Term
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1. red dwarfs
- very numerous
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Definition
| : these “red dwarfs” are much more numerous than massive stars in our galaxy. |
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Term
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1. red dwarfs
- long lifetimes:
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Definition
| since they are smaller in size, they last a lot more time than main sequence stars and giants of all classes |
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Term
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1. red dwarfs
- starspots
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Definition
show up as drops in light curve
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Term
red dwards
- flares and other evidence for activity
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Definition
: very common in red dwarfs because of lower mass
Especially active at younger age |
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Term
red dwarf
- minimum mass of a M.S star
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Definition
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Term
brown dwarfs
- “failed stars”
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Definition
| : are stars that did not gather 0.08 solar masses in their cloud also called “brown dwarfs” form because there isn’t enough mass to create heat at an optimal level needed to create fusion in the core |
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Term
brown dwarfs
young brown dwarfs as protostars : |
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Definition
: Not enough thermal energy to create fusion in the core, quantum pressure stops the star from contracting anymore. |
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Term
brown dwarfs
electron degeneracy pressure
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Definition
| : it is the pressure that keeps the star from further contracting into a MS star. (Depends on density alone) |
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Term
brown dwarfs
spectral types L,T,Y |
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Definition
| : new spectral types created for brown dwarfs, from cool to coolest. do NOT fall onto MS. |
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Term
brown dwarfs
cooling/fading track in the HR diagram |
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Definition
| : Ends in the lower right corner of the diagram beyond the red dwarfs. |
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Term
exoplanets
- direct vs indirect detection methods |
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Definition
1. direct is seeing the actual spectra and/or image of the planet,
2. indirect is measuring the parent star in order to receive information on the orbiting planet; includes
1.astrometric - looking at the wobble of the star
2. transit - when planet passes infront of star making a dip "eclipse" so its edge on
3. dopper/spectroscopic- Doppler shift of the star, we get the minimum mass of the planet, velocity, periodà which gives us the radius
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Term
exoplanets
gravitational tugs |
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Definition
| the gravitational effect the planet has on its host star, makes host star wobble that is the same period as the planets larger orbit. |
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Term
exoplanets
position wobble (astrometry) |
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Definition
the star does a little orbital tilt.
it is the accurate measurement of stellar objects’ positions. |
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Term
exoplanets
doppler wobble or radial velocity method (spectroscopy) |
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Definition
: Gives minimum mass and orbital period; combined astrometric and spectroscopic methods to get orbital tilt and mass.
--> Doppler shift of the star, we get the minimum mass of the planet, and the velocity,
(period gives us the radius)
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Term
exoplanets
transits (light curves) |
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Definition
| : The light curves measures the brightness of the star over time to find patterns. When a planets crosses in front of its parent star, creating a dip in the light curve. which shows us the radius of the planet and orbital period. it gives us the orbital tilt, and in conjunction with the doppler method the planet’s actual mass can be calculated. |
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Term
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Definition
:
jupiter-size planets orbiting another star very closely therefore making it very hot in temperature. they have considerably short periods |
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Term
exoplanets
habitable zones |
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Definition
The habitable zone is region in which a planet orbiting a particular star would be capable of having liquid water (which could possibly support life) depending on the planet, i.e. its luminosity, distance from the star, and temperature factors, the HZ is either further or closer away from the parent star.
