12
votes
2answers
216 views

Is there a upper limit to the number of planets orbiting a star?

Our sun has 8 planets orbiting as well as a number of dwarf planets. Are there any calculations that hint as to whether this number is close to some theoretical maximum value or are we simply an ...
12
votes
1answer
253 views

Could any known, living organisms on Earth survive on Mars?

No life has been discovered outside of Earth (yet?), but do we know if anything that would be considered "living" on Earth could conquer Mars? (or maybe Venus?) With the Mars One project on the way, ...
12
votes
3answers
293 views

Does a planet's mass or gravity affect the height of it's mountains?

According to this Wikipedia page, the top five highest mountains on Mars (and the highest on Venus) are all taller than Mount Everest (and Mauna Kea as measured from the ocean floor). Does a planet's ...
12
votes
1answer
112 views

Affordable night sky photography

As an amateur with limited budget, I'd be interested in taking photos of the night sky, trying to capture more detail than human eye armed with a lens of comparable parameters to what I have in my ...
12
votes
1answer
77 views

How are the compositional components of exoplanet atmospheres differentiated?

How are exoplanetary atmosphere compositional spectra distinguished from those of the parent star(s), from the composition of the planetary surface or any other factor? Is it actually possible to ...
12
votes
1answer
186 views

How exactly does inflation convert random gravity fluctuations into coherent gravitational waves?

In the course of this very enjoyable press announcement, it is mentioned that inflation can create gravity waves by amplifying gravity fluctuations. I do not properly understand this statement. I ...
11
votes
3answers
2k views

Does the Sun belong to a constellation?

Each new star we find is generally considered to be part of the constellation it is nearest to. Our Sun is obviously a star, just much closer. Is our Sun part of any constellation? If so, which ...
11
votes
2answers
281 views

At what distance from Earth would our Sun be the same apparent magnitude as the next brightest star in the sky?

When I stand outside looking at the night sky, to my untrained eye, everything except the moon looks like a star. I know intellectually that some are planets circling our sun, and some are entire ...
11
votes
2answers
235 views

Space expansion in layman terms

So far I got to understand the expansion of space is not to be understood as stars drifting further apart through space. There's something more fundamental - e.g. you can't simply measure speed of it, ...
11
votes
3answers
175 views

Is it possible to measure galactic red shift using consumer telescope equipment?

I was wondering if it would be possible to measure red shift from distant galaxies using consumer grade telescope equipment and spectroscopy filters. (like this one) I imagine it would require a ...
11
votes
1answer
183 views

How are the photos of milkyway taken?

We are inside the milky way, right? So, how are we able to take photos of the milky way galaxy?
11
votes
1answer
280 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. ...
11
votes
1answer
118 views

Has Hawking Radiation Ever Been Observed?

I know Hawking Radiation has firm theoretical footing, but has a signal ever actually been observed? What observational research is being done to attempt to see this effect? Is it simply too tall an ...
11
votes
1answer
117 views

Have we ever observed a large meteor hit the Moon?

Since the moon has no atmosphere, its surface has many more meteorite impacts than Earth's does. Image source Have we ever observed a meteor strike the surface of the Moon?
11
votes
2answers
139 views

Will an observer falling into a black hole be able to witness any future events in the universe outside the black hole?

I know someone or something sucked into a black hole could not survive, but is the bending of light so immense that an observer falling into a black hole will be able to witness any future events in ...
11
votes
1answer
739 views

How does neutron star collapse into black hole?

We know the spectacular explosions of supernovae, that when heavy enough, form black holes. The explosive emission of both electromagnetic radiation and massive amounts of matter is clearly observable ...
11
votes
1answer
139 views

Future of CMB observations: How will our knowledge of the early universe change?

The Planck satellite has been presented and awaited for a long time as the ultimate experiments for measuring temperature fluctuations in the cosmic microwave background (CMB) over the full sky. One ...
11
votes
1answer
165 views

Our galaxy, the Milky Way, forms part of a galaxy group called The Local Group. What are the parameters that dictate what a galaxy group is?

