Chris McKitterick (mckitterick) wrote,
Chris McKitterick

Astro-Porn of the Day: Surface of (Shrinking) Betelgeuse

Here's an amazing photo of the supergiant star, Betelgeuse (pronounced "beetle-juice") - an actual photograph of the surface of another star!

Click the image to read the .pdf article by the scientists who released the image.

This shot (taken by UC-Berkeley's Infrared Spatial Interferometer at Mt. Wilson) shows some fascinating detail; note the two bright areas; these are called "star spots," similar to our Sun's sunspots, though these enormous convective cells rising from below the star's surface are bright. This is because they're hotter than the rest of the surface, as opposed to dark sunspots, which are cooler because their magnetic fields inhibit convection. By "cooler," I mean 3000°Kelvin, hotter than anything short of a nuclear bomb. Even so, the hottest spot on Betelgeuse is cooler than the coolest sunspot on our Sun because of two things: 1) it's a red star, and stars at that end of the spectrum are cooler (blue is hottest), and 2) it's huge, so its total temperature is spread across a wider surface area.

Betelgeuse (pronounced "beetle-juice") is one of the brightest stars in our sky. It is also one of the largest stars in our galaxy - its surface is about as wide as the orbit of Jupiter. That's about 1,000 times as wide as our Sun. As big as it is, it has been steadily shrinking since 1993 - about 15% since then. To put that into perspective, it has shrunk by a distance about the same as the orbit of Venus. Now that's> a big star.

Why is this shrinkage interesting? Because, combined with its age (8.5 million years, old for a supergiant, which would be an infant for a Main Sequence star like our Sun, which is 4.5 billion years old), this is typically what happens to a supergiant star as it reaches the end of its life... right before it goes supernova! Betelgeuse's death-explosion will be the brightest ever recorded, brighter than the full Moon. Considering its size and age, it's scheduled to blow sometime between today and 1000 years from now. To put your mind at ease, because its rotational axis points away from Earth, Betelgeuse's supernova will not fire a gamma-ray burst death-ray directly at us. Such an event would wipe the biosphere from the surface of the Earth. Others might, of course. Just FYI.

You can find Betelgeuse in the night sky this time of year; it's the bright, orange star that forms Orion's left shoulder (from our POV). See this cool series of shots to identify Betelgeuse, zooming from naked-eye view to regular-telescope view to the European Southern Observatory's Very Large Telescope view in this photo:

Click the image to see the story.

Speaking of which, here's the best photo we had previous to the new interferometry shot, showing a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface:

Click the image to see the story.

Here's how Betelgeuse might look from the observation port of a starship in near orbit:

Click the image to see the story.

The massive bubbles belching out from the surface of the star shed mass equivalent to that of our Sun every 10,000 years. Consider that for a moment.

Tags: astronomy

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