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5 facts about Johannes Kepler

Firstly, thank you all so much for 100 likes total on my blog! It's so good to see that people are interested about space as much as I am.

So now back to the 5 facts:

Johannes Kepler was a German astronomer who lived from 1571 to 1630, who discovered the laws of planetary motion.

His first law states that planets orbit the Sun in an elliptical motion.

His second law states that the closer a planet comes to the Sun, the faster it moves.

His third law describes the link between a planet's distance from the Sun and its orbital period.

Isaac Newton used Kepler's laws to formulate his theory of gravity.

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The Transformation of the Universe: From the Big Bang to a Cold Death

I really hope you enjoy this, even though it is very long for a blog. I would recommend reading until the end though, because I think the fate of the Universe is the most interesting part :)

THE START OF THE UNIVERSE- AKA THE BIG BANG

The Planck Epoch

Before the Planck Epoch, the universe was just a singularity at the beginning of time. The Planck Epoch is known as the first instant after the Big Bang, and scientists currently don’t know what happened in this period.

The Inflation Epoch

The Inflation Epoch took place from 10^-36 seconds after the big bang, where the universe expanded radically, from billions of times smaller than a proton to something between the size of a marble or a football field. In this period, scientists believe that gravity split from the other forces of nature, followed by the strong nuclear force. This triggered the universe’s short but rapid expansion, and this theory helps explain why the universe is smooth and flat. At this point, an immense amount of mass-energy came into existence, together with an equal, negative amount of gravitational energy.

The Electroweak Epoch

In this Epoch, which occurred 10^-32 seconds after the big bang, huge numbers of quark and antiquark pairs formed from energy, just to annihilate back into energy again when they met. Gluons, and some of the other more exotic particles, also appeared during this period. The universe was thought to be a ‘soup’ of elementary particles and antiparticles at this time.

The Quark Epoch

During this time, starting 10^-12 seconds after the big bang, the electroweak force was separated into the weak force and the electromagnetic force. Only then did physical laws become what they are today. By 10^-6 seconds, the start of the Hadron Epoch, temperatures had dropped to 10^11K, and gluons could bind quarks together.

The Hadron Epoch

In the beginning of this period, vast amounts of quarks and antiquarks had combined to form particles called Hadrons, hence its name. Some types of Hadron particle include baryons (protons and neutrons), antibaryons, and mesons. The antibaryons and mesons, however, quickly decayed or were annihilated after they formed. The protons and neutrons formed during this epoch were done so through  quark confinement, where ‘up’ quarks and ‘down’ quarks combine with gluons and make protons and neutrons. 

The Lepton Epoch

This period in the transformation of the universe starts one second after its formation, when the universe was around 10^10 Kelvin. During the Lepton Epoch, leptons (electrons, neutrinos, and their antimatter particles) were very numerous. The electrons had annihilated with positrons by the end of the epoch.

Big Bang Nucleosynthesis

During Big Bang Nucleosynthesis, collisions between protons and neutrons began forming helium-4 nuclei, and tiny amounts of other atomic nuclei, like helium-3, lithium, and deuterium. These reactions finished within twenty minutes, and by that time, 98% of the helium atoms today had formed.

The Photon Epoch

Throughout the Photon Epoch, which lasted 380,000 years, the electrons, protons, and helium nuclei were constantly interacting with photons, which made the universe foggy.

The Recombination Epoch - 380,000 years after the Big Bang

When the temperature had dropped to around 4000 Kelvin, the protons and atomic nuclei had begun to capture electrons, which formed the first atoms. During this era, the Universe became transparent because electrons had stopped scattering photons after being bound up in atoms, and matter and radiation therefore became ‘decoupled’. The photons were released to travel through the Universe as radiation. The first free photons can actually still be detected as the cosmic microwave background radiation, or CMBR.

THINGS STARTED FORMING

The Aftermath of the Big Bang

When the Universe was 400,000 years old, it was filled with photons of radiation streaming in all directions, and atoms of hydrogen and helium, neutrinos, and other dark matter. Astronomers try and look back into that time, and even though it was around 3,000 degrees celsius and filled with radiation, they see no light. This is because when the Universe expands, it stretches the wavelengths of radiation by 1,000x. We see the photons as cosmic microwave background radiation. Their wavelengths are now that of an object with a temperature of 3 Kelvin.