Are there different classifications or just the one? How does our galaxy group compare with others?
11
votes
1answer
213 views

Inflation cosmology: slow-roll inflation versus tunneling between two vacua

In slow-roll inflation models, the early inflation of the universe is driven by the flat non-zero part of the inflaton potential, and it ends as the ball rolls down the cliff and the potential energy ...
11
votes
1answer
147 views

What is the current accepted theory as to why Venus has a slow retrograde rotation?

According to this NASA overview, the planet Venus is unique (amongst the major planets), Venus has a slow retrograde axial rotation, taking 243 Earth days to make one rotation (which is longer than ...
11
votes
1answer
153 views

How stable are Lissajous orbits?

Now that the Gaia Space Telescope is on it's way to the Sun-Earth L2 Lagrangian point (SEL2), I start wondering about the stability of Gaia's orbit there. The Planck Telescope is already there, as was ...
11
votes
5answers
305 views

What is in the center of the universe?

If the universe has formed & originated by a Big Bang Explosion, then there must be empty space left in the center of the explosion site, as all the matter is travelling at tremendous speeds away ...
11
votes
3answers
266 views

Why do (most of) the planets rotate counterclockwise, i.e. the same way the Sun does?

Referring to the mechanisms explaining the solar system formation and to the initial rotation of the gaseous cloud that collapsed, I understand easily why the planets orbit the Sun the same way this ...
11
votes
1answer
116 views

Dark Matter Particle Candidates

Dark matter appears to dominate the matter component of the universe as compared to luminous, or baryonic, matter. Though it does not interact electromagnetically (it doesn't absorb, scatter, or emit ...
10
votes
6answers
5k views

What will happen to life on Earth when Andromeda and Milky Way galaxies collide?

It is said that, Andromeda and Milky way galaxies are coming close to each other with the speed of approx $400000 \ km/hours$. They will be together in the next $4 \ billion years$. What will ...
10
votes
5answers
386 views

Do we know the exact spot where big bang took place?

If you rewind the universe back 14,7 billion years, all matter were in one spot, and then started expanding. Do we know where this is in reference to our own solar system? And is there anything there? ...
10
votes
3answers
343 views

How do we know dark matter/dark energy exists?

I've never quite understood the theory behind why dark matter and dark energy exist. I know it has something to do with gravitational pull being stronger than what we calculate it SHOULD be, could ...
10
votes
4answers
227 views

How would I measure that I'm at a pole?

How would a person measure that he is at a planetary pole? My first inclination is to use a sextant to ensure that the Sun remains at a constant inclination. However, due to the orbit around the Sun ...
10
votes
3answers
109 views

What is there in the intergalactic space?

What bodies can be encountered way outside galaxies - far beyond the farthest edges of galaxies, in the deep space between them? Are there single, galaxy-less stars, giant clouds of gas more dense ...
10
votes
3answers
715 views

How big would the asteroid belt planet be?

As I understand it, the asteroid belt exists because the gravitational force of Jupiter prevents the asteroids from accreting (is that a word?) into a planet. If, however, Jupiter didn't exist and ...
10
votes
2answers
318 views

Why does the Earth have a tilt of ~23°?

Is there a reason that the Earth has the tilt that it does (~23°)? How do we know which way is supposed to be 0°? Does this tilt have major consequences on the planet? Has it changed and will it ...
10
votes
3answers
1k views

What is the distance that the Moon travels during one orbit around the Earth?

What is the distance that the Moon covers in one orbit around the Earth, and does it always take the same amount of time, or does it fractionally differ on each revolution?
10
votes
2answers
261 views

How exactly is our universe mapped?

Watching this youtube video shows that our planet is nothing more than dust in the wind. At the 2:50 mark in the video, you will see a view of the whole Milky Way. At the bottom you will see this ...
10
votes
2answers
511 views

Where does the solar system end?

