| [00:00:00.17] | |
| [00:00:04.23] | |
| [00:00:08.26] | |
| [00:00:12.28] | Lynn Chandler: Okay. Good morning |
| [00:00:16.37] | and welcome to the NASA press conference on the latest scientific |
| [00:00:20.49] | discoveries from the Suzaku mission. I am Lynn Chandler and I am the |
| [00:00:24.58] | press officer for the Suzaku mission and today we have with us |
| [00:00:28.65] | Dr. Kim Weaver, Astrophysicist |
| [00:00:32.76] | and Dr. Koji Mukai, |
| [00:00:36.81] | Suzaku Guest Observer Facility Lead. |
| [00:00:40.93] | And at this time |
| [00:00:44.96] | time I would like to turn it over to our scientists for their presentations. |
| [00:00:49.07] | Dr. Kim Weaver: Thanks Lynn. We're discussing a new result from the Suzaku |
| [00:00:53.20] | X-ray satellite. For the first time, individual |
| [00:00:57.29] | clouds of gas have been caught in the act orbiting a giant black hole |
| [00:01:01.34] | at the center of a galaxy, this galaxy is named NGC 1365. |
| [00:01:05.35] | The movements and shapes of such clouds have long |
| [00:01:09.45] | been a mystery to astronomers. Remarkably these clouds have |
| [00:01:13.52] | a shape similar to the comets that we see in our solar system. |
| [00:01:17.55] | These clouds can also tell us a great deal about the extreme environments near |
| [00:01:21.65] | black holes. The science technique used to study these clouds |
| [00:01:25.97] | is called occultation or the blocking of x-ray light by the |
| [00:01:30.04] | clouds themselves. An occultation is when an apparently larger body |
| [00:01:34.07] | passes in front of a apparently smaller one. This happens for example |
| [00:01:38.22] | when we see the moon pass in front of a star as it orbits the |
| [00:01:42.32] | Earth. With Suzaku we have an occultation of a black hole |
| [00:01:46.37] | by orbiting clouds of gas. This is only the second |
| [00:01:50.39] | time an occultation in x-rays has been tracked so closely as to |
| [00:01:54.48] | capture movements so near to a black hole but it's the first time |
| [00:01:58.54] | such unique dimming of x-ray light has been seen that contains enough |
| [00:02:02.57] | information to actually determine the shapes of the clouds themselves that make up |
| [00:02:06.68] | the x-ray curtain in a galaxy. Koji will now tell us about |
| [00:02:10.83] | Suzaku and its importance for this science, Koji. Dr. Koji Mukai: Thanks Kim. |
| [00:02:14.88] | Suzaku is an x-ray astronomy satellite built by a |
| [00:02:18.89] | collaboration between Japan and the U.S. and launched in July of 2005. |
| [00:02:22.93] | You may not have heard of Suzaku before. |
| [00:02:27.03] | If you heard about one x-ray astronomy mission, it's likely to be Chandra, |
| [00:02:31.12] | which is justifiably famous for the exquisite x-ray images |
| [00:02:35.17] | that it can capture, but there are other x-ray astronomy satellites |
| [00:02:39.18] | satellites in orbit today. So why do we need more than one x-ray |
| [00:02:43.27] | astronomy satellite? This is because it takes a lot of resources |
| [00:02:47.38] | to build one satellite that can do everything that |
| [00:02:51.43] | an x-ray astronomer would ever want to do. It makes sense |
| [00:02:55.58] | for each project to focus on different aspects of |
| [00:02:59.68] | x-ray astronomy and build a satellite that can do that |
| [00:03:03.73] | aspect very well. In the case of Chandra it was the |
| [00:03:07.76] | fine imaging ability, in the case of Suzaku, |
| [00:03:11.86] | the team decided to focus on spectroscopy. |
| [00:03:15.94] | Spectroscopy is the study of intensity of electromagnetic |
| [00:03:19.97] | radiation, visible light, x-rays and so on, as a function |
| [00:03:24.11] | of its wavelength or the energies of individual x-ray photons. |
| [00:03:28.23] | One particular way that Suzaku excels is |
| [00:03:32.30] | that it covers a wide range of x-ray energies. Suzaku |
| [00:03:36.31] | has one type of instrument that can detect x-rays |
| [00:03:40.39] | of the same energies that Chandra can study, but |
