All Questions

0
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0answers
11 views

What is the relative strength of the 21cm compared to the CMB in Spectral Irradiance ($Jy\cdot sr^{-1}$)

I understand that radio astronomers like to work in terms of Brightness Temperature, due to the various conveniences it brings mathematically. The strength of the 21cm appears to be roughly 3 orders ...
3
votes
1answer
29 views

Non-thermal Sunyaev-Zel'dovich effect

Exactly what is the non-thermal Sunyaev-Zel'dovich effect? From what I understand from reading several papers by Mark Birkinshaw and Sergio Colafrancesco, I get the rough idea that the non-thermal SZ ...
1
vote
0answers
35 views

Angle between earth's angular momentum and earth's axis

I think this picture is correct because for earth astronomical day is slightly shorter than solar day. (Is it a rule of thumb for planets? Where can I read such data?) Source So the angle between ...
3
votes
1answer
44 views
+50

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 ...
5
votes
2answers
71 views

MeerKAT's Epic Image of the Galactic Centre, what are we seeing?

In this answer as well as this one, I've linked to New Jersey Institute of Technology's Dr. Dale Gary's nicely-written Physics 728 Radio Astronomy; Lecture #1 notes where I can see the image below. It ...
1
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0answers
26 views

Do contact binaries such as Ultima Thule affect our current theories on how the Moon formed?

While I was reading about Ultima Thule, I was wondering if the discovery of contact binary objects had any effect on our current theories of how the Moon formed?
1
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0answers
23 views

Luminosity of the Milky Way compared to Seyfert galaxies

This page lists the total luminosity of the Milky Way Galaxy to be $4\times10^{10}$ $L_{sol}$, and $L_{sol}=3.86 \times10^{33}$ ergs.sec$^{-1}$; this gives a total luminosity for the MW of $1.54\...
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0answers
14 views

Anisotropy of quasar distribution

In a paper titled Arp, H. (1984). Distribution of quasars on the sky. Journal of Astrophysics and Astronomy, 5(1):31-41. at Journal of Astrophysics and Astronomy, Halton Arp wrote that there is ...
3
votes
1answer
39 views

Why would atmospheric absorption increase rather than decrease the antenna temperature in Penzias and Wilson's famous CMB observation?

The classic paper A MEASUREMENT OF EXCESS ANTENNA TEMPERATURE AT 4080 Mc/s begins: Measurements of the effective zenith noise temperature of the 20-foot horn-reflector antenna (Crawford, Hogg, and ...
1
vote
0answers
44 views

Expansion of space - how do we end up with an unobservable region?

I've just been answering a question on this issue,in physics SE,and realised that my answer conceals a point I don't myself understand. I understand that The expansion of metric isn't affected by ...
1
vote
2answers
79 views

If objects don't move when the universe expands, how can the expansion result in redshift?

I am approaching this topic from a layman's perspective and view this as a logic puzzle, but when someone tries to get me to accept the logic, I'm never convinced by their arguments. According to ...
0
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0answers
17 views

National Geographic 76/700EQ telescope finder scope - help needed

I have this National Geographic 76/700EQ telescope I picked up at a second-hand store for $50. Anyone know how to adjust the finder scope on it? I turn the 2 pins on the top and side but it does not ...
5
votes
3answers
96 views

Does any asteroid we have ever seen have a hot core like earth.?

I was wondering if any of the asteroids we have ever seen has a hot core like Earth's. I'm thinking that Earth has a strong gravitational field and so formation would have involved a lot of ...
3
votes
3answers
40 views

Does coronal mass ejection include radiation at optical wavelengths?

It is known that during Solar/Stellar Flare, plasma from the corona of the star is released into the space, and travels comparatively slowly. In an hypothetical situation, does the coronal mass also ...
2
votes
1answer
49 views

What causes “North-South ambiguity” when doppler radar imaging a planet surface equator on?

I'm having a hard time understanding why there would be this ambiguity. Also, why would this be not the case if the planet was viewed pole on? Edit: "NOrth SOuth ambiguity" is a term used in a paper ...
2
votes
1answer
38 views

Is the delay to correlate the signal from one dish to another on a VLA radio telescope longer for red shifted objects?

When observing 2 objects side by side close to the horizon with a very large array, one receding fast & red shifted, is the delay to correlate the signal from the closest dishes to the further ...
0
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0answers
19 views

Examples of radio correlations over times much longer than interferometric baselines?

