All Questions

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How many satellites orbit the Earth? At what rate do they orbit the earth? [closed]

I was looking at a full moon the other night with my telescope and noticed a black dot move across the moon quite rapidly. This happened a few times and others who were with me were able to confirm. ...
2k views

How can we avoid needing a leap year/second?

Given the Earth's current speed around the sun and current rate & axis of rotation, what is the best way to keep time to avoid a leap year? How many hours should we have in the day and days in a ...
86 views

Why you use log to measure metallicity in galaxies?

For example, I saw the next expression for matallicity in a paper: $\log(O/H) + 12$. I understand O/H is the O(Oxygen) to H(Hydrogen) ratio but why is there the number 12? And why the logarithm?
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The battle over Gliese 581 and Gliese 667C?

In 2014, Robertson et.al. made a case that stellar activity is masquerading as planets (here and here) for these well known systems. In both cases, they claim that the only real planets discovered so ...
134 views

If an Asteroid was to strike the Earth, would it affect the Earth's rotation?

If an Asteroid was to strike the Earth, would it affect noticeably the Earth's rotation, and if so, how large would this Asteroid have to be?
107 views

Is any consensus forming on the solution to the “Lithium Problem”?

The "Lithium Problem" relates to the fact very-low-metallicity stars appear to have a Li/H ratio approximately one third of what would be expected. The ratio should be the same as the prediction from ...
181 views

If 50 tons or more of debris falls to earth everyday, is Earth getting heavier?

In turn, would that increase our gravitational pull?
135 views

If two pieces of the same type of metal touch in outer space, they will bond together permanently? [closed]

Is this true? And if so, why? http://www.snapple.com/real-facts/cap-view/1003
69 views

Calculate Dec and RA of a star from Euler angles and GPS data

I have 9DOF sensor (accelerometer, gyroscope, and magnetometer) that gives orientation via Euler angles (yaw, pitch, roll). Along with GPS data (latitude, longitude, elevation, time) this is passed to ...
43 views

Conflicting information about the star Delta Pavonis?

Delta Pavonis has about the same mass as the sun so I would think that the evolutionary path would be about the same (the mass is given as O.991 M(Sun)/ not sure how we get this so accurately). It has ...
43 views

EPIC 201367065?

I was extremely stoked when I read an article in January of this year that the Kepler2 mission found three Earth-sized objects (one possibly in the habitable zone) transiting a star only 150LY away. I ...
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How did pre-Earth's mass and orbit change at the Moon formation event?

The popular, but still disputable, Moon formation theory is that a pre-Earth was hit by a Mars sized planet. The mass ratio of Earth:Mars:Moon is roughly 100:10:1. Does this mean that pre-Earth was ...
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What is the detector size of LANDSAT 8's detector array?

According to the suggested tags, this must be the right forum: I found that for each band of Landsat 8 over 7000 detectors are on the array. Does anyone know how big each of the sensors is?
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Is Polar Lights observation possible at the latitude of 56° N?

Back in 2002, me and my friends observed a green glow in the sky at night in the form of giant slow moving spurts of flame, looking more dense near the horizon and more blurred at height. It was ...
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Correlation of planet sizes with star sizes?

I did my own amateur Kepler data analysis in May of this year of data from Kepler.nasa.gov/Mission/ discoveries. I found a strong correlation between star size and planet size (percentages). 37 of the ...
29 views

Classification of Planets?

The data from Kepler has taught us that there is a much larger number of "Neptune-class" planets out there than we previously thought. I wonder, however, if this "dominance" of Neptunes is because of ...
26 views

Reason for a correlation between Hot Jupiters and higher metallicity in Kepler data

This question is from an amateur data analysis I did in May of data from Kepler.nasa.gov/Mission/discoveries. There were 80 Jupiter size planets in the Kepler "confirmed" planet table on this website ...
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Unbelievably high masses/ densities in nasa website data

In May, I did my own amateur analysis of Kepler data that was supplied on Kepler.nasa.gov/Mission/discoveries. This was a table of all confirmed "Kepler planets" to date (April 1, 2015). This table ...
66 views

The largest discrepancy in the history of science

I watched a cosmology lecture given by Leonard Susskind that convinced me to put my money on dark energy being a pressure caused by energy that is evenly distributed throughout the "vacuum" of space. ...
42 views

Could we estimate the age of the universe based on the planar property of the Solar System?

The Big Bang scattered planets and stars everywhere in three dimensions. But after billion years of moving and interacting with each others through gravity, planets moved on the same plane. Given ...
39 views

Planets within 10 parsecs

I have been researching what we know, so far, about planetary systems within 10 parsecs. It is easy to find out what has been found, but much harder to find out what has been eliminated (for instance: ...
120 views

Is it just coincidence that the Moon follows the ecliptic?

Or has it been gravitationally steered that way because of how it was formed?
56 views

Can Pluto and Neptune collide anytime in future? [duplicate]

We know that, the orbit of pluto ambiguously cuts the orbit of Neptune. I want to know, whether the revolving speed of Neptune is equal to the revolving speed of pluto. If not, is there a possibility ...
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Online wide-field star cameras?

