Neutron stars are the remnants of collapsed massive stars that have densities greater than atomic nuclei. They form when the core of a massive star collapses into a ball about 10-20 km in diameter. Some neutron stars spin rapidly and emit beams of electromagnetic radiation that pulse as the star rotates, known as pulsars. Evidence shows that neutron stars can have planets and exist in binary systems, pulling matter from a companion star. When the core of a collapsing star is over 3 solar masses, it will collapse into a black hole from which even light cannot escape. Black holes reveal themselves through their gravitational effects on nearby objects like binary companions. Gamma ray bursts are very bright flashes of gamma rays that come from extremely energetic explosions and are
This document discusses pulsars and provides information about them. It begins by listing the group members and topics to be discussed, including an introduction to pulsars, their properties, discovery, formation from neutron stars, examples of the Crab pulsar and binary pulsars, and their radiating mechanism. It then provides details on the properties of pulsars, their extremely high density, classification, and the discovery of the first pulsar PSR B1919+21. The document summarizes how pulsars are formed from the collapse and rotation of massive stars, and discusses the Crab pulsar and binary pulsars in more detail. It concludes by outlining some applications and milestones of pulsar research, including their use in gravitational wave
The document discusses neutron stars and pulsars. It begins by outlining predictions about neutron stars, including their small radius of 10-80 km but large mass over 1.4 times the sun's mass. It then explains how conservation of angular momentum causes neutron stars to spin rapidly as the core collapses. The discovery of pulsars is summarized, including how their periodic emission can be explained by a rotating misaligned magnetic field. The document concludes by briefly introducing black holes and relating them to Einstein's theory of general relativity.
Pawan Kumar Relativistic jets in tidal disruption eventsBaurzhan Alzhanov
- Fast radio bursts (FRBs) are short, intense radio pulses that last about 1 millisecond. One FRB source produced multiple outbursts over several years.
- The leading model is that FRBs originate from young, highly magnetic neutron stars called magnetars. Charged particles are accelerated by magnetic reconnection, producing coherent curvature radiation observed as FRBs.
- FRBs provide insights into neutron star physics and energetic processes in magnetar magnetospheres. Predictions include observing FRB-like bursts at higher frequencies.
After a supernova, a neutron star may form from the dense core. Neutron stars are extremely dense and spin rapidly, appearing as pulsars due to their intense magnetic fields and lighthouse effect. Neutron stars in binaries may become X-ray bursters or millisecond pulsars. Gamma-ray bursts are likely caused by colliding neutron stars or hypernovae. If the core is over 3 solar masses, it will collapse into a black hole requiring general relativity to describe. Anything within the event horizon of a black hole cannot escape.
Black holes are regions of space where gravity is so strong that not even light can escape. They form when very massive stars collapse at the end of their life cycles. While black holes cannot be seen directly, astronomers can detect them by observing their effects on nearby objects like stars and gas, and through detection of x-rays emitted during accretion. Black holes come in different sizes, from stellar-mass black holes up to supermassive black holes that may exist at the centers of galaxies.
This document discusses super massive black holes. It begins with definitions of black holes and explanations of escape velocity and Schwarzschild radius. It then discusses how normal sized black holes form from massive stars undergoing supernovas. The document suggests that super massive black holes could exist in the centers of massive galaxies and may have formed from early universe "lumps" or grown over time through mergers. Active galactic nuclei and quasars are believed to be powered by super massive black holes. Optical jets, tidal forces, and cannibalism are characteristics of active galactic nuclei. The fate of the universe is speculated to be a cold dark death as all black holes evaporate over immense timescales.
This document discusses super massive black holes. It begins with definitions of black holes and explanations of escape velocity and Schwarzschild radius. It then discusses how normal sized black holes form from massive stars undergoing supernovas. The document suggests that super massive black holes could exist in the centers of massive galaxies and may have formed from early density fluctuations in the universe, stellar seeds accumulating matter, or the collapse of whole star clusters. Active galactic nuclei containing super massive black holes are observed and theories for their formation and characteristics like optical jets and tidal forces are presented.
The document discusses black holes and their properties. It describes how John Archibald Wheeler coined the term "black hole" and how Pierre Simon Laplace first proposed the concept in 1795, calculating that an object compressed into a small enough radius would have an escape velocity greater than the speed of light. It provides details on escape velocity and the event horizon of a black hole, beyond which nothing, not even light, can escape. The document classifies different types of black holes by mass and size.
