The methods and techniques for gathering astronomical data, as well as the limitations thereof.

learn more… | top users | synonyms

3
votes
1answer
133 views

What is the average mass of galaxies according to Hubble Deep and Ultra Deep field observations?

It is very widely known among people interested in astronomy that there are 100-400 billion stars in the Milky Way galaxy and there are ~ 100 billion galaxies in the observable universe, which is ...
5
votes
0answers
43 views

Cosmic rays and neutrinos

I'm reading Gaggero's Cosmic Ray Diffusion in the Galaxy and Diffuse Gamma Emission and he makes the claim, ...the definitive proof of [Cosmic Ray proton acceleration in supernova remnants] would ...
12
votes
3answers
823 views

What is the most compelling evidence of General Relativity in the presence of matter and energy?

The most oft-cited triumphs of GR are things such as the shifting perihelion of Mercury, gravitational redshift experiments, and gravitational lensing. But, as far as I know, these are only ...
5
votes
2answers
88 views

What is the area of the sky that is covered by the Hubble Ultra Deep Field image?

I have found two different numbers for the area of the sky covered by the Hubble Ultra Deep Field (HUDF). According to this, the image is roughly 2.4 arcminutes wide. The image is also attached to the ...
5
votes
3answers
257 views

What does this stellar mass distribution mean?

According to this pie above and for the "Red Dwarfs" part, which of these is correct : 1) 41% of the stellar mass of a galaxy is in stars with masses < $0.25$ $M_{\odot}$ or 2) 41% of the ...
0
votes
1answer
64 views

Is there a confirmation of dark matter signal?

Dark matter, as we know does not emit light, so confirmation of its presence is indirect. Are there any recent indirect confirmations of dark matter. A place one would look for in detecting dark ...
1
vote
0answers
21 views

If we increase the aperture of a telescope and decrease its magnification, can it be harmful to the eyes?

The full moon is the brightest object in the night sky. I believe that if we increase the aperture of the objective, and decrease the magnification of the telescope, it might concentrate a dangerous ...
5
votes
1answer
42 views

According to the initial mass function, should there be more brown dwarfs than red dwarfs?

According to the IMF and the stellar mass distribution, stars become more abundant the less massive they are. And while objects must have a mass > 0.075 solar mass to become a star, brown dwarfs with ...
6
votes
2answers
474 views

What is the luminosity of the Milky Way galaxy?

The luminosity of the Milky Way galaxy according to this is $5\times10^{36}$ Watts, but this number suggests that there are about 10 billion stars with Solar luminosities in the Milky Way, which ...
0
votes
3answers
136 views

How far has a 13.7 billion year old photon travelled

I've read that the size of the observable Universe is thought to be around ~46 billion light years, and that the light we see from the most distant galaxies were emitted ~13.7 billion years ago as a ...
1
vote
1answer
31 views

Mass of NGC 1097 Galaxy

I've been looking all over the internet for this and can't seem to find a reference. Can anyone refer me to a paper citing the mass of NGC 1097 based on luminosity?
5
votes
1answer
52 views

What fraction of baryonic matter is in stars?

We know from big bang nucleosynthesis that baryonic matter accounts for about 5% of the universe's total mass-energy density. What is the current best estimate of how much of this is in the form of ...
0
votes
0answers
15 views

Synthesising types of galaxies using various stellar spectra

I have been given the task of synthesising an elliptical galaxy, a starburst galaxy and a spiral galaxy (considering the arms and the bulge separately and adding them) using stellar spectra which I ...
2
votes
1answer
57 views

How the distance and diameter of the stars are experimentally measured?

How to measure the distance of a star and the diameter of it from earth based tools? Normally we can measure the angle between the stars edge. But diameter or distance needed to measure the other ...
1
vote
1answer
25 views

Interferometry works as a filter

I attended an astronomy seminar the other day and though I did not pick up much as it was on data collection etc, I did take away one sentence: "Interferometry works as a filter" Now I know what ...
5
votes
2answers
114 views

How do we estimate $10^{23}$ stars in the observable universe?

Now, I read somewhere, that there are $10^{23}$ stars in the observable universe. How did scientists estimate this?
0
votes
1answer
76 views

Do septuple (7), octuple (8) or nonuple (9) star system exist?

