Questions tagged [nebula]

A collection of ionized gases and dust in interstellar space

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29 votes
2 answers
30k views

How many stars and galaxies can be seen by the naked eye?

How many of the luminous dots that we see naked are galaxies and not stars from our galaxy? I imagine that the majority of the luminous points that we see naked eye during the night, are actually ...
28 votes
2 answers
5k views

When stars explode after running out of fuel, why are new stars born from the remnants?

I'm not a physicist or have a very good physics background but I've often wondered why there are new stars that are born in the nebula which was created after the parent star has exploded. As I ...
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26 votes
4 answers
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How else can a star form, other than gravitational collapse?

I read this paragraph on the Sun's page on Wikipedia: [The Sun] formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most ...
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25 votes
3 answers
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Why is the Eagle Nebula so "static"?

This, of course, is a newbie question, as I am nothing more than a hobbyist. But I was quite surprised to see the recently-released "before and after" pictures of the so-called "Pillars of Creation" ...
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20 votes
2 answers
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Will new stars stop forming at some point of time?

New stars keep forming in the universe thanks to all the nebulae. Now, we need Hydrogen to form stars and there would a time when all the hydrogen will get exhausted, and no more star formation will ...
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19 votes
3 answers
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Why can space telescopes see through a planetary nebula?

I recently read the book "An Introduction to Planetary Nebulae" by Jason J. Nishiyama. Although I'm not an astronomy student, I could at least understand the written texts and less the ...
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18 votes
1 answer
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What causes the sharp if irregular boundary line in the "Cosmic Cliffs" JWST Carina image?

In this recently released JWST image: we can see a relatively sharp, if irregular, boundary line between a region appearing mostly bluish and a region appearing mostly reddish or orange (understood ...
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16 votes
2 answers
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Is it possible that the Sun and all the nearby stars formed from the same nebula?

I was looking at a map of our local stellar neighborhood, and it occured to me, the stars are really close, if one compares them to the size of some nebulae. So can it be, that the Sun, Alpha Centauri ...
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14 votes
1 answer
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What are the large round dark "holes" in this NASA Hubble image of the Crab Nebula?

I came across this image of the Crab Nebula taken from NASA Hubble telescope. What are the large round "holes" and how are they formed?
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13 votes
3 answers
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Are Brown and Sub-Brown Dwarfs secretly more common than stars?

I recently heard that Red Dwarfs are the most common type of star, and low-mass Red Dwarfs are the most common type of Red Dwarf. This seems to imply a generic trend that the lower the mass, the more ...
9 votes
2 answers
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Is Barnard 68 the only cloud so close to us that there are no stars between us and it?

Regarding molecular clouds / absorption nebulae / Bok globules / obscuring clouds, (I'm not sure if there's one generic term encompassing all those and any similar obscuring clouds - I just used "...
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9 votes
1 answer
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Will the nebula of Betelgeuse be visible to the naked eye? How bright, how large, how soon, for how long?

When Betelgeuse goes core collapse supernova it will leave a supernova remnant. Will it become visible to the naked eye? If so, in what time frame will it be visible. Will it be star like from the ...
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8 votes
1 answer
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What is the bright orange star?

After reading this NASA article on Tarantula's Nebula of this image: What is the really bright orange star in the center or upper-left of the young blue stars? The second link further provides ...
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8 votes
1 answer
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Why is the Boomerang Nebula colder than the CMB?

An earlier answer on temperature mentioned that the temp of the Cosmic Microwave Background (CMB) is $2.4\,{\rm K}$ and the temp of the Boomerang nebula as ${\rm 1\,K}$. How did the nebula cool faster ...
8 votes
3 answers
817 views

Are nebulae only visible from a distance?

There's plenty of data about the density of nebulae, and obviously they're pretty thin. This is space, after all, and these things are really, really big. But I'm wondering about the practical ...
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8 votes
1 answer
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The physical processes of emission lines in cosmic nebula

I think I understand how absorption lines in cosmic bodies occur. But after reading about the emission lines in quasars I am wondering more and more about the physical processes causing the emission ...
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8 votes
4 answers
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Can we see the color of nebulae?

