# All Questions

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77 views

### How to calculate phase angle of a satellite?

I'm making a program for predicting satellite passes. I'm trying to find out if the satellite is illuminated by the Sun and not in Earth's shadow. I need to know its phase angle: the angle between the ...
63 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 ...
73 views

### Fastest recorded apparent motion of a comet or asteroid seen from Earth (degrees/day)?

If I've done my maths correctly in this answer comet 2I/Borisov (C/2019 Q4) was seen to move about 0.2 degrees in 7 hours, which is almost 0.7 degrees per day. I'm assuming this is pretty rapid ...
2k views

### Reason for disqualifying Pluto as a Planet? [duplicate]

Pluto is no longer a member of the planets in the solar system. Why was it disqualified as a planet? What is the criteria for classifying an Astronomical Object as a Planet? Does this criteria apply ...
3k views

### What mechanism causes oscillations of the solar system's orbit about the galactic plane?

In a recent paper (news release here) Lisa Randall and Matthew Reece propose that a dark matter disk coinciding with the galactic plane together with the solar system's oscillations through the ...
2k views

### Coordinate system for space [closed]

I am high school student, I have doubt if I have to locate a planet or any star in space, how do I locate it, because we have no perfect coordinate system, I have read in some books, that time is ...
3 views

### Curiosity landing system versus Spirit/Opportunity's [migrated]

Spirit/Opportunity used airbags to land while Curiosity had a "carrier" with thrusters and chords - which to me sounds heavier and much more complex, therefore also riskier. It seems that it would ...
126 views

### What do the fusing 'onion layers' of a pre-supernova star look like to scale?

I'm sure we've all seen the diagrams of various layers of element fusion from hydrogen to silicon in a star that's just about to go supernova. (Picture from courses.lumenlearning.com) I suspect ...
113 views

### Did Hubble see a pair of UFOs? (Identify this artifact)

The image below is this one, found in this group of Hubble space telescope images of the interstellar comet 2I/Borisov (C/2019 Q4). Can anyone recognize this pair of artifacts in the upper right ...
2k views

### Where to obtain Tycho Brahe's data?

I would like to obtain Tycho Brahe's data on Mars. What would be an authoritative source? One source I could find is this page (the data is given as an Excel file) but I have no idea can that be ...
40 views

### Questions about Hubble's brand new view of an interstellar comet (video)

This GIF is made (via giphy.com) from the new NASA Goddard video Hubble's New Image of Interstellar Object and if I understand correctly many (if not all) of these frames are from https://archive....
30 views

### Photometric redshift - empirical methods (machine learning)

I am currently learning about estimation of photometric redshifts with machine learning methods (or empirical methods in general). These methods use the knowledge about the photometry and the ...
3k views

### Which are stars and which are noise in this comet photo?

The Forbes news article NASA's Hubble Telescope Snaps Best Images Yet Of Our First Interstellar Comet shows the image below (which I have since annotated) of comet 2I/Borisov (C/2019 Q4) and links to ...
106 views

### The dominance of Gravity vs Strength and its dependency on crater size

So I am trying to write a research paper (about 3700 words) for high school about the topic "The dominance of Gravity vs Strength and its dependency on crater size" or something similar. I have ...
15k views

### How loud would the Sun be?

Sound can't travel through outer space. But if it could, how loud would the Sun be? Would the sound be dangerous to life on Earth, or would we barely hear it from this distance?
62 views

How to plot Doppler profile corresponding to the spectral line? The spectral line was plotted from data: flux with respect to wavelenght and I know the temperature. These two function are Doppler ...
495 views

### How far away is the nearest compact star remnant likely to be?

Neutron stars and black holes are hard to detect when they are solitary, and there seems to be big uncertainties about how common they are. White dwarfs are much easier to detect and the nearest one ...
87 views

### Time dilation due to the expansion of the universe

This is not a homework question. I want some help in being able to clearly perceive the expansion of the universe and the consequences thereof. We know that the universe is expanding in an ...
74 views

### Why was Dawn's (the spacecraft) flight path circular? [closed]

In comparison to the twin Voyagers, Dawn's flight path circled the sun in an anti-clockwise manner. The map of its path shows its targets, Ceres and Vesta were in a trajectory that was close to a ...
71 views

### Calculating historical star maps from proper motion

I'm working on some software which needs to calculate the position of stars and galaxies visible to the naked eye at different periods of human history. The Yale Bright Star Catalogue gives the ...
80 views

### Is intrastellar commonly used by astronomers to refer to objects within our solar system?

The CNET article Interstellar comet Borisov looks ordinary, making Oumuamua even weirder says: A paper published Monday in Nature Astronomy lays out the early data on Borisov, which is just the ...
41 views

### Overhead (galactic North) view of the stars in and around the Vela Constellation with distance

I am working on a project and would like to have a star map--seen from "above" (Galactic North?) that calls out the stars in the Vela constellation and shows their distance from sol / earth. I ...
2k views

### Why can we observe the Cosmic Microwave Background no matter the direction we look?

I often read that the CMB was released from everywhere in the Universe, in every direction. If that statement is true, can someone elaborate what "everywhere in the universe, in every direction" ...
66 views

### Seeing a star near zenith around sunset

I'm recalling while taking a university astronomy class the professor brought a few of us up to the observatory, around sunset. He showed us a star near zenith with the telescope. After we left the ...
42 views

