https://preview.redd.it/yy371bttyicd1.png?width=2864&format=png&auto=webp&s=5c4772c1cc0b1464f97f05a4de968f8c38e69b65

After I drew all this in here I thought this sub would be a good place to post it.

I've heard plenty of good things about this book and have wanted to get to it for a long while now. However, I'm not in the US and I haven't managed to find a single place where it can be purchased as an ebook or a pdf. I have no idea where else to search or whom to ask. Thank you in advance for any help you could provide!

Apparently I can’t reply to comments on this subreddit, so here’s a quick edit of what would be my response to one of the comments and probably some others that are yet to appear:

Yeah, I’ve found the 3rd edition in multiple places now, but I’m specifically looking for the updated 4th. Thank you, nonetheless

Have you heard about T Coronae Borealis (TCrB)? No? Well no surprise since this binary star is very, very faint and not visible to the naked eye... YET.

Every 60 years the white dwarf of this binary star system accumulates enough hydrogen from its red giant companion to spark nuclear fusion on its surface. A Nova occurs, releasing large amount of energy. Sice this Nova is "kinda close by" the brightness increased to "naked eye visibility".

But where is the TCrB? Well of course one can use Stellarium, but using Python and some self coding is a great way to understand how these coordinates are computed and displayed.

Thus I created a small Python script + tutorial to create the following red-eye friendly sky map; where the white "+" is the position of the star.

https://preview.redd.it/e6pc0wlwybcd1.png?width=713&format=png&auto=webp&s=9a85c717130af32d28586dad7d2a24888cfcc50c

But WHEN is it happening?

Well... noone really knows. Potentially in the next weeks / months. So keep your eye up :)

YouTube Link: https://youtu.be/ocklQipgPEY

Cheers,

Thomas

I was thinking of things are gravitationally warping space and causing double images or other warping. It got me thinking about the CMB and its use for a lot of research. What I’m wondering is how accurate is the standard CMB images and results when accounting for gravitational warping?

Any idea how to fix this?

Hello everyone, I've always loved stargazing and astronomy ever since I was a kid and I decided to step it up a notch by buying a telescope for the first time, now my budget is a little low so I can't afford high end ones, I wanna view planets like Jupiter, the moon, Mars and etc but I don't know what the right specs are, do you guys recommend that telescope for me and if you could also tell me what I can see with it? The specs are the following: Objective diameter:50mm Focal length:600mm (F12) Tube size and weight: (OD)52mm x (L)580mm , 435 g (15.35 oz) Finder scope:5x20mm Visual back:31.7mm (use the diagonal mirror together) Magnification:60x, 30x Accessories: PL10 and PL20 eye pieces, diagonal mirror, accessory tray

References:

365.242189669781 days is the average length of a tropical year. (https://adsabs.harvard.edu/full/1991JRASC..85..121B)

Calendar Rules:

1. A year is 365 days long.
2. Once every 4 years add a day.
3. Once every 168 years deduct a day. (begins on 2184AD (168*13))
4. Once every 572 years deduct a day. (begins on 2288AD (572*3))
5. Once every 9116 years deduct a day. (begins on 9116AD (9116*1))
6. If rules conflict to create years not 365 or 366 days long (less), then leap years adjacent to those conflicted years are also selected to be deducted from instead in order to maintain 365 or 366 days long years. (The year 24,024AD for example would of had 2 days deducted, so the year 24020AD and the year 24024AD both have a day deducted instead. As for the year 54750696AD would have had 3 days deducted, respectively 54750692AD, 54750696AD, and 54750700AD then have a day deducted as the candidate leap years.)

The proof: (an average calendar year length based on the rules is obtained by converting the rules’ years altered into days difference throughout each year)

1. 365. (see Rule 1)
2. (365*4+1)/4 = 365.25. (see Rule 2)
3. -1/168 or -0.005952380952381 = 365.2440476190476. (see Rule 3)
4. -1/572 or -0.001748251748252 = 365.2422993672994. (see Rule 4)
5. -1/9116 or -0.00010969723563 = 365.2421896700637. (see Rule 5).

To calculate the error and given accuracy:

365.2421896700637 days (calendar calculation) - 365.242189669781 days (mean tropical year length) = 0.000000000282738 days

1/0.000000000282738 days (how long it takes to reach a full day throughout the difference of each year passing) = 3,536,843,296.6209 years until a full day is reached.

There is an error of a day around every 3,536,843,296.6209 years. (About 3 and a half billion years.)

Visual perspective of difference between calendar calculation and mean tropical year length:

365.242189669781 = True Mean Year 365.2421896700637 = Calendar Year

Thank you Reddit for your time and hope this reaches people that can have this replace the Gregorian calendar. It wasn't easy to find.

