Plasma ‘Soup’ May Have Allowed Ancient Black Holes to Beef up to Supermassive Proportions

How ancient supermassive black holes grew so big so quickly is one of the biggest mysteries hanging over astronomy — but now researchers think they know how these behemoths packed on the pounds.

John Wise, Georgia Tech

Supermassive black holes are the most extreme objects in the universe. They can grow to billions of solar masses and live in the centers of the majority of galaxies. Their extreme gravities are legendary and have the overwhelming power to switch galactic star formation on and off.

But as our techniques have become more advanced, allowing us to look farther back in time and deeper into the distant universe, astronomers have found these black hole behemoths lurking, some of which are hundreds of millions to billions of solar masses. This doesn’t make much sense; if these objects slowly grow by swallowing cosmic dust, gas, stars and planets, how did they have time only a few hundred million years after the Big Bang to pack on all those pounds?

Well, when the universe was young, it was a very different place. Closely-packed baby galaxies generated huge quantities of radiation and this radiation had a powerful influence over star formation processes in neighboring galaxies. It is thought that massive starburst galaxies (i.e. a galaxy that is dominated by stellar birth) could produce so much radiation that they would, literally, snuff-out star formation in neighboring galaxies.

Stars form in vast clouds of cooling molecular hydrogen and, when star birth reigns supreme in a galaxy, black holes have a hard time accreting matter to bulk up — these newly-formed stars are able to escape the black hole’s gravitational grasp. But in the ancient universe, should a galaxy that is filled with molecular hydrogen be situated too close to a massive, highly radiating galaxy, these clouds of molecular hydrogen could be broken down, creating clouds of ionized hydrogen plasma — stuff that isn’t so great for star formation. And this material can be rapidly consumed by a black hole.

According to computer simulations of these primordial galaxies of hydrogen plasma, if any black hole is present in the center of that galaxy, it will feed off this plasma “soup” at an astonishingly fast rate. These simulations are described in a study published in the journal Nature Astronomy.

“The collapse of the galaxy and the formation of a million-solar-mass black hole takes 100,000 years — a blip in cosmic time,” said astronomer Zoltan Haiman, of Columbia University, New York. “A few hundred-million years later, it has grown into a billion-solar-mass supermassive black hole. This is much faster than we expected.”

But for these molecular hydrogen clouds to be broken down, the neighboring galaxy needs to be at just the right distance to “cook” its galactic neighbor, according to simulations that were run for several days on a supercomputer.

“The nearby galaxy can’t be too close, or too far away, and like the Goldilocks principle, too hot or too cold,” said astrophysicist John Wise, of the Georgia Institute of Technology.

The researchers now hope to use NASA’s James Webb Space Telescope, which is scheduled for launch next year, to look back to this era of rapid black hole formation, with hopes of actually seeing these black hole feeding processes in action. Should observations agree with these simulations, we may finally have some understanding of how these black hole behemoths grew so big so quickly.

“Understanding how supermassive black holes form tells us how galaxies, including our own, form and evolve, and ultimately, tells us more about the universe in which we live,” added postdoctoral researcher John Regan, of Dublin City University, Ireland.

Life is Grim on the Galactic Rim

The White Star approaches the Shadow's homeworld of Z'ha'dum on the Galactic Rim.
The White Star approaches the Shadow’s homeworld of Z’ha’dum on the Galactic Rim.

It would appear that scientists have confirmed that the outer edge of the Milky Way is a bad location for life to even think about existing.

This research reminded me of the “Galactic Rim” in the 90’s sci-fi TV series Babylon 5. The Rim is the mysterious region of space right at the edge of our galaxy where only the hardiest of explorers dared to venture. As explained in the season 2 episode of B5, “In the Shadow of Z’ha’dum,” Captain Sheridan (Bruce Boxleitner) discovers that his wife (when exploring The Rim) went missing on a planet called Z’ha’dum. It turns out that an angry ancient alien race — called the Shadows — lived on this mysterious world and their discovery led to them being used in all kinds of plots during the latter four seasons of this awesome sci-fi show.

