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Saturn, and then been kicked out to larger distances through gravitational interactions with their neighbors. All these wonderful new observations illustrate how dangerous it can be to draw conclusions about a phenomenon in science (in this case, how planetary systems form and arrange themselves) when you are only wor... |
Centauri, which is spectral type M and located 4.2 light years from us.) We have a special interest in finding planets that could support life like ours, in which case, we need to find exoplanets within their star’s habitable zone, where surface temperatures are consistent with liquid water on the surface. This is pro... |
as high as hundreds of kilometers per second, from a star super-Earth a planet larger than Earth, generally between 1.4 and 2.8 times the size of our planet transit when one astronomical object moves in front of another SUMMARY 21.1 Star Formation Most stars form in giant molecular clouds with masses as large as 3 × 1... |
Jupiter in the solar system. 21.4 Planets beyond the Solar System: Search and Discovery Several observational techniques have successfully detected planets orbiting other stars. These techniques fall into two general categories—direct and indirect detection. The Doppler and transit techniques are our most powerful ind... |
Good review with Hubble results. Ray, T. “Fountains of Youth: Early Days in the Life of a Star.” Scientific American (August 2000): 42. On outflows from young stars. Young, E. “Cloudy with a Chance of Stars.” Scientific American (February 2010): 34. On how clouds of interstellar matter turn into star systems. Young, M... |
-Earth (planets somewhat bigger than ours) using new instruments and techniques that could show us what their atmospheres are made of. Websites Exoplanet Exploration: http://planetquest.jpl.nasa.gov/. PlanetQuest (from the Navigator Program at the Jet Propulsion Lab) is probably the best site for students and beginners... |
aller (2:25). Are We Alone: An Evening Dialogue with the Kepler Mission Leaders: http://www.youtube.com/ watch?v=O7ItAXfl0Lw. A non-technical panel discussion on Kepler results and ideas about planet formation with Bill Borucki, Natalie Batalha, and Gibor Basri (moderated by Andrew Fraknoi) at the University of Califor... |
you recommend, and why? C. Some people consider the discovery of any planets (even hot Jupiters) around other stars one of the most important events in the history of astronomical research. Some astronomers have been surprised that the public is not more excited about the planet discoveries. One reason that has been s... |
from the data that Kepler provided. Your group should access the site, work together to use it, and classify two light curves. Report back to the class on what you have done. H. Yuri Milner, a Russian-American billionaire, recently pledged $100 million to develop the technology to send many miniaturized probes to a st... |
a forming star with the scale of our solar system. 10. Why is it so hard to see planets around other stars and so easy to see them around our own? 11. Why did it take astronomers until 1995 to discover the first exoplanet orbiting another star like the Sun? 12. Which types of planets are most easily detected by Dopple... |
estimate the density of this planet, and then use that information to explain why it must be a gas giant. 23. An exoplanetary system has two known planets. Planet X orbits in 290 days and Planet Y orbits in 145 days. Which planet is closest to its host star? If the star has the same mass as the Sun, what is the semi-m... |
rogen, blue to hydrogen, and blue/violet to oxygen. (credit: modification of work by NASA, ESA and The Hubble Heritage Team (STScI/AURA)) Chapter Outline 22.1 Evolution from the Main Sequence to Red Giants 22.2 Star Clusters 22.3 Checking Out the Theory 22.4 Further Evolution of Stars 22.5 The Evolution of More Massive... |
their lives. Some astronomers like to call the main-sequence phase the star’s “prolonged adolescence” or “adulthood” (continuing our analogy to the stages in a human life). The left-hand edge of the main-sequence band in the H–R diagram is called the zero-age main sequence (see Figure 18.15). We use the term zero-age ... |
increase by a factor of 24, or 16 times. Check Your Learning If the rate of fusion of a star increased 256 times, by what factor would the temperature increase? Answer: The temperature would increase by a factor of 2560.25 (that is, the 4th root of 256), or 4 times. Lifetimes on the Main Sequence How many years a star... |
