Enlarge VLA image (right) of gas in young galaxy seen as it was when the Universe was only 870 million years old. Image: NRAO/AUI/NSF, SDSS
Enlarge VLA image (right) of gas in young galaxy seen as it was when the Universe was only 870 million years old. Image: NRAO/AUI/NSF, SDSS

Black Holes, galaxies

Which Comes First: Galaxy or Black Hole?

7 Jan , 2009 by


Do galaxies form first and then a black hole springs up in the center, or possibly, do galaxies form around an already existing black hole? That’s the cosmic chicken-and-the-egg problem astronomers have been trying to figure out. The answer? “It looks like the black holes form before the host galaxy, and somehow grow a galaxy around them. The evidence is piling up,” said Chris Carilli, of the National Radio Astronomy Observatory (NRAO), speaking at today’s press conference at the American Astronomical Society’s meeting. By observing with the Very Large Array radio telescope and the Plateau de Bure Interferometer in France at sub-kiloparsec resolution, the researchers have been “weighing” the earliest galaxies, ones that formed within a billion years of the Big Bang.

Previous studies of galaxies and their central black holes in the nearby Universe revealed an intriguing connection between the masses of the black holes and of the central “bulges” of stars and gas in the galaxies. The ratio of the black hole and the bulge mass is nearly the same for a wide range of galactic sizes and ages. For central black holes from a few million to many billions of times the mass of our Sun, the black hole’s mass is about one one-thousandth of the mass of the surrounding galactic bulge.

“This constant ratio indicates that the black hole and the bulge affect each others’ growth in some sort of interactive relationship,” said Dominik Riechers, of Caltech. “The big question has been whether one grows before the other or if they grow together, maintaining their mass ratio throughout the entire process.”

“We finally have been able to measure black-hole and bulge masses in several galaxies seen as they were in the first billion years after the Big Bang, and the evidence suggests that the constant ratio seen nearby may not hold in the early Universe. The black holes in these young galaxies are much more massive compared to the bulges than those seen in the nearby Universe,” said Fabian Walter of the Max-Planck Institute for Radioastronomy (MPIfR) in Germany.

“The implication is that the black holes started growing first.”

The next challenge is to figure out how the black hole and the bulge affect each others’ growth. “We don’t know what mechanism is at work here, and why, at some point in the process, the ‘standard’ ratio between the masses is established,” Riechers said.

New telescopes now under construction will be key tools for unraveling this mystery, Carilli explained. “The Expanded Very Large Array (EVLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) will give us dramatic improvements in sensitivity and the resolving power to image the gas in these galaxies on the small scales required to make detailed studies of their dynamics,” he said.

“To understand how the Universe got to be the way it is today, we must understand how the first stars and galaxies were formed when the Universe was young. With the new observatories we’ll have in the next few years, we’ll have the opportunity to learn important details from the era when the Universe was only a toddler compared to today’s adult,” Carilli said.

Carilli, Riechers and Walter worked with Frank Bertoldi of Bonn University; Karl Menten of MPIfR; and Pierre Cox and Roberto Neri of the Insitute for Millimeter Radio Astronomy (IRAM) in France.

Source: NRAO, AAS Press Conference

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Nancy Atkinson is currently Universe Today's Contributing Editor. Previously she served as UT's Senior Editor and lead writer, and has worked with Astronomy Cast and 365 Days of Astronomy. Nancy is also a NASA/JPL Solar System Ambassador.

15 Responses

  1. s0l says:

    If that turns out to be the case i find it very interesting philosophically…The creator born out of the destructor…

    I didn’t expect the Black Holes to be there first ; could it then be that something other than extreme gravity generates black holes?

  2. Chris Coles says:

    The core difficulty with existing theory is the age of the universe.

    Trying to define a theory that postulates the arrival of a massive object, a black hole, and then assuming that a very large mass of stars, formed from what we must assume is new mass “appearing?” from the surrounding intergalactic void, does stretch the imagination.

    We need a new theory.

  3. Dark Gnat says:

    I would imagine that in the early universe, which was denser, could have situations where enough matter could collect, and form directly into a black hole.

    Any stars the formed later would be attracted to the black holes.

    In fact, I’m betting that it wasn’t for black holes, matter would have been spread more evenly, and less stars would have developed.

  4. john webber says:


  5. HeadAroundU says:

    Chicken was first, then her egg. That means galaxy was first, then her blackhole. An egg before chicken wasn’t chicken’s egg. An blackhole before galaxy wasn’t galaxy’s blackhole. :)

  6. Robbb says:

    very interesting. A few questions: assuming that the early matter in the universe was much more packed together wouldn’t it make some sense for a lot of black holes to form b/c these massive ‘bunches’ collapse from the collective gravity? (I know I’m not using the right jargon.)

    Then, following that notion, the early black holes are eating and spewing lots of matter, helping stars to slowly begin to coalesce around them? The outer ring stars have the best chance to survive and have liveable planets.

    Or I way off, speculatively speaking?

  7. Robbb says:

    Looking back, it sounds like I’m saying same thing as Dark gnat…

  8. Steven says:

    What would be the definition of a Galaxy(a region of stars?) If that’s the case then the black hole was first.

  9. drbubo says:

    The Universe is shrinking. In an expanding Universe there would not be Black Holes. The red and blue shift do not necessarily indicate expantion, wit the same effort in can be accelerating shrinking too.

  10. Hiker 9965 says:

    If you have seen any of my post, you know that I don’t believe in Black Holes.

    But if they did exist, how could they possibly preceed galaxies? You would need a a large amount of matter congregating to feed the back hole. I would call that… a galaxy.

  11. OilIsMastery says:

    I’ll take a stab at this one. Since black holes do not exist in actual physical material reality I’ll go with galaxies.

    “…the ‘Schwarzschild singularities’ do not exist in physical reality.” — Albert Einstein, mathematician, 1939

  12. Jake says:

    Replying to drbubo, black holes do not give us enough evidence to suggest that the universe is shrinking, and black holes could easily exist in an expanding universe, it’s just that they would be rarer. Also, Red Shift dies not indicate acceleration, as far as I know, it indicates an object moving away.

    My question is, how come the black hole is not sucking in the galaxys, and by now, would the black hole have evaporated?

  13. SBS says:

    Let’s take this down a few notches. If black holes are at the center, then why is the Universe expanding? If black holes came in then everything formed around them, then wouldn’t everything be sucked into them sense that’s what they are known for? Speaking of that, If we have a black hole in the center of our galaxy, and a super massive one at that, wouldn’t the best way to verify that be by measuring to see if our galaxy in getting smaller because of it getting sucked into the black hole?

  14. samuek says:

    The black hole did exist..my father was was working with the top secret scientists in america,russia,europe and japan my father told me that the scientist are in the half way identyfying.I really Did Believe on him even i his son give me some proofs.id like to explain it to you but it will be hard im sorry maybe next time.

  15. Jeffery Keown says:

    Haven’t very large (up to 1000 solar mass) stars been detected at this distance?

    When they formed, they would be very short-lived, as there would have been plenty of matter around to accumulate. When they denotated after a few million years (in spectacular GRBs) they would form the cores of new galaxies.

    Therefore, Big Stars ->Big Black Holes -> Galactic Cores.

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