| [00:03:44.45] | Suzaku carries another instrument which studies higher energy x-rays. |
| [00:03:48.48] | So it's like seeing all the colors of the rainbow |
| [00:03:52.57] | with Suzaku instead of just seeing oranges and reds. |
| [00:03:56.64] | It also happens that higher-energy x-rays |
| [00:04:00.67] | --bluer photons, so to speak--penetrate deeper |
| [00:04:04.69] | into gas clouds and lower energy x-rays |
| [00:04:08.74] | tend to get more absorbed. You can say that |
| [00:04:12.79] | Suzaku and the supermassive black hole to x-ray |
| [00:04:16.82] | the gas cloud orbiting around the NGC 1365, much like |
| [00:04:20.93] | doctors do with your bones, which is actually quite rare |
| [00:04:24.95] | in x-ray astronomy. This needed the |
| [00:04:28.98] | Suzaku's ability to study x-rays, |
| [00:04:31.93] | wide range of x-ray energies. |
| [00:04:36.04] | Another reason why Suzaku was essential for this study, was that, |
| [00:04:40.12] | we tend to stare at one object for a long time to |
| [00:04:44.17] | build up the x-ray spectra because you need to |
| [00:04:48.28] | collect enough photons at each energy to have a good spectrum. |
| [00:04:52.39] | With short observations we would have missed |
| [00:04:56.46] | some of the important moments of this occultation event, |
| [00:05:00.48] | so that was another reason why Suzaku was |
| [00:05:04.59] | important. I hope I've made it clear why Suzaku was |
| [00:05:08.67] | a great tool for this research. I will now turn it back to Kim |
| [00:05:12.71] | who will explain the significance of this scientific discovery. Dr. Kim Weaver: Thanks Koji. |
| [00:05:16.72] | The black hole we are talking about is about two million times the mass |
| [00:05:20.82] | of our sun. As material comes close to the black hole it heats |
| [00:05:24.87] | up to about millions of degrees and gives off x-rays. |
| [00:05:28.89] | Obscuration of x-rays by dense gas is seen in many galaxies |
| [00:05:32.99] | but actual occultation by clouds themselves are rarely caught. |
| [00:05:37.06] | One reason is that a galaxy must be observed for a long time, |
| [00:05:41.10] | uninterrupted. It can be very hard to schedule such a long block of |
| [00:05:45.22] | time on our telescopes but it does happen. This particular observation |
| [00:05:49.31] | was three and a half days long, quite long. The graphic |
| [00:05:53.36] | currently being shown, shows the intensity of x-ray |
| [00:05:57.56] | light with time that was measured from this galaxy, and you |
| [00:06:01.62] | can see a lot of variability in the x-ray light. Suzaku |
| [00:06:05.67] | saw two distinct eclipsing events marked by the green lines. |
| [00:06:09.70] | As you can see for each eclipse there is a sudden dimming in x-rays |
| [00:06:13.79] | due to the transit of a dense cloud covering about sixty five percent of the x-ray |
| [00:06:17.86] | source. The specific variability of x-ray light |
| [00:06:21.94] | in NGC 1365 was fairly easy to find due to the |
| [00:06:25.96] | way in which the galaxy is actually tilted with respect to how we see it. |
| [00:06:30.14] | The tilt, this pretty high tilt, gives us a high chance of seeing through many clouds. |
| [00:06:34.26] | Other galaxies could be tilted differently so it could be very hard |
| [00:06:38.31] | to catch views of their clouds. It's possible that the events like |
| [00:06:42.43] | this are simply very rare for astronomers to witness. |
| [00:06:46.51] | The next graphic shows side-by-side pictures of an artist concept of the |
| [00:06:50.58] | comet-like cloud passing in front of the black hole. A fast |
| [00:06:54.61] | fade out of light, like we saw in the light curve before, means that the dense |
| [00:06:58.70] | cold cloud has to have a sharp leading edge as we see here. |
| [00:07:02.75] | On the left hand side you can see the dense cloud blocking the black |
| [00:07:06.79] | hole itself. Slower dimming of the x-ray light over longer |
| [00:07:10.88] | time indicates less dense gas streaming out behind the dense |