”Goldilocks planets”-planets where water can exist in liquid state
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Term
exoplanets
NASA Kepler satellite |
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Definition
| a NASA discovery shuttle launched in 2009, that uses the transit method for searching and locating exoplanets. First few months it found jupiter-sized planets, but its goal was to detect earth-size planets ( which it has ). Frequencies of large vs. small planets must take the “bias” of the transit method into account. |
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Term
1. pre main sequence or protostar phase
contraction under gravity |
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Definition
| a protostar assembles from a collapsing cloud fragment. it is concealed beneath a shroud of dusty gas. the protostar shrinks and heats as Gravitational Potential Energy is converted into thermal energy |
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Term
1. pre main sequence or protostar phase
- conversion to thermal energy |
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Definition
: GPE converts to Thermal energy
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Term
1. pre main sequence or protostar phase
beginning of core H fusion |
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Definition
| : when the star becomes hot enough due to radiation, it is able to fuse H into He in the core. (When core reaches 10^7 K) |
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Term
1. pre main sequence or protostar phase
path in the HR diagram |
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Definition
| : comes up from behind the MS (to the right) then angles into land on the MS- where at depends on the mass and temperature of the star. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
core H exhaustion |
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Definition
| : when the MS star has finished fusing H into He in the core, the area right above the core begins burning H.. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
up the red giant branch |
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Definition
| : the region where H shell burning becomes hotter and higher pressured, so the outer layers of the star expand, creating a red giant. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
core He-fusion |
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Definition
| : this occurs in the horizontal branch as the He core heats up, called the “triple alpha process” where He becomes C,O. (Seen as a “Second main sequence period, 10^8K) |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
horizontal branch |
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Definition
| : 3rd stage in life of low-mass star, which has a Helium burning core, burn He to C. the star is now smaller and hotter. On the HR diagram the horizontal branch extends quite far to the blue of the red giants. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
double shell burning stage (Asymptotic giant branch “AGB”)
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Definition
| : 4th stage in life of a low-mass star, consists of a “double shell burning” where He is fusing in the region above the core and H is fusing in the shell above that. the star becomes cooler, larger in size, and more luminous. Its path in the HR Diagram asymptotically falls back and approaches the red giant branch. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
- mira variables
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Definition
: it is the tendency for AGB stars to pulsate every 1-2 years, which means they swell up and contract. mira the wonderful” is the most famous example of this.
"dredge up" which release "thermal pulses"
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
mass loss
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Definition
| : The outer layers swell and contract, and mass starts leaking away in a flow called a “stellar wind.” certain elements start condensing into small solid particles called dust grains. once dust forms, “superwinds” are created. These superwinds form the “seeds” of future planets. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
neutron capture reactions : |
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Definition
iron is the dead end for standard fusion. after that, heavier elements are only created through neutron capture reactions. there is a slow process and a fast process, or r-process. in the s-process, typically a low mass star phenomena, neutrons are added one at a time followed by a beta-decay which changes the element. in the r-process, a high mass star process, the pre-existing nuclei is flooded with neutrons, making neutron rich isotopes. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
- thermal pulses
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Definition
| : the predicted upward spikes in the rate of helium fusion, occurring every few thousand years, that occur near the end of a low-mass star’s life. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
- dredge up
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Definition
| : associated with AGB stars that are unstable. Convection passes and releases all these products from the core called thermal pulses into space. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
- planetary nebula
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Definition
| : all of the stellar dust/wind (gas) that flows out into space from an AGB star late in its life, and this is the next generation of stars. |
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Term
2. post M.S evolution of low & intermediate mass stars (up to 8 SM)
white dwarf |
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Definition
| : The core (composed of C and O made by earlier reactions) contracts to high density, essentially building a white dwarf in the middle of the star. The core is supported by electron degeneracy pressure, which prevents it from contracting any further. the maximum mass is 1.4 solar masses, because any greater the electrons would surpass the speed of light. this is called the chandrasekhar limit. after the planetary nebula ejects into space, it leaves a white dwarf, which is small but very massive. white dwarfs obey an inverse mass relationship, meaning the smaller they are the more massive they are. we can compare a white dwarf to a hot potato cooling off over time. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
CNO cycle |
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Definition
| : the cycle of reactions by which intermediate and high-mass stars fuse hydrogen into helium by using carbon as a catalyst. Instead of through the familiar p-p reaction that happens in the sun. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
Triple alpha and higher fusion reactions
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Definition
| : triple alpha process creates C, O. higher fusion reactions occur when He fuel is exhausted, and nuclei are created that are multiples of He, i.e. O, Ne, Mg, etc. (Only in high mass stars) |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- “onion” structure of evolved star
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Definition
| : the different layers of elements inside a high mass star, with an inert iron core. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- core collapse
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Definition
| : occurs due to photodisintegration; no pressure to support the core anymore. if neutron degeneracy pressure is insufficient, core will collapse into a black hole. (Core greater than about 3 solar masses) |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- photodisintegration
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Definition
| : high energy photons collide with Iron nuclei, creating free protons, neutrons, and helium nuclei. Since the energy of the photon is absorbed the temperature goes down. photodisintegration uses up energy, so pressure falls rapidly and the core collapses |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- neutronization |
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Definition
| : electrons combine with protons in the extremely dense core of a high mass star to create neutrons and neutrinos. The neutrinos interact frequently, so they do a random walk in the core, this causes the core to boil which brings heat and neutrinos to its surface. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- neutrino burst |
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Definition
| :Due to Neutronization, the core becomes very compact and instable which gives rise to a sudden burst of neutrinos coming out of the core. This is an indicator of a supernova explosion, for neutrinos will reach earth much faster than radiation. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- supernova explosion
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Definition
: The outer layers of the star lose pressure support, so fall inward. The core collapse is suddenly halted by neutron degeneracy pressure, so the outer layers crash into it and bounce off, creating the supernova explosion. Neutrinos are involved somehow.