Someone asked me this question: To see the color of the Great Nebula in Orion, how large the aperture of the telescope should be. I don’t even know whether this is possible. I understand that the ...
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7 votes
1 answer
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Why are O III lines so prominent in the spectra of emission nebulae when the amount of oxygen relative to hydrogen is a million times smaller?

Looking at spectra of emission nebulae like the Lagoon Nebula, the $[\text{O III}]$ lines are prominent in intensity. However, the abundance of oxygen is minuscule compared to hydrogen. How then are ...
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6 votes
2 answers
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Could stars be seen from inside a nebula?

Nebulae look dark against the backdrop of stars, but how opaque are they likely to be from inside? In other words, if our Solar System had drifted into the middle of, say, the Horsehead Nebula, would ...
6 votes
1 answer
231 views

Assuming no light pollution, was "2C. 1406" ever visible to the naked eye?

Joseph Needham, in his Science and Civilisation in China Vol. III, claimed that there was an ancient record of a nova about three thousand years ago. As a result of private correspondences with a "Dr ...
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6 votes
1 answer
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What are realistic and unrealistic values for the high energy gamma ray spectral indices of pulsar wind nebulae?

This summer, I was working on a project fitting very high energy gamma ray spectra of the Crab Nebula, a pulsar wind nebula. At energies about $\sim$1 TeV, a simple power law suffices, i.e. $\phi(E)\...
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5 votes
1 answer
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Whose name is Minkowski 92 bearing?

Minkowski 92 is a protoplanetary nebula. But after which Minkowski is it named? Same question for Minkowski's object (part of NGC 541).
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1 answer
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How big is nebula dust?

Whenever I see the term dust for the particles of a nebula, I ask myself whether this is actually based on some reliable measure of particle size. Of course we can all agree it looks like dust from ...
5 votes
1 answer
349 views

Why does hydrogen ionization happen in HII regions?

Why does hydrogen ionization happen in HII regions? Why is the hydrogen there ionized?
5 votes
1 answer
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Why is there billowing dust in nebulae?

Why do some nebulae look like the billowing clouds? Wouldn't that require something like a viscosity in empty space?
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1 answer
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Whose name is Fleming 1 nebula bearing?

Fleming 1 is an unusual planetary nebula situated in the Centaurus constellation. Yet it is not clear after who it was named
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2 answers
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Are older main-sequence stars found in or near molecular clouds?

From what I have read as molecular clouds are the birth place of stars, their population as you would assume are young stars or stellar remnants but so far I have not found out if there are main-...
4 votes
1 answer
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Long-lived supernova remnants?

We cannot see the supernova remnant of the star that triggered the formation of the Sun and the Solar System, as the remnant dispersed and became mixed into the interstellar medium. So I am wondering, ...
4 votes
1 answer
156 views

Why was StDr56 discovered only now?

StDr56 is a newly discovered planetary nebula (maybe). link1 link2 It was found by amateur astronomers Marcel Drechsler and Xavier Strottner. According to the above articles, it's pretty big: With an ...
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4 votes
1 answer
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How long do hot X-ray sources last?

Some X-ray sources in nebulae are caused by hot materials in the millions of degrees that formed in supernovae. What's the cooling rate of this stuff? How long does it stay this hot? If we would take ...
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4 votes
1 answer
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How do proto-planetary nebulae gain momentum?

currently I am curious about proto-planetary nebulae. At first I was curious about how planets spin but I read in a couple of articles that they got their spin from when they were in a proto-planetary ...
4 votes
1 answer
117 views

How can an accretion disk form around the central star of a planetary nebula?

I was reading the 2012 paper A tidally destructed massive planet as the progenitor of the two light planets around the sdB star KIC 05807616 about the possible origin of two exoplanets that orbit a ...
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0 answers
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From what distance could the Sun's planetary nebula be seen entirely with free eye?

When collapsing to a white dwarf, a red giant Sun would emit a planetary nebula. How far from the Sun would that nebula stretch at most? Also: At about what distance could you see the planetary nebula ...
4 votes
2 answers
548 views

How to tell a nebula from a galaxy?

