# All Questions

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6 views

### line of lights across sky

This morning at 6AM I saw a line of lights coming out of Orion, moving across the North star then Big Dipper and disappearing into the early dawn. I saw at least 30, no idea how many came before I ...
12 views

### What do you call it when a satellite goes once around its planet?

When a planet or a satellite turns around itself, its called a rotation. When a planet goes once around the Sun, it's called a revolution. What do you call it when a satellite goes once around its ...
26 views

### What makes the planets to be symmetric

I have seen, in my text books, and on nasa sites, the all the planets are symmetrical. And universe also love symmetry. What cause this symmetry, why the symmetry is important. As we know that ...
11 views

### Calculating object velocity at perihelion

I would like to calculate the velocity of an asteroid orbiting around a star (Sun) at the perihelion of its orbit. I know the excentricity of the ellipse and its semimajor axis. I have found that the ...
29 views

### Binocular highlights from Tasmania next few weeks?

My friends are visiting southern Australia and Tasmania for the next few weeks. I am lobbying them to bring my Nikon 8x42 binoculars so they can appreciate the Milky Way and possibly see a few other ...
9 views

### How can I download all of this JPL MRO imaging data at once?

There are several files. I think that they all needs to downloaded to have the complete dataset. Is there a particularly good way to download them all in one shot? https://pds-imaging.jpl.nasa.gov/...
26 views

### How much of a molecular could can end up as “starstuff”?

Stars form within molecular clouds. These clouds can be up to 6 millions solar masses. When the cloud collapses into stars, is it possible to know a rough figure for how much of this material actually ...
23 views

### Lifespan of B-type subdwarfs

According to the Extrasolar Planets Encyclopedia, the B-subdwarf Kepler-70 lost its helium envelope and became a blue-white subdwarf roughly 18.4 million years ago. (sources: archived encyclopedia ...
1k views

### Which stars did the Sun form with?

The Sun formed 4.5 billion years ago, in a molecular cloud. I assume that there were other stars in the vicinity (as is common in molecular clouds). Which stars are they? Where are they now? Are they ...
169 views

### How do I get started in astronomy data analysis?

I am learning some machine learning (I have previous background in statistics) on my own, and I am interested in getting some hands-on practice by doing some ML analysis in R and Python. Given how ...
24 views

### What makes some meteor showers continue for days, while the “Unicorn shower” can be shorter than one hour?

The Washington Post's One hundred meteors in 15 minutes? ‘Short-lived outburst’ of shooting stars forecast for Thursday night. says: A “short-lived outburst” is forecast for Thursday evening around ...
34 views

### The colour of blue dwarf stars

The paper "M dwarfs: planet formation and long term evolution" describes blue dwarf stars, a hypothetical next-stage in the lifespan of red dwarf stars within a certain mass range, after which they ...
145 views

### Based off of the study that found the universe has a positive curvature, how big would the whole universe be?

This study found that the universe has a positive curvature https://www.nature.com/articles/s41550-019-0906-9. I didn't really want to buy it and see if it says how big the universe might be. I know ...
2k views

### What are the minimum element requirements for a star?

What elements would be essential for a star to exist? From what I understand our sun is made of mostly hydrogen and helium and most stars have small amounts of heavier elements like carbon, nitrogen,...
34 views

### Ecliptic line plot in a map

Is there any url that can give me data of ecliptic line that i can plot in a map. i.e i need earth's latitude and earth's longitude of ecliptic line for a specific time and date. Right now i only ...
9k views

### Is Earth's Surface “In orbit”?

I'm having trouble understanding relative angular/tangential speeds at increasing altitudes above Earth's surface. In particular, I find this comparison of tangential velocities on Wikipedia very ...
95 views

### What is the LSST's plan to address frequent satellite trails in data?

update: From Nature.com News article: SpaceX launch highlights threat to astronomy from ‘megaconstellations’: But an upcoming, cutting-edge telescope could be in bigger trouble. The US Large ...
13 views

### Is the turn-off point of the main sequence the same as the terminal-age main sequence?

The turn-off (TO) point is one tipping point on the Hertzsprung-Russell diagram (HRD) where low-mass stars start to evolve from the main sequence (MS) toward lower temperatures. If I understand it ...
1k 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?
501 views

### Ross 128 (What does the number mean?)

I see that there are a number of stars that have a number at the end of them. Ross 128 is an example. What does this number mean?
32 views

### Is it possible to build a ground-based telescope that can directly image Earth-like planets orbiting in the habitable zone of sunlike stars?

In the following discussion I will refer to Earth-like exoplanets planets orbiting in the habitable zone of sunlike stars simply as “Earth-like exoplanets." NASA is currently developing or ...
17 views

### What was the distribution of the elements and compounds in the protosolar nebula?

I've been reading some articles on planetary formation in which it is mentioned that the composition of the protoplanetary disk changes depending on the distance to the protostar. At great distances ...
34 views

### When is the best time to observe M81 from the Northern Hemisphere?

I have read that the best time to view M81 is during the spring. Considering its RA is ~10h and Dec. is +69°, wouldn't February 21st be the best time to view it since this is about when it transits my ...
424 views

### If a comet strikes a glacier, does it make a print on the land below?

The Younger Dryas Impact Theory describes an asteroid impact in Northern America, possibly the eastern part of Hudson Bay, which contributed to the end of the last ice age. If a comet strikes a ...
107 views

### The recent results on Hubble constant measurements

In recent news there is this announcement In the introduction they say: Distance measurement discrepancy: a $4.4σ$ tension on the value of $H_0$ and I understand the discrepancy is with the ...
79 views

### The energy density of DM (to be fluid,state parameter=-2)increases with time. Does it violate the concept of accelerating universe?

