Bubbly Burp Tracks Giant Black Hole's Last Meal

Observations with a number of telescopes, including the Hubble, have now dated a kind of burp in the eating habits of the giant black hole at the center of our Milky Way Galaxy. It appears that about six million years ago, the central black hole "ate" a large cluster of stars and the neighborhood around it was energized by the process of the meal.

Black holes are regions where material (starting with dead stars) has collapsed so much, that nothing, not even light, can get out. The black hole at the center of our Milky Way now includes enough material to make more than 4 million stars like the Sun! It's what we call a "supermassive black hole" and lurks in the middle of our Galaxy like a giant speed trap for unwary stars or star groups that get too close.

As material is in the process of being "swallowed" by the black hole, it glows with desperate radiation, just before it falls in and disappears from view. A great bubble produced by the black hole as it ate its last serious meal has now been tracked by astronomers with much greater precision.

Just like the sound of the burp your uncle makes (after a heavy Thanksgiving meal) can travel through the dining room, so the bubble from this last meal can be seen traveling through the Galaxy like a giant expanding shell. The shell was probe by the Hubble as the light of distant objects raced through it and astronomers were able to measure the speed of the bubble's motion.

Six million or so years ago, it appears that a large clump of stars or gas (the raw materials of stars) was consumed by the black hole, making two "Fermi bubbles" in the Galaxy. Since then, the black hole has only been "snacking" -- tearing apart and eating an occasional star or random bit of gas. But no serious meal has made a big bubble from the mouth of the black hole since then.

Our diagram shows how in the six million years since that meal, the bubble has expanded at speeds of two million miles per hour and made a giant bubbles north and south of the black holes that extend for tens of thousands of light years. That kind of puts your uncle's last burp into perspective!

Big Day for Astronomy Discoveries: Gravity Waves, Alcohol and Tatooine 9

The national organization of professional astronomers (the American Astronomical Society) is meeting in San Diego this week, and there is BIG news from the meeting: More gravity waves, wood alcohol in space, and a big Tatooine-like planet.

Scientists working with LIGO (the Laser Interferometer Gravitational-Wave Observatory) have announced their second discovery of gravity waves. (The first was announced in February.) Once again they observed two giant black holes coming closer and closer and then merging into a bigger black hole. In the merger, some of the mass in the system is converted to energy, and comes out as the waves of gravitational energy Einstein predicted about 100 years ago.

The black holes that merged were 14 and 8 times as massive as our Sun, somewhat smaller than those in the first discovery. Scientists estimate that the black hole that came out of the merger had as much stuff as 21 Sun. This means an entire Sun's worth of mass was converted to energy -- explaining why we could detect the gravity waves, even though such waves are much, much weaker than other waves we know and love, like radio or x-rays.

In the second discovery, a team of astronomers from around the world used the giant ALMA array of radio telescopes in Chile to measure the presence of alcohol in the planet forming disk of a young star 170 light years away. Alas, the kind of alcohol they found is what we call "wood alcohol" or methanol, not the drinkable version. Still, this is the first detection of one of the complex building blocks of life in the region around a newly formed star that is making planets as we observe it.

We have found many of the basic chemical building blocks of life in comets, in chunks of rock that fall from space, and especially in the great clouds of raw material (gas and dust) from which new stars form. But this is the first time we see the "fingerprints" of such a molecule in the flat disk around a star which is the nursery from which planets like Earth and Jupiter emerge. The name of the star is TW Hydrae in case you want to search for more information. (Our image shows an artist's impression of the disk and the molecules of methanol.)

And, finally, in a discovery that is bound to warm the hearts of Star Wars fans everywhere, astronomers have announced the discovery of the ninth, the largest, and the furthest planet orbiting two stars. Such a world could have two suns in the sky at the same time -- just like Tatooine, Luke Skywalker's home planet.

