Stars and Stellar Final
What is the ultimate fate of a binary star system? (Type 1a supernova)
- super nova can occur if a a white dwarf in a binary star system gain mass from its companion.. -because the gas is degenerate there is no thermostat to regulate the fusion, and the entire white dwarf fuses suddenly in a violent explosion.. white dwarf is destroyed. But there are no hydrogen lines in the spectrum of the supernova
Giant stars
-as stars age, they evolve away from the main sequence to become red giants or supergiants
Lower mass stars
-the lower mass a star is the longer it lives While fusing hydrogren in their cores both hydrogen and helium rise through the star and fall back down Red dwarfs can last a trillion years before they die
the diameter of the sun can fit roughly
109 earths
What is the planetary nebula and what is it made of?
A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. They are in fact unrelated to planets; the name originates from a supposed similarity in appearance to giant planets.
death process of a Red Dwarf star
A red dwarf dies when it burns all of its fuel, which will then be nearly pure helium and fusion will cease. finally it will be a cold black dead star
Understand the death process of the medium mass stars like our sun
As a medium mass star nears the end of its life, it runs out of hydrogen which it has been fusing onto helium in its core for its whole life. The helium then fuses into lithium, beryllium, boron, etc. This process ends at iron where no energy is produced. All the elements in the core of the star build to a giant ball of iron, while the rest of the gases expand out in a planetary nebula.
. How does theory predict the existence of Black Holes?
As for white dwarfs (Chandrasekhar limit:1.4 M¤), there is a mass limit for neutron stars! Neutron stars can not exists with M > 3.0 M¤ . If M > 3.0 M¤ the pressure becomes so high that we know of no mechanism to halt the collapse of the compact object The compact object will collapse until the escape velocity of any object from its surface exceeds the speed of light. This is a black hole!
What will you find at the center of planetary nebula?
At the center of a planetary nebula, the glowing, left-over central part of the star from which it came can usually still be seen.
What is a pulsar and how were they discovered?
Bell discovered the first pulsar in 1967. ... Bell and Hewish had no idea what the signals were that they detected, so they were dubbed little green men (LGM) as a reference to extraterrestrial life. Soon after, Thomas Gold showed that a spinning neutron star could make the pulses they observed.
The temperature of the corona is
Hotter than the photosphere
What are some strange effects near black holes?
If you happened to fly near a black hole, its extreme gravitational pull would increasingly slow down time and warp space. You'd be tugged ever closer, gradually joining an accretion disk of orbiting space material (stars, gases, dust, planets) spiraling inward toward the event horizon or "point of no return." Once you crossed this boundary, gravity would overcome all chances of escape and you'd be super-stretched, or "spaghettified" as you plunged toward the singularity at the black hole's center also nearing black holes effects space an time, the closer you get to the event horizon time slows and at the event horizon time stops.
What conditions are required for electrons and protons to combine to form stable neutrons?
In a neutron star gravity has overcome electron degeneracy pressure allowing the protons and electrons to combine into neutrons
The process of removing an electron from a stable nucleus is known as
Ionization
How does a binary star system transfer mass?
Matter moves away from one star and passes through the point of equal gravity. It is then captured by the other star
Why are neutron stars hard to observe?
Neutron stars are very hard to find since they are so small and not very bright. The easiest way to find them is when they emit beams of radiation as pulsars
Gamma-Ray Bursts
Object that radiates tremendous amounts of energy in the form of gamma rays, possibly due to the collision and merger of two neutron stars initially in orbit around one another. Bursts come in two varieties: Short and Long
death of lower mass main sequence star
Red dwarfs are stars that have very little weight to support (M < 0.5 M) temperature is low so the star will consume hydrogen slowly when star uses up all the hydrogen through convection the star does not get hot enough to ignite helium
Understand why a Red Dwarf star does not become a Giant star
Red dwarfs will not pass through a red giant phase in their evolution. Because convection occurs through the entire star, hydrogen is constantly recirculated from the outer regions to the core.
Granulation is caused by
Rising and sinking gases (convection) below the photosphere
What is a star cluster and explain why they are important to test our theories on stellar evolution
Star clusters are very large groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds to millions of old stars which are gravitationally bound
What does the Chandrasekhar limit tell us about the mass of White Dwarfs?
The Chandrasekhar Limit is now accepted to be approximately 1.4 times the mass of the sun; any white dwarf with less than this mass will stay a white dwarf forever, while a star that exceeds this mass is destined to end its life in that most violent of explosions: a supernova.
What is the Chandrasekhar limit?
The Chandrasekhar limit is the maximum mass of a stable white dwarf star
Sunspots are known to be magnetic phenomena because
The Zeeman effect is observed in sunspots
Differential rotation of the sun is
The equatorial regions of the sun rotating move more rapidly than polar regions
What are the properties of a neutron star?
