Questions tagged [astrophysics]

Questions involving the physics of the universe, especially the nature of astronomical objects, energy fields, and/or regions, rather than their positions or motions in space.

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1answer
50 views

Comparing Star Formation rate in different galaxies

I was looking for some scale to compare my result of star formation rate in order to find out whether it is moderate or high or low, but I couldn't find any scale. Is there any paper related to such ...
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2answers
159 views

The creation of comets

How are comet and meteors made, and what causes them to travel through space so fast? I have tried researching, but I decided this was the faster way.
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1answer
373 views

How to find the distance between two galaxies from ra and dec and redshift [duplicate]

I have ra and dec and corresponding redshift of galaxies. I would like to calculate the distance between two galaxies. I did like this to find the nearest neighbour galaxies. Suppose I am trying to ...
3
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1answer
102 views

Type II supernovae as a distance indicator

Could someone explain in brief exactly how type II supernovae could be used as distance indicators? as in simply the formulae used and how they are employed? I know there are certain methods based on ...
3
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1answer
342 views

What if a primordial black hole went through the Sun?

How much mass would the Sun lose to a primordial black hole that (initially) has 10 Earth masses, passing through or close to the center of the Sun at solar escape velocity? How massive would the Sun ...
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1answer
46 views

redshift in astrophysical plots [closed]

Why do astrophysicists often use redshift in plots? Why it is important to know how an astrophysical object evolves in function of redshift? I was seeing an "cosmological time per redshift ...
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0answers
25 views

Constants of three body problem(2 fixed centers)

I was solving two fixed centers problem and got answer in quadratures. After that i want to find constants of motion. First one is full energy - E. Second is $p_{\varphi}$. And third one comes from ...
3
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2answers
104 views

Was there ever a meteorite with a measurable gravity?

Did we ever find a meteorite (a meteoroid that has fallen down to Earth) whose mass, density and gravity were high enough to demonstrate their gravity similar to the Cavendish experiment, so that ...
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1answer
92 views

How does a planet-sized robot standing on a planet affect its gravity? [closed]

I originally asked this at the sci-fi exchange but was told it was off-topic as it was about real-world science. Here is a picture of Unicron standing on top of the planet Cybertron, as written by ...
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26 views

Where can I find galaxy spectra (in the form of FITS files)?

I know there's SDSS and I tried searching for the spectra through the navigate and explore tool under CAS as well as by using RA/Dec coordinates under SAS, but every single time it comes out with 0 ...
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2answers
156 views

Why is a black hole's Hawking radiation temperature inversely proportional to its mass/size?

As a black hole shrinks in volume and mass, shouldn't its temperature get lower? Shouldn't it evaporate more slowly? Naively, (very naively), I think that with a smaller surface area (as per its ...
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2answers
104 views

Unit problem regards to proton

In a textbook, we have an example: The density of matter in the interstellar medium is of order one proton per ${\rm cm^3}$, then the total mass of the interstellar medium is of order (The $10^6$ ...
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1answer
35 views

How can I know the source size using the spectrum variability?

When reading some astrophysical papers I saw things like this: The sources are variable on very short timescales, implying a compact emission region. How can we conclude or measure the source size, ...
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2answers
174 views

Why carbon is considered volatile?

Carbon is considered volatile by planetary science, eg Moon lacks volatiles and thus lacks carbon. However volatiles are defined as "elements or substances with low boiling point", but ...
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1answer
173 views

Gamow Energy, Peak, Width and Window?

I am trying to wrap my head around Gamow energy and it’s various terms. To put it simply I understand higher Gamow energy reduces the chance of penetration relating to the Coulomb barrier. For the ...
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1answer
86 views

Where can I look up assigned origins of gamma ray bursts events? (GRBs)

Gamma ray burst GRB170817A is believed to have originated from the merger of Neutron Star(NS)-Neutron Star(NS). From this article on the associated gravitational wave detection GW170817: The ...
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36 views

Setting specific CENTER coordinates coordinate in SWARP

The SWARP Documentation specifies that we first set the CENTER_TYPE to MANUAL and then in the CENTER parameter we specify either one of the equatorial coordinates (RA, Dec). This is specified in the ...
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1answer
95 views

Gift for 16 year old Aspiring astrophysicist,,,,

I'm an outsider here, so please bear with me. I have a 16-year-old nephew interested in the field of astrophysics and am looking for a birthday gift. I had thought about a book on astronomy, but don'...
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2answers
113 views

Can a pulsar also be a magnetar?

