Astronomers Peer Deep into Blobs in Space

galaxy evolution
A computer simulation of a lyman-alpha-blob object in space. It's being lit up by radiation from hot young stars being born in galaxies associated with the blob. ESO/STScI/Wm. Keck Telescope

Out in the depths of space, there's a blob that astronomers have been anxious to explain. It wasn't immediately obvious to them why it shined as brightly as it did. The blob (and it really is a blob) is called SSA22-Lyman-alpha-blob and it lies some 11.5 billion years away from us. That means that it looks to us now as it did some 11.5 billion years ago. SSA22-LAB appears to have two giant galaxies at its heart that are bursting with star formation activity. The whole region where this object and its galaxies lies is swarming with smaller galaxies. Clearly, something is going on there, but what? 

VLT and ALMA to the Rescue

This rare Lyman-alpha Blob is not exactly visible to the naked eye. That's largely due to distance, but also because the light it's emitting is visible to us here on Earth in infrared wavelengths and also in radio frequencies. The name "Lyman-alpha-blob" tells astronomers that the object originally radiated its light in ultraviolet wavelengths. However, due to the expansion of space, the light is shifted so that it's visible in infrared. It's one of the largest of these LABs to be observed.

So, astronomers used the European Southern Observatory's Very Large Telescope Multi Unit Spectroscopic Explorer to dissect the incoming light for study. They then combined that information with data from the Atacama Large-Millimeter Array (ALMA) in Chile. Together, these two observatories allowed astronomers to peek into the heart of the action at the distant blob in space. Deep imaging with the Hubble Space Telescope's Imaging Spectrograph and the W.M. Keck Observatory in Hawai'i also helped them refine the view of the blob. The result is an amazingly beautiful view of a blob that existed in the distant past but is still telling us its story today.

What's Happening at SSA22-LAB?

It turns out that this blob is one very interesting result of galaxy interactions, which create ever-larger galaxies. Furthermore, the two embedded galaxies are surrounded by clouds of hydrogen gas. At the same time, they are both cranking out hot young stars at a furious rate. Baby stars emit a lot of ultraviolet light, and that lights up the surrounding clouds. It's like looking at a streetlight on a foggy night — the light from the lamp scatters off the water drops in the fog and it makes a kind of foggy glow around the light. In this case, the light from the stars is scattering off the hydrogen molecules and creating the lyman-alpha blob.

Why Is This Discovery so Important?

Distant galaxies are extremely interesting to study. In fact, the more distant they are, the more fascinating they get. That's because very distant galaxies are also very early galaxies. We "see" them as they were as they were infants. The birth and evolution of galaxies is one of the hottest areas of study in astronomy these days. Astronomers know that it proceeds as smaller galaxies merge together with larger ones. They see galaxy mergers at nearly every part of cosmic history, but the beginnings of those mergers started back 11 to 13 billion years ago. However, the details of all mergers are still being studied, and the results (such as this lovely blob) are often quite a surprise to them.

If scientists can get a handle on how galaxies form through collisions and cannibalization, they can understand how these processes worked in the early universe. What's more, from observing other, newer galaxies that have been through the same process that this LAB galaxy is experiencing, they know that it will result in a giant elliptical galaxy. Along the way, it will collide with more galaxies. Each time, the galaxy interaction will force the creation of countless hot, young massive stars.  These 'starburst galaxies' show prodigious rates of star formation. And, as they evolve and die, they will also change their galaxy — seeding it with more elements and the seeds of future stars and planets.

In a sense, looking at SSA22-Lyman-alpha-blog is like looking at the process our own galaxy might have experienced early in its formation. However, the Milky Way didn't end up as an elliptical galaxy in the heart of a cluster as this one will do. Instead, it became a spiral galaxy, home to trillions of stars and many planets. ​In the future, it will merge again, this time with the Andromeda Galaxy. And, when it does that, the combined galaxies will indeed form an elliptical. So, the study of SSA22-LAB is a very important step in understanding the origin and evolution of all galaxies.