#star-formation

This Is Why 'Pillars' In Space Mean Destruction, Not Creation

“In the heart of the Eagle Nebula, the iconic Pillars of Creation loom as one of Hubble's greatest all-time sights. But very little is still being created in there, compared to the destruction that's taking place. It's true: there are new stars being formed inside, as the gas gravitational collapses down to grow the largest clumps of matter. But the reason you have a pillar shape at all is because of nearby, bright, external stars, which boil the gas away.”

Just because you have newly-forming proto-stars inside of you doesn’t mean you’re creating new things. You could, instead, be at the very end-stages of creation, where you’ve finished creating ~99% of everything your star-forming region is ever going to create, and only the last remnant stage — that of destruction — is left. Instead, these gas clumps are the final vestiges of an environment that houses already-born stars, in the process of boiling off. These gas globules aren’t collapsing and giving rise to stars; they’re evaporating away. What we’re witnessing is the aftermath of creation, not the start of it.

What Was It Like When Galaxies Formed The Greatest Number Of Stars?

“The star-formation rate declined slowly and steadily for a few billion years, corresponding to an epoch where the Universe was still matter-dominated, just consisting of more processed and aged material. There were fewer mergers by number, but this was partially compensated for by the fact that larger structures were merging, leading to larger regions where stars formed.

But right around 6-to-8 billion years of age, the effects of dark energy began to make their presence known on the star formation rate, causing it to plummet precipitously. If we want to see the largest bursts of star formation, we have no choice but to look far away. The ultra-distant Universe is where star formation was at its maximum, not locally.”

In a myriad of locations, throughout our galaxy and almost all the galaxies in the known Universe, new stars form wherever a cloud of gas is triggered into collapsing. From the Orion Nebula to dozens of others in our own galaxy, new stars form thousands-at-a-time in regions all throughout our local neighborhood. But as spectacular as these sights are, they’re much, much rarer than they were a long time ago. In fact, we formed stars at a rate that was 30 times faster than today back when the Universe was young. For the last 11 billion years, we’ve been forming fewer and fewer stars everywhere we look.

New Stars Turn Galaxies Pink, Even Though There Are No 'Pink Stars'

“New star-forming regions produce lots of ultraviolet light, which ionizes atoms by kicking electrons off of their nuclei. These electrons then find other nuclei, creating neutral atoms again, eventually cascading down through its energy levels. Hydrogen is the most common element in the Universe, and the strongest visible light-emitting transition is at 656.3 nanometers. The combination of this red emission line — known as the Balmer alpha (or Hα) line — with white starlight adds up to pink.”

When you look through a telescope’s eyepiece at a distant galaxy, it will always appear white to you. That’s because, on average, starlight is white, and your eyes are more sensitive to white light than any color in particular. But with the advent of a CCD camera, collecting individual photons one-at-a-time, you can more accurately gauge an astronomical object’s natural color. Even though new stars are predominantly blue in color, star-forming regions and galaxies appear pink. The problem compounds itself when you realize there isn’t any such thing as a pink star! And yet, there’s a straightforward physical explanation for what we see.