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american astronomical society, black holes

Wow! AAS is a Cosmos of Cool Information!

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Endless Possibilities!

So, I’m here at the American Astronomical Society meeting and in the first two days alone, we’ve been treated to fantastic images of distant galaxies (courtesy of Hubble Space Telescope) in-depth looks at the behavior of supermassive black holes in galaxy collisions, the discovery of new planets by the Kepler Mission, a fantastically touching talk by NASA Administrator Charles Bolden, and much, much more.  I  don’t know where to begin — it’s all so much fun and so exciting to learn about.  So, I’ll just plunge into a couple of stories in this entry and then work my way through the stuff that has been interesting me.

Before I get there, though, a word about today.  I have been doing little four-minute video segments called “The Astronomer’s Universe” for an online video news presentation called Astrocast.TV.  My latest segment is about the Pleiades — which I invite you to watch here.

So, for the AAS meeting, I decided to do a segment about the meeting itself, focusing on some of the big astronomy stories being announced here.  So, we (me, the producer Rich Mathews) and Chris Mathews (camera man extraordinaire), and science advisor Harold Geller spent today interview special folks like astronaut and now Deputy Director of Space Telescope Science Institute John Grunsfeld, Roger Windhorst (leader of a team that has taken the deepest yet image of the distant cosmos using HST), and a pair of black hole researchers, and a couple of other guests. It was quite an undertaking and I had a lot of fun doing it.  The segment will appear on February 1st, and I’ll keep you posted on when to go check it out.

Okay, aside from that, I’ve been going to paper sessions, press conferences, and visiting with astronomers. It’s a firehose of information and I’m catching a few drops as it goes by.  Here is a sampling from Day 1, starting with black holes.

Black Holes: We’re Waltzing, Shredding and Evolving Yer Galaxies

An image of the galaxy COSMOS J100043.15+020637.2 taken with the Advanced Camera for Surveys on the Hubble Space Telescope. The tidal tail of stars, gas, and dust shows that this galaxy recently merged with another galaxy, which brought two supermassive black holes into this galaxy

Black holes are curious animals in the cosmic zoo.  Half a century ago they were little more than theoretical constructs — looked good on paper, but none had been seen. Now, thanks to Hubble Space Telescope, Chandra X-Ray Observatory, countless radio observations, we know they exist — not because we see them directly, but because of their effect on material around them. Supermassive black holes exist in the centers of nearly all galaxies, and they affect the evolution of those galaxies — particularly when galaxies merge.

Today at the first press conference of the American Astronomical Society, we heard more about how black holes affect their enviroments — from the dance of dual black holes in galaxy mergers to black holes to  black holes shredding stars apart in the centers of old globular clusters.

The waltzing galaxy story is quite fascinating — it involves the collision of galaxy duos that each have a central supermassive black hole (and by supermassive, I mean a black hole with somewhere between a million to a BILLION times the mass of the Sun).  During the merger, the combined galaxies make a new, bigger galaxy, and the black holes slowly move in a stately waltz that takes on the order of a hundred million years for one swing around the cosmic dance floor.

Astronomers have discovered and studied 33 pairs of these waltzing behemoths and expect to find many more of them in survey data taken with such observatories as Hubble Space Telescope, and examined more closely in data taken with instruments on the Keck II telescope in Hawai’i.  One of the really interesting measurements taken with Keck showed that the black hole dancers are spinning around at speeds of a few kilometers per second (about 500,000 miles per hour)!  The galaxies they studied are about 4 to 7 billion light-years away from the Milky Way, which puts them at point in cosmic history when the universe was 7 to 10 billion years old.

They are not the brightest galaxies in the cosmos — most of them are gas-poor, which makes them tough to spot. But, their black holes are gobbling up material around them. As that stuff swirls into the grasp of the black hole, it gets heated and lights up. That light from the immediate environment of the black hole is what astronomers are detecting — as the two black holes and their accretion disks dance together at distances of about 3,000 light-years apart. They can also study the light to determine the speed at which the black holes are moving around each other — and through the universe. In at least one pair, the data show a stream of material being pulled out of one galaxy during the merger — and the dual black holes are clearly obvious.

A Chandra X-Ray Observatory image of an elliptical galaxy in the Fornax cluster that contains an ultraluminous X-ray source. That source is very likely a black hole that is plowing through a globular cluster.

In a few billion years, our galaxy and the Andromeda Galaxy will collide, and their supermassive black holes will enter into the same kind of dance. And, maybe there’ll be an astronomer in another galaxy watching it happen!

In another black hole study, astronomers found striking evidence in both x-ray and optical studies (with Giant Magellan Telescope and Hubble Space Telescope) of a white dwarf star that appears to have been torn apart by an intermediate-mass black hole. The action is taking place in a globular cluster — collection of very old stars crowded together in a small area of space. If this study bears out — that is, if it can be confirmed, it would be the first time such a class of black hole was found in this setting — and one of the few times an intermediate-mass object like this has been found.