However, the existence of any kind of life (let alone life as complex as the evil Shadows) in the badlands of the Milky Way is looking very unlikely.

Located some 62,000 light years from the core of our galaxy (over twice the distance of the Earth from the galactic centre), two very young star clusters in the constellation of Cassiopeia have been studied. Chikako Yasui, Naoto Kobayashi and colleagues at the University of Tokyo, Japan, found these clusters in a vast cloud of gas and dust called Digel Cloud 2. The stars inside these clusters are only half a million years old, and the majority of them should possess proto-planetary disks (which is characteristic of local star-forming regions). However, it would appear that these stars contain very little oxygen, silicon or iron (i.e. they have very low metallicity) and only 1 in 5 of the 111 baby stars analysed in both clusters have disks.

If proto-planetary disks are rare, this means there will be a rarity of planets. This is an obvious bummer for life to form. After all, Life As We Know It™ is quite attached to evolving on Earth-like planets.

So why are these young stars lacking proto-planetary disks, when local star forming regions don’t seem to have this affliction? The authors of the paper, soon to be published in the Astrophysical Journal, suggest that these stars did have disks, but some mechanism is rapidly eroding them.

The most likely scenario is that low metalicity proto-planetary disks are more susceptible to photoevaporation. Simply put, these disks evaporate when exposed to EUV and X-ray radiation from their parent stars far more rapidly than disks that are metal-rich.

Therefore, if an alien race was able to form, they’d be very rare or they’d be very different from what we’d expect “life” to be like (i.e. they thrive in low metalicity star systems). Sounds like the mysterious Shadow homeworld of Z’ha’dum would be a very rare sight on The Rim of our Milky Way after all.

Publication: The Lifetime of Protoplanetary Disks in a Low-Metallicity Environment, Chikako Yasui et al., 2009. arXiv:0908.4026v3 [astro-ph.SR]
via New Scientist

Mystery Blob Detected 12.9 Billion Light Years Away

The Himiko object, the most massive object ever discovered in the early universe (M. Ouchi et al.)

Take a good look, this is one of the most mysterious, massive objects ever discovered in the cosmos. We don’t really know what it is, but this thing is huge, spanning 55,000 light years across (the approximate radius of our Milky Way). What makes this all the more intriguing is the fact that this object formed only 800 million years after the Big Bang and it is 10 times more massive than the next biggest object observed in the early Universe. But what is it?
Continue reading “Mystery Blob Detected 12.9 Billion Light Years Away”

Star Formation: The Game

starformation

Dave Mosher, I’m pointing my finger at you for this late night effort! Usually I stay up late to write articles, but for the last 30 minutes I’ve been playing this game after Dave sent a message on Twitter saying he had been playing a “simple” and “addictive” star formation game. No kidding! I shouldn’t have even clicked the link. But like a caffeine-infused moth to a super-shiny flame, off I went for some simple star-creation fun.

It looks like the Star Formation game is part of Discover Magazine’s featured article about the mysteries of star birth (it’s a great read, check it out). The game is simple, yet captivating (despite a few minor bugs). You play the role of supernova progenitor, dropping some massive star fury on an unsuspecting nebulous cloud of hydrogen. According to the game developers, the situation is physically accurate, it is just up to you to create the perfect conditions for stars to form in the dense cloud. It would appear the lectures I attended on star formation paid off, as I speak I’m on top of the leaderboard with a whopping 21122 points (see the screengrab above, I saved it posterity, I doubt I’ll be at #1 for much longer).

I’m all for games with an educational element, and I can’t think of a better way to spend an evening (well, I can, but if you’re stuck in the office, this is a great alternative to work). I’m off to create some more stars, check out Discover so you can do the same (just you try to knock me from the #1 slot!).