Mira, Mira on the Wall

8/19/07


78 trillion miles. That is, seventy-eight with twelve zeros after it, miles. There is no analogy, simile or metaphor known to man which I could use to illustrate how great a distance that is; the human mind simply cannot grasp it. 78 trillion miles is 13 light years*, and that’s the size of this object:

That light blue, gossamer tail is glowing material being spewed from a red giant star named Mira as it hurtles through space at 80 miles per second. Mira, pronounced MY-rah, Latin for “wonderful,” is deep in her death throes, which is what has caused this massive venting of her elements. She’s been known to astronomers since the 17th century, and has about the same mass as our own Sun. But Mira is running out of the Hydrogen which powers a star’s fusion, and has bloated to 400 times the size of our star due to loss of fuel. It's the same thing that will happen to our star when Sol finally gives up the ghost. At this size, gravity can no longer hold Mira together properly, and her mass gets shunted off into space like dry ice vapor, creating this “tail” which makes Mira look like a comet on steroids.

The picture is actually an ultraviolet image taken from NASA’s orbiting telescope Galaxy Evolution Explorer, and it’s like nothing we’ve ever seen before. The “tail” is made up of enormous amounts of star dust, including oxygen, nitrogen and carbon. This colossal amount of star vomit is seeding our galaxy with vast stores of raw material which could eventually form new stars, planets and solar systems. NASA scientists believe there are probably many more of these objects pinballing around the Universe, and it’s just one method by which new celestial bodies are born from the remnants of the old.

Twenty bucks says my wife has not read this far.

Mira’s not alone inside that cloud, either. She travels with a companion star, a white dwarf around which Mira orbits. Our single-star solar system appears to be the exception rather than the rule; about 2/3 of star systems have binary stars like Mira. Scientists think she will eventually vent all of her gas into space, forming an amorphous nebula, eventually collapsing into a white dwarf**.

Mira is about 350 light years from earth, if you want to try and wrap your mind around how far away that is.


Source – A Star with a Comet’s Tail; Science@NASA

--Image taken from http://www.space.com/images/h_in_sun_redgiant_03.gif

*The distance light travels in one earth year. At a jaunty clip of 300,000 km/second, that’s about 6 trillion miles every 365 days.

**A white dwarf star is about the same mass as the Sun, but is only as large as the earth. Therefore, if you could stand on a white dwarf, you’d weight approximately 330,000 times what you weigh here. Just to put into perspective how dense a white dwarf is, a teaspoon of such star matter would weigh about 40 tons here on earth.