# All Questions

6,706 questions
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### What might a CN filter be in the context of comet watching? Is it showing dust, or gas, or something else?

In this post on the website for the Comet Wirtanen Observing Campaign at wirtanen.astro.umd.edu, there's mention of a CN filter being used to observe the comet, and this cool GIF. What exactly is a ...
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I am reading about the interior temperature structure of Jupiter. It says in various texts that there are regions in Jupiter's atmosphere which are well-approximated by a dry adiabatic lapse rate. ...
34 views

### Can a moon have a moon? [duplicate]

Is it possible for a natural moon to have a natural moon? What is the limit to when satellites on satellites becomes to unnatural for it to be possible?
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### Is there a name for this type of orbit of a natural satellite?

Is there a name for the orbit of a natural satellite of a planet who's period is the same as the rotational period of the planet, but the orbital motion has the opposite sense than the planet's ...
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### Why is Neptune true anomaly decreasing?

So I've been having fun with trying to determine where the perihelia of different planets are (using JPL Horizons). And by the time I got to Saturn, something weird started happening. I've noticed ...
37 views

### Is Titan Better or Mars? [on hold]

Isn't Titan better to colonize than Mars? It has a thick atmosphere which is made up of nitrogen like our planet's. It doesn't have a magnetic field, but it does get a type of protection from Saturn. ...
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### Why aren't GPS clocks sufficient to synchronize VLBI observations?

In very long baseline interferometry, it is typical to use a hydrogen maser atomic clock to sample data. However, given how expensive these atomic clocks are, it seems surprising that more ...
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### If space was n>3 dimensional, would clouds of particles still turn into 2D disks due to gravity?

I don't fully understand why clouds of particles which turn into galaxies and solar systems usually result in an (approximately) 2D shape, but whatever. Would they still result in an almost 2D shape ...
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### How can we learn the inclination of the orbiting plane of the exoplanets using radial speed method?

I heard about the radial speed method to discover exoplanets a few years ago, however, these questions kept confusing me. If we know a planet star of mess $m$ is orbiting a star by interpreting the ...
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### What would happen if someone had a telescope and watched Betelgeuse when it goes supernova?

Would that person go blind? Neutrino detectors and the abundance of Neutrinos would detect the upcoming visible show about 3 hours before any visible signs, so there would be time to point certain ...
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### How are exoplanets with 10,000 day periods discovered with the radial velocity method?

The radial velocity technique has apparently been used to discover exoplanets with extremely long orbital periods of ~10,000 days. For example, see this link: https://exoplanetarchive.ipac.caltech....
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What frequency distribution law applies to a random point in deep space that is assumed to be far away from any particular source of radiation. Can it be expressed by some form of Plancks/Bose-...
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### Why is the shape of the Moon spherical? [duplicate]

The Moon does not rotate on its own axis. If I am right, for something to gain a spherical shape it has to rotate on its own axis. We know that the Moon does not rotate on its own axis. How can this ...
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### How does ALMA produce stable, mutually coherent ~THz local oscillators for all of their dishes?

The ALMA (Atacama Large Millimetre/submillimetre Array) radio telescope's band-10 capabaility is now operational, per this answer. That's confirmed by NRAO's First Science with ALMA’s Highest-...
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### Discovery of Near Earth Objects (NEO's)

Near Earth Objects (NEO's) have been mapped by NASA and JPL since 1990's. The graph below shows how many of these potential planet-killers have been found and classified over the years. I am curious ...
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### How often do they move most/all of ALMA's dishes?

The Phys.org article Unknown treasure trove of planets found hiding in dust reports on recently published radio measurements (~1.3mm) of planetary systems forming around stars in Taurus: Scientists ...
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### What direct or indirect observations of dust can one make by eye or with binoculars?

The solar system and space in general has plenty of dust, and dust has major impacts on observing both visually and in radio astronomy. If I wanted to "see dust" in space, or see its effects, using ...
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### What is this thin, square-ish object on asteroid Bennu? How big is it?

What could this square thing be? Roughly how big is it? From BGR's Our first up-close look at the Bennu asteroid is a messy one: rotated, 2x zoomed, and sharpened. unscientifically:
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### Current delay for radio signals from the Mars InSight mission

I've been meaning to post it on the day when InSight landed but just got around to it now. When they broadcasted landing in real-time, it really wasn't in real-time because radio signals from Mars ...
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### A non rotating asteroid of huge mass collides with earth. After the collision, does the length of the day on earth change?

A non rotating asteroid of huge mass collides with earth. After the collision, would the length of the day on earth increase or decrease? Why?
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### Precise declination of Moon

The moon follows 5.14 deg inclined path. the ecliptic and the Moon's path coincide are called 'nodes', and they travel around the ecliptic in a period of 18.66 years. Once every 18.66 years, the ...
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### What does “all stop” mean in reality?

In science fiction, when a starship captain commands "all stop," the audience simply assumes that, like a terrestrial naval ship anchored to the ocean floor, the ship literally comes to a complete ...
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### Is the nose of the solar system and the solar apex the same thing?

Results from the IBEX satellite indicate the nose of the solar system is pointing to the constellation Scorpius. Various sources say the solar apex is pointing to the constellation Hercules. Are the ...
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### How do black hole spinning at speed of light expose its singularity?

Black hole can spin very rapidly something about conserving momentum once a massive star used up its fuel and collapsed under it own weight, if black hole can spin at speed of light it could expose ...
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### Why doesn't the equipartition theorem disallow spinning dust?

