Would a black hole cast a shadow?

Question

Theoretically, if there was a solar system, with a black hole and a planet in orbit, and they aligned so that it was sun--blackhole--planet would the blackhole cast a shadow, or would the gravitational lensing prevent this from happening, and the light would just bend around it, causing no shadow?

So a solar eclipse with a black hole, viewed from a planet, what would be seen?

Answer 1

You have to consider that solar mass black holes are very small about 3 km in radius. Compared to the diameter of the sun that is infinitesimal. Such a black hole would still cast a small shadow but the sun would not be eclipsed. In fact, whether you are going to see a total shadow or not will depend on how far away the black hole is from you. If you are standing sufficiently far away all you will see is a relative darkening in the light from the portion of the sun "eclipsed" by the black hole.
You would also see a distortion in the light crossing close to the black hole, within a few km.
If on the other hand you had a super massive black hole, with radius close to the radius of the sun about 2 x 10^5 solar masses, then the situation will be different. The sun is visually behind the horizon so by all means direct light is eclipsed. However, rays of light approaching tangentially to the horizon would be bend and then depending on your distance from the black hole and the relative sizes of the sun and black hole you may still see light much like the same way when the moon eclipses the sun, although the later is a pure optical effect.
With black holes with even larger masses and therefore radii you still have a non-zero probability than gravitational lensing of the light from the sun behind the BH will reach an observer.

Answer 2

A shadow is the outline of an object caused by light passing around the object and showing on a surface but the light in direct line with the object being blocked by the object and not allowed to pass.

Given that the theory holds that a black hole with bend light towards itself and also that it absorbs all light, it would hold that there would be no available light to cast as shadow. What would the shadow be cast upon?

Mind you, the theory of light being bent toward a black hole and that is the reason that a black hole cannot be seen is very convenient one. It allows the exploration of black holes without the lack of any empirical evidence ever being questioned.

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Answer 3

This is a great question!

Of course it would all depend on the relative sizes and distances of everything. But gravitational lensing would enter into it. The likelihood of everything being placed in the perfect locations to create the illusion of invisibility would be very small. I think the observer would see something distorted. The star could look larger than normal, or smaller, or even inverted, depending on the focal length of the gravity lens. The black hole would be a different size too. It would be extremely interesting to watch it happen. Everything behind and around a black hole looks very distorted.

There's a simulation of what looking at a black hole passing through space here. (Click the "Up Close and Personal" tab)
http://hubblesite.org/explore_astronomy/black_holes/modules.html

Answer 4

If a black hole could exist it would not cast a shadow or eclipse a body that was behind it.
A black hole would have the virtue of containing no space,therefore it's event horizon is merely theoretical.
It could not cause an eclipse.
Since it would be a massive body with gravity it would make itself known by it's influence on another body which would be tugged in different direction as it's location changed.
A black hole is an elegant theoretical entity that cannot exist.

Answer 5

First thing u cant see a black hole coz its gravity is powerfull to suck all radiation from it nearby objects into its horizon,now the shodow casting happens like this when a object is lit with light the area covering up the light will be seen as shadow behind the object but when black hole is lit with light area covering light will cast shadow in top of that light from the surrounding also get pulled into it so the shadow appears larger than actual size of the black hole.

Answer 6

One of the theories concerning black holes is when a dwarf star collapses and soon all of that solar system falls into the hole. Thus in your theoretical scenario the dwarf sun sucks in any planet in that system (as more mass is sucked in the black hole increases in gravity) and so is impossible to occur.

Enter the other possibility of a tiny black hole. If the black hole moves in between the observer and the light source, the shadow that results is no light shining to the observer. The cone of shadow is relative to the closeness of the light source to the black hole. By comparing one cone of shadow to another cone of shadow the relative distances and sizes of the black hole can be determined.

Since the existence of non-dwarf star black holes is theoretical, until we find them all answers are speculative, like my answers.....

Answer 7

Makes you think doesn't it?

My guess is that much would depend on the relative diameters for the sun, the black hole(event horizon) and the distances between Sun, Black Hole and planet.

The umbra would be reduced by gravitational lensing and to see a shadow (on the planet) the planet would have to be in the umbra but outside the event horizon.

Answer 8

think this ties in to what uncle Einstien got his nobel for (not relitivity) think it would depend on the space of the objects to each otherif the planet were close enough or the star small enough then it would be shadowed - just like the moon and earth . now if the star were large enough - say near death giant then possably a planet (doomed though it is) migh have light bent back into it , or if it was far enough back and the black hole not powerfull enough and the star larg enough the black hole even with gravity pulling light might again have light. just like an asteroid between us and the sun realy dosen't eclipse us...

Answer 9

With a black hole there is no gravitational lensing. Gravitational lensing happens when the light can pass through objects; black holes "devour" everything, even light. Black Holes have such a huge gravity that not even light can escape.

Answer 10

I would say no because the force of gravity in a black hole is supposed to outweigh light, meaning the light passed onto the black hole would then be sucked into it thus the 'black'. No light that passed over it would survive therfore no shadow would be cast. The only thing stronger than the power of light is the power of DARK.