8
votes
1answer
47 views

On (minuscule) dark matter production in supernovae

It is believed that dark matter is made of particles, which interact with matter only weakly and gravitationally. One common candidate for dark matter are so called WIMPs. WIMPs, specifically, are ...
8
votes
1answer
75 views

What implications do younger Earth and Moon have on Late Heavy Bombardment genesis hypotheses?

The Late Heavy Bombardment (LHB) or the Lunar Cataclysm is when the inner solar system, including the Earth and the Moon, underwent multiple and sustained heavy impacts early in their history (around ...
8
votes
1answer
52 views

What is the current accepted theory as to why Mercury, despite its size, has a similar density to Earth?

According to the NASA web page overview about Mercury, despite the planet being just a bit larger than our moon, it's density is about 98.4% of Earth's. This high density suggests a comparatively ...
7
votes
4answers
137 views

What is the most extreme weather found on another planet?

On Venus, there is really inhospitable weather, as well as within the gas giants in our solar system. Are there examples of even more extreme weather on planets found in other solar systems than ours? ...
7
votes
2answers
301 views

What was the length of year 1 million years back?

We know that the universe is gradually expanding and this indirectly means that the gravitational force between sun, earth, planets and other stars (roughly anything in the universe) is gradually ...
7
votes
3answers
126 views

Why is the interstellar medium so hot?

On this link, it states the following: "large assemblies of galaxies that are permeated by even larger amounts of diffuse gas. With temperatures of 10 million degrees or more". How are these ...
7
votes
5answers
139 views

Orbiting around a black hole

Is it possible (for either a satellite or a planet) to orbit around a black hole? Do they attract everything around themselves into the center? Or they just affect gravitational force just like stars? ...
7
votes
2answers
79 views

Moon orbits crossing each other

Some planets, such as Mars, have 2 or more moons. Giants, like Jupiter of Saturn have a lot of moons! How likely the orbit of one crosses another one's orbit? Is it possible for two moons to collide? ...
7
votes
1answer
128 views

Is it possible for a moon to orbit a planet floating free in the galaxy rather than orbiting a star

This article got me thinking, can a planet hold a moon in orbit if it is just floating in the galaxy by itself not as part of a star system? Can a celestial body even qualify as a planet if it is ...
7
votes
2answers
249 views

Why are orbits elliptical instead of circular?

Why do planets rotate around a star in a specific elliptical orbit with the star at one of it's foci? Why isn't the orbit a circle?
7
votes
3answers
89 views

What is the orbital path of the newly discovered star-less planet PSO J318.5-22?

Recent results from Institute for Astronomy at the University of Hawaii at Manoa claim that there is a Jupiter-sized gas giant planet that is independent of a star about 80 light-years from Earth. ...
7
votes
2answers
156 views

Why can you see the space station on some days but not on others?

In my area, from December 17th - 26th, you can see the space station every day, twice But from December 27th - January 6th, you can only see it twice My question is, why does it appear for ...
7
votes
1answer
82 views

Which is the closest exoplanet to Earth?

The closest star to Earth (after the Sun) is well-known: Alpha Centauri, 4.3 light years away. But what about the closest exoplanet to Earth, outside of the Solar System?
7
votes
3answers
161 views

Is the Jupiter-Sun system considered a binary system of some type?

Since Jupiter is very massive, it is the only planet (in our solar system) that has a center of mass with the Sun that lies outside the volume of the Sun. (Source) If Jupiter was a star, they would ...
7
votes
2answers
122 views

Is the rotation of the Sun and the rotation/orbit of the Moon around the Earth a coincidence?

While looking at sunspot information in connection with Amateur Radio, I found that the Sun rotates on a period from 27 days to 31 days. Its rotation is differential, at the equator it spins at a ...
7
votes
1answer
83 views

Age of the universe

We know that the universe is approximately 13.7 billion years old. What methods did we use to discover this? How sure are we about its accuracy?
7
votes
1answer
53 views

How fast do we travel through space?

