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0answers
16 views

Why is the peak value(s) of the spectral radiance of the CMB different if you calculate with freq. instead of wavelength?

On Wikipedia, the calculated value of the peak frequency of the cosmic microwave background is 160.23 GHz, but it says if you do the calculating with wavelengths, then convert to frequency, you get a ...
2
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3answers
1k views

Is it difficult to see DSO in your eyepiece?

I want to know if bringing the image of a DSO in eyepiece generally represents a problem for beginners in astronomy.
2
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1answer
27 views

What name was voted for Tau Boötis b by the Name Exoworlds Project?

In 2015, the exoplanet Tau Boötis b was included in the Name Exoworlds Project, a project where various international astronomy organizations would propose names for a selection of known exoplanets ...
6
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1answer
185 views

Lucky imaging with Celestron 14 - is this result reasonable?

I attempted to do some lucky imaging of Jupiter using a permanent installation (Celestron $14$" SCT + Paramount ME II) and Nikon D5600 attached directly to a Baader Hyperion 8-24mm eyepiece (...
2
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1answer
24 views

What determines if a comet's debris will produce periodic meteor showers?

Background I was wondering if the debris from the comet NEOWISE that recently passed Earth would provide meteor showers in the future. I looked up that the Perseid meteor showers happen when the Earth ...
35
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5answers
4k views

Why can't we see Saturn's phases from earth?

In the Astronomy Picture of the Day from August 8, 2020 ("Crescent Saturn"), the caption states From Earth, Saturn never shows a crescent phase Why is this? We can observe phases on ...
1
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1answer
28 views

how to find the approximate [stellar radius]? (distance from center to most distant star) of a circular flat disk galaxy based on its stellar mass?

I'm doing a high school programming project on drake's equation (simple galactic model) and wondered if there was a (simplified) way to find the radius (measured by the distance between the center and ...
1
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1answer
34 views

Why is the Cosmic Microwave Background at the same distance no matter the direction we look?

I've read from different sources that: The CMB is visible at a distance of 13.8 billion light years in all directions from Earth, leading scientists to determine that this is the true age of the ...
1
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1answer
52 views

Celestron C14 collimation and cleaning

When checking the collimation of a Celestron 14" SCT I took this image: My question is: how much will the particles causing the local aberrations affect the image quality? (i.e. do I need to ...
3
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1answer
113 views

Trappist-1 planet albedo

Is the albedo of any of the Trappist-1 planets know? Is it high enough so if you are on the surface of one of the planets, you can see the others? I looked up the distances from the star and size of ...
2
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1answer
464 views

How to correct observed flux densities for redshift

Say I have a spectrum of a galaxy at a redshift $z$, in flux density units of erg/s/cm^2/Angstrom. I'd like to recover the spectrum (in the same flux density units) at z=0, i.e. at its rest ...
1
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1answer
38 views

How can one determine the angle between the line of nodes and the major axis of the orbit of Mars?

Edit: What I really was looking for, was the difference in longitude on the orbit of Mars between its aphelion and the point where the north pole axis of Mars would point towards the Sun (northern ...
1
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2answers
87 views

can moon rise before sun and set after it in the same day

I found it mentioned in ancient Arabic astronomic book Kitāb al-Amwāl by Ibn Qutaybah (889 AD) Cresent can't be seen in the morning in the east in front of the sun and in the evening i the west ...
4
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1answer
247 views

Why the number of Long Gamma Ray Bursts(LGRBs) is greater that number of Short Gamma Ray Bursts(SGRBs)?

I collected https://www.google.com/url?sa=i&url=https%3A%2F%2Fgammaray.nsstc.nasa.gov%2Fbatse%2Fgrb%2Fduration%2F&psig=AOvVaw09lbpxsH2xmfnCCXQh4cKn&ust=1597302004094000&source=images&...
0
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1answer
43 views

Question about semi-major axis mean separation

I am currently doing an assignment but I cannot for the life of me understand what one of terms used means. Notice I am not trying to get help with the assignment itself, but rather to make me ...
1
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1answer
43 views

How to see Mars and Venus in color?

