The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying of the contents of the universe in order to better understand what is out there.

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35
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4answers
15k views

Why is a new moon not the same as a solar eclipse?

Forgive the elementary nature of this question: Because a new moon occurs when the moon is positioned between the earth and sun, doesn't this also mean that somewhere on the Earth, a solar eclipse ...
0
votes
0answers
16 views

K-Correction of Photometric Data [on hold]

How do I achieve the K-correction with the Photometric data of type Ia Supernovae ? Basically, I want the corrected magnitude and following is the sort of data I have : ...
0
votes
0answers
8 views

What is the estimator that used to de-rotation of CMB polarization? [duplicate]

For de-rotation of CMB polarization we need to use of estimator for rotation angle. and used many estimator for this process.
-3
votes
0answers
44 views

Virtual particles and space inflation [on hold]

Could virtual particles be separated by fast inflation of space between them while they were created.
4
votes
1answer
48 views

Hubble time and age of the universe

I'm having trouble with the following derivation of the 'age of the universe': http://imgur.com/gRvLWX8 The parts I'm struggling to conceptualize is what a 'universe expanding' means, and also why ...
-6
votes
0answers
38 views

What are Black holes exactly? [on hold]

A Black Hole is a very large rip in the atmosphere that opens after to many shuttles have traveled into space. It happens after about 5 million years of shuttles traveling in and out of spaces ...
0
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2answers
38 views

The impact of the Oort cloud to change the barycenter of the solar system

Is the Oort cloud changing the position of the barycenter of the solar system? Does it affect in a significant way? How significant?
0
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0answers
13 views

what are the historical reasons that people have made to explain eclipses? [on hold]

I basically want to know the causes that people gave in order to explain eclipses. For example some tribes thought that gods "sent" eclipses as punishment. I need an article (from a reliable source) ...
0
votes
0answers
93 views

Solar time correction due to longitudinal difference

I've been always calculating the correction in solar time due to difference between observer's meridian and the meridian on which the local standard time is based using the following formula "Design ...
3
votes
2answers
29 views

Different width of spectral lines for different groups of stars

As seen in an HR-diagram, a certain stellar classification can correspond to more than one group/sequence of stars (G5 could for instance be either a giant, main sequence star or a white dwarf and so ...
11
votes
4answers
2k views

Names, maps for Milky Way dust clouds? (Dark Cloud Constellations)

There is a nice image of the Milky Way, labeled with constellations, at 360°x45° panorama with constellations: It leads me to wonder how much we know about the Great Rift, Coalsack and other ...
1
vote
0answers
37 views

Calculating the Diameter of Jupiter through Image [on hold]

I was trying to calculate the diameter of Jupiter from a picture I took of it. Here's the information I was able to get that I needed to calculate the diameter: Focal Length of Telescope: 1.2 m ...
-1
votes
0answers
36 views

Physics Calculation Tool [closed]

I have many images like the following: As many of you may recognise, this is a picture of Jupiter and its four Galilean moons. Using these images, I am aiming to calculate the mass of Jupiter by ...
-1
votes
1answer
76 views

Can you see yourself in space? [closed]

Can one see them self in space if no near by star was in view? Is there enough star light to read once your eyes adjust?
1
vote
1answer
25 views

Gamma Ray Burst data

I wanted to know if there was some database for gamma ray burst (GRB) data. I would like to get the luminosity and duration of recorded GRBs. So far, I have come across this website, but since I do ...
-7
votes
0answers
55 views

Concrete and Relevant Usage of Most Digits of Pi [closed]

I have recently come accross the fact that no concrete usage of pi exists in physics to an accuracy better than 39 digits of it. 39 digits would get us an accuracy better than that of a hydrogen atom, ...
1
vote
1answer
28 views

The observation of changes barycenter of the solar system

Is it possible to observation changes in the barycenter of the solar system? There are graphics showing changes barycenter but they are made on the basis of computer simulation (E.g.: here and here). ...
0
votes
0answers
40 views

Is there any evidence of black holes existing? [duplicate]

Yes, I am aware of observations of "massive objects", for example near the center of the galaxy. But is there any evidence that the object in question is a black hole, with all its commonly attributed ...
-1
votes
0answers
24 views

How to de-rotate the cosmic microwave background polarization?

the polarization of CMB is rotated by effect of cosmological birefringence. then to remove this rotation of polarization, we need to de-rotate this polarization. but I know about this de-rotating ...
7
votes
2answers
111 views

How are stellar and galactic ages determined?

