33
votes
5answers
4k views

9th planet location?

I've seen a number of news reports indicating there is likely a 9th planet in our Solar System, something with an orbital period of between 10k-20k years, that is 10 times Earth's mass. I haven't seen ...
4
votes
1answer
53 views

We are sure that there are no brown dwarfs closer than ______

I don't quite know how to word this question. How close could a brown dwarf be to us and have gone undetected until now? Or maybe, with what probability are we sure that there is no brown dwarf ...
14
votes
2answers
382 views

How long should it take for us to observationally determine if Caltech's Planet Nine is really there?

Caltech just released a report that says there is possibly a large (10 earth mass) planet in a remote orbit (10 - 20 thousand year) that explains a lot of observations of Kuiper Belt objects. How long ...
1
vote
1answer
45 views

how to get image coordinates of source points in saoimage ds9?

I loaded my fits image to saoimage ds9. Then, Analysis->Catalogs automatically brought up source locations. how can i get xy image coordinates of this source locations?
1
vote
1answer
52 views

Why do PMS stars on the Hayashi track remain at a constant temperature while they contract?

Why do pre-main-sequence stars on the Hayashi track remain at a constant temperature while they contract? I've read the Wikipedia article, so no need to repeat the derivation. What I took away from ...
0
votes
0answers
61 views

Formulas for gravitatitional equilibrium

I am trying to calculate at which point gravitational equilibrium sets in for various bodys (planets stars neutron stars etc.) assuming they are perfect spheres. However the radius i get is not equal ...
4
votes
1answer
43 views

Why do proto stars on the Hayashi track get dimmer as they contract?

Why do proto stars on the Hayashi track get dimmer as they contract? My expectation is that they would get hotter and brighter the more they contact. Why is this wrong?
1
vote
2answers
27 views

How does time “add up” for observers outside of and travelers inside of a Krasnikov tube?

A ship travels 99% of c from Earth (leaving at Time A, say 2016) to Destination Star (arriving at Time B, say 2020, accounting for relativistic effects) to stretch the tube, leaves a buoy at ...
1
vote
3answers
103 views

If sun steals comets from other stars, then what is the primary source of comets?

I heard some theory that sun may steal materials such as comets from neighbouring stars, is it true? But if is true, what is the primary source of those comets? Especially "who" creates them instead ...
1
vote
0answers
88 views

A phonecall inside a blackhole

I was wondering what a phone call would be like entering or falling t=into a black hole. Due to the massive density of the black hole and time would feel slower, how would that appear to the person on ...
2
votes
3answers
130 views

Closest point on Earth to a planet?

I'd like to be able to find the latitude and longitude on Earth (assuming a sphere is fine) which is closest to Pluto at the current time (or where Pluto is directly overhead). Is this possible with ...
0
votes
1answer
28 views

Could the Earth be used to cast an arago/poisson spot on something

There's a potential design for a space-based telescope that uses a large opaque circular disk in place of a transparent lens to focus light for analysis. It uses the light that bends around the disk ...
0
votes
3answers
108 views

View from inside the black hole

If an observer is falling toward a black hole with its face away from singularity then what will he observe after crossing the event horizon? The reason that why I am asking this question because as ...
1
vote
2answers
116 views

What is the Maximum Speed that can be acheived Because of Acceleration Due to Gravity?

Planets and other bodies in the universe have different ranges of gravitational fields. What is the maximum speed that can be achieved because of acceleration due to gravitational field. In other ...
0
votes
1answer
58 views

The relation of the lit side of the moon and the sun

During different days when both the sun and the moon are seen I notice that the axis of the lit, illuminated, side of the moon does not pass through the sun there is some degree of diversion. Why?
0
votes
1answer
59 views

Second Big Bang [duplicate]

Just say you are immortal and will live forever. Since the universe is claimed to be unstable, what would happen after it ends? Would all of the universe's mass just fly back into another compressed ...
5
votes
2answers
85 views

Are there ever any simultaneous transits of both Mercury and Venus as seen from the Earth?