We know that dark energy with value of state parameter $\omega<-1$ is called phantom dark energy model. In this model if we assume dark energy to be a fluid with value of state parameter $\omega=-2$...
49 views

### How long for the sun to traverse its diameter at the pole?

As the sun rises once per year at the north/south pole, the time taken to rise (and set) must also take significantly more time to complete to rise (and set). How long does this take at either pole? ...
18 views

### Freefall timescale for a Jeans-unstable hydrogen cloud of mass M

I'm working on a project (personal, not academic) that involves calculating the collapse timescales for protostars which will end up becoming stars of varying given masses. I'm treating the pre-main ...
77 views

### Could different views of the universe simply be different points in time?

I'm not sure if this is the correct stackexchange site for this question. I've been reading this article on Vice Motherboard There’s Growing Evidence That the Universe Is Connected by Giant ...
20 views

### Determining Horizontal Coordinate System data (azimuth, altitude) for geographic locations

I would like to determine, specifically, azimuth and elevation data for any given location on the surface of the earth relative to another location on the surface of the earth (for my purposes, the ...
164 views

### Could a star closely orbit a black hole long enough for the star to have lost 0.5B+ years to time dilation?

I was wondering how stable a close star-black hole system could plausibly be, and thus how much time a star could plausibly miss out on (from an outside observer's perspective) due to being in an ...
228 views

### If a star were travelling at 99% of the speed of light, directly at Earth would we see it?

Stars being flung from black holes in the news made me question if something were heading directly for us at the speed of light, would we even know? Update: Since it's impossible for a star to travel ...
45 views

### What is the least dense exoplanet?

An exoplanet with density 0.31 grams per cubic centimeter has been found. Is this the least dense exoplanet we know of?
53 views

### Black hole collision animation: What are these extrusions?

In this video uploaded by LIGO Lab Caltech, two inspiraling black holes are depicted. The video's description explains what is shown and can be summarized by: The colored surface is the space of ...
117 views

### Are there only a set number of atoms in this universe?

As per the title, are there only a set number of atoms in the universe? Or does the universe make more atoms, and if so, how does it work? I'm a high school student that just had a question during ...
53 views

### How was lunar eclipse proven using the scientific method? [on hold]

I read a few articles about lunar eclipses and while they explain the science behind them, they do not describe who explained it and how it was explained using the scientific method. Some of them ...
11 views

### Creating a 2D matrix from 2 FITS images of unequal dimensions for Radio/FIR correlation

I have two images of NGC 6946: ...
99 views

### How can a star be “thrown out of the Milky Way” by Sagittarius A*?

A recent publication reports that a hypervelocity star on course to leave the galaxy was found, likely accelerated by the black hole at the center of the Milky Way in a process predicted by Jack G. ...
74 views

### Hot Jupiters around heavy stars?

Hot Jupiters are giant planets that are very close to their host star. How many Hot Jupiter exoplanets have been found around stars more massive than our Sun? Has the number of Hot Jupiters ...
95 views

### Electron Degeneracy Pressure

The Z/A term for calculations of degeneracy pressure for white dwarfs is given as 0.5. But I can't find an explanation as to why. For my assignment, I am trying to find the degeneracy pressure for the ...
61 views

### Ecliptic line data

I would like to get the data of ecliptic line with respect to celestial equator for a particular day. Is there any specific URL that can give me this. I only have data for declination of Sun and the ...
109 views

### Hills' mechanism for making Hypervelocity Stars

In Hill’s mechanism, the gravitational tidal force of a single MBH disrupts an approaching binary. One star is captured on an eccentric orbit around the MBH and, by conservation of energy, the ...
2k views

### Could the earth become a star if more mass was added?

I've heard that the only difference between a star and a planet is mass, meaning that if planets accredited enough mass they would too become stars. Does this mean that the star started off as a ...
32 views

### How to calculate the Subsolar's Latitude and Longitude for a given Date and Time from RA and Declination? [on hold]

I think that the latitude is equal to the declination. How to calculate the longitude from the RA?
266 views

### Struggling to understand the phases of the moon

Source Typically this diagram is how the phases of the moon are explained but the issue is this, namely, the phases seen on the right half are not possible. All the phases should appear on the left ...
1k views

### Can satellites travel in clusters?

Last night we saw a large cluster of what looked like exceptionally bright stars that moved, as a group, across the night sky in Lancaster, PA. It was about 9:15 pm, and they moved roughly from SW to ...
73 views

### How spectrographs that measure radial velocities manage to translate variations in the stars' spectrum lines into the “speed” of the star?

Like ESPRESSO or CARMENES, for example. I just don't understand the process or the way these spectrographs manage to obtain the velocity of the "wobble" of the star (due to the presence of another ...
77 views

### How to determine the orbital period of an asteroid using Kepler laws given its orbit's radius?

Given that the mean distance of an asteroid from the Sun is $450 \times 10^6$ km is it possible that the asteroid completes one rotation around the Sun in two years? According to the third law of ...