Being a 4th year undergraduate physicist, you'd think I'd know this! But it's never really taught in any detail, just vague mentions of metallicities and, in galactic case, redshift. So how exactly ...
1
vote
1answer
25 views

Stellar classifiaction and metals

I have recently started to study astronomy and there is a thing with stellar classifications I can't get my head around: The colder the star the more absorption lines from metals are present in its ...
0
votes
0answers
25 views

Blurry image in a Celestron 8SE

We have a Celestron 8SE. Last night we were looking at the quarter moon. The moon was in focus. We switched viewers & 2nd viewer only saw a blurry white blob, not the surface of the moon. When ...
2
votes
2answers
124 views

Seeing the shadow of a black hole

Why can't we see the shadow of a black hole cast on Earth. Shouldn't the black hole block some light from a star or a galaxy far behind as they line up?
2
votes
0answers
39 views

Would a black hole cast a shadow? [duplicate]

Okay, so I've been wondering and this is a simple question and I cannot find an answer anywhere. Would a blackhole the size of the Moon (event horizon) black out the Sun in a "Lunar eclipse"? My ...
0
votes
3answers
2k views

What can be seen with a 114mm Aperture 675x Zoom Telescope?

I choose to post this question on the physics exchange seeing there would be a bigger audience for answers than the astronomy exchange still in BETA. But i'm looking to buy a telescope and was ...
0
votes
1answer
43 views

Are planets and galaxies being discovered from earth?

I wonder how new planets and galaxies can be discovered from earth. I mean, there are not inifinately many directions to look with the telescope, right? Is it really so many different directions to ...
1
vote
1answer
42 views

Surface brightness

I have to compute the surface brightness as a function of the radius from the following set of data: {right ascension ($\alpha$), declination ($\delta$), magnitude (m)}. I also know the center of the ...
2
votes
0answers
28 views

Boötes Void numbers, 2016

As a general science (hence Wikipedia!) reader, the latest information I have is that 60 galaxies have been found and counted inside the Boötes void, this of 1997. (1) What is the latest count of ...
0
votes
0answers
29 views

Is it possible to approximately know the wattage/luminosity of a lamp knowing distance and using a DSLR?

I'd like to know if it is possible to approximately know the wattage/luminosity of a lamp knowing distance and using a DSLR (digital single lens reflex camera) mounted on tripod. Maybe, when shooting ...
7
votes
0answers
45 views

Are there any models for distribution of asteroid sizes in a belt?

Question: Is there any function that can describe the distribution* of asteroid diameters expected within an*' asteroid belt? *: distribution as frequency of occurrence within the asteroid belt or ...
0
votes
1answer
43 views

Calculating the diameter of Jupiter through an image

I took an image of Jupiter through my 8" Dobsonian Telescope, attaching a DSLR and a 1.25" Barlow Lens where the eyepiece goes, as shown in this video: https://www.youtube.com/watch?v=reFxoF3XoaU ...
4
votes
2answers
65 views

A question about the Fermi acceleration

In high school physics, we know that a charged particle cannot gain energy from a magnetic field. But, it seems that in the so-called Fermi acceleration, the particle is accelerated by the magnetic ...
0
votes
2answers
60 views

Cosmic Scale Factor $R$ and redshift

I'm slightly confused by an idea of redshift: If we assume the distance between two points is given by: $$d = R Δx$$ we can assume that $$λ_0 = R_0 Δx$$ And when we receive the emission it will ...
1
vote
1answer
52 views

Mathematically calculate if a Planet is in Retrograde

How do you mathematically calculate if a Planet is in Retrograde when you are given both the Earth and the Planet Keplerian Elements value and rate? Keplerian Elements are: a - Semi-Major Axis; e - ...
0
votes
0answers
37 views

Can we calculate the point on Earth nearest to the Moon?

