0
votes
0answers
33 views

Does Triton trigger the active atmosphere of Neptune?

As we know the atmosphere of Neptune looks more active than Uranus', is this due to the tidal forces caused by the retrograde orbit of Triton around the planet?
1
vote
3answers
672 views

How can the universe be infinite?

I've heard from renowned astrophysicists that we don't yet know whether or not the Universe is infinite. How is that possible regarding the big bang theory is accepted (as they all do)? Are they ...
3
votes
2answers
196 views

Is there a limit to how hot an object an get?

Temperature is a measure of the average kinetic energy of particles in a given place (correct me if I am wrong) so there must be a definite limit to heating like there is an absolute zero to cooling. ...
5
votes
1answer
51 views

Population of excited H levels in a Strömgren Sphere

In chapter 2.2 of Astrophysics of Gaseous Nebulae and AGN Ostriker and Ferland claim that, as far as ionization is concerned, one can assume all atoms to be in the ground state in a Strömgren Sphere ...
0
votes
0answers
43 views

Is our universe expanding? [duplicate]

Is our universe is expanding or contracting. And if it is doing so then what is the basic principle behind it. Is it related to the net energy of the universe or something else.
1
vote
1answer
50 views

UTC to UT1 time corrections

Astronomic observations in geodesy. It is well understood that sun and star positions may be expressed in Greenwich hour angle and declination. Or Right Ascension Declination. And may be published ...
9
votes
9answers
2k views

What's the largest non-spherical astronomical object in the universe?

Some asteroids and comets are non-spherical. But is the nature of big things and gravity so that large things in the universe are always spherical? What is the biggest astronomical object in terms of ...
1
vote
2answers
84 views

Higgs Bosons in the centre of Black holes or extremely large stars [closed]

With the discovery of the Higgs Boson as the mass carrier, what is the possibility at the centre of a black hole being so dense and gravity so infinite that the structure of a proton or neutron are ...
1
vote
2answers
129 views

Calculate time when star is above altitude 30°

To find the best observation time for an object, I'd like to calculate the time when it is 30° or more above the horizon. Local Sideral Time would be sufficient. To include that in my program, I need ...
5
votes
1answer
73 views

Oscillation in tilt of the solar system

I know that the solar system is tilted 62.6° to the plane of the galaxy. I'm curious whether this angle changes over time, and what are the extents and time frame of any such oscillations if they ...
3
votes
1answer
33 views

Are there currently observed systems of close (narrow) binary brown dwarfs?

All over the Universe, there are (gravitationally bound) binary star systems. Considering the huge number of brown dwarfs, are there currently known double systems of gravitationally bound binary ...
1
vote
2answers
519 views

Definition of stellar core?

This is a basic question, but I may as well ask it. I had always thought that the core of a main-sequence star is defined as the part hot enough for nuclear fusion. Some dictionaries seem to agree ...
1
vote
1answer
44 views

What kinds of stars would it be possible to observe in M31 with a small amateur telescope?

I was wondering what kinds of stars would be visible in M31 and other nearby galaxies using a moderate (~8") telescope and a CCD camera. This would be a limiting magnitude of around 17. I have heard ...
0
votes
2answers
162 views

Question about space-time

In the Big Bang model of the Universe, every observable thing is thought to have expanded very abruptly from a point of infinite density and zero volume. However, the problem with this assertion is ...
2
votes
1answer
131 views

Is the Sun slightly blue in the center? - Wavelength-dependent limb darkening of the Sun

I've slightly modified the title to try to attract some attention. If we call sunlight "white" and limb darkening is a result of seeing deeper at normal incidence and shallower at oblique incidence, ...
3
votes
1answer
21 views

What is the magnitude of variation of Earth's orbital inclination?

Please excuse if this has been asked and I just didn't find it. I have found several references that indicate that the inclination of Earth's orbit varies over a period of ~70,000 years, but I can't ...
0
votes
1answer
58 views

Would the (orbitting) speed of the earth change if suddenly the sun disappear and the earth is thrown into space?

