In fact, the Solar system contains an immense number of objects. We know of hundreds of thousands of asteroids , and think there may be more than ten trillion comets , held in cold storage around the Sun, halfway to the nearest star. Ten trillion is 10,,,, Of the many objects in the Solar system, we think the best places to look for life are those that have liquid water , or had it in the past.
Well, on Earth, everywhere we find water we find life, so it seems natural to search where liquid water is present! Mars is our main target, and we keep sending spacecraft to try to find out if there was ever life there. But there are a growing number of other targets — moons orbiting the giant planets that have vast oceans of liquid water, buried deep underground.
Around Jupiter, we know that Europa , Ganymede and Callisto have oceans, each of which has more water than the Earth. But the Solar system is just one of an immense number of planetary systems. The Sun is one of around billion stars in our galaxy, the Milky Way. What does this mean?
Well, if we guess that each star has eight planets like the Sun , then if there are ,,, stars in the galaxy, there will be 3. But there are many more galaxies out there. In fact, scientists think that there could be 3. How big is that number? Well, that means there are more than a million planets in the universe for every single grain of sand on our planet. There are simply so many places that could have life that I, personally, think there must be a ginormous number of inhabited planets through the universe.
Probably billions, trillions, or even quadrillions! Hello, curious kids! Ask an adult to send your question to us. You can:. Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! Collimation Aligning the optical elements of a telescope so that they all point in the proper direction. Most reflectors and compound telescopes require occasional collimation in order to produce the best possible images.
When close to the Sun, the warmth evaporates the ice in the nucleus to form a coma cloud of gas and a tail. Named for their discoverers, comets sometimes make return visits after as little as a few years or as long as tens of thousands of years. Compound Telescope A telescope with a mirror in the back and a lens in the front.
Conjunction When the Moon or a planet appears especially close either to another planet or to a bright star. Constellation A distinctive pattern of stars used informally to organize a part of the sky. There are 88 official constellations, which technically define sections of the sky rather than collections of specific stars. Culmination The moment when a celestial object crosses the meridian and is thus at its highest above the horizon. Dark adaptation is rapid during the first 5 or 10 minutes after you leave a well-lit room, but full adaptation requires at least a half hour — and it can be ruined by a momentary glance at a bright light.
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The celestial equivalent of latitude, denoting how far in degrees an object in the sky lies north or south of the celestial equator. Dobs provide more aperture per dollar than any other telescope design. Double Star Binary Star Two stars that lie very close to, and are often orbiting, each other. Many stars are multiples doubles, triples, or more gravitationally bound together.
Usually such stars orbit so closely that they appear as a single point of light even when viewed through professional telescopes. Earthshine Sunlight reflected by Earth that makes the otherwise dark part of the Moon glow faintly.
Eccentricity The measure of how much an orbit deviates from being circular. Eclipse An event that occurs when the shadow of a planet or moon falls upon a second body.
The Sun, Stars, and Galaxies by Michael Anderson
Ecliptic The path among the stars traced by the Sun throughout the year. The Moon and planets never stray far from the ecliptic. Elongation The angular distance the Moon or a planet is from the Sun. The inner planets of Mercury and Venus are best seen when at maximum elongation, and thus are highest above the horizon before sunrise or after sunset.
Ephemeris A timetable with celestial coordinates that indicates where a planet, comet, or other body moving in relation to background stars will be in the sky. Its plural is ephemerides pronounced eff-uh-MEHR-ih-deez. On an equinox date, day and night are of equal length.
Eyepiece The part of a telescope that you look into. Field of View The circle of sky that you see when you look through a telescope or binoculars.
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Generally, the lower the magnification, the wider the field of view. Finderscope A small telescope used to aim your main scope at an object in the sky. Finderscopes have low magnifications, wide fields of view, and usually crosshairs marking the center of the field. Focal Length The distance usually expressed in millimeters from a mirror or lens to the image that it forms. In most telescopes the focal length is roughly equal to the length of the tube. Histogram A plot of the number of pixels in an image at each brightness level.
Inclination The angle between the plane of an orbit and a reference plane. Libration A slight tipping and tilting of the Moon from week to week that brings various features along the limb into better view. Light Pollution A glow in the night sky or around your observing site caused by artificial light. It greatly reduces how many stars you can see. Special light-pollution filters can be used with your telescope to improve the visibility of celestial objects. Light-year The distance that light moving at about , miles per second travels in one year, or about 6 trillion miles.
Magnification power The amount that a telescope enlarges its subject. Magnitude A number denoting the brightness of a star or other celestial object. The higher the magnitude, the fainter the object. For example, a 1st-magnitude star is times brighter than a 6th-magnitude star. Meridian The imaginary north-south line that passes directly overhead through the zenith. Messier object An entry in a catalog of star clusters, nebulas, and galaxies compiled by French comet hunter Charles Messier mess-YAY between and The modern-day Messier catalog contains objects.
Milky Way A broad, faintly glowing band stretching across the night sky, composed of billions of stars in our galaxy too faint to be seen individually. Mount The device that supports your telescope, allows it to point to different parts of the sky, and lets you track objects as Earth rotates. Dark nebulas are not lit up and are visible only because they block the light of stars behind them.
Occultation When the Moon or a planet passes directly in front of a more distant planet or star. A grazing occultation occurs if the background body is never completely hidden from the observer. Opposition When a planet or asteroid is opposite the Sun in the sky. At such times the object is visible all night — rising at sunset and setting at sunrise. Parallax The apparent offset of a foreground object against the background when your perspective changes.
At a given instant, the Moon appears among different stars for observers at widely separated locations on Earth. Astronomers directly calculate the distance to a nearby star by measuring its incredibly small positional changes its parallax as Earth orbits the Sun. Phase The fraction of the Moon or other body that we see illuminated by sunlight.
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