7
votes
3answers
93 views

What is the long term fate of the gas giants?

If I'm not mistaken, it is believed that the reason for such turbulent weather on the 4 outer gas giant planets is that the internal pressure is so great that it is generating heat, which is causing ...
1
vote
2answers
115 views

What are the nearest galaxies I can observe?

What are the nearest galaxies I can observe using my Telescope? Does it require to be out of the city lights?
2
votes
2answers
62 views

Free neutrons and stellar nucleosynthesis

Both the R-process and the S-process of stellar nucleosynthesis rely on absorbing 1 (S) or more (R) neutrons. Where do they come from? I thought there are no free neutrons in stars. (Also the ...
4
votes
1answer
60 views

Have we detected galaxies which have red-shifted beyond the visible light range?

According to this answer it is possible for galaxies' light to move beyond the visible frequencies due to redshift: ...
4
votes
4answers
129 views

Without using absolute magnitudes or isochrones, how might we tell a star's age and evolutionary status?

Usual methods of estimating stellar ages involve isochrone approximations. It can also help to estimate a star's radius by correlating its absolute magnitude with effective temperature and apparent ...
6
votes
1answer
75 views

What is the reason for high lithium concentrations in Sun-like stars?

In reading the European Space Organisation paper Lithium depletion in solar-like stars: no planet connection (Baumann et al. 2010), several conclusions based on their observations include: Lithium ...
3
votes
2answers
625 views

Why can I see the whole moon during various non-full-moon phases?

Here's an image that describes the phenomenon I'm asking about. The very thin sliver to the left is of course the surface of the moon as lighted by the sun. But the rest of the moon is also faintly ...
2
votes
1answer
35 views

Red shifting galaxies

I am an amateur astronomer please correct if any of my understandings are wrong. We all know that from the Hubble's ultra deep field image the most distant galaxies which were created shortly after ...
2
votes
2answers
32 views

How do I find the RA of sunset and sunrise in a specific location?

I want to make some observations with a telescope in Hawaii on Mauna Kea but I am living somewhere else (not Hawaii) and I want to plan a night's viewing on the Hawaiian telescope. How do I find the ...
-2
votes
0answers
19 views

Red shifting galaxies [duplicate]

I am an amateur astronomer please correct if any of my understandings are wrong. We all know that from the Hubble's ultra deep field image the most distant galaxies which were created shortly after ...
15
votes
1answer
844 views

Can you see man-made lights on the dark side of the Earth from the surface of the moon with the naked eye?

This question is prompted from a comment on this answer: Could a person on the surface of the moon see man-made lights on the dark side of the Earth with the naked eye? If not, how much magnification ...
4
votes
1answer
102 views

Maximum Amplitude of a Lissajous Orbiting Object in a L4 or L5 Position

I stumbled on The Lagrangian points during some wikipedia reading. After looking at the gravity contours, I naturally come to the conclusion that the L4 & L5 should have a wave pattern and then ...
2
votes
1answer
67 views

Astronomy Olympiad Books

I'd like to one day take the Astronomy Olympiad, however I'm at a loss to know where to begin. As it currently stands I have no experience whatsoever with Astronomy. If there are people here with some ...
0
votes
0answers
8 views

Where can I find historic rates of meteor impact events?

I have a friend that watches a lot of TV news and they have the impression that impact events are becoming more common than in recent memory. Does the evidence support or refute this? Thinking it ...
3
votes
2answers
134 views

time on earth compared to completely stationary in space

I recently started trying to understand the theory of relativity and I have the following question. Because earth is orbiting the sun at approx 67,000 mph (and its my understanding time slows down ...
1
vote
1answer
16 views

In the chromoscope, what is the X-ray source between Ophiuchus, Libra and Scorpius?

http://www.chromoscope.net/ is a nice toy. Pressing 'L' shows the constellations as guide. There's a bright X-ray source between Ophiuchus, Libra and Scorpius. In Hydrogen-Alpha there are two ...
0
votes
3answers
44 views

Why isn't the moon dark in a solar eclipse?

In the following partial solar eclipse, the moon is "invisible" rather than being dark. By contrast, if someone stands between my view and the sun, they will appear as a dark figure instead of ...
0
votes
1answer
60 views

What is “Median Stellar Mass”?

