# All Questions

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### How big do comets get?

If my understanding is correct, Chury, the best explored comet so far is rather on the smallish side as comets go. Most comets observable with naked eye were so because they flew close to Earth, not ...
109 views

### What is in the brightest area of the night sky?

When I look up in the night sky, I assume the brightest area, commonly known as "The Milky Way", is the Galactic Center of our home galaxy. But then I stumbled upon this illustration, which seems ...
252 views

### How can we be 13.2 billion light years from another galaxy?

How did we get 13.2 billion light years from the faraway galaxies being discovered with Hubble? If we all started near each other at the Big Bang, and we all travelled slower than the speed of light, ...
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### Is there any way a planet could form independent of a star?

I just recently heard that there are currently no theoretical models that support planet formation without a star, but I can't remember where. So, I thought I would request all of your expertises. ...
152 views

### Standard practices and models for generating the ephemerides of the solar system

I am familiar with the theory on generating the positions of the members of the solar system, but have been unable to find out the standard practices and methods of professional astronomers in ...
424 views

### Is it possible that a ultra-large portion of the space we live in is already inside a black hole? How could we refute this?

Trying to wrap my head around some concepts involving the very large gravitational fields of black holes, and what the gravitational gradients look like on a cosmic scale. I'm familiar with the Great ...
123 views

### Calculation of Horizontal Coordinates

Given a fixed coordinate location on Earth (i.e. a latitude and longitude), and a fixed equatorial coordinate location of a particular astronomical object in the sky (i.e. right ascension and ...
594 views

### Why is right ascension measured in hours?

When viewing star maps in Stellarium, I noticed that the meridians of the equatorial grid were denoted in hours and not degrees, and that always puzzled me. Why did astronomers choose this system? I ...
262 views

### How are the masses of celestial bodies determined?

I was scrolling through the list of moons of Jupiter and I wondered how astronomers where able to determine the masses of those objects. When I tried to google it I meanly found results of people ...
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### Our universe the surface of a 4-dimensional sphere?

The cosmic microwave background that we observe uniformly around us is usually explained by assuming that our universe is the surface of a four dimensional sphere. That way the uniformity makes sense ...
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### How far apart can two people watch the moon simultaneously?

Obviously there's a limited part of earths surface where the moon is visible at any given time. I imagine the area of this surface would be a lot smaller than the area where the sun is visible at any ...
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### How would light from a blue or red star affect the way we see?

How would things look if we saw them through the light of a blue or red star? Would there be any changes?
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### What is the maximum number of planets in the habitable zone?

At present, it seems like we are alone in our solar system. How many earth-like planets would fit into the habitable zone of the solar system? The orbits should be stable for quite a time, i.e. for ...
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### What happens to the energy from a GRB?

A gamma ray burst produces somewhere around 1044 J of energy, according to Wikipedia. Only a small portion of that energy will be absorbed by other objects. The rest of that energy will go on to ...
609 views

### How to plot orbit of binary star and calculate its orbital elements?

I have a set of dates, position angles ($\theta$) and angular separations ($\rho$) for visual binary star. For example: ...
154 views

### What are the next planned space telescopes?

We've had hubble for two decades. Its become the most famous space telescope, and lately Kepler seems to be running for the second place. Are there any more powerful, better telescopes planned for ...
2k views

### Most important feature of a telescope

I was taking an astronomy test, the following question came up: The most important function of the astronomical telescope is: Resolving power Light gathering power magnifying power ...
291 views

### What is the direction of a comet's dust tail before and after perihelion?

I recently created a visualisation of comet ISON's orbit. However, I received a critique that the dust tail of the comet should be pointing away from the Sun after perihelion. As far as I know, the ...
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### Is there any real chance of getting hit with a meteorite if we build a base on the moon?

I've been reading an article today on how the European Space Agency (ESA) has an interest in building a space village on the moon which will be 3D printed and assembled by robots. Eventually people ...
610 views

### Do all planets have a molten core?

As we know, according to Wikipedia on Earth's inner core: The Earth's inner core is the Earth's innermost part and according to seismological studies, it is primarily a solid ball with a radius of ...
164 views

### Best approximation for Sun's trajectory around galactic center?

What is the current best approximation for the path the Sun takes around the center of the Milky Way? I have found some information on the approximate position of the Milky Way's center, the speed of ...
173 views

### Does Mars contain more iron than the Earth?

Is the reason Mars is red because its surface contains a lot of iron? (When dirt is red on Earth, it is sometimes caused by a high amount of iron). If so, does Mars contain more iron than the earth?
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### If we found evidence of life on Mars, how would we know that it originated on Mars rather than Earth?