This document discusses pulsars and provides information about them. It begins by listing the group members and topics to be discussed, including an introduction to pulsars, their properties, discovery, formation from neutron stars, examples of the Crab pulsar and binary pulsars, and their radiating mechanism. It then provides details on the properties of pulsars, their extremely high density, classification, and the discovery of the first pulsar PSR B1919+21. The document summarizes how pulsars are formed from the collapse and rotation of massive stars, and discusses the Crab pulsar and binary pulsars in more detail. It concludes by outlining some applications and milestones of pulsar research, including their use in gravitational wave
The document discusses neutron stars and pulsars. It begins by outlining predictions about neutron stars, including their small radius of 10-80 km but large mass over 1.4 times the sun's mass. It then explains how conservation of angular momentum causes neutron stars to spin rapidly as the core collapses. The discovery of pulsars is summarized, including how their periodic emission can be explained by a rotating misaligned magnetic field. The document concludes by briefly introducing black holes and relating them to Einstein's theory of general relativity.
Pawan Kumar Relativistic jets in tidal disruption eventsBaurzhan Alzhanov
- Fast radio bursts (FRBs) are short, intense radio pulses that last about 1 millisecond. One FRB source produced multiple outbursts over several years.
- The leading model is that FRBs originate from young, highly magnetic neutron stars called magnetars. Charged particles are accelerated by magnetic reconnection, producing coherent curvature radiation observed as FRBs.
- FRBs provide insights into neutron star physics and energetic processes in magnetar magnetospheres. Predictions include observing FRB-like bursts at higher frequencies.
After a supernova, a neutron star may form from the dense core. Neutron stars are extremely dense and spin rapidly, appearing as pulsars due to their intense magnetic fields and lighthouse effect. Neutron stars in binaries may become X-ray bursters or millisecond pulsars. Gamma-ray bursts are likely caused by colliding neutron stars or hypernovae. If the core is over 3 solar masses, it will collapse into a black hole requiring general relativity to describe. Anything within the event horizon of a black hole cannot escape.
Black holes are regions of space where gravity is so strong that not even light can escape. They form when very massive stars collapse at the end of their life cycles. While black holes cannot be seen directly, astronomers can detect them by observing their effects on nearby objects like stars and gas, and through detection of x-rays emitted during accretion. Black holes come in different sizes, from stellar-mass black holes up to supermassive black holes that may exist at the centers of galaxies.
This document discusses super massive black holes. It begins with definitions of black holes and explanations of escape velocity and Schwarzschild radius. It then discusses how normal sized black holes form from massive stars undergoing supernovas. The document suggests that super massive black holes could exist in the centers of massive galaxies and may have formed from early universe "lumps" or grown over time through mergers. Active galactic nuclei and quasars are believed to be powered by super massive black holes. Optical jets, tidal forces, and cannibalism are characteristics of active galactic nuclei. The fate of the universe is speculated to be a cold dark death as all black holes evaporate over immense timescales.
This document discusses super massive black holes. It begins with definitions of black holes and explanations of escape velocity and Schwarzschild radius. It then discusses how normal sized black holes form from massive stars undergoing supernovas. The document suggests that super massive black holes could exist in the centers of massive galaxies and may have formed from early density fluctuations in the universe, stellar seeds accumulating matter, or the collapse of whole star clusters. Active galactic nuclei containing super massive black holes are observed and theories for their formation and characteristics like optical jets and tidal forces are presented.
The document discusses black holes and their properties. It describes how John Archibald Wheeler coined the term "black hole" and how Pierre Simon Laplace first proposed the concept in 1795, calculating that an object compressed into a small enough radius would have an escape velocity greater than the speed of light. It provides details on escape velocity and the event horizon of a black hole, beyond which nothing, not even light, can escape. The document classifies different types of black holes by mass and size.
1) Neutron stars are the remnants of collapsed stars that have a mass greater than 1.4 solar masses. They form during type II supernovae following the collapse of massive red supergiant stars.
2) Pulsars are a type of neutron star that emit beams of electromagnetic radiation and appear to pulse due to their rotation. They were first discovered by Jocelyn Bell in 1967 through detecting their regular radio pulses.
3) Gravitational waves are ripples in spacetime caused by accelerating massive objects like neutron stars and black holes. Detecting gravitational waves from binary neutron star systems could provide insights into energetic cosmic events and test Einstein's theory of general relativity.
The document discusses the evolution and deaths of stars. It describes how low-mass stars like the Sun will evolve into red giants and planetary nebulae over billions of years. More massive stars may explode as supernovae, producing neutron stars or black holes and spreading heavy elements throughout space. Neutron stars can be observed as pulsars that emit beams of radiation. The origins of elements on Earth and phenomena like cosmic rays and pulsars are also examined.
Astronomy - State of the Art - GalaxiesChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the properties of galaxies are discussed, including supermassive black holes and dark matter.
Using radio observations, astronomers may be able to detect and characterize exoplanets by observing radio emissions from their magnetospheres. Planetary magnetospheres are theorized to produce bursts of decametric radiation through interactions with the solar wind that distort magnetic field lines and accelerate charged particles. While difficult to detect over a host star's emissions, observation of planetary radio signals could provide information on properties like the presence, size, and composition of a magnetosphere, as well as any orbiting satellites. The LOFAR radio telescope may enable the first detections of exoplanetary radio emissions within the next decade.
