spiral galaxies are often some of the brightest in the universe. About 20% of all galaxies are spirals. Our home galaxy, the Milky Way, is a very good example of one. Elliptical galaxies  are shaped like stretched-out circles, or ellipses. Some elliptical galaxies are more stretched out than others. One might look almost perfectly circular. Another one might look long and flat. Elliptical galaxies contain mostly older stars. That means they often aren't as bright as spiral galaxies. They also have ver

  How Does NASA Communicate With Spacecraft? The Short Answer: Spacecraft send information and pictures back to Earth using the Deep Space Network (DSN), a collection of big radio antennas. The antennas also receive details about where the spacecraft are and how they are doing. NASA also uses the DSN to send lists of instructions to the spacecraft. NASA spacecraft are exploring our planet, our solar system and beyond. How do they tell us what they find out there? Spacecraft send information and pictures back to Earth using the  Deep Space Network , or  DSN . The DSN is a collection of big radio antennas in different parts of the world. The DSN complex in Canberra, Australia. There are at least four antennas at each DSN site. Image credit: NASA/CSIRO/Canberra Deep Space Communication Complex There are DSN locations near Canberra, Australia; Madrid, Spain; and Goldstone, California. Those sites are almost evenly spaced around the planet. That means as the Earth turns, we never lose sight

  Where Do Old Satellites Go When They Die? The Short Answer: Two things can happen to old satellites: For the closer satellites, engineers will use its last bit of fuel to slow it down so it will fall out of orbit and burn up in the atmosphere. Further satellites are instead sent even farther away from Earth. Like every other machine, satellites do not last forever. Whether their job is to observe weather, measure greenhouse gases in the atmosphere, or point away from Earth to study the stars, eventually all satellites grow old, wear out, and die, just like old washing machines and vacuum cleaners So what happens when a trusty satellite’s time has come? These days there are two choices, depending on how high the satellite is. For the closer satellites, engineers will use its last bit of fuel to slow it down. That way, it will fall out of orbit and burn up in the atmosphere. The second choice is to send the satellite even farther away from Earth. It can take a lot of fuel for a satelli

  What Is a Light-Year? An image of distant galaxies captured by the NASA/ESA Hubble Space Telescope. Credit: ESA/Hubble & NASA, RELICS; Acknowledgment: D. Coe et al. For most space objects, we use  light-years  to describe their distance. A light-year is the distance light travels in one Earth year. One light-year is about 6 trillion miles (9 trillion km). That is a 6 with 12 zeros behind it! Looking Back in Time When we use powerful telescopes to look at distant objects in space, we are actually looking back in time. How can this be? Light travels at a speed of 186,000 miles (or 300,000 km) per second. This seems really fast, but objects in space are so far away that it takes a lot of time for their light to reach us. The farther an object is, the farther in the past we see it. Our  Sun  is the closest star to us. It is about 93 million miles away. So, the Sun's light takes about 8.3 minutes to reach us. This means that we always see the Sun as it was about 8.3 minutes ago. T

  If it's time for a meteor shower, you won't need a telescope, binoculars, or a high mountain to have a "star gazing" party. You might need a warm sleeping bag and an alarm clock to wake you in the middle of the night. But then just lying down in your own back yard will put you in the perfect spot to enjoy a great show. Meteors A meteor is a space rock—or meteoroid—that enters Earth's atmosphere. As the space rock falls toward Earth, the resistance—or drag—of the air on the rock makes it extremely hot. What we see is a "shooting star." That bright streak is not actually the rock, but rather the glowing hot air as the hot rock zips through the atmosphere. When Earth encounters many meteoroids at once, we call it a meteor shower. Why would Earth encounter many meteoroids at once? Well, comets, like Earth and the other planets, also orbit the sun. Unlike the nearly circular orbits of the planets, the orbits of comets are usually quite lop-sided. As a comet

  Where Does Interstellar Space Begin? The Short Answer: Scientists define the beginning of interstellar space as the place where the Sun’s constant flow of material and magnetic field stop affecting its surroundings. This place is called the heliopause. What is interstellar space? At first glance, the answer seems simple. ‘Inter’ means between. ‘Stellar’ refers to stars. “Easy!” you think, “Interstellar space is the part of space that exists between stars.” Not so fast! Wouldn’t that pretty much mean that all of space is interstellar space? For interstellar space to be something different, then there must be some defined boundary between the space near a star and the space in between stars. But what is that boundary? Look to the solar wind! The solar wind pushes against the particles of interstellar space. Scientists define the beginning of interstellar space as the place where the Sun’s constant flow of material and magnetic field stop affecting its surroundings. This place is called

  The Short Answer: Although humans can't hop into a time machine and go back in time, we do know that clocks on airplanes and satellites travel at a different speed than those on Earth. We all travel in time! We travel one year in time between birthdays, for example. And we are all traveling in time at approximately the same speed: 1 second per second. We typically experience time at one second per second. Credit: NASA/JPL-Caltech NASA's space telescopes also give us a way to  look  back in time. Telescopes help us see stars and  galaxies that are very far away . It takes a long time for the light from faraway galaxies to reach us. So, when we look into the sky with a telescope, we are seeing what those stars and galaxies looked like a very long time ago. However, when we think of the phrase "time travel," we are usually thinking of traveling faster than 1 second per second. That kind of time travel sounds like something you'd only see in movies or science fictio