Consider this scenario. One of the probes sent to Mars either very soon, or within the next century, finds conclusive micro-fossil evidence that life once existed on Mars. One theory today that is ...
149 views

### Could an impact have resurfaced Venus 300 million years ago?

Venus surface isn't older than about 300 million years. The only explanation I've come across is that some kind of global volcanism resurfaced the planet. But couldn't it have been an impact event? A ...
59 views

### Is the Astronomy community still concerned about the lumpyness of matter distribution in the universe?

A decade or so ago, when I was still a science undergrad, one of the open questions in astrophysics was to explain the uneven distribution of galaxies in the observable universe. That is, why did the ...
287 views

### Has the conjunction between Venus, Jupiter, and Regulus only occurred twice in 2,000 years?

I recently heard the claim that mid-July, the "Star of Bethlehem" formed for the first time in 2,000 years, where the Star of Bethlehem is a three-way conjunction between Venus, Jupiter, and Regulus. ...
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### Are trojans in L5 more likely than in L4?

Mars has much more trojans in L5. Does it reflect a common pattern?
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### How/where to check where the Sun is (constellation)?

I would like to check in which constellation the Sun was in at some time in the past, any recommendations how to do that?
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### How likely is it that the Sun will destroy our electric society?

Given the studies of the Sun and similar stars and the most impressive understanding of its physics, is there any kind of probability distribution for its dangerous behavior? There are also some ...
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### 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 ...
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### 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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### Time period in which a planet rotates

I notice that Wikipedia give two contradictory terms for the time period in which a planet rotates in relation to an infinitely-distant object. In one place this is called a "sidereal day" and in ...
269 views

### Sky Glow calculations

I am leading a project for my High School NASA Club, and am looking for some advice. The goal of our project is to use a Raspberry Pi to control a camera that takes photos of the sky, and uses the ...
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### Would bagging an asteroid destroy valuable science about it?

NASA has a plan called "Asteroid Redirect Mission option A". It would robotically put an asteroid of a few meters diameter in a bag and push it into reach of astronauts for thorough examination. 44 ...
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### Is it possible for a person to not see the new moon at different places on earth?

It is known that theoretically we see the same moon phase everywhere on the earth, but practically I see that people are unable to observe the 0.8% waxing crescent at different places on earth. This ...
134 views

### On analogies between gas and stellar systems

Analogies between (typically) ideal gas and stellar systems are not only intuitively valid to some extent, but have been established and used in the studies of stellar clusters and galactic systems, ...
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### What does observational evidence say about the number of protoplanets believed to exist in the early solar system?

Currently, the solar system has 8 major planets, a handful of dwarf planets and a plethora of asteroids, comets and natural debris, and of course, a rather locally dominant star (the Sun). There are ...
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### Is there any evidence that the Gas Giant planets in our solar system are experiencing orbital migration?

Planetary migration is defined by Lubow and Ida (2010) in their article Planet Migration as the process by which a planet’s orbital radius changes in time. The main agent for causing gas giant ...
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### How much oxygen did the Warwick/Cambridge study find in the rocky debris around white dwarf GD 61?

There are several articles out saying that a Warwick/Cambridge study of ultraviolet spectroscopy data from the Cosmic Origins Spectrograph on the Hubble Space Telescope found a large amount of oxygen ...
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### Current limitations in radio-astronomical spectrometry analysis of local interstellar cloud's hyperfine structures

I've been trying to wrap my head around capabilities of current radio-astronomical spectrometry technology to isolate not too distant tenuous sources, say, chemical composition and density of the the ...
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### Is there a variation of ISO 8601 for julian calendar dates?

If I want to write a date in the Gregorian calendar, I can write it in the ISO 8601 format; today would be 2016-02-20. The advantage is that there are many parsers available to let computers read in ...
359 views

### why does pluto have a high orbital inclination

Pluto has a high orbital inclination compared to the planets in our solar system. What has caused Pluto to have such a different orbit -- was it always like this, or did something happen to make it ...
193 views

### Lack of planets in the Oort Cloud

With the current news about the possibility of a planet in the Oort cloud, I was thinking, why is the matter in the Oort cloud distributed so? It makes sense that inside the planet region there is not ...
91 views

### Orbital resonances and position of planets

I am interested in quick generation of planetary systems for programs similar to Space Engine or Pioneer Space Simulator. As far as I understand, formation of planets is a complex process and the ...
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### Do star systems stripped from galaxies have different expected behavior?

Another way of stating this question: Does the fact that a star system (or comparable concentrated mass) exists in a galaxy affect its long-term evolution, in terms of expansion, contraction, ...
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### To what extent are structure formations unexplained?

I hear conflicting claims about our understanding of the structure formation in our universe. I heard that ΛCDM explaines well the large scale structure of the universe i.e. Comparison of the ...
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### If we were to see the Sun with our naked eyes from the Orion belt, would all planets be encompassed inside the star? Is this calculable?

When we see a star it looks much bigger in diameter to us than it really is, this picture (extracted from here) explains what I mean: Notice that the point we see in the skynight, represented by ...
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### Calculate angle of inclination for a certain angle in a planet's orbit?

The background is that I'm trying to write a computer program to show at what angles each planet would be able to be seen transiting in front of the sun from an observer outside our solar system. My ...