# Exoplanets

Exploring the universe

## The mystery with Tabby's star

The Soviet astronomer Nikolai Kardashev proposed in 1964 a method that is measuring a civilization's technological advancement based on how much energy they are able to consume.
This is called the Kardashev scale and has three categories.

1. A type I civilization or a planetary civilization are able to harness and control all energy available on their planet. With estimated energy use of size 10^16 watt
2. A type II civilization or a stellar civilization is able to harness and control energy at a scale of its solar system. With estimated energy use of size 10^26 watt
3. A type III civilization or a galactic civilization is able to harness and control energy at a scale of its host galaxy. With estimated energy use of size 10^36 watt

The Kardashev's scale could be calculated with the formula suggested by the astronomer Carl Sagan

$$K=\frac{\log_{10} P-6}{10}$$

where P is the energy use in watts. The current energy usage of the human civilization is 18*10^16 and has a K value of $$0.72=\frac{\log_{10} 18*10^{12}-6}{10}$$

and we will probably reach Type I civilization status in 100-200 years. Perhaps we will reach type II in a few thousands of years.

One hypothetical technology advancement to reach a type II civilization would be to build a megastructure that encapsulates the entire star and captures most of its power output. This is called a Dyson sphere and was first suggested by Freeman Dyson in his paper "Search for Artificial Stellar Sources of Infrared Radiation" from 1960, but the concept was previously described in a science fiction novel Star Maker by Olaf Stapledon in 1937. The megastructure could be technically possible by using solar power satellites or space habitats orbiting around the star in a so-called Dyson swarm. Such construction would dim the light of its host star and SETI has adopted this assumption in their search for extraterrestrial life.

Image credit: NASA/JPL-Caltech

In September 2015 citizen scientists from the Planet Hunters project discovered unusual light dimming around the star KIC 8462852 when they were analyzing data collected by the Kepler space telescope. The star is of F-type with 1.4 the mass of our sun and is located in the constellation Cygnus 1470 light-years from earth. The star got the name "Tabby's Star" after the American astronomer Tabetha S. Boyajian, the lead author of the scientific paper describing the unusual light fluctuations. The fluctuations can not be caused by a planet, because the dimming is irregular and it has been measured to vary between 22 percent and 5 percent. Analyses of old data have shown the brightness of the star has also been dimmed by 14 percent since 1890. The star is too old for the planet-forming event still would occur. The SETI Institute used the Allen Telescope Array to look for radio signals from possible intelligent aliens. In fall 2015 the news that SETI was investigating an alien megastructure got viral and took the internet by storm. The light fluctuations have been studied in 2017 and now in 2019 by TESS. The star is still a SETI target as a natural phenomenon causing the dimming is still not fully explained.

As not all wavelengths are equally blocked the most likely explanation is that the dimming is caused by dust and not aliens. Inward migration of Jovians could make their moons escape their gravity and become a so-called ploonets. Numerical simulations have shown that when these ploonets melting they spread a dust cloud around the star and that could explain the light curve of Tabby star.
A study with 21 candidates star with similar light curves was published this year that suggests that this natural event might be common, but more investigations are needed to confirm if these candidates really are tabby like.

Dyson Tabby star

## Nobel prize in Physics for the discovery of an Exoplanet

Tomorrow in Stockholm will the ceremony for the Nobel Prize in Physics be held.

The Swedish chemist and the inventor of dynamite, Alfred Nobel. Died 10 December 1896 in San Remo Italy. Nobel was also a very rich businessman and he was before his death very concerned that the world would not remember him after his death. So he wrote a testament that his fortune should be used to award big contributions to science. The prizes were in Chemistry, Literature, Peace, Physics, and Physiology. The prizes were first awarded in 1901 and Wilhelm Röntgen received the prize in Physics for the detection of electromagnetic radiation in wavelength of X-rays. This year's prize in Physics goes to James Peebles the father of modern cosmology. Peebles has done achievements in cosmology since 1970 and much modern cosmology is based on his ideas and calculations.

Image credit: NASA/JPL-Caltech

He will share the prize with Michel Mayor and Didier Queloz for their discovery of the first exoplanet orbiting a sun-like star. The first exoplanet discovered was 51 Pegasi b. 51 Pegasi is 50 lightyears from earth in the constellation Pegasus and is like our sun a G-type star. The star has an exoplanet 51 pegasi b that is 150 times more massive than Earth and is located at a distance of 0.05 AU from its star with an obit of 4 days it is a so-called hot Jupiter. Michel Mayor and Didier Queloz discovered the planet by measuring the variation of the color from the starlight. The method is based on the concept that a planet system is orbiting around its centrum of mass and when the star moves from us the color of the light will shift towards red. The discovery was made on October 6, 1995. At the time the scientist thought that planetary systems around other stars always was formed in the same way as ours. The discovery came as a surprise. Now we have found that hot Jupiters are common and the scientists had to rethink their theories about how planetary systems are formed.