| [00:07:14.95] | cloud like the tail of a comet, and you can see on the right hand side of the graphic |
| [00:07:18.98] | now the comet part of the cloud is passing in front of it. |
| [00:07:23.13] | The cloud geometry can be roughly sketched out. Scientists can |
| [00:07:27.19] | only reconstruct the shape of the tail projected on to the plane of the |
| [00:07:31.26] | sky; they can't actually determine the shape of the cloud along |
| [00:07:35.29] | our direction. The next graphic shows the comet |
| [00:07:39.40] | cloud in relation to our solar system, in relation to the sun-Earth |
| [00:07:43.42] | distance. The length of the cloud's tail covers a distance |
| [00:07:47.45] | at about the same as that between the earth and the sun and as you can see here in this |
| [00:07:51.44] | artist's concept. As these clouds orbit the black hole they |
| [00:07:55.50] | constantly loose mass and the expected lifetime |
| [00:07:59.54] | of an individual cloud is only two months. Where |
| [00:08:03.56] | does the gas go that is lost? It's probably not accreted |
| [00:08:07.65] | or eaten by the black hole. It either heats up to ten million degrees |
| [00:08:11.71] | and becomes part of a hot haze of gas that the clouds have to pass |
| [00:08:15.73] | through, or the gas loss is caused by radiation pressure for the black hole |
| [00:08:19.83] | and the gas becomes part of an out-flowing wind. About a |
| [00:08:23.90] | tenth of a solar mass per year, which is many clouds' worth, could be lost |
| [00:08:27.94] | this way. What are the clouds? This is unclear. |
| [00:08:32.05] | Atmospheres of stars can produce mass loss that resembles tails |
| [00:08:36.14] | but there are not nearly enough stars here to account for the number of clouds that are |
| [00:08:40.19] | seen. The dense clouds are probably moving supersonically |
| [00:08:44.21] | through a less dense haze. This would set up a system of shocks, like |
| [00:08:48.30] | bow shocks. As the dense clouds plow through the regions of hot gas, |
| [00:08:52.36] | the clouds erode, and the erosion creates the tails. |
| [00:08:56.40] | Is a comet shape common for such clouds? Well that's not known. |
| [00:09:00.52] | We need more observations of occulting events like this to understand these |
| [00:09:04.60] | and other questions. Lynn Chandler: Thank you Kim and Koji. |
| [00:09:08.69] | And that concludes our presentation portion of the press briefing today, |
| [00:09:12.75] | and at this time we're going to take questions. We do have some callers |
| [00:09:16.77] | on the phone and I ask that you specify which scientist you would like to |
| [00:09:20.87] | answer your question. And our first caller is from Jeffrey |
| [00:09:24.94] | a student in California. Jeffrey: This is for doctor Mukai. |
| [00:09:28.97] | What information does the Suzaku mission seek to discover? And what are the most |
| [00:09:33.08] | important purposes of this probe? Dr. Koji Mukai: Well one |
| [00:09:37.17] | answer to this question is that Suzaku is a facility for the entire |
| [00:09:41.21] | astronomical community. So the community decide what questions to |
| [00:09:45.32] | to tackle and what objects to observe and so on. But |
| [00:09:49.42] | we did have some overarching goals for the mission, when we built the |
| [00:09:53.48] | mission. One is we'd like to study how |
| [00:09:57.51] | various chemical elements are formed in the universe, and how they're dispersed. |
| [00:10:01.61] | Another focus area is the study of matter and the |
| [00:10:05.68] | extreme conditions such as these clouds right near a black hole. |
| [00:10:09.72] | Lynn Chandler: Okay. And our second caller, Lauren |
| [00:10:13.74] | is a student from Texas. Lauren: This is for Dr. Weaver. How large |
| [00:10:17.83] | is a supersize black hole? What would a normal size black hole be like? |
| [00:10:21.86] | Dr. Kim Weaver: A normal black hole we be the most common type that we see |
| [00:10:25.97] | which are stellar mass black holes. A black hole that has the |
| [00:10:30.05] | mass of about the mass of our sun would be about three miles across, so |
