Circa 2023 Astro Physics Discoveries (v1.1)

Some of the hardest questions in Physics are: 

1. Why are we made of matter and not antimatter? (Scientists think neutrinos have something to do with this)

2. Can we glimpse even closer to the big bang event? (Scientists thinks gravity waves may provide insights on this)

3. Why is the universes expansion accelerating? (Scientists think it is because of dark energy)

4. Why is there so much matter in the universe that we can't see or detect except indirectly through gravitational effects? (Scientists think it is because of dark matter)

Two huge discoveries in astrophysics were published lately that are fascinating and are steps towards answers. One new space telescope launch also looks promising to provide some answers. 

A Neutrino is believed to be a vital ingredient in a star's supernova process. They are also a biproduct of nuclear fusion. They are one of the universe's essential ingredients, and they have played a role in helping scientists understand some of the most fundamental questions in physics. It's very tiny bit of mass may explain why the universe is made up of matter, not antimatter. Early in the process of the Big Bang, there were equal amounts of matter and antimatter, but as the universe expanded and cooled, in the quark epoch (10^{-12} to 10^{-6} seconds after the big bang), matter and antimatter were mostly annihilated. And a slight asymmetry favored matter over antimatter. Scientists think neutrinos may have something to do with that process and asymmetry …. And it’s a puzzle, why we’re made out of matter and not antimatter. Scientists want to understand neutrinos better. 

Neutrinos are called ghost particles. It can go through a whole galaxy without being affected in any way. It is uncharged and almost massless and travels close to the speed of light. At any second there are likely billions of neutrino particles going through you. Almost all of them that fall on earth just go through it. However, neutrinos all so very slightly interact with ice. In contrast, cosmic rays are high energy heavier subatomic particles travelling close to the speed of light and have been blamed for electronic problems in satellites and other machinery. Neutrinos are of three types: electron neutrino, muon neutrino and tau neutrino. 

 The biggest neutrino detector on this earth is in the South Pole and is called Ice Cube. A large block of ice 1.5 miles underground and a total of one cubic kilometer acts as the detector. There are 86 boreholes with sensors that surround it that detect any neutrino that interacts with the ice. It detects about 100,000 neutrinos a year. When they interact, a streak is detected and from its characteristics you can deduce which part of the sky they came from.

 Using machine learning, researchers have assembled this data to plot neutrinos from the Milky Way. They have drawn a picture from the analysis of the neutrino sources in the Milky Way. This is the very first neutrino picture of the Milky Way rendered in visible light by an artist so we can see it. 

Another discovery is gravity waves. According to general relativity, when two black holes spiral in towards each other and merge, the resulting gravitational-wave signal – or general relativity waveform – has a characteristic profile that, as time passes, increases in frequency and amplitude until they peak.

While gravity waves were first detected in 2015 using laser Interferometers, a very recent discovery and confirmation is that there is a continuous background of such gravity waves that constantly ripple through space-time. This was proven by multiple independent studies by observing many pulsars, (which pulse with almost the precision of an atomic clock and are really rapidly spinning neutron stars). Minute changes in arrival rate of pulses measured over years could only be due to a continuous background of gravity waves being ever present. Tiny discrepancies might be because of individual stellar idiosyncrasies or could be a sign that gravitational waves have changed the distance each pulse travels on its way to us. By monitoring dozens of pulsars, astronomers hunt for correlations in timing errors that are a smoking gun of passing gravitational waves. And that’s just what they found. Next step is to evaluate different types of gravity waves and try to assign specific sources for specific ones. It opens up a whole new discipline in physics. 

The biggest gravity wave detectors on earth uses laser interferometry and these detectors are gigantic and marvels of engineering. They use two, kilometers-long tubes at right angles. LIGO in US, the most sensitive detector uses 4 km long arms, and it has two such detectors 3000 km apart. Lasers are sent in both directions and reflected back. If they cancel each other out at the point of origin, then there was no disturbance. IF not, gravity waves made one slightly shorter than the other. For example, when LIGO detected gravity waves in 2015, the difference was a fraction of a proton size!! The next iteration in technology is space-based interferometry like LISA. But the pulser approach used recently is a whole new approach.  

There is a more intriguing possibility than colliding black hole pairs for gravity waves. Very early in the universe there was a period of very rapid exponential expansion called inflation that could set space time ringing with gravity waves. Could these background gravity waves detected be echoes of that? The inflation period occurred between 10^{-36} seconds to 10^{-32} seconds after the big bang and the universe expanded from less than the size of an atom to a grapefruit. If so, this is as important a discovery as the cosmic microwave background radiation that was the first tangible proof that the universe started with a big bang and resulted in the birth of cosmology.

 In other news Europe's Euclid space telescope just launched on a SpaceX rocket to be positioned at the L2 sun-earth LaGrange point (like the James Webb space telescope) with a major emphasis to study dark energy and dark matter. It will also make a immense 3D map of the cosmos. It is hypothesized that dark matter is an unknown form of matter that constitutes 85% of the matter in the universe, and dark energy is an unknown form of energy that affects the universe at its largest scales. It is hypothesized that the universe’s expansion is actually accelerating because of dark energy. 

Dark energy, Dark matter, Neutrinos and Gravity waves are all very important research subjects. 

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NEXT: A recent discovery - JUMBOs. (v1.1)

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