Where can I find a large list of online star cameras with wide fields of view? http://www.itelescope.net/all-sky-cameras is one example, but the images are fairly low resolution and there aren't many ...
81 views

infinite Universe [duplicate]

I was watching a documentary and they said that Cosmologists have determined that the Universe is infinite. I find this to contradict the expansion theory. If the Universe had a starting point then ...
30 views

How to get error out of astropy constants

How do I get the error value out of an astropy.constants quantity? ...
116 views

Perceiving movement of stars

Are there any stars visible to the naked eye whose position, over a normal human lifetime, can be seen to have changed (relative to other stars in the vicinity)?
109 views

What does the orbit of multiple star systems look like?

How can I find simulations of trinary, 4-nary.. etc. star systems? What do they look like? For example the Alpha Centauri system has 3 stars and possible planets. What does that orbit look like? I ...
19 views

accretion discs in h/lmxbs

High mass x-ray binaries necessarily accrete via wind, no disc accretion? What makes the difference between a hmxb and a lmxb? In what kind of circumstances does an accretion disc form? How does it ...
67 views

The colour of saturn as it appears to the naked eye

I have started to watch the skies in order to learn stars, constellations planets etc. The few references I checked state that Saturn presents itself to the naked eye as a pale yellow tiny little ...
82 views

How to interpret this old degree notation?

I'm trying to follow the calculations in this paper on page 5 (see image below). The paper is describing traditional methods of calculation for a luni-solar calendar. The math is not hard, but I ...
165 views

Venus presents same face toward Earth at closest approach. What do you make of that?

Is reference 6 in this Wikipedia article "dubious" and this passage in need of excising or clarifying? Venus's 583.92-day interval between successive close approaches to Earth is equal to 5.001444 ...
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Are micrometeorites cosmic dust?

Are micrometeorites just dust grains at high relative speed, or is there some difference between them and cosmic or interstellar or solar nebula dust? Dust as in the clouds which obscure parts of the ...
53 views

Do bigger telescopes equal better results?

There are many large reflecting/optical telescopes around the world, just to name a few: the Very Large Telescope, Large Zenith Telescope, and European Extremely Large Telescope. My question is does ...
54 views

Travelling at light speed(inside water) [closed]

It is a said fact that 299792458 m/s is the speed limit,nothing can go faster than this speed, or it will take an infinite amount of energy for propulsion.What we perforce in vacuum is one thing.Can ...
97 views

What do we know about the characteristics of stellar objects, 13,3 billion light years away from us?

To receive light from objects like MACS0647-JD, I suppose, it has to has extraordinary dimensions and intensity of electromagnetic radiation. What are the mass, the dimensions and other ...
66 views

If I were to point into the sky, how many galaxies would be in this line?

If I point in the sky and draw a line from the tip of my finger to the end of the universe, how many galaxies would this line cross? I had a discussion with my dad and he said due to the universe ...
179 views

Why Earth does not have rings?

Why does the Earth not have rings like Saturn or Uranus?
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Amount of EM radiation (and particles) Earth “receives” from other planets in our solar system?

Can it be (or has it been already?) measured how much and what kind of EM radiation (apart from visible light)/particles Earth "receives" from a specific planet in our solar system? Can other planets ...
80 views

Supermoon Lunar Eclipse?

I recently read this article: http://www.cbsnews.com/news/supermoon-lunar-eclipse-coming-this-month/ I'm having some trouble understanding how a "supermoon" lunar eclipse is possible. Judging from ...
97 views

Does the universe expand at the same rate everywhere in the universe?

Specifically, I am wondering if some areas of the universe expand faster than other areas and whether the faster expanding areas diffuse the expansion through the slower expanding areas or does the ...
98 views

Determining North-South Line Via Watch Method: Theory & Reason

I recently read that if you're in the northern hemisphere and have an analog watch, then you can point the hour hand at the sun and know that a south line lies between (bisection) the hour hand and ...
71 views

When a neutron star accretes matter, will its mass increase?

When a nova gets matter, the outcome is that it may lose more matter because of eruptions. Only some kind of nova's masses can increase stably. A white dwarf may become a supernova after it exceeds ...
127 views

What are iron stars?

I have a question about iron stars. I was fascinated about the theory about the inability of protons to decay, and it led me to a point where I read something about some special kind of star called an ...
47 views

Spicules vs Prominences/filaments

What is the difference between spicules and prominences/filaments. I know that they are both in the chromosphere, and I know the difference between provinces and filaments (depends on the view), but ...
156 views

Astrophotography - Unable to achieve focus with current setup

I am new to astrophotography and am looking for guidance. I have the following equipment: Orion StarBlast 9814 4.5" Altazimuth Reflector Tabletop telescope 1.25in Telescope Adapter Extension Tube T ...
69 views

Roll, Pitch and Yaw of Orbital Planes

I have been reading about celestial mechanics and particularly about planetary orbits. I understand that a planet's orbit can be tilted (pitched) with respect to the Earth's ecliptic and that it might ...
47 views

Finding the suns position in the sky anywhere at any time

What am I looking for? from any point Latitude, Longitude and date D I want to know where the sun is in the sky at any given time anywhere on our planet. I even don't know what the outcome will be ...