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All posts for the month September, 2012

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.

 

Star Formation is Gorgeous!

This new image from ESO’s La Silla Observatory shows part of a stellar nursery nicknamed the Seagull Nebula. This cloud of gas, formally called Sharpless 2-292, looks like the head of the seagull. Its bright glowing red color is due to strong radiation from a very hot young star lurking at its heart. The detailed view was produced by the Wide Field Imager on the MPG/ESO 2.2-metre telescope. Courtesy ESO.

When you look at a star, it’s hard to wrap your head around the idea that it came from a cold cloud of gas molecules and dust. Yet, that describes the nebulae where stars are born pretty well. Take the Seagull Nebula. It lies about 3,700 light-years away from us near the constellation Canis Major (the Big Dog) in the sky, and kind of looks like a sea gull with a bright spot or two in it. Those bright spots are newborn stars.  The image you see here was taken with the MPG/European Southern Observatory 2.2-meter telescope, using its Wide Field Imager.

This wide-field view captures the entire Seagull Nebula, formally called IC 2177. This view was created from images forming part of the Digitized Sky Survey 2. Courtesy: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin. (Click to enlarge.)

So, one part of this complex of gas and dust clouds makes up the head of the cosmic sea gull. It’s glowing brightly (in red, near the bottom of the image) . What causes it fluoresce like that?  See the star in the center of the image? That’s a hot young star that formed in the nebula and its strong radiation is heating the gases and causing them to glow.

There are other hot young blue-white stars that hatched here in this stellar nursery, and their light bounces off of dust particles and shows up as a blue haze.

One of the reasons that I’m so taken with images of star birth regions is that they are always so beautiful. That beauty belies the fact that stellar nurseries are places of great destruction. The birth of a star eats up the cloud material. It carves out caverns and spaces, and sometimes the formation of a huge star chokes off the formation of smaller sibling stars that haven’t yet emerged from their nebular cocoons.

Our own Sun was born in a cloud of gas and dust some 4.5 billion years ago. It likely formed with other sibling stars, which have moved on and taken up new spots in the galaxy.

So, when you look at gorgeous images of star birth regions, you’re seeing something similar to the place where our own solar system formed, where the elements that make up our Sun, planets, moons, rings, comets, asteroids… and us… concentrated together in the distant past.

It Begins Here at Home, Part II

One of the things I absolutely love about astronomy is that it’s just outside the door. You go out, you look up and you see things. During the day you know the Sun’s there, and part of the month you can also see the Moon.  At night, the stars are there for your exploration, along with the planets, and an amazing array of deep-sky objects such as nebulae.  What if you had such concentrated and perfect eyesight that you could look across more than thirteen billion light-years of space to some of the earliest galaxies and galaxy “seedlings” ever formed?  Well, people right here on Earth can do that. They’re using a magnificent time machine called the Hubble Space Telescope to do it.

The Hubble eXtreme Deep Field (XDF). My gosh, it’s full of galaxies! Courtesy STScI/NASA. (Click to embiggenate)

Over a period of ten years, astronomers have aimed the telescope at a patch of sky in the constellation Fornax and taken images of distant galaxies in that direction. They’ve essentially used HST as a big light bucket for a decade to collect faint light streaming from thousands of galaxies.

The resulting image is called the Hubble eXtreme Deep Field (XDF), and it has gorgeous spiral galaxies similar in shape to our Milky Way and the neighboring Andromeda Galaxy.  There are also large, old fuzzy red galaxies where the formation of new stars has shut down.

If you look closely at the large version of this image, you’ll find tiny, faint, and extremely distant galaxies sprinkled across the image. Think of these as the “seedlings” from which today’s  striking galaxies grew.

This whole image is basically a history of galaxy formation — from the first shreds of galaxies to the enormous and grand galaxies we see today in near-Milky Way space.
Hubble used two instruments to get this image. It took the Advanced Camera for Surveys and the Wide Field Camera 3 to get this level of detail from 2,000 images taken over a total exposure time of 2 million seconds spread out over ten years.  Why take so long?  The longer you look, the deeper you look, and the deeper you look, the further back in time you see. Thus, Hubble is really a time machine, showing us the distant universe — all the while orbiting Earth and sending back data and images to astronomers right here on the planet.  It’s really pretty amazing when you think about it.

To learn more about this image, surf on over to the Hubble Space Telescope Web site, and feast your eyes on bigger versions of this image. It’s worth exploring!