37 votes

Can a magnetic field of an object be stronger than its gravity?

It depends on what object it's acting on. There are many objects, including stars, that have magnetic fields where Lorentz forces on charged particles like electrons and protons are stronger than the ...
  • 5,250
23 votes
Accepted

What would the night sky look like if the Milky Way were the only galaxy in the universe?

I feel sure this is a repeat, but couldn't immediately find it. The only things in the night sky we can see (with the naked eye) that are not part of our own Galaxy are (on a good night) the Andromeda ...
  • 129k
18 votes

What would the night sky look like if the Milky Way were the only galaxy in the universe?

It wouldn't be too apparent, but there are a few objects that you can see in good viewing conditions with the naked eye that would disappear. Here they are in order of brightness. I marked the ...
17 votes
Accepted

Can a magnetic field of an object be stronger than its gravity?

Let's look at the proper magnetic force (as opposed to the Lorentz force on a moving, charged object described in @KenG's answer) on a specimen $S$ of magnetized material with mass $M_S$ as a way to ...
  • 30.4k
16 votes
Accepted

Are there more stars than all the words ever spoken by humans?

Number of stars in the observable universe There are about 100 to 200 billion galaxies in the observable universe. Galaxies range in size from a few billion to hundreds of trillions stars. Using 100 ...
  • 31.4k
14 votes
Accepted

On what basis is the information about the distance and velocity of the Voyager probes determined?

On what basis is the information about the distance and velocity of the Voyager probes determined? For distance: round-trip travel time of radio signals For velocity: Doppler-shift of round-trip ...
  • 30.4k
13 votes

What was the length of the solar day 73 million years ago?

There is evidence from Silurian coral fossils that, 430 My ago, there were 420 daily rotations in each annual season, compared to 365 days per year now. If we assume that the year (fixed by mean ...
  • 981
12 votes
Accepted

How to discover Neptune from the Uranus orbit (by computer simulation)

Here is what I did: Based on their masses, it is safest to initially consider Jupiter and Saturn as well as Uranus. It might also be fruitful to include the Earth in the analysis, to get relative ...
11 votes
Accepted

Why do we use FITS format for scientific images especially in astronomy? How is it different from formats such as JPEG, PNG etc?

File formats tend to be industry/field-specific, with the format, tools, and expectations of the field coevolving to become more dependent on each other over time. JPEG co-evolved with amateur digital ...
11 votes

How to know that the 21cm Hydrogen line is the actual emission and not any other redshifted line?

No, not really. The first thing is that we know that ${H}$ is far more abundant than other elements or simple molecules in the universe. The next thing is that the 21 cm line comes from a ...
11 votes
Accepted

What liquids can be found in the void space?

No liquid can be completely stable in a vacuum, since all liquids have some non-zero vapour pressure, and so will evaporate at some rate. However some liquids have an exceptionally low vapour pressure,...
  • 101k
10 votes

Which is more rare: Lunar eclipse or Solar eclipse?

Solar and lunar eclipses occur about equally often - between two and four times per year. However, when you do not intentionally travel around the world chasing solar eclipses, you are more likely to ...
  • 757
10 votes

What do the months and hours mean in Tomas Filsinger's Map of The Universe

I am Tomás the guy that designed it following astrocartography traditions. The thing that makes it confusing is that the position of the little suns in the Ecliptic are plotted against the stars at 12 ...
9 votes
Accepted

How can I contribute to the scientific community using my telescope?

Amateurs do useful scientific work by being many-handed and widely spread. Many Supernovae are discovered by amateurs. You need a set-up that can image one galaxy after another and look for any "new ...
  • 101k
9 votes

Can a magnetic field of an object be stronger than its gravity?

It isn't impossible, but the short answer is "no". A gravitational field will accelerate all matter and energy equally while a magnetic field will only accelerate moving electric charges (other ...
8 votes
Accepted

Astronomical ABCD...!

Seems a little contrived, essentially you just have to dig deep enough to find a specific enough category that matches the letter. But here you go : K - KBO (Kuiper Belt Object) , if you still don't ...
8 votes
Accepted

What do the months and hours mean in Tomas Filsinger's Map of The Universe

The hours show the lines of right ascension, where right ascension is one of two coordinates used to specify a point on the sky. (The other coordinate is declination, measured in degrees from the ...
  • 7,331
8 votes
Accepted

Have there been studies of "old photons" to see just how constant things like Planck constant has been?

You can not check if a dimensional constant has changed because you can always reverse that change by a smart change of coordinates (system of units). Despite that, since the current Physics assumes ...
7 votes

Why you use log to measure metallicity in galaxies?

The distribution of metallicities appear to be more evenly spread out in logspace than in linear space. The reason for this can be ascribed to there being no preferred scale for the abundance of a ...
  • 35.3k
7 votes

Why didn't Johannes Kepler use data about more planets?

Kepler could, with a lot of work, apply his analysis to other planets of course - but it won't help in proving his point of elliptical path. There are only two planets where this elliptical path could ...
  • 1,607
7 votes

Why didn't Johannes Kepler use data about more planets?

I know that quoting Wikipedia is frowned upon here, but as there has been no other answer posted, this is what the Wikipedia article on Kepler has to say about the matter: He then set about ...
7 votes

Can some stars not emit any energy in the visible spectrum?

Light that is not light That's meaningless. All light is electromagnetic radiation. A finite part of the infinitely large range of the electromagnetic spectrum is visible light. So you should talk ...
7 votes
Accepted

When black holes forms out of a supernova do they have a very high velocity?

There is no specific answer to this -- anything from "just sits there" to flys away at high speed is possible. It all depends on the symmetry of the supernova (SN) explosion. Extensive modelling ...
  • 7,430
7 votes
Accepted

Why the more-luminous star has larger surface area when two stars have the same temperature?

I'd say your problem is that you are imagining the light rays emanating out from the center of the star. Try it again with light emanating from each square area on the surface, and you will see that ...
  • 5,250
7 votes
Accepted

Difference between J2000, FK5 and ICRS coordinate systems? Which one does the Yale Bright Star Catalog use?

The questions confuses things: J2000 is the epoch / equinox in which the catalogue is in. This defines the reference point in time for Right Ascension and Declination. See e.g. here https://en....
6 votes

Equations for coordinates of solar system objects

It depends a bit on how precise you would want to be. A very good discussion on how to calculate the orbits of solar system objects is given in the book by Jean Meeus, Astronomical Algorithms (1999), ...
  • 3,341
6 votes
Accepted

If the universe is 'flat', what shape is it?

Let me clear this up first. Shape of the Universe means the curvature of the Universe. The meaning of "shape" is not the same as in "what is the shape of this object I'm holding". It doesn't mean that ...
6 votes

The M-theory to understand black holes

Can someone please explain it to me whether the M-theory can be used to explain what is happening in the centre of the black hole where the singularity exists? In Layman astronomy - yes, M-Theory ...
  • 23.2k
6 votes

How can I contribute to the scientific community using my telescope?

You can also help the study of variable stars and in particular their light curves - You do not require a big scope for this. See for example the American Association of Variable Star Observers, or ...
  • 4,124
6 votes

Relation between angular resolution and aperture?

The angular resolution only tells you your ability to distinguish ("resolve") two separate points of light. For example, your ability to distinguish the two distinct headlamps on a car from being a ...
  • 161

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