Gaofen 11 [Bright - Solid]

Sirius FM6 Tk [Faint - Solid]

Cosmos 1048 r [Faint - Solid]

FIA Radar 3 r [Bright - Variable]

Starlink-3591 [Extremely Faint - Solid]

Cosmos 249 [Bright - Flare]

Landsat 4 [Bright - Flashing]

ISS [Ultra Bright - Solid]

SkyTerra 1 Tnk [Extremely Faint - Solid]

IRS 1A r [Faint - Solid]

Noss 2-2 (D) [Bright - Variable]

USA 245 [Ultra Bright - Flare]

OV1-10 X-258Rk [Semi Bright - Variable]

ONEWEB-0501 [Almost Undetectable - Solid]

Cosmos 220 r [Bright - Solid]

DMSP B5A1 Rk [Faint - Solid]

Glonss BrzTank [Bright - Variable]

Landsat 5 [Bright - Solid]

Starlink 1586 [Bright - Solid]

Seasat [Faint - Solid]

CZ-2C R/B [Bright - Solid]

Starlink-3458 [Bright - Solid]

Asnaro [Faint - Solid]

Meteor 1-14 [Bright - Flare]

So, this is an idea I came up with while trying to determine the "optimal" solution to Venutian terraforming. Theoretically, it slowly replaces its thick CO2 atmosphere with oxygen and water vapor. As with any thought experiment, there are a number of assumptions that need to be made for this to work. The process is as follows:

1. A harvesting mechanism would orbit a Jovian planet and harvest the hydrogen the collects in the upper atmosphere. (This mechanism would need some way to offset the force of atmospheric friction. Perhaps a fusion rocket that can use said hydrogen as fuel?)

2. This hydrogen could then be mass-driven to Venus for processing.

3. The hydrogen arrives at Venus, and a fraction of it is used to power a MOXIE facility. Again, this operates on the theory that the hydrogen is a workable fusion fuel.

4. Part of the released oxygen is combined with the hydrogen in a fuel cell to create water vapor.

5. The waste carbon can be used to create additional transportation vessels for the hydrogen that can be mass-driven back to the Jovian planet (if necessary). Whether the original container is re-used or a new container is generated, a replacement will need to be sent to our theoretical Jovian planet.

So, where does this land on a scale of "absolutely impossible" to "theoretically possible, with caveats"?

What do we think guys?

1. Has sufficient mass for its gravity to overcome rigid body forces so that it assumes a nearly round shape (in hydrostatic equilibrium).

2. Directly orbits a star¹, stellar remnant², or the barycenter of a star system³, or is part of a system where the combined barycenter of the system directly orbits a star or stellar remnant⁴, or has been ejected from such a system⁵.

3. Is not massive enough to initiate thermonuclear fusion in its core.

Which would mean we have the following 14 planets:

• Mercury
• Venus
• Earth
• Mars
• Ceres
• Jupiter
• Saturn
• Uranus
• Neptune
• Pluto
• Charon (orbiting the same barycenter as Pluto)
• Haumea
• Makemake
• Eris

¹ like Earth ² could orbit a white dwarf or something ³ allows for systems with more than one stellar mass object ⁴ like Pluto-Charon ⁵ allows for rogue planets

Regarding our observation of GNZ11, I understand that we are seeing light that left the galaxy 13.4 billion years ago, and that due to the expansion of space it is now 32 billion lightyears away.

What I don't understand is how the light that we're seeing has travelled 13.4 billion light years in 13.4 billion years. Wouldn't the expansion of space between the earth and GNZ11 cause it to take longer reach us?

Say for example I'm driving a car at exactly 100mph along a road that is exactly 100 miles long. It would take me 1 hour to cross it, but if the road was expanding it would take me longer than an hour to cross it. Does this not happen to light travelling through expanding space?

Not sure if this post is allowed, but it’s a big milestone- sad to leave somewhere I spent five wonderful years, but excited to start my next chapter as a professor at the University of Oregon!

Fun fact- that dome behind me contains the Great Refractor, which was the biggest telescope in the world in the 1800s and discovered several moons of Saturn.

Apparently, due to the incredibly far distance between stars, it is highly unlikely (but never zero) that (if) any stars collide.

Spotted outside of Rapid City SD at 8:41 pm MST to the east. Appeared stationary in the sky and was still too light out to see any other stars or planets in the sky. Image taken by my brother’s iPhone through a 40 power spotting scope used for hunting. Have video as well if there’s interest.

Hello! I’m a high school student and I LOVEEEE outerspace. I’ve often thought of astrophysics as what I wanted to do but when I looked into it I discovered that often careers ended with being a professor at a university. I’m not really interested in that. I really want to conduct research, and while I wouldn’t mind working partly as a teacher and partly as a researcher, I definitely know I’m not interested in working as JUST a teacher.

How reasonable is it to go into this field without wanting a purely teaching position? I do love many aspects of science so would it be possible to find jobs in other aspects of physics and science until I found an astrophysics research position? Also: In general, how long can astrophysics research positions be?

All advice is appreciated!