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Happy Sunday! Relax! A day to read the newspaper, devour a science magazine, sip some tea, and attack the Sunday paper Jumble like it was Fermat’s Last Theorem. I’ll add to your Sunday reading list with the addition of a new weekly feature here on The Perfect Silence called SunDay. On the day of the week named for our own star, I’d thought that we’d knock on the door of one of our galactic stellar neighbors, and get to know one of the giant balls of luminous plasma that shines down on us.

What better way to start off our first installment of our feature than with (dramatic music sting), the largest star known in the entire universe. Well, at least in the part of the Milky Way that’s visible to us.

This big dog is VY Canis Majoris, and it shines in the constellation of Canis Major, which is nice and high in the night sky right now. Woof!

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VY Canis Major is the St. Bernard of stars – a true stellar giant, at an estimated 2000 times the radius of our own sun.* VY Canis Majoris is classified as a red hypergiant star, and it shines in the constellation of Canis Major, the Large Dog. It’s not only thought to be the largest star observed in terms of its size, but VY Canis Majoris is also one of the brightest stars ever seen. If it were sitting where our sun is now, the star’s surface would extend to the orbit of Saturn, and I’m prrety sure give anyone on Uranus a permanent orange afro.

It’s hard to imagine why such a stellar giant floating anywhere near us wouldn’t completely dominate our night sky with the World’s Largest Night Light. But that’s just it – it’s far, far away from our stellar neighborhood, waving us down from 5,000 light-years away, which actually ends up making it too dim for us to see without a pair of binoculars or a telescope! The fact that it’s as bright as it is from this distance says something about how massive The True Big Dog really is.

VY Canis Majoris may be big, bright, and highly impressive from down here, but it’s also highly unstable. Spasming forth tremendous amounts of gas into its surrounding space, the resulting nebula that has emerged has painted a beautiful picture painted with brush strokes from an astronomically violent and powerful event. Last year, the Hubble Space Telescope turned its Advanced Camera for Surveys toward the nebula to give us our best ever view ever of what the thrashings of a colossus look like.

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All of this is due to the fact that a star this big is overextended, and the star’s gas is held more loosely at its surface that it normally would be. As you can see, the asymmetrical cloud has interesting arcs, and knots weaved through its structure. All this beauty acts as a celestial veil, keeping us from getting a good look at the giant star that lies underneath as a mere pinpoint.

VY Canis Majoris will surely live out its short life, then explode in a spectacular supernova event, releasing its tremendous energy held within. Astronomers can’t say exactly when that ultimate firework will go off, and luckily VY is too far off to do any damage to our home planet. But it should be a spectacular show 5,000 years after it goes off, when the light finally arrives from its long journey to signal that a giant has fallen.

* There is some scientific controversy surrounding VY CMa. In 2006, astronomer Roberta M. Humphreys made the estimate that the star’s diameter was around 2000 solar radii. Then, a paper led by Philip Massey was written, contradicting that estimate, and bringing it down to a more “normal” diameter for a hypergiant. But Humphreys fired back, and published a paper later in the year refuting those claims, laying out in more detail the evidence that VY is indeed a giant among giants.

In the world of astronomy, this is the equivalent of an ultimate science fighting championship! But it illustrates the strength of science – the ability to challenge ideas, hashing it out sometimes uncomfortably, until the best evidence that explains the physical phenomena prevails. Huzzah!

This entry was posted on Sunday, February 24th, 2008 at 4:23 pm and is filed under SunDay, astronomy. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.