Stars are a lot like people. They are born, and then go on to enjoy a playful childhood and active youth–but, eventually, stars calm down when they evolve into glaring adults. However, the inevitable occurs when a star grows old and dies. Stars that are more massive than our Sun end their stellar lives when they explode in brilliant, violent supernova blasts. After the catastrophe, the erstwhile massive star leaves behind a dense, city-sized object termed a neutron star. Neutron stars are so dense that a teaspoon full of neutron star material can weigh as much as a herd of zebra. However, the most massive stars in the Universe have a different fate. When these especially massive stars run out of their necessary supply of life-sustaining nuclear-fusing fuel, they collapse into the oblivion of a black hole of stellar mass.
Less massive stars, like our Sun, come to the end of the stellar road more peacefully, without the brilliant grand finale fireworks display of their more massive stellar counterparts. When stars like our Sun live alone, without a binary companion, they first evolve into red giants that ultimately blow off their outer layers to become white dwarfs encircled by a beautiful shell of multicolored gases.
All stars, regardless of their mass, are kept brilliantly bouncy as a result of an enduring battle between gravity and radiation pressure. Gravity tries to pull all of the star’s material in, while radiation pressure tries to push everything out. This delicate balance between the two eternal foes goes on from stellar-birth to stellar-death. In the end, when the old star runs out of its necessary supply of nuclear-fusing fuel, it can no longer churn out radiation pressure to counteract the relentless and merciless pull of its own gravity As a result, gravity wins the war, and the star is doomed.
Today, our Sun is a lonely star, but it was probably not born that way. Our Star probably formed as a member of a heavily populated open cluster, along with thousands of other newborn, fiery sibling stars. Our Sun was either gravitationally evicted from its natal cluster due to interactions with others of its fiery kind or it simply peacefully floated away into the space between stars approximately 4.5 billion years ago. Likewise, our Sun’s long-lost siblings are thought to have migrated to more remote regions of our Milky Way Galaxy, never to return.
Our entire Solar System emerged from the tattered remains left over from the nuclear-fusing ovens of previous generations of dead ancient stars. Our Sun–like others of its kind–was born within a dense, cold blob tucked tenderly within the whirling, swirling, ruffling folds of a churning dark, giant molecular cloud. The dense blob ultimately collapsed under the intense pull of its own gravity, thus giving birth to a hot, glaring baby star (protostar). Within the secretive depths of these enormous and beautiful clouds, that float like lovely, eerie phantoms throughout our Galaxy in huge numbers, fragile threads of material tangle themselves up together, and the resulting clumps grow ever larger and larger for hundreds of thousands of years. Then, pulled inward by the relentless crush of gravity, the hydrogen atoms existing within the clumps rapidly and dramatically fuse. This process of nuclear fusion triggers a violent conflagration that will rage with brilliant fury for as long as the new star lives–for that is how a star is born.