How Hot Is the Hottest Star?

What's the densest object in the universe? The brightest? The loudest? In his new book Extreme Cosmos (Perigee, 2012), astronomer Bryan Gaensler reveals the cosmic record holders of these and many other titles. In an excerpt below, from the chapter "Extremes of Temperature," Gaensler explains the physics behind some of the hottest stars known:

We all know that if you heat something up, it glows. A poker in a fire shines a dull orange or red, while a conventional (incandescent) lightbulb works by heating up a tungsten filament to several thousand degrees so that it glows yellow or white. These are special cases of a universal process first properly explained by German physicist Max Planck: Virtually every object (whether on Earth or in space) radiates light, and the color of this light is tied to the object's temperature.

Spectacular Photo of Orion Space Cloud Snapped by Night Sky Observers

After seven cold nights, an exhausted astrophotographer captured this beautiful photo of the Orion Molecular Cloud Complex.

The complex is a region of a vast nebula containing dark dust clouds and newly-formed stars the constellation Orion. It has a range of bright and dark regions some of which can be seen with the naked eye.

Astrophotographer Josh Knutson from Rio Rancho, New Mexico teamed up with Salvatore Grasso in June to complete post processing of this stunning night sky  image. The night sky photographers made the image using a 200 mm SCT telescope. The image was made by taking a 28-hour exposure over seven days, with Knutson and Grasso collaborating in the post-processing work.