# All Questions

66 views

### Mechanisms of binary/multiple star formation

What are mechanisms of binary/multiple star formation in different mass ranges (low, intermediate and high stellar masses)?
8 views

### What happens if an astronaut is hit by a tiny micrometeorite? [migrated]

A micrometeorite (including space debris in LEO) hitting the metal wall of the ISS would likely cause a shower of secondary high speed fragments. But there are other "softer" materials proposed which ...
82 views

### Does the holographic principle contradict eternal inflation?

As it is for example explained here, Andrei Linde's chaotic inflation is among the potential winners or survivors of the spring cleaning induced by the potential detection of primoridal gravitational ...
78 views

### How did Bradley arrive at the +/- correct speed of light when he calculated it?

After Bradley discovered stellar aberration and the corresponding constant of aberration he was able to calculate the speed of light, since he knew the speed of the Earth around the Sun. As far as I ...
43 views

### Space objects visible from earth

I recently saw the International Space Station without a telescope. Are there any other man-made space objects that can be seen using bare eyes?
94 views

### How can I calculate what star was above my head when I was born? [closed]

Almost everybody knows the concept of Zodiac. But there are others. And, AFAIK, even Zodiac classification is wrong for nowadays - since the classification of the people's Zodiac Sign was developed ...
74 views

### Why does time get slow near a black hole? [closed]

Why exactly does time get slow around a black hole? And does it provide a way to go into the future?
73 views

### A curious relationship between lunar periods and the solar year

Earlier today I was exploring the astronomy features on WolframAlpha, when I stumbled upon an intriguing numerical relationship involving the values for the lunar synodic and sidereal months. Using ...
139 views

### Is there a fundamental difference between a small galaxy, and a large star cluster?

For instance, If a large globular cluster were somehow ejected from its galaxy, and was observed by astronomers, would they call it a galaxy, or would there be characteristics of the star cluster that ...
55 views

### Do the E and B modes of the CMB polarization have anything to do with electric and magnetic fields?

As explained in this article, as the CMB is created from a vaiable (matter?) density $\kappa$ its gradient $\nabla \kappa = \vec{u}$ can be separated into a gradient and curl part, called the $E$ and ...
59 views

### Why isn't the dark energy getting decreased?

AS the articles on the web suggest, Dark energy is the reason behind the expansion of universe. If so, why isn't it getting used up in doing so. And consequently, the rate of expansion should reduce! ...
65 views

### How do scientists know if an Earth-like planet is really Earth-like?

I'm not sure how scientists determine that a planet is really an Earth-like planet. How do they do it?
105 views

### Galactic Habitable Zone

Do galaxies have habitable zones the same as stars do? Say in a galaxy with a very active nucleus producing a lot of heat and radiation, would there be a point at which no star's planets could harbor ...
47 views

### What must/do astronomers reveal beyond their academic papers?

Academic papers often make claims about observational data and results from computations. The papers only refer to names of data sources (such as an observatory) and of mathematical methods without ...
33 views

### How would an exoplanet be found from earth if our view of its star system is “from the top”?

When we find an exoplanet by observing the dimming of its parent star, this means that the planet passes in front of the star from our view. What if our view of a star system is from its "top" or ...
82 views

### What limits the usable focal length of telescopes currently?

What barriers - of technology, physics and possibly economy (things that would be possible technologically but are simply too expensive) sets the upper bound on quality of telescopes for observation ...
110 views

### What are these faint streaks on the moon?

I was poking around this Gigapan image of the moon's north polar region, when I noticed this area: What is the source of these light streaks? For position reference, here's a zoomed-out shot (I ...
70 views

### why are galaxies different in color?

whether its in movies,television,real-life or some planetarium different galaxies are shown in different color. For ex:- Milky way is always seen in Blue where as Andromeda gives out a bit reddish ...
69 views

### Are we moving away or towards each other?

There are numerous theories about the shape of the Universe. I've read somewhere most probably in 'A Brief History of Time' that there is a possibility that the Universe is spherical. So is it ...
46 views

### Is it possible to grow plants on Mars? [migrated]

If we provide adequate water supply will it be possible to grow plants/seeds/moss/algae (from Earth) on Mars? How different are Mars soil from Earth's soil?
124 views

### How can we predict a Big Crunch when all galaxies are moving further apart?

I've read that the further away a Galaxy is from us the faster it moves away. By this logic how can scientists predict that there will eventually be a big crunch when every piece of matter is ...
299 views

### Why airplane times differ between travels to east and to west? [migrated]

Why does it take longer to fly west to east than east to west? Which factors affects this? Does earth spinning affect the time difference? Maybe the air circulation? Can you please provide the ...
32 views

### Simple life on asteroids

If there were an asteroid orbiting its star within the habitable zone and this asteroid contained liquid water, would it be possible for simple life such as bacteria to form?
76 views

### Is there another explanation, apart from the doppler effect, for the redshift observed in distant galaxies?

On episode 10 of the original Cosmos TV series, Carl Sagan mentions that some scientist don't agree that the redshift observed in distant galaxies is evidence of the big bang, stating that probably ...
108 views

