Ultraviolet light plays an active role transferring energy from place to place, and helping move the cosmos along on its long journey from chaos to order.
Young stars at the heart of NGC 3603 bombard the surrounding gas with ultraviolet light
As we contemplate this grand cosmos from which we come, it is amazing to think that light itself is a force of creation.
The universe is a massive incubator of incredible things. Stars, planets, galaxies ... humans. But at its simplest, everything we see in the cosmos is just matter and energy pushed and pulled by the fundamental forces of nature into a huge variety of fascinating celestial objects.
Great cosmic masterpieces
Among the most impressive objects in the universe are nebulas. These are the jewels that decorate the arms of the Milky Way and other nearby galaxies. In a nebula, gravity sculpts brilliant swirls of gas and mysterious dark dust into new forms, sometimes even stars and planets. But gravity isn’t the only force at work. Light also comes into play, changing the nebula with its energy. As we contemplate this grand cosmos from which we come, it is amazing to think that light itself is a force of creation.
Here we are ... and this was us
The clouds of gas and dust where stars form tell the tale of our cosmic ancestry. Our own sun was born inside the blistering turmoil of a great nebula - light and life emerging from chaos. But how exactly did we come from this? Pressure and time. And perhaps something more.
Nebulas start out cold and dark. Simply atoms and molecules floating together in space. Gravity is the first force to act. The slightest disturbance, perhaps a gravitational nudge from a passing object, sets things in motion. The once loose clump of particles begins to collect, a tiny wrinkle in the smooth spacetime that, itself, begins to disturb the environment nearby. Like a snowball rolling downhill, the cloud attracts even more matter to it. Eventually, the particles are close enough to collide, and heat plays its hand.
Under gravity’s inexorable pull, tremendous pressure builds as incoming particles rush inwards. Then more collisions produce even more heat until eventually, the core of the collapsing gas cloud reaches millions of degrees. And the collisions spark nuclear reactions. Like flicking a switch, new stars flash into existence, announcing their arrival in a great burst of energy that radiates the nearby gas.
The pink-red hydrogen glow is a hallmark of star birth around our galaxy and others. But other elements can be ionized as well, creating a gorgeous palette of distinctive hues.
Our star emits energy in the visible and infrared parts of the spectrum, but it also produces a certain amount of ultraviolet light. We cannot see it, but ultraviolet light carries enough of a punch to damage human skin cells, posing dangers ranging from a mild sunburn to deadly skin cancer. Fortunately, the Sun does not produce much ultraviolet light. It simply isn’t massive enough.
The biggest and brightest stars in our galaxy flood their nebulas with a torrent of high-energy ultraviolet. This light stimulates the surrounding gases which, in turn, begin to glow. Light to make light.
Through a process called ionization, atoms of gas absorb and re-emit light energy by shedding and recombining with electrons. It’s the same process that happens inside a neon sign, just on a much larger scale. And each gas, constrained by the rules of atomic physics, produces a characteristic color.
A pool of glowing pink
The pink-red hydrogen glow is a hallmark of star birth around our galaxy and others. But other elements can be ionized as well, creating a gorgeous palette of distinctive hues. These glowing colors correspond to the gases that emitted them, such as helium, oxygen and nitrogen.
But the ultraviolet light does more than make gas in a nebula glow. With its high energy, ultraviolet light sweeps through the turbulent environment near young stars, carving deep cavities in the cloud, leaving only heavy dust behind. This dust can, eventually, be pulled into planets that might not otherwise have been able to form. By clearing away debris, ultraviolet light helps push the cycle of star and planet formation along. Possibly even creating potential new homes for life.
Looking out
Nebulas, the great clouds of the galaxy, are where we can see the universe’s processes laid bare. Stars living and dying side by side in electric cloudscapes that completely overwhelm our senses. Looking at these phantasms of gas and dust, it is humbling to think that this was once us. Our sun, our planets. Our stellar neighbors. All tamed out of a wild cloud, acting according to the absolute laws that govern the cosmos.
Gravity and light, pushing and pulling the raw materials of the universe into the myriad forms we see here today.
Forms that include us, sitting on our planet, looking out.