by S. Prasad Ganti

Stellar nurseries are places in a galaxy where star formation is taking place. Very much like all living beings, stars are born and die. Huge clouds of gaseous hydrogen, embedded with dust particles,  are the source for star formation. Some of these clouds span several light years. Over a long period of time, gravity does its magic compressing the gas cloud to lead to a stellar nursery.       

Star formation leads to planet formation. And a new solar system is born. The number of planets and their proximity to the parent star, depends on a lot of factors. Some of the combinations lead to a goldilocks zone like ours where a planet developed life. Thousands of exoplanets are being discovered around other stars. Given billions of galaxies with billions of stars in each, it is statistically likely that life exists elsewhere in our Universe. The form and level of life may be different. It may or may not be carbon based life like ours is. May not be intelligent or may be a super intelligent life form. The timing could be different as well. Some of them could have had their peak and may be extinct, some may be in peak, and some may be yet to come. Shown below is the picture of a stellar nursery as captured by James Webb telescope, courtesy NASA. There are about 50 new stars lighting up in the picture. 

The gas clouds start off as a huge collection of atomic hydrogen. Atomic hydrogen is the simplest element in the Universe with one proton in the nucleus and one electron orbiting. Such clouds do smash into each other and form a cloud of molecular hydrogen. A molecule of hydrogen consists of 2 hydrogen atoms. As gravity acts on such a cloud, a structure emerges which has long filaments connecting some dense cores. In a cloud, some areas become dense statistically which form the cores. While the lighter parts become the filaments. The dense cores become the sites of star formation. The cores get compressed by gravity further and further before they light up the nuclear furnace and start giving out radiation including light. 

What sets the rate at which stars are born in a galaxy ? Obviously the raw material is a huge amount of gasses which need to come together. Earlier galaxies had primordial hydrogen. Later ones got gasses from explosive deaths of stars. When the gas gets depleted in a galaxy, the star formation comes to an end. And the galaxy begins to die as the death of stars is more than births. Like the population of the countries decrease when the births reduce in relation to deaths. Yes, galaxies are born and galaxies die, like stars. We know our Universe was born, it will probably die some time in the distant future. 

Our galaxy, the Milky Way, produces stars at a leisurely pace of about three solar masses’ worth of stars every year. But so-called starburst galaxies that flourished in the early universe had high star-formation rates that are tens or hundreds or thousand times that of ours. 

The dynamics inside such huge gas clouds depends on gravity, turbulence, radiation and magnetic fields. Observing such a gas cloud is not easy. Any visible light gets absorbed by the dust in the cloud and all we see is a dark patch.  But radio waves and infrared waves pass through. The radio telescopes and infrared telescopes are our best bet to observe such gas clouds. Like the James Webb telescope which operates in the infrared region.           

Based on the observations made, mathematical models are built on how the gas clouds behave and progress. Gravity is the weakest of the four known fundamental forces (electromagnetic force along with the nuclear forces of strong and weak interactions are the other ones). Yet this weak force is what sculpts the structures of our Universe. 

A recent article in Scientific American spoke about how the results from the mathematical models, like the shape, is used to 3D print an object which can be held in one’s hand ! A stellar nursery being held in a hand!