Eta Boy Eta Car

Travis:	Welcome to another edition of Slacker Astronomy. Each week we bring you a recent news event from the world of astronomy. And when there is nothing new to report, we'll continue work on our next newsletter for the Pigs In Space fan club where we profile Dr. Strangepork.
Pamela:	But happily for all of you born after 1980, today we have some news to cover about a very bright star way down in the south. Our southern hemisphere listeners should 
	enjoy this episode about a star called Eta Carinae, also known as Eta Car.
Travis:	I don't know. They may be sick and tired of hearing about Eta Car. They see it all the time.
Pamela:	You saying they're spoiled?
Travis:	No, but still. (YAWN!) You hear about it all.. the... time.. eh, I guess it is interesting. (bored pause)
Pamela:	If you like that sort of thing.
Pamela:	Wow, you're becoming a stellar snob.
Travis:	(proud) That's better than being a SUBstellar snob. 
Pamela:	Well you certainly are a SUBstellar comic.
Travis:	Someone's got to provide relief from these BORING stars.
Pamela:	Eta Car is anything but boring.
Travis:	Prove it.
Pamela:	First, it is at least 100 times larger than our Sun. Second, it changes in brightness. In the mid 
	1800's it was the 2nd brightest star in the night sky. Then in the 1900's it faded so that you needed a 
	telescope to see it. Then in the 1990's it surged in brightness again and can now easily be seen with the 
	naked eye. And finally, it's about to blow itself to Kingdom Come. QED!
Travis:	(panic'ed) QED? Where!?!? How'd they find me here?! They can prove nothing!
Pamela:	No, Q - E - D. Its greek for quod erat demonstrandum. It means I've proven my point.		
Travis:	Anytime something is going to blow itself up, that is indeed interesting.
Pamela:	Eta car is expected to go supernova within 20,000 years, a very short period in astronomy. When it does, it 
	will become the brightest star in the Sky other than our Sun. It will be bright enough to be seen in daylight and 
	to cast shadows at night. 
Travis:	But there is no need to hoard the SPF 1 million sunblock just yet. Eta Car is pretty far away as bright stars 
	go at 7,500 light years away. So the supernova shockwave won't be strong enough to hurt us.
Pamela:	And if it turns into a hypernova and creates a gamma ray burst, it won't be pointed at us. The axis for 
	Eta car is pointed 45 degrees away from us. So again, we're in the clear.
Travis:	It's good to be the Earth. We have no known supernova candidate stars nearby and no hypernova candidates 
	pointing at us.
Pamela:	Our biggest threat is ourselves.
Travis:	Amen to that.
Pamela:	Eta Car is not only big, but it is spinning very quickly, so fast that if it spun only 10% faster it would fly apart. 
Travis:	The star itself is flattened at the poles. Most stars and planets are not really spheres but rather are elongated
	a bit at the equator. Eta car, because it is spinning so fast, is very elongated and shaped a little bit like a 
	wheel of cheese, only not as extreme.	
Pamela:	Imagine the center of that wheel of cheese. Now picture the surface of the cheese. The surface on the
	round edge of the wheel is farther away from the center than the surface on the flat edge.
Travis:	As a result, the flat edge is closer to the Hydrogen and Helium fusion going on in the core. So it is
	warmer. Since it is warmer, it is radiating more energy. So that explains why the winds are so much stronger at
	the poles. 
Pamela:	In a regular star, the opposite happens. Winds are usually stronger at the equator because centrifigual force is helping to speed it up. Eta Car likes to be different. 
Travis:	These winds blowing from the poles have created a beautiful and exotic nebula around Eta Carinae. It consists of two billows of mass blowing outward at 1.5 millionmiles per hours. It has many names, but most astronomers refer to it as the Homunculus.
Pamela:	The term historically refers to a very small person created... how should we put this.. in ways thatwould be have gotten you burned at the stake 200 years ago. 
Travis:	Or a late night spot on Cinemax today.
Pamela:	Anyway, the term is now used in modern culture to explain systems that have mysterious inner workings,where we have no idea what really goes on at the core level. Like consciousness...
Travis:	Or why cats go nuts in the middle of the night and break things...
Pamela:	Or why anyone would try out for Fear Factor
Travis: Or why anyone would *watch* Fear Factor
Pamela:	So the humunculus is an appropriate name. We have no idea what is really going on deep inside the star.
Travis:	Perhaps it is the fortress home of the Flying Spaghetti Monster.
Pamela:	Or perhaps it is two stars.
Travis:	Two stars? I like my idea better.
Pamela:	How about one star and one Flying Spaghetti Monster?
Travis:	Hmmm. Interesting visual.
