Date: January 26, 2010

Title: Once Upon a Lonely Sun

Podcaster: Pamela Gay

Links: Astronomy Cast: http://www.astronomycast.com/
Star Stryder: http://www.starstryder.com/

Description: In this podcast — recorded on a cold and snowy day — Pamela shares three of her favorite winter objects.

Bio: Dr. Pamela Gay is a professor at Southern Illinois University-Edwardsville. She is also an astronomer, writer, and podcaster focused on using new media to engage people in science and technology. Listen to her weekly on one of the most popular astronomy podcasts, Astronomy Cast. Follow her on her blog, Star Stryder.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Nathan Eaton and dedicated to my wife, Linda, and her peer educators at the Dallas Museum of Nature and Science planetarium for the joy and wonder of the night sky they bring to children of all ages in North Texas.

Transcript:

Hello and Welcome to 365 Days of Astronomy Jan 26, 2010. This is Pamela Gay from Astronomy Cast.com. On this cold and snowy day, I want to share with you three of my favourite winter objects.

From wherever you are in the world, you can find Orion the hunter hanging in the sky toward the equator. Near Orion are the Pleiades and the Hyades cluster, When I show these objects to my students, I always tell them “these are snap shots in the evolution of open clusters.” Each of these systems is the home of young stars, bu t they are all very different in age.

One of the things about the science of astronomy that can be very frustrating is we don’t get to do experiments. I can’t mixup a star growing solution in my lab and raise of little blue giants or sun-like stars in a petri dish. Instead, to understand the life of a star, I have to peer around the sky and hope I can piece together what I see just right to solve the mysteries of where stars come from.

This isn’t all that different from trying to imagine the life of a human from going to the mall. Looking around, you’ll learn that infants can’t walk as you watch larger humans push and carry the little ones about. And you may learn that often the oldest can’t walk either. You’ll see how people grow and guess at how hair color changes and skin texture changes correspond to age. In that single look around the mall, you won’t be able to watch a single life go from new born child to aging geriatric, but you can build an understanding by observing hundreds of snapshots of what life looks like in all its different stages.

Astronomers live too short a time to capture in a single life any meaningful change in the populations of stars that evolve over out heads. But that’s okay, instead of seeing any 1 object evolve, we are instead given the chance to measure millions of stars in this moment and build an understanding of stars in all the fabulous varieties come in.

The stellar nurseries of the Orion, Pleiades and Hyades clusters are three places where in single images we can capture an entire generation of stars in all their possible forms, and each of the systems gives us a glimpse at a different age.

The Orion nebula is very much the stellar nursery, with stars just 10 million years old or younger. The Pleiades, well, it’s more like a day care center with stars ranging up to 100 million years old. And Hyades – it’s the afterschool program for stars as old as 730 million years of age – and looking a Hyades you can watch as the young teens make their break for freedom, leaving home as fast as they can.

In their youth these stars still gather in clumps. But, as they age, the stars will drift apart until, as adults, they have no memory of the place they were born. Our Sun is one of these solitary stars and every time I introduce my students to these three open clusters, they ask what happened to the open cluster where our Sun was born. The truth is, that cluster and our Sun had a falling out.

Once upon a time, somewhere in our galaxy, our Sun’s atoms were part of a giant molecular cloud. Approximately 7 billion years ago, that molecular cloud was bumped. Exactly what did the bumping no one knows. That anonymous bump so shocked the dark molecular cloud that in recoiled and collapsed in on itself. At first this inward spiral wasn’t at all dramatic, and an imaginary space traveler looking at this shocked cloud with her imaginary eyes might not have perceived the motion. Over time, however, momentum built up, and the collapse gained speed, with the densest parts of the cloud pulling themselves into fragments, as more ethereal parts were left behind to collapse more slowly. In one of these collapsing regions a womb of gas and dust that was neither too big nor too small began to glow as a single star exhaled its first breath of heat. As it grew and began to illuminate its surroundings, a disk formed; a disk containing just enough stardust to someday form 8 planets and a lot of harder to categorize smaller bits.

While this star, which would come to be called “The Sun,” was busy forming, its nursery mates were similarly busy growing, glowing, and in some cases even going an extra step and exploding. This stellar nursery was filled with screaming stars that wept radio waves and threw off high energy jets as they tried to find their way onto the main sequence. While these stars wailed and grabbed at matter, they also traveled as a pack around the galaxy. While we can’t do more than guess at the Sun’s original orbital position, we know that today it takes about 135 million years for the Sun to orbit the galaxy. Let’s assume for a minute that the Sun emerged from the center of of that cluster. This would put it in a position to watch some of its nursery mates race ahead around the galaxy, take less time to orbit, while other of its nursery mates slowly fell behind, taking longer to orbit (and a few just explode themselves into oblivion as supernovae). After a few orbits and a few hundreds of millions of years, these differences in speed caused the fastest (and slowest) stars to fall out of the cluster, as their positions no longer made it possible for the casual observer to match them up with their cluster of origin. Over time, differences in orbital velocities drew more and more of the stars away from their siblings. Eventually, it became impossible to tell exactly which stars made up those sibling stars to the Sun.

The Sun, like its sisters and brothers, simply fell out of the cluster as it raced around the galaxy, just as a runner might fall away from the pack.

We are an orphan system, alone in the galaxy. Unlike the majority of stars, our Sun has no companion. Having escaped the chaos of our home, we are now simply alone.

Today, astronomers around the world want to find our lost siblings. One of the wonderful thing about comeing from a cluster is all those stars are made from the same mix of gas and dust. Our siblings contain the same mixture supernovae rement, exhaled steller wind materials, and primordial atoms that we contain. As we look around, it is possible to very carefully measure the mix of elements that make up the stars around us, and guess at who are relatices may be.

Sadly though, while we can easily identify stars of no relation, the fingerprints of elements aren’t as unique as the genetic fingerprints that allow humans to sort out family relaships. At best we can do is identify stars that appear to be moving like you expect a sibling to move, and appear to be made of what a sibling should be made of, and label these stars as possible relations.

It is a start, tomorrows scientists and tomorrows next generations of astronomers, may be able to improve on these beginnings and find our lost solar family.

If you liked this story and want to learn more about astronomy, please tune in to astronomy cast, or read text versions of stories like this one on my blog. www dot starstryder (with a y) dot com. www.starstryder.com

End of podcast:

365 Days of Astronomy
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