of their lives to peacefully fusing hydrogen into helium.) Lifetimes of Main-Sequence Stars Spectral Type Surface Temperature (K) Mass (Mass of Sun = 1) Lifetime on Main Sequence (years) 54,000 29,200 40 16 1 million 10 million O5 B0 Table 22.1 770 Chapter 22 Stars from Adolescence to Old Age Lifetimes of Main-Sequenc... |
way, like all heat, flows outward to where it is a bit cooler. In the process, the heat raises the temperature of a layer of hydrogen that spent the whole long main-sequence time just outside the core. Like an understudy waiting in the wings of a hit Broadway show for a chance at fame and glory, this hydrogen was almo... |
top of the frame. When you take the lid off a pot of boiling water, the steam can expand and it cools down. In the same way, the expansion of a star’s outer layers causes the temperature at the surface to decrease. As it cools, the star’s overall color becomes redder. (We saw in Radiation and Spectra that a red color ... |
youth” and “adulthood” to “old age.” (After all, many human beings today also see their outer layers expand a bit as they get older.) By considering the relative ages of the Sun and Betelgeuse, we can also see that the idea that “bigger stars die faster” is indeed true here. Betelgeuse is a mere 10 million years old, w... |
black lines show the predicted evolution from the main sequence through the red giant or supergiant stage on the H–R diagram. Each track is labeled with the mass of the star it is describing. The numbers show how many years each star takes to become a giant after leaving the main sequence. The red line is the zero-age... |
—undergoing pre-main- sequence gravitational contraction. We can see many stages of stellar evolution among the members of a single cluster, and we can see whether our models can explain why the H–R diagrams of clusters of different ages look the way they do. The three basic types of clusters astronomers have discovere... |
hydrogen fuel and have expanded to about 100 times the diameter of our Sun. The blue stars have started helium fusion. (credit a: modification of work by NASA, ESA and the Hubble Heritage Team (STScI/AURA); credit b: modification of work by NASA, ESA, and the Hubble SM4 ERO Team) What would it be like to live inside a... |
the Sun. Note the contrast in color between the bright yellow supergiant and the hot blue main-sequence stars. The name comes from John Herschel’s nineteenth-century description of it as “a casket of variously colored precious stones.” (credit: ESO/Y. Beletsky) Although the individual stars in an open cluster can surv... |
only about a million years, they would not still be around unless star 1 Escape velocity is the speed needed to overcome the gravity of some object or group of objects. The rockets we send up from Earth, for example, must travel faster than the escape velocity of our planet to be able to get to other worlds. 778 Chapt... |
22.8. Young Cluster H–R Diagram. We see an H–R diagram for a hypothetical young cluster with an age of 3 million years. Note that the high-mass (high-luminosity) stars have already arrived at the main-sequence stage of their lives, while the lower-mass (lower-luminosity) stars are still contracting toward the zero-age... |
dust are gone. One massive star has evolved to become a red giant and stands out as an especially bright orange member of the cluster. This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 22 Stars from Adolescence to Old Age 781 Figure 22.11. NGC 3293. All the stars in an open star c... |
, the lower the point on the main sequence (and the lower the mass of the stars) where stars begin to move toward the red giant region. The location in the H–R diagram where the stars have begun to leave the main sequence is called the main- sequence turnoff. This OpenStax book is available for free at http://cnx.org/c... |
off the main sequence to become red giants) as a measure of the age of a cluster (the main-sequence turnoff we discussed previously). For example, we can compare the luminosities of the brightest stars that are still on the main sequence in Figure 22.10 and Figure 22.13. Using this method, some associations and open c... |
applies to almost all stars: each starts as a contracting protostar, then lives most of its life as a stable main-sequence star, and eventually moves off the main sequence toward the red-giant region. As we have seen, the pace at which each star goes through these stages depends on its mass, with more massive stars ev... |
