ASTRONOMY:
Chapter 13 The Death of Stars: NOTES
I
Low-mass stars and planetary nebula
Some
stars come to their end with a whimper and some end with a bang and it all depends on their mass.
In this chapter (and the next) we will learn how stars come to their end.
A) (13-1) Low-mass stars become supergiants before expanding into planetary nebula
Quick review: stars of less than 0.4 M– , called red dwarfs, fuse all of their H into He and die, or cool down over the next several millions of years. Low mass stars, from 0.4 M– to 8.0 M– go through stages wherein H fuses in a region around the core, the star becomes a giant (Changing position on the H-R diagram), lose mass and begin He fusion. If less than 2 M– they have the HE flash, if over 2 M– the transition to He fusion is smoother (no degenerate electrons). Both types of stars lose mass and move into the horizontal branch. Eventually their cores become carbon (triple alpha process) and oxygen. What happens next is the subject of this chapter and it depends on their mass. First we will consider two mass ranges: Low mass star: from 0.4 M– to 8 M– and high mass stars: greater than 0.4 M–.
a. He shell fusion
i. Old stars with cores of carbon and oxygen do not get hot enough for these elements to fuse
ii. As the core gets richer and richer in C and O atoms the He fusion slows down and the core cools
iii. As a result the inner layers of the star, being cooler, collapse.
iv. As you might expect, this contracting causes these once cooler regions to get hot
v. As a result the layer of He just outside the C and O rich core reach a high enough temperature that He shell fusion can occur
b. He shell fusion heats up the star and it once again, for the last time, expands into a giant and the star moves out of the horizontal branch and into the giant region of the H-R diagram
i. Remember that in addition to He shell fusion there is still H shell fusion taking place in the layer just outside the He shell fusion layer
ii.
Stars that move into the giant phase for the second
time are called an asymptotic giant branch star (a.k.a. AGB star) (N.B. An asymptote of a real-valued
function y = f(x). In english this
means that as a ratio of two values, ‘x’ and ‘y’ approach infinity the ratio
becomes more and more exact. It applies to these type of stars because there
are two different kinds of fusion taking place in the star. The ratio of these
two types of fusion are asymptotic. For those of you that are studying caculaus
this graph of asymptots might be useful:
c. AGB stars are
i. Brighter than ever before, as much as 104 L–
ii. As large as 1AU or even larger, out to the orbit of Mars
iii. Destined to self-destruct
1. Before reaching this stage, as a giant star, they emit great quantities of their mass as stellar winds
2. Lower mass stars in this range emit stellar winds at a lower rate than higher mass stars
3. On the way to the AGB the mass reduction can be as much as 30% of the star’s total mass
4. As an AGB star they lose even more mass and are surrounded by large quantities of gas and dust
d. The final stages:
i. Since the stars have so little mass their C and O rich cores cannot reach fusion temperatures (6M K)
ii. Thermal runaway occurs:
1. The triple alpha process is extremely sensitive to temperature
2. As temperature goes up, even slightly, the He fusion rate skyrockets. This is a helium shell flash (not to be confused with the long ago helium flash)
3. The star expands as a result. The expansion causes cooling. The cooling slows the He fusion.
4. 100,000 years later the same process happens all over again and can happen several times while the star is in this phase
iii. When the star expands as a result of the He shell flash some of the outer layers cool enough so that the ionized atoms regain their electrons
iv. Photon pressure pushes these atoms further and further away from the star
v. Eventually enough mass is ejected from the star that He and H shell fusion stops
vi. The stellar matter continues to expand outward and there comes a time when the core, what is left of it, is visible. At this time the star becomes a planetary nebula (You must read the “Insight Into Science” on page 382!)
vii. Planetary Nebula:
1. Have nothing to do with planets!
2. Very common in our galaxy
a. 1800 have been identified
b. may be as many as 20k to 100k
3. Come in a variety of shapes, sizes, configurations and they make a very impressive astronomical photograph
4. Consist of as much as 85% of the mass of the star they came from
5. This is the matter that is available for the formation of Population I stars, like our sun
6. The matter of these nebula move away from the parent star at speeds of 10-30km/s (N.B. to convert km/s to miles per hour multiply by 2250!)
7. Last only 50k years
B) (13-2) The burned-out core of a low-mass star becomes a white dwarf
a.