Could someone explain what is "median stellar mass" and how is it calculated? I have seen it written as: $$\log(M)$$ or as: $$\log\left(\frac{M_*}{M_{\text{Sun}}}\right) $$ but I do not ...
6
votes
1answer
84 views

What are the last images from the Galileo orbiter before impacting Jupiter?

NASA's Galileo orbiter at Jupiter ended its mission in 2003 by intentionally dive into the gas planet. Did it take and transmit any close up images before it ceased to function? If not, why? Are there ...
1
vote
1answer
52 views

Where can I learn these Astrophysical techniques? [Read below]

Whenever I read any Astro papers in http://arxiv.org/ they usually talk about Data fitting or modelling or sentences like 'we fitted the spectral region by analytic functions i.e. by multi-component ...
2
votes
0answers
28 views

What is the cause of the variation from high and low mean obliquity periods of Mars?

It is reasonably well known that Mars has a greater obliquity range than Earth, due to Mars lacking a stabilising influence of a large moon. However, the Martian obliquity seems to have gone through ...
2
votes
0answers
23 views

What will New Horizons be able to say about a magnetic field at Pluto?

Does NASA's New Horizons flyby probe to Pluto have instruments to measure Pluto's (or Charon's) magnetic field, if any? I'm a bit confused by the Wikipedia article which says that New Horizons, ...
4
votes
1answer
26 views

How tall are the “fractured” linear structures on Europa's surface?

What are the altitude differences in the high resolution part of this image of Europa? How high do those ridges rise over their neighboring valleys? And how large is the area shown in this image? ...
5
votes
3answers
77 views

How do you calculate the effects of precession on elliptical orbits?

Kepler's first law states that planets (and all celestial bodies orbiting another body) travel in elliptical orbits, which have well-known formulas that make it relatively easy to calculate the ...
7
votes
2answers
244 views

Where does the Milky Way end?

I was reading this article and it says the following: Researchers measured the mass of the Milky Way and found that our galaxy is approximately half the weight of a neighbouring galaxy known as ...
1
vote
2answers
63 views

Is the location that published calendars use to calculate the seasons one specific location on the earth?

All the calendars in my house say the fall equinox is Tuesday the 23rd. All the astronomical programs and astronomical sources say it is it is Monday the 22nd in Ohio. Since the time given is 10:29 ...
11
votes
1answer
1k views

Is the moon moving further away from Earth and closer to the Sun? Why?

According to The NASA Moon Facts page: The moon is actually moving away from earth at a rate of 1.5 inches per year. Why is the moon moving further away from the Earth? Is this a result of the ...
3
votes
4answers
175 views

Hulse Taylor Binary Pulsar - How is “Cumulative Periastron Time shift” calculated?

Following on from a previous question about the interesting Hulse Taylor Binary Pulsar. BACKGROUD Weisberg & Taylor, 2004 present a graph showing the change in "Cumulative Periastron Time Shift" ...
1
vote
1answer
34 views

speed of light measurement

While searching for different methods of speed of light measurement, i came across one of the method of fizeau discussed below which i cannot fully understand. In short,in Fizeau’s apparatus, a beam ...
1
vote
2answers
117 views

Why does the face of the moon 'sync' with the earth? [duplicate]

We never see the dark side of the moon. It rotates so that the same side always faces us. I heard two (dinner party) theories on this: 1. The moon was made by smashing out a chunk of the earth, and ...
3
votes
1answer
318 views

How likely and severe is the threat of a gamma ray burst to earth?

In the National Geographic article: http://news.nationalgeographic.com/news/2009/04/090403-gamma-ray-extinction_2.html it is suggested that a gamma ray burst likely caused a mass extinction in earth's ...
6
votes
3answers
173 views

Planets and Pluto? Neptune?

If one of the rules to be a planet is that it needs to clear ALL objects from their orbit, does this also make Neptune a non-planet? Since it has thus far failed to clear Pluto (and based on an answer ...
1
vote
1answer
30 views

How is the maximum density in a circumstellar disk determined?

