Dark country nights bring many astronomical attractions, but the Milky Way is 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. Up here 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, imagine 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 its shape 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 it is nearly impossible to relate to its size. However, if you were to imagine our solar system reduced to the diameter of a typical coffee cup, at this scale the Milky Way would span across the entire continent of North America, from Victoria, BC right over to Boston, Massachusetts.
This analogy would include all the planets and the Kuiper Belt (the asteroid belt to which Pluto is part of). If your interested, at this scale our solar system would be roughly where Dodge City, Kansas is on a map.
You may be also 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 even though that sounds close, it would still take you almost 18,000 years to reach it. That’s because the highest speeds available from modern propulsion systems is about 254,000 km/hr (attained by the unmanned spacecraft Helios II).
NASA’s New Horizons mission launched a probe in Jan 2006 to travel to Pluto, and with it travelling at 58,000 km/hr, it 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.