Could someone give the rough estimates of speeds of our travel through space? I can easily find the two nearby ones: Earth's own rotation - depending on latitude, up to 40,075 km/24h = 463 m/s ...
7
votes
2answers
192 views

Why haven't Earth and Venus got any tiny moons? Or have they?

Why haven't some meteoroids gotten caught in Earth's or Venus' orbit? AFAIK most meteors are tiny fragments from comets. Shouldn't some comet tail sometime have passed Earth orbit at velocities ...
7
votes
2answers
30 views

Official registry of lunar placenames?

What's the definitive source for names of geographic objects on the moon? Reason: As a computer graphics project I've rendered a scene based on LROC terrain data. I want to know what I'm looking at. ...
7
votes
1answer
66 views

Appearance (popularity) 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 ...
7
votes
2answers
240 views

How long until we cannot see any stars from other galaxies?

Since all the galaxies are moving further away from each other at a faster and faster rate, eventually we won't be able to see stars from other galaxies. How long until we can't see stars from other ...
7
votes
1answer
72 views

What is the Lyman Alpha forest Used For?

The Lyman-alpha forest is an interesting feature found in the spectra of sufficiently distant objects. This series of absorption lines extends over a range of frequencies, and are a result of the ...
7
votes
2answers
46 views

What is the Neupert Effect?

This effect is frequently discussed in the context of solar time series. In particular, it a relationship between soft x-ray (thermal emission) and hard x-ray (nonthermal emission) from the Sun.
7
votes
1answer
70 views

Effect of Charon on Pluto

Even though Pluto is not known as a planet anymore, theroetically it has/had a moon, called Charon. I've heard about something that their size are so close to each other that while Charon rotates ...
7
votes
1answer
39 views

Why does mars appear to retreat across the sky?

If you plot the movement of mars across the Earth's sky it appears to move back on itself during its orbit. Why does it appear to have a loop shape from Earth?
7
votes
1answer
42 views

How would the pocket cellular clock work?

In a museum in Lviv, I saw a pocket cellular clock. I don't have a photo, but it was a small disc that had 2 or 3 filaments in it which were pointed at the stars (one of them was Andromeda, I think). ...
7
votes
1answer
116 views

Emulation of an Orrery

Orrery is a clockwork model of the solar system. I am trying to emulate one in 2D. Now, to emulate, I need to know what goes on inside. Can someone please explain the basic principle behind the ...
7
votes
1answer
74 views

How do we know Milky Way is a 'barred' spiral galaxy?

In reference to the question, "How can we tell that the milky way is a spiral galaxy?" The answers there clearly sum up the question asked. But Milky Way is not just a spiral galaxy. It is further ...
7
votes
1answer
105 views

Why can't we observe the Oort cloud with a telescope?

The Oort cloud is a hypothetical structure based on our observation of long-period comets. There are currently proposals to design probes to confirm the existence of the Oort cloud. Now, sending a ...
7
votes
3answers
125 views

Why are planets spherical?

I am a complete novice when it comes to astronomy, but someone asked me the above question casually. It seems as though planets are all roughly spherical, whereas other celestial bodies aren't ...
7
votes
1answer
50 views

Sources of Turbulence in the ISM

What sources of turbulence exist within the Interstellar medium (ISM)? Which ones are physically the most important for newly forming stellar systems?
7
votes
1answer
46 views

Crab Nebula Time Period

I've learned that the time period for a rotating neutron star, i.e., a pulsar is very accurate and can be used as an interstellar clock. But according to Walter Lewin's 8.01 Lec 19 on classical ...
7
votes
1answer
68 views

What is the largest recorded solar flare?

For the purposes of this question I would interpret the word "recorded" as loosely as possible meaning that historic records such as ice cores or tree rings would count. Also what effect did such a ...
7
votes
1answer
35 views

What are Trojan Asteroids and where are they located?