The highest I found so far is Castor, a sextuple star system. And there doesn't seem to be any other sextuple star system within at least 100 light-years...
1
vote
0answers
39 views

Do the different observed Type Ia supernovae have similar explosion energy?

I have been trying to read about the energetics of observed supernovae for some time. And while the observed core-collapse supernovae have many scientific papers about them trying to estimate the ...
1
vote
1answer
22 views

Optical interferometers resolution

I found this interesting list of optical interferometers: http://en.wikipedia.org/wiki/List_of_astronomical_interferometers_at_visible_and_infrared_wavelengths But I can't understand which is the ...
0
votes
2answers
64 views

A question concerning the act of observing distant galaxies

The comoving radius of the observable universe is currently put at $46$ to $47$ billion light years. Source wikipedia. When we observe galaxies at great distance, such as the Hubble Deep Field at ...
1
vote
0answers
64 views

Sedna, VP113 and the likelihood of the PX/Tyche/Thelistos hypotheses

The recent discoveries in exoplanetary science (specially those findings of planets orbiting far far away from its parent star/stars) raise questions about how much we know about the (true, AIU ...
2
votes
0answers
28 views

What's the evidence, if any, for some local concentration(s) of dark matter in some region(s) smaller than a galaxy?

What's the evidence, if any, for some local concentration(s) of dark matter in some region(s) smaller than a galaxy? Galactic-sized--or larger--gravitating halos seem to get all the attention. I'm ...
2
votes
2answers
128 views

Can a point source be located more accurately out-of-focus or in-focus?

Let's say I am taking a picture, and I know a priori that the image is of a single ideal point source of light at infinity. With a perfect imaging system in focus, the image shows an Airy disk. I ...
1
vote
1answer
60 views

How stellar aberration is measured?

A simple calculation shows that stellar aberration due orbital motion of earth is roughly 20 arcseconds. My questions are: Practically how this small value is measured? Does this value is in the ...
1
vote
1answer
33 views

Why is solar eclipse so important for sunlight spectrum analysis?

People wait for decades to catch the chance of a solar eclipse to observe the sun. Why cannot they do it every noon?
0
votes
2answers
81 views

The reason(s) of seasons on earth

This maybe simple and usual question, although there is a lot of confusion about it over internet and even in some books, so I want from an astronomer / astrophysicist to fill the gaps for me ...
0
votes
0answers
26 views

If the universe has a shape, what is the surface? [duplicate]

Since the idea of the universe was that it was expanding, is there a way to know the surface area of the universe like the growing 3D object it is illustrated? The idea was that the universe was ...
2
votes
2answers
115 views

How to calculate error of parallax and sextant based navigation?

First of all, why wasn't the sextant ever used for land navigation? The horizon is easier to see at sea, but land based sextants could be used in conjunction with artificial horizons (as at sea when ...
7
votes
1answer
248 views

How was this dot identified as a mystery planet originally (Pluto in this case)?

I was watching a documentary on a mission to study Pluto. At 21:11, an image is presented with an arrow mark pointing a small dot which is now identified as Pluto. As there are hundreds of dots on ...
1
vote
0answers
33 views

How is the formula derived for finding the field of view given drift time and declination of a star?

How is the formula for field of view derived given the drift time of a star and its declination? $FOV = (drift\ time \cdot \cos(declination)\cdot360 ) / 86164$
2
votes
1answer
111 views

How to practically find the RA-DEC coordinates of a star?

How are RA-DEC (Right Ascension & Declination) coordinates of a star measured i.e. if scientist spot a new star in the sky how do they accurately measure it's coordinates?
1
vote
0answers
21 views

Velocity dispersion of galaxies

I couldn't find on web how can I get the velocity dispersion and velocity maps of galaxies from the 3D data cube I get from integral field spectrograph.
3
votes
0answers
46 views

Why can't Wetterich's “Universe without expansion” be tested compared to standard cosmological redshift?

I have read on several sites that this is a theory that cannot be tested. Why is this a theory that can not be tested? It seems to me that if the mass of particles is continually increasing, then the ...
5
votes
1answer
102 views

How did Kepler arrive at his laws?