51 Peg b

## New observations suggest that the universe is round

The riddle of the size of the universe has involved scientists ever since the childhood of cosmology. Newton believed that the universe is infinite, while Kepler believed in a finite.
Albert Einstein was the first physicist that gave the concept of a finite universe a sustainable theoretical foundation. The gravity can make space curve so much that the overall structure closes itself in the same way as the surface of a globe. The shape of the universe is depending on how much mass it is in the universe. The density parameter was derived by Alexander Friedmann in 1922 from Einstein's field equations.
$$\Omega =\frac{\rho}{\rho_{c}}$$
where ρ is the actual density of the Universe and ρc is the critical density.
The critical density is according to Friedmann equations
$$\rho_{c} =\frac{3H^{2}}{8\pi G}$$

where G is the gravitational constant 6.674×10−11 m3/(kg⋅s2)  and H is the Hubble parameter a function of time that tells us how fast the universe is expanding it may be derived from the same equations as

$$H^{2}= \frac{8\pi G \rho }{3}-\frac{kc^{2}}{a}$$

then the density parameter becomes

$$\Omega = \frac{H^{2}+\frac{kc^{2}}{a}}{H^{2}}$$
where c is the speed of light in vacuum and  k is the curvature constant and a is the scale factor

If the density parameter:

• Is bigger than 1 and k equals 1, then the universe is finite and has a spherical shape
• Is smaller than 1 and k equals -1, then the universe is infinite or finite and has a hyperbolic shape
• Is equal to 1 and k equals 0, then the universe is infinite and is flat

Credit: NASA / WMAP Science Team

The Planck space observatory was a spacecraft operated by the European Space Agency (ESA) from 2009 to 2013 and mapped the cosmic microwave background CMB. CMB is the radiation leftover from the big bang.
Several observations have indicated that the universe is flat and that fits very well with our current theoretical models, but re-analysis of the Planck data shows that we live in a finite spherical universe where the density parameter is bigger than 1
Here is the paper: nature.com
Here is an article about it quantamagazine.org

The density of the universe is according to the article calculated to be about 6 hydrogen atoms per cubic meter of space and the critical density is 5.7 hydrogen atoms per cubic meter of space, which gives the density parameter value of 6/5.7 =1.05.

Universe Hubble

## Exoplanet Hunter in virtual reality

One proposed solution to the Fermi paradox why we don't see any Aliens is that advanced civilizations will create their own virtual reality where they have everything they need and therefore stop caring about the outside world. Perhaps our civilization shares the same fate.
Here comes the first step for humanity to become a virtual civilization. Why should you invest in long expensive and dangerous interstellar space travel when you can just sit at home and explore the space with our new Exoplanet Hunter VR app.

Exoplanet Hunter VR is available on Oculus store and will work for Oculus go. Oculus Go is a standalone virtual reality headset that was released on May 1, 2018. It is possible to navigate all discovered exoplanets in the sky with the milky way skybox as a background using the oculus go controller laser pointer to visit an exoplanetary solar system in 3D. It is also possible to visit an exoplanet in and read about the information to learn more. You can always navigate back by using the back button.

The application is developed with Unity. Unity is a cross-platform game engine developed by Unity Technologies.

Here is a promo video of the new app

Here is the link to the app on Oculus store Exoplanet Hunter Vr

VR

## Looking for life on Europa

In 1610 Galileo Galilei an Italian astronomer pointed his telescope towards the sky. His discoveries have forever changed our understanding of the cosmos. He looked at the moon and saw a landscape with mountains and valleys. He looked at the gas giant Jupiter and he saw moons orbiting the planet. He believed that smaller bodies were revolving around bigger and that the Earth and the planets were orbiting the Sun. Heliocentrism that was proposed by Copernicus in 1543 was considered by the Roman Inquisition as foolish and blasphemy and Galileo was sentenced to spend the rest of his life in house arrest. Galileo was employed as a mathematics tutor for Cosimo de' Medici and he named the moons Medician Stars and called them Jupiter I, II, III and IV. But Simon Marius a German astronomer that discovered the Moons independently at the same time. Named them Io, Europa, Ganymede, and Callisto after Zeus mistresses. Galileo's names were used until the mid-20th century when more inner moons were discovered.

Credit:NASA/JPL/DLR

The unmanned spacecraft Galileo was named after Galileo Galilei was launched in 1989 it arrived at Jupiter in 1995. It was the first mission that investigated Jupiter's moons and Galileo was in the Jupiter system for 8 years until it was terminated by falling into Jupiter's atmosphere in 2003. The data the spacecraft collected supported the idea that there is a liquid ocean of water under the moon Europa's icy surface. The ocean is bigger than all the water on Earth and the moon is geologically active due to tidal forces from Jupiter's gravitation. Vulcans will heat the ocean, and energy and water are the building blocks of all living organisms. Considering that the ice surface is 20 kilometers thick then the pressure in the ocean could be calculated using Europas surface gravity and density of ice $$g_{eu}\rho _{ice}s=$$1.315 m/s² *917 kg/m3* 20000 m = 24 Mpa or 240 bar

Deep-sea creatures can live at 20 to 1000 bars on earth. Also, the temperature should be similar and the thick ice blocks the deadly radiation from Jupiter. This makes Europa the best candidate for looking for life in our solar system
The Hubble telescope discovered in 2014 indications that there are geysers shooting out water in space from Europa's icy surface.

Nasa will send a probe called the Europa clipper in 2025. The clipper will not be orbiting the moon as radiation from Jupiter could damage the electronic instruments on the probe. Instead, the clipper will make 45 flybys in one of those flybys the probe could catch one of those geysers and analyze the molecules in the gas for living organisms. The probe will be equipped with advanced instruments that will scan the surface and with radar map the thickness of the ice surface. It could help to find pockets of water closer to the surface and also investigate what could be a good spot for a lander. It is also suggested that the mission will include a lander that will be financed by the congress. Drilling through the 15-20 kilometer would be very technical hard and expensive, but if the clipper finds interesting results then perhaps the next mission will be launching a submarine under its surface and perhaps we could find some alien fish or mermaids.

European Space Agency is also planning a mission to Europa, Ganymede, and Callisto. All three moons might have significant bodies of liquid water beneath their surfaces. The JUpiter ICy moons Explorer is an interplanetary spacecraft that will launch in 2022 and reach the system in 2029 it will end up orbiting the moon Ganymede in 2033.

Jupiter