# All Questions

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### Who first named the planets Mercury, Venus, Mars, Jupiter, and Saturn?

Who first named the planets Mercury, Venus, Mars, Jupiter, and Saturn? Agnes Clerke's Catholic Encyclopedia article "Astronomy in the Bible" § Planets claims that "Venus and Saturn are the only ...
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### Simulation and its necessity in astronomical research

I was wondering if mainly everything in Astronomical and Astrophysical was dependent on Simulations then what are the educational requirements are necessary to qualify as the Simulation Expert. What ...
27 views

### If you put all planets between earth and moon what would happen?

It's often discussed that you can fit all the planets in the space between the Earth and the Moon. But if they actually did teleport there instantly what would happen next? Assuming their initial ...
45 views

### Can there be a three-moon system where only two are visible most of the time?

I am trying to build a moon system for a sci-fi work in collaboration with my boyfriend. He's the main writer and wants there to be three moons circling the planet in a way that most of the time, only ...
25 views

### Nebula and its Colours [duplicate]

A Nebula boasts of Too Bright Awesome Colors that includes red, blue, green, orange, white, etc? They're result of excitation of electrons. Is there a clear explanation as in which Color is ...
27 views

### Nebula and its colors

A Nebula has bright awesome colors that include red, blue, green, orange, white, etc? They're result of excitation of electrons. Is there a clear explanation as to which color is attributed to an ...
32 views

### A basic question about light curves

I'm new here, so if I've done anything wrong, please let me know. I've been taking a look at some photometry data collected from TESS, and I encountered this light curve: (please ignore the blue and ...
37 views

### How many galaxies have had their distance determined using SNIa?

Supernovae of type Ia can be used as standard candles to determine extra-galactic distances. But these event only occur (roughly) once every 200 years in any given galaxy and rapidly fade away. So to ...
24 views

### What are these data in light curve generator

I'm generating light curves for some variable stars on the AAVSO website (see https://www.aavso.org/lcg ) . I can choose what type of data must be plotted. Can you explain what they are? Thank you in ...
36 views

### How to compute Ascension / Descension cycle of the Moon

I am struggling to find out an information about how to determine ascending/descending cycle of the Moon. I can find from this source and a bunch of others, that Moon begins to descend when reaches ...
4k views

### How often do supernovae occur?

Type Ia supernova are used as standard candles. But they also are transient events. This means that to determine the distance of a galaxy using supernovae, you have to wait for one to occur. How often ...
65 views

### “Juxtapositions” of moon,stars and planets in the sky,

What are "Juxtapositions" of the Moon, stars and planets called? When the Moon, stars and planets take exactly the same position after few or many years, how to describe the positions and what is ...
121 views

### Why do Newtonian physics give the right radius for a black hole?

When computing the distance at which the escape velocity is equal to the speed of light, the result is equal to the Schwarzschild radius. Is this just a coincidence, or is there a physical reason why ...
126 views

### Can a material other than glass be used for making telescope mirrors?

Although I do know of a few instances where professional or observatory mirrors have been made by alternate materials, it was primarily for targeting specific nuances, like weight reduction and low ...
85 views

### What are the chances that the universe could be moving towards an Extra SuperMassive BlackHole [closed]

As we know it the Universe is moving towards a certain direction and we all are drifting towards it slowly but surely. So what are the chances that in the midst of all the controversies(Just To Be In ...
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### Consequences of strong wind on an alien Planet on the possibility of life

I was surprised to learn recently that Neptune has winds of 1500 miles an hour. My question is whether life could ever evolve on such a Planet that has such powerful winds? Not necessarily on ...
1k views

### Why does the sensitivity to GWs drops off inversely proportional to the distance?

This answer makes me wonder why the sensitivity to gravitational waves decreases proportionally to the distance. Since gravitational waves extend in all directions, my (uneducated) guess would be ...
93 views

### What methods can high school students use to measure the radius of the earth?

I suppose they could split into 2 groups and use the shadow method from different latitudes. Maybe they could also use the stars on the horizon at two different latitudes. Is measuring a ship below ...
95 views

### We should be seeing more than 59% of the Moon

It is said that we see about 59% part of the Moon due to libration. However we must be seeing more than that. My logic is as below. Since the Moon's orbit is inclined to the plane of Sun-Earth by 5 1/...
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### When exactly star Sirius shines into the queen's chamber of Great Pyramid?

I read that Great Pyramid was built to resonate with Sirius by aligning an airshaft that connected to queen's chamber. That is, the light of Sirius going through the shaft would be able to shine into ...
88 views

### How do astrophysicists handle the topic 'boundaries'?

The naive perception, at least mine, is that in astrophysics the objects of investigation evolve in an infinitely large environment. Since the scenery is so much larger than the events unfolding in it,...
136 views

### When can the Sun, Moon and the five naked-eye planets all be in Leo?

What are the possible dates for the seven (classical/mediaeval) planets (Sun, Moon, Mars, Mercury, Jupiter, Saturn, Venus) all being in Leo? I’m not sure how to figure this out on my own. I’m ...
453 views

### Are Tharsis Montes and Hellas Basin a result of the same event?

Looking at Mars map: the highest, biggest mountains and their associated highlands are essentially antipodes of the deepest, huge basin. Roughly 180 degrees away, similar latitude except opposite ...
34 views

### Temperature variation with distance [closed]

So here is the question I'm troubling with: We estimate that the temperature varies approximatively with that relation: a) Determine the point (x0, y0) where the temperature is maximum? b) If the ...
81 views

### Gravitational field for oblate spheroid?

Consider a planet, described as an oblate spheroid. Assume that the spheroid is uniformly dense but not a point source. Outside of the object, do all vectors in the gravity field point through a ...
24 views

### Large-Scale instabilities in Disk Galaxies

Multiple sources in literature state that a disk galaxy, without considering the presence of Dark Matter is subject to large-scale instabilities. What is the reason behind the claim? I am looking for ...
146 views

### Why we can't see our Sun as it was a few years ago?

Our Sun is orbiting the center of the Milky Way galaxy. So many years ago, it was at a different location from where it is now. In addition, we are observing stars and exoplanets as they were many ...
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### Why have brown dwarf classes been dubbed L, T and Y?

