Questions regarding large spheres of gas undergoing fusion.

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Yellow object between δ Ori and η Ori

Can someone perhaps assist me in identifying the yellow object between δ Ori and η Ori? I took an image of this object, but I can't identify it. It can be seen on the image below, hosted on the Eagle ...
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0answers
30 views

Instrumental magnitude to “real” magnitude - Photometry with not enough data?

I have a lot of data taken in R, B, V, Luminance and Halpha-bands which I want to analyse photometrically (one target in the frame). The frames are already reduced (with flats, darks etc.) and have a ...
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1answer
150 views

At what density does helium burning start in a star?

I have seen several references that say that helium burning begins in a star once the core temperature reaches $10^8$K (such as here) but nowhere that says what density that corresponds to. Does ...
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1answer
101 views

Why don't small stars end up as a black holes?

I've recently done some research about black holes, and I realized that big stars form black holes and small ones don't. Is it because the gravity isn't strong enough for it to fall in on itself, or ...
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1answer
82 views

What is the ratio of “real” stars in the sky?

When you look at the sky without any utilities like binocular or telescope, what is the rough ratio of "real" stars to other objects like planets, the moon, asteroids, satellites? 90% stars - 10 % ...
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1answer
47 views

Star class according to initial mass

Studying the stars classes for my homework (school) i learned that stars are classified by the spectral types (Harvard) and luminosity class (MKK) .. So the sun is a star class ...
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2answers
48 views

length of Star lifetime

In a star, the fact that not all the hydrogen is used up, not all the helium is used up etc. is a little counterintuitive. Shouldn't it be that a star looses the hydrogen layer passively, in other ...
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1answer
64 views

Why does iron consume more energy in the fusion process than it produces?

I understand that once a star starts fusing iron, it's doomed to collapse because iron fusion requires more energy than it releases in the process, allowing the opposing gravity of the star to cause ...
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0answers
60 views

Compute the colour in the AB photometric system

I have a question for homework and don't get it at all: Consider two filters as shown in the figure below. Compute the colour S1 - S2 in the AB system for a star with flux: where is a constant ...
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2answers
91 views

Could we actually freeze a star?

I read an article recently that said NASA has discovered a brown dwarf that has frozen. Given we had the technology, resources, and supplies, could we actually freeze a star and stop it from burning ...
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1answer
60 views

Age of the universe and age of stars

The age of the universe is 13.798±0.037 billion years, yet the age of HD 140283 is 14.46±0.8 billion years, how this can be the case?
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1answer
647 views

What causes the dimensions of a star increase when its hydrogen fuel is exhausted?

What causes the dimensions of a star increase when its hydrogen fuel is exhausted? For example, the Sun is expected to increase its radius 250 times. What causes this if its temperature is expected to ...
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2answers
144 views

Can we see individual stars in other galaxies?

Just wondering if we can examine individual stars from other galaxies, or if we are pretty much stuck with the billions that are in the Milky Way?
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1answer
57 views

Why can't the surfaces of stars be observed?

If I'm correctly informed, only three stars: Sol, Betelgeuse and Altair have surfaces which have been resolved by telescopes. All other stars are only point sources of light, even in the greatest of ...
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1answer
69 views

Requesting book references for a non-expert person with math background or just a non-expert person

I've just finished my masters degree (to be exact previous week ^_^). And I'm completing my collection of applications of my studies. During previous year I started reading about Robotics and Coding ...
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3answers
163 views

Is there enough hydrogen left after a star dies so another star will have enough to light up?

A star consumes quite a lot of hydrogen in its life, and is pretty much "vacuuming" everything in its vicinity. After it dies (eventually by supernova which will spread all its composition over light ...
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1answer
139 views

If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?

I posted this as a question to Scientific Imagination (Area 51 proposal) a while ago. And it was suggested that this question "is perfectly acceptable on Astronomy SE", since "it's about stellar ...
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2answers
79 views

any unique phenomenon when the cores of two planets are aligned with their star's core?

Imagine a line passing through the cores of two planets (in the same planetary system) and their star. Have we ever witnessed this - either with both planets on the same side of the star or on ...
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1answer
65 views

Is there a term for stars without any planets?

Quite simply, is there any used term for stars that don't have any planets? While contemplating this and doing numerous searches to no avail, I think I found my own answer, but I'm asking here for ...
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1answer
74 views

Mechanism for Brown Dwarf Fusion

I've read (at here, among other places: http://deepblue.lib.umich.edu/bitstream/handle/2027.42/55288/index.html?sequence=1) that during the Degenerate Era, star formation will end and the last stars ...
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2answers
187 views

Are there stars that don't emit visible light?

Are there stars that do not emit any light in the visible part of the EM spectrum?
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2answers
170 views

Why don't planets give off their own light? [closed]

Why don't the planets glow like stars?
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5answers
240 views

Why aren't there galaxy-sized balls of iron out there?

Since we know that stars burn out, collapse, or blow up when too many of their atoms fuse inti iron, then how come, with all the ancient galaxies we've been observing, there isn't one galaxy whose ...
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1answer
60 views

What is star composition after formation

Most descriptions of star ignition go something like... The star reaches a critical mass and ignites, blowing away the surrounding material. The most obvious question would be "Why are stars not all ...
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2answers
121 views

Weight of a celestial body

How do astronomers find out the correct weight of a planet tough there isn't any direct means to weigh them?What technique do they use?Just curious!
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1answer
44 views

Electron Degeneracy Pressure and the Pauli Exclusion Principle

I have read that what keeps white dwarfs from gravitational collapse is electron degeneracy pressure. How does this pressure prevent further collapse, and how is it related to the Pauli Exclusion ...
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2answers
169 views

Is a white dwarf hotter than a Red Giant?

