What Is…?

What is a Meteor? What is a Comet? What is a Star? What is a Nebula? What is an Open Cluster? What is a Black Hole? What is a Quasar? ? ? ? ?

What Is Astronomy? Reflection nebula IC4606 by George Greaney

What is Astronomy? Astronomy is a science that attempts to understand the make-up and the history of the universe. Galaxy M83 in Hydra by George Greaney

Basically, if its off this planet its a study of some realm of astronomy. As one might imagine that covers an awful lot of subjects, even more than we know right now. A short list of subjects include: NGC 253, galaxy in Sculptor by George Greaney

Stars Nebula Planets The Sun The Great Andromeda Galaxy by George Greaney Star clusters Galaxies Galaxy clusters Dark matter Black holes

Galileo Observatory in Italy An Astronomer is a Scientist, skilled in Mathematics, Physics, and Astronomy Most Professional Astronomers work for Universities or Government Agencies Source: The Berkeley Cosmology Group

Galileo Galilei ( ) What is an Astronomer? A night watchman with a college education?

Astronomer Serena Kim at work At Cerro Tololo in Chili Few astronomers spend much time looking through a telescope. Most operate telescopes from a control room or even from their computer at home via the Internet. Typical astronomers only spend one or two weeks each year observing, and the rest of their research time analyzing their data. Source: Applied Theoretical and Computational Physics Division Los Alamos National Laboratory

Amateurs and their tools What is an Amateur Astronomer?

What is an Amateur Astronomer? Although the Term has different meanings for different people, a basic definition would include anyone who looks into the sky, and wants to see or learn more.

Tonight You are an Amateur Astronomer

What Is a Meteor?

A Meteor is a bright streak across the sky, or a “Shooting star” produced when a small piece of comet or asteroid, called a meteoroid, enters the Earth’s atmosphere. Source: The Lowell Observatory A Meteor from the annual Leonid Meteor shower lights the sky

A meteoroid is the dust, rock, or debris still in space. It could be a chunk of an asteroid or comet. The Giant Asteroid Gaspra What is a Meteoroid? Source: NASA

A meteorite is a meteor that actually falls to the ground. Most meteors burn up and never make it to the ground. The Giant Asteroid Gaspra What is a Meteorite? Meteorite Damage, Peekskill, NY Source: NASA

What Is a Comet? Image by Dave Dockery Astronomical Society of Las Cruces Comet Ikeya Zhang

A comet is basically a ball of ice and dust in space. The typical comet is less than 10 kilometers across. Most of their time is spent frozen solid in the outer reaches of our solar system. Image by Harvard-Smithsonian Center for Astrophysics Comet Hale Bopp

A comet orbits around the sun, in a wide, elliptical path. When a comet gets within a few million miles of the sun, it begins to melt, leaving a tail of gas and dust that is blown by solar winds Image by Harvard-Smithsonian Center for Astrophysics Source: NASA Comet Hale Bopp

What Is a Star? Image of the Sun from Goddard Space Flight Center

What is a Star? Our Sun is the closest star. At the simplest, a star is just a ball of gas that has condensed out of interstellar material. The largest part of its lifetime is spent as a main sequence star during which hydrogen is being converted to helium balancing gravitational contraction so that the radius and energy output remain almost constant. Source: The British Astronomical Association

Our Sun is a star that has already spent about 5 billion years on the main sequence. Scientist believe our Sun is roughly halfway through it's life.

Image courtesy of Dave Dockery Astronomical Society of Las Cruces Source: The British Astronomical Association Nearby Stars: Name Distance from Earth Sun 93 million miles (8 light minutes) Proxima Centauri 4.22 Light Years Alpha Centuri A,B 4.39 Light Years Barnards Star 5.94 Light Years Wolf Light Years Lalande Light Years Sirius A,B 8.6 Light Years

What is a Light Year? Buzz Lightyear - Superhero

A Light Year is a unit of Distance, not time. It is the distance that light travels in one earth year, which works out to: 5,903,300,000,000 Miles A Light Year is almost six trillion miles long!

That’s a long way! But even further Than most folks realize. Compare this to a distant but familiar object, Like Pluto. Pluto is about 5 light HOURS from Earth. Only a small fraction of a light year Pluto, as seen by the Hubble Space Telescope

What is a Star Cluster? Image by Dave Dockery Astronomical Society of Las Cruces Omega Centauri

Image by Dirk Langenbach Star Clusters are collections of a few dozen to many thousands of stars, which are gravitationally bound. Image by Dave Dockery The Pleiades, an open cluster Hercules Cluster, a globular cluster

What Is a Nebula? North American Nebula, Image by George Greaney

Reflection Nebula IC4592/4601 in Scorpius, byGeorge Greaney A nebula is a cloud of gas and dust in space. Some nebulas are regions where new stars are being formed, others are the remains of dead or dying stars. Source: NASA

Types of Nebula: Emission Nebula The Orion Nebula Image by Dave Dockery Astronomical Society of Las Cruces An Emission Nebula absorbs the light of nearby stars and reaches very high temperatures. Emission nebula are often found in regions of space where new stars are forming. Source:NASA

Types of Nebula: Reflection Nebula The Pleiades Image by Dave Dockery Astronomical Society of Las Cruces A Reflection Nebula is a cloud of gas and dust which does not create its own light, but instead shines by reflecting the light from nearby stars. Source:NASA

A planetary nebula is created when a star blows off its outer layers into space, forming a nebula In the shape of a ring or bubble Types of Nebula: Planetary Nebula The Dumbell Nebula Image by George Greaney Source:NASA

Dark clouds in space are called absorption nebulas or dark nebulas. An absorption nebula is a cloud of gas and dust which blocks light from the regions of space behind it. Types of Nebula: Absorption Nebula The Horsehead Nebula Image by George Greaney

The Andromeda Galaxy Image by Dave Dockery Astronomical Society of Las Cruces The term Nebula was first coined in the 19th century by Herschell, a famous astronomer, to distinguish anything in the sky that looked indistinct. Some of his 'nebulae' turned out to be entire galaxies such as the Andromeda “Nebula“.

Illustration of Cygnus X-1 from the Astronomy Cafe What is a Black Hole?

Source: The Berkeley Cosmology Group What is a Black Hole? Loosely speaking, a black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull.

Images from Hubble Space Telescope What is a Quasar?

Illustration from the Astronomy Cafe What is a Quasar? Quasars are one of the Most mysterious and rare objects in astronomy A quasar is a very, Very bright object at the core of a few highly active galaxies. Quasars are thought to form as matter spins into super massive black hole at the center of these galaxies.