# All Questions

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### Utilization of data from satellites mantained by India [migrated]

What are the prerequisites to utilize the data from 'astrosat' or 'mangalyaan'. My aim is to check how useful the data generated by an Indian scopes are? I could not make any sense in the catalogs.
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### What is Color Index?

I found this Wikipedia page on this property called color index. Unfortunately, I could not find a source that explains this property well. My interpretation is that color index is the brightness ...
99 views

### How do I get from Star Atlas to real life?

This question is about finding the elevation and bearing of a given star at a particular time at Latitude 52N. I look up the RA and Declination of my star. How do I calculate its bearing and ...
32 views

### Equation to find distance between objective and eyepiece

I have a home made astronomical telescope with 100 cm objective lens and 5 cm eyepiece.when viewing an object in infinity the distance between eyepiece and objective is 105 cm. So how could I ...
108 views

### Visibility of human activity on the moon

In this video the host of Test Tube Plus states that you can go out a buy a laser, point it at the moon, and see the retroreflector left by the astronauts. When you point at the right spot you'll ...
153 views

### How Are Radioactive Decay Rates Influenced by Neutrinos - On Earth and Other Dense Planets

I read a science report recently that mentioned an accidental discovery where radioactive decay rates shifted slightly slower in advance ( about a day and a half) of solar storms or in sync with sun's ...
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### Method to determine the amount of reflected starlight necessary for an exoplanet to be visible from a given distance/angle?

What is the method to determine the amount of reflected starlight necessary for an exoplanet to be visible from a given distance/angle? (Not from occlusion but actually visible on its own.) Further, ...
122 views

### Can a gas moon exist?

Could a gaseous moon exist in the same way as a giant gas planet? All the moons in the solar system are rocky, or icy. Why shouldn't gas planets have gas moons?
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### Why some stars appear to move differently when viewing device shakes

I was looking at Arcturus with a pair of binoculars, and noticed that when they vibrate due to my heartbeat, Arcturus seemed to move differently than the other dimmer stars. I started playing with ...
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### Does the Sun orbit the Milky way in a (kind of) flat or inclined orbit or more of a sine wave? [duplicate]

I know it can't be a perfect ellipse or smooth orbit due to all the matter in every direction, and our Sun could be affected by a gravity assist of sorts if it passes close enough to another massive ...
188 views

### Precessing of the Earth

It's been known that the Earth's axial tilt varies from 22.5 to 24.5. Does this result in a wobbling while the value of the tilt varies about these two limits? If so, how does it affect the mechanics ...
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### What were the challenges for the ancients to observe the orbit of the Moon (instead of Mars)?

Astrophysics can be said to have been founded by Johannes Kepler around the year 1600. He based his break-through science on data of the position of Mars in the sky and disproved the ancient ideas ...
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### How well do planetary orbits fit with Johannes Kepler's in- & circumscribed Platonic solids?

In Mysterium Cosmographicum (1596) Johannes Kepler proposed that the relative distances between the orbits of the six ancient planets (six because heliocentrism had recently added Earth as one of the ...
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### Calculate time when star is above altitude 30°

To find the best observation time for an object, I'd like to calculate the time when it is 30° or more above the horizon. Local Sideral Time would be sufficient. To include that in my program, I need ...
156 views

### Can we compress any object to create black Holes?

In general, when a star runs out of nuclear fuel, gravity gets the upper hand and the material in the core is compressed even further and creates black holes. I am clear till here. Now the question ...
135 views

### Is a black hole heavier than the star from which it was created?

I did some googling around and couldn't get answer to a simple question of black hole mass compared to the star from which it was created. It is well known that giant stars burn very bright and ...
214 views

### How do we know that our galaxy is a spiral galaxy?

I know that our galaxy is spiral in shape, but I'm wondering how the scientists found out that our galaxy has a spiral shape. I don't think we can see the entire galaxy from telescopes on Earth, ...
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### Could a small Mars Cycler be used for repeated sample and big data transfers? [migrated]

Imagine rovers collecting samples on Mars and launching them to dock with a Mars-Earth transfer spacecraft. This vehicle would be in a Mars cycler orbit which passes near Mars and Earth every 7 years, ...
188 views

### What is the bluest narrow band filter mounted on ground based telescopes?

If we want to check a QSO's lyman alpha narrow band image, could a ground based telescope do that? I mean under the circumstance that its lyman alpha shifts to 3300A.
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### Where did everything come from?

Where did all the material and gas contained in our universe come from? If it was the size of a "coin," then it could not have contained all the matter that is in our universe today before the Big ...
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### How bright can white dwarf stars glow as they accrue matter?

I realize this is kind of general as it would depend on the size of the white dwarf and the rate of accrual. The general idea I got thinking about is what would happen if a white dwarf star - lets ...
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### How can the observable universe be so small if there are so many stars in it?

The observable universe has a radius of about 46.5 billion light years. That’s big but I just wonder how that can be big enough to fit in everything we know exists in the universe. There are hundreds ...
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### What is the share of stars in total radiation input of Earth?