White Dwarf:
i. Primarily made up of C and O with a thin layer of H and He
ii. Stable objects supported by electron degeneracy
iii. Roughly the size of earth with a density of 109kg/m3 (Compare this to the density of water which is 103kg/m3. This means that white dwarfs are a million times more dense than water!)
b. Evolutionary track on the H-R diagram
i. From the last phase as a giant they move, in astronomical terms, rapidly to the left sometimes, depending on mass, looping along the way
ii. After the crossing the main sequence line they turn sharply downwards to the white dwarf region
iii. White dwarfs take billions of years to cool
C) (13-3) White dwarfs in close binary systems can create powerful explosions
a. A white dwarf in a close binary system can gain mass from the other star in the form of H gas
i. This gas remains on the surface of the white dwarf
ii. As large quantities of H gas collect the layer gets thicker and thicker until the pressure is great enough to heat up the H (107K) so that it actually fuses
b. This fusion process creates a great deal of light and the event is called a nova
i. In our galaxy there are approximately 20 such nova events every year.
ii. All of these are not visible because their light is obscured by interstellar matter
c. New information:
i. The Hubble X-ray telescope and the Chandra observatory reveal
1. The smooth shell implied above may actually be clumps of H gas on the surface of the white dwarf
2. The degenerate matter in the white dwarf applies outward pressure. There is a limit to this outward push, which means white dwarf are limited to less than 1.4 M–.
3. This limit in mass is called the Chandrasekhar limit
ii. It seems there is a great deal more to learn about white dwarfs and the nova they produce
D) (13-4) Accreting white dwarfs in close binary systems can also explode as Type 1a supernovae
a. Type Ia supernova:
i. Remember that the upper limit of a white dwarf is 1.4 M–; in a semidetached binary system the companion star gives enough mass to the white dwarf that the Chandrasekhar limit is exceeded
ii. When the Chandrasekhar limit is exceeded the added mass increases the pressure which increases the temperature enough that carbon fusion starts in the core
iii. Since there are no outer layers to absorb the tremendous energy the whole star blows up!
b. In this explosive process heavier elements are made
i. Many of these elements are radioactive
ii. Especially abundant is a radioactive isotope of nickel which decays into cobalt
iii. The N to Co decay is responsible for most of the electromagnetic display of the Type Ia supernova
c. Type Ia supernova’s spectrum does not contain a hydrogen line, no surprise there since white dwarfs have no hydrogen!
d. The absolute magnitude of the Type Ia supernova reaches M = –19 (N.B. remember that for every change of 5 in absolute magnitude is a difference in brightness of 100 times. Since the absolute magnitude of the sun is M = 4.83; this means that the supernova is about 500 times brighter than the sun!)
e. Because of their brightness Type Ia supernovas can be seen from a great distance, even as far away as 109ly, that’s a billion light years!
f. The brightness of all Type Ia supernovas is the same, this makes them, like the Cepheid variable, a good way for astronomers to determine distance
i. Simply observe the supernova at its peak brightness
ii. Use the distance-magnitude relationship to
iii. Calculate the distance
II High-mass stars and Type-II Supernovae
Stars of 8 M– and greater there is sufficient gravitational force to compress the core which raises the temperature high enough to support carbon and oxygen fusion. This leads to the creation of more and more other heavy elements all the way up to Z = 26, Iron.
A) (13-5)
A series of fusion reactions in high-mass stars leads to luminous supergiants
a. When He fusion ends (Remember that the He has been converted to C and O) in high-mass stars there is enough mass to provide the pressure necessary to raise the core temperature high enough (600M K) to fuse carbon and oxygen
b. Nucleosynthesis
i. The process in which lower mass elements fuse to make higher mass elements
ii. Carbon fusion makes neon and magnesium
iii. Oxygen fusion makes sulfur, silicon and phosphorus
c. Since less massive elements make more massive elements each layer of elements must contain fewer and fewer atoms of the more massive element and the time to fuse the atoms is also less and less (N.B. be sure to take a look at Figure 13-10!)
i. Carbon fusion takes 600 years
ii. Neon fusion takes only a single year
iii. Oxygen fusion takes 6 months
iv. Silicon fusion into iron starts and stops in a single day
d. All
of this fusion creates a great deal of high energy photons which push the outer
layers of these stars further and further outward until the star reaches a size
that would fill the orbit of Jupiter, larger stars can fill a space 0.3ly in
diameter!
e. Eventually
the core of these giants is pure iron .