The newly discovered planet, called by its catalog number Kepler
1647b, is about the size of Jupiter and takes three years to orbit its star. The star system is about the same age as our own. And most intriguingly, the new planet orbits in the "habitable zone" of the double star -- meaning that the temperature in the planet's neighborhood would be comfortable for water and life as we know it.

Now Jupiter-sized planets are probably mostly gas and liquid, like Jupiter is, and have no surface for life to evolve on. But such planets may have large solid moons, like Jupiter and Saturn do. On such moons, an atmosphere and oceans may form and remain, so that an environment for life may yet exist in this strange, beautiful system. (We can't find moons yet, only planets, so for now, we have to leave such thoughts to the science fiction writers.)

And those three are only the most interesting of the many discoveries announced at the meeting. We really do seem to be living in a golden age of observational astronomy!

Two Giant Black Holes Whirl at the Core of an Active Galaxy

Using the Hubble Space Telescope, a team of astronomers has found that a superbright (active) galaxy is powered at its core by two supermassive black holes whirling around each other in only a bit more than one year. This remarkable galaxy is called Markarian 231, after the Armenian astronomer who made a catalog of such active galaxies (with unusually bright centers.)

The galaxy is almost 600 million lightyears away, so we cannot see the tiny area in the center which contains the black holes directly. But a detailed study of the ultraviolet light from the core of the galaxy strongly implies that a black hole containing enough material to make 4 million Suns is whirling around a much larger black hole (with mass inside for 150 million Suns.)

Think about those numbers! You would not want to live near such overweight black holes, but luckily they are confined to the central regions of galaxies (including our own Milky Way) and are not a feature of the galactic outskirts where our solar system resides in comparative peace.

The idea that enormous black holes like this can share the same environment is not news to astronomers, but it's nice to have such a clear example. We now know that the giant islands of stars called galaxies probably all started much smaller and have been growing through "mergers" (if you'll pardon our appropriating a word from the world of business.)

Smaller galaxies are "eaten" by larger ones, or two galaxies of equal size are attracted together by their mutual gravity. If the smaller galaxies each contain a big black hole, both black holes will wind up near the center of the merged object. If the original galaxies had orbiting motion around each other, their inner black holes will have some of that motion, and can circle each other until -- later -- their gravity also pulls them together.

The fact that the two black holes in Markarian 231 take only about one year to go around means they will collide in a few hundred thousand years (a long time compared to the presidential nomination season, but short for galaxies.)

When two black holes collide you get -- surprise, surprise -- a bigger black hole. But we have caught Markarian 231 in the act of a small galaxy having been swallowed, but before the two black holes had time to merge. There are stars and huge clouds of gas and dust being pulled in by the pair of black holes and as they are torn apart and whirled around, they give off a lot of energy.

It's that energy of doomed material (before it falls into one or the other black hole) that makes Markarian 231's center so unusually bright.

The method used to find the waltzing, whirling black holes in this galaxy holds promise for finding other pairs of giant black holes in other distant galaxies. And the existence of such pairs of hungry black holes is good evidence that our merger theory of how galaxies "bulk up" is correct.

(By the way, our image, above, is a painting, based on the Hubble data.  As we said, we can't take a picture of the inner part of the galaxy.  But below is a Hubble image of the entire disturbed galaxy with its bright center.)

A Monster Misses a Meal

There is a monster at the heart of our Milky Way Galaxy.  It's a super-massive black hole that has already eaten enough material to make 4 million stars like our Sun!  And, like all black holes, it is still hungry.  

For material to be "eaten" by a black hole, it must come quite close to the black hole "mouth" which astronomers call its event horizon.  Because black holes are the most compressed (squozen) objects in the universe, even overfed monster black holes have relatively small event horizons. Astronomers estimate that the one at the center of our Galaxy is 80 to 100 million miles across.  That's roughly the distance between the Earth and the Sun and is a tiny space in which to put 4 million(!) Suns.

So material near our black holes must come close to that tiny region to serve as food for the monster.  Things further away, like stars, can orbit around the black hole and not get swallowed.  (It is from the movement of such close, but not doomed, stars that we can estimate the gravity of the black hole.)

