Neutron stars are the remnants of explosions of supernovae. Neutron stars are most dense in the universe so these are quite small in size. For example the size of London. They are so dense that a spoonful of neutrons weighs as much as 100 000 Eiffel towers.
It so happens that when two neutron stars approach each other, they turn faster and faster generating the gravitational waves by modifying the space-time around them. Ultimately they collide and fuse. After this the eject lots of matter.
How such events in occuring in the universe are detected? Electromagnetic rays emitted during such an event in the form of visible and invisible energy waves can be tracked by the modern telescopes and spectrometry.
Another technique has been added and it measures the gravitational waves which are generated in such violent events involving massive bodies. Such instruments has been installed in US. Called LIGO (Laser interferometer Gravitational-Wave Observatory) can record the gravitational waves.
One such event of fusion of two neutron stars happened 130 million years ago. The gravitational ripples were detected by LIGO on August 17 at 1241 GMT for 100 seconds. Then after 2 seconds a Gamma rays burst was observed. After hours and days following the event, X-rays, UV rays and infrared rays were detected.
This is the first successful observation of fusion of two neutron stars through Gravitational Waves and as well as through different kind of rays that are emitted.
It also confirmed the premise that gravitational waves travel with speed equal to that of light. This event was made possible with the collaboration of 3674 scientists from 953 institutions all around the world.
Atoms are the smallest units of matter which are independent and have a definite address. Atoms of different elements are different in many aspects but size and atomic weight are the main attributes. I think there is no such thing as color of things. Color exists only when there is light.When the darkness falls, the color of things begins to dissolve and black color takes over everything. Black color thus obliterate all the differences due to colors. May be this is the reason why in Hindu mythology many Gods are dark complexioned. Take for example Rama, Krishna and Draupadi, all of them are dark in complexion. Although it is strange to explain why so many of Hindus prefer the fair color. So how can a thing have red color and black color at two instances of time? Light a bulb and again colors come back but there is different between the colors of things in different kinds of lights.
Sunlight is a mixture of many colors which are different waves. All the waves are the part of what is called light spectrum. Our eyes can see limited spectrum of light called visible spectrum which is from violet to red. Violet and beyond region called ultra violet have higher energy. On the opposite end is the red color and lower energy infra red. Birds and bees are endowed with more complex eyes and are capable of seeing into the infrared and ultra violet ranges also. The plants have exploited this capability and deposit substances on the flower strategically on flowers so that bees reach the target directly.
Our eyes have light receptors called cones and rods. They gather light from the target and send to the brain for generating a composite picture. The rods are more numerous than cones. The rods are meant for collecting the faint lights and operate when the light is dim like the sailors panning the stars in sky or when we are out in remote village on a clear night. Due to the plenty of light during the nights also these days, the services of the rods are seldom impressed upon. Now the main role is played by the cones. It is not known why these rods have not been traded with cones during the evolution.
When the light falls upon a substance, different energy centers in the substance become excited. These centers are electrons, atoms or molecules rotation, vibration of atoms joined with different kinds of bonds like single, double or triple. Depending upon the available spectrum of rays falling on the substance, those matching these centers are absorbed. This match is very much defined depending on the structure of the molecules.
From the visible spectrum, some of the wave length rays are absorbed. Those which does not match any center is not absorbed and reflected back. This is the color which reaches our eye and is responsible for the color which we attribute to the substance.
Most of the optical analytical instruments use monochromatic light beams to shine on the atoms and molecules. Monochromatic light is pure light beam of single energy and generally matches a particular wavelength emitted by an excited atoms of single elements. Thus they are able to determine the concentration of a particular element in a solution.