We have the ability to calculate the Moon's orbit in order to predict Lunar and Solar eclipses precisely. Using our known calculations of the Moon's orbits, can we calculate the closest point (city ...
11
votes
2answers
6k views

Cameras in Voyager probes

I've always wondered about the cameras in the space probes, especially in the Voyagers. 1) What kind of cameras do they have? Digital? (What kind of sensor and megapixel count?) Analog? (Do they ...
4
votes
1answer
50 views

Will stars disappear from the sky when their particle horizon is outside the event horizon

Given that the universe is expanding at an accelerated rate, will there be a point where stars visible in the night sky will simply disappear from view when their particle horizon is outside the event ...
9
votes
4answers
2k views

How many percent of the visible light reaching the Earth are from other stars than the Sun?

How many percent of the whole visible light reaching the Earth are from other stars than the Sun? Is it maybe 0,5 - 1% or is my guess already too much? I am interested mainly in visible light, but ...
1
vote
1answer
29 views

What is meant by the point-source response of eye or telescope?

I have heard that a source is called unresolved if it is much smaller in angular size than the point-source response of the eye or telescope observing it. What is the meaning of point-source response ...
5
votes
1answer
68 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 ...
0
votes
2answers
43 views

Distances between stars and their sizes

At the begining I wish to apologise for naive question, but one thing puzzles me. Let's say we observe two stars that have average brightness. One can easily see that they are not points, but those ...
4
votes
2answers
61 views

Why is the distribution of Cosmic Rays isotropic?

We observe that cosmic rays (CRs) are isotropic on the sky, i.e. they come from all directions with no apparent preference. I understand this is related to the deflection of these CRs by the magnetic ...
2
votes
2answers
50 views

Finding the remnants of recent supernova explosions in the solar system's neighbourhood

I just found an article, Long-Ago Supernovae Littered Earth, which reviews evidence presented in The locations of recent supernovae near the Sun from modelling 60Fe transport; D. ...
0
votes
1answer
43 views

Why are there more meteorite falls during April?

I was reading this article about the Nov 2015 Fireball surge. One explanation was that "... gravitational forces from Jupiter causes the Taurid meteor stream to be more heavily concentrated near Earth ...
0
votes
2answers
32 views

Why can't we detect the Earth's orbital motion when looking at the sky and stars?

After I read that speed of earth orbit around the sun is 30 km/s, I looked at sky and I didn't notice any change when compared to the start location. 30 km/s can be converted to (30 * 60 ) km/minute ...
1
vote
0answers
29 views

Light pollution and visibility of Milky way [closed]

Say, 1000 years ago, when there was (almost) no light pollution or air pollution, would the milky-way galaxy have been visible at night, anywhere on Earth?
4
votes
2answers
3k views

Density of stars near the center of the Milky Way

At night, I can look up and see the Milky Way across the sky. My question is, supposing our solar system was, instead of way out on an 'arm' of the galaxy, if we were near the galactic center. Would ...
1
vote
1answer
39 views

Why don't stars re-emit the photons they absorb, thus restoring a continuous emission spectrum?

If you shine white light through a gas, electrons can absorb sufficiently energetic photons to reach higher excited states. This produces gaps in the spectrum and it's how Helium was discovered. So ...
3
votes
1answer
39 views

What causes damage to interference filters?

I am currently working on a UV detector meant to be mounted on a CubeSat satellite. To select the bandwidth, I consider using an interference filter placed between the detector and the source. ...
9
votes
2answers
675 views

What are the demographics of stars visible to the naked eye?

Of the stars that can be seen with the naked eye, what are the distributions of each type? For example, how many are main sequence? how many are Super Red giants/white dwarfs/neutron stars...etc. ...