Pamela:	The problem is, the spaghetti monster would have to be really big. Astronomers have been monitoring the star's spectra for decades and they have detected a sudden dimming of some spectra lines every five and a half years.
Travis:	This dimming looks an awful lot like an eclipse. It occurs regularly, suddenly and has a relatively flat bottom. A light curve of it is in our show notes at slackerastronomy.org. 
Pamela:	So the Spaghetti Monster would have to be very big to block the light from an entire star for months onend.
Travis:	Spaghetti is pretty tasty. I would assume a spaghetti monster would be big and fat.
Pamela:	Instead of inventing mythical beasts...
Travis:	Who said it is a beast? Maybe its nice and cuddly and...
Pamela:	I SAID! Instead of inventing mythical beasts, let's stick with tried and true physics. One possible explanationis that a second star is in the system. It would be a smaller star orbiting the main star, but still more massive than our Sun. 
Travis:	A recent paper published by Rosina C. Iping and four coauthors claims that this is the case. Using observations made with the Far Ultraviolet Satellite explorer, also known as FUSE, she claims that the kind of ultraviolet light blocked in the eclipse is the kind that would be radiated by a secondary star 30 times 	as massive as the Sun. 
Pamela:	This supports a claim made last year that shadows caused by the primary have been detected by the Hubble Space Telescope. Normally Eta Car is surrounded by a glow of ultraviolet light. When one of the eclipses occurs, the ultraviolet light around the star dims.
Travis:	But it doesn't dim uniformly. Instead, different sides of the star dim at different times. Astronomer Nathan Smith claimed last year that these dark areas are shadows caused by the bright central star blocking the ultraviolet radiation from the companion. 
Pamela: Thus the gas and dust behind the star doesn't get any radiation to energize it. So it is dimmer and looks like a shadow.
Travis:	These are both creative ideas that show astronomers are thinking outside the box to explain Eta Car. It is so puzzling that open minded approaches are needed.
Pamela:	But the ideas are also untested in observations of other stars and have some weaknesses. For example, there could simply be clumps of matter orbiting the central star. Or variations in the stellar wind. Plus, X-rays have been detected from Eta Car that cannot be explained by a secondary star. 
 (aaron's post recording errata: this next line may not be true, see discussion about this at
 http://www.slackerastronomy.org/wordpress/index.php/archive/eta-boy-eta-car-ff-show-32/ 
 for alternatives)
Travis:	Eta Carinae and the secondary would both be too cool to generate X-rays. So some have claimed that collision in winds from the two stars could do it. But that would require the secondary star to be massive and bright as well, which while not impossible, would be unlikely. 
Pamela:	And, finally, observations of the eclipses at other wavelengths do not detect any missing light not generated by Eta Car itself. So only a very specific type of short wavelength ultraviolet light from the secondary makes it out of the nebula and into our telescopes. So where is the rest of the light?
Travis:	Lots of questions remain. Eta Car researchers are split down the middle of the debate. Evidence is mounting that a secondary star exists. But it is not yet conclusive. 
Pamela: What is conclusive, though, is that there is something else in the system. Whether it be a star, a chunk of matter, thick globs of wind, or a flying sphaghetti monster, it's there. 
Travis:	The next eclipse comes in 2008 and now that Spitzer is up, some detailed observations of the dust ininfrared should be possible. In infrared, Eta Car is the brightest object in the sky outside of our solar system - an easy target for a precision instrument like Spitzer.
Pamela: And an easy episode for Slacker Astronomy. 
Travis:	This star pratically writes itself. 
Pamela: It has mystery, politics and even an explosive ending.
Travis:	Maybe we should pitch it to Hollywood as a movie of the week.
Pamela: This is real stuff, we should pitch it as a reality show.
Travis:	And tarnish Eta car's reputation with that rubbish?
Pamela:	Ah, so you like Eta car now.
Travis:	Yeah, I'm convinced. The southern hemisphere listeners are lucky. Go out tonight and take a look at Eta Car. Who knows if it will be there tomorrow!
Pamela:	And with that, thanks for listening to another episode of Slacker Astronomy.
Travis:	As always, show notes are on our web site. We also have linked to a neat map listener Dr. Slime aka Mike Garlick made for us. All you do is type in your zip code and it plots your location on the map along with many other SA listeners.
Pamela:	Please drop by slackerastronomy.org and add yourself to the map. There are about a hundred people there so farl You can also add a picture while you're at it. It's neat to see where everyone is from and the map willmake a good visual for our funding applications.
Travis:	For Pamela, our author Aaron, annd this week Mike Koppelman for consultation, I'm Travis. Clear skies and clear bandwidth.
Pamela:	You've been listening to slacker astronomy, a podcast for you, for fun, for the voices in our heads.