3
votes
0answers
25 views

Protocol for establishing longitudinal meridians on other heavenly bodies

When we first observe a new heavenly body (it could be a new star, asteroid, etc.,or a minor planet in our own solar system), are there any procedures set in place for establishing a system of ...
1
vote
1answer
28 views

What is the name of the cycle whereby the lunar azimuth and altitude recur on a given day?

Like the Metonic cycle, except for position in the sky, not phase. Original question: If I look up at the moon tonight, how long before it is in the same apparent position, and same phase, again? I ...
1
vote
0answers
32 views

a math problem in Spherical astronomy [on hold]

this is an exercise from Spherical astronomy by Smart, which i want to solve: $\frac{d \eta}{d H}= -\cos(\phi) \cos (A) (\sin (z))^{-1}$ when $\phi$ is latitude, $\eta$ is parallax, $H$ is sidereal ...
5
votes
2answers
14k views

How much magnification is needed to see planets of solar system?

I have a 3inch Newtonian reflector telescope with 300 mm focal length. I can use highest magnification of 75x using a 4mm eyepiece. But in 75x I can't see details of Jupiter what was expected. Instead ...
9
votes
6answers
1k views

Why don't we have 2 Summers and 2 Winters?

Due to Earth's elliptical orbit, its distance from Sun varies by almost 5 million Kilometers (147 million Kilometers at closest point & 152 million Kilometers at farthest point, i.e. almost 3% of ...
0
votes
1answer
114 views

Cluster of fast moving stars

We live in NW Tasmania in a country town and tonight out walking I pointed out a long cluster of stars to my sister as they made an unusual shape but then we realised they were moving really fast - we ...
1
vote
2answers
66 views

A quick (elementary) check on arsecond conversion to sky distance in parsecs

I just wanted to double check I had something correct. If an object, say a nebula, is measured to roughly have a diameter or extent of, say, 250 arcseconds, would its diameter in parsec simply ...
8
votes
2answers
3k views

Is it possible to move a planet out of its orbit? At least a lighter planet?

As observed by many researches our sun will be exhausted in the distant future. So does anyone think that driving our planet (or any planet) closer to the sun for more light and heat is a solution for ...
0
votes
2answers
41 views

Warm and Hot dark matter density profiles

For cold dark matter, density profiles are well known and easy to find information about - eg. NFW, Burkert, Einasto, and others. But for some reason I couldn't find explicit expressions for the ...
1
vote
1answer
50 views

Could the Sun's magnetosphere block extraterrestrial contact?

I was reading how certain strong magnetic fields can block or alter radio waves so bearing this in mind would it be possible for the Sun's magnetosphere to block attempts to establish radio contact ...
0
votes
0answers
30 views

What (actually) is a radio “homology telescope” and will the 500m dish in China be one?

This question is about design aspects of large radio telescope dishes which allow them to flex under the influence of gravity as they change elevation angle, and still maintain good optical ...
6
votes
2answers
740 views

How can the Sun burn without oxygen?

Allright I am a 17 year old student, that only just figured out that the universe is amazing! Thanks to Dr. Neil Degrasse Tyson I raised a lot of interest in the universe. Due to his latest show "...
2
votes
2answers
94 views

Could this three moons system be stable?

In my fictional world I have selected all parameters to maximize the Hills Sphere of my planet. The planet has three times Earth's mass and it is located in 2 AU from its star that's 1.4 times more ...
1
vote
0answers
22 views

What are the requirements to become a planet? [duplicate]

A planet is taught to us (at primary school) as a ball of rock that orbits around the Sun and is similar to our own planet, Earth (in as a ball of rock). But of course, humans have to be more specific ...
35
votes
3answers
9k views

How many planets are there in this solar system?

So, in school (that's a long time age) they have been teaching us there are 9 planets in our solar system. Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto But every now and then I ...
2
votes
2answers
136 views

Advancement of perihelion, data

I was looking for accurate and up-to-date data regarding the advancement of the perihelion of the planets in the Solar System, the only ones I've found so far are at least 90 years old bout I really ...
0
votes
0answers
12 views

Virial coefficient when computing dynamical mass enclosed by a rotating galactic disk of gas

Suppose I have a large thin disk of rotating gas in a galaxy -- the disk has a maximum inclination-corrected $V_{max}$ and a maximum radial extent of $R_{max}$ corresponding to that $V_{max}$ ...
19
votes
2answers
3k views

Why is our solar system “tipped” about 63° with respect to the plane of our galaxy?

Our own solar system is "tipped" by about 63 degrees with respect to the plane of the galaxy. Has it ever been researched or is there any scientific theory which could explain the reason why our solar ...
1
vote
2answers
110 views

What would Earth be like without the Moon?

If somehow our moon was destroyed (for example by an asteroid) what would happen to Earth? Would the Earth be affected by the absence of the moon? Would humans be able to live normal lives without ...
1
vote
0answers
21 views

Is there always visible airglow from space? [migrated]

Looking at time lapses taken from the International Space Station, I discovered that earth atmosphere can glow at night, even when it seems that those pictures were taken far away from auroras. ...
1
vote
1answer
38 views

How can I convolve a template spectrum with a photometric filter response spectrum?

Suppose I have a template stellar population spectrum (say, from Bruzual & Charlot 2003) which runs from like 1000 Angstroms to 160,000 Angstroms and which has x-axis wavelength units of Angstroms ...
3
votes
1answer
80 views

Universal point for sky observation

Is there a place on Earth, where polar axis lies on the horizont and heaven equator is in zenit? If it exists, can I, in theory, see all the constelations available worldwide this night?
8
votes
2answers
162 views

Is it possible for a moon to continuously have a side facing its star whilst orbiting a planet?