the nucleus of the helium atom an alpha particle. When the triple-alpha process begins in low-mass (about 0.8 to 2.0 solar masses) stars, calculations show that the entire core is ignited in a quick burst of fusion called a helium flash. (More massive stars also ignite helium but more gradually and not with a flash.) ... |
Stars from Adolescence to Old Age 787 Becoming a Giant Again After the helium flash, the star, having survived the “energy crisis” that followed the end of the main-sequence stage and the exhaustion of the hydrogen fuel at its center, finds its balance again. As the star readjusts to the release of energy from the tri... |
. We can think of stellar evolution as a story of a constant struggle against gravitational collapse. A star can avoid collapsing as long as it can tap energy sources, but once any particular fuel is used up, it starts to collapse again. The star’s situation is analogous to the end of the main-sequence stage (when the ... |
such a star. In a star with a mass similar to that of the Sun, the formation of a carbon-oxygen core thus marks the end of the generation of nuclear energy at the center of the star. The star must now confront the fact that its death is near. We will discuss how stars like this end their lives in The Death of Stars, b... |
to shrink again and to heat up as it gets more and more compressed. (Remember that this compression will not be halted by another type of fusion in these low-mass stars.) The whole star follows along, shrinking and also becoming very hot—reaching surface temperatures as high as 100,000 K. Such hot stars are very stron... |
the red region isolates emission from ionized nitrogen, which is radiated by the coolest gas farthest from the star; and the green region represents oxygen emission, which is produced at intermediate temperatures and is at an intermediate distance from the star. (b) This planetary nebula, M2-9, is an example of a butt... |
by NASA, The Hubble Heritage Team (STScI/AURA); credit d: modification of work by H. Bond (STScI) and NASA) As Figure 22.18 shows, sometimes a planetary nebula appears to be a simple ring. Others have faint shells surrounding the bright ring, which is evidence that there were multiple episodes of mass loss when the st... |
/ESA; credit “Helix”: modification of work by NASA, ESA, C.R. O’Dell (Vanderbilt University), and M. Meixner, P. McCullough) As the star continues to lose mass, any less dense gas that leaves the star cannot penetrate the torus, but the gas can flow outward in directions perpendicular to the disk. If we look perpendicu... |
ged up and mixed with its outer layers, which can cause further nuclear reactions and the creation of still more new elements. As a result, the winds that blow outward from such stars include atoms that were “newly minted” inside the stars’ cores. (As we will see, this mechanism is even more effective for high-mass sta... |
will reach Earth. For a while, the amount of carbon dioxide will continue to decrease. (Note that this effect counteracts increases in carbon dioxide from human activities, but on a much-too-slow timescale to undo the changes in climate that are likely to occur in the next 100 years.) Eventually, the heating of Earth ... |
think of would be to move humanity to a more distant and cooler planet. However, calculations indicate that there are long periods of time (several hundred million years) when no planet is habitable. For example, Earth becomes far too warm for life long before Mars warms up enough. A better alternative may be to move ... |
in our best models of the first few minutes of the universe, everything starts with the two simplest elements—hydrogen and helium (plus a tiny bit of lithium). All the predictions of the models imply that no heavier elements were produced at the beginning of the universe. Yet when we look around us on Earth, we see lo... |
its evolution. The pink outer region is material ejected in an outburst seen in 1843, the largest of such mass loss event that any star is known to have survived. Moving away from the star at a speed of about 1000 km/s, the material is rich in nitrogen and other elements formed in the interior of the star. The inner b... |
atomic nuclei) in the centers of the more massive red giant stars. This still leaves the question of where elements heavier than iron come from. We will see in the next chapter that when massive stars finally exhaust their nuclear fuel, they most often die in a spectacular explosion—a supernova. Heavier elements can b... |
be less and less as we look further into the past. We saw that the globular clusters are much older than the open clusters. Since globular-cluster stars formed much earlier (that is, they are an earlier generation of stars) than those in open clusters, they have only a relatively small abundance of elements heavier th... |