Space weather and potential impact on earth’s climate dec 19 10 v2Poramate Minsiri
This document discusses space weather and its potential impacts on Earth's climate and seismic activity. It provides an overview of the solar system and its dynamics, as well as how our solar system interacts with the Milky Way galaxy and larger universe. Recent observations have found evidence that the outer boundaries of our solar system are being compressed as we pass through Galactic clouds, allowing more cosmic rays and energetic particles to enter the inner solar system. This could affect Earth's climate and increase seismic activity. The document also discusses changes observed on other planets in our solar system, such as the growth of dark spots on Pluto and changes in cloud cover on Mars.
There are several types of ultra-compact binary star systems that orbit each other with periods of less than an hour. These systems emit gravitational waves due to their strong gravitational fields changing over time. The Laser Interferometer Space Antenna (LISA) mission aims to detect these gravitational waves. While current ground-based detectors cannot detect the waves from ultra-compact binaries, LISA may be able to do so due to observing from space. The document provides data on four example binary systems and calculates their orbital decay rates and the strain of the gravitational waves emitted.
1) Asteroids are rocky bodies too small to be called planets that orbit the sun, with many located in the asteroid belt between Mars and Jupiter. Some asteroids pass close to Earth and are called Near-Earth Objects.
2) The sun is a hot ball of gas at the center of the solar system that provides the energy and heat for life on Earth. It is one of billions of stars in the Milky Way galaxy.
3) Supernovas occur when massive stars explode at the end of their life cycles, around once every 50 years in a galaxy the size of the Milky Way. Less massive stars like the sun will swell into red giants before collapsing into white dwarfs instead of exploding.
3C 273 was one of the first quasars discovered in 1963. It remains one of the brightest and best studied quasars. It is located approximately 3 billion light years from Earth and radiates energy equivalent to 1014 times the luminosity of the Sun. 3C 273 plays a key role in understanding the nature of quasars as powered by accretion disks around supermassive black holes. It continues to be intensely observed across the electromagnetic spectrum to better understand the physics occurring in these energetic and distant cosmic objects.
Big Bang Theory & Other Recent Sciences || 2014 - Dr. Mahbub Khaniqra tube
RECENT SCIENCES
Big Bang, Dark Matter, Dark Energy, Black Hole, Neutrino, God Particle, Higgs Field, Graviton, Expansion of Universe, and Search for Life elsewhere in the Cosmos
1) The document hypothesizes that dark matter images were accidentally recorded by cameras on the TSS-1R satellite during a 1996 NASA mission mishap. Disk-like images seen moving beyond the receding satellite are proposed to be evidence of dark matter.
2) It further conjectures that these disk images each represent two single-notch 2D disks "stuck together" from a lower plane of existence, representing doubled magnetic monopoles on that plane.
3) A mathematical formula is proposed to describe the number of fundamental particles ("koilon quanta") that make up electrons and other fundamental particles on different planes of existence.
Universe and the Solar System (Lesson 1).pptxJoenelRubino3
SHS Earth and Life Grade 11 Lesson 1. This lesson discusses the compos of the universe, the origin of the universe, different hypotheses of the origin of the universe
The Big Bang model describes the origin and evolution of our universe. It postulates that approximately 13.8 billion years ago, the entire observable universe was only a few millimeters in size and extremely hot and dense. The universe has been expanding and cooling ever since. Evidence for the Big Bang includes the expansion of the universe, the cosmic microwave background radiation, and the relative abundance of light elements like hydrogen and helium.
The Big Bang model describes the origin and evolution of our universe. It postulates that approximately 13.8 billion years ago, the entire observable universe was only a few millimeters in size and extremely hot and dense. Since then, the universe has been expanding and cooling. Evidence for the Big Bang includes the expansion of the universe, the cosmic microwave background radiation, and the relative abundance of light elements like hydrogen and helium. The Doppler effect and redshift help astronomers measure the speeds at which distant galaxies are receding from Earth, leading to the discovery that the expansion of the universe is accelerating. Dark matter and dark energy are hypothesized to explain discrepancies in measurements of the density and expansion rate of the universe.
ILOA Galaxy Forum Europe 2013 - dark matter in galaxies - dr benoit famaeyILOAHawaii
This document discusses the history and current state of the dark matter problem in astrophysics. It summarizes that observations in the 1930s and 1970s found that galaxies and galaxy clusters contain far more mass than can be accounted for by the visible stars and gas, with the mass increasing farther from galaxy centers. This is known as the "missing mass" problem. The current favored model, called Lambda Cold Dark Matter (Lambda CDM), posits that dark matter makes up 85% of all matter in the universe and helps explain large scale structure formation. However, the nature of dark matter remains unknown, and alternative gravitational theories have not been ruled out. Future experiments aim to directly detect dark matter particles or test gravitational theories on larger scales
Stars are formed from clouds of gas and dust called nebulae. As stars age and evolve, they progress through different stages - from stars to red giants or dwarfs to supernovae. The most massive stars may collapse into neutron stars or black holes. Black holes are objects so dense that not even light can escape their powerful gravitational pull. Material near a black hole forms a swirling accretion disk and is ejected at nearly light speed in powerful jets. Advancing technology is improving our understanding of stellar evolution and black hole formation.