I know this is a simplistic question, but I cannot find a straight answer... Also, is it possible most or all neutron stars are magnetars and/or pulsars? It's just hard to see all of their properties ...
2
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1answer
254 views

What is the 'scale factor' equation for a dark-matter dominated universe?

The Friedmann equations can be solved exactly in presence of a perfect fluid with equation of state $${\displaystyle p=w\rho c^{2}} \qquad p=w\rho c^2$$ where ${\displaystyle p}$ is the pressure, ${\...
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0answers
19 views

Do apparent magnitude (V) and photometric magnitude (specifically in optical V band between 500-600 nm) have a similar scale to stellar magnitude?

I'm graphing a table and I used the magnitude values from this database https://vizier.u-strasbg.fr/viz-bin/VizieR-4 (It's the V/19/data catalog for "Masses and Ages of stars in 68 open clusters&...
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1answer
49 views

photon gas pressure and Independence on refraction index

Brief context: when studying Stellar Structure one of the main goals, aside of determining equations that describe quantities of interest of the system, is to also determine equations of state that ...
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1answer
45 views

What is a UBV source for stars or stellar objects?

I was using the V19(VizieR) catalog and the main identifier of the stars was in terms of an 'ID' number which they mentioned as being 'Star number in UBV source' I have no idea what that means. How ...
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2answers
81 views

How far away are objects whose light will never reach us, because of the expansion of the universe?

I thought I had read this question on Stack Exchange before, but now I cannot find it... In fact, I thought I had posted this question before, somewhere, on Stack Exchange... I believe the answer ...
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1answer
118 views

What measurements helped us in understanding 'Oumuamua's location and speed?

What measurements helped scientists understand 'Oumuamua's location and speed? I wanted to know how it was achieved and with what accuracy if possible.
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1answer
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Are the most distant known objects in the universe more than 14 billion light years away? [duplicate]

When I hear about the most distant objects in the universe, such as the recently discovered galaxy GN-z11, their distances are usually stated to be a little under 14 billion light years away.... But, ...
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3answers
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How do scientists know that the distant parts of the universe obey the physical laws exactly as we observe around us?

How do scientists know that distant parts of the universe obey the physical laws exactly as we observe around us? The question might look a bit odd but I am really stuck on my head. We know, ...
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1answer
120 views

How to isolate H$_\alpha$ from Nitrogen doublet emission lines

I am trying to find out line intensity and FWHM of H$_\alpha$6565 emission line from a quasar spectrum obtained from SDSS DR-14Q. Visual inspection of spectrum shows H$_\alpha$ being contaminated with ...
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0answers
70 views

Is the Universe infinite? [duplicate]

https://en.wikipedia.org/wiki/Universe Is the Universe infinite or finite ?
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2answers
102 views

What is the difference between these various Angular Resolution formulas?

I have recently learned about angular resolution and its dependence on the ratio λ/D. There seem to be three different equations for angular resolution that I have come across. One of these has the ...
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2answers
978 views

Problem regarding the absorption lines of the sun

Some of the wavelengths of light that are emitted from the sun will be absorbed by atoms in the outer layer of the sun and also the atmosphere of the sun, and we see this as absorption lines in the ...
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2answers
186 views

Why is molecular hydrogen (H2) so difficult for astronomers to detect?

I am reading a great deal about the various forms of hydrogen throughout the universe, and I keep reading that 'molecular hydrogen is notoriously difficult to detect', and other sentiments along those ...
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1answer
130 views

Is most hydrogen in the universe in the form of plasma, atomic neutral hydrogen, ionized hydrogen, or molecular?

I have had trouble finding an answer somewhere.... Some places say most hydrogen is plasma, such as the stuff stars are made of (mostly) and the 'warm-hot intergalactic plasma'. Other places say ...
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1answer
113 views

Fraction of initial mass lost (radiated) by neutron star mergers compared to black hole mergers?

GW190521 black hole merger total mass calculation and missing mass, how does this happen? notes that there are about 9 solar masses missing from the final black hole. GW170817 is the first observed ...
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2answers
152 views

Do the neutrons in neutron stars emit the radio waves?