stars) that form a system of clusters in the center of our Galaxy helium flash a nearly explosive ignition of helium in the triple-alpha process in the dense core of a red giant star main-sequence turnoff location in the H–R diagram where stars begin to leave the main sequence nucleosynthesis the building up of heavy ... |
Open clusters typically contain hundreds of stars, are located in the plane of the Galaxy, and have diameters less than 30 light-years. Associations are found in regions of gas and dust and contain extremely young stars. This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 22 Stars f... |
where it can be used to form new stars. Each succeeding generation of stars therefore contains a larger proportion of elements heavier than hydrogen and helium. This progressive enrichment explains why the stars in open clusters (which formed more recently) contain more heavy elements than do those in ancient globular... |
are born in clusters, but different clusters evolve differently. Subinsky, R. “All About 47 Tucanae.” Astronomy (September 2014): 66. What we know about this globular cluster and how to see it. Websites BBC Page on Giant Stars: http://www.bbc.co.uk/science/space/universe/sights/giant_stars. Includes basic information ... |
youtube.com/watch?v=1D2cwiZld0o. Brief Hubblecast episode with Joe Liske, explaining planetary nebulae in general and one example in particular (5:22). This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 22 Stars from Adolescence to Old Age 801 COLLABORATIVE GROUP ACTIVITIES A. Have ... |
astronomy class suddenly hears about this problem from a large donor and appoints your group as a task force to make suggestions on how to prepare for the end of Earth. Make a list of arguments for why such a task force is not really necessary. F. Use star charts to identify at least one open cluster visible at this t... |
becomes a red giant to the time it exhausts the last type of fuel its core is capable of fusing. 6. A star is often described as “moving” on an H–R diagram; why is this description used and what is actually happening with the star? 7. On which edge of the main sequence band on an H–R diagram would the zero-age main se... |
globular clusters, or associations? This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 22 Stars from Adolescence to Old Age 803 19. Explain how an H–R diagram of the stars in a cluster can be used to determine the age of the cluster. 20. Where did the carbon atoms in the trunk of a... |
universe? Would you expect to find a globular cluster with a main-sequence turnoff for stars of 0.8 solar mass or less? Why or why not? 32. Automobiles are often used as an analogy to help people better understand how more massive stars have much shorter main-sequence lifetimes compared to less massive stars. Can you ... |
.3 to estimate the mass of this star. Then calculate the age of the cluster. This method is similar to the procedure used by astronomers to obtain the ages of clusters, except that they use actual data and model calculations rather than simply making estimates from a drawing. How do your ages compare with the ages in t... |
Evolution of Binary Star Systems 23.6 The Mystery of the Gamma-Ray Bursts Thinking Ahead Do stars die with a bang or a whimper? In the preceding two chapters, we followed the life story of stars, from the process of birth to the brink of death. Now we are ready to explore the ways that stars end their lives. Sooner or... |
giant region of the H–R diagram for a second time and had shed some of its outer layers to form a planetary nebula. Recall that during this time, the core of the star was undergoing an “energy crisis.” Earlier in its life, during a brief stable period, helium in the core had gotten hot enough to fuse into carbon (and o... |
807 moving rapidly. This means that no two of them will be in the same place moving in exactly the same way at the same time. But this all changes when a star exhausts its store of nuclear energy and begins its final collapse. As the star’s core contracts, electrons are squeezed closer and closer together. Eventually,... |
yan Chandrasekhar. He was able to show how much a star will shrink before the degenerate electrons halt its further contraction and hence what its final diameter will be (Figure 23.2). When Chandrasekhar made his calculation about white dwarfs, he found something very surprising: the radius of a white dwarf shrinks as ... |
