-1
votes
1answer
156 views

Distance between Earth and where The Big Bang's happened? [duplicate]

The universe is around 13.8 billion years old. We know how fast the light is. We also know how fast our galaxy moving around inside observable universe. Is it possible to calculating distance ...
4
votes
3answers
144 views

How should one rationally deal with the issue of space travelling alien civilizations?

What kind of reasoning is appropriate to understand the as of today unanswered question of whether there are (other) interstellar space travelling civilizations in the Milky Way? We have already sent ...
4
votes
3answers
193 views

how far away could we detect that earth has life?

My guess is that life bearing planets are too far apart to be detected. I think we can only find the ones within a sphere around our planet that is 100s of light years in diameter but I suspect life ...
4
votes
2answers
128 views

Could the Philae comet lander be recharged by laser?

Could the Philae comet lander be recharged with a laser (or possibly many lasers) from earth? My thought would be to aim one or more powerful lasers from earth at the Philae lander to recharge it ...
3
votes
2answers
73 views

Are our 'observations' of or near a black hole affected by gravity induced time dilation?

This answer made me wonder if matter/energy/events near a black hole are viewed (by us) in a very different time frame, how might that affect our measurements? ...
0
votes
1answer
31 views

Could discoid galaxies be expanding?

I understand that astronomers once thought that the material in the disc of a galaxy was moving around the galactic centre (where most of the mass was thought to be) in roughly circular orbits. The ...
2
votes
1answer
45 views

How many stars can be seen naked eye from outside the atmosphere? Ho dense is the “sky” from there?

When I was 20, I went to Naxos (Greece) with friends. I was driving my car during the night on the mount Zeus (1003 meters - 3,291 ft) listening Pink Floyd. Up there we stopped the car to take a ...
3
votes
1answer
81 views

What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...
4
votes
1answer
129 views

How bright is the full Earth during the lunar midnight?

At lunar midnight (i.e. the new moon as seen from Earth), the Earth is in its full phase with its entire disk in sunlight, and it is the brightest object in the lunar sky. How bright is it, and how ...
2
votes
4answers
71 views

Can objects enter hydrostatic equillibrium through processes other than the influence of gravity?

Wouldn't a droplet of liquid (say water) floating around in space become spherical and "in hydrostatic equilibrium" due to surface tension but not gravity?
5
votes
1answer
86 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: ...
5
votes
2answers
748 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 ...
3
votes
1answer
57 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 ...
9
votes
1answer
186 views

How long do planetary rings last?

I'm surprised that this question hasn't been asked before (here or on Physics), to the best of my knowledge. It's one that I might have asked when I was a bit younger, and one that I think other ...
1
vote
2answers
178 views

Why does the distance between Sun and Earth stay the same?

Well, we all know Sun gravity , makes the Space time curvature and space pushes the earth towards the Sun. But my question is "why the distance between the Sun and Earth is Same? Earth should have ...
1
vote
0answers
16 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 ...
15
votes
1answer
970 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 ...
1
vote
1answer
21 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 ...
34
votes
4answers
4k views

How does the Earth move in the sky as seen from the Moon?

I just want to be sure I am visualizing this correctly, because it seems odd. The Moon is tidally locked to the Earth but there are wobbles to its motion due to libration. So from a point on the ...
1
vote
3answers
96 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 ...
4
votes
2answers
109 views

Likelihood of a stable system with a dwarf planet's orbit inside that of a gas giant

I keep thinking of various planetary system configurations, and would like to know: What are the fundamental references based on Monte Carlo long-term simulation of planetary systems' evolution that ...
1
vote
2answers
138 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?
1
vote
1answer
90 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 ...
5
votes
2answers
149 views

Why is carbon so rare on the Moon and on Mars?

Carbon is the fourth most common element in the universe and in the Solar system. It is about the ninth most common element in Earth's crust. It doesn't seem to be part of any of the ten most common ...
2
votes
2answers
160 views

Can the theory of multiuniverse explain dark matter?

If there are many universes they must have an gravity effect on each other. Since dark matter is measured through gravity but we dont know the mass behind it, isnt it possible that it comes from ...
2
votes
0answers
33 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
1answer
62 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 ...
4
votes
1answer
64 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, ...
6
votes
1answer
104 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 ...
4
votes
1answer
30 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? ...
2
votes
1answer
44 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 ...
2
votes
1answer
80 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 ...
1
vote
2answers
151 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
2answers
84 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
1answer
39 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 ...
1
vote
2answers
143 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?)
2
votes
1answer
97 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:)
1
vote
2answers
98 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 ...
1
vote
1answer
50 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
668 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
vote
0answers
48 views

stellar evolution fortran code-runge kutta mass step from center to fitting point [closed]

I am trying to integrate the four stellar model equations from the core to a fitting point and from the surface to the fitting point ($x_f$). When I start the outward integration, however, I have to ...
-1
votes
1answer
57 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
120 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 ...
1
vote
2answers
59 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
37 views

Yellow object between δ Ori and η Ori

Can someone perhaps assist me in identifying the yellow object between δ Ori and η Ori? I took an image of this object, but I can't identify it. It can be seen on the image below, hosted on the Eagle ...
-3
votes
1answer
82 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?
5
votes
3answers
127 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 ...
2
votes
1answer
63 views

Is axial tilt direction correlated with semi-major axis direction?

Earth comes closest to the Sun every year around January 3. Winter solstice is at 21-22 December, merely some 12-13 days away. That means projection of Earth rotation axis onto the plane of its ...
-2
votes
1answer
56 views

As of now did a radio telescope ever recorded something else than the silence of space? [closed]

When a radio telescope listen to the Universe; a constant sound is recorded. Is it the noise "of the mic" : interferences? Scientists says that when they will notice variations on this basic constant ...
2
votes
2answers
101 views

How do I calculate the positions of objects in orbit?

In a model of the solar system, given the Sun is at the point $(0, 0, 0)$, an given the six orbital elements for each object in orbit ($a$, $\epsilon$, $i$, $\Omega$, $\omega$, $M_0$), how can I ...

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