# All Questions

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48 views

### Are red dwarfs (M dwarfs) known to be strong infrared sources?

If so, why? Are they known to be surrounded by large amounts of dust? Do they typically flare?
93 views

### Relativistic Mercury orbit around the Sun

My question is the following,would the scalar of precession of Mercury orbit be the same if Mercury orbited Sun in the oposit direction?
75 views

### Do gravitationally bound (e.g. orbiting) objects really resist the expansion of space?

Thinking about the expansion of space, it is commonly explained that gravitationally bound objects (like galaxies and galaxy clusters) will not be affected by the expansion of space (dark energy). I ...
175 views

### Will intergalactic travel be impossible in roughly 15 billion years?

Even if we (or aliens somewhere in the universe living at that time) somehow invent something that can go just short of the speed of light, will intergalactic travel still be impossible in roughly 15 ...
95 views

### Does light from the sun reach the surface of Venus

I am aware we have images from the surface of Venus from the Venera missions but I am not sure if those images are taken using the visible spectrum the human eye can see. This is why I was wondering ...
26 views

### How to interpret error of absolute magnitude of a star given data from wikipedia?

This Wikipedia page contains information about the star Spica in the rightmost table. A small snapshot of this table is below. In this table, the absolute magnitude is given as ...
57 views

In the CASJOBS Server, I created the following query for galaxies(DR12) ...
93 views

### Slow moving star like objects in the night sky

So yesterday at about 2am I was watching the sky when I saw a small star like object moving very slowly across the sky. My initial thought was that it was a satellite due to the fact it was moving so ...
83 views

### Black hole's gravity

Is gravity relative to volume, or size of an object? Since a black hole is a massive star that collapses on its weight, how comes the same sun's mass, when it becomes a black hole, provides gravity ...
168 views

### View of other planets from the Earth

There appears to be varying positions/spots of view of other planets from Earth, if I'm not wrong. Now, given that all planets are on the same plane, why do their positions change on the night sky for ...
128 views

### Snowball Earth brightness

The Earth likely froze over almost completely about 700 million years ago. This increased its albedo significantly, and I wonder if that would have a considerable effect on its apparent magnitude from ...
89 views

### Energy to expand

I do have a small question, which may seem a bit stupid but we are all here to learn. Anyways my question is: Is the universe expanding using the energy it had from the Big Bang? if so what would ...
80 views

### What decides the shape of a galaxy?

As I know, most galaxies are spiral, some elliptical, and a rare type is ring-shaped. What causes a galaxy to become a specific shape (i.e. ring vs spiral)?
138 views

### If the earth stopped spinning what would happen to the moon

A question was posed at work today, "if the earth stopped spinning what would happen to the moon"? Ignoring any effects on the Earth, what actually happens to the Moon? Does it continue to orbit the ...
9k views

### Does this smartphone photo show Mars just below the Sun?

I live in Essex, England (51.7678° N, 0.0878° E). On 25 July 2019 (hottest day ever in the UK, btw), 06:43 BST, I took this smartphone photo of the Sun. Is that white dot just below and left of the ...
90 views

### How thick was Earth's primordial atmosphere?

Earth's first atmosphere was made of hydrogen and helium accumulated before fusion started in the Sun. As soon as this happened it was stripped away by the Sun. How many atm of hydrogen and helium had ...
58 views

### What is the significance of minus sign in the expression of apparent magnitude?

The apparent magnitude of a distant object in the sky is measured as m=(-)2.5 log (I/I0) Where I is the intensity of the object whose apparent magnitude is to be measured and I0 is the reference ...
41 views

### Orbital Resonance

First, let me verify that this statement is correct: Planets will tend to migrate toward stable orbital resonances with other planets around the host star. There are unstable resonances, also, where ...
64 views

### When and where are we exposed to most cosmic radiation?

I understand the mechanical dynamics of being faced away from the Sun at night, having a lower altitude, not being in the weak points at the poles in the atmosphere, being in a valley and others ...
35 views

### Geo Helio and RA

please assist me , i'm using Zet 9 and there is Geo longitude , Helio longitude and RA , what is the difference between them. example : ...
3k views

### On the consistency of different well-polished astronomy software

I have purchased a custom wedding band from a seller that claims the ring will show the constellations visible at the horizon on a specific date at a certain date and time. However, I have fired up ...
71 views

### Meade ETX-90 with computerized mount slews too far during auto-alignment

I've been trying to get my new ETX-90 to properly align itself these past few nights, but without success. I've mostly been using the Easy align functionality, which has been choosing Arcturus and ...
118 views

### What weather is present in Jupiter's great red spot?

What weather is present in Jupiter's great red spot? Is it raining? Is it snowing? There is definitely a hurricane a blowing :-). I know it is very cold, extremely high winds, has clouds of an ...
85 views

### Lorentz transformation for stars

If a star that has regular pulses(standard candle) is flying away from us at relativistic velocity(very distant), would that pulses look like very sluggish compared to a non-relativistic velocity(...
30 views

### What Would Be the Maximum and Minimum Luminosities of a G-Type Main-Sequence Star?

So I just found the Habitable Zones in Multiple Star Systems interactive website, where I can create a habitable zone out of multiple stars using the temperature, luminosity, mass and position of each ...
108 views