Very Long Baseline Interferometry or VLBI such as the Event Horizon Telescope or JPL's delta-DOR (see below) uses baselines of the order of the Earth's diameter. Spacecraft position determination ...
2
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0answers
116 views

Are quasars simply AGNs that are viewed from a particular angle?

I found the picture below in an answer to the post "Was the Milky Way ever a quasar". The picture is published on a website belonging to "NASA/IPAC Extragalactic Database". In the answer that has 16 "...
2
votes
1answer
81 views

Discontinuity in space-time

What I understood about it till now is that space-time fabric is kind of broken there. Please tell me whether I am correct. If it's true then does it mean that perception of time will stop there? I ...
3
votes
1answer
57 views

Could a planet form without a molten state?

Based on what I know, the Earth accreted out of the solar nebula, had a period when it was entirely molten, and then slowly cooled. Could a planet form without ever passing through a molten phase?
11
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1answer
2k views

Are astronomers waiting to see something in an image from a gravitational lens that they've already seen in an adjacent image?

@RobJeffries' answer to the question Does gravitational lensing provide time evolution information? points out that there can be a substantial different in arrival times of light from a given source ...
1
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0answers
37 views

Within a given image of a multiple-image producing gravitational lens, does Fermat's principle apply?

The question Does gravitational lensing provide time evolution information? is excellent! When we see multiple images of the same object because of the phenomenon of gravitational lensing, do all ...
3
votes
2answers
92 views

Why is only a narrow chunk of sky darkened in this amazing Curiosity solar eclipse GIF from Mars?

I found three NASA JPL images in the sequence PIA23133, PIA23134, and PIA23135. They were taken by the Curiosity Rover on Mars and show solar eclipses by Mars' two moons. Details of these images are ...
6
votes
1answer
96 views

Does gravitational lensing provide time evolution information?

When we see multiple images of the same object because of the phenomenon of gravitational lensing, do all the images show the lensed object at the same point in time? Does it take the same amount of ...
0
votes
1answer
63 views

Does the Sun's atmosphere have a scale height?

Much of the Earth's atmosphere has a scale height $h$ of roughly 7 to 8 kilometers such that the local density varies as $\exp(-(r-r_0)/h)$ where r is the radius vector and $r_0$ would be some ...
1
vote
1answer
38 views

Finding angle between a given sky position and ecliptic pole

Given a right ascension in degrees and declination in degrees (say, 88 degrees RA, -63 degrees DEC) I want to find the angle between that location and the ecliptic pole (90 degrees RA, -66 degrees DEC....
2
votes
1answer
81 views

Can Fermi Bubbles be produced in non-spiral galaxies?

In 2010 observations with the Fermi Gamma-ray Space Telescope discovered giant bubbles which have been named Fermi Bubbles. Similar structures have also been discovered by Pshirkov et al. (2016) ...
2
votes
0answers
31 views

Spectra from Temperature and Emission Measure [closed]

Having the solar flare fluxes on the two bands of GOES (0.05-0.4 nm and 0.1-0.8 nm) I need to calculate the flux between 0.05 and 0.2 nm.
5
votes
2answers
90 views

Why does the sun have a convection layer and a radiation layer?

Why is the outer section of the sun convective but the inner section stable and only radiative? They are both made up of the same kind of matter, both heated by the core.
1
vote
2answers
48 views

How would I search within an angular distance of an object corresponding to a distance in parsecs?

I'm interested in the learning about the local densities around galaxies. I've found myself a bit confused on how to relate angular distances (arcseconds) with physical distances (parsecs) when ...
3
votes
1answer
74 views

How to determine the mass of a galaxy?

I am having a slight disagreement with my professor. We can measure the mass of a distant star cluster from: A.Its color B.Its radius C.Its metallicity D.Smearing of lines in ...
0
votes
1answer
46 views

What values can a color index variable get?

I am a statistician with love and passion for astronomy. I try to explain some outliers I found in the values of quasars - color indexes. I found four (4) values close to twenty (20). Is that ...
0
votes
1answer
51 views

What would happen if space-time began to contract? [closed]

Assume that the expansion of the universe stops and it starts to contract again. What would happen? Would only distances between objects get smaller, or are there other effects we can expect?
2
votes
2answers
86 views

Why does the Sun show different colour at midday and at morning?