| [00:10:34.10] | it would be very small, very tiny. A supersize |
| [00:10:38.12] | black hole can be much, much larger and range from with sizes |
| [00:10:42.21] | anywhere from a tenth of a distance between the earth and the sun to as |
| [00:10:46.27] | large as our entire solar system put together. |
| [00:10:49.95] | Lynn Chandler: Okay. And our next question comes from Bailey in Michigan. |
| [00:10:54.02] | Bailey: This is for Dr. Weaver. Approximately how big is the black holes |
| [00:10:58.07] | diameter, and are there black holes bigger than this one? |
| [00:11:02.09] | Dr. Kim Weaver: Yes. There are black holes bigger than this one. There are many |
| [00:11:06.18] | in fact, you can a have black holes with masses that are up to a billion |
| [00:11:10.23] | times the mass of the sun, so one hundred times more |
| [00:11:14.25] | massive than this black hole. And a black hole like that would be about |
| [00:11:18.34] | one hundred times larger, and again that would be roughly the size of our |
| [00:11:22.40] | solar system. Lynn Chandler: Okay. And our next question comes |
| [00:11:26.36] | from Brittney in New York. Brittney: For Dr. Mukai. |
| [00:11:30.41] | Why is Suzaku called the red bird of the south? |
| [00:11:33.36] | Dr. Koji Mukai: That's a very interesting question. The first x-ray |
| [00:11:37.47] | astronomy satellite launched by our Japanese colleagues was called Hakucho, |
| [00:11:41.53] | which is the Japanese name for the constellation Cygnus or swan. |
| [00:11:45.57] | So that started the tradition of naming the x-ray astronomy satellites |
| [00:11:49.68] | after flying creatures. The fourth one was called ASCA, |
| [00:11:53.76] | which was an acronym but also meant a flying bird |
| [00:11:57.81] | and it also was the name of an ancient |
| [00:12:01.82] | Japanese era. So for |
| [00:12:05.92] | their fifth x-ray astronomy satellite they picked Suzaku, which |
| [00:12:09.99] | not only means "the red bird of the south", but it's also a name |
| [00:12:14.02] | of another era in Japanese history. Lynn Chandler: Okay. And our next |
| [00:12:18.13] | question come from Madeline, a student from Louisiana. |
| [00:12:22.21] | Madeline: This is for Dr. Weaver. In what ways are clouds detected around the black |
| [00:12:26.26] | hole comparable to those observed in our own solar system? |
| [00:12:30.28] | Dr. Kim Weaver: Well clouds in our solar system are like the clouds that we see in our-- |
| [00:12:34.38] | Earth's--atmosphere. So the way in which their similar; when you look up |
| [00:12:38.44] | in the sky and it's a cloudy day, the clouds are blocking the sun's light |
| [00:12:42.47] | from us to see, these clouds are similar in that they are blocking |
| [00:12:46.57] | the x-ray light in the galaxy. Lynn Chandler: And our last question today |
| [00:12:50.69] | comes from Andrew in Virginia. Andrew: This one is for Dr. Weaver. |
| [00:12:54.77] | What's the importance of this finding for astronomy? |
| [00:12:58.82] | Dr. Kim Weaver: Well Koji mentioned one importance and that's understanding the extreme environments |
| [00:13:02.87] | around black holes, but another thing that's really interesting about this is that |
| [00:13:06.88] | black holes generally are thought of as gobbling up material that comes |
| [00:13:10.96] | near them, and eating stuff that flies by, |
| [00:13:15.03] | never to be seen again. But in this case we're actually understanding material |
| [00:13:19.06] | that's going to be going away from the black hole, being pushed away from the |
| [00:13:23.17] | black hole in an out-flowing wind. So we're using this |
| [00:13:27.24] | experiment to understand things that move away |
| [00:13:31.28] | from the black hole and thus are a part of the entire system of |
| [00:13:35.39] | the black hole galaxy environment. |
| [00:13:39.41] | Lynn Chandler: Okay. Thank you for joining us today and this concludes |
| [00:13:43.50] | our NASA press briefing on the Suzaku mission. |
| [00:13:47.55] | |
| [00:13:51.57] |