Exoplanets

Exploring the universe

Saturns potentially habitable icy moon Enceladus


Enceladus is the sixth biggest moon of Saturn. The moon that was discovered by William Herschel in 1789 is named after the giant Enceladus of Greek mythology. It won't live up to its name when it comes to size. With a diameter of 500 km, the moon would fit within the north sea. But it will live up to its name when it comes to being one of the strongest candidates for finding non-terrestrial microbial life in our Solar system. Studies have shown half of Earth's biomass lives long under the surface. As microbial life is not just a surface phenomenon the chances of finding this kind of organism outside the so-called goldilocks zone of a star increases. The strongest candidates are moons around gas giants that under their thick icy surface has oceans heated with volcanic activity. One of those candidates is Jupiter's moon Europa that I wrote about in this article. And the other is Enceladus.

Enceladus

Image credit: NASA/JPL-Caltech

On January 16th, 2005 Nasa's probe Cassini's was on a flyby pass Saturn when it captured a very unusual event on Enceladus. There was a bright light coming from the south pole of the moon shining out into space. There were enormous geysers plumbing out vapor into space, more than 8000 times larger than geyser on Earth. Nasa immediately decided that Cassini should have a new mission. To study Enceladus. The probe was reprogrammed from earth to fly into these plumbs and find out was the vapor was made of. It took three years of reprogramming until Cassini was able to do that and the result showed that the vapor was liquid water. Some of the water will fall back on Enceladus as snow but the most will make of the material in Saturn's E ring. The result also showed that the water contains salt which is a very important ingredient for life. The chemicals in the water were very similar to earth and it also showed that something inside Enceladus was heating the water. On June 27, 2018, scientists reported the detection of complex organics compounds from the Cassini data. The Cassini mission ended in September 2017 with the probe crashing into Saturn's atmosphere.

It is very hard getting a probe to investigate Enceladus within a reasonable budget. Several future missions to Enceladus that have been proposed has been canceled. Here is are a list of candidates that are under study and could be our next mission to the icy moon:

  • Enceladus Life Finder (ELF) has been twice proposed by Nasa, but it has not been selected yet. The probe would orbit Saturn and fly through the geysers several times.
  • Enceladus Life Signatures and Habitability (ELSAH) is another proposed project by Nasa. It has not been selected for launch but has received development funds to improve the instrument. Any details about the mission have not been made public yet.
  • Explorer of Enceladus and Titan (E2T) a mission that would investigate both Enceladus and Titan is proposed by ESA in collaboration with NASA. The probe will have high-resolution mass spectrometry to analyze the ice Enceladus.
  • Enceladus Explorer (EnEx) is founded by the German Aerospace Center and the research is carried out on seven German universities. EnEx is a lander mission and will be equipped with an iceMole that is a maneuverable ice-melting probe.
  • Russian billionaire Yuri Milner, the founder of Breakthrough Initiatives that I wrote about in this article. He is also planning a mission to Enceladus. The low-cost and low mass spacecraft using solar sails will fly through the geysers once and analyze its content for biosignatures. Milner will also receive scientific and technical expertise from Nasa during this project.
Saturn Enceladus

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

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