This document provides an introduction to black holes from both a theoretical physics and astronomical perspective. It describes how black holes form from the gravitational collapse of massive stars and discusses their key properties, including their event horizons and singularities based on solutions to Einstein's equations. The document uses diagrams of light cones to visualize how black holes distort spacetime and discusses how time appears frozen for distant observers watching objects cross the event horizon. It aims to build intuition for some basic yet profound concepts regarding black holes.
Recent advances in the study of black holes include:
1. The first image of a black hole was captured in 2019 using the Event Horizon Telescope, showing the shadow of the supermassive black hole at the center of the Messier 87 galaxy.
2. Gravitational waves detected in 2015 by the LIGO observatory provided direct evidence of black holes from the merger of two stellar-mass black holes.
3. Observations of stars orbiting Sagittarius A* provided evidence of a supermassive black hole at the center of the Milky Way galaxy.
4. X-ray binaries, where matter falls from a donor star onto a compact object like a neutron star or black hole
New microsoft office power point presentationSalman Ahmad
A black hole is formed when a massive star collapses under its own gravity at the end of its life. It creates a region of space where the gravitational pull is so strong that nothing, not even light, can escape. Black holes were first theorized in the 18th century and their existence was predicted by Einstein's theory of general relativity. They have been observed through their effects on nearby stars and gas and the emission of x-rays. Black holes come in different sizes, from stellar black holes formed by collapsed stars to supermassive black holes millions of times the sun's mass at the center of galaxies.
1) The document provides a summary of a course on high-energy astrophysics that the author took. It discusses various topics covered in the course including accretion disks, pulsars, black holes, supernovae, and more.
2) The author argues that high-energy astrophysics is important for understanding the universe and requests that the provost offer a similar course at their university.
3) Key concepts in high-energy astrophysics discussed include accretion and its relation to luminosity, binary star systems, properties of neutron stars and black holes, and x-ray emissions from astrophysical phenomena like supernovae.
1) Neutron stars are the remnants of collapsed stars that have a mass greater than 1.4 solar masses. They form during type II supernovae following the collapse of massive red supergiant stars.
2) Pulsars are a type of neutron star that emit beams of electromagnetic radiation and appear to pulse due to their rotation. They were first discovered by Jocelyn Bell in 1967 through detecting their regular radio pulses.
3) Gravitational waves are ripples in spacetime caused by accelerating massive objects like neutron stars and black holes. Detecting gravitational waves from binary neutron star systems could provide insights into energetic cosmic events and test Einstein's theory of general relativity.
The document discusses the evolution and deaths of stars. It describes how low-mass stars like the Sun will evolve into red giants and planetary nebulae over billions of years. More massive stars may explode as supernovae, producing neutron stars or black holes and spreading heavy elements throughout space. Neutron stars can be observed as pulsars that emit beams of radiation. The origins of elements on Earth and phenomena like cosmic rays and pulsars are also examined.
Astronomy - State of the Art - GalaxiesChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the properties of galaxies are discussed, including supermassive black holes and dark matter.
Using radio observations, astronomers may be able to detect and characterize exoplanets by observing radio emissions from their magnetospheres. Planetary magnetospheres are theorized to produce bursts of decametric radiation through interactions with the solar wind that distort magnetic field lines and accelerate charged particles. While difficult to detect over a host star's emissions, observation of planetary radio signals could provide information on properties like the presence, size, and composition of a magnetosphere, as well as any orbiting satellites. The LOFAR radio telescope may enable the first detections of exoplanetary radio emissions within the next decade.
Space weather and potential impact on earth’s climate dec 19 10 v2Poramate Minsiri
This document discusses space weather and its potential impacts on Earth's climate and seismic activity. It provides an overview of the solar system and its dynamics, as well as how our solar system interacts with the Milky Way galaxy and larger universe. Recent observations have found evidence that the outer boundaries of our solar system are being compressed as we pass through Galactic clouds, allowing more cosmic rays and energetic particles to enter the inner solar system. This could affect Earth's climate and increase seismic activity. The document also discusses changes observed on other planets in our solar system, such as the growth of dark spots on Pluto and changes in cloud cover on Mars.
There are several types of ultra-compact binary star systems that orbit each other with periods of less than an hour. These systems emit gravitational waves due to their strong gravitational fields changing over time. The Laser Interferometer Space Antenna (LISA) mission aims to detect these gravitational waves. While current ground-based detectors cannot detect the waves from ultra-compact binaries, LISA may be able to do so due to observing from space. The document provides data on four example binary systems and calculates their orbital decay rates and the strain of the gravitational waves emitted.