From what I've read, white stars are hotter than red ones. But a white dwarf would have just heavy elements to fuse, so shouldn't it be less bright?
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4answers
286 views

What would the effects be on Earth if Jupiter was turned into a star?

In Clarke's book 2010, the monolith and its brethren turned Jupiter into the small star nicknamed Lucifer. Ignoring the reality that we won't have any magical ...
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3answers
126 views

Can there be an infinity of stars in the Universe?

I have a mind puzzle. Can there be an infinity of stars in the Universe ? I have 2 opposed reasonings, yet I don’t find any flaw in them. Can you help me here ? Answer A : No, the number of stars ...
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1answer
73 views

What's an order-of-magnitude main sequence star look like?

I'm looking for a very rough, order-of-magnitude approach to the main sequence. What I mean is, I have a spherically-symmetric hydrogen distribution. I'm looking to get a rough approximation for ...
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2answers
37 views

Can solar luminosity & activity be predicted?

Can a star's luminosity and its activity, solar flares and sunspots, be predicted? If so, with what accuracy & precision?
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1answer
41 views

how to measure temperature of the distant star [duplicate]

As part of small project i want to measure temperature of the distant star on basis of optical observations. so by what exact method i can do it? which instruments will be necessary? what is the ...
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2answers
136 views

Accurate way to programmatically generate a main sequence star?

I am working on a (personal) programming project, part of which involves generating random stars and their parameters. In order to create a procedurally generated star, I want to randomly select as ...
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1answer
37 views

Naive star filter visible at night in certain country

I have a HYG catalogue and I'd like to filter out stars visible at night and in Europe. Doesn't have to be exact. I was assuming that it'll be all stars with positive declination, but I wasn't sure ...
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2answers
206 views

Are there a lot of collisions between stars in the core of the galaxy?

I'm reading on Wikipedia about Halo Stars that orbit the center of the galaxy at a high inclination away from the plane of the Milky Way. It seems that at some point, these stars must dive back into ...
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4answers
154 views

Burning Out Stars

In the book "A Really Short History Of Nearly Everything", I read that the larger the star is, the faster it burns itself. Whys that? Wouldn't there be more energy to burn if it's larger, and just be ...
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1answer
58 views

What is the physics of a gas mass subject to gravity in space?

There are many formulas for atmospheric pressure on earth, but how does gas behave in free space? I am thinking about why stars form. I am guessing that the gas density will influence pressure, as ...
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1answer
94 views

Is there a flaw with the newer purposes and correlations attributed to the HR diagram? (And would a third axis of mass correct the enclosed flaw?)

When I was younger, I was looking at HR diagrams, and began to experiment with the HR diagram. I was looking at plotting different groups of stars on the HR diagram when I found RV Tauri stars. ...
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1answer
63 views

Formation of stars

How are stars formed? I read somewhere that when dust, gas, rocks etc come close to each other due to gravity, slowly and gradually build up a lot of pressure and form stars. If what I read is ...
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2answers
176 views

Statistically, what would the average distance of the closest black hole be?

The closest confirmed black hole is several thousand light years away from earth. Our galaxy has about 100 billion stars. I didn't find any reliable information on the black hole count of ratio versus ...
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2answers
52 views

Stars in star clusters in SMC and LMC

Is there any catalog or any paper published in any journal that enlists the stars discovered under which ever star-cluster of Small Magellanic Cloud (SMC) they belong to? There is one for Large ...
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2answers
103 views

How many stars are visible to naked eyes around Equator area?

In the best sky conditions, we can see about 44,000 stars in the sky. But what if I am located around Equator area? How many stars I can see? From what I know, the number of stars I can see should ...
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1answer
58 views

Distance of extra-galactic Classical Cepheids

There have been many questions and answers about finding the distance of a star from the earth. But as I did some research on the net, I found that we have specific approaches for finding the ...
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1answer
106 views

Is it safer to be near a star or a black hole?

If a star or black hole neared the solar system, which would do the least damage? For the sake of a good comparison, lets assume the candidate star is an "average" 5 solar mass star, and the black ...
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4answers
168 views

Where can I find a catalog of all stars in the Milky Way?

Is there a catalog of all known stars or brightest stars in our galaxy? Preferably with some sort of galactic coordinates instead of just night sky coordinates (right ascension, etc.) I'm trying to ...
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2answers
113 views

Is the Sun homogeneous?

Does the Sun have the same composition and density everywhee within it? How does it vary in other stars?
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1answer
168 views

How often do stars pass close (~1ly) to the Sun?

Interstellar exchange of massive objects is difficult across several light years. But as the stars orbit the galaxy the distances between them change. I don't find data for neighbor star distances ...
3
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1answer
60 views

Does Tobler's First Law of Geography Apply to Star Composition?

There is a principle in Geography called Tobler's First Law of Geography which states that "Everything is related to everything else, but near things are more related than distant things." Does this ...
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2answers
66 views

What is the difference between LMC and SMC?

Apart from the obvious difference as suggested by their names that the Large Magellanic Cloud is 'larger' than the Small Magellanic Cloud, what are the other differences between them? Do give all the ...
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2answers
96 views

Why do we think that there is no two-solar-mass black hole?

We think that the mass boundary between neutron stars and stellar mass black holes is around three solar masses. The maximum mass of the neutron stars now is two solar masses and we may find a 2.6 ...