My telescope is Arsenal - Synta 70/700 AZ2 (refractor model). 140x max zoom (10 mm with Barlow). I could clearly see Jupiter and Saturn in color. I even saw brown stripes on Jupiter. Yet, when I tried ...
1
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1answer
41 views

Horizontal to Equatorial Conversion - Code

Following this tutorial I have been able to convert from Equatorial to Horizontal Coordinates and am now searching for a way to do the reverse. I understand this kind of question has been asked and ...
15
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5answers
5k views

Why are all quasars so far away?

Why are all quasars so far away? If the universe is homogeneous, we could expect to have a homogeneous distribution of quasars, but all of then seem to be far away from Earth. Why is that?
6
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2answers
1k views

What color is a red dwarf star?

I read recently that a red dwarf star might actually look white. I realize there's a wide range in red dwarf surface temperature, 2,500 to 3,500 degrees K, compared to 5,778 for our Sun. Metal at ...
3
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1answer
84 views

Can a telescope ever increase the apparent luminance of an extended object?

From what I know about common telescope designs, telescopes don't increase the apparent luminance of extended objects compared to the luminance seen with the naked eye. In this sense extended objects ...
1
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0answers
19 views

What is the mass and momentum of a relativistic jet?

Relativistic jets from accreting black holes are powerful radiation sources, but carries some ionized matter along. What are the estimates or observations of the mass or momentum flow in such jets?
1
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1answer
61 views

What satellite is this?

While out viewing the Perseid shower last night (8/11/20), we saw an interesting object that I'm trying to identify. We're in the vicinity of Portland, Oregon. It appeared to be traveling west->...
1
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2answers
26 views

How can I estimate the initial luminosity of a SNIa given initial mass of Ni-56?

The initial portion (and peak) of a SNIa's light curve is powered by the $\beta$-decay reaction: $$ ^{56}Ni \rightarrow ^{56}Co + e^+ + \nu_e + \gamma $$ Supposing we know how much Ni-56 is created in ...
2
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0answers
24 views

Determine spectral type of star from its properties

How can I determine spectral type of star, if I know all its another properties? For Example, Rigel A has spectral type B8Ia. Rigel has temperature 12 500 K. ...
9
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4answers
3k views

How much does the sky change in a few thousand years?

The "fixed stars" are not actually fixed, the earth's tilt changes over time etc., but all that happens slowly on human timescales. Imagine a Babylonian astronomer (or astrologist?) ...
5
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3answers
2k views

How long for a complete solar system cycle

Considering the solar system as a closed system, how long until all the planets pass twice by the same position relative to each other? I would say that you'd have to get the length of the year in ...
2
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0answers
63 views

How did we measure the mass of the universe?

In an wiki article, observable universe, it was mentioned that, Mass (ordinary matter) 1.5×10^53 kg I wonder how did we measure the mass of our observable universe?
0
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1answer
53 views

How to read light curve from .fits?

I have a .fits file (this one, in fact) containing the data of a fast radio burst, FRB110523. Is it possible to, from that, make a simpler file containing the intensity (integrated over all bands) as ...
2
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2answers
128 views

If the solar system is nearly flat, then why don't all the planets appear to lie on the same axis when viewed from earth?

For instance, consider the image below. The location of the planets seem to be so random relative to Earth. If the solar system was indeed flat, then I would expect the planets to lie on the same '...
25
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5answers
6k views

Why is the observable Universe larger than its age would suggest?

The age of the Universe is estimated at 13.8 billion years, and current theory states nothing can exceed the speed of light, which can lead to the incorrect conclusion that the universe can't have a ...
2
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1answer
148 views

Precision in the measurement of the distance to the Sun

How precisely can the distance to the Sun be measured? Wikipedia says the distance to the Moon can be measured upto millimeter precision. But Wikipedia article on distance to the Sun says only about ...
3
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0answers
53 views

How much (more or less) of the moon will be visible as it recedes from the Earth?

The Moon is receding from the Earth, at a rate of about 4 cm per year. We can currently see about 59% of the Moon's surface, from the Earth's surface. Will the amount of the Moon's surface we can see ...
1
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1answer
64 views

How does a cross dispersed spectrum look like in a reality (from echelle spectrographs)?

I am an analytical chemist with some interest in amateur spectroscopy. Since astronomers use echelle spectrographs to study the high resolution spectrum of the stars, someone suggested to post the ...
0
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0answers
13 views

What was the energy/wavelength/frequency of the CMB when first emitted/released?