For the last few years, astronomers who monitor the center of our Galaxy have been predicting that a snack is on its way to the black hole.  A dusty cloud of material which they have nicknamed G2 was going to have a close encounter of the worst kind with the black hole in May 2014.  It was going to be torn apart by the enormous gravity of the monster and some of its material was then going to provide a meal for the black hole.  

When gas clouds (or other food) fall into a black hole, they are whirled around with unbelievable speed just before they fall in, and tend to glow briefly with x-rays and other forms of radiation before they disappear in the event horizon. However, no such flare-up of radiation was seen, even when the world's largest telescopes (like the Keck in Hawaii and the European Very Large Telescope in Chile). 

It appears G2 was not torn apart and consumed, because it wasn't a loose cloud of raw material, but a star with some of its birth material still around it.   The star managed to hold on to its "stuff" and make it away from the black hole, depriving it of a meal at this time.  Sorry, monster.   Better luck next time.

(In the picture, you see G2 in different colors going around the black hole (which is invisible, but whose position is marked by the plus sign.)  The blobs are shown at different times, and are red when G2 was moving away from us, and blue now that it was flung around the black hole and is coming toward us.)

A Rogue Black Hole Escaping its Galaxy

Astronomers have announced the possible discovery of a big black hole that has escaped the galaxy of stars that gave birth to it, a phenomenon that had been predicted in theory, but not observed.

Galaxies (great islands of stars) that share a neighborhood in space can sometimes collide. If each has a big black hole at the center -- as many galaxies do -- usually the two black holes collide and merge. But, under the right conditions, the black holes can engage in a "game of pool" (billiards for those with more refined tastes.)

One of the big black holes can "recoil" or "rebound," and wind up being shot out of the combined galaxies. This is a pretty unusual circumstance, and astronomers have been searching for an example. Now, it looks like they may have found one.

The project involved observations with several telescopes, including the Swift satellite and the giant Keck telescope in Hawaii. The galaxy that remains is called Markarian 177 (a name that comes from a catalog of disturbed galaxies made by an Armenian astronomer.) The object that may be the escaped black hole has a number from the Sloan Digital Sky Survey catalog -- SDSS1133.

The galaxy is about 90 million light years away in the bowl of the Big Dipper. As shown on the accompanying image, the rogue object is about 2600 light years from the center of the galaxy.

As black hole fans are now probably thinking as they read this, it's not the actual black hole we are seeing on this highly magnified Keck infra-red image. Black holes are black and hard to see against the black of space. The SDSS object is a black hole surrounded by gas and dust that the black hole is "eating." It is the ring of "food" that we see glowing on the picture.

There is a small possibility that the SDSS object is something else entirely, such as an exploding star, although there is evidence from earlier images against that interpretation. Astronomers plan to use the Hubble Space Telescope to get even more information about this mysterious pair of objects.

If the black hole interpretation holds up, this will be a new creature in the "astrophysical zoo" to add to the many weird things we have been discovering lately. Rogue black holes are already in use in science fiction (such as Allen Steele's novel "Spindrift") and may now join the real universe as well.

The Movie Interstellar: The Science Behind the Story

Lots of my students are asking questions about the new film Interstellar.  I have been hearing about the movie for some time; the studio even sent me a “teachers’ guide” that was not especially useful, but piqued my interest.  Most exciting for me was the news that the scientific advisor (and one of the producers of the film) was Prof. Kip Thorne of Caltech, who is arguably the world’s expert on black holes and wormholes -- and designed the science behind the “galactic subway system” in Carl Sagan’s novel and film Contact.

I wrote to Dr. Thorne and he told me that he had indeed been involved with Interstellar, and had, in fact written a book, entitled The Science of Interstellar, to explain the complicated science that was the basis for some of the more intriguing scenes and events in the film.   The book also tells the story of the film, which was always supposed to be strong on science, and, at one time, was set to be directed by Stephen Spielberg.  But that original deal fell apart and it took a while to bring Christopher Nolan, the film’s current director, into the project.

