Category: ask

What are nebulas?. And why nebulas are big as …

What are nebulas?. And why nebulas are big as galaxies.

Basically, a nebula a huge cloud of gas and dust. Some nebulae are the rest of the death of a giant star, like a supernova. Other nebulae are where new stars are forming. (more)

The nebulae are divided into some types:

  • Emission Nebulae
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Emission nebulae are gas clouds with high temperature. The atoms in the cloud are energized by ultraviolet light from a nearby star and emit radiation when they decay to lower energy states. Emission nebulae are usually red, because of hydrogen, the most common gas in the Universe and commonly emitting red light.

  • Reflection nebulae
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Reflection nebulae are dust clouds that simply reflect the light of a star or nearby stars. Reflection nebulae are usually blue because the blue light is spread more easily. Emission and reflection nebulae are usually seen together and are sometimes called diffuse nebulae.

  • Dark nebulae
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There are also dark nebulae, they are clouds of gas and dust that almost completely prevent the light from passing through them, are identified by the contrast with the sky around them, which is always more starry or bright. They may be associated with star formation regions.

  • Planetary nebulae
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Planetary nebulae were named after William Herschel because when they first appeared to the telescope, they resembled a planet, later it was discovered that they were caused by ejected material from a central star. This material is illuminated by the central star and shines, and an emission spectrum can be observed. The central star usually ends up as a white dwarf.

  • Remnant of supernova
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Remnant of supernova is a gas envelope, composed of the remains of a star that was destroyed by a violent explosion, supernova, marking the death of this.

If the earth had rings, would we see them when…

If the earth had rings, would we see them when it was night? It's a stupid question but still

Yes, just as the moon reflects the light of the Sun, the rings also reflect. But perhaps they would not be like the rings of Saturn, they would be smaller because the Earth has the gravity smaller than the one of Saturn to hold them and also they would not be made of ice, because they would be closer to the Sun. There is a specific point in the System Solar known as “ice line” or “snow line”. This is the point in the Solar System, where ice deposits could have survived for long periods of time. Any closer and the radiation from the Sun sublimates the ice away. Instead, the rings could be made of rock and dust.

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Why does Saturn have a ring and how was the ri…

Why does Saturn have a ring and how was the ring made?

It is not only Saturn that has rings, Jupiter, Uranus and Neptune also has rings, although they are more discreet.

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The origin of the rings is unknown. The first theory concluded that its formation occurred along with that of the planets about 4 billion years ago, but recent studies indicate that they are younger, only a few hundred million years old. Another theory suggests that a comet disintegrated due to tidal forces as it passed near Saturn. Another possibility is the collision of a comet with a moon of Saturn that, when disintegrating, would have formed the mysterious structure.

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Theoretically, what would happen if two black …

Theoretically, what would happen if two black holes were next to each other or crossing paths?

Theoretically the collision of black holes gives rise to gravitational waves, and is one of the most extreme events of the universe.

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The result of the collision of two black holes results in a single black hole and its mass is somewhat smaller than the sum of the masses of both, the rest is released in the form of energy ie gravitational waves.

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Por exemplo: two black holes — of 36 and 29 solar masses — merging into a single 62 solar mass one. Those missing three solar masses? They were converted into pure energy: gravitational waves rippling through the fabric of space.

I was wondering if you could go in depth, at l…

I was wondering if you could go in depth, at least to a degree about how incredibly dense objects have strong enough gravity to distort light. To me that's one of the wildest concepts I can imagine, not that I expect you to be all knowing but maybe you've got a good article or something? I don't recall if you've ever made posts about the theory of relativity. Sorry for the long ask!

Well, I know only the basics, things I study in my free time, however, I can try to explain. The distortion of space-time is described by Einstein’s Theory of General Reality. The more massive an object, the more its curvature will be in the space-time fabric.

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This distortion in light is known as a gravitational lensing. The gravitational lensing is formed due to a space-time distortion caused by the presence of a large mass body between a distant light source and an observer.

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These distortions are widely observed through globular clusters.

Since the amount of lensing depends on the total mass of the cluster, gravitational lensing can be used to ‘weigh’ clusters. This has considerably improved our understanding of the distribution of the ‘hidden’ dark matter in galaxy clusters and hence in the Universe as a whole. The effect of gravitational lensing also allowed a first step towards revealing the mystery of the dark energy.