Given the z redshift of 1089, and the temperature difference between then and now of about 1089, I tried scaling the ev, freq. and wavelength by 1089.... Is that right? I get a freq. of about 240 ...
11
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2answers
1k views

Shouldn't tidal locking be impossible for a satellite that has a considerably eccentric orbit?

This popped up into my mind just now. The Moon is tidally locked to Earth, and also has a significantly eccentric orbit. This means that its orbital velocity near periapsis is considerably faster than ...
10
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3answers
2k views

Compute Planet's Apparent Visual Magnitude

In a hypothetical solar system there exist: a sun of radius $r_s$ and absolute visual magnitude $V$ the Earth, with radius $r_e$ and distance from the sun of $1\,AU$ another planet, wit radius $r_p$, ...
0
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1answer
51 views

360 degree image of the whole sky

I look for an image that I know exists. It is an image showing the whole sky, showing all stars and galaxies bright enough to be visible at the resolution, projected to the same shape that is commonly ...
4
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4answers
4k views

Is it possible to be 'still' in space?

So I was reading this answer about how galaxies are the fastest moving objects in the universe because space is expanding faster than the speed of light. This got me wondering, would it be possible to ...
1
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1answer
41 views

Picking two random points in space and drawing a line between them, what is the chance the line intersects anything?

I thought of this question after pondering how most of the observable universe is observable. If we can observe it, then the space between us and that object must have been unoccupied to allow the ...
1
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1answer
46 views

Timekeeping on other celestial bodies than Earth

I have looked for months for any site capable of calculating solar altitude w.r.t an observer located on the surface of a generic celestial bodies, but with no luck as of now. Even NASA does not ...
14
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2answers
1k views

Does blackhole merging break their event horizon segregation?

So far as I know, if we have 2 blackholes A and B, both having their own event horizons, then what's inside the event horizon of A remains completely unknown to us, and same for what's inside the ...
4
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2answers
486 views

What is meant by “vastness of space, which now filled a volume of a hundred million light years”?

I am reading the book Cosmic biology: How life could evolve on other worlds (citation below) and do not understand the meaning of the following paragraph from page 4 (emphasis mine): It took 200,000 ...
3
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1answer
30 views

How can I calculate the uncertainties in magnitude like the CDS does?

When you check an entry of the Gaia DR2 stellar catalogue in Vizier, for example this one, you can see that there is a value for the G magnitude (in our case 18.0733 mag) and a value for the ...
3
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1answer
49 views

Black Hole - energy and matter

Can someone explain what is happening with energy (e.g. light) and matter which was collected by a black hole? I suppose that matter builds a black hole's mass and size, but what about light? Does it ...
3
votes
3answers
87 views

Impact on the rest of the solar system if Mercury or Venus were disassembled?

I've watched a few theoretical videos about Dyson spheres where they mention that the most practical way to do that would be to disassemble a planet - preferably one already close to the sun - Mercury ...
0
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1answer
82 views

how long a light year on earth will seem [closed]

First of all, sorry if this is not the right StackExchange to ask this question, but i don't know a better place (open to suggestion in case). So, the question: Suppose that for some reason, we can ...
8
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2answers
2k views

Where is the Perseids meteor shower coming from?

Swift–Tuttle Comet has orbital period of 133.28 years. Yet, people say that debris and dust from this comet causes this meteor shower. This does not make any sense. Or do they want to say that from ...
3
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2answers
191 views

Are all solutions of the 3-body problem restricted to 2 dimensions?

I am not a physicist. Suppose there are two massive bodies orbiting each other. Their orbit will presumably define a plane. As far as I know, the existing solutions to the 3-body problem are limited ...
-2
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0answers
29 views

Problem 7- chapter 13 of the Astronomy Principle and practice.-Calculate the radius of Venus

Well, this is one of the exercises from chapter 13 of the Astronomy Principle and Practice, which using Kepler's Laws to solve it. But if there are other ways to solve that would be great. Thank you!
2
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1answer
98 views

Comprehensible full manual for bolometric light curve reconstruction

Could anyone point me to some manual or tutorial, possibly step-by-step one, on reconstruction of (quasi-) bolometric light curve using UBVRI-photometry data? Both links and names are fine for me.

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