This excellent answer to the question What is the physics of the “spinning dust” contribution to Cosmic Microwave Background measurements? Is well sourced. The abstract of one of the papers there, ...
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### WCS.pix2world: Read in latitude and longitude of entire FITS field

I have FITS file in pixel coordinates. I want to basically read in its latitude and longitude. I know we can use something following: from astropy import WCS from astropy.units as units ...
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### What's the easiest way to get 3D-positional data of galaxies

Is there a database with cartesian coordinates (x, y, z) of galaxies? I only need positional data and calculating that using degrees and redshift for all galaxies could take a while and would be ...
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### Are there Dark Stars

In the visible universe, we have a lot of matter to energy conversion going on in stars. Is there an equivalent structure that is converting dark matter to dark energy?
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### Very Large and Very very Bright [duplicate]

Between 3am ish and sunrise, I can see in the Northern sky, from North of Seattle WA something very bright and very large (close) in the sky. I have not been able to find anything. This is the biggest ...
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### What should be the future opportunities for a data scientist in Astronomy? [on hold]

I am a data scientist and as we all know in this highly emerging tech era every area-knowledge holds a front line position for data scientists. What would be the research scope type for a data ...
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### Dataset for globular star cluster

Where can I find the dataset(s) for a globular star cluster? The datasets should have the coordinates, color index (for different wavelengths) , magnitude etc. of every star in the cluster. I want ...
45 views

### Celestron NexStar 130 SLT Computerized Telescope GoTo Not Accurate

I am trying to use a Celestron NexStar 130 SLT Computerized Telescope, but I am not able to use the GoTo function. I do the three start alignment, it confirms matches, I make sure the level is ...
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### How could the Moon have arisen from a collision - what would make for an elliptical orbit?

One serious theory advanced for the creation of Earth's moon is that it resulted from a collision. However matter would be thrown off in all directions and some will fall back. How could a mass of ...
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### Are they really sure this isn't an Airy disk? How was that ruled out?

Are they sure this is a spherical shell of gas, and not just an Airy pattern? Image from: https://www.eso.org/public/images/eso0906b/ I get 180 pixels from center to the first minimum, and 72 pixels ...
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### If our earth hits Jupiter would it completely explode because of its methane atmosphere? [on hold]

Considering that methane's composition in Jupiter is mere 10% or so but is it still enough to trigger a huge explosion? And is there enough oxygen(From earths atmosphere) for that to happen?
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### How does Canada's radiotelescope CHIME manage polarization-dependent apodization of the fast f/0.25 optics?

CHIME, the Canadian Hydrogen Intensity Mapping Experiment uses four parabolic cylinder reflectors and a dense linear array of 256 x 2 polarization feeds along each focal line. Each feed is a dual ...
43 views

### What telescope might this be a model of, with Sir Fred Hoyle?

The BBC article Archaeopteryx: The day the fossil feathers flew has nothing to do with Astronomy but it shows a file photo of the famous astronomer Sir Fred Hoyle with a model of what looks like some ...
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### What can I learn from, or notice in the LIGO Orrery video?

The Ars Technica article Physicists detected gravitational waves from four new black-hole mergers notes that This brings the total number of events detected by LIGO and Virgo to 11. It also has a ...
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### How to find the radius of a satellite not knowing the mass

If I know the semi-major axis, the density of the planet, and orbital period.. how can I find the radius of the satellite? I can't think of any formula to use.
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### How strong are the stellar flares on YZ Ceti?

Doing research for a game and trying to understand the implications of the stellar flares from YZ Ceti. In short (ignoring the planets for now), if people were to build large space stations of various ...
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### Moons of migrated giant planets: Icy, Rocky, or none at all?

My understanding is that gas and ice giants form outside the "snow line" of their protoplanetary disk, then sometimes through gravitational interactions they are able to migrate into the inner star ...
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### Can't see any detail on planets with my new Celestron NexStar 130 SLT Computerized Telescope [duplicate]

Mars looks like a small white blob/circle and the same with all other planets. This is very frustrating. I've looked all over for a solution jumping from site to site and nothing. Please be different ...
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### Is there likely other significant objects we haven’t discovered in the solar system?

In the last few weeks, I read a few news that presented new advances in our understanding of the solar system, which implied we don’t really know our neighboorhood that well. I was wondering, how ...
96 views

### Why more matter still left after collision with anti-matter?

Question implies all, why is that? Why we exist even after equally creation of matter and anti-matter, any possible exception?
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### Numerous Stars Moving Across The Sky [duplicate]

It was amazing! they didn't move very fast to my eyes but they moved at a steady pace and there were so many of them. I was Starstruck as I stood there watching the stars move across the sky. When I ...
48 views

### Is the universe always expanding

Currently we observe that the universe is expanding. And this expansion even goes faster and faster. Why do we know (or presume) that this expansion started slowly at a singularity (i.e. big bang) ...
2k views

### In which direction is the sun travelling?

Relative to this simple drawing, can someone explain to me, in which direction is the sun and its solar system travelling, which star (irrespective of distance) is closest to that direction, and in ...
44 views

### What is the apparent magnitude of the weakest stars we can see in one telescope on the ground with a diameter of 2.4m? [duplicate]

All I know is its main mirror diameter; 2.40 m I also know that the eye, which its pupil is 5mm in diameter can see up to an apparent magnitude of 6. How can I calculate the apparent magnitude that ...