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
more neutron capture reactions ( rapid “R” process)
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Definition
| : r-process is the flooding of neutrons and occurs very quickly, creating neutron rich isotopes. This only happens in high mass stars and leads to the creation of heavier metals past iron. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- jets
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Definition
| : The rotation of the star causes the poles of the star to become a natural pressure outlet. Large amounts of material being ejected at the poles create jets. The magnetic field of the star can also help strengthen the jets. in some of the most massive stars, this can be the cause of gamma ray bursts. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- nucleosynthesis |
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Definition
| - The creation of new elements from other, usually lighter ones. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- supernova 1987A |
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Definition
| : Nearest observed supernova in modern astronomy: 168,000 ly away in the Large Magellanic Cloud (LMC) “Occurred” in 1987, the explosion happened 168,000 years ago, the light reached us in 1987. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
supernova remnants
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Definition
: The shock from the supernova that travels outward at
about 10% the speed of light.
The ejecta carries the newly synthesized elements with it into the interstellar medium, ready to become the next generation of stars. |
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Term
3. post M.S evolution of High mass stars ( over 8 SM)
- crab nebula
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Definition
| : Actual Supernova recorded by Arab, Chinese, and Japanese astronomers in 1054 AD. Nebula first observed in 1731 by John Bevis, and independently again in 1758 by Charles Messier. It also left a pulsar behind .Indirect proof of Einstein’s theory of general relativity, namely “gravitational radiation” |
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Term
1. white dwarf, former cores of AGB stars
end states of low & intermediate mass stars |
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Definition
| : red giant branch (He core with H>He outside), horizontal branch (He>C in core), asymptotic giant branch (H and He both fuse in shell), planetary nebula (cost-off outer layers), white dwarf (nearly degenerate stellar core of Carbon) |
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Term
1. white dwarf, former cores of AGB stars
- electron degeneracy pressure
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Definition
| : degeneracy pressure exerted by electrons, as in brown dwarfs and white dwarfs. Forces the core of these two to stop compressing. |
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Term
1. white dwarf, former cores of AGB stars
- mass/radius relation
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Definition
| : white dwarfs obey an inverse mass relationship, which means the smaller they are the more massive they are. (Up to 1.4 M = Chandrasekhar limit) |
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Term
1. white dwarf, former cores of AGB stars
- cooling tracks and cooling ages
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Definition
| : The white dwarf cools off and grows dimmer with time, sliding down along a line of constant radius in the H-R diagram. |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- neutron degeneracy pressure |
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Definition
| : increases density so When neutrons are packed together, as they are in a neutron star, the number of available low energy states is too small and many neutrons are forced into high energy states. These high energy neutrons make up the entire pressure supporting the neutron star. |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- pulsars
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Definition
| : a neutron star, pulsating radiation (not thermal, only radio waves) and rotating at extremely high speeds. they form from supernova remnants. |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- synchrotron radiation
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Definition
: The magnetic radiation in the pulsar beams is not thermal emission. It has a different spectral shape from a blackbody, being very strong at radio wavelengths.