1) Asteroids are rocky bodies too small to be called planets that orbit the sun, with many located in the asteroid belt between Mars and Jupiter. Some asteroids pass close to Earth and are called Near-Earth Objects.
2) The sun is a hot ball of gas at the center of the solar system that provides the energy and heat for life on Earth. It is one of billions of stars in the Milky Way galaxy.
3) Supernovas occur when massive stars explode at the end of their life cycles, around once every 50 years in a galaxy the size of the Milky Way. Less massive stars like the sun will swell into red giants before collapsing into white dwarfs instead of exploding.
3C 273 was one of the first quasars discovered in 1963. It remains one of the brightest and best studied quasars. It is located approximately 3 billion light years from Earth and radiates energy equivalent to 1014 times the luminosity of the Sun. 3C 273 plays a key role in understanding the nature of quasars as powered by accretion disks around supermassive black holes. It continues to be intensely observed across the electromagnetic spectrum to better understand the physics occurring in these energetic and distant cosmic objects.
Big Bang Theory & Other Recent Sciences || 2014 - Dr. Mahbub Khaniqra tube
RECENT SCIENCES
Big Bang, Dark Matter, Dark Energy, Black Hole, Neutrino, God Particle, Higgs Field, Graviton, Expansion of Universe, and Search for Life elsewhere in the Cosmos
1) The document hypothesizes that dark matter images were accidentally recorded by cameras on the TSS-1R satellite during a 1996 NASA mission mishap. Disk-like images seen moving beyond the receding satellite are proposed to be evidence of dark matter.
2) It further conjectures that these disk images each represent two single-notch 2D disks "stuck together" from a lower plane of existence, representing doubled magnetic monopoles on that plane.
3) A mathematical formula is proposed to describe the number of fundamental particles ("koilon quanta") that make up electrons and other fundamental particles on different planes of existence.
Universe and the Solar System (Lesson 1).pptxJoenelRubino3
SHS Earth and Life Grade 11 Lesson 1. This lesson discusses the compos of the universe, the origin of the universe, different hypotheses of the origin of the universe
The Big Bang model describes the origin and evolution of our universe. It postulates that approximately 13.8 billion years ago, the entire observable universe was only a few millimeters in size and extremely hot and dense. The universe has been expanding and cooling ever since. Evidence for the Big Bang includes the expansion of the universe, the cosmic microwave background radiation, and the relative abundance of light elements like hydrogen and helium.
The Big Bang model describes the origin and evolution of our universe. It postulates that approximately 13.8 billion years ago, the entire observable universe was only a few millimeters in size and extremely hot and dense. Since then, the universe has been expanding and cooling. Evidence for the Big Bang includes the expansion of the universe, the cosmic microwave background radiation, and the relative abundance of light elements like hydrogen and helium. The Doppler effect and redshift help astronomers measure the speeds at which distant galaxies are receding from Earth, leading to the discovery that the expansion of the universe is accelerating. Dark matter and dark energy are hypothesized to explain discrepancies in measurements of the density and expansion rate of the universe.
ILOA Galaxy Forum Europe 2013 - dark matter in galaxies - dr benoit famaeyILOAHawaii
This document discusses the history and current state of the dark matter problem in astrophysics. It summarizes that observations in the 1930s and 1970s found that galaxies and galaxy clusters contain far more mass than can be accounted for by the visible stars and gas, with the mass increasing farther from galaxy centers. This is known as the "missing mass" problem. The current favored model, called Lambda Cold Dark Matter (Lambda CDM), posits that dark matter makes up 85% of all matter in the universe and helps explain large scale structure formation. However, the nature of dark matter remains unknown, and alternative gravitational theories have not been ruled out. Future experiments aim to directly detect dark matter particles or test gravitational theories on larger scales
Stars are formed from clouds of gas and dust called nebulae. As stars age and evolve, they progress through different stages - from stars to red giants or dwarfs to supernovae. The most massive stars may collapse into neutron stars or black holes. Black holes are objects so dense that not even light can escape their powerful gravitational pull. Material near a black hole forms a swirling accretion disk and is ejected at nearly light speed in powerful jets. Advancing technology is improving our understanding of stellar evolution and black hole formation.
This document provides an introduction to black holes from both a theoretical physics and astronomical perspective. It describes how black holes form from the gravitational collapse of massive stars and discusses their key properties, including their event horizons and singularities based on solutions to Einstein's equations. The document uses diagrams of light cones to visualize how black holes distort spacetime and discusses how time appears frozen for distant observers watching objects cross the event horizon. It aims to build intuition for some basic yet profound concepts regarding black holes.
Recent advances in the study of black holes include:
1. The first image of a black hole was captured in 2019 using the Event Horizon Telescope, showing the shadow of the supermassive black hole at the center of the Messier 87 galaxy.