Transits of Mercury happen fairly frequently due to its short period, but transits of Venus are less frequent. I've looked over the data available to me and found that there have been transits of ...
1
vote
0answers
19 views

Which moons have cold traps? (i.e. low ecliptic inclination in orbital and rotational axes)

Both the Moon and Mercury have polar cold traps in polar craters, with signs of volatiles. This is of course not as interesting on a moon in the outer Solar System which consists of volatiles anyway. ...
0
votes
0answers
23 views

About bias in sidereal time (used by astronomers)

I came up on this stanza in various websites when looking up on experimenter bias. It says "If the signal being measured is actually smaller than the rounding error and the data are over-averaged, a ...
4
votes
1answer
110 views

What lies at the center of a neutron star if any?

What does the current theory tell us about what is going on at the core of a neutron star, I'm expecting a black hole hopefully I won't be disappointed!
0
votes
0answers
22 views

Percentage of galaxies rotating with trailing arms

I am looking for the percentage of galaxies that rotate with a trailing arms. I know that only a small percentage of galaxies rotates with leading arms and would like to know whether there are any ...
4
votes
1answer
62 views

Sun as our Supergiant

Let's talk about the time when our sun becomes a supergiant. We know that our solar system may get destroyed or it may get affected due the large mass of the supergiant and also due to the large ...
0
votes
1answer
64 views

Behind a black hole

Nothing can escape a black hole , not even light. But what if anything approaches a black hole from behind..... Correct me if I'm wrong! Do black holes have front and back? If yes then does they suck ...
2
votes
2answers
65 views

Why do stars seem not to move relative to each other?

Whilst I understand why stars move across our skies,(Earth rotation) I struggle to understand why they do not appear to move relative to each other. To explain: Take the best know constellation the ...
1
vote
1answer
49 views

Obtaining stars vector position in relation to the center of the galaxy at a given date

How can someone obtain such vector, for stars in the Milky Way? Input should be star data (from a catalog, eg: Hipparcos) and Julian Date. Output should be a Vector Position (in pc) in relation to ...
3
votes
1answer
48 views

Stability of orbital resonance

Recently I've become more interested in the topic of the stability of planetary systems. I have been reading about it and it seems that orbital resonances play an important role in the stability of ...
0
votes
0answers
9 views

Is atmospheric turbulence irrelevant for ExoPlanetary transits and radial velocity measurments?

Atmospheric turbulence is known to scatter photons in a quasi-random way along their path throughout the atmosphere, resulting in lower imaging resolution than would have been anticipated by ...
0
votes
2answers
43 views

Reasoning questions on eclipses

why doesn't a solar eclipse occur in every new moon? I know one reason is the inclination of Earth's orbital plane. But is there another?
0
votes
3answers
44 views

What is the centre of rotation of Pluto?

I know that Pluto and Charon have been found to circle round each other, hence the reason Pluto is no longer a planet I believe, which would mean that the centre of rotation is an arbitrary (!) point ...
1
vote
1answer
36 views

Is there a single, most prominent helium line?

There's a prominent spectral line at ~1420 MHz caused by hydrogen. From what I can tell, this is the most notable electromagnetic emission from hydrogen in radio astronomy. Is there an equivalent ...
5
votes
3answers
105 views

On the cosmological principle

Just more of a conceptual question on the mutual inclusivity of the cosmological principle. That is to say, I was wondering if it were possible to have a Universe that were isotropic but NOT ...
1
vote
4answers
94 views

What do we mean by Sunrise and Sunset?

If the Earth rotates on its own axis, then what do we mean by sunrise and sunset?
0
votes
1answer
51 views

Black holes and time relation

Why Is it said that if someone is being sucked inside a black hole then he/she may see that time is running slowly?
0
votes
0answers
36 views

Time and velocity [migrated]

Suppose two cars are traveling at a velocity of c/2 (c=velocity of light) in two straight lines parallel to each other but in opposite direction in vacuum.... Then what will a person sitting in one of ...
0
votes
2answers
78 views

What is the future of our universe?

