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Course: Cosmology and astronomy > Unit 2
Lesson 1: Life and death of stars- Birth of stars
- Accreting mass due to gravity simulation
- Challenge: Modeling Accretion Disks
- Becoming a red giant
- White and black dwarfs
- Star field and nebula images
- Lifecycle of massive stars
- Supernova (supernovae)
- Supernova clarification
- Black holes
- Supermassive black holes
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Supernova clarification
Supernova clarification. Created by Sal Khan.
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what is a hypergiant or hypernova?(29 votes)
Good question, Hypernova and Supernova are basically the same thing. Hypernova's are just bigger in weight and mass because of the gamma rays it shoots. When that happens, that is the sound of a Quasar being born. A hyper giant is a giant star that has more potential than anything else. For Example, once a hypergiant explodes, it will go farther than the other stars that is not hyper giants. I hope this helps! :)(42 votes)
what will happen if a supernova takes place in a binary star system?thank you!(16 votes)
The remnant may start 'feeding' on the binary partner if it is close enough, siphoning plasma off the surface of its partner. Otherwise, their orbits will grow larger as the supernova remnant has significantly less mass than the predecessor star.(9 votes)
how would the Crab Nebula supernova have appeared in the night sky 1000 years ago? would it have been as an unusually bright star, brighter than anything we see today? or something like the current bright objects in the night sky, like a planet? would it have been visible at all during the day?(6 votes)
The supernova was visible during the day.
It would appear as a star steadily getting brighter and brighter.(3 votes)
how does NASA dipict pictures that are so far far from us??(5 votes)- They have this awesome new telescope called Hubble. This telescope is unique in the fact that it is not on Earth, it is floating above our heads in orbit around the Earth. It is so powerful that from its position in orbit, it can photograph ants on Earth. With this visual power, it can take amazing far away things in space.(12 votes)
how long does a supernova last ?(6 votes)- If I am correct then just a few years.(3 votes)
I heard on vsauce that 8 octillion million tons of dynamite is equal to the explosive force of a supernova.Is that statement true?If you don't think so give a little proof down below.Thanks in advance.(5 votes)- Octillion is a number and a very large one at that. Going back to the original question, let's take the ASSASN-15lh event, the most powerful supernova astronomers had ever seen, which occurred last summer. ASSASN-15lh radiated 2.2 x 10^38 joules of energy per SECOND! The atomic bomb that leveled Hiroshima during the end of World War II got all of its destructive power from a chunk of uranium smaller than a pea. Now imagine an explosion with the destructive power of a chunk of uranium the size of a moon emitted every 30 seconds. The ASSASN-15lh was so powerful that the most powerful nuclear explosion (Tsar Bomba, 50 megatons) was a mere billionth of a trillionth (a quintillionth) of the energy emitted in a single second of the ASSASN-15lh event.(6 votes)
Is the Crab Nebula a nebula or supernova?(3 votes)
It's a nebula (gas in huge quantity...), so the result of a supernova which occured many years ago.(7 votes)
- so it occured 6500 years before it was seen (1000 years ago). now its been 7500 years because we add on 1000(4 votes)
I completely agree with you because 7,500=6,500+1,000(4 votes)
How can you determine the lifespan of a red supergiant star?(4 votes)- They live short lives. It takes little more than 2 million years.(4 votes)
Why do black holes only happen when they are too massive to be a neutron star?(3 votes)- For the same reason stars become neutron stars instead of white dwarfs. Matter has only so much ability to resist collapse.
The maximum mass for a white dwarf is how much mass can be supported by the pressure of electrons resisting being pushed into each other. If there is more pressure that the electron pressure can support the electrons combine with the protons into neutrons and you get a neutron star.
A neutron star is supported by neutron pressure. And if the mass is too great for the neutrons to support it then it will collapse past a neutron star into a black hole. There is another possible step between a neutron star and a black hole but we are not sure if it would really exist, this is what would be called a quark star. A quark star would be where the neutrons all merge into a star made of only quarks but we don't know if the radius of a quark star would be smaller than the radius of the event horizon of a black hole of the same mass.(4 votes)
Video transcript
I want to make one
clarification on my video on supernovae, because that's
the plural for supernova, is that I said this supernova
occurred 1,000 years ago. That's actually not
precisely right. The supernova was first
observed 1,000 years ago, or the light from
that first explosion was observed by astronomers
we believe 1,000 years ago. But we have to be
very clear here. Because the Crab
nebula at its core is roughly 6,500
light years away, even this light, even this
image we see right here is that nebula as it
was 6,500 years ago. And so the supernova itself, if
we think about when it actually occurred, it actually must have
occurred about 7,500 years ago. So it must have occurred
about 7,500 years ago. And that first slide
from that first explosion from that first energetic
event reached us about 1,000 years ago. So it took 6,500
years to get to us, and reached us 1,000 years ago. So first light 1,000 years ago. Just wanted to make that clear. Might have been obvious
to some of you all, but always important
to think about it. When I said 1,000
years ago, I really should have said it
was first observed, the explosion was
observed 1,000 years ago. But since it's so
far, the actual event must have occurred
7,500 years ago.