2. Gravitational waves detected in 2015 by the LIGO observatory provided direct evidence of black holes from the merger of two stellar-mass black holes.
3. Observations of stars orbiting Sagittarius A* provided evidence of a supermassive black hole at the center of the Milky Way galaxy.
4. X-ray binaries, where matter falls from a donor star onto a compact object like a neutron star or black hole
New microsoft office power point presentationSalman Ahmad
A black hole is formed when a massive star collapses under its own gravity at the end of its life. It creates a region of space where the gravitational pull is so strong that nothing, not even light, can escape. Black holes were first theorized in the 18th century and their existence was predicted by Einstein's theory of general relativity. They have been observed through their effects on nearby stars and gas and the emission of x-rays. Black holes come in different sizes, from stellar black holes formed by collapsed stars to supermassive black holes millions of times the sun's mass at the center of galaxies.
1) The document provides a summary of a course on high-energy astrophysics that the author took. It discusses various topics covered in the course including accretion disks, pulsars, black holes, supernovae, and more.
2) The author argues that high-energy astrophysics is important for understanding the universe and requests that the provost offer a similar course at their university.
3) Key concepts in high-energy astrophysics discussed include accretion and its relation to luminosity, binary star systems, properties of neutron stars and black holes, and x-ray emissions from astrophysical phenomena like supernovae.
International Upcycling Research Network advisory board meeting 4Kyungeun Sung
Slides used for the International Upcycling Research Network advisory board 4 (last one). The project is based at De Montfort University in Leicester, UK, and funded by the Arts and Humanities Research Council.
Best Digital Marketing Strategy Build Your Online Presence 2024.pptxpavankumarpayexelsol
This presentation provides a comprehensive guide to the best digital marketing strategies for 2024, focusing on enhancing your online presence. Key topics include understanding and targeting your audience, building a user-friendly and mobile-responsive website, leveraging the power of social media platforms, optimizing content for search engines, and using email marketing to foster direct engagement. By adopting these strategies, you can increase brand visibility, drive traffic, generate leads, and ultimately boost sales, ensuring your business thrives in the competitive digital landscape.
1. Neutron Stars
and
Black Holes
Why do we expect neutron stars exist?
How do we know neutron stars exist?
What theoretical arguments predict the existence of black
holes?
What evidence is there that black holes indeed exist?
3. Neutron Stars:
If we pack electrons
close enough together
white dwarf
(electron degenerate)
If we pack neutrons
close enough together
neutron star
(neutron degenerate)
Q: Recall the Chandrasekhar limit (1.4 solar
masses), what happens if the collapsing core
is greater than this?
4. Properties of neutron stars:
~ 10 km in radius
Density ~1014g/cm3
Between 1.4 and 3 Msun
Q: What happens when a
NS becomes more
massive than 3 Msun?
Spin rapidly
Hot
Strong magnetic field
Pressure becomes so high that
electrons and protons combine
to form stable neutrons
throughout the object.
Q: Why would we expect neutron
stars to spin rapidly, be hot, and
have strong magnetic fields?
6. Pulsars:
1967 Jocelyn Bell noticed
pulses which repeated
regularly in the sight line of a
distant galaxy first pulsar
that was detected.
Periods range from ~ 0.030
to 3.75 seconds
Gradually slow down
Pulses last ~ 0.001 s
This places an upper
limit on the size of the
object emitting the
pulse…
Suppose it was a white dwarf of 12,000 km
diameter emitting the pulse…
Since the near side is 12,000 km closer than
the far side, the light from the near side would
arrive ~0.04 s sooner than the light from the
far side…
The pulse would be smeared out over a
longer interval.
An object cannot change its brightness in an interval
shorter than the time it takes light to travel its diameter.
For a 0.001 s pulse interval, the diameter must be smaller than
300 km.
/
t d c
7. The link between neutron stars
and pulsars:
In 1968, astronomers discovered
a pulsar in the Crab nebula.
The Crab
Pulsar is
roughly 25
km (~16 mi.)
in diameter
and rotates
~ 30
times/second!
It’s slowing in its
rotation by 38
nanoseconds/day
due to energy
loss by the pulsar
wind.
8.
9. Theoretical model of a pulsar:
Pulsars do not pulse, but
rather emit beams of
radiation that sweep around
the sky as the neutron star
rotates
Strong magnetic and electric
fields are likely the cause of
the intense beams of
radiation
Note that we only
can see the
pulsars whose
beams sweep
over Earth.
10. The evolution of pulsars:
Q: the Crab pulsar is
slowing down in its
rotation by 38
nanoseconds/day…
why?
Pulsars lose energy
as they emit beams of
radiation and the
pulsar wind (high-
speed atomic
particles)
Q: Where, ultimately,
does this energy come
from?
The energy of
rotation! (That’s why
they slow down)
11. pulsar B1508+55 path
1000km/s
Q: What could explain these strange
motions of pulsars that are observed?
