How do astronomers detect neutrinos?

Answer 1

Superkamiokande, or Super-K, is a neutrino detector built into an abandoned mine in Japan. It is a huge tank of ultra pure water, around which are arranged thousands and thousands of photomultiplier tubes. Most neutrinos will pass through the entire mass of the earth like light through clear glass, but a few will interact with the water, producing a flash of light. The photomultiplier detects these subatomic particle interaction light flashes, and that is how we detect neutrinos. The Super-K has an inner set of photomultiplier tubes to help us determine the direction from which the neutrino came.

The main purpose of the Super-K was to discover the proton half life. This experiment established that the half life (if it exists) must be greater than 6.6 x 10^33 years. Next we'll build an even bigger detector, the Hyper-K, in the hopes of deriving an answer to this question.

Answer 2

Seeing objects that don't reflect light is tricky business. And black holes are as mysterious as a target can be. Not even light can escape them. This is a pretty tricky problem for scientists, whose instruments usually rely on light-- whether it's visible light, radio waves, X-rays or infrared-- to observe objects in space.

One method to see black holes has been to watch the fate of an object falling into one of these cosmic graves. If material actually falls into a black hole, it gets shredded apart and it heats up. As it heats up, it starts emitting light and this radiation we can observe. In particular, we can often see X-rays coming from black holes. When gas orbits around a black hole it tends to get very hot because of friction. It starts emitting X-rays and radio waves. So a lot of times black holes can be found and studied by looking for bright sources of X-rays and radio waves in the sky.

These X-rays do not get through the Earth's atmosphere and can only be seen with telescopes positioned in space, such as the Hubble telescope.

The strong gravitational attraction of a black hole affects the motion of nearby objects. When astronomers see a star circling around something, but they cannot see what that something is, they may suspect it is a black hole. Astronomers can even figure the mass of a black hole by measuring the mass of the star and its speed. The same kind of calculation can be done with black holes at the center of many galaxies, including our own galaxy, the Milky Way. In fact, at the very center of our galaxy, radio and X-ray telescopes have detected a powerful source called 'Sagittarius A', identified as this massive black hole.

Answer 3

Since black holes allow nothing including light to escape, detection needs to be indirect. Common methods to detect black holes include the observation of the effects of their gravity upon nearby objects; such a technique was used to interpret compelling evidence of the presence of the supermassive black hole at the Milky Way's center, and included measurements of the orbital period and distance from the source of gravitational pull. Another method is the detection of a characteristic signature of radiation emitted by matter falling into the black hole. Their presence can also be inferred from the radiation created by the accretion disk and the polar relativistic jets in some circumstances. Gravitational lensing may also indicate the presence of a black hole although other possible causes would need to be eliminated, such as the presence of intervening dark matter. Gamma ray bursts may also indicate the birth of a black hole, and also searches are underway for emergy emissions possibly associated with their death.

Often the gathering of a scientific consensus regarding the presence of a black hole can only be achieved with prolonged observation.

Answer 4

Dark matter, just like it's the name suggests, cannot be seen directly. It is detected through its interaction with "regular" matter such as the orbital rate of a galaxy.

Answer 5

Dark matter can't be seen directly, but its presence can be detected by observing its gravitational effects on visible matter.