Inside the Nurseries: The Birth of Stars
Look up at the night sky, and you get the impression of stability, serenity, a fixed eternity. Nothing could be further from the truth. The universe is hugely dynamic and everything is moving. Supernovae go off, galaxies collide, black holes devour anything that approaches. Stars are constantly dying and being created.
Massive clouds of gas and dust like this one
are the birthplaces of the universe's stars;
when supernovae shockwaves hit the
clouds, huge fragments of the nebulae
collapse and trigger the formation of stars.
Photo: Canada-France-Hawaii Telescope
Those births take place inside the universe’s “stellar nurseries.” It’s a quaint term, evoking nursemaids and rocking horses, and hardly does justice to the spectacular clouds of gas and dust that breed new stars. Inside those vast molecular clouds, the children of the universe come to life when huge fragments of the clouds collapse, triggering the formation of dense orbs of fusing hydrogen—in other words, stars. Why do the parent clouds collapse? The working theory is that they crumple when hit by shockwaves from nearby supernovae.
Actually seeing the nascent stars inside those nebulae is no easy business: Galactic dust might be a progenitor of the stars but it is also the enemy of the astronomer, for it absorbs visual light and obscures everything within it. Galactic dust doesn’t absorb all light, though. At infrared and radio wavelengths, it absorbs very little. If you use the long radio waves of Mauna Kea’s SMA Submillimeter Array, for example, or the infrared of the NASA telescope to look at stellar nurseries, you can see through the dust and to the stars.
Astronomers on Mauna Kea are using the mountain’s telescopes to observe the genesis of stars, investigating how frequently they’re born, how massive they can become, how long they take to form. (The answer to that last: Anywhere from one hundred thousand to two million years.) And they’re studying larger patterns in star formation, too. For example, at certain times in the universe’s existence, large numbers of stars formed; at other times, including now, very few. Another discovery: Stars are not uniform—some are lighter, some heavier—but across the galaxies, the ratio of lightweight to heavyweight stars seems to hold true wherever you go. What does that suggest, astronomers wonder, about homogeneity, universality and the worlds those conditions might create?