December 27, 2015 at 11:22Ask Ethan # 40: Who's pretending to be a supernova?
- Transfer
The reader asks:
Let's start with the very supernovae these objects pretend to be.
From time to time, a very dim star in our galaxy (and, in principle, in any galaxy), which is usually not even visible to the naked eye, suddenly becomes so bright that it can become brighter than all the other stars in the sky. In the past, they could shine even brighter than planets, and become visible even during the day. Initially they were called “stella nova” (“new star” in Latin), and these supernova outbursts were actually great events that announced the end of the star’s life.
They are obtained in different cases, for example:
In any case, a huge amount of energy is released in a very short period of time. In just a few days, the same amount of energy is released as the Sun radiates in 10-12 billion years. And in any case, the original star dies, leaving either a neutron star, or a black hole, or just a cloud of ionized plasma and gas.
But sometimes you can observe a very vivid phenomenon that persists in the sky not for days or weeks, but for years. And after that, the star becomes less bright than it was before, but still does not completely disappear. The η Carinae mentioned in the question was the first star, and the only one in our galaxy to show such behavior.
Let's deal with her story.
In most constellations, astronomers call the brightest star "alpha", the next brightest "beta", etc. Therefore, Canopus, the brightest star in the constellation Kiel, it is also the second brightest in the whole sky, called α Carinae, the second brightest, Miaplacidus - β Carinae, and then in the Greek alphabet. Thus, most of the observations of η Carinae were seventh in brightness.
But today you will not see her in the sky, even the darkest and even with perfect vision.
This area of the sky is full of stars, and it is located in the plane of the Milky Way, where star clusters form. But what happened to this star? In 1837, the star underwent a strong eruption, became brighter than usual - but not as bright as a supernova - for a period of 21 years. At the peak of brightness in 1843, it was called a pseudo-supernova (this was the first such case), and then it became the second brightest star in the sky, even brighter than Canopus, which in that constellation was alpha.
At the peak of brightness, the sky around the constellation most likely looked as calculated on this computer simulation:
From 1837 to 1858 it remained bright and then faded. By the end of the 1860s, it was already impossible to see with the naked eye, and then it became brighter again, and went out again in the 1880s - 1890s, and over the past 100 years it has been gaining brightness, although it still can not be seen without binoculars .
So what is the reason for this behavior? It turns out that you can learn a lot by looking at η Carinae and its surroundings today. Since this region is rich in dust, it is best to look at it in infrared light.
In this region, there is a lot of dust and forming stars, and in the center there is a star cluster - the Carina Nebula. And the bright object in the lower left corner is the pseudo-supernova, η Carinae. It is not surprising that she is young, bright and massive. Indeed, it is in new star clusters that one can find the most massive stars in the Universe. And this is not surprising, since they live only a few million years.
η Carinae is one of the most massive stars known to us, and perhaps the most massive of the known in our galaxy. Its mass is 100-150 solar. Only in cluster R136 in the Tarantula Nebula are more massive stars observed, the most massive of which draws 260 solar masses.
Of course, the most massive stars spend their fuel the fastest, and die in the form of supernovae before everyone else. But if a star becomes too massive and asymmetric, or acquires another unstable feature, then a phenomenon can occur with it in which a nuclear cascade occurs inside the star and does not destroy it.
Instead, a massive ejection of matter occurs, but the star remains intact and continues to burn fuel, having already a smaller mass, as if nothing had happened. And if we look at η Carinae today, this is exactly what we will see.
This photograph, taken by the Hubble telescope, shows a double nebula and the outer edges of a region filled with scattered gas and plasma. All matter in total weighs about 20 times more than our Sun. At the same time, a bright blue star is still in the center.
Will it ever turn into a supernova? Of course. But will this happen soon? Maybe.
The UGC 4904 galaxy has a pseudo-supernova discovered in 2004. The star, defined as a bright blue variable (and η carinae is defined in the same way), increased brightness and pulled out a mass of itself, then slowly faded, and two years later died in a hypernova explosion.
Therefore, a pseudo-supernova event can be regarded as a preliminary tremor before an earthquake - a sign that a more serious event will soon follow. But other bright blue variables do not instantly turn into supernovae. For example, the Swan P in our galaxy, which became very bright in the 17th century, still remains stable.
So what do we see when we look at a pseudo-supernova? An ultra-massive, ultra-bright blue star (at least 50 times more massive than the Sun), burning its fuel brighter than all the new stars that we saw, but not as bright as supernovae - for example, like this one located in Monsieur 99:
Why mass ejection? Here are some of the leading ideas:
It is interesting that some other theories on this subject were refuted precisely thanks to the light echo from a star flare in 1837 - the reflection of ancient light from clouds of interstellar gas began to reach our planet, and allowed us to better understand certain properties of at least this pseudo- supernova.
In the next 10-15 years, we will be able to learn even more about this event. Here is what we already know:
I would like to learn more about space objects that can be confused with supernovae. My favorite subject. This keel just belongs to this type. It is very difficult to find material on this subject. Surprisingly, these objects can throw out so much mass and continue to exist.
Let's start with the very supernovae these objects pretend to be.
From time to time, a very dim star in our galaxy (and, in principle, in any galaxy), which is usually not even visible to the naked eye, suddenly becomes so bright that it can become brighter than all the other stars in the sky. In the past, they could shine even brighter than planets, and become visible even during the day. Initially they were called “stella nova” (“new star” in Latin), and these supernova outbursts were actually great events that announced the end of the star’s life.
