Cosmic Fireworks

Big News in Distant Galaxies

You know that saying about how time is the universe’s way of keeping everything from happening at once? Well, there’s a lot happening in astronomy news today, almost all at once. So, the universe is flinging cool new stuff at us.

First, take a gander at this image. It’s an artist’s concept of what galaxies in the early universe were doing about 13 or so billion years ago.


Galaxies in the early universe grew fast by rapidly making new stars. Such prodigious star formation episodes, characterized by the intense radiation of the newborn stars, were often accompanied by fireworks in the form of energy bursts caused by the massive central black hole accretion in these galaxies. This discovery was made by a group of astronomers led by Peter Barthel of the Kapteyn Institute of the University of Groningen in the Netherlands. (Credit: ESA/NASA/RUG/MarcelZinger)

Yep, they were making stars at a prodigiously fast rate, more rapidly than many galaxies do today. By comparison, our Milky Way’s star birth factories create at an average rate of one new star a year. Ours is a pretty quiet galaxy in that regard. And, while we do have a black hole at the center of the galaxy, compared to other galaxies’ very busy black holes, ours is pretty tame. Only occasionally does it capture a star or gas cloud and gobble it up.

Now, if you look at more active galaxies, you see more  star formation. And these busy galaxies were much more common in the early universe.  So, it makes sense that astronomers would find galaxies at that time busily baking up stars. Quasars and radio galaxies are prime examples of these active galactic denizens.  And, observing them is easy due to their bright radiation, which can be detected over huge distances. Essentially, these active galaxies are easily detected through their luminous radio, ultraviolet or x-ray radiation, which results from steady accretion on to their massive central black holes.

These exotic galaxies are getting a lot of attention from the Herschel Telescope, which is sensitive to far-infrared wavelengths of light (which indicate heat radiation). A group of astronomers in the Netherlands has used it to study star birth in distant galaxies.  Basically, it looks for heat radiation generated by star and planet formation in our own galaxy, and also studies the same radiation from complete galaxies.  If a distant object is emitting strong levels of far-infrared radiation, then it’s a sure bet that the galaxy is undergoing massive amounts of star formation. And, by massive, I mean creating hundreds of stars each year.

These busy galaxies also have strong signals in radio frequencies, emanating from their central black holes. The black holes are busy growing (accreting mass and perhaps even merging), at the same time their host galaxies are creating whole batches of hot young newborn stars.  And all of it is happening billions of light-years away, showing us galaxies in some of the earliest epochs of the universe.

The take-home message here is that these kinds of active galaxies existed early in cosmic history.  They’re among the largest, most distant, most powerful and most spectacular objects in the universe. And, they give astronomers a look at what massive normal galaxies may have looked like in their infancy as they balanced the action of growing black holes at their hearts with the demands of star birth in other regions.  These are the kind of “baby pictures” of infant galaxies that give astronomers a deeper understanding of what happened “way back when” at a time when the universe was a baby.


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