Dr. Thorne wasn’t the only scientist involved in the long period before the movie went from an idea to a completed production.  Yesterday, I was talking with Dr. Frank Drake, the father of the scientific search for extra-terrestrial intelligence, and he told me that he was on one of the early panels of scientists brought together (with Stephen Spielberg) to make sure the plot stayed close to real science and possible science.

With Christopher Nolan and his brother Jonathan (a writer of screenplays) involved, the film evolved from the script Dr.Thorne and producer Lynda Obst had first envisioned, to include much more about a future Earth facing ecological disaster.  Still, the original thought, to portray black holes and worm holes as accurately as modern science can make it, was high on everyone’s list of priorities.

A black hole is a place where the death and collapse of a huge star has produced such strong gravity, that space itself is “warped” -- and nothing, not even light can escape.  Near a black hole, time proceeds more slowly than in the rest of the universe, and this change in the flow of time becomes a major plot element in the movie.  Both the existence of black holes and their strange effect on time have been demonstrated by many experiments and are well established.

A wormhole is more speculative, but something Einstein himself thought a bit about.   It’s a place where a black hole or some other unusual feature of space and time becomes a tunnel (or short cut) from one place in space to another place very far away, or even to another time.  In a wormhole, the dangerous effects you would feel falling into a black hole are somehow kept at bay, so that a spaceship can go through it to elsewhere or elsewhen.

Both wormholes and black holes get major roles in Interstellar.  The astronauts in the movie first use a wormhole to get from our Milky Way Galaxy to another galaxy far far away.   Then, they wind up in the new galaxy in a location where there is a massive, spinning black hole, with planets around it.  I won’t give anything else away, except to say that the special effects showing the wormhole and the gargantuan black hole were composed from calculations made by Dr. Thorne and his team at Caltech, fed directly to the computers of the special effects team for the movie – and they are truly SPECTACULAR.

For more, I recommend reading Dr. Thorne’s book (pictured in this post) and going to see the movie – especially if you are a black hole fan.  Dr. Thorne also has a web page with some animations at: https://interstellar.withgoogle.com/transmissions

A Baby Galaxy with a Grown-up Black Hole Inside

Using the Hubble and Gemini telescopes, astronomers have found a mystery --  a tiny galaxy that has a huge black hole in its center. That hungry black hole has eaten enough material to make 20 millions Suns!

The baby galaxy is really small -- its diameter is only 300 lightyears.  It's crowded in that little space; it contains about 140 million stars.  (Compare it with our Milky Way Galaxy, which stretches over 100,000 lightyears, and contains at least 200 billion stars.  Yet our central black hole has eaten only about 4 millions sun's worth of material.)  How could such a baby galaxy have such a big black hole?

Astronomers are no longer surprised to discover giant black holes at the centers of most galaxies.  Where a galaxy is most crowded (in its middle) is where a black hole (a star corpse with enormous gravity) has the most "food" to eat and can therefore grow.  But, in general, we have found that the larger a galaxy, the larger the monster black hole at its center.  So finding a baby galaxy sporting such a big black hole comes as a huge surprise.

A clue to this mystery comes from the name of the baby galaxy -- its awkward designation is "M60-UCD1."  UCD stands for ultra-compact dwarf (galaxy), which makes sense.   But M60 refers to the 60th entry in Charles Messier's catalog of fuzzy sky objects published in the 1780's.  That Messier catalog features some of the brightest and easiest to see galaxies and nebulae.   There is no way a tiny faint baby galaxy would have made his list!

It turns out that our baby galaxy is orbiting the much larger and brighter galaxy called M60.  In our picture, you see M60, a huge, blimp-shaped "grown-up" galaxy, which has its own super-massive black hole at the center.  You can see our baby galaxy in the inset of the photo. (You may need to click on the image to see it well.)