The First Stars

The first stars are thought to have formed roughly 180 million years after the Big Bang. They were all made of hydrogen and helium, because there weren’t really any other elements in the universe. Physicists think that nebulae that form stars would have condensed into larger clumps than those around today. The stars that formed these clumps would have been extremely hot and large, with masses between 100 and 1,000 times the mass of the sun. Although many of these stars only would have lasted a few million years before dying as supernovae, ultraviolet light from these stars may have actually triggered a key moment in the transformation of the Universe. Either the first stars, or radiation from quasars likely re-ionised hydrogen from a neutral gas to the ionised form seen today. 

Early Galaxies

Astronomers are still trying to determine exactly when in time the very first stars ignited, and what types of galactic structures this could have caused. They have recently used instruments like the Spitzer Space Telescope and the Very Large Telescope to perform infrared studies and hopefully find early galaxies. Amazingly, they found very faint galaxies with very high red-shifts that existed as little as 400 million years after the Big Bang! One of these is GN-Z11, which is the most distant galaxy known. 

Cosmic Chemical Enrichment

The first massive stars created and dispersed new chemical elements into space during the course of their lives and deaths. Elements like carbon, oxygen, silicon, and iron were all formed in the cores of these stars from nuclear fusion, and during the stars’ violent deaths, they formed elements like barium and lead. 

Stars smaller than the first megastars, second- and third- generational stars, formed later from the interstellar medium. They created some of the heavier elements, then returned them to the interstellar medium through stellar winds and supernovae explosions. 

Galactic mergers and the stripping of gas from galaxies led to even more mixing between the galaxies, and these processes even continue today.

This is really important, because without these new heavier elements, living organisms on rocky planets (like us) would not have formed.

THE UNIVERSE’S END

The Big Crunch

The ‘Big Crunch’ theory of the end of the Universe is currently regarded as the least probable of the 4 theories to actually happen, even though it’s the most exciting. According to this theory, all matter and energy will collapse into an infinitely hot, dense singularity, kind of like the Big Bang in reverse. If this were to happen, it would be tens of billions of years from now, so there’s no need to worry about the incredibly painful death this would bring.

The Big Rip

With this theory, the Universe would end with the strength of dark energy increasing so much that it would overcome all the fundamental forces and completely disintegrate the Universe. First, galaxies would be ripped apart, then even planetary systems like ours would be torn away from each other. We would have to say goodbye to any sunlight or warmth ever again and hello to a frozen death, but luckily this won’t happen until 20-30 billion years from now. Even if the theory is correct, we won’t be alive to experience it ourselves.

A Cold Death - The most probable theory

If the Universe were to end with a Cold Death, it would happen with galaxies eventually exhausting the gas that can form new stars, in about a trillion years, or 10^12 years. After this, in about 10^25 years or 10 trillion trillion years, most of the Universe’s matter will be in black holes and burnt-out white dwarfs that circle and fall into the supermassive black holes in the centres of galaxies. Then, in 10^32 years, protons will start to decay into photons, electrons, positrons, and neutrinos, and all matter that isn’t in black holes will fall apart. 10^67 years after that, black holes will start evaporating by emitting particles and radiation, and in about 10^100 years from now, even supermassive black holes can evaporate. The Universe will then be nothing more than a diffuse sea of photons and elemental particles.

Another version of The End which also leads to a Cold Death

In this theory, structures that are not bound by gravity will fly apart faster than the speed of light  if the effects of dark energy continue the way they are now. (Whilst no matter can travel through space at greater than the speed of light, space itself can extend this speed limit). This theory also gets to the same Cold Death as the previous one, it just took a slightly different approach.

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Stephan's Quintet

This galaxy cluster, appearing between 41 and 340 million light years away from us, was first discovered by the French astronomer E. M. Stephan in 1877. The galaxies are a mixture of spirals, barred spirals, and ellipticals. Some scientists think that the largest galaxy in this cluster, NGC 7320, is probably in front of what is really a quartet of interacting galaxies, and since then there have been many discussions between scientists with different theories on what this actually means.

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The Fried Egg Galaxy

The spiral galaxy NGC 7742 is also named the fried egg galaxy because of its core, which is much brighter than would be expected for a galaxy only 36,000 light-years across. This is because the fried egg galaxy is a Seyfert galaxy, and has a moderately active core. The fried egg galaxy, or NGC 7742, is type II (brightest in infrared light) and it is found 72 million light years away from us.

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What is dark matter and dark energy?

