NASA’s Retired Spitzer Space Telescope Shows Us Where Stars Are Born

NASA’s Retired Spitzer Space Telescope Shows Us Where Stars Are Born

NASA’s Spitzer Space Telescope retired earlier this year, but for astronomers, the mission isn’t over yet. They’re still studying a wealth of astronomical data, which the telescope collected and sent home faster than a full staff of humans and computers could analyze it. Researchers working through the data Spitzer left behind recently unearthed a detailed image of a nebula where some of the most massive stars in the galaxy are spawned.

If you could see the nebula W51, it would stretch across a patch of night sky about as wide as the full Moon – despite being 17,000 light years away. The Moon looms so large in our night sky because it’s so close: about 1.25 light seconds. W51, if it were visible in the wavelengths of light our eyes can see, would loom just as large because it’s actually enormous, even in cosmic terms: about 350 light years wide, encompassing dozens of stars.

But you can’t see W51, and neither can telescopes that see the universe in the same wavelengths of light as your human eyes. Physicists call this the visible spectrum, which is definitely going to confuse any alien species we eventually meet who can see in ultraviolet or infrared (which is pretty plausible; several Earth species do it). Unfortunately, other dust clouds in the 17,000 light years of interstellar space between us and W51 block the visible light from the nebula. Radiation with longer wavelengths, like infrared and radio waves, can penetrate those interstellar dust clouds – which is how astronomers with radio telescopes discovered W51 in 1958, and how Spitzer observed the nebula’s infrared radiation in awesome detail, revealing a cosmic wonder that would otherwise be invisible to us.

“The really spectacular images provided by Spitzer via the GLIMPSE survey – in concert with data from many other, complementary telescopes – give us insight into how massive stars form in our Milky Way and then how their powerful winds and radiation interact with the remaining ambient material,” said California State Polytechnic University, Pomona, astrophysicist Breanna Binder in a NASA press release. “Regions like W51 are really important for advancing our understanding of star formation in the Milky Way, which we can extrapolate to how a star formation proceeds in other, nearby galaxies.”

Nuclear Fires And Supernovae

The gas clouds of nebula W51 could swallow our solar system thousands of times over, and within their vast swirls and billows, massive new stars are flaring to life, burning brightly, and dying in spectacular explosions.

In nebulae like W51 (the word “nebula” just means “cloud” in Latin), molecules are gathered together just closely enough for gravity to start pulling them together into clumps. As molecules fall together, their shared gravity pulls in even more molecules, and eventually they coalesce into gas giants like our solar system’s Jupiter. If the newly-formed gas giant gathers up enough material, something spectacular (and a little terrifying if you think about it too much) happens: the force of its own mass pressing inward actually crushes hydrogen atoms together so tightly that they fuse into helium. That’s called nuclear fusion, and it puts out a tremendous amount of energy.

For the record, Jupiter would need to pull in enough material to make itself about 1,000 times bigger in order to become a star like our Sun – but with just 80 times more mass, it could become a smaller, cooler red dwarf star like Proxima Centauri. Neither one is going to happen, because the available gas and dust within Jupiter’s gravitational reach has already been gobbled up (sorry, Jupiter).

But in huge nebulae like W51, newly born stars can keep growing as more and more gas falls inward toward their burning nuclear cores. Some are 16 to 120 times the mass of our Sun and 10 to 200,000 times brighter, blazing a brilliant blue-white and blasting out intense ultraviolet radiation. Astrophysicists call these O-type stars, and they’re the largest, brightest, and rarest stars in the galaxy. Only one in every few hundred main sequence stars becomes an O-type, and there are at least 30 of them in the W51 nebula.

W51 is exactly the type of cosmic neighborhood you’d expect to find these massive, bright, hot stars in; they turn up most often in regions of active star formation in the spiral arms of galaxies. That’s exactly what W51 is: one of the most active star-forming regions in the galaxy, located just a bit closer to galactic center than Earth, along the same spur of star systems branching off one of the galaxy’s spiral arms.

The hotter and brighter a star burns, the sooner it burns out. For massive O-type stars, that takes just a few million years. And it nearly always ends violently, in a spectacular explosion called a supernova, which blasts most of the star’s mass out into space and leaves behind a black hole or a small, dense, burned-out stellar husk called a neutron star. Blasting all that gas out into a nebula like W51 can trigger new waves of star formation, starting the whole process over again.

That’s been going on for generations in W51. If you look at the red area on the right side of Spitzer’s image, you can see where stellar winds from living stars and supernovae explosions from dying ones have carved out huge chunks of the surrounding cloud.

A GLIMPSE Of The Cosmos

Spitzer collected the infrared light that eventually became this false-color image – and a lot of less aesthetically pleasing but more useful numerical data for scientists to work with – in 2004, when the telescope was working a project to map the large-scale structure of our galaxy. That’s a difficult thing to do from within the galaxy (sort of a “can’t see the forest for the trees” problem), but the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire made tremendous progress.

In the process, Spitzer observed some smaller (relatively speaking) features of the galaxy, like W51. Not bad for a telescope that retired in January.

Source Article