They are extremely dense, and they are very massive(high mass), they spin rapidly and have strong magnetic fields A typical neutron star has a surface gravity 100 billion times stronger than earth
sunspots often appear in pairs
True
. What Happens if an evolving star is in a binary star system?
Two stars orbiting each other control two regions of space called Roche lobes. ... Mass is transferred from an evolving star through an accretion disk around the receiving star.
How does theory predict the existence of Neutron stars?
When a supernova explodes, the core collapses to very small size. Theory predicts that protons and electrons will combine to form a degenerate neutron gas. ... A neutron star is supported by the pressure of the degenerate gas of neutrons.
How will stars similar to our sun die?
When it dies it will leave behind a white dwarf in the center of an expanding cloud of gas called a planetary nebula. The name white dwarf comes from the fact that these stellar corpses are A star with a mass like the Sun, on the other hand, can continue fusing hydrogen for about 10 billion years.Jul 15, 2014
What happens to a star when it uses up the last of the hydrogen in its core?
When the core runs out of hydrogen fuel, it will contract under the weight of gravity. ... The upper layers will expand and eject material that will collect around the dying star to form a planetary nebula. Finally, the core will cool into a white dwarf and then eventually into a black dwarf.
What is a neurton star?
a celestial object of very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons. Neutron stars are thought to form by the gravitational collapse of the remnant of a massive star after a supernova explosion, provided that the star is insufficiently massive to produce a black hole.
What is a white dwarf?
a small very dense star that is typically the size of a planet. A white dwarf is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula
The corona and chromosphere of the sun are believed to be heated by
high energy particles being accelerated by the sun's magnetic field.
The to most abundant elements in the sun are
hydrogen and helium
What is escape velocity?
in brief, its the velocity at which you need to fling something off the surface of an object to get it to escape
Why are Pulsar Systems important?
locate extra solar planets. astronomers can use pulsars for unique "experiments" at the frontiers of modern physics. ... Pulsars are at the forefront of research on gravity
What is the Chandrasekhar limit?
mass limit to the total mass of a white dwarf, beyond which the electron degeneracy pressure will be overcome and the core will collapse
What are some properties of a pulsar (Rotation, magnetic field strength)
pulsars are neutron stars , their rapid rotation coupled with their incredibly strong magnetic field launch twin beams of energy away from the star like the beams from a lighthouse, the beams sweep around as the star rotates and from earth we see this as a pulse
The bending of light as it passes through a lens is known as
refraction
Understand the death process of stars with mass 4 Solar mass units
shrinks to neutron star. Supernova happens when a neutron star is created. Neutrons prevent further collapse. The size of a neutron star is about that of a large city.
At the beginning of the sunspot cycle
sunspots begin to appear at higher latitudes
Describe the features of a Black Hole (Singularity and Event Horizon)?
the event horizon is where the escape speed exceeds the speed of light: you'd have to be going faster than light (which is impossible for any bit of matter) to escape the black hole's gravity Inside the event horizon is where physics goes crazy. ... A singularity is what all the matter in a black hole gets crushed into.
. How do massive stars die
the more massive the star, the faster it burns up its fuel supply, and the shorter its life. The most massive stars can burn out and explode in a supernova after only a few million years of fusion.
Most of the visible light we see from the sun originates from
the photosphere
What is Schwarzschild Radius?
the radius at which the escape speed from the black hole equals the speed of light There is a limiting radius where the escape velocity reached the speed of light c.
Sunspots are dark because
the strong magnetic field inhibits the currents of hot gas rising from below.
What is a black hole?
the ultimate end state for the core of a high mass star, whatever happens in a black hole stays in a black hole That region of space, that surface around the black hole where the escape velocity is the speed of light is called THE EVENT HORIZON
How does a Binary System evolve?
these stars can evolve independently of each other if their orbits are large - in some binary systems, the less massive star has become a giant, while the more massive stars is still on the main sequence.
How can astronomers be sure that black holes really exists
we know that black holes exist because even though they don't emit light, they do have lots of gravity. Thanks to laws of physics discovered by Newton, we can find out exactly how much gravity an object exerts by measuring how fast something else orbits around it. In the case of a black hole, finding out how quickly nearby stars orbit around it can tell us exactly how much mass it has.
Understand theory behind Binary Pulsar systems
when another normal star orbits them if they are close enough together the neutron star can rip material off the other star and feed on it
Where are white Dwarfs found on the HR diagram?
white dwarf stars (luminosity class D) are the final evolutionary stage of low to intermediate mass stars, and are found in the bottom left of the HR diagram.
Where are white Dwarfs found on the HR diagram?
white dwarf stars (luminosity class D) are the final evolutionary stage of low to intermediate mass stars, and are found in the bottom left of the HR diagram. These stars are very hot but have low luminosities due to their small size.