There is far more matter in the Universe than what is contained in stars, planets, and other visible objects. We have called this invisible mass 'dark matter'. We do not know much about dark matter yet, and some of it could take the form of MACHOs, or massive compact halo objects. These include brown dwarfs and some types of black hole. It is a lot more likely though that the majority of dark matter consists of WIMPs, or weakly interacting massive particle, or some other type of subatomic particle that hasn't been discovered yet.

There is evidence that dark matter exists, even if we don't know much about it. Many galaxies should just fly apart, but instead they rotate, and this can really only be because they contain large amounts of matter that we can't see.

Even if all the dark matter we deduce from observations is included though, the density of the universe is still not enough for theories of its evolution to make sense.

To find a solution to this problem, cosmologists came up with dark energy, a force that counteracts gravity and causes the universe to expand faster. We still know so little about dark energy though.

How are people searching for dark matter

To find dark matter, scientists are using underground detectors which search for particles like WIMPs and neutrinos, which are two of the forms dark matter could take. Even if they find that dark matter takes the form of neutrinos, their size means their combined mass could only account for one percent of the Universe's dark matter. This would only leave us with so many more questions about the rest of the dark matter out there.

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What's a black hole?

A black hole is a region of space that contains a singularity, which is some matter squeezed into a point of infinite density, at its centre. Within a certain spherical region around this singularity, the gravitational pull is so strong that nothing, not even light, can escape, earning them their name.

The fact that light cannot escape from a black hole means we cannot observe them, just the material around them. The ones we have discovered so far have usually had a disc of gas and dust spinning around the hole, throwing off hot, high speed jets of material or emitting radiation, like X rays, as matter falls into the hole.

Supermassive Black Holes

Supermassive black holes can have a mass equivalent to billions of suns, and can be found in the centres of galaxies, like our own. We don't fully understand the origin of supermassive black holes, but they may be a by-product of the process of galaxy formation.

Stellar Black Holes

Stellar black holes are smaller than Supermassive black holes, and they form from the collapsed remnants of exploded supergiant stars. They may be common in all galaxies.

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Are there aliens?

This post is inspired by a talk I went to today about exoplanets and the future of humankind.

In the talk, Chris Impey uses the analogy of sand to illustrate the incredibly likely chance that we are not alone in the universe. In the milky way, there are about 10^10 exoplanets in the habitable zone around their star. This number is about the same as the amount of grains of sand in a child's sandpit. That seems like quite a lot of exoplanets that can harbour life, right? Now the universe as a whole has an even more inconceivable number of exoplanets that could contain life, 10^21. To wrap your mind around this big of a number, imagine a beach ten miles long and 10 metres deep. Every single one of the grains of sand is a possible civilisation out there.

So with the vast number of planets that could have life, we can almost certainly say we are not the only planet with living species on it. Although the vast majority of this life on the planets will be microbes, we can use the Drake Equation to find out how many civilisations there are out there, which, until we as humanity have a bit more knowledge, can leave us with a number of anywhere between 1 to 1,000,000 civilisations out there.

A discovery to be excited for

It is quite likely that in the near future (10 years? Don't treat that as a fact) there will be microbes found somewhere. Whilst this is understandably not nearly as exciting as finding a whole civilisation out there, it will change the whole of biology forever, because any living microbe will either have the same/similar biology as what is on Earth now, or it won't. Whilst this seems obvious, it is worth saying that whichever one of the two we find microbes to be on other planets, it will answer a lot of questions we have right now about biology.

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What's in the moon's atmosphere?

The moon's atmosphere is very thin, with a total mass of only 10,000kg, compared to the Earth's 5.15 x 10^18 kg. It has the same amount of gas as is released by a landing Apollo spacecraft!

The moon's surface temperature varies by about 270 degrees celsius, or 480 degrees Fahrenheit, over a lunar day. The quantity of gas near the surface of the moon is 20 times greater during its cold nights than its hot days.

Because the moon's gravity is just one sixth of Earth's, the moon's atmosphere is escaping all the time. However, it is also constantly being replenished by the solar wind.

The gases it is made up of are neon (29%), helium (25.8%), hydrogen (22.6%), argon (20.6%), and trace gases. The neon, hydrogen, and helium are captured from the solar wind, but the argon is derived from the radioactive decay of potassium in lunar rocks.

We know about the gases on the moon because of The Apollo 17 mission, which deployed an instrument called the Lunar Atmospheric Composition Experiment (LACE) on the moon's surface. It detected the gases.

Some more interesting facts

From here on Earth, researchers using special telescopes that block light from the moon's surface have been able to make images of the glow from sodium and potassium atoms in the moon's atmosphere as they are energised by the sun.

