eshaya
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Is there an equivalent of the red shift effect for cosmic rays?
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6 votes

Yes, there is a "retardation of the co-moving velocity" of particles. It is important to take it into account to understand the time history of peculiar velocities of galaxies and for ...

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Fate of lone spiral galaxies?
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2 votes

I think there are a few misconceptions floating around here. The Hubble Sequence is not a sequence in time. Hubble did not mean to imply that galaxies flow from one side to the other in the sequence ...

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What is a hard spectral state vs. a soft spectral state?
1 votes

Active galaxies are known to change state as seen by a change in slope of their X-ray and gamma-ray spectra. We say that a spectrum has become harder (or changed to its hard state) when the slope ...

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What is the antonym of "closest approach"?
1 votes

Historically, astronomers focused on the easier to measure conjunctions, since getting distances is very hard, so knowing exactly when greatest distance occurs was not possible. Planets interior to ...

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Can lightning occur in stars like the Sun?
38 votes

Stars are not actually gaseous, they are plasmas, i.e., highly ionized. Hence, the entire star is highly conductive and does not easily develop the voltage difference via friction needed for lightning ...

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How can cosmological bubble universes "collide" with each other?
0 votes

There is a bit of a semantic mess in multiverse talk. The eternal inflation theory claims that, on the largest scales, inflation (exceptionally rapid expansion) continues for a long time, perhaps ...

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Origin of heavier elements on earth?
4 votes

Supernova ejecta expand at velocities between 5,000 km/s and 30,000 km/s. Lets take 10,000 km/s as typical. The speed of light, c, is 300,000 km/s, so 10,000 km/s = c/30. So, it would take 120 years ...

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Does the Zwicky Transient Facility only run when triggered by a cell phone?
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2 votes

The ZTF is operating on most clear nights on an automated queue of pointings. When they discover transients, they inform TNS which may trigger other observatories to point at the same object, just as ...

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Is this the best non-radio image of whatever's at the center of M87? How was it taken?
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2 votes

Your top image is this from Dr Jean Lorre stock science images. Just a photo showing stars and the optical jet with a 22 MB CCD camera through a small telescope. It is unfortunate that he chose a ...

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Does the Earth orbiting around the Earth-Moon barycenter cause a measurable centrifugal force?
2 votes

The Earth and Moon are in orbit about each other, which means that the centrifugal (outward inertial) force $M_iV_i^2/d_i$ is balanced with the centripetal (real inward force), ie $GM_{\oplus}M_{\...

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Deep space radiation distribution
3 votes

If you were in deep space, i,e., a spot somewhere between galaxies, then the night sky would look a lot like the sky seen by astronauts in the ISS, when they look away from both the ecliptic plane ...

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What is the cause of all of these sharp, concentric rings around bright stars in this HST image?
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8 votes

The diffraction pattern at the focal plane created by a circular aperture is called an Airy Disk or Airy Pattern. Both the outer opening and the inner hole plus secondary contribute to the exact ...

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Light pollution and apparent magnitude of objects in solar system
3 votes

The answer is yes: dust is highly constrained to the ecliptic plane and so viewing from above the plane would result in less light that needs to be subtracted from observations of the solar corona. ...

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Deriving Dark Matter; specifically looking for a table of stellar speed versus distance from center of galaxy to derive dark matter
2 votes

It is very difficult to measure Galactic orbital speeds of stars in our galaxy for several reasons. We are moving with them and do not have a reliable measurement yet of even our own orbital motion. ...

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Does this amateur observation hold a record even including robotic searches for supernovae?
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5 votes

No, supernovae have been observed earlier and with better cadence than this one. The Kepler Satellite has been observing galaxies at a 30 minute cadence from months before the supernova explosion to ...

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How well is Earth’s motion through the universe quantified?
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1 votes

Surprisingly, we will soon be able to do this well enough to go back several hundred million years and place ourselves, if not in the solar system, inside the Galaxy and roughly in the right part of ...

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Sunlight intensity during a day
1 votes

The sunlight intensity is the cosine of the sun's elevation angle $\alpha$. How to calculate the position of the sun is described simply at PVEducation.com. To summarize the relevant equations: $\...

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Units of integrated flux density (irradiance) along longitudes
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1 votes

You could say "MJ in bins of x degrees in l" where x is the degrees spanned by a pixel. Or, you could divide the fluxes by the steradians in each column and keep it MJ/sr or "Mean MJ/sr within ...

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What kind of a visual trajectory would an asteroid have if it were to hit Earth?
4 votes

There is no simple answer to this question other than: you have to do the math. Most often you would see the asteroid brightening more rapidly and moving across the sky faster as the days pass, but ...

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Does gravity repel when dark energy is involved?
0 votes

We do not yet know the answer to this question. We observe the universal expansion, which should be slowing down from mutual gravitational attraction, is not slowing down as much as it should and ...

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Why is NEOWISE used for galactic observation?
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1 votes

After WISE ran out of cryogens to cool its detectors it was re-purposed to look for asteroids. This was possible because the detectors for 3.4 microns and 4.6 microns could work at higher ...

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Can a Neutron Star become charged?
2 votes

The pressures are so great in a neutron star that most of the electrons combine with protons and become neutrons. A statistical equilibrium is set up in which neutrons, because they are unstable, ...

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How did the Ancients understand the ecliptic using the Ptolemaic system
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They saw the stars, planets, Moon and the sun (the Celestial Sphere) rotate around the Earth each day. The Sun however, moved about 1 degree each day across the Celestial Sphere, so by the end of a ...

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If a rocky world is large enough (not a gas or ice giant) can it have helium from the primordial disk in its atmosphere?
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2 votes

The snow line is the inner radius from the star where the water condenses onto dust and larger particles as ice (ie snowballs). The hydrogen and helium never freezes out. Planets start forming by ...

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Star systems forming when large gravitational force is applied
1 votes

Most binary stars are believed to have formed together as they condensed out of a common rotating dense cloud of gas and dust. A few more form when, coincidentally, two are ejected from a cluster at ...

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Does our current understanding of the mass of black hole only allow for it to be located at the singularity?
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1 votes

As a star or neutron star collapses to form a blackhole there will, of course, be a moment when the matter is distributed everywhere within the event horizon. So, there may not be a singularity ...

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Is TESS replaceable by gound-based-small-telescope arrays?
1 votes

I think the biggest issue is the precision of the photometry. The atmospheric turbulence limits ground-based photometric precision to 1%. In space, Kepler achieved about 0.001% on bright stars over ...

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In a finite universe, what happens when light reaches the boundary?
0 votes

This is one of the most essential questions in cosmology. The first gedankenexperiment probably. If the universe were finite what could be at the boundary? If there were some sort of wall, what would ...

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What complementary observation campaigns have looked at Kepler's field of view?
2 votes

The Kepler Field had been covered in the near IR by the 2MASS catalog since that covered the entire northern sky. There was also a Smithsonian Institute program called the Kepler Input Catalog ...

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Are exo-meteoroids possible?
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4 votes

Most, and perhaps all, stars form in stellar clusters. Most likely, the sun formed in a open cluster. In clusters the density of stars is quite high, therefore close encounters are common. So, I ...

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