Good Fact #5: The Milky Way Galaxy

Written by on July 7, 2010 in Good Fact Series with 0 Comments

An hour and half northeast of Toronto is the town of Peterborough. It’s a great place to live, especially if you like quiet mid-sized towns with safe neighbourhoods, green parks, clean lakes, rushing rivers and bright starry nights.

Travel another hour north and you’ll be in fabled cottage country. This area doubles its population every summer weekend due to fleeing city folk. They jam the highways to and from their tense downtown lifestyles to find more comforting, low key hideaway’s in the woods.

Hurriedly the take to the golf courses, glistening lake waters and pristine wilderness with their quadrunners, speed boats, and over priced golf clubs. After a busy a day of premeditated fun they reflect on the days’ frivolity over a glass of wine or bottle of beer.

Then as night falls, the grand finale swoops overhead. It’s subtle and others may not notice but with luck you may pick up on it. It is the Milky Way. A grand light show, shining bright as ever far from light polluted skies. More than just stars, it is the plane of our galactic disk cutting a path right above your head from horizon to horizon. If you see it you’ll definitely point it out to others, for it is magical and reminds us there is lot more to the universe than just us and our busy little lives.

Photo: Larry Landolfi

I recall my first date with my wife, we went to a nighttime rally race in the woods near Bancroft, we still talk about how incredible the stars were that night.

Dark country nights bring many astronomical attractions but the Milky Way is by far one of my favourites. Many describe it looking like a milky trail that spills across the sky, and so it is aptly named. In fact the word galaxy is derived from the greek word for milk.

This glowing band of light is actually millions of stars along our galactic plane, too faint to be distinguished individually. In the northern hemisphere it is brightest in the summer because the galaxy’s nucleus is at its highest point on the horizon.

To image what our galaxy looks like, think of flying away from our solar system at a distance of several thousand light-years, looking back and seeing a great cloudy disk of stars, gas and dust twirling around in space. You would see that the Milky Way Galaxy is a barred spiral galaxy that is approximately 100,000 light-years in diameter and on average 1000 ly thick.

Its Galactic disk consists of a bar-shaped core and four major spirals arms. Branching off the arms are at least 2 smaller arms or spurs. Our Solar system is found within the Orion Spur, roughly 25,000 ly from the galactic center.

In astronomy a light year is a unit of measure that is approximately 10 trillion kilometers in length or the distance traveled in one year at the speed of light.

Needless to say the galaxy is absolutely enormous. So colossal in fact that to relate in terms of something familiar is going to take something that is very big already, the continent of North America. Please see the fiqure below.

If our solar system were reduced to the diameter of a typical coffee cup, the Milky Way would span across the continent of north America between Victoria, British Columbia and Boston, Massachusetts.

This depiction of our solar system includes all the planets and the Kuiper Belt (the asteroid belt to which Pluto is part of). Incidentally, at this scale our solar system would be poisition over Dodge City, Kansas.

You may be interested to know that our closest neighbouring star, Proxima Centauri, would only be roughly 1 city block away from our coffee cup sized solar system. And eventhough that sounds close, it would still take you almost 18,000 years to reach it. That’s even at the highest speeds available from modern propulsion systems which is about 254,000 km/hr (attained by the unmanned spacecraft Helios II).

Currently, NASA’s New Horizons mission launched a probe in Jan 2006. It is traveling out over our solar system at over 58,000 km/hr and will arrive at Pluto by July 2015, almost ten years later! Needless to say we won’t ever be visiting any other stars in our galaxy, the distances are just too far.

Note – the Milky Way is not as bright as what is shown in the photograph at top, this image is due to long time exposures and makes it brighter than it actually is. To the naked eye though you wouldn’t see as much detail but it is still quite striking.

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