### Tilting cycle vs orbital cycle of earth

Common sense tells us a year is conveniently divided exactly into four seasons. I'm wondering whether that means the earth's tilting cycle is equal to its orbital cycle. If so, there must be a reason. ...
19 views

### Warming Mars by increasing dust infall? [migrated]

From this article: https://www.universetoday.com/142558/martian-clouds-might-start-with-meteor-trails-through-the-atmosphere/ It suggests that increasing high-level cirrus cloud would significantly ...
145 views

### How can we see stars if they are hundred years of light far from the Earth?

So the right question is, is the light years counted from that second when you look up to the sky? If that so, how can we see the stars from the telescope (which I think it starts when you put your ...
148 views

### Why are there no photos of exoplanets?

There are a lot of photos of diffrent astronomial objects such as galaxies, nebulae and stars of which some are very far away. However there are no real photos of exoplanets (by “real photos” I mean ...
124 views

### How to listen to our world from 10,000 light years away?

If you were 10,000 light years away from all radio stations and digital broadcasts from our world, what equipment would be necessary to detect and capture some information like a voice or a photo? If ...
42 views

### Difference between first (focal length (fl.) 500 mm, ocular (o.) 10 mm) and second telescope (fl. 1000 mm, o. 20 mm)? (both 50 x)

Magnification is defined as $f_{objectiv}/f_{ocular}$. If I had the first telescope with the focal length of 500 mm, ocular 10 mm and second telescope with the focal length of 1000 mm, ocular 20 mm, ...
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### Can we observe changes in the CMB (surface of last scattering) over time? [duplicate]

It is hard to determine the age of the Sun, because it won't change much over 100 million years or so. But what about the cosmic microwave background radiation, that is being mapped with ever better ...
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### I am looking for the SKYMAP Api (To create nightsky/star maps)

The ones used by underluckystars.com and thenightsky.com I have found several but I am having difficulty finding a working updated version, has anyone come across this API, or know where I can find ...
31 views

### How to do logarithmic wavelength binning (in Python) in order to find redshift?

In Tonry and Davis (1979)(http://adsabs.harvard.edu/abs/1979AJ.....84.1511T), they formulated a cross-correlation method for extracting velocity redshifts. They bin the linear spectra into logarithmic ...
21 views

### How to correct a spectrum for galactic absorption and for redshift?

I downloaded spectrum from SDSS data base, it is AGNs data, I want to use software to subtract FeII and that software requires input spectrum to be corrected spectrum for both galactic absorption and ...
683 views

### Are there galaxies with 2 or more super massive black holes orbiting each other?

We now know that most stellar systems have 2 or more stars orbiting each other. Do we know of any galaxies which have 2 or more super massive black holes orbiting each other? Is it possible?
9k views

### If the Moon were impacted by a suitably sized meteor, how long would it take to impact the Earth?

An answer to the question of How well would the Moon protect the Earth from a Meteor? mentions as a possibility that the Moon could get knocked into the Earth. What is the smallest change to the ...
107 views

### What would happen to black holes during the Big Rip?

If the universe expands fast enough to rip atoms apart, what will happen to black holes? Would they rip apart too? What would that be like? Would they expand along with the universe's expansion, or ...
12 views

### What are estimated magnetic properties of liquid metallic hydrogen? [migrated]

I understand that liquid metallic hydrogen isn't easy to produce, or keep it stable on Earth, but can be liquid metallic hydrogen magnetised? Does it have metallic properties at all?
32 views

### In which countries are there organised Messier Marathons?

Just out of curiosity... In which countries have there been or are current, organised Messier Marathons? Thank you for all answers and effort for this!
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### Is there any free stacking program that stack images which are not aligned?

I liked to photo deep-sky-objects and planets with my camera Canon sx130. But I have never stacked images because they were too much apart. I was looking for some free astronomy stacking program for ...
88 views

### 2019OK energy at impact

The asteroid 2019 OK recently passed at 77.000km of the Earth, with an estimated size of 50-130m. But if this asteroid had crashed onto the Earth, what would have been its kinetic energy on impact? ...
3k views

### How well would the Moon protect the Earth from an Asteroid?

Would the Earth fare better if the Moon blocked the meteor, comet, rogue planet, or otherwise rather than a direct impact? At what point would the Moon's debris would be an extinction event? The ...
55 views

### First spectroscopic detection of Uranus' rotation?

As an undergraduate exercise quite a while ago, we placed the equator of Jupiter's disk across the slit of a high resolution grating spectrometer and then measured the tilt of the resulting line in ...
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### How does the orbit of a 2-body system evolve as it orbits a more massive 3rd body?

I have been reading up on how multiplicity of star systems decline with star mass, which implies a relatively common occurrence of binary star systems orbiting more massive stars. I would imagine this ...
36 views

### How do I calculate Allan Variance (maybe for pulsars)?

I am studying pulsar timing this summer and have come across many Allan Deviation plots that include several popular clocks alongside pulsar measurements, like this one by N. Ashby and D.A. Howe: I ...
133 views

### What kills us in the event of two galaxies combining?

I find the joining of galaxies interesting as the two eventually become ONE. On series I saw on a discovery channel stated we die. Everyone dies. What is it that causes us to die when the galaxies ...
161 views

### Can a black hole formation be stopped or interrupted

My question is a hypothetical: if I were to create a black hole the size of a family house, in New York, is there any way that it can be stopped, or interrupted? If a black hole of this size is formed,...