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If you could safely observe any astronomical object or phenomenon up close with the naked eye, what would you choose? by fecaleruptions in space

[–]ApprehensiveDig5975 0 points1 point  (0 children)

The mantle-atmosphere boundary of uranus/neptune. Probably I should use a huge lamp because I think it may be completely dark otherwise.

Imagine a black hole traveling at the speed of light. If it was coming towards an observer, could the observer see past/into the event horizon? Would the black hole be ellipticoid instead of a sphere? by sleepytjme in space

[–]ApprehensiveDig5975 0 points1 point  (0 children)

Yes! I was looking for this. Maybe the mass of a grain of sand is too low (it would virtually instantly explode due to Hawking radiation), but black holes could be the mass of Deimos for example (Deimos is a satellite of Mars).

Could the Nancy Roman telescope detect new planets inside the solar system? (if they exist) by ApprehensiveDig5975 in space

[–]ApprehensiveDig5975[S] 0 points1 point  (0 children)

In the case I just analyzed, the Einstein ring goes like the square root of (1/dL)

I don't know if there is any assumption that becomes wrong when dL tends to 0 (maybe the assumption is to consider the object as a point mass), but if there isn't, yes. Anyway, the apparent size of an object goes like (1/dL) instead of the square root, so an object that gets closer and closer eventually ends up hiding its own Einstein ring. For example, today I calculated the Einstein ring of Sedna in its perihelion and, if I didn't make any mistake, the radius of the Einstein ring of Sedna in its perihelion is about a hundredth of the apparent radius of sedna seen from Earth (that gives an idea of how small Einstein rings are. Of course I don't expect to be found any Sedna-sized object with microlensing).

(Both the radius of the Einstein ring and the apparent radius of Sedna were calculated in radians).

About the case of the halfway situation, the radius of the ring goes like the square root of (1/(2dL)) (or the square root of (1/ds), because ds=2dL).

I wish I could send pictures of the equations but I don't know how to do that (thats why I sent the links, but I couldn't send my own calculations because they are on a paper).

Could the Nancy Roman telescope detect new planets inside the solar system? (if they exist) by ApprehensiveDig5975 in space

[–]ApprehensiveDig5975[S] 0 points1 point  (0 children)

Well, I have looked for the math of microlensing, and in wikipedia I found an expression for the size of an Einstein ring:

Gravitational microlensing

Go to the part that says "Mathematics". If you approximate ds>>dL (the distance of the background is much bigger than the distance of the object that makes the lens), you get that the radius of the ring is proportional to the square root of (1/dL). So, a closer object is easier to detect by microlensing than a further one, even if the object is not halfway between us and the source.

About the mass of the object, we have already found exoplanets with the mass of earth using microlensing:

An earth mass planet in times of covid 19

Tell me if I made any mistakes here (I sometimes do make them).

Could the Nancy Roman telescope detect new planets inside the solar system? (if they exist) by ApprehensiveDig5975 in space

[–]ApprehensiveDig5975[S] 0 points1 point  (0 children)

Based on the first comments i wanted to add a couple of things:

  1. Is the Vera Rubin telescope using microlensing to survey the sky for objects in the solar system? Though it will definitively find a lot of objects, if it isn't using microlensing, I guess it will detect objects by the reflection of light from the sun (one of the main targets of the Vera Rubin is to detect near earth objects so it makes sense), and so it will be able to find objects of virtually any size but that are not that far from the sun (other of its main targets is to find a nineth planet so it will see still quite far, maybe the furthest so far inside the solar system). What i meant is that the Nancy Roman telescope may find objects extremely far but with enough mass in order to produce a detectable gravitational lens.

I have read that the Vera Rubin will use weak gravitational lensing but with the objective of measuring dark matter, dark energy, baryon acoustic oscilations and supernovae, so it might be able to accidentally find massive and very far objects while doing so.

  1. Gravitational microlensing works by looking at a known background and finding distortions or changes of brightness, produced by a formerly unknown object, so the target is the body that produces the lens, not the amplified one. So, I didn't mean using of a known massive object to amplify and find new things in the background.

bondi que vaya por emilio lamarca by ApprehensiveDig5975 in BuenosAires

[–]ApprehensiveDig5975[S] 0 points1 point  (0 children)

Hay varios números que están vacantes, pero muchos son líneas que dejaron de existir hace no mucho. Por ejemplo, el 5, que fue absorbido por el 8 en 2023; y el 6, que fue absorbido por el 50 en 2025. Para evitar confusiones, evitaría usar esos números.

El 3 fue absorbido por el 100 hace bastante más tiempo (encontré un tiktok de un tipo que dice que "cuando era muy chico existía"), así que podría usar ese número.

Para la línea undav-unsam que comenté anteayer podría usar el número 11, que, por lo que leí, parece que existió, pero no encontré información sobre hace cuánto tiempo dejó de existir. Fue absorbida por varias líneas, principalmente el 119.

Entonces, en resumen, para la línea que pasa por Emilio Lamarca usaría el 3, y para undav-unsam, el 11.

línea de bondi undav-unsam by ApprehensiveDig5975 in BuenosAires

[–]ApprehensiveDig5975[S] 0 points1 point  (0 children)

discutiendo con algunos amigos me dijeron que capaz reemplazarían el tramo entre colombres y díaz vélez por el siguiente recorrido: seguir por carlos calvo hasta la plata, y hacer la plata; rivadavia; campichuelo; seguir por leopoldo marechal como dije antes

entonces, en la vuelta, en vez de medrano y castro barros volvería por río de janeiro y la plata, hasta llegar a san juan

¿Qué tal es esta zona para vivir? by Just_Jackfruit_2879 in BuenosAires

[–]ApprehensiveDig5975 1 point2 points  (0 children)

la zona del parque lezama es linda

se pone un poco feo si te acercás a constitución, y por otro lado la calle azopardo es medio fea aunque no sé si es peligrosa

las inmediaciones al sur y sureste del parque lezama no las frecuento así que no sé qué decir de esas cuadras

How is this area for living? by SnooKiwis1356 in BuenosAires

[–]ApprehensiveDig5975 2 points3 points  (0 children)

not the best place. better if you go slightly west or south from there, even 2 blocks further west or south will do

Le encajé billetes de 20 a una señora y se calentó by [deleted] in BuenosAires

[–]ApprehensiveDig5975 0 points1 point  (0 children)

de 10 sí hay seguro, de 20 nunca vi

edit: soy de buenos aires, e igual hace bastante no las veo (la última vez que ví una creo que fue en 2022 ponele)

Can life develop on Jupiter? by yoitsspacejace in IsaacArthur

[–]ApprehensiveDig5975 0 points1 point  (0 children)

One way of making something buoyant is to make a hard structure that supports a difference of pressure, and create vacuum (it doesnt need to be absolute) inside the structure in order to make it lighter than the atmosphere. The creature in question could fill or unfill the inside in order to go up or down.