Usually an orbit is considered as an acceleration. So fe the earth has a speed of about 100.000km/h around the sun. Now I think there is some relativity involved, so from which point of view shall we ...
0
votes
1answer
113 views

Can a star eject a liquid or a gas that has not been ionized?

Can a star eject a liquid or a gas that has not been ionized? I am implying that these gases could be a source of reusable energy.
1
vote
1answer
102 views

What is 'Dark Fluid'?

Is this term official jargon/wording for 'Dark Matter'? If so, why include the word "Fluid" if there is supposedly no viscosity in actual space. It would be like saying 'Hey, want to go swim in my '...
8
votes
2answers
157 views

What's the distinction between “planetary formation mechanisms” and “gravitational collapse”?

As I was curious about the exact identical comment to my title here: http://astronomy.stackexchange.com/a/16135/10102 And as it seems no one asked it yet, I'm simply interested in the difference of ...
0
votes
2answers
108 views

Could asteroid mining affect gravitational balance?

I'm just a guy who is interested in all topics around space, so forgive me if it is a dumb question. I have read some things about asteroid mining in the past and I think it's a really interesting ...
6
votes
4answers
184 views

How did the Earth come to be in orbit around the sun?

I'm not sure if this post should be in the physics subject forum, but this seems to fit here too. I have been reading a book about chemistry and how the universe came to be with the theory of stars ...
3
votes
1answer
48 views

Does the summit of a small mountain offer better seeing?

I have a small amateur telescope, and would like to defeat the atmospheric seeing conditions as much as is possible. Fortuitously, I happen to live fairly close to this lovely patch of bare elevated ...
1
vote
1answer
45 views

Pointing direction movement of a fixed camera

first doubt here: I have a fixed camera, whose coordinates I know, pointing to the sky. After the first image, I performed a astrometry calculation from nova.astrometry.net and I got, among other ...
6
votes
5answers
181 views

How cold is interstellar space?

The vastness of space brings me a sense of chilliness even though I have never experienced it, although I wish to. Just how cold is interstellar space (on average)? How is this even measured? I mean ...
1
vote
0answers
56 views

Theoretically could the expansion of the universe affect acceleration due to gravity?

I was wondering if theoretically the universe expanding affects speed or acceleration due to gravity, compared to if space weren't accelerating. The way I have it in my head, something is falling ...
1
vote
1answer
64 views

uses of coordinate systems

Wikipedia describes the five following celestial coordinate systems each with rectangular/spherical variants: horizontal equatorial ecliptic galactic supergalactic What are the practical preferred ...
1
vote
1answer
60 views

Eclipse — Solar and Lunar

Q. Why is solar and lunar eclipse not seen from all parts of the earth at the same time? I think its because of the revolution of the earth but i am not sure. I want a more reliable answer.
0
votes
1answer
38 views

What other “planetary formation mechanisms” exist beyond “gravitational collapse”?

My curiosity was pricked by the an edit made to this post: What other "planetary formation mechanisms" exist beyond "gravitational collapse"? sadly the edit was changing the ...
0
votes
1answer
41 views

How to calculate the pixel size and beam size of an image?

I have an image with some sources in it. I need to get the pixel size and beam size of that image. How can I calculate it?
0
votes
1answer
52 views

LLR & Orbital Motion

As I understand it, light that is emitted from a source is not imparted with the motion of the source and so always follows a "straight line". If this is correct, I am having a difficult time ...
5
votes
2answers
206 views

Confirm: We can only notice planets if their orbit passes in front of their star and our view

If we can tell a planet exists by the dimming of the brightness of a star when it passes in front of our view of the star does that mean we cannot see a planet if it does not cross in front of our ...
2
votes
1answer
93 views

Finding a location using the direction of shadow, UT and date approximately

Does anyone know how to find a location by using : the direction of shadow relative to the normal (for example azimuth angle) the Universal time (UT) and date I have a satellite image and I know ...
0
votes
2answers
65 views

Was the radiant of the Perseid meteor shower ever near Vega thousands of years ago?