The fact that our baby galaxy is a "satellite" of the big galaxy may explain the mystery of its small size and big black hole.  The discoverers suggest that in the distant past, our baby was actually a big galaxy, with many more stars (explaining how it got its big black hole.)  But it had a "close encounter" with M60.  The gravity of the big galaxy stripped away its outer stars, leaving the "victim" of this encounter much smaller. 

If M60 took away and absorbed the outer layers of its neighbor, that would make M60 a cosmic cannibal.  That sounds awful, but in recent years astronomers have begun to realize that just about every big galaxy has grown to its present size by cannibalizing some of its smaller neighbors.  

It's a dog-eat-dog world out there among the galaxies, and the big bullies really get to throw their weight around.  Our little galaxy was once a more regular member of the galaxy club, but it lived in a rough neighborhood and got really beaten up by the local gravity bully.  Now it's a mere shadow of its former self.  

A Cluster of Stars Thrown Out of Its Galaxy at 2 Million MPH

A team of astronomers has discovered the first cluster of stars that has been thrown out of another galaxy. Whatever threw this rich grouping of stars out of the galaxy known by its catalog number as M87, was able to accelerate it to a speed of some 2 million miles per hour. Kids, don't try this at home without adult supervision!

It just so happens that the star cluster is being thrown roughly in our direction, but since M87 is 54 million light years away, no one is worried. The cluster will just wind up in the space between galaxies, wandering like the lost ships of legend, never finding its home port again.

M87 is a huge galaxy of stars and clusters, almost a million light years in diameter (our Milky Way Galaxy is about 100,000 light years across, by comparison.) In addition to thousands of billions of stars, M87 contains an estimated 12,000 "globular clusters" -- tightly bound groups of roughly 100,000 stars each. Our home galaxy only has about 150 of these globular clusters, and we are a pretty good-sized galaxy as far as cosmic requirements are concerned. So M87 makes us look like a 90-lb weakling in comparison.

So how did a cluster with many thousands of stars get loose from the considerable gravity of a giant galaxy like M87? No one knows for sure, but here is the clever idea that discoverers of the high-speed cluster are suggesting. Giant galaxies like M87 get bigger by eating smaller neighbor galaxies for lunch. Occasionally, they even merge with a big galaxy, gently pulling in the other galaxy's stars and other "inhabitants." What if M87, in the distant past, swallowed a big galaxy with a giant black hole at the center?

Astronomer have recently found that all big galaxies have big black holes in their crowded cores. The bigger the galaxy, the bigger the central black hole, in general. So M87 probably had a big black hole and the other galaxy would have had a big black hole too. As the two galaxies merged, their two black holes, like boxers circling each other in the ring, could have begun to orbit around each other. (We have seen pairs of big black holes in other such systems, so this is not a wild idea at all.)

Now, along comes our victim globular cluster, which had some orbit around the center of M87 that might well have brought it a bit too close to the pair of black holes. When the black holes interacted with the cluster, their gravity might have played a "game of pool" with it. In pool (or billiards, for some of you), you often see one ball interacting with another and then causing a third ball to go shooting off into a distant pocket. When the two black holes and the cluster had their moment of gravitational interaction, the cluster could have been thrown out of the galaxy by the tremendous gravitational energy of the giant black holes.

Astronomers have seen superfast stars thrown out of galaxies, but this is our first instance of seeing a whole cluster of stars shooting out from its home galaxy. M87 is one of my favorite galaxies anyway, with many other signs of violence and inner turmoil. This makes it even more interesting. The accompanying image is an artist's attempt to show the cluster coming out of M87, which is correctly shown as a fuzzy rounded blob.

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On a personal note, I would like to dedicate today's post to the memory of my good friend and colleague, Alan Friedman, the former director of the New York Hall of Science, who passed away this weekend.  Alan and I taught weekend courses on Einstein together, wrote papers on interdisciplinary approaches to teaching astronomy and physics, and bemoaned the state of science education in the U.S. over many dinners.  Alan also helped chart the course of the Lawrence Hall of Science in Berkeley, the Parc de la Villette science museum outside of Paris, and dozens of other museums and science centers where his advice was frequently sought.  He leaves an emptiness in the universe that will be impossible to fill.