This is all very exciting work — and it really shows how far we’ve come in 40 or so years — from black holes being mathematical ideas to actual detections and measurements of their activity in the centers of galaxies — and their influence on the shapes and evolution of galaxies.  I can’t wait to see what the next steps in the black hole saga will be!

astronomy, astronomy news, astronomy research, black holes, colliding planets, planet-forming scenarios

Starving Black Holes and Smashing Planets

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Life Sucked for Early Black Holes

Lots of big astronomy news is hitting the ether this afternoon. The first story to catch my eye is this one about how early black holes weren’t quite the gluttons for material that they were expected to be.  Since most galaxies have black holes at their hearts, this idea that the first ones couldn’t get enough to eat in the early universe has profound implications for how astronomers understand galaxy formation.

A computer simulation of x-rays produced by an early black hole and their effects on nearby gas clouds. Early stars ate up most of the gas, leaving little for the resulting black holes to feed on. Courtesy KIPAC/SLAC/M. Alvarez, T. Abel and J. Wise .
A computer simulation of x-rays produced by an early black hole and their effects on nearby gas clouds. Early stars ate up most of the gas, leaving little for the resulting black holes to feed on. Courtesy KIPAC/SLAC/M. Alvarez, T. Abel and J. Wise .

To get a handle on the black hole diet way back in the first million years after the Big Bang, astronomers at the Goddard Space Flight Center and the Kavli Institute for Particle Astrophysics and Cosmology, performed a supercomputer simulation of conditions back when the first stars and galaxies were forming — some 13 billion years ago.

“The first stars were much more massive than most stars we see today, upwards of 100 times the mass of our sun,” said John Wise, a post-doctoral fellow at NASA’s Goddard Space Flight Center in Greenbelt, Md., and one of the study’s authors. “For the first time, we were able to simulate in detail what happens to the gas around those stars before and after they form black holes.”

In the simulation, cosmic gas slowly coalesced under the force of gravity and eventually formed the first nassive, hot stars. They burned brightly for a short time and emitted so much energy in the form of starlight that they pushed away nearby gas clouds.

These stars could not sustain such a fiery existence for long, and they soon exhausted their internal fuel. In the simulation, one of the stars collapsed under its own weight to form a black hole.  since the progenitor star had either consumed or pushed away the rest of the gas cloud, the black hole was essentially “starved” of matter on which to grow.

So, the first black holes were on a pretty strict diet — but they still managed to produce x-ray radiation that kept nearby gas from falling in to the black holes.  This radiational also heated gas a hundred light-years away to several thousand degrees. When you get that kind of heated gas cloud, it can’t coalesce to form new stars — and so even though the black holes were starving, they contributed to the dietary cycle by starving nearby areas of any material from which to form new stars.  How does affect galaxy formation?  Well, starving out the star-formation process affects the growth of galaxies. Yet, we have galaxies now, and we’ve seen galaxies back then — so the next step is to understand how the first galaxies overcame this strict diet inflicted on them by their black holes. Stay tuned!

You can watch a nifty animation of the black hole starvation scenario here.

Planetary Collisions Spotted by Spitzer

Planetary collision -- an artists concept of a stupendous event! (Courtesy NASA/JPL-Caltech) Click to embiggen.
Planetary collision -- an artist's concept of a stupendous event! (Courtesy NASA/JPL-Caltech) Click to embiggen.

The other big story today that caught my attention is the infamous colliding planets announcement. Now, my friend Phil Plait over at BadAstronomy wrote a book called Death from the Skies that talks about all the ways we can die (or be seriously inconvenienced) by the cosmos — but I don’t think he covered colliding planets. Now that Spitzer Space Telescope has caught evidence of planets colliding around another star, he can add that one in to the next edition of the book.

So, what’s the story behind this discovery?

NASA’s Spitzer Space Telescope found evidence that a high-speed collision between two forming planets — one about the size of Mercury and the other about the size of our Moon —  occurred a few thousand years ago around a young star, called HD 172555.  This planetary system, which is about 100 light-years away from us, is still in the early stages of planet formation.

So, what evidence did Spitzer capture of this dramatic event?  When the collision occurred, lots of vaporized, melted rock and bits of rubble got thrown across immediate space. As you can imagine, such a collision causes lots of heat — and the infrared heat signature is something that Spitzer is especially good at detecting.

As the bodies slammed into each other at speeds upwards of 10 kilometers a second, a huge flash of light would have been emitted. Rocky surfaces were vaporized and melted, and hot matter was sprayed everywhere. Spitzer detected the vaporized rock in the form of silicon monoxide gas, and the melted rock as a glassy substance called obsidian. On Earth, obsidian can be found around volcanoes, and in black rocks called tektites often found around meteor craters.

At the end of the collision process, the larger planet was essentially stripped of its outer layers. It absorbed the core and most of the surface material of the smaller body. This is likely how Earth formed — by collision and accretion, some 4 billion years ago.  It’s probably very similar to how Mercury formed, and a similar collision contributed to the formation of our Moon. So, in a sense, the Spitzer observations are giving astronomers a very interesting look back to the birth of our own solar system.