Cosmic Cast of Characters (PDF)

Creating A Colorful Cosmos Notes for Surveying the Universe

What’s Out There? Notes & Descriptions Where in the Size Range Notes about Universe? Note: 1 light year = distance Telescope Observing Note: 1 light year = distance that light travels in one year that light travels in one year

These objects (including our own There are eight planets and oodles Bit Players can range from fist and Solar system objects move around The “Bit Players” Earth) are the leftovers from the of comets and asteroids in our own house-size (asteroids) to with respect to the far-away back- formation of a star … solar system, here on the outskirts Jupiter-size (around 10 times ground stars. Planets the Sun in our case. of the Milky Way Galaxy. Earth’s diameter). Much bigger and they no longer qualify as “bits” Because they are relatively close Planets, comets and asteroid orbit Astronomers have discovered -- If Jupiter were much larger, it’s and reflect the Sun’s bright light, Moons their parent star. Moons orbit their nearly 4000 planets around other gravity might cause a high enough exposure times for the moon and own planet. stars, with thousands of other temperature in its core for it to start planets will be short. “candidate” exoplanets still to be glowing on it’s own and become Comets Some of these objects are made confirmed! When you look in the a star! mainly of rocky materials (like the sky, on average every star you see Earth and Mars or asteroids for has at least 1 planet! Asteroids example). Other are mostly made of gas (like the giant planets such The distance between the earth as Jupiter and Saturn). and the Sun is about 10,000 Earths diameters. Light takes 8 minutes to They don’t glow with their own travel that distance. Light travels visible light, but reflect the light the distance between Pluto and the of their star. Sun in a about 5 hours.

www.microobservatory.org Creating A Colorful Cosmos Notes for Surveying the Universe

These are the main source of visible All the stars you see in the night Our sun is a relatively small star: Most stars and star clusters will The Stars light in the universe! Sunlight is sky, and all the stars you will ob- its diameter is about 100 times the require an exposure time of 60 starlight. serve with your on-line telescopes, Earth’s diameter. seconds. are located outside our Solar Individuals Stars are huge balls of gas, such as System but inside our Milky Way Stars range in size from a little Stars come in different colors, Hydrogen and Helium. Galaxy. smaller than our Sun to 50-100 which you can investigate by Double stars times the size of our Sun. Even the taking images through different Because they are so big, the inward The closest stars you will observe largest stars though are so far away colored filters. force of a star’s great gravity causes will be several light- years away: If that they still look like tiny dots in Clusters of Stars: nuclear fusion at its core--the we were traveling at the speed of our telescopes. source of a star’s light & energy. light it would take about 3-4 years Open Clusters for us to reach the closest star to Star clusters, groups of hundred Globular Clusters Telescopes are starlight recorders. our Sun. to hundred thousands of stars, however are pretty big: Open star The farthest globular star clusters clusters range from 10-30 light will be halfway across our Galaxy years across while Globular star tens of thousands of light years clusters can be hundreds of light away. years across.

www.microobservatory.org Creating A Colorful Cosmos Notes for Surveying the Universe

Nebulae are huge clouds of dust Nebulae, like the stars, are These clouds of gas and dust can Unlike stars, nebulae don’t glow as Nebulae and gas. distributed around our Milky Way range from a light year across a result of nuclear fusion. Rather galaxy, beyond our own Solar to tens of light years. Typically they shine in one of 2 ways: they Some nebulae collapse under their System. star-forming clouds are bigger than either scatter or reflect the light Clouds of gas and dust own gravity to form new stars. the star-death remnants of super- of nearby stars; or they absorb Meanwhile, dying stars spew out Most nebulae seen through your novae or “planetary” nebulae. ultra-violet light from nearby stars Star birthplaces (e.g. Orion their newly formed elements in on-line telescopes will range from and “flouresce” like a glowing neon gentle puffs (e.g. the Ring Nebula) hundreds to thousands of light The Orion Nebula is about 24 light gas lamp. Nebula) or in violent explosions called su- years away. years across. The Ring Nebula is pernovae (e.g. the Crab Nebula). about 1 light year across and the Because nebulae are mostly Stellar graveyards (e.g. The Orion nebula is about 1200 Crab Nebula is about 11 light years made of Hydrogen, and hydrogen Interesting fact: The atoms of light years away. The Ring Nebula is across. glows with a red color, you’ll find Crab Nebula or Ring carbon and calcium that make up about 2300 light years away while that nebulae are often brighter Nebula) your skin and bones were once in a the Crab Nebula is about 6500 light through the red filter than through great interstellar cloud out of which years away. the blue. Use long exposure the Solar System formed. Nebulae times to gather the faint light from are indeed the great chemical these diffuse cloudy objects. recycling centers of the universe.

www.microobservatory.org Creating A Colorful Cosmos Notes for Surveying the Universe

Galaxies are huge groups of stars, Everywhere! Our own Milky Way Galaxies are VERY big, on average Because galaxies are very far Galaxies much bigger than star clusters. Galaxy (which we cannot see from about 100,000 light years across. away (millions to billions of light the outside since we are inside) is years) -- they are dim, so you’ll Spiral These cosmic cast members could but one of billions of galaxies that The distance between the Milky need long exposure times. also be called the “Hollywoods of appear to populate the cosmos all Way and Andromeda is equivalent the Heavens” — they are huge the way out to the very limits of the to about 25 galaxies. But the When you see an image of a Elliptical metropolises of hundreds of observable universe! distance between the Milky Way galaxy, you’re seeing the billions of stars. and the Whirlpool Galaxy is about combined light of billions of stars, The Andromeda galaxy, the closest 250 galaxies apart! but no individual stars can be Irregular While galaxies had been observed galaxy to the Milky Way, is about resolved by our telescopes. since the invention of the 2.5 million light years away: it takes Galaxy clusters telescope, it was only in the 1920s 2.5 million years for the light of In fact, at the scale of a typical that we realized they were huge Andromeda to reach our galaxy image (say 2 inches islands of stars outside of our own telescopes! across or 100 pixels), a single star galaxy. would be much smaller than an The Whirlpool Galaxy is even atom! further away; its distance is about 23 million light years.