Talk on the Work of and Crisis at Lick Observatory Now on YouTube

As you may have heard, the Lick Observatory (on whose Council I am now proud to serve) is being threatened by budget cuts at the University of California. Recently, Dr. Alex Filippenko (who was named the best professor at Berkeley a record nine times, and is a wonderful speaker) gave a very exciting talk on: "Exploding Stars, New Planets, Black Holes, and the Crisis at Lick Observatory". The video is now available on YouTube at
https://www.youtube.com/watch?v=JEY2pzxda1w

Lick Observatory, the first mountain-top telescope facility in the world, was founded in 1888, but continues to be a vibrant research facility and an important site for student and public education. Dr. Filippenko, who chairs the Lick Observatory Council, discusses some of the most exciting research being pursued at Lick, but also explains the funding crisis, what is being done by local citizens, and how you can help.

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Today's image is a snapshot I took at Lick, showing Dr. Filippenko (left) with noted venture capitalist Jim Katzman, standing in front of the Katzman Automated Imaging Telescope. It was with the use of this telescope that astronomers discovered a number of special exploding stars in other galaxies that could be used as distance markers for the universe. That work led to the discovery of the accelerating expansion of the cosmos and won the two groups involved the 2011 Nobel Prize in Physics. We can't let them shut this facility down, folks!

Happy Belated Einstein's Birthday (Get Ready for Spring)

Yesterday was Albert Einstein's birthday and this coming Thursday will be the Spring Equinox, when the length of the day and the length of the night are roughly equal, and we move from winter to spring in the Earth's northern hemisphere. This is always a good time of year to think fresh thoughts, something Einstein was especially good at.

At Foothill College, where I have the privilege of teaching, this is the week we begin registering students and community members for our spring quarter, which starts in April. This spring, I get to teach my evening Physics 12 class, nicknamed "Everything You've Wanted to Know about Einstein and his Work (without Math) but Were Afraid to Ask..."

If you, or someone you know, might be interested and are close enough to Los Altos, California to come to an evening class, I invite you to check it out.

Although Einstein died in 1955, his work continues to capture the imagination of both scientists and the public. In the last few years, astronomers have found new confirmation of some of Einstein’s most bizarre ideas -- including time itself slowing down under the right circumstances and gravity acting like the distorting mirrors of an amusement park. Huge black holes have been found, some of them having “eaten” enough material to make billions of Suns.

In the Physics 12 course, we explain all these ideas and discoveries in everyday language -- using analogies, visuals, and humor instead of math. Physics 12 will be offered on Tuesday and Thursday evenings from 6 to 8:30 pm, April 8 to June 24, 2014. Pre-registration is advised, but, if there is room, you can come hear the first lecture (room 5015) and then register if you like the approach. The class is held on the main campus of Foothill College in Los Altos Hills, just off Freeway 280. (For adults who don't need a grade, arrangements can be made, after you register, to take the course without the exams.)

For registration information for the Spring Quarter see:
http://www.foothill.edu/admissions.php

Physics 12 emphasizes key ideas that form the basis of our modern concepts of space, time, matter, and energy:
* The theory of how atoms work
* Energy, heat, and the arrow of time
* The special theory of relativity: what happens when you travel close to the speed of light
* The general theory of relativity: gravity, space-time warps, and black holes
* Quantum mechanics: the bizarre rules that govern the world inside the atom

In addition to examining the physics and physicists involved with these areas, the course also takes a brief look at the effects that such physics ideas have had on the humanities -- including poetry, fiction, music, and the public view of scientists. The quarter concludes the course with a non-technical introduction to the work of Stephen Hawking, whose innovative ideas combine these areas and take some of Einstein's ideas to the outermost limits of cosmic possibility.