lightmodel house
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Term
2. neutron stars, collapsed cores of high mass star supernova
- lighthouse model
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Definition
| : When the beam is briefly pointed at us, the observers, we see a brighter star image than when it has swept past and points in a different direction. |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- pulsar slowdowns and glitches
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Definition
| : pulsars slow down with age and become dimmer. |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- association of pulsars with supernova remnants
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Definition
| : pulsars are left behind after a supernova explosion, therefore confirming the theory that neutron stars (pulsars and magnetars) are created and left behind after a supernovae. |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- binary pulsars
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Definition
| : pulsar in a binary system |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- pulsar planets
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Definition
| : It is speculated that the planets form in an accretion disk around the pulsar |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- magnetars
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Definition
| : neutron stars with extremely strong magnetic fields |
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Term
2. neutron stars, collapsed cores of high mass star supernova
- millisecond pulsar
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Definition
| s : ”rejuvenated” pulsars that spin at least 500-1000 times a second. due to mass transfer from its binary companion and the accretion disk onto the pulsar. |
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Term
1. What are the differences between a red dwarf, brown dwarf, and white dwarf? Where is each located in the HR diagram and how do their positions change with time?
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Definition
1. red dwarf - are supported by nuclear fusion. masses > 0.08sm.
2. brown dwarfs - are too small, so they can’t be supported by nuclear fusion. they are supported by electron degeneracy pressure. mass below 0.08 solar masses.
3. white dwarfs - are supported by electron degeneracy pressure. small, but very massively compact.
- (look and learn from the HR diagram ) their position change with time as they continue to evolve throughout their stages of life. Brown dwarfs stay as brown dwarfs in the lower right corner of the diagram under the red dwarfs, red dwarfs eventually move up the M.S position and continue to evolve (very very long process since they’re smaller and stay in that stage more time) and possibly becoming giants (upper right corner) then white dwarfs. After it is turned in a white dwarf, they slide down along a line of constant radius in the H-R diagram. |
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Term
2. Consider the CNO cycle of nuclear reactions and the “triple-alpha” process, both of which involve C and O. Describe what happens in each sets of reactions: what is the input (fuel), and what is the output (product)? In what stars, and where within these stars, do they take place?
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Definition
the triple alpha- takes helium and makes carbon and oxygen. this occurs in low mass horizontal branch stars in the He burning core.
the CNO cycle occurs in higher mass stars and it means that carbon is a catalyst in nuclear fusion, or the fusion of hydrogen into helium. requires a high core temperature.
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Term
3. Why is looking in the infrared part of the electromagnetic spectrum a good strategy for finding brown dwarfs? If you found an object that was brighter in the infrared than in the visible, how would you confirm/check on whether it is in fact a brown dwarf, rather than something else?
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Definition
brown dwarfs are very cool and lie beyond the red dwarfs, so it is logical their spectrum would appear in the infrared. just a guess: you could measure the radius to see how small the object is; if it is smaller than a red dwarf needs to be then it is probably a red dwarf. you could use the reflex motion method.
Wouldn’t you just take its spectral lines to confirm if it was a brown dwarf, i.e. L, T, Y?
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Yes. while it is true that brown dwarfs peak in the infrared, they are defined by the pattern of their absorption lines L,T,Y, which reveal larger molecules and therefore cooler end on the EM spectrum. |
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Term
4. What are the maximum and minimum masses for brown dwarfs, Main Sequence stars, white dwarfs, and neutron stars? (Hint: In some cases there might not be a maximum and/or minimum value.) What are the physical reasons for these maximum/minimum values?
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Definition
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White dwarf minimum mass is 0.08, max mass is 1.4
Neutron star minimum mass is 1.4 , max mass is 2-3
Blackhole minimum mass 2-3, no maximum
the minimum mass for a main sequence is 0.08 solar masses / the maximum for a main sequence is 250+ sm
the maximum mass for a brown dwarf is anything less than 0.08 solar masses / the minimum is probably not known, or negligible
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Term
5. What are the three major “indirect” methods for finding exoplanets? In what way are they “indirect”? What kind of measurements do you need to make, to apply each method? Which of them have been more successful, and which less successful?