Neutrons can, especially in extreme circumstances (and large concentrations) emit electromagnetic radiation. I specifically asked about this in Physics S.E. Has a free neutron ever been shown to ...
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3answers
614 views

Moving from mathematics to astronomy/astrophysics

I'm currently studying for a PhD in pure mathematics (the topic is the cohomology of differential graded categories, just to give you an idea of how pure I mean), although the first year of my ...
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1answer
108 views

what is the difference between luminosity distance and distance?

This is a very basic question but I am little confuse the difference between luminosity distance and distance. Can anyone tell me that what is the difference between luminosity distance and distance?
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1answer
100 views

What will "the Earth being consumed by the Sun" look like?

Sometime soon (astronomically speaking) the Sun will, as a main sequence star, expand into a red giant and, potentially, "consume the Earth". If we take it as read that the surface of Sol ...
2
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1answer
54 views

Apparent Centering Problem When Using the Perifocal System to Draw Orbital Ellipses [closed]

I am attempting to render orbital ellipses in software. Given a set of orbital elements, I am using the Perifocal system to determine a set of points along the curve of the ellipse. I am using the ...
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0answers
100 views

How do magnetic fields mess with astronomers' observations?

Does anyone else watch 'Dr. Becky' on YouTube? Her March 'Night Sky News' video, subtitled 'The biggest black hole burp, a wobbly Milky Way & Betelgeuse is brighter' says that... "Dust and ...
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1answer
4k views

Why are there no gamma-ray bursts detected in our galaxy?

I found from Wikipedia and other sites that there are no GRBs detected in the Milky Way. Can someone give a feasible reason for that? Why are there no GRBs detected in the Milky Way galaxy?
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1answer
78 views

how to find the approximate [stellar radius]? (distance from center to most distant star) of a circular flat disk galaxy based on its stellar mass?

I'm doing a high school programming project on drake's equation (simple galactic model) and wondered if there was a (simplified) way to find the radius (measured by the distance between the center and ...
2
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1answer
315 views

Why is the number of Long Gamma Ray Burst (LGRB) event occurrences greater than the number of Short Gamma Ray Burst (SGRB) event occurrences?

I collected from NASA this histogram plotting the number of GRBs vs the duration of GRBs. Now my question is, why is the number of Long Gamma Ray Bursts (LGRBs) events occurrences greater than the ...
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1answer
82 views

Why is the peak value(s) of the spectral radiance of the CMB different if you calculate with freq. instead of wavelength?

On Wikipedia, the calculated value of the peak frequency of the cosmic microwave background is 160.23 GHz, but it says if you do the calculating with wavelengths, then convert to frequency, you get a ...
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30 views

What was the energy/wavelength/frequency of the CMB when first emitted/released?

Given the z redshift of 1089, and the temperature difference between then and now of about 1089, I tried scaling the ev, freq. and wavelength by 1089.... Is that right? I get a freq. of about 240 ...
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1answer
3k views

Have I nearly found the event horizon of a black hole?

The calculator on the website https://planetcalc.com/1758/ cites Wikipedia's Gravitational acceleration and implements: $$g = G \frac{M}{(R + h)^2}$$ For a black hole with mass $M$ equal to 5 solar ...
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0answers
47 views

Ideas for a project in astronomy and deep learning [duplicate]

I am currently pursuing computer engineering and am in my senior year. I'm looking for a long term project (ideally 2-4 months) in astronomy and deep learning. I have extensively worked on the Galaxy ...
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0answers
31 views

Demonstration of scales for the two components (transverse and perpendicular) of Baryonic Acoustic Oscillations (BAO)

I transfer here a post that has not had any answer pn physics exchange, so I am going to delete this latter. Maybe I will have more luckiness here. In an astrophysics context about BAO (Baryonic ...
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0answers
33 views

How thick are the intergalactic filaments?

Recently, in October, news came out about the faint intergalactic filaments finally being 'found'. Then, in June, astronomers announced that these things had enough normal matter in them to solve the '...
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1answer
2k views

Why don't (or can't) stars be more than 325 or so times the mass of the sun? What limits their size?

Is there a particular reason why stars cannot grow as massive as they want to? And why doesn't this limit apply to supermassive black holes?

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