had read about in India. His calculations soon brought him into conflict with certain distinguished astronomers, including Sir Arthur Eddington, who publicly ridiculed Chandra’s ideas. At a number of meetings of astronomers, such leaders in the field as Henry Norris Russell refused to give Chandra the opportunity to d... |
other “stellar corpses” in the M4 star cluster, located about 7200 light-years away. The Ultimate Fate of White Dwarfs If the birth of a main-sequence star is defined by the onset of fusion reactions, then we must consider the end of all fusion reactions to be the time of a star’s death. As the core is stabilized by d... |
. Visible Light and X-Ray Images of the Sirius Star System. (a) This image taken by the Hubble Space Telescope shows Sirius A (the large bright star), and its companion star, the white dwarf known as Sirius B (the tiny, faint star at the lower left). Sirius A and B are 8.6 light-years from Earth and are our fifth-close... |
search for young clusters that contain one or more white dwarf stars. Remember that more massive stars go through all stages of their evolution more rapidly than less massive ones. Suppose we find a cluster that has a white dwarf member and also contains stars on the main sequence that have 6 times the mass of the Sun... |
it reaches a new temperature high enough to fuse still-heavier nuclei. The products of carbon fusion can be further converted into silicon, sulfur, calcium, and argon. And these elements, when heated to a still-higher temperature, can combine to produce iron. Massive stars go through these stages very, very quickly. I... |
that goal. But iron is a mature nucleus with good self-esteem, perfectly content being iron; it requires payment (must absorb energy) to change its stable nuclear structure. This is the exact opposite of what has happened in each nuclear reaction so far: instead of providing energy to balance the inward pull of gravit... |
s overlying layers. The core begins to shrink rapidly. More and more electrons are now pushed into the atomic nuclei, which ultimately become so saturated with neutrons that they cannot hold onto them. At this point, the neutrons are squeezed out of the nuclei and can exert a new force. As is true for electrons, it tur... |
cubic centimeter’s worth) of a neutron star. The neutron degenerate core strongly resists further compression, abruptly halting the collapse. The shock of the sudden jolt initiates a shock wave that starts to propagate outward. However, this shock alone is not enough to create a star explosion. The energy produced by ... |
http://cnx.org/content/col11992/1.8 Chapter 23 The Death of Stars 815 Figure 23.7. Five Supernova Explosions in Other Galaxies. The arrows in the top row of images point to the supernovae. The bottom row shows the host galaxies before or after the stars exploded. Each of these supernovae exploded between 3.5 and 10 bi... |
, neither the authors nor the readers of this book would exist. But the supernova explosion has one more creative contribution to make, one we alluded to in Stars from Adolescence to Old Age when we asked where the atoms in your jewelry came from. The supernova explosion produces a flood of energetic neutrons that barr... |
drive the evolution of life on our planet. In all the ways we have mentioned, supernovae have played a part in the development of new generations of stars, planets, and life. This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 23 The Death of Stars 817 But supernovae also have a dar... |
force of gravity, F, between two bodies is calculated as F = GM1 M2 R2 where G is the gravitational constant, 6.67 × 10–11 Nm2/kg2, M1 and M2 are the masses of the two bodies, and R is their separation. Also, from Newton’s second law, where a is the acceleration of a body with mass M. F = M × a So let’s consider the s... |
kg ⎝3.2 × 106⎞ ⎛ ⎠ 2 ⎞ ⎠ = 2.61 × 107 m/s2 23.3 SUPERNOVA OBSERVATIONS Learning Objectives By the end of this section, you will be able to: Describe the observed features of SN 1987A both before and after the supernova Explain how observations of various parts of the SN 1987A event helped confirm theories about supern... |
Stephenson have scoured records from around the world to find more than 20 reports of the 1006 supernova ( SN 1006) (Figure 23.9). This has allowed them to determine with some accuracy where in the sky the explosion occurred. They place it in the modern constellation of Lupus; at roughly the position they have determi... |
many with an interest in the heavens, including Galileo. No supernova has been spotted in our Galaxy for the past 300 years. Since the explosion of a visible supernova is a chance event, there is no way to say when the next one might occur. Around the world, dozens of professional and amateur astronomers keep a sharp ... |