Earth gets its radiation input primarily from Sun, then from reflected sunlight from Moon, and stars. Among these, what is the share of stars (or sources outside solar system) to this total radiation ...
144 views

### Did a piece of Halley's comet strike the Earth 1,500 years ago?

A friend showed me an article saying that there's evidence that a piece of Halley's comet may have struck the earth about 1,500 years ago. Is anyone here aware of such evidence?
80 views

### Is it accurate to compare comets to clouds and rain?

I'm trying to avoid an opinion-based question, so before I outline the comparison I'm proposing, I will qualify the specific facts that yield this comparison. By focusing answers on the relative ...
31 views

### Finding a location using the direction of shadow, UT and date approximately

Does anyone know how to find a location by using : the direction of shadow relative to the normal (for example azimuth angle) the Universal time (UT) and date I have a satellite image and I know ...
85 views

### Does time slow down because the universe is expanding at an accelerating rate?

If the universe is expanding at an accelerating rate, such that the galaxies' moving away from each other is accelerated, then time should also slow down. And when universe will accelerate to the ...
38 views

### What would be the maximum theoretically possible angular resolution?

I have studied some basic astronomy, but I have difficulty conceptualizing the physics of luminosity and optics. We use electromagnetic spectra to detect existence and properties of distant planets, ...
104 views

### Is there a yearly measurement of photon momentum from the sun taken by the moon? [closed]

I can't find how much photon momentum force the moon is receiving every year from the sun.Does the moon's mass,color,size and tidal lock with earth in a never changing phase a good source for this ...
122 views

### Stellarium 0.10.4: planet orbits change over time?

If I draw the orbit of Mars in stellarium 0.10.4 for 23 Sep 2015, it passes south of Chi Leonis: If I advance the date to 17 Oct 2015, however, the orbit of Mars correctly goes right through Chi ...
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### Why did the moon abruptly change positions in the sky?

Three or four weeks ago I was outside showing my neighbors how cool the moon was through a 'backyard' telescope in broad daylight (~8PM PDT). It was 3/4 of the way across the sky (setting behind the ...
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### could dark energy be a force coming from the hyperspace outside the universe?

It seems to me that the expansion of the universe is only being looked at one way. a repelling force, basically being the opposite of gravity. After pondering this for many nights, I began to wonder ...
272 views

### How to calculate a planet's current position within the solar system

I'm making an application that needs to calculate a planet's current position within the solar system - I don't want to calculate its position in the sky. For example, what I want to do is exactly ...
358 views

### Moon's orbit around the Sun

The Earth revolves around the Sun and the Moon revolves around the Earth. Out of curiosity I started thinking about the orbit of the Moon around the Sun and expected (assumed) it to be as follows: ...
54 views

### Estimates of exoplanets distribution consistent with current data

I am interested in current estimate of distribution of planets of various radii in various distances from their parent star. There is many sources, where one can find database of presently known ...
319 views

### What do we know about the lifecycle of the Milky Way (or any other spiral galaxy)?

I know that the Milky Way will collide with Andromeda in the distant future but based on what we know so far there is a supermassive black hole in the center of each galaxy and thus the Milky Way will ...
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### Does all of time already exist if so why can't we see it? [duplicate]

I've recently become fascinated with the theory of relativity and time. If all of time already exists, and there is no difference between past, present and future then what is preventing us from being ...
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### TIME TRAVEL-Can it be really done? [closed]

Is it posssible for us to time travel? Is light essential factor or the dark matter and dark energy?
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### Gravitational red hift vs Doppler redshift: Is the universe really expanding?

Is it possible that the redshift observed by Edwin Hubble is really from a gravitational redshift and the universe isn't expanding as he has predicted? What I think I know thus far is this: ...
134 views

### How many bodies can I see with a 90x telescope?

I am a 9th class student so I'm a beginner at using a telescope, hence please help me. How many bodies can I see using a 90x telescope? How will I know when and where I should point a telescope to ...
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### How long would it take for earth's core to cool down and solidify?

Would earth go the same way as Mars by first losing its magnetic field followed by its atmosphere as its core solidifies and cools down ? At what rate is the earth's core cooling down?. Is it slow ...
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### Formation and capture of Mars' moons, Phobos and Deimos

Mars's moons have the appearance of captured asteroids. How could this capture have taken place. An asteroid in solar orbit would need to loose some momentum to be captured. The gas Giants can ...
102 views

### Why does gravity increase in star formation?

When a star ignites ( ie. fusion starts ), the star maintains its form by balancing gravity's inward pressure, and radiation's outward pressure. I get that the fusion of hydrogen atoms releases ...
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### What exactly is a stellar association?

What exactly is a "stellar association" in the strict kinematic sense?
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### Is it true that chaotic inflation is the most popular inflationary model nowadays?

Old inflation was ruled out, and I think that Linde's New inflation has its problems. There's an astonishing number of inflationary models out there (more than 100?) and they're all too technical for ...
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### Do sungrazing comets leave a field of meteoroids near the Sun?

A large fraction (a third?) of all comets found (with observational bias thanks to SOHO) have been sungrazers, breaking up with perihelion of a few of Sun's radius. Is there reason to believe that ...
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### 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 ...
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### What is the color of Venus if it has no atmosphere?

Mars looks reddish and Mercury looks gray because they lack thick atmospheres and we can see their "real color" easily, how about Venus? Is the surface of Venus really yellowish in color?