Asides from the main Asteroid Belt, there are Trojan Asteroids - what are these and where are they located?
7
votes
2answers
96 views

Can moon set after being up when due north? (pseudo circumpolarity)

I'm in the northern hemisphere, facing north, and notice that the moon is due north (azimuth 0) and is still above the horizon, albeit barely. Does this mean the moon is necessarily circumpolar ...
7
votes
1answer
95 views

Do moons have moons?

Have we discovered any natural satellites of natural satellites of planets or dwarf planets? Even very small, or relatively short-lived - e.g. ringlets around Saturn's moons, some meteorites orbiting ...
7
votes
1answer
55 views

Do planetary rings have geometric bounds?

Are there any bounds on where a planetary ring can form and maintain orbit relative to the planet? Do they have to be in a circular equatorial orbit? Is there a min or max altitude, say with respect ...
7
votes
2answers
116 views

Where does the radiation in space come from and can we observe it?

I have recently been reading that space travel is strongly influenced by "space radiation" and how it poses a threat to human space exploration. Does this radiation originate from stars like our Sun, ...
7
votes
1answer
110 views

What is the current theory for the formation of the Earth's Moon?

Given that the Earth and Moon are often said in the literature to have very similar geochemistry, what is the current theory as to how the Earth's Moon formed?
7
votes
1answer
203 views

How does moonrise/moonset azimuth vary with time?

In my tenacious attempts to observe moonrise (surprisingly difficult in a poor weather heavily urbanized hilly area with frequent bad smog, with busy work schedule and a bicycle) I was frequently ...
7
votes
1answer
49 views

What is the relevance of the Tropics and the Polar Circles? Do they Exist on other planets?

The middle line is the equator, the second and fourth line are the tropics, the first and fifth are the polar circles. What is the relevance of these bands on Earth? Do these exist on other ...
7
votes
2answers
52 views

What is the difference between asteroids, comets and meteors?

Some celestial objects seem to be referred to as asteroids, some as comets, and some as meteors or meteorites. What is the distinction between all of these different objects? Are any of them the ...
7
votes
1answer
70 views

What is the current accepted theory for Neptune's immense wind speed?

According to "Neptune: The Other Blue Planet in Our Solar System" (Choi, 2010), Neptune, despite its great distance from the sun, is the windiest planet in the solar system, with winds reaching ...
7
votes
1answer
101 views

What can be seen with a 4.5" telescope

I just got a 4.5" Newtonian reflector. The skies haven't been clear where I live lately so I've only been able to use it to see the moon and Jupiter (I was also able to see the Galilean moons). A ...
7
votes
2answers
84 views

How are Galaxy Super Clusters Generated

I have seen pictures of clusters of galaxies, usually used in regards to theories of dark matter and galaxy formations. One of the most famous ones has the perceived shape of a stick-figure. If I am ...
7
votes
1answer
69 views

Might Oort cloud comets be exchanged between solar systems?

Considering their distance from their parent stars, might Oort cloud object such as comets be exchanged between passing stars (assuming that other stars have similar Oort clouds)?
7
votes
1answer
37 views

How can I measure the mass of eclipsing binary stars?

Is there any method to measure the mass of eclipsing binaries without using Doppler shift effect?
7
votes
1answer
122 views

How exactly is the Initial Mass Function (IMF) calculated?

The Initial Mass Function (IMF) is the empirical function which describes the initial masses of a population of stars. My questions are, 1) What are the various IMF's which are used? 2) For each, ...
7
votes
1answer
65 views

Timescale of ignition of a protostar?

What is the timescale of start of nuclear fusion as T Tauri type star transforms into a Main Sequence star? Wikipedia article on T Tauri type stars mentions: Their central temperatures are too ...
7
votes
1answer
152 views

What reason is there to doubt the existence of the hypothesised planet Tyche in the far distant solar system?

Please note, I do not necessarily believe in its existence, just after a scientific (hence, non-Wikipedia) reasoning to doubt the planet's existence, other than the "we would have seen it" argument. ...

15 30 50 per page