Jimmy Westlake: The hottest star in the sky
Steamboat Springs — Back in my days as a planetarium director, I entertained and amazed youngsters by the busload with stories about the stars, planets and constellations. One of the most unexpected questions I ever got was from a little girl in kindergarten who, after I had gone on and on about the stars in Orion and Taurus, asked me — in the most innocent voice possible — “What would happen if you ate a star?”
Whoa. I had to think fast.
“Well, you would burn your mouth because stars are very, very hot,” I replied.
Then we got into a discussion about just how hot stars are.
“See that red star up there?” I said, pointing to Orion’s shoulder star, Betelgeuse. “Red stars are cool stars. Blue stars are the hottest, like that one in Orion’s foot named Rigel.”
That seemed to satisfy her curiosity.
Stars are assigned a letter of the alphabet to designate their temperature, but not in the usual A, B, C order. The stellar temperature alphabet, from hottest to coolest, is O, B, A, F, G, K, M. The traditional way that astronomy students remember this temperature scale is with the mnemonic “Oh, Be A Fine Girl (or Guy), Kiss Me!” The coolest stars are 3,000 degrees, and the hottest stars are about 40,000 degrees. Our sun, being yellow, is a fairly cool star of temperature class “G.”
That little girl’s question set me to thinking. What is the hottest star you can see with the unaided eye? After a little investigation, I discovered that it is the star Zeta Puppis, also known as Naos. It belongs to the constellation of Puppis, the Poop Deck, and is not far from the sky’s brightest star, Sirius.
To locate Naos, you’ll need an unobstructed view to the southern horizon because Naos never rises very high in our sky. Draw an imaginary line from Orion’s shoulder star, Betelgeuse, to the lower left to find Sirius, then extend that line an equal distance beyond Sirius to the next bright star you see. That’s Naos, the sky’s hottest star.
Hot “O” stars like Naos are exceptionally rare. Recent measurements reveal a surface temperature for Naos of 42,000 degrees, placing it near the top of the list of hot stars, and certainly the hottest visible without a telescope. It emits as much energy as 800,000 suns.
The only reason it looks as faint as it does is because it is so far away — nearly 1,400 light years. If Naos were as close as Sirius (about 9 light years from Earth), it would shine like a second sun in our sky, casting distinct shadows in the night.
Hot stars like Naos also use up their fuel very fast, so they don’t live for long. In just a few hundred thousand years, Naos will go kaboom as a supernova, splattering its innards all over this corner of the galaxy and probably leaving behind the ultimate stellar corpse — a black hole.
Pull out your binoculars and aim them at Naos to appreciate its beautiful blue color, and while you are in the vicinity, scan around for several gorgeous star clusters nearby. This section of the southern Milky Way is loaded with little stellar jewel boxes.
Just be careful not to burn your mouth.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published all around the world. Visit Westlake’s website at http://www.jwestlake.com.
Support Local Journalism
Support Local Journalism
Readers around Steamboat and Routt County make the Steamboat Pilot & Today’s work possible. Your financial contribution supports our efforts to deliver quality, locally relevant journalism.
Now more than ever, your support is critical to help us keep our community informed about the evolving coronavirus pandemic and the impact it is having locally. Every contribution, however large or small, will make a difference.
Each donation will be used exclusively for the development and creation of increased news coverage.
Start a dialogue, stay on topic and be civil.
If you don't follow the rules, your comment may be deleted.
User Legend: Moderator Trusted User
In late 2019, Routt County Riders and Partners in Routt County were handed the blueprints for what had previously been known as the Steamboat Stinger. With the birth of the Honey Stinger Emerald Mountain Epic,…