The moon's atmosphere may play a key role in a potential lunar water cycle, facilitating the transport of water molecules between polar and lower latitude areas. The moon may not only be wetter than we once thought, but also more dynamic.

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All about Wolf-Rayet stars

Some facts about Wolf-Rayet Stars

Wolf-Rayet stars are named the ‘most massive and brightest stars known’. This is because their temperatures start at 30,000 degrees celsius. They also have strong stellar winds which blow away their outer atmospheres, revealing the stars’ inner layers. Blowing at over ten million miles per hour, the stars shed about 2 thousand billion billion tons of material every year. That’s equivalent to the mass of three Earths! Since these stars have trouble holding themselves together, they don’t last very long, burning up their fuel quickly and blasting mass into space, eventually tearing themselves apart. They are usually members of binary stars with O or B stars (types of stars classed by temperature) as companions.vd

The discovery

The French astronomers Charles Wolf (1827-1918) and Georges Rayet (1839-1906) co-discovered this type of unusual, hot star, which are now named after them. They discovered Wolf-Rayet stars by using the Paris Observatory’s 40cm Foucault telescope in 1867 to observe three stars whose spectra had strong, broad emission lines, but few absorption lines, which is unusual for stars. 

For decades, the reason for these emission bands remained a mystery. Eventually, it was discovered that these lines resulted from the presence of helium, which was discovered in 1868, one year after the original observation. E.C.Pickering also compared Wolf-Rayet spectra with nebula spectra, and noticed similarities between them. This led to his discovery that some or all Wolf-Rayet stars are in the centre of nebulae.

In 1929, doppler broadening (the broadening of spectral lines due to the Doppler effect caused by a distribution of velocities of atoms or molecules) was being used to explain the width of the emission bands. It was concluded that the gas surrounding Wolf-Rayet stars must be moving with velocities of 300-2400 km/s, and therefore they are continually ejecting gas into space. This produces an expanding envelope, or bubble, of nebulous gas. The force that ejects this gas was then discovered to be radiation pressure.

Later, Rayet became Director of the Bordeaux Observatory, and to this day, we have discovered over 500 Wolf-Rayet stars in our galaxy. 

About the most massive star, R136a1, which is a Wolf-Rayet star

R136a1 is the most massive star known, which is a Wolf-Rayet star. It is 163,000 light years away from the Sun, and is located in the Large Magellanic Cloud. It is also part of the R136 super star cluster, and has the mass of 315 suns. Despite being the most massive star known and shining 9 million times brighter than the sun, it requires a telescope to see. An interesting fact about R136a1 is that it defies what scientists know about how stars form. A popular hypothesis among scientists is that R136a1 did not form directly from the collapse of a molecular hydrogen cloud, but rather from two massive stars colliding. 

About WR 124, a Wolf-Rayet star

WR 124 is 15,000 light years away from the Sun. Its spectral type is WN, meaning it falls into the hottest ‘O’ spectral type of stars, but is referred to as ‘W’ from Wolf-Rayet. The ‘N’ means it shows strong emission lines of nitrogen. WR 124 is the glowing star in the centre of a huge, fiery nebula. WR 124 has a surface temperature of around 50,000 degrees celsius, and is one of the hottest known Wolf-Rayet stars. It is a massive, unstable star which is blowing itself apart. Its material is travelling at up to 150,000kph. The nebula that surrounds the star, M1-67, consists of vast arcs of glowing gas which is violently expanding outwards into space. M1-67 is quite young, only 10,000 years old, and it contains clumps of material within it with masses 30 times the mass of Earth and diameters of 150 billion km.

WR 7, another Wolf-Rayet star

WR 7 is also 15,000 light years away from the Sun. It produced the emission nebula NGC 2359, which is also known as Thor’s Helmet because it looks like a helmet with wings. The nebula has a diameter of around 30 light years, and has WR 7 at its centre. Its surface temperature is between 30,000 degrees celsius and 50,000 degrees celsius, which is 6 to 10 times the temperature of the sun. It is an incredibly unstable star, ejecting stellar material into the interstellar medium at speeds which approach 7.2 million kph! Even though it is a massive star, it loses the mass of the Sun every thousand years. Material ejected from the star is done so in a spherical manner, which produces a bubble of material. This bubble has been shaped further by its interactions with the surrounding interstellar medium. WR 7 lies at the edge of a dense, warm molecular cloud, which is unusual.