HOW DO WE DETECT BLACK HOLES? CURIOSITY STREAMER

HOW WE DETECT BLACK HOLES?

A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it.The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.

so it become clear that even light cannot escape from black holes that is than how researcher detect black holes in space ?

these are the following ways in which we detect the presence of black holes

• wobbling effect of object around black hole
• gravitational lens effect
• emitted radiation                          

WOBBLING EFFECT

every black hole has objects around it , by looking the behavior of object we can detect the presence of black hole.

we can also measure the movement of object around the suspected black hole and calculate the mass of black hole.

this is the most used technique to measure mass of black holes.

When a star or a disk of gas that is behaving as though there were a large mass nearby. For example, if a visible star or disk of gas has a "wobbling" motion or spinning and there is no  visible reason for this motion and the invisible reason has an effect that appears to be caused by an object with a mass greater than three solar masses (greater then a neutron star), then it is possible that a black hole is causing the motion. You then estimate the mass of the black hole by looking at the effect it has on the visible object like star or a disk of gas. 

For example

image source : L. Ferrarese (Johns Hopkins University) and NASA/ESA

in the core of galaxy NGC 4261, there is a brown, spiral-shaped disk that is rotating. The disk is about the size of our solar system, but weighs 1.2 billion times as much as the sun. Such a huge mass for a disk might indicate that a black hole is present within the disk.

 

GRAVITATIONAL LESING EFFECT

Gravity Lens

     gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. This effect is known as gravitational lensing.

    Einstein's General Theory of Relativity predicted that gravity could bend space.
This was later confirmed during a solar eclipse when a star's position was measured before, during and after the eclipse. The star's position shifted because the light from the star was bent by the sun's gravity. Therefore, an object with immense gravity (like a galaxy or black hole) between the Earth and a distant object could bend the light from the distant object into a focus, much like a lens can. This effect can be seen in the image below.
                                                                  

image source: hubblesite.org

   In the above image, the brightening of MACHO-96-BL5 happened when a gravitational lens passed between it and the Earth. When the Hubble Space Telescope looked at the object, it saw two images of the object close together, which indicated a gravitational lens effect. The intervening object was unseen. Therefore, it was concluded that a black hole had passed between Earth and the object.

EMITTED RADIATION

 As the core of the black hole is super heated and it is intense gravity it can easily attracts all the objects in to it, even the photons.

When material falls into a black hole from a companion star or any other objects such as supernova, it gets heated to millions of degrees Kelvin and accelerated. The super heated materials emit X-rays, which can be detected by X-ray telescopes such as the orbiting Chandra x ray observatory. these x rays particles are know as hawking radiation. it was discovered by stephen hawking.  

In addition to X-rays, black holes can also eject materials at high speeds to form jets. Many galaxies have been observed with such jets. Currently, it is thought that these galaxies have supermassive black holes (billions of solar masses) at their centers that produce the jets as well as strong radio emissions. One such example is the galaxy M87 as shown below:

                                                                             

image source:Tod R. Lauer (NOAO), Sandra M. Faber (CSC), C. Roger Lynds (NOAO), and the Wide Field/Planetary Camera Imaging Team.

Relativistic jets are beams of ionised matter accelerated close to the speed of light. Most have been observationally associated with central black holes of some active galaxies, radio galaxies or quasars, and also by galactic stellar black holes, neutron stars or pulsars.

It is important to remember that black holes are not cosmic vacuum cleaners -- they will not consume everything. So although we cannot see black holes, there is indirect evidence that they exist. They have been associated with time travel and worm holes and remain fascinating objects in the universe. so it is come to clear that black holes are not pure black body. 

image source: NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)

                                                                                                                                                  The star Cygnus X-1 is a strong X-ray source and is considered to be a good candidate for a black hole. As pictured above, stellar winds from the companion star, HDE 226868, blow material onto the accretion disk surrounding the black hole. As this material falls into the black hole, it emits X-rays.

but also researchers claims that:

Gravitational waves helping to expose black holes, dark matter and theoretical particles

FIRST IMAGE OF BLACK HOLE 

                     

we come to know more about hawking radiation on up comming articles:)