# Exoplanets

Exploring the universe

## TESS has found a new Earth-like planet around TOI 700

TESS has recently found a new Earth-like planet around the star TOI 700. TOI stands for Tess Object of Interest. This is the first discovery of an Earth-like planet done by TESS. The star has three planets called TOI 700 b,TOI 700 c,TOI 700 d. The first planet is TOI 700 b that has the same size as Earth but is very hot and is more like an Earth-size Mercury. The second planet is a Super-Earth eight times the size of Earth. The planet is too hot and would be more like a Super Venus. The third planet is a little larger than Earth with 1.7 the mass of Earth and is in the inner edge of the habitable zone of the star. Technically the planet could have liquid water and support life. The planet would not be an Earth twin as it orbiting an M type star a red dwarf with 40 percent of the mass of our Sun. All the planets will probably have tidally locked orbits were one side of the planet would always face the star and be hot and the other side never gets any light from the star and is cold. Perhaps humans could survive in the area between the cold and hot part of TOI 700 d if the planet has a correct atmosphere.

Image credit: NASA's Goddard Space Flight Center

A problem with red dwarf stars is that they usually have violent flares that could strip any planet of its atmosphere. The good news is that TOI 700 does not show a single flare. There are several indications that the star has low stellar activity and simulations of the planet have shown that it is a strong candidate for being a habitable world. We can not be sure if the star had higher stellar activity and flares in the past. The discovery was also confirmed by NASA’s Spitzer Space Telescope. TOI 700 is located 100 light-years from Earth in the Dorado constellation. We will not be able to visit soon, but next year when James Webb telescope is in use that has a sharper instrument we can receive more information about the composition of the planet.

TOI 700 b TOI 700 c TOI 700 d

## Will Betelgeuse go supernova

Betelgeuse is the 11 brightest object in the night sky and the second brightest object in the Orion constellation after Rigel. The star is a red giant about 11 times more massive than the sun. If Betelgeuse had been in the same location at our sun it would have been swallowed all the inner planets and reach the current orbit of Jupiter. The star is just 10 million years old but it has evolved rapidly because of its huge mass and will soon end in a supernova within 100 thousand years. Our sun will just as Betelgeuse also become a red giant in 5 to 6 billion years and will increase its radius to reach the current orbit of the earth. But our Sun is not massive enough to become a supernova instead it will form a planetary nebula and leave behind a white dwarf as massive as the sun but much denser with a radius similar to Earth. Betelgeuse, on the other hand, will explode in a massive supernova and leave behind neutron star 1.5 times more massive than our sun.

Betelgeuse Credit: ESO/L. Calçada

Recently astronomers have discovered that Betelgeuse is getting fainter. By the end of December, it is the 23 brightest object in the night sky. This could mean that Betelgeuse is becoming a supernova, but there could be other explanations for the dimming Betelgeuse is a variable star that has increasing and decreasing cycles of luminosity.

Hypothetically if now Betelgeuse were to explode in a supernova, how will it look like? And will it be dangerous for us? Betelgeuse will become as bright as our moon and light up the night sky and it could even be visible during the day. It lasts for a couple of weeks or even months before it fades away. This would be an amazing astronomical event to observe it will be a priceless scientific possibility for astronomers to learn more about supernovas. Betelgeuse is 640 light-years from the sun and the radiation from the supernova will not affect us on that distance. If we will have the opportunity to see a supernova soon than Betelgeuse should have exploded during the 14th century.

The last time a supernova was visible was 1604 the Kepler's Supernova 20000 light-years from Earth. It was the brightest star in the sky. It was observed by Kepler and was published in the work De Stella nova. It was also reported by Chinese, Korean and Arabic sources.

Betelgeuse

## 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