How did Kepler arrive at his laws? If one already knows the distances to the planets (and the eccentricity of the orbits etc.) it is understandable how one might proceed to establish the second and ...
2
votes
0answers
61 views

Gamma ray bursts luminosity measurement

physicists use millisecond fluxes i.e.,fluxes calculated within a very short timescale to measure the actual 1 second flux for these grbs.But to do that they have to multiply the millisecond fluxes ...
1
vote
1answer
502 views

Radians to Rotate Earth to Match ECI Lat/Lon with ECEF Lat/Lon

I am attempting to model GPS Satellite positions on the globe for a set of ephemerides. I have a verified set of ECI ( http://en.wikipedia.org/wiki/Earth-centered_inertial ) XYZ Coordinates and a ...
4
votes
0answers
76 views

Calculus used by Gauss to find Ceres' position?

With very little data, the great mathematician Gauss was able to predict the exact location of where to find the asteroid Ceres. If possible I would like a reconstruction of his work, from the data ...
1
vote
1answer
63 views

Is it possible to build an optical system that increases the perceived surface brightness?

So is it possbile to build a system from lenses and mirrors that can make faint gas nebulas brighter or can be used as nightvision? If you increase the size of the aperture of a telescope it will ...
10
votes
3answers
182 views

Milky Way Voyeurism

When and where on earth do we get the best view of the Milky Way? I believe it helps if it is night if it is winter to look in the direction of the galaxy center I think that this information ...
2
votes
0answers
70 views

To what extent are the astronomically observed black hole candidates compatible with GR black holes?

Do they all fit Schwarzschild black holes? How people compare them with more complicate BH solutions as spinning BH solutions (even if they are not known analytically), say. I'd like more than ...
4
votes
1answer
73 views

How bright was the AGN eruption at the center of the Milky Way ~2 Ma ago?

The black hole at the center of the Milky Way is believed to have erupted as an active galactic nucleus (AGN) approximately 2 million years ago, at which time it would have been visible to early ...
7
votes
1answer
176 views

What are the different ways to measure the spatial curvature of the universe?

Just what the question asks. Assuming the Friedmann-Rovertson-Walker (FRW) metric, what measurements can be performed to determine the spatial curvature of the universe.
4
votes
5answers
503 views

Could the speed of light change outside our solar system

Theory: The speed of light changes when it enters or exits the solar system due to a difference in medium (dark matter possibly). Potential problem 1: refraction If there was a speed change at the ...
4
votes
2answers
167 views

Will a telescope show a more magnified image if the object is brighter?

I have a small telescope which shows me the moon's craters a little bit magnified. Consider a situation where the moon is very very brighter than its current brightness, so that the telescope's ...
2
votes
1answer
190 views

Analyse astronomical data

Recently I was told of a job offer to analyse astronomical data. The job offer states that they want somebody with knowledge of astronomical data analysis software and it will be a plus somebody who ...
2
votes
0answers
53 views

Where can I get latest full updated list of supernovae candidates from the SDSS-II Supernova Survey?

I am doing a project where I need the list of supernovae candidates from the Sloan Digital Sky Survey II (SDSS-II) supernova survey. One list is available as part of the data-release-7 (DR7) website. ...
5
votes
1answer
64 views

Relation between brightness and magnitude

Let say we measure the superficial brightness of an object in the $B$ band, $I_{B}$ measured in $\displaystyle\frac{L_{*}}{\mbox{pc}^2}$ where $L_{*}$ is solar luminosity and $\mbox{pc}$ is parsec. I ...
1
vote
2answers
781 views

What is the highest useful magnification todays largest telescopes can offer?

I know that the maximum (useful) magnification is limited by the diffraction limit, but I was not able to find numbers for the highest useful magnification factors using modern large telescopes. How ...
4
votes
1answer
158 views

Identifying the position of the moon

I encountered the following question in a previous year paper of a graduation-based test. On a certain night the moon in its waning phase was a half-moon. At midnight the moon will be (choose one ...
3
votes
1answer
113 views

When one can make telescope that can distuingish 1 mas?

When one can make telescope that can distuingish(angular resolution) 1 mas object by angular diameter? If already possible, tell the name of telescope/observatory. How to calculate angular resolution ...