. . and something remarkable is about
to happen
B) (13-6) High-mass stars blow apart in violent supernova explosions
a. Unlike other less massive elements iron cannot fuse
i. The protons and neutrons in the iron nucleus are tightly bound
ii. Because of this tight bond no further energy can be extracted by fusing, i.e., if the nuclei did fuse no energy would be emitted
iii. This means that the nuclei are exceedingly stable
b. The only thing supporting the core against the tremendous pressure from the outer shells of the star is the electron degeneracy pressure
i. As more and more silicon fuses into iron the core exceeds the Chandrasekhar limit
ii. This causes the core to collapse
iii. When the core collapses a rapid series of cataclysms is triggered that ends with the star being torn apart within seconds
c. Photodisintegration
i. The temperature of the iron core is so high, 5G K, that the gamma ray photons have so much energy that they break apart the iron nuclei
ii. It takes millions of years for a star to reach the iron core phase and only 1/10 of a second to bring the iron back into its component protons and neutrons
iii. The density is still great enough that the protons and electrons are forces together making neutrons and, most important, lots and lots of neutrinos
iv. There are enough neutrinos and they have enough energy to provide pressure pushing the star’s core outward
d. What happens next:
i. ¼ of a second after the collapse begins, the collapse mentioned in b ii, the density of the core is 4x1017kg/m3, this is called nuclear density
ii. at nuclear density the stuff of the core stiffens and the collapse abruptly stops
iii. This happens so abruptly that the material actually bounces, this is called the core bounce
iv. Meanwhile, the collapsing outer layers have achieved speeds of 15% of the speed of light
v. The outward moving core matter from the bounce is moving out and it collides with the incoming outer shell matter. Imagine!
e. In a matter of hours the incoming matter reaches the outer regions of the star with a mighty blast and a Type II supernova is created!
f. How bright is it?
i. The giant star, before supernova, was 104 to 105 L–
ii. During the explosion the brightness increases to as much as 106 times more!
iii. This means that the Type II supernova is emits as much light as 100G suns!
g. As the layers of these stars is blasted into space
i. they are compressed by the neutrinos and the shock wave that temperatures can be high enough to cause fusion to take place in the expanding material
ii. The products of this fusion is the source of many of the heavier elements that eventually make up interstellar matter and becomes the material for population II stars
iii. However, these stars do not create the much heavier elements such as gold, platinum and silver
h. Over the course of its lifetime 25 M– stars lose more than 20 M– back into space
i. The spectrum:
i. Type Ia spectrum have no hydrogen
ii. Type II have hydrogen in their spectrum
j. Type Ia supernova dim gradually and at a steady rate while Type II alternate between periods of steep and gradual declines in brightness
C) (13-7)
Supernova remnants are observed in many places
a. How many?
i. While novae occur, about 20 every year supernovae are much less common
ii. Type Ia occur about once every 36 years per galaxy
iii. Type II occur about once every 44 years per galaxy
iv. Is it possible that none have occurred during your young lifetime? Consider the number of galaxies! The greater likelihood is that many have occurred since your birth, perhaps not; however, in the Milky Way.
b. Where?
i. Since Type II supernovae require high-mass stars and
ii. since high-mass stars require large molecular clouds and
iii. since large molecular clouds are found in the outer bands of a galaxy most Type II supernovae occur in the outer bands of a galaxy. (Remember, we are in the outer bands of the Milky Way!)
c. How do we see them?
i. There is so much interstellar gas and dust that we cannot see very far into our galaxy in visible light
ii. Long wavelength light can penetrate the interstellar gas and dust
iii. Many supernovae remnants are visible only at very long, radio wavelengths, or very short, X-ray wavelengths
d. When were they seen?
i. The last supernova seen in our galaxy was in 1604 and was studied closely by Johannes Kepler
ii. The last supernova before the 1604 event was in 1572, only 32 years earlier (Imagine, of you were a child in 1572 you might have seen two supernovae in your lifetime!)
iii. There have been no supernovae visible to the naked eye in our galaxy since 1572
iv. In 1987 a supernova (More below on this one!) was seen in the LMG (Large Magellanic Cloud), which is actually a galaxy about 168,000ly away. Imagine, the supernova was 1018 miles (That’s a billion, billion, or a billion gigamiles) away and the light of it was visible even in the daytime!