Not all galaxies are spiral in shape[1][2], some nebulae are huge[3] and nebula are the nursery of stars[4]. How to tell them apart? Note I have already compare the contents for galaxy and a nebula, ...
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3 votes
2 answers
535 views

Is there a Vela Nebula?

The Vela pulsar is a neutron star from a supernova that exploded 10,000 years ago. It spins 11 times a second. The Crab Nebula along with the central Crab Pulsar formed 1000 years ago. This pulsar ...
3 votes
4 answers
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Do heavier elements breakdown during supernova?

Heavier elements like gold, uranium etc. are formed at the end of a star's life. As the star explodes into a supernova, it gives rise to nebula which is the birthplace of new stars. But as the star ...
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3 votes
2 answers
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Why is the Emissivity of emission lines in unit erg.s-1.cm3?

The python package PyNeb could calculate the 'Emissivity' of an emission line at given electron temperature and density in unit "erg.s-1.cm3". But I don't know why Emissivity should in such ...
3 votes
2 answers
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How to locate nebulas visible through AstroMaster 114 telescope without device assistance?

I will be going to the desert this month and it's my understanding that the night sky will be very dark there. I've got some practice locating the planets but I'd really like to get a look at a nebula ...
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2 answers
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How do I see more than just points in the sky?

I just bought a new telescope with these specifications: Aperture: 203 mm Focal Length: 1200 mm F/ratio: f/5.9 I usually use a 28 mm eyepiece, giving me about 42.5x magnification, but I also have a ...
3 votes
1 answer
335 views

Nebula and its colors

A Nebula has bright awesome colors that include red, blue, green, orange, white, etc? They're result of excitation of electrons. Is there a clear explanation as to which color is attributed to an ...
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3 votes
1 answer
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What state of matter are nebulae in?

After doing research it said that nebulas are made of gas and dust. Are they actually gases and solids, or are they plasma?
3 votes
1 answer
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What are the dark spots in this Hubble image of the Crab Nebula?

I recently ran into this NASA Hubble image of the Crab Nebula in this article talking about its core. What I am interested to know though is: what are these round dark spots appearing in the image (...
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1 answer
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How to visually tell the difference between a planetary nebula and a supernova remnant?

If we see a nebula by looking through a powerful telescope, how can we tell whether we are looking at the remnant of a supernova or at a planetary nebula? Thanks
3 votes
0 answers
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Can the "haze" of a mirror telescope be quantified?

When reading Why was StDr56 discovered only now? and its answers and comments, I realized that refractor telescopes, and in particular the Dragonfly Telephoto Array are a great tool to find nebula and ...
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3 votes
0 answers
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Hydrogen Frost Line? Where, if anywhere, is it cold enough for Oort Cloud objects or rogue planets to have solid hydrogen on their surfaces?

I like the idea of Oort Cloud objects all being crusted with a thin layer of hydrogen snow, though what little information I've managed to find on the topic seems to imply that that is unlikely, ...
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1 answer
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Information on Planetary nebula formed from the death of our star the 'Sun'!

I want to know the expansion rate, composition, mass and density of hydrogen present of a Planetary nebula similar to that which will be formed after the death of our star the sun. Knowing these ...
3 votes
0 answers
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What are the implications if the Sun was formed in a warm nebula?

Molecular oxygen O2 has been found on comet 67P/C-G in a ratio of 3.8% to water, which is much higher than expected. An explanation proposed is that the Solar System formed from a molecular cloud ...
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3 votes
1 answer
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Can violet astronomical objects exist?

According to black-body radiation, violet stars are not possible. Even if there are 1 million Kelvin, they are blue, not violet. But are violet galaxies, nebulae, clusters etc. possible? Google found ...
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2 votes
3 answers
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How can I see a nebula?

I've recently been seeing a bunch of pictures of nebulae and I'm just fascinated by their beauty and complexity. Is there any kind of telescope that would make it possible to view it from here on ...
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2 votes
1 answer
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Why do stars rotate slower than they're expected to?

Due to conservation of angular momentum, I thought most stars would be spinning extremely fast because they have a relatively small diameter. However, it turns out that this is not true and most stars ...