Is the universe heading towards a Big Freeze, a Big Rip, a Big Crunch or a Big Bounce? Or is it part of an infinitely recurring cyclic model?
1
vote
2answers
108 views

Are we sure solar cycle is not related to the orbit of Jupiter?

Are we still debating the relationship between Jupiter and solar cycle? If not, what is the common or mainstream opinion about this topic? Or in other words, have we disproved the solar cycle is ...
0
votes
0answers
33 views

What is the shape of the Sun's orbit around the Earth taking into account elliptical orbits?

Consider the non-inertial frame that is at rest with respect to the Earth's revolution around the Sun. (Ignore the Earth's rotation around its own axis.) My question is, what is the shape of the ...
0
votes
3answers
91 views

Why is it that we can"t feel how fast the Earth is moving? [closed]

We are moving like 100,000 mph. And why do we not fall off going that fast
0
votes
2answers
33 views

Do massive OB stars accrete mass the same way as the black holes they turn into do?

It is often said, in spite of sci fi often having illustrated the opposite, that stellar mass black holes do not gravitationally attract material in their environment into themselves anymore than a ...
3
votes
0answers
38 views

What is the frequency distribution for luminosity classes in the Milky Way Galaxy?

I'm working on a game concept that does some mild simulation of realistic stellar classes and luminosities. In particular, I'd like to roughly model the general frequencies of the classes and ...
0
votes
0answers
15 views

Star Formation in the future [duplicate]

From what I understand stars form in dense clouds of hydrogen and helium molecules. Only so much hydrogen and helium were "created" from the Big Bang or rather formed if you may. Is it conceivably ...
0
votes
0answers
21 views

Resources on planetary stability

I am a fifth (and last) year undergraduate student in Physics with good level of Mathematics formation and basic Astrophysics formation. I recently read some theories about Solar System formation and ...
3
votes
1answer
94 views

What if we throw two solid objects parallel in space? Do those two objects have any chance to collide with each other?

What will happen if just throw two solid objects (for example, solid footballs) parallel in outer space and those two objects are floating and going far away in the universe. So is there any ...
0
votes
1answer
32 views

Eclipse — Solar and Lunar

Q. Why is solar and lunar eclipse not seen from all parts of the earth at the same time? I think its because of the revolution of the earth but i am not sure. I want a more reliable answer.
-6
votes
2answers
51 views

How do we know so much about the sun since we can't go near it? [closed]

I am wanting to learn everything there is to learn about the Sun from our solar system to the ends of the universe.
5
votes
2answers
166 views

How unusual is the solar system?

In Isaac Asimov's Foundation series, the main characters are looking for the long-lost Earth. There are two major features of the solar system that seem to make it unusual among the millions of ...
3
votes
4answers
84 views

Is it possible for a virus to come from a space rock?

So I am not a true scientist and I was just wondering if an extraterrestrial rock from space can have some dangerous unidentified virus or bacteria that can be deadly and wipe out the Earth if it not ...
9
votes
1answer
443 views

Is the Sun really a medium size star?

It is often said that the Sun is a medium size, or even dim star, but is that true? According to this list of stars within 21 light years, only six stars are brighter than the Sun out of the closest ...
0
votes
0answers
32 views

Calculating AZ and ALT from RA and DEC: values are slightly different from Stellarium

I'm developing my own planetarium software and I using Stellarium to check if the values a get from my software are correct or not. All values are roughly equal, being different only in the seconds. ...
3
votes
1answer
91 views

How can we hear the sound of the Sun?

Recently NASA has revealed that they have recorded the sound of Sun. They say that it produces a sound like "Om". I can't understand how they can hear it. To the best of my knowledge, sound can't ...

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