2019 – Posted in: RSTV

SUPER-EARTH

In News

Astronomers have finally uncovered water vapor in the atmosphere of a super-Earth.

A research report in the general astronomy says water has been found in the atmosphere of the planet orbiting in a star outside our solar system. This planet has earth-like temperatures that could support life called K2-18B. It is 8 times the mass of earth and is now the only exoplanet known to have both water and temperatures that could be potentially habitable known as Super-Earth.

The planet orbits the dwarf star K218 about 110 light-years from us in the Leo constellation. But there is bad news as well, researchers say given the high level of activity of its red dwarf star K2-18B may be more hostile than earth and even may be forced to radiations.

Data from NASA’s Hubble space telescope has revealed water vapour in the atmosphere of an earth size planet called as Super-Earth. Although this exo-planet orbits a star that is smaller than our sun, it falls within what is known as the star’s habitable zone. The findings make the world which is called K2-18B a candidate in the search for alien life.

In an incredibly exciting finding, astronomers discovered water in a planet outside our solar system that has temperatures suitable for life. According to the study, water vapour has been detected on a potentially habitable super-earth known as K2-18B located about 110 light-years away in the constellation Leo. K2-18B is classified as a super-earth because it is bigger than our earth twice as big in fact as well as eight times heavier. The exo-planet was first spotted in 2015 by NASA’s Kepler spacecraft but analysis of data has revealed new details that have not seen on a super-earth before.

The study revealed that the new planet sets in its star habitable zone where it is based in the same amount of energy as Earth get from the sun.

K2-18B has a temperature cool enough to have liquid water between zero and forty degrees Celsius. It also possesses powerful gravity that would make it difficult to walk upon and aside from water vapour; atmosphere contains mostly hydrogen gas a molecule that makes up less than a part million over the atmosphere. Despite all this information astronomers believed that the new planet is very unlike our homeworld as it is 650 million miles away from earth meaning too far to send a probe. Many astronomers also dispute the claim that the planet is potentially habitable. One analysis indicates that the planet is 1.5 times of the earth are unlikely to have a rocky surface. There is also concern that K2-18B’s size and gravity would make it difficult for the world to support life. Other critics suggest that the planet should not be classified as a super earth but as a mini Neptune instead. Another issue is that astronomers cannot agree what conditions are needed for habitability.

The K2-18B exo-planet was spotted by NASA’s Kepler space telescope even though Kepler is still operational. The space agency sent out another more advanced satellite in 2018 to find new exoplanets. The Transiting Exoplanet Survey Satellite or TESS is the next step in the search for planets outside our solar system including those that could support life. The mission is looking for exo-planets by surveying two lakh of the brightest stars near the sun. It has discovered twenty-one planets outside our solar system so far and captured data on other interesting events occurring on the southern sky during its first year of science and has now turned its attention to the northern hemisphere to complete the most comprehensive planet-hunting expedition even undertaken. TESS was launched on April 18^th 2018 aboard the spaces falcon nine rocket and has a mission like foe two years.

How’s TESS doing it?

The satellite is surveying the entire sky over the course of its mission by breaking up into twenty different sectors every 24 degrees by 96 degrees across. The powerful cameras onboard the spacecraft stare each sector for at least 27 days. Some of these sections overlap so some parts of the sky are observed for almost a year. From earth, the moon occupies just half a degree which is just less than one by nine thousand the size of the TESS tiles. TESS is concentrating on stars closer than 300 light-years from our solar system. Whenever an observed brightness of a star occurred; it may indicate the presence of a planet passing in front of it. This is known as a Transit.

The Transit method looks for dips in visible light of stars and requires the planet cross in front of the stars along our line of sight to them. Repetitive periodic dips can reveal a planet or planets orbiting a star. Transit photometry which looks at how much light an object puts out at any given time can tell researchers a lot about the planet. Based on how much a dip in light a planet causes in star, we can determine the size of planet. Looking at how long it takes a planet to orbit its star, scientists are able to determine the shape of the planet’s orbit and how long it takes the planet to circle its sun. With its observations, TESS is creating a catalogue of exoplanet candidates using this photometry method. After this ground-based follow up automations are conducted to confirm that the exo-planet candidates are true exo-planets and not false positives. These ground-based telescopes measures the masses of planets using the non-planet size orbit and mass the planet composition is determined. It reveals whether the planet is rocky like earth, gas giants like Jupiter or something even more unusual. Additional follow up allows astronomers to study the atmospheres of many of these planets. TESS is also collecting data on supernovae, black holes, and other phenomena in its line of sight along with the planet TESS has discovered. The mission has also identified over 850 candidate exo-planets that are waiting for confirmation by ground-based telescopes. On July 18 2019, the southern portion of the survey was completed and the spacecraft turned its camera to the north. When it completes the northern section in 2020, TESS will have mapped about 80 percent of the sky.