For a course syllabus in pdf format, see:www.foothill.edu/physics/Physics.12.Web.pdf

Black Hole Research is One Key Reason You Have a Web Browser

Today, astrophysicist Larry Smarr (U of California, San Diego) received the "Golden Goose Award" at the annual meeting of the American Association for the Advancement of Science. The award was conceived to honor scientific research which seems, at first, to have little practical value, but turns out to have a major effect on human life or society. 

(The Golden Goose Award is meant to contrast with the old "Golden Fleece" award, which a former Senator used to give out willy nilly to research he couldn't understand or appreciate.)

In the 1980's, Dr. Smarr and his group were investigating black holes, places where the complete collapse of a dying star has created a warp in the fabric of space and time. Such bizarre star corpses were predicted by Einstein's general theory of relativity, but only reliably discovered in the 1970's. Calculating exactly how the messy collapse of one spinning star (or the collision of two black holes) would affect and change space and time nearby was a real challenge, and required the use of far bigger supercomputers than were available to academics like Smarr at the time.

Dr. Smarr proposed to the National Science Foundation that the US should create a civilian center for super-computing to crack really hard problems like his. When the center was created (at the University of Illinois), Smarr became its director. With really good computers, scientists needed software to take best advantage of them. Two members of his software team (Marc Andreessen and Eric Bina) created a piece of software in 1993 called MOSAIC, which was an easy-to-use way of searching and communicating with the world wide web.

MOSAIC was the first web browser and the browsers you now use to read my Facebook post are its descendants (and still use many of its features.) It was only when browsers made it easy for the average person to get involved with the Web that the Web took off and the personal computer revolution began its modern acceleration. And to think it wouldn't have happened if an astrophysicist hadn't been itching to know the details of the neighborhood of a black hole or two.

Black Hole at Center of the Milky Way is Found to be Cooking its Dinner

Astronomers working with the European Herschel Space Observatory have discovered really hot gas in the vicinity of the monster black hole at the center of our Galaxy. Over the years, many lines of evidence have shown us that there is a black hole with enough material to make 4 million Suns at the heart of the Milky Way. The new observations, made using infrared (or heat) rays, show that gases such as water vapor and carbon monoxide have been heated to about 1000 degrees Centigrade within a lightyear of the black hole.

While energy from nearby stars may also be heating this inner gas, the astronomers can't account for so much heat from stars alone. They think that great streamers of gas heading toward the black hole may be colliding and the shock waves from the collisions may be significant contributors to the heating. Some of the streamers of gas will someday be "eaten" by the black hole. In other words, like many a hungry diner, the black hole appears to be "cooking" its dinner in anticipation of eating it.

In fact, other observations have recently shown a cloud of gas weighing as much as several Earths, falling to its doom much closer to the black hole. This cloud may be consumed by the black hole as soon as the end of 2013. When such clouds actually spiral inward to their doom, they heat up a lot at the end. The last thing we observe from them before they fall into the black hole (and are no longer visible) is a "burp" of x-rays. Several x-ray telescopes in space are prepared to record such burps when they happen.

If you are cooking a barbecue this Memorial Day Weekend (a holiday in the U.S.), you can enjoy the idea that some serious cooking may also be going on at the center of our Galaxy. The center region is 26,000 lightyears away from us, so none of this poses the least danger to planet Earth and its cooks.

(By the way, to see one of the lines of evidence for the existence of the monster black hole, we recommend a great new movie made from observations by astronomer Andrea Ghez' group at UCLA. The movie shows the whirling orbits of stars very close to the black hole, being pulled around by the enormous gravity of the black hole. Check it out at:

http://www.astro.ucla.edu/~ghezgroup/gc/images/media/ghezGC_comp3-18_H264_864.mov

Note that each second of the movie shows two years of star motion. It's enough to make you dizzy.)

An Amazing Picture of an Active Galaxy by the Hubble and an Amateur Astronomer

This past week, the scientists at the Space Telescope Science Institute released a remarkable picture, which combines Hubble images with those taken by advanced amateur astronomers on Earth, and I'm glad to be able to share it with you.   (Click on the picture to make it bigger.)

