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36 questions from the last 30 days
Newest Active Bountied 1 Unanswered
5 votes
2 answers
853 views

79-Year Repeating Cycle in Mars-Deneb Algedi Conjunctions: An Undocumented Pattern? Background I've been analyzing the conjunctions between Mars and the star Deneb Algedi (δ Capricorni, RA = 21h 47m ...
Boanerges's user avatar
  • 31
6 votes
2 answers
1k views

What is the difference between blazars and quasars? Is the classifcation related to the black holes at their centres? What are the relative numbers of each type and do all the known examples have ...
Saleem Akbar's user avatar
  • 106
9 votes
1 answer
1k views

Is there an easy way to calculate how close a star of given mass could get to our solar system without disrupting the orbits of the planets? Just looking for a rough estimate, nothing too involved ...
Darkreaper's user avatar
  • 101
8 votes
3 answers
449 views

Problem I'm trying to complete an assignment for my astronomy course, but I'm having trouble understanding how accuracy is determined when converting equatorial coordinates in sexagesimal format to ...
Atlas's user avatar
  • 183
4 votes
2 answers
1k views

The Earth's axis is tilted at 23.5 degrees. This number is very well known. This describes how far the axis is deflected away from the vector perpendicular to the ecliptic plane. If you drew a ...
TJM's user avatar
  • 387
-1 votes
4 answers
178 views

Here is a real observation of a triple conjonction of Mars during the retrograde loop of Mars : And here's an animation that shows clearly the problem : codepen.io/Boanerges-the-solid/pen/bNewJXQ As ...
Boanerges's user avatar
  • 31
1 vote
2 answers
1k views

Is $dt$ in the Minkowski metric mathematically equivalent to $dt$ in the FLRW metric for spatially flat, expanding universe? I'll be happy with the answer in comment. I already know that the FLRW ...
user avatar
-3 votes
3 answers
165 views

Is dark matter just negative mass? What would it look like? Is it the cosmological constant? Given the below article, I'm assuming DM would repel matter as it is the inverse of gravity (Newtonian) and ...
atod's user avatar
  • 11
4 votes
1 answer
302 views

The scale factor of the universe is defined to be unity now. In terms of this scale factor, the radius of the observable universe is defined as $$ r = \int^{t_0}_0 \frac{c}{a(t)}\ dt\ , $$ where $t_0$ ...
ProfRob's user avatar
  • 174k
3 votes
3 answers
299 views

So I'm totally versed on why the sun is higher in summer and lower in winter for the northern and southern hemispheres, this is because the earth orbits the sun and rotates on its axis at the same ...
Leo Sim's user avatar
  • 39
-1 votes
1 answer
94 views

Predictions can be done using software or manually. I don't understand too much about the methods used by computer software (planetariums etc.) to predict the movements of the planets nor how they are ...
user48495's user avatar
  • 109
-1 votes
1 answer
112 views

I saw an argument on a forum about a fictional moon orbiting a gas giant, with a 24-hour day. Which of these arguments is correct? Or maybe they're all wrong, and this would need something else? Guy A:...
Pointman's user avatar
  • 115
0 votes
1 answer
148 views

https://en.wikipedia.org/wiki/Age_of_the_universe#Cosmological_parameters I have two problems with the "empty universe". If it's completely empty, it can't expand, but its scale factor ...
user avatar
1 vote
2 answers
145 views

I'm new to the site, and yes, I did read through other answers. I'm an amateur photographer and look west from the deck often. Our view looks across the river to the mountains. I do use a tripod and ...
user79896's user avatar
  • 19
2 votes
1 answer
136 views

I've been comparing Mars retrograde motion data from JPL Horizons for the 2003 and 2012 oppositions and noticed something unexpected: 2003 opposition: Earth-Mars distance = 0.373 AU (55.8 Mkm), ...
Boanerges's user avatar
  • 31

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