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Definition
1. transit method - measure the transit of a planet in front of a star. (Finds radius of planet and is edge on)
2. positional shift - measure the shift in the star’s position as a planet orbits it
3. doppler shift - measure the doppler shift of the star’s position as a planet orbits it (Minimum mass) First successful method of finding exoplanets.
transit and doppler are successful working together!
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Term
6. What are the properties of a “hot Jupiter”? What causes it to be hot?
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Definition
| - They have to be Jupiter-sized planets, orbiting really close to their host star which causes them to be really hot. they have short periods. |
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Term
7. Describe some of the discoveries of exoplanets that astronomers found surprising.
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Definition
- Hot Jupiters
- White dwarfs/pulsars in a binary system
- Goldilocks planets
- multi planet systems |
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Term
8. How does the Kepler satellite search for exoplanets? How successful has it been?
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Definition
| - The Kepler satellite uses the transit method to find planets; so far it has found many multi planet systems, some binary star planet systems, and many smaller planets. It has found jupiter-sized planets and also earth-size planets, so very successful! Also has found planets with a potential for life. |
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Term
9. What are the observable properties of a protostar, and where does it lie in the HR diagram?
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Definition
| - A protostar has mass and rotational velocity (and therefore angular momentum). Proto stars lie right outside the HR diagram, and move inwards, right beneath the giants since they have around the same apparent brightness. The protostars come from the gases and waste from supernovas. |
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Term
10. Describe the major energy-producing fusion reactions that occur in low to intermediate-mass stars. What are the inputs and the products? Where in the stars do the reactions occur?
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Definition
- During the life of a low to intermediate-mass star, the star produces energy solely through hydrogen-burning in the core, which fuses 4 H atoms to create one He atom. After the star runs out of hydrogen in its core, it contracts and creates a helium core with a hydrogen-burning shell surrounding it.
The core begins helium-burning;under pressure from the star it fuses three helium atoms to create a carbon atom. By adding another helium atom oxygen is formed. The core continues this process until it is entirely carbon and oxygen.
While this is going on, the hydrogen-burning shell takes elements excreted by the core to use in what is called the CNO cycle. Carbon is used as a catalyst in a series of fusions with hydrogen that end up making a helium atom + a carbon atom. |
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Term
11. Cite the (6 or so) major stages in the life cycle of the lower-mass stars (less than 8 M¤). Summarize the physical properties of the star at these stages, the energy production mechanisms, the kind of pressure that supports them, and the path in the HR diagram.
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Definition
- 1. Main Sequence: H core burning: H → He in core ! (small)
2. Red Giant: H shell-burning: H → He outside the He core! (bigger) Goes towards the upper right corner of the H-R diagram while the core contracts.
3. Horizontal Branch: He → C in the core, H → He in shell! (gets smaller again) Moves left on the H-R diagram towards the blue side.
4. AGB or Double Shell Burning: H and He both fuse in shells,CO core becomes degenerate! (gets even bigger again) Moves back right towards the Red Giants.
5. Planetary Nebula lifts off, leaves white dwarf behind!
6. White dwarf: Excretes the energy produced, does not grow or shrink due to becoming electron degenerate and slides down along a line of constant radius in the H-R diagram.
Crystallizes and becomes a diamond. |
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Term
12. Cite the major stages in the life cycle of the higher-mass stars (more than 8 M¤). Summarize the physical properties of the star, the energy production mechanisms, and the path in the HR diagram. Which stages are in common with the lower-mass stars, and which are different?
- life cycle - protstar, massive star, red supergiant, blue supergiant, supernova, black hole or neutron star
physical properties - Massive star that his hot and large, gets larger and cools off, starts to “onionize”(outside ---> inside) hydrogen, helium, carbon, oxygen, neon, magnesium, silicon, and finally iron, collapses into a neutron star with a supernova remnant.
energy production - massive star H -> He in core. Red supergiant H shell burns, Blue Supergiant He -> C and O in core. Once core has turned into Iron it collapses.