For example; is there any possibility for the moon to always have a side facing the Sun whilst orbiting Earth? And if so then what would the day cycle be like?
7
votes
2answers
67 views

How was Earth's “quasi-satellite” 2016 HO3 “first spotted” and it's orbit determined?

Under a question I asked a few days ago Have there been any documented mini-moons since 2006 RH120? @Hobbes mentioned the recent news about 2016 HO3 - a near-Earth asteroid that stays near Earth ...
0
votes
0answers
79 views

What is Half-life of knowledge in Astronomy? [closed]

This question is inspired by this answer. About 16 years ago, we knew different numbers of stars in Polaris system than we do now. Even though we have come a long ...
3
votes
1answer
9k views

In 2016, the summer solstice will coincide with a full moon. How often does this happen?

I found that the solstices work on a 400 year cycle based on this. I can't find anything similar for the lunar cycle. Is there a formula I can use to calculate the date of the full moon?
4
votes
2answers
245 views

Are planets moving away from the sun?

I saw on the tv show Through the Wormhole (hosted by Morgan Freeman) that the planets in our solar system have been continuously moving away from the sun for millions of years. however, when I try to ...
1
vote
1answer
41 views

Astronomy Calculations Tool

I took 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 ...
6
votes
2answers
126 views

How many actual stars are Polaris?

I am getting conflicting accounts everywhere. I heard astronomers saying Polaris is a 3-star system. Some say they are binary but are optical-doubled with a 3rd. ...
3
votes
2answers
86 views

Is time taken into account by astronomers when creating and using maps of the universe?

There's really two questions I'm asking. Firstly, when maps are produced of stars and galaxies, are they just produced as we see them now from our viewpoint? Or are they based on the motion of those ...
11
votes
2answers
142 views

Conventional matter to dark matter ratio, outside of galaxies (Bounty!)

I'm pleased to offer a bounty to attract more attention to the fantastic Astronomy site. Consider say this outstanding diagram from another question, To begin with galaxies have a typical ...
0
votes
0answers
13 views

Where can I find the DR12 SDSS dataset in their website

I have to cross-match the SDSS DR12 dataset with that of GALEX but apparently I cannot find the fits document which has the same field as that in GALEX. I have explored the website but I couldn't find ...
2
votes
2answers
54 views

Any cheap (<100 euro) tools for observing the lines in solar spectrum?

I am now reading the book ''The story of Helium and the Birth of Astrophysics''. I really want to observe the lines (dark or bright) in the solar spectrum. Any easily available tools for an amateur?
3
votes
2answers
79 views

How to find which part of the sky a photo contains?

I was taking some photo stacks yesterday, and I also took a plenty of random ones (pointed not at a specific object) too at 200mm. However, I've ended with a shot but I have no idea where I pointed ...
1
vote
2answers
135 views

why was the probability of one in 10 billion per planet considered highly pessimistic by a recent study on aliens? [closed]

A recent article about the existence of extraterrestrial life claimed that "unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then ...
-1
votes
0answers
45 views

Are a white hole's forces completely opposite of a black hole? [duplicate]

Would not all the forces of a black hole be opposite if the light is escaping from it? For example, rather than it attracting everything to it, would it repel everything?
3
votes
1answer
131 views

What starting circumstances have to be for “grand tack” hypothesis to work, and why they are lacking in other planet systems(as far as we know)?

I recently read a bit about "grand tack" hypothesis. It was extremely interesting and it seems to reasonably well explain many features of our solar system. At the same time it supposedly is ...
29
votes
1answer
1k views

Why has Venus's atmosphere not been stripped away by solar wind?

This answer on Space Exploration to a question about Mars says that one reason Mars has such a thin atmosphere is because it lacks a magnetic field to protect it from the effect of double solar winds. ...
0
votes
0answers
31 views

Question on retrograde motion [duplicate]

I am a beginner Does planets exhibit retrograde motion (eg Mercury and Venus) only because of earth rotation? Or is there any other reason? Please clarify
0
votes
2answers
107 views

If the planets only attract, then how can they stay in their orbit?

Gravity is related to mass, and gravity is an attracting force on every body. Then what happens when bodies only attract each other..without repulsion they may strike the sun. I think there must be a ...
1
vote
2answers
94 views

What is the effect of the axial precession on the orientation of the planet's orbits?

I am working on an online application to visualize the positions of the planets and to calculate their ephemerides (you find it here, but it is not complete yet). I do not have much knowledge in ...
3
votes
1answer
119 views

Could the word “multiple stars” include binary stars?

We are translating some illustrated book for kids about astronomy, and then have a question as in the title. Referring to Wikipedia etc., It appears that "binary stars" represents the star systems of ...
0
votes
2answers
46 views

Survival on a rogue planet [closed]

Are there any planets not orbiting a celestial body which can support life despite the temperature? Also what is the absolute minimum temperature that life can survive in?
0
votes
1answer
25 views

How do I apply a velocity shift to a wavelength array with uniform logarithmic spacing?

Suppose I have a wavelength array for a spectrum in units of Angstroms. Suppose further that the wavelength has "uniform logarithmic spacing" such that if I just take the difference in Angstroms ...
6
votes
2answers
123 views

Does the shape of a supernova remnant depend on the progenitor star's magnetic field?

The magnetic field activity in a star can be very chaotic and my question is are they somehow related?
0
votes
0answers
24 views

Negative Spectral Flux Density

I am working on a project and using some satellite images. In some of the images the Spectral Flux Density is negative. What does it indicate?
1
vote
2answers
55 views

Can a rogue planet neither orbit around a star nor a galaxy?

As we know, rogue planets don't orbit around a star, how about galaxy? Can a rouge planet not orbit around a galaxy?

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