Bootes, pronounced by most people as Boot-tees, is one of the 66-plus constellations we see in the Northwest. It doesn’t really look like what it’s alleged to be.
According to Greek and Roman mythology, Bootes is supposed to resemble a farmer chasing a great bear. That beast is depicted as the famous constellation Ursa Major, better known as the Big Bear.
How the farmer got into the sky is quite a soap opera that I’ll get to in a bit.
Instead of a farmer look for a sideways kite pointing to the left in the eastern sky. The very bright star Arcturus is fixed at the tail of the left-leaning kite. Use the old rule “arc to Arcturus”: Extend the arc of the Big Dipper’s handle beyond the end of the handle and you’ll run right into Arcturus.
It has a noticeably orange hue; a calling card that tells astronomers that Arcturus is a cooler star. Bluer stars are hotter and reddish-orange stars are cooler. It’s just like a flame in a campfire.
The hottest part of the fire will be the inside blue flames, with the cooler orange flames on the outside.
Even with its orange hue, astronomers describe Arcturus as a red giant star, a bloated star that’s starting to run out of hydrogen fuel at its core.
Stars in the prime of their lives produce energy and light through a process called nuclear fusion.
Tremendous gravitational pressure causes hydrogen atoms in a stellar core to ram into each other so hard that they fuse together to form heavier helium atoms.
Eventually, over billions of years, stars begin to run out of hydrogen in their cores. That’s what happened to Arcturus.
As the hydrogen is expended, the core begins to collapse releasing tremendous heat that surges into the outer edges of the star, forcing the star to bloat out way beyond its original size.
Arcturus is nearly 22 million miles in diameter, about 25 times that of our sun but relatively cooler. The sun surface temperature is about 10,000 degrees and Arcturus is just under 7,000 degrees. Badly bloated Arcturus is shining on from more than 212 trillion miles away.
Big celestial hugging
In the early evening the planets Jupiter and Venus are beginning their tango toward other from night to night that culminates at the end of this month when they’ll be joined by the planet Mercury.
This week Jupiter and Venus will be visible toward the end of evening twilight in the west-northwest sky.
Both planets are easily seen with the naked eye with Venus, the brighter of two, just barely above the horizon. You’ll need an unobstructed view of that horizon to really see both planets.
Mike Lynch is an astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of “Stars, a Month by Month Tour of the Constellations.” Check his website, www.lynchandthestars.com.
The Everett Astronomical Society: www.everettastro.org/.
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