Ast 109 Lesson 20

What is the remnant of a mass range 3 star?

A carbon white dwarf

So, how long does a supernova take to explode?

A few million years for the star to die, less than a quarter of a second for its core to collapse, a few hours for the shockwave to reach the surface of the star, a few months to brighten, and then just few years to fade away.

What star is considered a supergiant?

A star classed as a supergiant may have a diameter several hundred times that of the Sun and a luminosity nearly 1,000,000 times as great. Supergiants are tenuous stars, and their lifetimes are probably only a few million years, extremely short on the scale of stellar evolution.

Helium Flash

A sudden and burst from the core of the Red giant heating to 10^8 degrees K, causing the immediate new source of fusion of He -> C and O.

What is a supernova?

A supernova is a large explosion that takes place at the end of a star's life cycle. ... A supernova is the explosion of a star. It is the largest explosion that takes place in space.

Novas

A white dwarf star that suddenly appears in the sky from an internal explosion: days-weeks that suddenly gets brighter being previous faintness or even invisible tonus. -The white dwarf gets 5-15 magnitudes brighter: 100 times brighter -1 million times brighter. -Cause: Some white dwarfs have companion stars, and if the companion starts to become a giant and expand, the white dwarf accretes the companion's energy and mass. -A blanket of new hydrogen appears which heats under the surface holding the explosion and starts a sudden fusion, which EXPLODES the surface of the star as a result of the pression.

Is Deneb a supergiant star?

Deneb is a blue-white supergiant star of spectral type A2 la. Since Deneb is very far away, its exact luminosity is hard to calculate but estimates suggest that it is between 55.000 to 196.000 times brighter than our sun. Deneb is so bright, that it actually rivals Rigel as the most luminous first magnitude star.Jan 30, 2020

Hubble Telescope

Detects the presence of White Dwarf stars even though they are single in the space.

Why is the supergiant star expanding?

Eventually, as stars age, they evolve away from the main sequence to become red giants or supergiants. The core of a red giant is contracting, but the outer layers are expanding as a result of hydrogen fusion in a shell outside the core. The star gets larger, redder, and more luminous as it expands and cools.

What is the difference between a giant star and a supergiant star?

Giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Whereas Supergiants have radii between 30 and 1,000 solar radii and luminosities between 30,000 and 100,000 times that of the Sun.

Does a Supernova create a star?

In the massive star case, the core of a massive star may undergo sudden collapse, releasing gravitational potential energy as a supernova. ... Supernovae are a major source of elements in the interstellar medium from oxygen to rubidium. The expanding shock waves of supernovae can trigger the formation of new stars.

What is a nova star?

Nova, plural Novas, orNovae, any of a class of exploding stars whose luminosity temporarily increases from several thousand to as much as 100,000 times its normal level.

Is supernova a dying star?

One type of supernova is caused by the "last hurrah" of a dying massive star. This happens when a star at least five times the mass of our sun goes out with a fantastic bang! Massive stars burn huge amounts of nuclear fuel at their cores, or centers. This produces tons of energy, so the center gets very hot.

Will our sun go supernova?

Our sun, for example, doesn't have enough mass to explode as a supernova (though the news for Earth still isn't good, because once the sun runs out of its nuclear fuel, perhaps in a couple billion years, it will swell into a red giant that will likely vaporize our world, before gradually cooling into a white dwarf).

Example of Mass Range 3 star?

Sun, Alpha Centauri A ~ G2V Arcturus ~ K2III D= 26D M= 4M III is luminosity. K2 is cool temperature

Why does the surface of a giant star expand while its core contracts?

The core fuses more, and dumps more energy/pressure into the outer parts of the star. Eventually, as stars age, they evolve away from the main sequence to become red giants or supergiants. The core of a red giant is contracting, but the outer layers are expanding as a result of hydrogen fusion in a shell outside the core. The star gets larger, redder, and more luminous as it expands and cools.

After 10^10 years some white dwarfs become _____ ______, or a cosmic corpse. after 10 billion years

black dwarfs

Range Three

-.4 < M* < 8 MSun -Includes types K, G, F, and A Main Sequence stars -All stars in this range burn H -> He -Examples: Sun, alpha Centauri A, Arcturus

H Burning Stops After:

-10^8 years for 8 MSun stars -10^11 years for .4 MSun stars -10^10 years for our Sun

Mass of a White Dwarf Chandrasekhar Limit

-A carbon white dwarf cannot be smaller than M* = 1.4 MSun. no mas de 140% de la masa del sol

Range Three Giant Phase Evolution

-Main Sequence stars become red giants when they run out of H to burn in the core. -The core collapses from the lack of internal outward pressure from fusion: collapse raises core temperature -Outer H shell collapses into the collapsed core and has a sudden burst of fusion that causes the star to expand. -The core is collapsing and heating and the outer star is expanding and cooling. -Star becomes more luminous and RED because of the expanse of surface area and energy.

Planetary Nebula

-One result of the instability of a red giant range three star -The shell burning around the core is unstable and so hot that it causes the star to pulse the outer layers. -The photon pressure from the core also pushes away to the outer layers. -Much of the star explodes into space to create a _________ ______.

Triple Alpha Process

-The He burning in the red giant. -3He4 -> C12 + y (gamma photon) and C12 + He4 -> O16 + y -During this, the core re-expands slightly, cools, and settles into He burning.

White Dwarfs/ the compound random that is left

-The carbon remnant left behind from the compact red giant core. -It collapses and reheats in the process to 100,000 degrees K. This is an "O" type star. -It is extremely intense light, it is very small. but it is Earth-sized so there is very low luminosity. It tends to collapse but what stop them to do it is the Electron Degeneracy Pressure. Example: Sirius B, which very close to the Earth and easy to see for us.

Range Three Star Interiors

-These stars are not convective throughout: They have a radiating core, and radiative zone to cause He to stay within the core.

Electron Degeneracy Pressure

-This stops the collapse of the White Dwarf, because it is impossible for the star to become any more compact or heated while staying together, because you can't force electrons in the same energy level. -Therefore, star becomes: Degenerate White Dwarf.

Horizontal Branch

-When the H-burning shell cools, the pressure drops, the outer star collapses some and then heats up, the giant becomes less red and more orange, which is the cause of the leftward shift to this branch on the HR diagram.

Red Giant

-size of the Earth's orbit: 300 million km -it's three layered core is the size of Earth: 1. carbon and oxygen core 2. helium fusing shell outside of the core 3. outer dormant hydrogen fusing shell

One tsp of mass from a Degenerate White Dwarf would weight ___________ on Earth.

10 tons

He burns in the core for about ____ of the time of the total Main Sequence phase.

10%

Hottest Supergiant Star

Blue supergiants are supergiant stars (class I) of spectral type O. They are extremely hot and bright, with surface temperatures of between 20,000 - 50,000 degrees Celsius. The best known example is Rigel, the brightest star in the constellation of Orion.

Biggest Star in the Universe?

Answer: The largest known star (in terms of mass and brightness) is called the Pistol Star. It is believed to be 100 times as massive as our Sun, and 10,000,000 times as bright! In 1990, a star named the Pistol Star was known to lie at the center of the Pistol Nebula in the Milky Way Galaxy.

Asymptotic Giant Branch

This is the upward and right shift on the HR diagram when the core collapses again, the outer layers re-expand, and the star heads towards super giant stardom, but is not stable enough to withstand the gravity so it legit falls apart. So, it will never become a Super giant star