Roaming pulsars: Some pulsars appear
to be moving at a high speed through
space…
12. Compact Objects with Disks and Jets – x-rays:
Black holes and neutron stars can
be part of a binary system.
=> Strong X-ray source!
Matter gets pulled off from
the companion star, forming
an accretion disk.
Heats up to a few million K.
Binary pulsars allow us to measure the mass
and all the other good things we get from
binaries…
Looking for x-ray sources is one way to
detect neutron stars (and black holes…).
13. Binary pulsars:
In 1974, Taylor and Hulse detected
the first binary pulsar
(PSR1913+16);
The pulses were changing, growing
longer, and then shorter over a
period of 7.75 hours
From Doppler shifts, the orbital
velocities and masses were
calculated…
and it turned out that this system
was two neutron stars orbiting each
other with a separation of roughly
the radius of our sun!
PSR1913+16 held another surprise…
In 1916 Einstein predicted that a rapid
change in a gravitational field should
spread out like waves (gravitational
radiation)
Taylor and Hulse were able to show
that the orbital period was decreasing
because the stars were spiraling
toward each other.
They won the Nobel prize in 1993.
14. Neutron Stars in Binary Systems: X-ray binaries – Her X-1:
Her X-1
2 Msun (F-type) star
Accretion disk material heats to several million K
=> X-ray emission
Star eclipses the
neutron star and
accretion disk every
1.7 days hiding the
x-ray pulses for a
few hours
Orbital period =
1.7 days
Pulses every
1.2 seconds
15. Masses of pulsars:
From Doppler shifts, astronomers
have estimated the masses of
dozens of binary pulsars.
Typical masses are ~ 1.35 solar
masses.
Q: If the core must be at least 1.4
solar masses to form a NS, then how
could the typical mass of a NS be
1.35?
A: A NS of slightly less than 1.4 solar
masses can exist if the NS loses
mass. Also, a 1.4 solar mass WD
produces a 1.2 solar mass NS.
Some of the mass is converted into
binding energy.
The gravitational fields near neutron
stars are so strong, that a
marshmallow dropped onto a
neutron star from a distance of 1AU
would release the equivalent energy
of a 3 Mt nuclear bomb! (~231
Hiroshima-sized bombs!)
16. X-ray bursters:
Matter flows onto the NS where it
accumulates until it becomes hot and
dense enough to ignite
The result is a burst of x-rays
“x-ray burster”
Notice the similarity between this and
the mechanism which generates
novae….
17. The X-Ray Burster 4U 1820-30
Optical Ultraviolet
This is a neutron star orbiting a white
dwarf
The period is only 11 minutes!
The separation is only about a
third of the Earth/moon distance!
This is possibly the result of a collision
of a neutron star and a giant…
the NS then went into orbit inside the
giant!
18. The fastest pulsars:
Q: Would you expect a pulsar that
pulses rapidly to be young or old?
Due to the gradual slowing of the
rotation, one would expect young
pulsars to blink rapidly and old
pulsars to blink slowly, but…
A few that blink the fastest may be
quite old….
One of the fastest (PSR1937+21)
pulses 642 times a second!
The energy contained in the rotation
of this pulsar is comparable to the
total energy of a supernovae
explosion!
Q: How could this be?
To explain this, it appears that this
pulsar was sped up by accreting
matter from a binary companion.
The fastest pulsars go by the name
“millisecond pulsars.”
Why are they so fast?
What happens to them when they
rotate so fast?
Since the pulse period of the pulsar is
the rotation period, these fast pulsars
are probably flattened like pancakes!
Take PSR1937+21;
Assume it is 10 km in radius…
Spinning at 642 times a second, the
period is 0.0016 seconds and the
equatorial velocity is about 40,000
km/s!
2 /
r t
19. Pulsar Planets:
Small Doppler shifts were observed in the
spectra of PSR1257+12
Analysis revealed that this pulsar was orbited
by at least two planets with masses roughly
4.3 and 3.9 Earth masses!
Further analysis revealed a third planet with a
mass of about that of our moon!
And there is evidence that a fourth planet
about 100 Earth masses orbits this pulsar with
a much larger separation.
Q: How can a NS have planets?!?
(Recall that NS are created by supernovae,
and a giant star about to explode would
envelop any planets within an AU or two…)
As a planet orbits around a
pulsar, the planet causes it to
wobble around, resulting in
slight changes of the
observed pulsar period.
These planets are probably the remains
of a stellar companion that was
devoured by the NS.
20. Black Holes
Just like white dwarfs (Chandrasekhar limit: 1.4 Msun),
there is a mass limit for neutron stars:
Neutron stars can not exist
with masses > 3 Msun
We know of no mechanism to halt the collapse
of a compact object with > 3 Msun.
It will collapse into a single point – a singularity:
=> A black hole!