As we see every day in the morning the sun shows a red-orange colour but at midday has a blue-white like colour why? Is it concerned with the distance from the earth or about intensity? How do you ...
2
votes
0answers
75 views

Is there a database of all known star names/identifiers?

I am looking for a list of all known identifiers used for stars. I'm not sure on the terminology. While I do want the "proper names", I also want whatever identifier is used for each star detected, ...
0
votes
1answer
39 views

At what annual rate are new exoplanets being recognized? How does it compare to new asteroids?

I just read the BBC News article Exoplanet tally set to pass 4,000 mark . It makes me wonder about the annual rate that new exoplanets being recognized, and how it compares to the rate of new ...
3
votes
0answers
38 views

What is the relationship between AGN and [OIII]

I read that we can observe [OIII] from AGNs but what processes in AGNs produces these lines why we can use them to trace or tell if that galaxy is active or not?
-1
votes
1answer
61 views

Compare this planet to Earth and determined its habitability (can humans live in this environment?) [closed]

I'm given this set of data and I need to describe the habitability. Would this not be habitable since the temperature of the albedo and the equilibrium is similar to Earth's or does the Spectral Type ...
3
votes
3answers
139 views

Do white dwarfs produce stellar wind? If not, why is that?

I've been told white dwarfs don't produce stellar wind like the sun produces solar winds. I don't quite understand why that is and can't really find any evidence that confirms or denies that. My ...
1
vote
2answers
59 views

Do white dwarfs lose mass as they fade to black dwarfs? Is there a correlation between temperature, mass, and radius?

I'm having a difficult time understanding certain behaviors of white dwarfs. I understand how mass is lost in the red giant to white dwarf transition process. I understand that white dwarfs can ...
0
votes
1answer
45 views

Is there a theoretical minimum mass main sequence star that can become a red giant?

Wikipedia's Red Giant page says they range in mass from 0.3 to 0.8 solar masses. Which corresponds to an initial mass of a bit less than 1 solar mass, about 0.8 or so, if I was to estimate and a few ...
2
votes
2answers
100 views

'Geocentric' view of orbits

Given our real solar system how would planet orbits plot look like if we fix earth in the middle (put earth in the middle and draw a real orbit of a given planet) ? What would be the shape of its ...
0
votes
0answers
41 views

How to fit a light curve from an exoplanet transit

I've realized the transit of an exoplanet. Now, I want to fit the points I obtain to study the light curve of the transit. But i don't now what math function I can use to do that. Do you have any idea ...
1
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0answers
21 views

How to draw an orbit from Orbital Elements using Transform3DGroup

I am trying to draw an orbit using the Transform3DGroup class in the C# .NET framework. I have orbital elements a, e, i, RAAN, ArgPer, trueAnom. The algorithm that spits these out for me also gives me ...
3
votes
1answer
72 views

What projection would I use to map the northern night sky onto a geodesic dome?

I'm trying to create a geodesic dome with the stars of the northern night sky inscribed on the outside. The highest point of the dome would be the celestial north pole. How do I create a map that ...
19
votes
3answers
5k views

Help understanding this unsettling image of Titan, Epimetheus, and Saturn's rings?

The NY Times article Saturn’s Rings Are Sculpted by a Crew of Mini-Moons is really interesting and links to the recent paywalled paper in Science Close Cassini flybys of Saturn’s ring moons Pan, ...
6
votes
2answers
157 views

Measures for the degeneracy from protons?

Come to think of it, the only things we hear about degeneracy is neutron and electron. I made a generalization: White Dwarf: Supported by electron degeneracy. Neutron Star: Supported by neutron ...
1
vote
0answers
27 views

Relationship between photometric colour and redshift, part two

In the graphs in my previous question here, there are negative-sloped regions as the colour-z relationship oscillates. So if I look at how the I-W2 and W3-U colours change with redshift, as I've done ...
1
vote
1answer
29 views

Relationship between photometric colour and redshift

In this paper, the authors describe the theoretical relationship between photometric colours, particularly in Figures 1 and 6: Since the colour is the difference between two magnitudes, and the ...
1
vote
1answer
79 views

Did universe have finite hydrogen

According to this video stars at end of time and many others on fate of universe they all agree on one thing that stars will eventually convert all the hydrogen into heavier elements and eventually ...

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