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As gravitational lenses function as magnification glasses it is possible to use them to study distant galaxies from the early Universe, which otherwise would be impossible to see.

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Gravitational lensing happens on all scales – the gravitational field of galaxies and clusters of galaxies can lens light, but so can smaller objects such as stars and planets. Even the mass of our own bodies will lens light passing near us a tiny bit, although the effect is too small to ever measure.

What would cause two stars to collide? What do…

What would cause two stars to collide? What does it take for a whole planet (as massive as Jupiter) to change trajectory?

The main mechanism that would make two stars collide is gravity. This depends on several factors, some stars may wander through space and end up being attracted by the gravitational field of another star, from there, one star begins to orbit the other. 

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But the most common are collisions in clusters of stars, because in a star cluster the stars are very close together, especially in globular clusters. 

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Collisions of young stars may also occur, as most of the stars are born close to each other in clusters. Many stars are binary, formed together, but in some cases before they evolve they may end up colliding.

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In the universe both collisions of active stars can occur, as can collisions of white dwarfs, neutron stars and black holes.

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The orbits of the planets are determined by the gravitational pull of the Sun, so it would need some very extreme force to cause the orbit of a planet to change its trajectory, perhaps if some planet or star enters our solar system, or when the Sun goes through changes and become a white dwarf in about 5 billion years.

What are your thoughts on Eta Carinae? I'…

What are your thoughts on Eta Carinae? I'm sad at the prospect of a star dying since it's so huge and close to death, but currently it's an amazing hypergiant binary that makes me look forward to cataloguing new star types after I finish uni

It is an incredible binary system. It was believed that Eta Carinae was a unique super massive star, but the binary nature of the system was proposed by the Brazilian astronomer Augusto Damineli in 1996 and confirmed in 2005, it is very cool to see a Brazilian astronomer do such an amazing job in astronomy!

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Unfortunately, because it is so huge, eta carinae is almost exploding. Eta Carinae is likely to become a super bright supernova if it continues to lose mass until it collapses, or to become a black hole without a visible explosion.

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It’s the law of the Universe, the biggest stars die first…

What creates neutron stars and how dangerous a…

What creates neutron stars and how dangerous are they???

A neutron star is the collapsed core of a large star which before collapse had a total of between 10 and 29 solar masses.
These tiny, dense stars are the result of a supernova explosion. They can also result in black holes.

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A neutron star is dangerous unless it is very close. The pulsars are a type of neutron star. These stars emit two beams of radiation from their poles, and if a planet is too close, it can destroy its atmosphere, and so the planet would be exposed to cosmic radiation and also the radiation of the pulsar itself.

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what is the universe expanding into?

what is the universe expanding into?

The universe does not expand “into” anything and does not require space to exist “outside” it. Technically neither space, nor objects in space, move. Instead it is the metric governing the size and geometry of spacetimeitself that changes in scale. Although light and objects within spacetime cannot travel faster than the speed of light, this limitation does not restrict the metric itself. To an observer it appears that space is expanding and all but the nearest galaxies are receding into the distance.

What’s the biggest misconception people …

What’s the biggest misconception people have about space or astronomy in general?

I’m not sure which is the biggest mistake, but I believe that one of them is the colors that are imposed on the images of planets, nebulae and other bodies of space. Many images are not real colors, many of them are fake colors. False colors are used to differentiate, some particular type of material, temperature, wavelength, chemical or mineral variations, and other factors.

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Mercury with colors in visible light

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Color-enhanced, this image represents chemical and mineral variations across the planet: tan areas are lava-formed plains, and blue regions show material that reflects little light.

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This image shows two different views of the Horsehead Nebula. On the right is a view of the nebula in visible light, taken using the European Southern Observatory’s Very Large Telescope in Chile . The new image on the left shows the nebula in the infrared, using observations from Hubble’s high-resolution Wide Field Camera 3.

Some illustrations of space can also deceive or confuse, like images of exoplanets, where in fact we do not know for sure what it would be, since we can not have such clear images to the point where we can see them closely, and other things like representation of the curvature of space time, which shows a curvature in 2D, would actually be in 3D, but this is a little harder to visualize.

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Curvature of the space-time fabric in 2D

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Curvature of the space-time fabric in 3D

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An annotated view of the Beta Pictoris system.

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Artist’s impression of Beta Pictoris b. The debris disk around the parent star can be seen.

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