I'm working with some equations to model the evolution of a circumstellar disk. One of the equations is $$\rho(r)=Ce^{-\frac{(r-r_{peak})^2}{2 \sigma ^2}}$$ where $\rho$ is density, $r$ is the ...
2
votes
1answer
44 views

Effect of the absence of atmospheric refraction to sun rise and sunset times

What is the effect of absence of atmospheric refraction on sin rise and sunset time? Is it will be delayed or earlier for sunrise and sunset, and why? Thank you:)
2
votes
1answer
60 views

How does this strategy for chasing the sunset work?

In Randall Munroe's What If? blog he tackles this question: What is the longest possible sunset you can experience while driving, assuming we are obeying the speed limit and driving on paved ...
2
votes
0answers
25 views

What range of exit pupils work for observing the full moon?

I'm observing the full moon, from a major city, with heavy light pollution and dust. The objective size is fixed, for this comparison, something between 4 and 6 inches. The question is about the ...
1
vote
2answers
102 views

What is a low mass Black Hole?

Is a Low Mass Black Hole also called a Stellar Mass Black Hole? Can Low Mass BH be also called Primordial BH? (If low mass BH are Stellar Mass BH-What is their size in terms of the mass of the sun?)
7
votes
1answer
131 views

Detecting Deep Impact

There have been several accounts in media articles of asteroid near misses, many describe that the asteroid was not seen before the near miss. After reading the question and answer to How can we tell ...
3
votes
1answer
81 views

What is the explanation for rapid inflation just after the big bang?

I often hear about cosmic inflation occurring rapidly after the Big Bang, but have never came across any explanation for it. What supposedly caused this inflationary period in the early universe? ...
5
votes
2answers
77 views

How does 67P rotate?

What can be said about 67P/Churyumov-Gerasimenko axial tilt? Is it fixed (if so, at what value), only changing with precession (at what rate?) or does 67P "tumble" with axial tilt changing over time? ...
1
vote
2answers
56 views

can we see all binary stars as pairs?

As it is obvious from the question title is there any restriction or cases that we can see the binary stars as not in pairs also is there any binary stars doesn't linked together by gravity ? I ...
4
votes
5answers
354 views

Very bright star in the east at northern hemisphere. What is it?

From some time now (few weeks as far as I can remember), there is a very bright star in the eastern sky. I first thought it was Venus, but according to this link, Venus is in the western sky and ...
1
vote
1answer
36 views

Roche Limit for Earth-like body around Earth-like body

In a discussion elsewhere about binary planets, it came the question. How near can a planet like Earth (maybe Earth itself) be to another planet like Earth before both of them tearing apart due to ...
2
votes
1answer
109 views

moonless night and lunar phase

How to define moonless night? There is no moon at all during some night? How to calculate and know whether the moon would appear during one night? If the lunar phase is full moon, is it possible ...
-1
votes
1answer
97 views

How can there be anything “beyond” the CMB?

Two things we take, for this purpose, to be axiomatic: The CMB is the oldest thing we can observe directly The cosmological red shift tells us how "old" something we are observing is Yet we also ...
-1
votes
1answer
45 views

Determining Distances in Space [closed]

I suspect the scope of this question may be to broad, but: what are some methods for determining distances between two objects in Space? Please present the methods in historical order, so as to make ...
-2
votes
1answer
57 views

Why does Earth enjoy a significantly longer time as a habitable planet as compared to Mars or Venus? [closed]

On a related note, why didn't Venus remain habitable for longer than it did? Is the current hypothesis as to the time when Venus's atmosphere became hostile and what event triggered it, proven true?
8
votes
1answer
108 views

Appearance (frequency) ranking of stars?

Is there some ranking / statistics that shows how common given type of celestial objects is? A table that would allow the answers to questions like: What type of star is most common per volume of our ...
1
vote
2answers
52 views

Why does a particle feel no force at radii greater than itself?

I am working through Liddle's "An Introduction to Modern Cosmology", and in a newtonian derivation of the Friedman equation he states: in a spherically symmetric distribution of matter, a particle ...
0
votes
1answer
35 views

Declination and Ascension - the Sun and Andromeda

If Andromeda is overhead at midnight, what is the right ascension of the sun? (andromeda is ar RA =1hr, Dec = +40). I thought I understood what Dec and RA were, but I can't think of how to start this ...

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