A Star on the Edge

[tom_hobbes]

I don't know if anybody's posted this but it rather tickled me to imagine living on a habitable planet with this thing in the sky once a day:<br /><br /><br /><b>Portrait of a Star on the Edge</b><br /><br />A new telescope array yields an unprecedented close-up of the bright star Regulus<br /><br /><br />January 19, 2005<br /><br />Arlington, Va.—Astronomers have known for decades that Regulus, the brightest star in the constellation Leo, is living very close to the edge.<br /><br />Only a few hundred million years old—young by stellar standards—Regulus has some three-and-a-half times the mass of our own middle-aged Sun, some 350 times its energy output, and a truly prodigious rate of spin. Our Sun makes one sedate rotation every 24 Earth days; Regulus whips around in less than one day. Indeed, its equator is moving at well over 700,000 miles per hour—perilously close to the speed at which the outward-pointing centrifugal force would cancel out the inward pull of the star's gravity. If Regulus were spinning even 10 percent faster, it would tear itself apart.<br /><br />Scientists at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) have now detailed some of the consequences of such behavior. Using their recently completed array of optical telescopes atop California's Mount Wilson, the CHARA astronomers have measured Regulus' size and shape, the temperature difference between its poles and equator, and the orientation of its spin axis.<br /><br />Their results are summarized in this computer-generated model of the star, which is shown with a similar model of our Sun for scale. The model is tilted on its axis 86 degrees from celestial north—just as the real Regulus appears in the sky. That makes the axis almost horizontal in this picture, and the equator almost vertical.<br /><br />Regulus' frenetic spin gives the star its grossly bulging mid-section; its equatorial diameter is one-third larger than its north-south diameter. But almost as striking is the <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>

 

[vogon13]

Sagan has speculated that stars with high spin rates are most likely unplaneted, unfortunately.<br /><br />Still we can imagine a world....<br /><br /><br />in a more distant polar orbit around Regulus. It experiences summer (planet wide) while passing over the poles of Regulus and winter when equatorially located. Thus you could have a world with synchronized seasons all over, and two complete sets of seasons every year. If a 730 day (earth day) polar orbit would put this hypothetical world in the Regulus habitability zone, it would make a neat setting for a sci-fi story for human type beings. <br /><br /><br />{fixed spelling error} <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[rogers_buck]

No, please, not even one more thin mint or I'll explode!

 

[tom_hobbes]

It's only wafer thin sir... <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>

 

[tom_hobbes]

I imagined that there'd be problems to having planets, let alone habitable one's around such a star, but I also imagined that if there were, they'd be orbiting on a plane perpendicular to the sun's axis.<br /><br />But if you <i>could</i> have planets in a polar orbit to a star like this, what a fantastic setting for a story, Vogon! <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>I imagined that there'd be problems to having planets, let alone habitable one's around such a star, but I also imagined that if there were, they'd be orbiting on a plane perpendicular to the sun's axis.<br /><br />But if you could have planets in a polar orbit to a star like this, what a fantastic setting for a story, Vogon!<p><hr /></p></p></blockquote><br /><br />Oh man, that would be BIZARRE!<br /><br />Of course, the wildly oblate shape might also have some significant gravitational consequences on any orbiting planets. A polar orbit might not be very stable, or might have an odd shape to it. The planet might not orbit in a neat ellipse, but perhaps more of race-track shape, or like an oval dinning room table that's had several leaves added into its middle to accomodate more guests.<br /><br />It's wild to think about a star so misshapen. We're used to our sun being basically spherical (yes, I know the sun's oblate, but it's below the threshhold of perception; it looks spherical). We're used to our moon being that way too. I think that in interplanetary travel, it'll be the little things like that that will make things seem particularly weird. I remember freaking out on time when I saw the Milky Way in all its glory out in a remote mountaintop wilderness area. I just wasn't used to it. (And it wasn't the first time I'd been in a really dark sky! I'm not sure why it freaked me out on that occasion, although the fact that it was the middle of the night and I was jogging from the cabin to the outhouse may have had something to do with it.) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[claywoman]

Again, I have a question here...<br /><br />If that star should 'slow' down its rotation, would it become more spherical?

 

[CalliArcale]

Yes; rotation is the only thing making it bulge out like that. It's like tossing a pizza crust, except that the basic "stuff" of Regulus is much more fluid. Gravity will pull it back into a sphere. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>