How do they find black holes and how many are in the Milky Way?

March 31st, 2009 Josephine

To date, astronomers have found 19 confirmed black holes and an additional 18 potential black holes, for a total of 37. All but one of the 37 lie in binary (double star) systems, each in the range from 5 to 10 times the Sun’s mass. Astronomers have also identified a supermassive black hole at the galaxy’s center containing about 4 million times the Sun’s mass.

In binary systems, a black hole and a star orbit each other. The black hole’s powerful gravity strips gas from its companion. As the gas accelerates toward the black hole and heats to millions of degrees, it gives off X rays. Astronomers find the black holes by looking for their characteristic X-ray emissions.

To confirm the black hole’s existence, astronomers track the companion star’s orbital motions. Knowing the star’s orbital speed makes it possible to calculate the mass of the companion black hole.

Appeared in: May, 2009 issue of Astronomy Magazine

Learn more about astronomy in my Introduction to Astronomy course.

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A fun survey from Astronomy magazine

March 27th, 2009 Josephine

http://apps.kalmbach.com/survey/default.aspx?sid=1097&auth=08SKSjoFop

Learn more about astronomy in my Introduction to Astronomy course.

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Astronomy – Sky gazing

March 23rd, 2009 Josephine

A great link for finding night sky objects – http://www.astronomy.com/asy/stardome/default.aspx

Check out my Introduction to Astronomy course.

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Astronomy – Milky Way Galaxy

March 10th, 2009 Josephine

This is a panoramic view of our Milky Way Galaxy. As a guide to the relative physical scale of the Milky Way, if it were reduced to 100 meters in diameter, the Solar System would be no more than 2 millimeters in width.

milkyway_pan1

Find out more in Introduction to Astronomy!

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Astronomy – Stars

March 9th, 2009 Josephine

Do you want to learn more about stars? There are many different classifications of stars and our Sun is just one of many and not even the most common type in the galaxy.

Find out more by signing up for Introduction to Astronomy!

800px-morgan-keenan_spectral_classification

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Astronomy – Our Solar System

March 4th, 2009 Josephine

Our Solar System


- A day on Venus lasts 243 Earth days.

- Jupiter’s Great Red Spot is large enough to engulf Earth twice over and has been raging for 350 years.

- Saturn has sixty known moons.

- Neptune has 2,100 mph winds and it rains diamonds.

Learn more in my Introduction to Astronomy course starting on March 14, 2009!!

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Astronomy – Unaided eye observation

March 2nd, 2009 Josephine

It is often thought that amateur astronomy requires the purchase of a telescope of some kind. Certainly it is true that owning a good quality telescope does make it possible to observe many more objects in the sky than can be seen with the naked eye. However, the fact is that a lot of interesting observing can be done with just the naked eye as well. Some amateurs, even experienced ones, sometimes believe that naked eye observing is only suitable for novices. However, that is not true either. In fact, there are many interesting and worthwhile naked eye projects for even the most advanced observers.

Learn more in my Introduction to Astronomy course starting on March 14, 2009!!

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Intro to Astronomy – Registration is open!!

February 12th, 2009 Josephine

Have you ever wondered:
How the universe started and how it might end?
How our galaxy and solar system formed?
If there is other life in the universe?

This is the course for you!!

Registration for Introduction to Astronomy is now open!!

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Astronomy tidbits

February 10th, 2009 Josephine

A sense of scale:
If the sun were the size of a volleyball and the Earth the size of a pea, they would be approximately 71 feet apart.
If our solar system were the size of a CD, then the Milky Way Galaxy would be the size of the Earth.
If the sun were the size of a golf ball in New York the next nearest star would be a golf ball in Chicago.
The Sun would hold approximately 1 million Earths.
There are 200 billion “Suns” in a galaxy like our own Milky Way Galaxy.
Astronomers can see billions of galaxies.

A sense of time:
If we compress the time since the beginning of the universe (13.5 billions years ago) into one year, and make the beginning January 1, then:
The Earth was formed in mid-September.
The mammals appeared in late December.
All human prehistory (from the first known stone tools) and history have occurred in the last hour of New Year’s Eve.

A sense of energy
At 40 MPH, car consumes about 10,000 watts of power
Hydrogen Bomb releases 100,000,000,000,000,000,000,000 watts
Sun steadily emits 100,000,000,000,000,000,000,000,000 watts, the power of 10,000,000,000,000,000,000 cars

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Intro to Astronomy Class Syllabus

February 10th, 2009 Josephine

Lesson 1 – History and Observation
History of Astronomy
Observational Astronomy

Lesson 2 – The Solar System
Formation and Evolution of the Solar System
Composition of Bodies in the Solar System
Position and Motion of Bodies in the Solar System

Lesson 3 – Stars
Stellar Evolution and Life Cycle
Stellar Properties
Stellar Spectra
Stellar Distances and Parallax
Lesson 4 – Galaxies
The Milky Way and the Local Group
Classification of Galaxies
Interstellar Medium

Lesson 5 – The Universe
Distribution of Galaxies and Hubble s Law
Cosmology The Study of the Universe
The Big Bang
The Early Universe
Expansion of the Universe
The Fate of the Universe
The Multiverse and Theories of Everything

Lesson 6 – Life in the Cosmos
Searching for Other worlds
Habitability of Other worlds
Possibility of Life Beyond Earth

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