e. What happens to them?
i. After the supernovae explosion the stellar matter continues to spread out at super-super sonic speeds
ii. Collisions between the stellar matter and gas and dust already present in the interstellar medium causes the beautiful glowing objects visible in the radio and infrared wavelengths
iii. The ages of the nova remnants, and therefore the time of the supernova, can be determined by the size of the debris field
1. knowing the rate of expansion,
2. knowing the size of the field,
3. the time it took to travel the distances involved is a simple calculation
f. It is strongly recommended that you carefully study the many pictures of the supernovae in the book. In addition, you can easily google ‘supernova’, click on ‘images’, and be prepared to lose a lot of time looking at the beautiful images that keep coming and coming. You may even make one of these images the wallpaper on your desktop.
D) (13-8)
Cosmic rays are not rays at all
a. Supernovae explosions have enough energy to accelerate particles to 90% the speed of light!
i. These particle may or may not collide with other particles of interstellar material
ii. Collisions with particles of the interstellar medium will accelerate these particle to high speeds as well
iii. When these particles interact with the atmosphere of earth they are referred to as cosmic rays or primary cosmic rays
b. As you can see, cosmic rays are not rays at all
i. As often happens in naming astronomical phenomena, they are named before they are understood fully and although fuller understanding reveals the phenomena is misnamed, the name sticks anyway
ii. Consist mostly of hydrogen nuclei
iii. Consist of less than 1% of heavier elements
iv. Consist also of electrons and positrons
c. Origins:
i. Thought to be from supernova events because there were no other events that could give these particle the observed energy
ii. Recent data from the Advanced Composition Explorer show that some cosmic rays are composed of isotopes of nickel that are NOT produced by supernovae
iii. Another possible source of especially high energy cosmic rays may be particles emitted form supermassive black holes at the center of many galaxies
d. Cosmic ray particles collide with earth’s atmosphere 15 km above earth’s surface
i. This is a good thing because if they got all the way to the surface they have more than sufficient energy to cause damage to living tissue
ii. Collisions with atmospheric particles generates a cascade of collisions with other particles and reach earth’s surface with considerably less energy as a cosmic ray shower
iii. Secondary cosmic rays are particles within the atmosphere that were not there until the primary cosmic ray ‘created’ them as a result of collisions with upper atmosphere gases
E) (13-9)
Supernova 1987A offered a detailed look at a massive star’s death
a. Named for the year it was seen and since it was the first (and, it turned out, only) seen that year it is given the letter ‘A’ (Full name: SN 1987A)
b. Occurred in the LGM (Large Magellanic Cloud, some 1.6 kly away
c. What makes SN 1987A unique
i. It is nearby (nearby!)
ii. The first one that could be studied with modern equipment
iii. The star that went supernova was well studied before the event
iv. It went supernova while it was in the blue giant phase (The star oscillated between large red giant and less large blue giant phases. Prior to this event it was thought not possible for a star in the blue giant phase to supernova
d. Careful study of the SN confirmed many portions of the theory discussed earlier in this chapter (Remember that the information from 13-6 was based on mathematical models of stars with 25 M– )
e. Neutrinos from the collapsing Fe core were actually detected on earth at three different neutrino detectors one day before the actual supernova
III Neutron Stars and Pulsars
Stars between 8 M–
and 25 M–
lose a great deal of their mass before (20k years before!) they explode.
This mass surrounds the star so then it does explode the matter moving outward
slams into the matter already there. The cores, which are now mostly neutrons
because of the electron-proton collisions, become highly compressed and become
neutron matter, referred to as neutron stars. These objects are between
1.4 M–
and 3 M–.
They are highly stable.