This is a question I've heard many times in the past, and a quick search of the site says it hasn't been asked here, so I figured I might as well ask (and answer) it. I know that it is rare for ...
10
votes
2answers
1k views

What is the formula to predict lunar and solar eclipses accurately?

A number of ancient civilizations had devised methods to predict exact dates and times of such eclipses, marking them as important events. Hence I assume the predictions were based on calculations, ...
10
votes
2answers
309 views

Do other planets in our solar system experience eclipses or is this unique to Earth?

Here on Earth we get to experience lunar and solar eclipses. Is this pure coincidence that everything happens to line up? Do other planets in the solar system experience this phenomenon or is this ...
10
votes
3answers
312 views

How was the core temperature of the Sun estimated?

It was estimated that the heat inside the core of the Sun inside around 15 000 000 °C - this value is extremely enormous. How did scientists estimate this value?
10
votes
2answers
74 views

How does the evolution of a solar system not break the second law of thermodynamics?

Please forgive: I am a layman when it comes to physics and cosmology, and have tried finding an answer to this that I can understand, with no luck. As I understand it, the solar system evolved from a ...
10
votes
1answer
105 views

Why does the Moon seem larger when it is close to the horizon? [duplicate]

I've noticed that when I look into the sky at night, sometimes the moon appears very large near the horizon. Sometimes it also looks like it has a yellow tint. Is this the light rays bouncing off ...
10
votes
1answer
882 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 ...
10
votes
2answers
690 views

Is it Possible for Planetary Bodies To Exist In Close Proximity Without Adverse Effects?

There are several sci-fi movies where planetary bodies are shown in the sky in order to indicate that the characters are on an alien planet. A good example is in Predators (2010): Is it actually ...
10
votes
1answer
125 views

Will Neptune be visible with the naked eye if I am standing on its satellite

Assume that I am standing on one of the many satellites of Neptune. Will I be able to see the planet with my naked eyes (without any sort of visual aid). If I was to stand on Moon I would be able to ...
10
votes
2answers
176 views

Dimensions of a black hole

How big can a black hole become and how small can a black hole become?(minimum and maximum dimensions of a black hole)
10
votes
1answer
84 views

How hot can a planet be?

Given that some exoplanets, particular "Hot Jupiters", orbit very closely to their parent star, how hot can these planets become? What is the hottest exoplanet discovered so far?
10
votes
1answer
191 views

Why does the Moon stablize Earth's axis?

In an academic study titled 'The Moon and the Origin of Life on Earth' it is said that 'If the Moon did not exist, the orientation of the Earth’s axis would not be stable, and would be subject ...
10
votes
1answer
377 views

Why do some planets have rings?

Some planets, specifically Jupiter, Saturn, Uranus, and Neptune in our solar system, have planetary rings. Why do some planets have rings? How are they made and from what? Most importantly, will I ...
10
votes
1answer
1k views

How can I collimate a dobsonian telescope with a laser collimator?

I've had a dobsonian telescope for a while now, but I've never been able to collimate it. I thought I had it collimated once, but when I looked through it the star didn't look right, it looked kind ...
10
votes
2answers
113 views

How hot must a star get before it is considered to be a star?

How hot must a star get before it actually becomes a star? Why does it need to get so hot? Please find an official site to quote from, if you can.
10
votes
1answer
259 views

Explaining Dark Matter and Dark Energy to layman

With my little knowledge, I know this: Dark Matter The center of a galaxy controls/attracts its objects (stars, planets, comets etc.) towards itself because of gravity. But the mass of the center of ...
10
votes
2answers
341 views

Why do stars appear to twinkle?

Sometimes at night you will look up to the stars and they will appear to twinkle, getting brighter and darker in bursts. Why does this happen? Is this because of our atmosphere? Would they twinkle ...

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