21. Escape Velocity:
Escape velocity depends
on two things;
1. Mass
2. Distance from CoM
vesc
Gravitational force decreases with
distance (~ 1/r2)
Starting out high above the surface
lower escape velocity.
vesc
vesc
If you could compress Earth to a smaller
radius => higher escape velocity from the
surface.
Velocity needed to escape Earth’s
gravity from the surface: ≈ 11.6 km/s
(~25,000 mph).
22. The Schwarzschild Radius:
There is a limiting radius where the
escape velocity reaches the speed of
light, c:
Vesc = c
Rs =
2GM
____
c2
Rs is called the Schwarzschild radius.
G = gravitational constant
M = mass
23. Schwarzschild Radius and Event Horizon:
No object can travel faster than
the speed of light
We have no way of finding
out what’s happening inside
the Schwarzschild radius.
=> nothing (not even light) can
escape from inside the
Schwarzschild radius
“Event horizon”
24.
25. “Black Holes Have No Hair”
Matter forming a black hole is losing almost all
of its properties.
black holes are completely determined by
3 quantities:
mass
angular momentum
(electric charge)
26. General Relativity Effects Near Black Holes:
An astronaut descending down
towards the event horizon of the black
hole will be stretched vertically (tidal
effects) and squeezed laterally.
27. General Relativity Effects Near Black Holes (II):
2 2 1 2
' (1 )
t t c
Time dilation
Event horizon
Clocks starting at 12:00 at
each point.
After 3 hours (for an
observer far away from
the black hole): Clocks closer to the black hole
run more slowly.
Time dilation becomes
infinite at the event horizon.
In SR:
2 1 2
' (1 2 )
t t c
In GR:
28. General Relativity Effects Near Black Holes (III):
gravitational redshift
Event horizon
All wavelengths of emissions from
near the event horizon are stretched
(redshifted).
Frequencies are lowered.
29. Observing Black Holes:
No light can escape a black hole
=> Black holes can not be observed directly.
We can estimate its mass
from the orbital period and
radial velocity.
Mass > 3 Msun
=> Black hole!
2 3
2
4
total
a
M
G P
But… if an invisible compact object is part of a binary…
32. Jets of Energy from Compact Objects:
Some X-ray binaries show
jets perpendicular to the
accretion disk.
These bipolar flows are
formed the same way as
they do for protostars.
(Bipolar flow - angular
momentum hot accretion
disk high-energy photons
emitted shot out via
thermal & magnetic
processes.
Your impression of a black
hole might suggest that it’s
impossible to get energy out
of such an object.
33. Opposing jets of gas are
streaming away from a
supermassive black hole at
Centaurus A´s galactic nucleus
- remnants of a giant explosion.
34. Model of the X-Ray Binary SS 433:
Optical spectrum shows spectral lines
from material in the jet.
Two sets of lines: one
blue-shifted, one red-
shifted to near ¼ c
(it’s receding and
approaching!)
Lines shift back and forth
across each other every
164 days due to jet
precession
SS 433 is most likely a
black hole!
35. In 1963, a nuclear test ban treaty was signed – nuclear weapons tests
were off limits…
In 1968, the U.S. had satellites designed to detect gamma rays – signs of
a nuclear detonation…
Those satellites started detecting bursts of gamma rays at a rate of about
one burst a day…
That data became declassified in 1973.
The bursts usually lasted only a matter of seconds…
They came from all directions of the sky and not from any particular
region…
They occur without warning…
And they have more power than the most violent supernovae
explosions….
36. Gamma-Ray Bursts (GRBs):
GRB of May 10, 1999:
1 day after the GRB
2 days after the GRB
Some of these GRBs repeat – known as “soft gamma-ray repeaters,”
“soft” = low energy gamma rays.
We suspect that these originate from neutron stars with really strong
magnetic fields (“magnetars”).
When shifts in the magnetic field breaks through the crust of a magnetar,
bursts of gamma rays are emitted.
On August 27, 1998, one of these ionized Earth’s atmosphere and
disrupted radio communications worldwide.
37. Gamma-Ray Bursts (GRBs) II:
Possible origins:
Could be the result of the merger of two neutron
stars (recall the binary pulsar PSR1913+16 detected by
Taylor and Hulse.)
and/or from the collapse of really massive stars
(>25 solar masses) - “hypernovae”
March 29, 2003 GRB in
Leo…
Left behind a spectrum
which resembled that of
a SN
Hypernovae are
indeed responsible for
some GRBs
But the NS merger is not
ruled out….
38. GRBs III:
If a GRB occurred only 1,600 ly from Earth, we would be showered with the
radiation equivalent to a 10,000 Mt nuclear blast!
Possibly every few hundred million years one could occur near enough to Earth
for us to be affected.
Possibly one of these caused one of the mass extinctions that show up in the
fossil record…
Q: How could something which seems so rare as a neutron star merger, be so
common that we detect at least one of these GRBs every day?