5 million light-years from Earth, this is the closest supernova of type Ia discovered in the past few decades. In the image, you can see reddish plumes of hydrogen coming from the central region of the galaxy, where a considerable number of young stars are being born. (credit: modification of work by NASA, ESA, A. Goob... |
mass of about 20 MSun. For 90% of its life, it lived quietly on the main sequence, converting hydrogen into helium. At this time, its luminosity was about 60,000 times that of the Sun (LSun), and its spectral type was O. When the hydrogen in the center of the star was exhausted, the core contracted and ultimately beca... |
contracted again, the radius of the surface also decreased, and the star became a blue supergiant with a luminosity still about equal to 100,000 LSun. This is what it still looked like on the outside when, after brief periods of further fusion, it reached the iron crisis we discussed earlier and exploded. Some key sta... |
. Neutrinos poured out of the core, helping the shock wave blow the star apart. The shock reached the surface of the star a few hours later, and the star began to brighten into the supernova Ian Shelton observed in 1987. The Synthesis of Heavy Elements The variations in the brightness of SN 1987A in the days and months... |
Figure 23.13, astronomers did observe brightening due to radioactive nuclei in the first few months following the supernova’s outburst and then saw the extra light die away as more and more of the radioactive nuclei decayed to stable iron. The gamma-ray heating was responsible for virtually all of the radiation detect... |
inos had already passed through Earth and were on their way back out into space when they were captured. Only a few neutrinos were detected because the probability that they will interact with ordinary matter is very, very low. It is estimated that the supernova actually released 1058 neutrinos. A tiny fraction of thes... |
stars and white dwarfs.) Because it is so small, a neutron star probably strikes you as the object least likely to be observed from thousands of light-years away. Yet neutron stars do manage to signal their presence across vast gulfs of space. Properties of a Typical White Dwarf and a Neutron Star Property White Dwarf... |
of gas produced by SN 1054, a supernova that was recorded by the Chinese in 1054 (Figure 23.14). The energy from the Crab Nebula pulsar arrives in sharp bursts that occur 30 times each second—with a regularity that would be the envy of a Swiss watchmaker. In addition to pulses of radio energy, we can observe pulses of... |
a neutron star sweeps across the oceans of space, giving us a pulse of radiation each time the beam points toward Earth. Figure 23.15. Lighthouse. A lighthouse in California warns ships on the ocean not to approach too close to the dangerous shoreline. The lighted section at the top rotates so that its beam can cover ... |
magnetic north and south poles do not have to be anywhere close to the north and south poles defined by the star’s rotation. In the same way, we discussed in the chapter on The Giant Planets that the magnetic poles on the planets Uranus and Neptune are not lined up with the poles of the planet’s spin. Figure 23.16 sho... |
The Death of Stars speeds. As its rotational energy is used to excite the Crab Nebula year after year, the pulsar inside the nebula slows down. As it slows, the pulses come a little less often; more time elapses before the slower neutron star brings its beam back around. Several decades of careful observations have no... |
in space will not include Earth than will include it. Thus, we estimate that we are unable to observe a large number of neutron stars because their pulsar beams miss us entirely. At the same time, it turns out that only a few of the pulsars discovered so far are embedded in the visible clouds of gas that mark the remn... |
and gamma-ray radiation from a neutron star known as SGR 1806-20. What made this event so remarkable was that, despite the distance of the source, its tidal wave of radiation had measurable effects on Earth’s atmosphere. The apparent brightness of this gamma-ray flare was greater than any historical star explosion. Th... |
Ia supernovae event Indicate how type Ia supernovae differ from type II supernovae The discussion of the life stories of stars presented so far has suffered from a bias—what we might call “single- star chauvinism.” Because the human race developed around a star that goes through life alone, we tend to think of most st... |