The ancient Chinese story of the Weaver Girl (Altair) and the Cowherd (Vega) tell of starcrossed lovers who are only allowed to meet once a year on the 7th day of the 7th (Chinese) lunar month, ...
0
votes
1answer
35 views

Books describing first-hand experience of astrophysicists finding planets without skipping actual maths

Are there good references of astronomical texts where we get a first-hand experience of astronomers uncovering astronomical gems using maths alone and not using observation. Observation may have been ...
3
votes
1answer
60 views

Solar / lunar positions in ECEF using SOFA C libraries

I'd like to calculate the positions of the sun and moon in the ECEF coordinate system using the SOFA (http://www.iausofa.org/current_C.html) libraries given a Julian day input. So far, I've got this ...
3
votes
1answer
45 views

Is there a name for the maximum in local solar elevation angle?

It came up in conversation today that we were nearly at 21st June, and the days would shortly be getting, um, shorter. We were trying to think of the the term that means "When the sun is at the ...
8
votes
2answers
119 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 ...
1
vote
1answer
41 views

How useful are filters for spotting nebulae?

Recently I've been trying to spot a couple of nebulae, IC59 and IC1318. The skies at the site are modestly dark (4.5 on the Bortle scale), I'm using an 8" scope, and I've slowly scanned around the ...
1
vote
1answer
396 views

How to calculate the temperature of a star

I need a way to calculate the effective temperature (surface temperature) of a star for a stellar model. I need something in the form Te=.... I have: Radius in m mass in kg the composition of ...
5
votes
1answer
84 views

What are the possible solutions to the Red Supergiant problem?

I have recently come across this so called "Red Supergiant problem" in the literature, a phrase that was coined by Stephen Smartt in 2009 in reference to why red supergiants with masses ∼16-30M⊙ have ...
3
votes
1answer
56 views

What exactly is this VLA radio image of Jupiter showing?

This VLA image is beautiful, and instructive, but I don't understand it fully. This version is from an article in Gizmodo where the credit reads: A radio image of Jupiter captured by the Very ...
3
votes
3answers
74 views

Question related to Sun rise and Sun set times

I am not sure whether this question is right or not so bear with me. I understand 'Sun rise' and 'Sun set' is caused by the Earth's rotation. I read that 'Sun light' takes around 8 minutes to reach ...
0
votes
1answer
108 views

Term for altitude of the sun?

The sun travels in an arc across the sky. Where I live, during the summer the arc rises higher, but in the winter the arc is lower. Once might speak of highest altitude or elevation the sun reaches ...
4
votes
2answers
35 views

Capability of observing transits with terrestrial telescopes of various sizes?

I have access to my university's telescope, Dearborn Observatory, an 18.5 inch refractor on the shore of Lake Michigan, just north of Chicago (yes, it's an atrocious location, but the telescope still ...
14
votes
3answers
2k views

Is the Earth-Sun distance 1.012 AU?

Wolfram Alpha's query: Sun Earth distance in AU gives: 1.012 au (astronomical units) They definitely use this value in other places too - e.g. Earth-Sun $L_1$ distances from Earth and from Sun ...
9
votes
1answer
2k views

Why can't our Sun be a binary with Jupiter as a T or Y dwarf?

I just learned about Brown Dwarfs, they are "failed" stars, they narrowly missed the stellar mass mark. I learned that Y Dwarfs have temperature as low as 80 Fahrenheit (The first one found by WISE ...
20
votes
1answer
1k views

Why is there a gap in this image of supernova discoveries?

I came across this gif showing supernova discoveries from the late 19th century to 2010. Here's the data in 2010: Notice that there's a prominent region shaped like an inverted U in which there are ...
1
vote
1answer
2k views

When will the next summer solstice and a full moon coincide? What day?

What day will the summer solstice and full moon coincide? As far as I know the next time will be in 2016. I would like to know what day.
0
votes
0answers
15 views

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? I would expect ...

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