The little “eggs” have baby stars in them. Photo Source

A lot.

The Hubble space telescope has been in orbit for almost 25 years, and some of the information it was revealing was available back then. But newer space telescopes, and some on the ground, have yielded far more information. For one thing, the newer telescopes cover a far larger fraction of the electromagnetic spectrum than Hubble, which is essentially a visible-light scope. Newer instruments take pictures in wavelengths from radio waves to x-rays, giving a far better picture of the life cycle of stars than was available when I was teaching.

A planetary system forming. (The black center is a mask over the star.) Photo Source

Some things have stayed the same. A star’s mass is still its DNA, controlling its life cycle, its color, its luminosity, and what elements it is able to produce. It is still true that nuclear fusion within stars, and the violent explosions that mark their deaths, produce virtually all of the elements except the hydrogen and helium we inherited from the big bang. But improvements in both observations and computer simulations have taught us far more than we knew when I was teaching.

The course is designed for non-scientists, and there were times I was bothered by the anthropomorphism applied to stars. But at the same time, I learned a lot. We knew that certain gaseous nebulae were cradles of star birth, but now we can peer into those nurseries with infrared and see individual infant stars. We know that stellar birth is often, perhaps most of the time, associated with the production of a family of planets. We are beginning to understand much more about the details of the stellar deaths that lead to planetary nebulae, and the more violent ones that produce supernovae and black holes.

If you are interested in the stars, and want to know more of what we have learned in the last fifteen years, this course is worth watching.