0
Novas
Supernovas and Novas are terms to describe the massive explosion of a star that has reached the end of its life.
357 Questions
What does nova and white dwarf mean?
A drying star that has collapsed to the size of the earth and is slowly cooling off; located are lower left of the H-R diagram.
What causes a nova to explode?
A nova (as distinct from a supernova) is produced in a close binary system where one member is a white dwarf and the other a larger, less dense star. The white dwarf 'sucks' gas from the larger star which condenses into an accretion disc around the white star's equator. When this accretion disc reaches a critical mass it interacts with material on the white star and produces a huge thermonuclear explosion. This is what we see as a nova event.
Novae are variable stars.
What factor determines what happens to the star after a supernova?
Mass decides a stars ultimate fate.
What is the term for the tiny and very dense white dwarf star that is left behind after a supernova?
I think that's a pulsar.
What age are stars before they explode?
It depends on the initial mass of the star - i.e., how much actual material it contains. The more massive a star is, the shorter its 'life'. Most stars average out at roughly the mass of the Sun (certainly within a fairly narrow range either side of it at least) and the lifetime for such stars is therefore about the same as the Sun's - about 10 billion years. Really massive stars like eta Carinae will run through their nuclear reactions at a much faster rate and so will only last for a few million years. Eta Carinae could go supernova any day now!
How can you identify a supernova remnant?
Well, it may not always be possible to do this in every case, but there are certain things to look for.
Often a supernova will leave some relic behind, such as a pulsar or black hole, so you can look and see if there is one of these phenomena present.
Also (as in the case of the Crab Nebula) we know that there was a supernova some time in the past and we can see the result with our eyes. In this case we have a pulsar at the centre as well!
After a long time, if there are any gases present from the explosion, these may dissipate owing to the object's galactic motion or gravitational effects from passing stars (really the same thing!) so the Crab Nebula may not look quite so crablike in a few million years' time.
What is it called when a bunch of white dwarfs explode?
There is no such thing as a "bunch of White dwarfs", let alone exploding white dwarfs.
The nearest explanation would be a nova. See related question.
Because they run out of the resources they use which consist of gases. It eventually 'dies' just like you would if you didnt eat food for a long period of time.
This results in the star dying/exploding causing a supernova explosion
What elements are left after a star explodes?
All of them. A star begins to die when it creates Iron. Then it creates all the elements heavier than Iron. It has already created the elements lighter. Thus when the star explodes it spreads the elements it has created witch is all of them.
How long does it take a stellar iron core to collapse?
It takes only milliseconds for a stellar iron core to collapse when it reaches the end of its life cycle. This rapid collapse leads to a supernova explosion.
They are made all the time. 30 - 60 are discovered in our Milky Way every year.
Who discovered the new star in Cassiopeia?
Although not noted as a supernova, the nebula "Cassiopeia A" was first observed by John Flamsteed on August 16, 1680. It is likely that intervening dust clouds obscured the brightness of the supernova, which might otherwise have been observed in 1667.
Current estimates place the distance from Earth as around 11,000 light years. If that is correct, then the supernova explosion actually took place around 9,000 BCE. (see related link)
How long does a neutron star last after a supernova?
Nobody knows for sure, but billions of years. It would also depend on when the neutron star, no longer becomes a star. Is it when it stops radiating heat, or x-rays? The star or the remains will continue to be a physical property but will no longer radiate any energy.
What causes the collapse of a star?
The collapse of a star is based on its age. When it runs out of "Fuel" its inside contracts as the outside expands. it can then super nova or collapse into a tiny star.
Are there more white dwarfs of more black holes?
I think white dwarfs. This is because they are much more low mass than black holes. White dwarfs are much more common in the universe than black holes, because we have only discovered a few black holes whereas we are aware of many white dwarfs.
Do all stars experience a supernova when they die?
No. Our sun, for instance, after an expansion (red giant) stage that may encompass Earth, will then compress its entire mass into a very dense body about the size of Earth. It will then be known as a white dwarf. This phase, lacks a fusion process and consists of radiating stored thermal energy. The radiation from this stage will supply very little energy to the rest of the system but will take many billions of years to cool. Finally, our sun will remain in one piece, a dark body of matter that continues to orbit in our galaxy. The planets will continue to orbit around it, but without star-shine. It will then be known as a cold black dwarf.
An idea of the time frame involved can be gleaned from this thought. It is believed that: no black dwarfs exist, since the universe, at about 13.7 billion years of age, isn't mature enough to have allowed any star the necessary amount of time for this process to complete itself.
Compression.
Do you mean lighter in color? Halley's comet has an albedo of about 0.04, which is the color of tar. Our Moon has an albedo of about 0.07, which is the color of weathered asphalt.
If you mean lighter as in less massive... we've never seen a comet as massive as our Moon, but there are some pretty tiny moons out there in the outer solar system; a few comets might be larger than some of them.
Is the final stage of a star a white dwarf or a black hole?
A black hole may only occur at the end of the life of a very massive star. Most other stars will collapse into a dense White dwarf, which will gradually become a black dwarf star over many billions of years.
Following certain types of Supernova events there can often be a gravitational collapse of massive stars and this can result in the stellar remnant becoming a neutron star. Based on the Tolman-Oppenheimer-Volkoff limit the solar mass of a neutron star can range from 1.5 to 3.0 solar masses.