The classes used to categorize stars (O, B, A, F, G, K, M) are in a bizarre order for historical reasons. Stars were labeled based on the spectral lines that were visible, then the categories were put ...
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### What is the exact time of sun stay in each zodiac every year on sidereal year duration?

I tried to reverse engineer from astro-chart times at which sun stays in a zodiac. Here is the list. ...
16 views

### How the depth[Mpc] is obtained from the redshift

I read this paper. In this paper, they show the three-dimensional distribution of the [OII] emitters. It is mentioned that The depth in z-axis is converted from the redshift, which is estimated from ...
71 views

### Gravitational Slingshot

If a spacecraft slingshots around a planet P (with escape velocity V) at an angle $\theta$, I understand that the resulting velocity is { v }_{ 2 }=({ v }_{ 1 }+2u)\sqrt { 1-\frac { 4u{ v }_{ 1 }(1-...
38 views

### Co-ordinate System of Celestial bodies in space [closed]

My question is How can One Understand what is Azimuthal, Right Ascension, Declination,etc? I had tried understanding but failed.
191 views

### Is there a limit to the distance of detectable gravitational wave events?

This is somewhat a follow up question to this one. This article indicates that the binaries detected have a distance between 320 and 2840 Mpc. With the current technology, is there a limit to the ...
25 views

### How are Y-dwarf spectral subtypes defined?

It is often stated that the spectral subtype indicates the relative position between spectral types, e.g. G5 being halfway from the start of spectral type G to the beginning of spectral type F. Given ...
117 views

### How would the sky look if Earth orbited a red giant at a safe distance?

Let's say that instead of the sun, we have a red giant, but are orbiting it at a safe distance, within the goldilocks zone. Would the sky actually look more red? Or would it be closer to white/...
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### Why is Ganymede's aurora only visible in ultraviolet while Earth's is bright green and red?

GANYMEDE AURORAE NASA's Hubble Space Telescope observed a pair of auroral belts encircling the Jovian moon Ganymede. The belts were observed in ultraviolet light by the Space Telescope Imaging ...
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### How far away are the events that caused the gravitational waves that have been detected?

A certain number of gravitational wave events have been detected. Is it possible to know how far away the mergers that caused those gravitational wave events are?
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### Book recommendation for astronomy [closed]

I want to buy a book that deals with the mathematics of astronomy and still is understood by all. I am a sixteen year old student
51 views

### Saw 8 stars moving in same direction one by one [duplicate]

I saw 8 stars moving in the same direction one by one and then at the same point they faded or you can say disappear. The speed was not too fast but not too slow either. I am more curious because ...
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### How is the Dating of Samples of Cosmic Objects Performed, Including Pre-Solar Dust?

In the new Space.com article 7 billion-year-old stardust is oldest material found on Earth I had read about some pre-solar grains dating back to 7 billion years. What techniques are used in ...
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### Will the nebula of Betelgeuse be visible to the naked eye? How bright, how large, how soon, for how long?

When Betelgeuse goes core collapse supernova it will leave a supernova remnant. Will it become visible to the naked eye? If so, in what time frame will it be visible. Will it be star like from the ...
94 views

### Several stars in line [duplicate]

I can see several stars in the sky they can make a line come from the West south and going to East north direction at the time between 6.50 to 7.00 pm Indian time on date 13.1.20. What might these ...
55 views

### Saint-Exupery describes visit to plateau where he easily finds several meteorites. Is this realistic?

In "Wind, Sand and Stars" Antoine de Saint-Exupéry describes a visit to a plateau where it is extremely easy to discern meteorites from stones, since there are no stones. I picked up one and then a ...
24 views

### The sun networks [duplicate]

For my research about the sun activity I need to edit pictures of the sun. I want the pictures to show three stages the quiet, enhanced and active/plage network. I couldn't find any information in the ...
55 views

### What if the Sun turned into a red giant tomorrow? [closed]

Let's say that, hypothetically, our sun uses up all of it's hydrogen tonight, and tomorrow morning is the first day of its red giant phase. How long would it take for the star to turn red? How long ...
38 views

### Stars are moving in row What could it be? [duplicate]

Star like light moving in the sky, what could it be? The same thing I saw today  I saw number of stars are moving in straight line. And some are in various directions. It was about the same size of ...
29 views

### Stars moving in a row [duplicate]

Today I saw with my wife and neighbours stars are moving in a row almost 10 to 12, and after a few minutes 2-3 stars moving in different direction in a row. What could they have been?
29 views

### Difference between quiet, enhanced and active networks

For my research about the sun activity I need to process pictures of the sun. I want the pictures to show 3 stages the quiet, enhanced and active network. I couldn't find any information in the ...