In the image, we're seeing the central part of an "active" or disturbed galaxy about 25 million light years away, with the catalog number M106.  You can see the yellow center of the galaxy, crowded with stars whose light blends together.  You can also see its great spiral arms of stars, gently curving away from that center.  They are outlined with blue stars and regions where gas is being heated by stars and glowing red.  Those arms go much further out than the boundaries of this picture.  

But what is especially interesting is that there are also great jets of glowing red gas, which are not part of the flat spiral structure of the galaxy.  Instead, they are at odd angles to the galaxy's disk.  What we are seeing there are great clouds of glowing hydrogen -- the most common element in all galaxies.  But what makes them glow so intensely?  Astronomers have good evidence that they are energized by radiation (not visible to the human eye) coming from a super-giant black hole at the center of the galaxy.  

Neither the black hole (somewhere in the middle of the yellow center) or its rays of energy are visible here.  But when those rays hit the gas that is the "raw material" of such galaxies, they make it glow with a fierce intensity.  

This beautiful photograph was assembled by an amateur astronomer, Robert Gendler, a doctor living on the East Coast, who has made astronomical photography his hobby and his passion.  It's quite a coup to have his photograph used and released by the Hubble scientists.  For more of Dr. Gendler's photos, see his web site at: http://www.robgendlerastropics.com/

If you want to learn some basic information about black holes, you can check out a little video of a 6-minute talk I gave about them at the SETI Institute: http://www.youtube.com/watch?v=7DX_cc-IjpY 

Amateur astrophotographer R. Jay Gabany also contributed to the image.  You can see his image (with less detail) but showing the whole galaxy and really emphasizing the gas excited by the black hole at:
http://apod.nasa.gov/apod/image/1103/lrg_ngc4258gabany.jpg 

Music Inspired by Astronomy

One of my hobbies is collecting examples of music that are seriously influenced by astronomy -- I've found astronomical ideas in both popular songs and classical music. A new catalog of such music (organized by topic) has just been published, and I thought some of you might enjoy seeing the collection of weird and wonderful pieces I have found over the years. (Only pieces available on commercial CD's are included.) The list can be found at: 

http://aer.aas.org/resource/1/aerscz/v11/i1/p010303_s1?view=fulltext

Most of these pieces may not be your cup of tea, but if you are dying to know what six songs include scientifically valid information or ideas about black holes, this is the place you will find an answer.  (Note that this list doesn't including anything about astronauts or space travel, nor does it include any so-called new-age "space music.)   But perhaps you can discover a few pieces that you may enjoy reading about or hearing on your own music player.

Giant Black Hole at the Center of Our Galaxy (and a Video)

A new observatory in space has caught the giant black hole at the center of our home galaxy in the process of having a snack. We know that the at the very heart of the Milky Way there lurks a black hole with as much material inside as 3 - 4 million Suns. When material falls into such a black hole, just before it enters, it gets very hot by friction and gives off (not light but) a glow of x-rays.

Once material falls into a black hole, then no light or x-rays can escape from it. But just before any such stuff goes to its doom, we do see a flare of x-rays from it. It is just this sort of flare that the NuSTAR satellite detected in July (just about a month after it was launched). It wasn't really a full meal for the black hole, merely an afternoon snack, but the temperature of the glowing gas cloud before it fell in was an astounding 180 million degrees Fahrenheit.

The so called "super-massive" black hole at the center of our Galaxy is a relatively small one, compared to some of the really massive black holes in the centers of other galaxies.  Some of these have billions (thousands of millions) of times the mass of our Sun contained within them.

If you are already a black hole fan, such observations will probably just confirm your view of how weird black holes are. But if you are not sure what black holes are, I might recommend a little video that the SETI Institute made of me during a family event there. It's a brief, friendly explanation of just what black holes are and why falling into one is a "once-in-a-lifetime experience." You can see it at:
http://www.youtube.com/watch?v=7DX_cc-IjpY