Looking Up: You think it's hot here?

Peter Becker GateHouse News Service

As the nation deals with a long heat wave, we do well to be grateful for our planet, placed where it is in a solar system multiple billions of miles wide. We could be on Mercury where the sunlit side bakes at +800 degrees Fahrenheit (F), or Pluto, with an average surface high of almost -250 degrees. Instead, we are in the proverbial "Goldilocks" zone, where our porridge is neither too hot or too cold.

Of course this is all very relative. The Earth's temperature extremes send us rushing for an air conditioner or piling on the layers to warm us, and what's just right for someone is dastardly hot or cold for the next. Still, we survive without a space suit!

A rage among astronomy circles today is the quest for planetary systems around other stars. Since the first planet was confirmed in 1995, well more than 700 "exo-planets" have been found. Some planets have already been located in the "Goldilocks" zone around their host star, where at least the thermometer readings would be attractive for life as we know it.

Of course there are many other factors for a habitable planet, let alone a place we would want to visit very long. The Earth is blessed as an abode of life with the right temperature range, gravity, a magnetic shield, an atmosphere of the right pressure and mixture of gases, a moon able to sweep up much of the incoming asteroids, and geologic makeup.

How hot or cold does it get out there?

The surface of the sun is an astounding 10,000 degrees Fahrenheit. At the center of this great ball of churning gas, the temperature reaches 27 MILLION degrees. The outer envelope of the sun, known as the corona, surges to temperatures in the millions. Yet there are hotter stars than our Sun.

Stars have a wide range of temperature, which influences their color and are rated on a scale by how hot they are. Mass of the star - the amount of material in a given volume - increases with the temperature.

Astronomers normally use the Kelvin scale of temperature (K) when talking about stars. Absolute zero, or 0 K, is be the lowest temperature possible, where particles have ceased motion. Absolute zero has the equivalent of -459.67 degrees F or in Celsius, -273.15 degrees.

Blue stars such as brilliant Vega, high in the summer evening sky or Sirius in the winter evening sky, are among the most hot. The hottest are over 25,000 K, with an average mass of 60 times that of the sun (+44,540 Fahrenheit). The sun, on the Kelvin temperature scale, is about 5,000 to 6,000 K.

A massive red supergiant star such as Betelgeuse in the winter constellation Orion or Antares in the summer evening sky (in Scorpios), are among the most "chilly." The temperature is about 3,500 K. That's still +5,840 Fahrenheit.

The coldest temperature in deep space is about 2.7 Kelvin degrees above absolute zero (-454 F).

Venus, by the way, is the hottest planet in the solar system though second in distance from the sun. Its thick cloud cover and carbon dioxide atmosphere creates a viral greenhouse effect. The surface fries at +900 F!

While we deal with what we consider extremes on Earth, we still marvel at the night sky and the depth and breadth of the cosmos of which we are a part.

New moon is on July 19.

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Keep looking up!