One of the projects that keep space agencies busy is the search for the existence of life beyond earth. Scientists have catalogued thousands of exo-planets orbiting different stars that fir the basic requirements for life as we know it. But what is an exo-planet?

Exoplanet

An exoplanet is a planet or a solar planet outside the solar system. It is a planet orbiting a star other than the sun. For centuries; scientists, philosophers, and science fiction writers suspected that extrasolar planets existed. The first evidence of an exoplanet called Van Maanen was noted as early as 1917 but was rejected by astronomers. The first scientific detection of an exo-planet occurred in 1988. Shortly afterwards, the first confirmation came in 1992 with the discovery of several terrestrial mars planets orbiting the PSR B1257+ 12. Also it is located 2,300 light years from the sun in the constellation of Virgo. The first conformation of an exo-planet orbiting a main sequence was made in 1995 but a giant planet was found in a fourth orbit around a nearby star ’51 Pegasi.’ The planet is believed to be about half the size of Jupiter. Two more exo-planets were discovered in 1996. Besides exo-planets, there are also rock planets that do not orbit any star. These tend to be considered as a separate category. The rock planets in the milky-way possibly number in billions or more. Because these planets are so far away even thousands of light years away. Scientists mainly learn about them through remote observations using telescope and other equipments. Some exo-planets have been imaged directly through telescope but the vast majority have been detected through indirect methods such as transit method and radial-velocity method. Most currently known exo-planets were found either by detecting the effect of the gravitational pull of the planet or by catching the planet as it pass in front of its star and slightly dim it. In 1990’s, NASA’s Hubble Telescope has not only discovered a variety of transiting exo-planets but has characterised the atmosphere of some of them. Hubble continues to remain in operation and in incredibly exciting finding discovered water on an exo-planet first time this week. K218-B is eight times the mass of earth and is now the only known exo-planet to have both water and temperatures that could be potentially habitable.

Another sky watcher NASA’s Spitzer Space Telescope launched in 2003 observes transiting exo-planets in infrared wavelengths. It is planned retirement in January 2020 but now NASA’s Kepler telescope launched in 2009 introduced the modern era in planet hunting. Launched into an earth trailing helium centric record orbit, Kepler was designed to continue monitor the brightness of approximately 1, 50,000 main sequence stars in a fixed field view of four years. Before its retirement in the year 2018, Kepler observed 5, 30,506 stars and detected 2,662 planets during its nine years of service as per a new NASA mission test in 2018. Since the first detection of exo-planets in 1992, scientists have identified 4,031 confirmed exo-planets some of which show signs of having atmospheres. In addition to confirmed exo-planets there are thousands of potential exo-planets as well. Out of the confirmed exo-planets scientists list at least 21 exo-planets that have the best chance of life being there on the solar system.

Since the beginning of civilisation, humanity has wondered whether we are alone in the universe. This idea has inspired a wealth of science fiction stories after Hollywood films all limited only by our imagination. But other features exists list in the vast reaches of space. On other planets on moon and are there other intelligent forms of life are there. Or are we more likely to find something much simpler. Within our solar system, space missions have searched for science of both in ancient times in current life. Beyond our solar system, Kepler’s are revealing thousands of planets orbiting stars. There are also efforts to explore ways to search for life advanced enough to create technology. Techno-signatures are science or signals that would allow us to infer the existence of technological life elsewhere in the universe. The best known techno signatures are radio signals and scientists and radio astronomers have started research for terrestrial intelligence in a systematic manner. Several international organisations are using radio telescopes to detect signals that could be produced by intelligent life. From studying water on mars probing promising ocean worlds such as Europa, or Saturn’s moon to looking for bio-signatures in the atmosphere of exo-planets. Science missions are working together to find unmistakable science of life beyond earth. The underlying scientific goals searching for life beyond the solar system is the same as a study of astro-physical influence on the evolution of life on the planet earth. It will achieve an understanding of the nature and distribution of life and the universe. Exo-biologists study both the distribution and nature of life in other potential habitats to understand and compare the evolution.

Life outside Earth

On a broader level, the objective of searching for life elsewhere can be:
To determine the frequency and morphology of nearby planetary systems
To determine the frequency of occurrence of conditions suitable to the origin of life
To also search for presumptive evidence of life in other planetary systems
To search for evidence of extraterrestrial technology

Beyond the solar system, the discovery of thousands of exoplanets gives us a chance to expand our understanding of how planetary systems are formed and evolution and infer their ability to develop biology. These recent discoveries also give us information about the probability of the existence of other technologically advanced civilisations in the universe.

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