A) (13-10) The cores of many Type II supernovae become neutron stars
a. There is a wonderful story about the progress from the theoretical proposition of the existence to the actual discovery of an actual neutron star. If you do not read this story you will miss out on a delightful adventure!
b. Neutron
degeneracy pressure
i. Neutrons packed tightly together cannot have the same quantum numbers (Pauli exclusion principle)
ii. Protons packed tightly together must move rapidly so that the quantum numbers are not the same
iii. This causes a great deal of pressure to build up so that the mass neutron stars can exceed the Chandrasekhar limit
iv. Neutron degeneracy pressure is greater than electron degeneracy pressure
c. Actual pulsars were first seen in 1968 (If you google this you must put the date into the search, otherwise you get a lot of useless twitter hits)
d. Younger pulsars have shorter periods than older pulsars
B) (13-11)
A rotating magnetic field explains the pulses from a neutron star
a. Recall that stars rotate, which means that stars have angular momentum
i. The law of conservation of angular momentum states that without outside forces, the angular momentum of a closed system must remain constant
ii. Here is how this law applies to a skater on earth:
1. When a skater spins with their arms outstretched the rate of spin is slow because their moment of inertia is high (L = Iw; angular momentum (L) equal the product of the moment of inertia and the angular speed.
2. The moment of inertia is a function of how far the mass that is rotating is from the axis of rotation: m x r, so I = (mr) w). Angular speed is a measure of how fast the object is spinning.
3. When they bring their arms in the moment of inertia is reduced (the mass of their arms is no longer far from the axis of rotation) and thus, to keep Li = Lf, the rate of spinning must increase
b. When a star collapses it becomes much smaller; however its angular momentum must be conserved so the smaller the star becomes the faster it must spin. A star the size of the sun rotates approximately once a month; when collapsed to the size of a neutron star it must rotate once a second!
c. Stars have magnetic fields; neutron stars do too. Magnetic fields are not necessarily oriented along the spin axis
d. Moving magnetic fields create electric fields
i. These powerful electric fields act on the protons and electrons at the star’s surface and
ii. These are channeled into space with a great deal of energy, which means at great speeds
iii. These very fast moving particles also emit energy as the electromagnetic fields accelerate them
iv. The result is that two thin beams of highly energetic particles and electromagnetic energy stream out of the neutron star’s north and south magnetic poles.
v. The stream is continuous; the stream does not pulsate
e. So, why call these things pulsars?
i. The lighthouse model
1. The light of a lighthouse rotates with a continuous beam of light, but, it is only visible when that beam crosses our line of sight
2. The continuous beam from a pulsar is visible only then that beam is aimed towards earth
3. Unless the magnetic poles of earth are exactly in line with earth we will never see the continuous beam from the neutron star
4. Since the line of sight from the pulsar is above or below a straight line of sight to earth we see the pulse only when it crosses the line of sight
ii. The lighthouse model explains why we see the neutron star appear to pulse
iii. The rate of pulse depends on
1. How far out of line the magnetic axis is from the line of sight to earth: less in line, longer pulse
2. The age of the neutron star: the older the neutron star the longer it period of pulsing
iv. Pulses can range from tens of seconds long to 10-2Hz
C) (13-12)
Rotating Neutron stars create other phenomena besides normal pulsars
a. The magnetar
i. If the neutron star is spinning fast enough (100+ times per second, or 100+Hz), and if it is very hot (1011K, or 100GK) convection will occur within
ii. This convention will add to the strength of the magnetic field
iii. Such an object is a magnetar
b. The magnetic fields generated by a magnetar are strong enough to buckle the surface of the neutron star
i. This buckling causes bursts of X-ray and even gamma ray photons
1. The buckling does not last long, only fractions of a second
2. The bursts of photons lasts as long as the burst that generated them
3. The surface will buckle again only hours later
ii. Since the bursts of gamma ray photons are at the low end of the gamma ray part of the spectrum they are called soft gamma rays (Sort of like UV A and UV B)
iii. Magnetars are sometimes called SGR for soft gamma ray repeaters
c. In 2006 anther type of emission was discovered coming out of rotating neutron stars
i. The emission consisted of photons primarily at the radio wavelength
ii. They lasted for only 1/1000 of a second (no wonder they were so difficult to find!)
iii. The pulsate anywhere from minutes to hours
iv. Called RRATs for rotating radio transmitters (Not nearly as cool as LGM1!)
