Unanswered Questions
238 questions with no upvoted or accepted answers
-6
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Answer this or don't downvote
Otherwise you'll be showing your complete ignorance in the matter and contempt for the truth.
If the scale factor as a function of time represents or is equal to the average distance between the ...
2
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0
answers
32
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Dual mode in SExtractor
I wanted to use SExtractor for source detection. I have 7 NIRCam filter data from the JWST CEERS catalogue. How can i proceed with the source detection. I read about using dual image mode in which a ...
- 51
0
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24
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calculating the color of a galaxy and making the k correction
I want to know if this is correct:
I have in my dataset: $u_{mag}, u_{mag_{err}}, r_{mag}, r_{mag_{err}}$
Calculating the $u_{r_{color}}$:
$u_{r_{color}} = u_{mag} - r_{mag}$
$u_{r_{color_{err}}} = u_{...
- 328
1
vote
0
answers
16
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cross-matched SDSS-WISE catalog
Please where can I find cross-matched SDSS and WISE dataset for a machine learning project?
(Galaxy-star-qso classification task)
2
votes
0
answers
84
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Would we know if the universe was rotating?
I was wondering what we would observe if the universe had a small rotation. My conclusion was that galaxies on the equatorial plane of the universe would be slightly more redshifted than galaxies than ...
- 373
3
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0
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41
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Why MIT's Benjamin Rackham says "nearby ultracool dwarf SPECULOOS-3" would look "purplish-red, spotted, and flaring" from an airless orbiting planet?
May 15, 2024 MIT News article Newly discovered Earth-sized planet may lack an atmosphere includes the following:
“We can say from our spectra and other observations that the star has a temperature of ...
- 30.7k
0
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0
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43
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Finding the algular size of galaxy cluster when given the RA and dec cordinates of all the galaxies in the cluster
I have the RA and dec values of all the galaxies in a cluster and i need to find its angular size i do not know how to calculate it
0
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1
answer
74
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The distribution of mass in the bullet cluster
Can someone point me to a database which contains the luminous and gas mass distribution of the bullet cluster?
- 3,504
0
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0
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35
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Project Analog Hypothetical Planet
For my story Project Analog, I was wondering if a hypothetical planet (Let's call it Suria). It has the same size and conditions as Earth with the same axis, tilt, and rotation, as well as one moon. ...
CommunityBot
- 1
2
votes
0
answers
101
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What would the Big Crunch theoretically look/feel like?
In the Big Crunch theory, the expansion of the universe reverses, resulting in all matter contracting into a single point. Imagine you are alive at the time of this event. What would the sky look like?...
- 29
2
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0
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34
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Local anisotropies in the expansion of the universe and tidal forces...?
In the context of the large-scale structure of the universe, there can be local anisotropies (https://www.aanda.org/articles/aa/full_html/2021/05/aa40296-21/aa40296-21.html).
I understand from this ...
- 1,017
0
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0
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25
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Deriving Faber-Jackson Relation from Milgrom's Law
I am reading Famaey & McGaugh 2011, a review paper on Modified Newtonian Dynamics. My question concerns bullet 3 in Sec 5.2, where the authors try to explain how Faber-Jackson Relation can be ...
- 779
1
vote
0
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121
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Determining Time Based on Arc Seconds
So our arc day starts at 20°41'32 which is midnight (0:00) and ends 24 hours later at 21°42'42. According to my calculations it traveled 0 degrees, 59 minutes, and 30 seconds or 3570 arc seconds in 24 ...
- 2,339
2
votes
0
answers
34
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Baryonic Tully Fisher Relation slope
I'm studying the Baryonic Tully-Fisher relation. In the textbook I'm reading there is written that in order to construct this relation, one needs to derive a stellar mass, obtained for example by ...
- 21
0
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0
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66
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Flux from the Sun on the Earth using the Stefan-Boltzmann law
What is wrong with this computation, plase? I am getting the result of 4291.65 W m^{-2} instead of 1361 W m^{-2}. Thank you very much
...
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