They are obtained in different cases, for example:
- A very massive star runs out of fuel, which is burned with the release of energy through nuclear fusion in the nucleus; the star collapses and explodes
- The white dwarf, a former star of the Sun class, turned into a mixture of carbon, oxygen and silicon, acquires additional mass, contracts under its own weight and starts an uncontrolled synthesis reaction, tearing the star
- Two white dwarfs connect or collide, which again leads to a reaction tearing them apart
In any case, a huge amount of energy is released in a very short period of time. In just a few days, the same amount of energy is released as the Sun radiates in 10-12 billion years. And in any case, the original star dies, leaving either a neutron star, or a black hole, or just a cloud of ionized plasma and gas.
But sometimes you can observe a very vivid phenomenon that persists in the sky not for days or weeks, but for years. And after that, the star becomes less bright than it was before, but still does not completely disappear. The η Carinae mentioned in the question was the first star, and the only one in our galaxy to show such behavior.
Let's deal with her story.
In most constellations, astronomers call the brightest star "alpha", the next brightest "beta", etc. Therefore, Canopus, the brightest star in the constellation Kiel, it is also the second brightest in the whole sky, called α Carinae, the second brightest, Miaplacidus - β Carinae, and then in the Greek alphabet. Thus, most of the observations of η Carinae were seventh in brightness.
But today you will not see her in the sky, even the darkest and even with perfect vision.
This area of the sky is full of stars, and it is located in the plane of the Milky Way, where star clusters form. But what happened to this star? In 1837, the star underwent a strong eruption, became brighter than usual - but not as bright as a supernova - for a period of 21 years. At the peak of brightness in 1843, it was called a pseudo-supernova (this was the first such case), and then it became the second brightest star in the sky, even brighter than Canopus, which in that constellation was alpha.
At the peak of brightness, the sky around the constellation most likely looked as calculated on this computer simulation:
From 1837 to 1858 it remained bright and then faded. By the end of the 1860s, it was already impossible to see with the naked eye, and then it became brighter again, and went out again in the 1880s - 1890s, and over the past 100 years it has been gaining brightness, although it still can not be seen without binoculars .
So what is the reason for this behavior? It turns out that you can learn a lot by looking at η Carinae and its surroundings today. Since this region is rich in dust, it is best to look at it in infrared light.
In this region, there is a lot of dust and forming stars, and in the center there is a star cluster - the Carina Nebula. And the bright object in the lower left corner is the pseudo-supernova, η Carinae. It is not surprising that she is young, bright and massive. Indeed, it is in new star clusters that one can find the most massive stars in the Universe. And this is not surprising, since they live only a few million years.
η Carinae is one of the most massive stars known to us, and perhaps the most massive of the known in our galaxy. Its mass is 100-150 solar. Only in cluster R136 in the Tarantula Nebula are more massive stars observed, the most massive of which draws 260 solar masses.
Of course, the most massive stars spend their fuel the fastest, and die in the form of supernovae before everyone else. But if a star becomes too massive and asymmetric, or acquires another unstable feature, then a phenomenon can occur with it in which a nuclear cascade occurs inside the star and does not destroy it.
Instead, a massive ejection of matter occurs, but the star remains intact and continues to burn fuel, having already a smaller mass, as if nothing had happened. And if we look at η Carinae today, this is exactly what we will see.
This photograph, taken by the Hubble telescope, shows a double nebula and the outer edges of a region filled with scattered gas and plasma. All matter in total weighs about 20 times more than our Sun. At the same time, a bright blue star is still in the center.
Will it ever turn into a supernova? Of course. But will this happen soon? Maybe.
The UGC 4904 galaxy has a pseudo-supernova discovered in 2004. The star, defined as a bright blue variable (and η carinae is defined in the same way), increased brightness and pulled out a mass of itself, then slowly faded, and two years later died in a hypernova explosion.
Therefore, a pseudo-supernova event can be regarded as a preliminary tremor before an earthquake - a sign that a more serious event will soon follow. But other bright blue variables do not instantly turn into supernovae. For example, the Swan P in our galaxy, which became very bright in the 17th century, still remains stable.
So what do we see when we look at a pseudo-supernova? An ultra-massive, ultra-bright blue star (at least 50 times more massive than the Sun), burning its fuel brighter than all the new stars that we saw, but not as bright as supernovae - for example, like this one located in Monsieur 99:
Why mass ejection? Here are some of the leading ideas:
- one of the layers of the star spends its fuel, contracts and spreads vibrations throughout the body of the star, which leads to additional synthesis, energy production and explosion
- the star shifts from bright blue to the Wolf-Rayet star. R136a1, the most massive known, is an example of such a star.
- supermassive companion star launches ejection process
It is interesting that some other theories on this subject were refuted precisely thanks to the light echo from a star flare in 1837 - the reflection of ancient light from clouds of interstellar gas began to reach our planet, and allowed us to better understand certain properties of at least this pseudo- supernova.
In the next 10-15 years, we will be able to learn even more about this event. Here is what we already know:
- An exploded nebula travels at a speed of 210 km / s, which is much slower than a regular supernova
- the explosion temperature was 5000 K, which is much less than previously thought, and even less than that calculated in modern theoretical models
- no spectral lines of radiation are observed — only absorption, which excludes the model of “opaque stellar winds”. As written in the article about this event:
- “The cause of the explosion and the loss of mass is still unclear, but the data of radiation transfer models trying to predict the mass ejection η Carinae can now be compared with spectral observations. Alternative models, such as those that included an accretion disk from a companion star, can now be confirmed and disproved. ”