d. What a RRAT really is, is still under investigation. They could be older neutron stars or they could be slowly rotating magnetars
D) (13-13)
Neutron stars have internal structure
a. Neutron stars, it turns out, are not pure neutron matter
i. Core: superfluid neutrons and Superconducting protons
1. A superfluid is a substance that flows with out friction, it has, literally, zero viscosity
2. A Superconducting substance conducts a current with zero resistance, and therefore no loss of energy with the flow of current or heat
ii. Middle layer: superfluid neutrons
iii. Final layer: crust made of dense nuclei and electrons
b. Even though a neutron star is only about 20km in diameter they are so dense that climbing a1mm bump would be as difficult as climbing mount Everest
c. There is evidence that neutron stars have ‘earth’ quakes. These cause a small and brief change in the star’s period of rotation, this is called a glitch
d. Most pulsars are single stars but astronomers have discovered 90 that have a companion and are referred to as binary pulsars
e. Some pulsars rotate at or greater than 1,000 times per second. Since these stand out as rather unusual, they are called millisecond pulsars
f. In 2004 astronomers saw, for the first time, a binary pulsar with each star being a neutron star. Because of the immense gravity of the orbits of these pulsars around each other, they can be used to test some important features of Einstein’s theory of general relativity
E) (13-14)
Colliding neutron stars may provide some of the heavy elements in the universe
a. Astronomers can detect the elements heavier than iron that exists in the interstellar medium
i. The total mass of these heavier elements is greater than what can be accounted for by the explosions of supernovae
ii. A great deal of effort was put in to find the source of the ‘extra’ elements heavier than iron
b. Computer simulation of what will happen when two neutron stars collide indicate that this is the most likely candidate for the source of the elements heavier than iron
F) (13-15)
Binary neutron stars create pulsating X-ray sources
a. Some binary neutron stars are coupled with a non-neutron star
i. This non-neutron star fills its Roche lobe
ii. Matter passes from the giant star to the neutron star
b. The magnetic field of the neutron star is still the source of energy for the beams of matter and energy streaming out from the magnetic poles
i. The matter from the giant star accelerates up to 0.5c as it falls into the neutron star
ii. There is enough energy to emit huge amounts of energy as gamma rays that can be 100k L–.
G) (13-16)
Neutron stars in binary systems can also emit powerful isolated bursts of
X-rays
a. Neutron
stars can acquire additional mass from a companion star
b. X-ray burster:
i. Emit X-rays at a constant level
ii. Suddenly and without warning they emit a burst of X-rays
iii. Perhaps this is caused by mass transfer in a binary system
1. The regular emission of X-rays is from the constantly falling matter from the companion star
2. Pressures and, therefore, temperatures, are high enough to fuse hydrogen
3. When the He form this fusion builds into a layer only an inch thick the He fuses
4. The He fusion causes the X-ray burst
H) (13-17)
Smaller, more exotic stellar remnants composed of quarks may exist
a. There is an upper limit to how large a neutron star can be
i. The tremendous pressure of the outer layers pushing in on the core of the neutron star is opposed by the neutron degeneracy pressure
ii. This creates an upper limit to the mass of these stars
iii. This upper limit is called the Oppenheimer-Volkov limit
iv. The Oppenheimer-Volker limit is 3 M–.
b. Neutrons (and protons) are made of quarks. Each particle is made of 3 quarks
c. Quarks cannot exist alone. In addition, quarks cannot exist alone. Furthermore quarks cannot exist alone. In case this is not clear: quarks cannot exist alone
i. If the mass of a neutron star becomes greater than 3 M– it is possible that the pressure could get so great that the neutrons are so crushed that the spaces between the protons is crushed and pure quark matter is created
1. Quarks must obey the Pauli exclusion principle
2. This causes the quark matter to exert pressure
ii. No one knows what the upper limit to a quark star could be
d. Recall that when matter falls into a neutron star it can reach speeds of 0.5c which means the escape speed is also 0.5c
i. If the neutron matter is compressed further and the mass becomes even more condensed and the density is so great the star’s escape speed becomes greater than the speed of light
ii. Such a star is now invisible because no light, or any other kind of photon, can escape from it
e. We are now ready to explore the most bizarre and fantastic objects in the entire universe: the black hole
I) (13-18)
Frontiers yet to be discovered
a. The telescopes in existence and planned are unlike anything that could have even been imagined only 10 years ago
i. These telescopes can see X-rays and gamma rays
ii. They can compensate for the various and changing densities of the atmosphere
iii. They can detect tiny changes in the background temperature of the entire universe!
b. These telescopes will be used to look for things we do not yet know of as you read these words
c. Imagine being the first to find a quark star!
d. Imagine bending space to your will by controlling quark matter
e. And we are still not talking about black holes!