Similar stages as lower-mass stars
– Hydrogen core fusion (Main Sequence)
– Hydrogen shell burning (red supergiant)
– Helium core fusion (blue supergiant)
position in HR diagram : Starts in the upper left of the main sequence, begins moving right on diagram by cooling off and expanding, as the shells of fusion around the core increase in number, the star swings “back and forth” between the red and blue sides of the HR diagram. |
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Definition
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Term
13. What are the similarities and differences between the event that throws off the outer layers of lower vs. higher-mass stars at the ends of their lives? What are their expanding debris called?
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Definition
the similarities: At the ends of their lives once the lower mass stars progress past Double shell burning it become unstable due to CO core becoming degenerate and starts to excrete the “planetary nebulae”. This is similar to the higher-mass stars progress to having an iron core it collapses into a neutron star due to no more energy able to be created and starts to excrete its outer layers as “supernova remnants”.
The differences is that low mass stars expel all their outer material layers leaving behind the core, while the high mass stars there core gets so dense with iron that all the material falls in at once and they just “bounce off” which creates a supernova explosion.
Another difference is that the lower mass stars get thrown off due to their center being degenerate while the high-mass stars core becomes iron which doesn’t allow any more contraction. If a higher- mass stars core exceeds 2-3M mass it will collapse under pressure causing a black hole. |
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Term
14. Where and how in nature are the elements heavier than Fe (iron) made?
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Definition
| - Stars age and lose most of their mass when it is ejected late in the stellar lifetimes, thereby enriching the interstellar gas in the abundances of elements heavier than helium. For the creation of elements during the explosion of a star, the term nucleosynthesis is used. Also called stellar recycling. elements heavier than iron are formed by neutron capturing processes. This causes different levels of Iron isotopes which disintegrate into heavier metals. |
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Term
15. Once formed, how do a white dwarf’s properties change with time?
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Definition
- With time, the white dwarf will eventually cool off and lose its energy. It is a retired star, destined to become a huge crystallized rock sitting in space.
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Term
16.What is a pulsar? Once formed, how does its properties change with time?
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Definition
| - a neutron star, pulsating radiation (not thermal, only radio waves) and rotating at extremely high speeds. With time it could either gain even more speed (if it has a companion star) or typically lose rotational speed over time with age which causes it to dim and stop being visible. |
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Term
17. Are there neutron stars that are not pulsars? What properties do or would they have, or lack?
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Definition
| - Yes there is. These “normal” neutron stars do not produce the jets that pulsars would likely produce. However they are spinning relatively fast as pulsars are. |
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Term
18. Compare white dwarfs and neutron stars in terms of: mass, radius, density, composition.
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Definition
- White dwarfs tend to have a smaller mass than neutron stars; they are formed from lower mass stars. However, their radii are much bigger than that of neutron stars, which tend to be the size of a small city (such as Austin). Therefore the density of neutron stars is far greater than that of white dwarfs.
As far as composition goes, white dwarfs are composed of mostly carbon and oxygen, with a hydrogen outer layer; neutron stars are composed entirely of neutrons (who would have guessed).
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Term
19. What can be learned from a pulsar that is found to be in a binary system?
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Definition
It can be learned that new planets may form from the material after a supernova explosion in the accretion disk around the pulsar.
We also see the period slowing down over time, 2 pulsars getting closer, and periods are increasing, they have to give up energy (gravitational waves) carrying energy away from the binary system.
- this prove einsteins theory of general relativity
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Term
20. Why was Supernova 1987A an important event for astronomers, in terms of confirming theories about supernovae?
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Definition
- Well it was the 1st supernova observed in modern astronomy. And its important because according to our theories about supernovae, they should leave behind neutron stars. But this 1987A has not shown evidence of a neutron star. Does this mean that there isn’t one there? Not exactly.
The key point about SN 1987A was that a neutrino burst was seen, emitted when the core is “neutronized.” However, no pulsar has been seen in the remnant of SN 1987A to date. !
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