### What is the probability that there is life on other planets?

I would like to know, from a mathematical point of view what is the probability that 1) There is organic life on other planets 2) There are advanced species like us or even greater than us on other ...
109 views

### What is Gravitational Lensing?

What is the effect known as gravitational lensing? How does it work? What objects would be able to cause this effect?
57 views

### What mechanism causes oscillations of the solar system's orbit about the galactic plane?

In a recent paper (news release here) Lisa Randall and Matthew Reece propose that a dark matter disk coinciding with the galactic plane together with the solar system's oscillations through the ...
80 views

### What is the temperature of outerspace?

I want to know whether the temperature in Outer space is higher than earth's or cold.Is the temperature in outer space vary as it does on earth?
56 views

### Would it be possible to calculate the expected frequency of impact craters of all sizes on Earth

Can the expected frequency of all sizes of impact craters on Earth be calculated based on the preservation of impact craters seen on the Moon? Taking into account the difference in gravity and ...
100 views

### I'd like to become an astronomer. What experience do I need? [closed]

I think I'd like to become an astronomer. What degrees and training/experience do I need to become one? I've heard I should take science and mathematics, but I don't know which specific courses I ...
42 views

### What is the relationship between the focal length and f number of a telescope compared to a guide scope?

How do you determine the optimal length of a guide scope for a given imaging telescope? I imagine it would have to take into consideration the pixel size of the guide scope, but would the aperture ...
30 views

### Is there online data on asteroid axial tilts?

I am hoping to find axial tilts for asteroids and also their spring and fall equinox. Some of the asteroids I'm interested in are: 4 Vesta, 1 Ceres, 24 Themis, 65 Cybele, 153 Hilda, 624 Hektor
32 views

### Why can primordial tensor perturbations of the CMB be ascribed to gravitational waves?

Why can primordial tensor perturbations of the CMB be ascribed to gravitational waves? Is this attribution unique, or are there other michanisms that could lead to the ecitation of tensor modes? In ...
34 views

### If I have amateur astrophotography image data that might be of scientific value, what should I do?

I have some image data that may be interesting to someone, somewhere, but I don't know who to contact or notify. I would imagine it would depend on the type of data, but maybe there is a central ...
87 views

### What causes Earth's gravity? [closed]

Why Earth is like a magnet? how can earth attract any object irrespective of what it is made of? What is the reason behind Celestial Body's gravity? i.e Sun,Jupiter,Moon etc.
31 views

### What exactly does outer space contain?

Does outer space contain any gases? Recently i watched a video on youtube,in which NASA installs a camera on a spacecraft.The footage shows some dust particles or some matter floating over the space ...
46 views

### regarding spectral type of a star

consider two stars of the spectral type and subtype, but not necessarily both on the main sequence. Describe whether this information is sufficient to tell you how the stars differ in surface ...
100 views

### Why are most planetary orbits nearly circular

In our solar system, with the exception of Pluto all planets follow a relatively circular orbit around the Sun, at the same inclination. They also all rotate in the same direction, none are ...
17 views

### What are the differences between TESS and PLATO exoplanet telescopes?

Within a year now it has been decided to launch TESS in 2017 and PLATO in 2024, space telecopes of NASA and ESA. They seem to have very similar science goals, both searching for transiting Earth sized ...
19 views

### need data-point: actual counts per second with APD (avalanche photodiode) detector

I'm designing a sensor system to perform specialized [astronomy and space-sciences] experiments, and need a "reality check" to support or adjust my theoretical calculations. What I need is the ...
20 views

### local stellar mapping data

I've been playing around with Near Star Map, and I think I kind of want something more sophisticated, so for all stars within 100ly/30pc, is the following known? velocity (it would be nice to have a ...
21 views

### Max. speed that a space probe can communite with the Earth? [closed]

Question: Which is the average or maximum speed of a telematically sent message that a space probe can send? Is as simple as radio waves travel at the speed of light in a vacuum? Context: I have been ...
54 views

### How will the recent appearance of a supernova, the closest in 27 years, help reduce the uncertainties in our measurements of dark energy?

A supernova has been recently spotted on M82, also known as the cigar galaxy. Being the closest to earth in 27 years and given the advances of technology this article proposes that: ...as the ...
26 views

### Black dwarf binary systems

I know black dwarf stars do not exist yet, and that they are what white dwarfs end up after a long time. The question is really simple: would it be possible to have a binary system in which one of the ...
42 views

### Why do stars become red giants?

Disclaimer: I’m not a career astronomer. I don’t own a telescope. I have no professional credentials. But I do find this stuff fascinating, and I consume all astronomy documentaries I can. So, ...
57 views

### Rotation and relativity

When a planet is spinning around its own axis, it has an effect on the trajectory of its satellites. I believe it is called frame dragging. Spin increases the kinetic energy of an object, ...
75 views

### Do solstices and equinoxes shift over time?

Right now, I think the winter solstice is around December 21. Has it always been around this date constantly? Since the earth's axis's 23.45° tilt will be on the exact opposite side in 13000 years ...
185 views

### Is the universe expanding faster than speed of light?

The celestial bodies like stars and galaxies are moving away from each other. How fast are they moving apart? Is that speed more than the speed of light?