# Exoplanets

Exploring the universe

## 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

## K2-18 b a water world

K2-18, also known as EPIC 201912552, is a red dwarf star located 124 light-years from Earth, in the constellation of Leo.
Visit the planet here K2-18 b

The star has an Exoplanet K2-18 b in its so-called goldilocks zone. The planet that was discovered by the Kepler telescope in 2015 is 8 times more massive than Earth and has a 33 days orbit.
It is the first Super earth exoplanet in the habitable zone of its star where we have been able to discover water in its atmosphere. Water has previously been discovered on Jovians outside the habitable zone of its star. See our previous article: Atmosphere on exoplanets

The measurements were done with the Hubble telescope and were confirmed by two separate analyses by researchers at Université de Montréal and University College London (UCL) The result was published just a month ago on September 2019. This is very exciting news K2-18 b is cool enough to have liquid water and models suggest that its atmosphere has sufficient pressure that will form clouds and have rainfall just like earth. But some analysis suggests that planets this size could lack solid surface and could be more similar to Neptune than earth. It is not possible from the Hubble data to see how much water there is in the atmosphere.

Credit:AP/M. Kornmesser/ESA/Hubbl­e

K2-18 b is now expected to be observed with the James Webb Space Telescope that will be launched and for the ARIEL space telescope which mission is to study the atmospheres of Exoplanets in great details that will be launched in 2028. These telescopes have the instruments to look for gases in the planet's atmosphere that could only be produced by living organisms. It would be hard to imagine any human-like creatures would be able to live in that environment but may be possible for microorganisms. Even if there is no sign of life. The atmosphere on K2-18 b will tell us a lot about how planets in the habitable zone are formed around red dwarf stars

K2-18 b

## Will we ever be able to travel to the stars

Will humans ever be able to travel to the stars and colonize habitable exoplanets?
Closest habitable exoplanet Proxima Centauri b is 4.25 light-years away. The fastest spacecraft is NASA robotic spacecraft Parker Solar Probe that was launched in 2018 it has a max speed of 192 000 meters per second which is 0,0006 percent of light speed. With that speed, it will take 7000 years to reach Proxima Centauri b. We need to get to a speed at least 10 percent of light speed to reach Proxima Centauri in a reasonable time. A reasonable time is 50 years if we consider the wait dilemma. In 50 years we will be able to build space ships that can reach the target destination much faster, so it will be more beneficial to wait.
We will never reach the stars using rocket engines because we would need more fuel than it is mass in the observable universe to reach 10 percent of light speed.
The rocket equation is

$$\Delta v =v_{e}\ln \frac{m+f}{n}$$
Where m is the mass of the vehicle, ve is the exhaust velocity of the rocket and f  is the mass of the fuel. If we solve f  from the rocket equation, we get:
$$f =me^{\frac{\Delta v }{v_{e}}}-m$$
If  we assume that the mass is equal to 1000 kg and exhaust velocity of 210,000 m/s which is the speed of our very best reaction engines, we get:
$$1000e^{\frac{3000}{21}}-1000 \approx 1*10^{65}$$
Compare that with the total amount of mass in the observable universe that is  $$1.5*10^{53}$$kg.

It would be theoretically possible to make the trip using nuclear fusion by detonating many nuclear bombs behind the spacecraft. Physicist Freeman Dyson and Ted Taylor at General Atomic worked with this idea in a project called Orion in 1958, but the Partial Test Ban Treaty of 1963 that forbid nuclear bombs in space ended the project. Another idea is to use a fusion rocket. Project Daedalus was a study conducted between 1973 and 1978 to design an unmanned interstellar spacecraft to reach Barnard's Star 5.9 light-years away. The trip was estimated to take 50 years, but the technology behind fusion rockets is complicated and we are not there yet.

A more efficient method is to use antimatter rockets. When a subatomic particle collides with its respective antiparticle a large fraction of the rest mass is converted into energy. Depending on how much antimatter we could make it would be possible to reach a speed of 80 percent of light speed. The travelers on a ship with that speed only need to wait 3.2 years to arrive at Proxima Centauri b.
Because of time dilation from Einstein's special relativity :
$$t =\frac{t_{o}}{\sqrt{1-\frac{v^{2}}{c^{2}}}}$$

$$\Rightarrow \frac{4.25}{0.8}*\sqrt{1-0.8^{2}}=3.2.$$
Antimatter is produced in many experiments at CERN, but far from the amount that is needed it takes a lot of energy and it is hard to contain.

Credit Gerhard Janson pixabay

Another option is to travel faster than light. The Mexican theoretical physicist Miguel Alcubierre created an idea in 1994 which a spacecraft could travel at warp speed by using Albert Einstein's field equations in general relativity.
A signal in space cannot move faster than light, but the space itself can expand faster than light. The idea is that space is moving the ship just like a surfers board is moved by the water waves. This is mathematically possible, but one needs negative gravity. Negative gravity is produced by negative mass, not anti-matter which has positive gravity. Scientists have never observed negative gravity or mass, but there is nothing in the Einstein field equations that forbid it. Negative mass is equal to negative energy.  Dark energy is postulated to act in opposition to gravity and will perhaps work as negative energy. Dark energy explains why the universe is expanding at an accelerating rate and 72 percent of total energy in the universe consists of dark energy. If scientists figure out how to get this dark energy, perhaps warp drive like in Star-trek will be possible in the future.

The most promising option to travel to Proxima b is to use a solar sail read about the project here Breakthrough Starshot

Proxima Cen b Alcubierre drive