### How to calculate the orbital velocity, the high-orbit (quasigeostationary) holding force and the shadow of the disk on Earth? [closed]

[] The following data are given: • The circular orbit of the disk D (quasigeostationary orbit) parallel to the geostationary orbit. • Located 4,505 km to the north of the equatorial plane, above ...
35 views

I am trying to perform wavelength calibration on an image but I am stuck by the identify task under the longslit package. So when I type :go on the command line after I set the parameters (see the ...
94 views

### Is there a way to tell the difference between earth andesite from Mars

I'm curios if there is a way to test if this sample might be Martian andesite. What type of oxygen isotope (or other) test can be done to address this in some way? As background, any information ...
590 views

### Why do shooting stars burn close to the ground sometimes?

I saw a shooting star as I was standing on the roof of my home. My home is double storey. And the height of that shooting star that I saw was maybe 10 to 13 meters. It was burned down at that height. ...
100 views

### Is there an optimum orbit for a hipparcos/GAIA-like parallax observatory

The GAIA spacecraft is currently mapping the stars in the Milky Way by parallax. It orbits in the Earth-Sun L2 lagrange point. The parallax observed from the spacecraft orbiting around the sun allows ...
191 views

### Can fish and other sea creatures survive in watery planets like Neptune or any other planets that has water?

I'm a bit curious since Neptune does not have a land surface and it is covered with water, I mean water has oxygen right? What will happen if we put some sea creatures in these watery planets? Can ...
48 views

### Dark forces and galactic filaments

Could it be that dark energy = momentum of hydrogen in galactic filaments, and dark matter the mass of the galactic filaments?
121 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 ...
50 views

### Spectral Class Breakdown

Where can I get a more detailed breakdown of Spectral Classes. Wikipedia only has it at Letter level rather than sublevel. For example, https://en.wikipedia.org/wiki/Stellar_classification has B ...
82 views

### How was Cassini able to measure and use the Earth-Mars distance to get the Earth-Sun distance?

How was Cassini able to measure and use he distance between Earth and Mars to get the Earth-Sun distance? How were the ratios of Earth-Mars and Earth-Sun calculated then? Given Kepler's laws all we ...
67 views

### Understanding The Fluctuations In The CMB Maps

If I'm understanding this correctly the fluctuations in CMB are a result of the "last scatter" of photons when electrons joined together with nuclei that before this formed plasma. CMB is among other ...
2k views

### Why is the Sun so bright, but you can feel it far away?

First of all, the Sun's surface temperature is only about 6000 K. Years ago I was working at at a melt work with furnace temperatures 0f about 2-3000 K; of course you could not be near a furnace ...
5k views

### Black Hole / Hawking Radiation: Why only capture anti-particle?

I may have some specifics wrong here. If so, don't focus on those. Just focus on the general thrust of my question. I "understand" (cough) that particle/anti-particle pairs form spontaneously in ...
2k views

### How much mass will the Sun have when it becomes a white dwarf?

In 4 billion years, when our Sun sheds all of its outer gas layers and turns into a white dwarf, how much mass will the white dwarf have compared to what the sun has today? Will the planets still ...
68 views

### What is the history of the Milky Way's relationship with Andromeda?

From what I've read, the Milky Way will collide with Andromeda in about 4 - 5 billion years, and a billion or so years after that the two will merge and become a giant elliptical galaxy. What I'm ...
10k views

### Why is Mars cold?

The surface temperatures of Mars are about -87C to 5C, which is much colder than that of Earth's. If Mars has 95% carbon dioxide, which is a Greenhouse gas, why is the surface of Mars so cold? ...
123 views

### Strange object crossing the sky

Was stargazing last night and spotted an object traversing the sky from roughly East to West. It had a bright light that was intermittently flashing but with three different intensities. The "third" ...
108 views

### Given that Kepler's Third Law as stated on most websites doesn't include mass, how does it work for planets in other star systems? [duplicate]

Kepler's Third Law as stated on websites I found while searching for "how to convert between a planet's orbital period and semi major axis" is $P^2 = A^3$ where P is the orbital period in years and A ...
36 views

### Find x,y,z velocity component of a star? [closed]

I am trying to find the initial x,y,z velocity components of the Epsilon Lyrae stars. How might I go about doing this? The radial velocities are available on Wikipedia, but I am not sure how to use ...
36 views

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### Where can I find permissibly licensed database of stars and constellations?

I'm working on a game engine of sorts, and one thing I did for a previous game which was under the GPL was I had a night sky with the constellations visibly connected and I'd like to do that again. I ...
60 views

### Does it make more sense to upgrade our existing telescope or to buy a new one?

We're at a bit of a crossroads here, since we're faced with what appears to be a tough choice. We've got a Celestron 11" SCT tube with a Losmandy G11 equatorial mount, all bought in 1996. The mount ...
259 views

### Split telescope into two eyes

I am looking for an appendage to attach to the end of a telescope which splits the image into two eyes instead of one. Does such an appendage exist?
110 views

### Venus-Saturn conjunction in Sagittarius on Dec 11, 2019 - How often does this happen?

Venus and Saturn will be approximately two finger widths apart in the constellation Sagittarius on December 11, 2019. I was wondering: how often do Venus and Saturn come together in the sky like this? ...