# All Questions

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59 views

### Practicality of Dobsonian telescopes

I've been using binocular for more than a decade for visual observation. I'm thinking of upgrading to a telescope. The Dob caught my attention due to its simplicity in setup and also cost ...
52 views

### Strange trail left by shooting star [duplicate]

I saw something really odd last night that I cannot understand. Last night I got up around 3am to catch a glimpse of the upcoming Perseids meteor shower, now I know it's not peaking until next week ...
50 views

### Can an event horizon form with the observer already inside?

I am on a planet orbting a star around the center of the milky way (assume no supermassive blackhole there). By some mechanism, mass starting from the outer part of the galaxy gets pushed inward until ...
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### Approximate formula to find velocity from cosmological redshift

From IOAA 2013 (Greece) Theory question no. 15, they stated that the approximate formula to find velocity from cosmological redshift is $$v = c*log_e (1+z)$$ and that it is often used by cosmologists. ...
46 views

### Angular diameter result confirmation

Not being a math-minded person at all, however basic it might appear to be to all of you in this particular question, I would like to get the following calculation confirmed. I'm trying to calculate ...
65 views

### How does gas in accretion disks of supermassive black holes create orbital torques on smaller black holes within the disks causing them to migrate?

This answer to What enhances the capture and merge rates of pairs of small black holes orbiting around supermassive black holes? links to Migration Traps in Disks Around Supermassive Black Holes which ...
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### Would a satellite that has a retrograde orbit and a shorter orbtial period than its planet's rotational period be tidally accelerated or decelerated?

There are 4 configurations to consider. A satellite orbiting a planet that: Has a prograde orbit and larger orbital period than its planet's rotational period (example: The Moon) Has a prograde ...
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### Is there still a possibility that Makemake is not ellipsoidal but asteroid-shaped?

In 2008, Makemake and Haumea have been named under the expectation that they would prove to be dwarf planets. Well, did they prove to be ones? Haumea obviously did since we know its shape which is a ...
533 views

### Where did Mars' water go?

Many sources indicate that there is ice water on Mars today, but it is mainly traces, here and there, but not that much. However, solid hypothesis state that there were oceans on Mars, see Wikipedia'...
901 views

### Jupiter with a mobile phone and Celestron Astro FI 102mm Maksutov

My name is John, I am new here and now that I am retired I decided to get myself my first ever telescope, why I never got one before I have no idea...probably too busy. So I thought I would try and ...
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### Why wouldn't massive torrents freeze on Mars?

I am currently reading the Cambridge Guide to the Solar System. In chapter 8, section 8.7, they explain that massive torrents of water created outflow channels on the surface of Mars in the past. The ...
48 views

### How Can I interpret this particular light curve without reading data on the side

There is only one dip in flux recorded. How can I interpret this particular light curve and find planetary radius https://exo.mast.stsci.edu/exomast_planet.html?planet=55Cnce
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### Strip Brightness in a Spherical System

My question concerns the following problem, published in Galactic Dynamics by Binney and Tremaine and based on a work by Schwarzschild. Specifically, I am having difficulties in deriving the given ...
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### How long do hot X-ray sources last?

Some X-ray sources in nebulae are caused by hot materials in the millions of degrees that formed in supernovae. What's the cooling rate of this stuff? How long does it stay this hot? If we would take ...
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### How fast is Neptune getting brighter? When was was this first noticed and reported?

This answer to Compute Planet's Apparent Visual Magnitude reports the new work on planetary magnitudes, and contains an intriguing blurb about Neptune: Neptune keeps getting brighter. No one knows ...
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### Do meteorites streak across the sky in the same direction?

Once while camping with my family as a child we all watched a meteor shower in the summer (in the month of August). All the meteorites streaked across the sky in the same direction. Obviously, this ...
3k views

### Have I nearly found the event horizon of a black hole?

The calculator on the website https://planetcalc.com/1758/ cites Wikipedia's Gravitational acceleration and implements: $$g = G \frac{M}{(R + h)^2}$$ For a black hole with mass $M$ equal to 5 solar ...
387 views

### Is there permanent dry ice on Mars? [duplicate]

Are there any places featuring permanent dry ice (carbon dioxide ice) on Mars? Is there dry ice at the poles?
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### Kardashev scale [closed]

Why is becoming a type 3 from a type 2 civilization the hardest? I have watched many videos on the topic and still can't figure out why? Also is there a difference in technology between a type 4 and a ...
205 views

### What are the Mathematical Algorithms/Formulas behind hindu Sunrise and Sunset Calculations?

There are differences between Astronomical Sunrise/Sunset calculation and Hindu calendar Sunrise/Sunset calculations. The astronomical algorithms to calculate the sunrise/sunset can be found over the ...