Visions from Hubble Space Telescope

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White Dwarf Stars on the Run!

an illustration of a globular cluster
Astronomers used Hubble Space Telescope to analyze 3,000 white dwarfs in the 47 Tucanae globular cluster, located 16,700 light-years away in our Milky Way galaxy's southern constellation of Tucana. Until these Hubble observations, astronomers had never seen the dynamical conveyor belt in action. NASA, ESA, and H. Richer and J. Heyl (University of British Columbia, Vancouver, Canada) Acknowledgment: J. Mack (STScI) and G. Piotto (University of Padova, Italy)

Feast your eyes on this gorgeous globular cluster. It's called 47 Tucanae, and visible to observers in the southern hemisphere. It contains hundreds of thousands of stars packed into an area of space about 120 light-years across. Hubble Space Telescope has looked at this cluster many times, with different instruments, to understand the types of stars it contains, and their behavior. The most recent study identified white dwarfs that are making a beeline out of the center "city" of the cluster and headed for the "suburbs". 

Why would they do this? The cluster has many massive stars that have migrated to its core. There they stay, happily shining for millions or billions of years. But, stars also age and die, and as part of the process, they lose mass. Some types of stars shrink down to become white dwarfs, once they've lost enough mass, they can move faster than when they were lumbering giants. They tend to pick up speed in their motions, and make their way out of the central core to the edge. 

By just looking at the cluster through binoculars or a small telescope, you really can't tell which stars have moved, but Hubble instruments can do the trick by looking at specific characteristics of the light coming from the different types of stars in the cluster. 

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A Galaxy Halo Surrounds Andromeda

graphic showing how astronomers look for gas around Andromeda
Astronomers using Hubble identified the gas in Andromeda's halo by measuring how it filtered the light of distant bright background objects called quasars. It is akin to seeing the glow of a flashlight shining through a fog. This finding promises to tell astronomers more about the evolution and structure of one of the most common types of galaxies in the universe. NASA/ESA/STScI

Not everything that Hubble Space Telescope sees turns into a pretty picture. Some of its most fascinating discoveries don't look like much at all. But, that's okay, because sometimes the best discoveries are hidden in plain sight.

Here's a good example. Astronomers used Hubble to look at light from distant quasars as it streamed past the Andromeda Galaxy. This is the nearest neighbor spiral galaxy in space and something you can see with the naked eye from a good dark-sky spot. The big question astronomers wanted to answer was: how much gas is shrouded around Andromeda?

It's commonly known that the space between galaxies isn't empty. In some places in the universe, it's filled with gas. That's the case with Andromeda. And, astronomers know that this galaxy is about six times larger and a thousand times more massive than they once knew. Since that mass wasn't obvious as stars or nebulae, what was it?

Astronomers programmed the telescope to look at those distant quasars. It's a little like standing in a foggy area and looking for the lights of distant cars. As the quasar light streamed through the gas surrounding Andromeda, it changed the light. The change isn't visible to our eyes, but to a specialized instrument called a spectrograph, it out quite well. and indicated was that Andromeda is surrounded by a halo of hot, diffuse gas. The mass of that gas is so high that it could make another half a galaxy's worth of stars. 

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Hubble Spots 13-Billion-year-old Light from Distant Galaxy

Light from the depths of time
A Hubble Space Telescope image of the farthest spectroscopically confirmed galaxy observed to date. It existed over 13 billion years ago. The near-infrared image of the galaxy (inset) has been colored blue as suggestive of its young, and hence very blue, stars. NASA, ESA, P. Oesch and I. Momcheva (Yale University), and the 3D-HST and HUDF09/XDF Teams

Here's another image that doesn't look like much until you understand what it means. Hubble Space Telescope focused on a point in space that contains objects that existed when the universe was about 13.2 billion years old. That's so long ago that the universe was just a toddler.

What is this object? It turns out to be the most distant galaxy ever spotted. It's called EGS-zs8-1, and at the time its light left, it was the brightest and most massive objects in the early universe. 

In the image, it looks like a faint, small blob, and its bright white and ultraviolet light has traveled across 13.2 billion years for Hubble, the Spitzer Space Telescope, and the W. M. Keck Observatory in Hawai'i to detect in near-infrared light. The galaxy's light has been dimmed and attenuated into infrared wavelengths as space stretches and it travels across that great distance. 

What's next for astronomers? They'll study the early stars in this galaxy to understand the role they played in the young universe.