, which are actually the endpoint of stellar evolution for low-mass stars. But since the system of two stars was too faint to be visible to the naked eye, it did seem to people, before telescopes were invented, that a star had appeared where nothing had been visible. This OpenStax book is available for free at http://c... |
a huge amount of energy in a very short time. However, unlike the explosion of a high-mass star, which can leave behind a neutron star or black hole remnant, the white dwarf is completely destroyed in the process, leaving behind no remnant. We call these white dwarf explosions type Ia supernovae. We distinguish type I... |
would slowly move closer together until they merge. If their combined mass is greater than the Chandrasekhar limit, the result could also be a type Ia supernova explosion You can watch a short video (https://openstaxcollege.org/l/30supernovavid) about Supernova SN 2014J, a type Ia supernova discovered in the Messier 8... |
at http://cnx.org/content/col11992/1.8 Chapter 23 The Death of Stars 835 observatories above Earth’s atmosphere (see Astronomical Instruments) have recorded many objects that undergo just these types of X-ray bursts. If the neutron star and its companion are positioned the right way, a significant amount of material c... |
. But there are stars whose core masses are greater than 3 MSun when they exhaust their fuel supplies. What becomes of them? The truly bizarre result of the death of such massive stellar cores (called a black hole) is the subject of our next chapter. But first, we will look at an astronomical mystery that turned out to... |
the bursts to come from was the main disk of our own (pancake-shaped) Galaxy. If this had been the case, however, more bursts would have been seen in the crowded plane of the Milky Way than above or below it. Instead, the sources of the bursts were distributed isotropically; that is, they could appear anywhere in the ... |
cold outer reaches of our own solar system or from the halo of our Galaxy, then astronomers had to hypothesize some new kind of physical process that could produce unpredictable flashes of high-energy gamma rays in these otherwise-quiet regions of space. And if the bursts came from galaxies millions or billions of lig... |
identified the position of the burst, and reoriented the spacecraft to focus BeppoSAX’s X- ray detector on the source. To their excitement, they detected a slowly fading X-ray source 8 hours after the event—the first successful detection of an afterglow from a gamma-ray burst. This provided an even-better 838 Chapter ... |
fuzzy object that was 4 billion light- years from the Sun, meaning that the location of the burst had to be at least this far away—and possibly even farther. (How astronomers can get the distance of such an object from the Doppler shift in the spectrum is something we will discuss in Galaxies.) What that spectrum show... |
per la Ricerca dei Transienti Ottici Rapidi (Italian for Telescope Optimized for the Research of Rapid Optical Transients)] (see Figure 23.21). According to the data taken by these telescopes, for a period of about 30 seconds, the light from the gamma-ray burst was bright enough that it could have been seen by the una... |
out in only one or two narrow beams, then our estimates of the luminosity of the source can be reduced, and the bursts may be easier to explain. In that case, however, the beam has to point toward Earth for us to be able to see the burst. This, in turn, would imply that for every burst we see from Earth, there are pro... |
http://cnx.org/content/col11992/1.8 Chapter 23 The Death of Stars 841 in each stage of its life. This suggests that the bursts come from a young and short-lived, and therefore massive type of star. Furthermore, in several cases when a burst has occurred in a galaxy relatively close to Earth (within a few billion light... |
emission from these events lasts less than 2 seconds, and in some cases may last only milliseconds—an amazingly short time. Such a timescale is difficult to achieve if they are produced in the same way as long-duration gamma-ray bursts, since the collapse of the stellar interior onto the black hole should take at leas... |
, massive stars in its spectrum. Furthermore, no supernova was ever detected after the burst, despite extensive searching. What could produce a burst less than a second long, originating from a region with no star formation? The leading model involves the merger of two compact stellar corpses: two neutron stars, or per... |
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