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k2-18b water discovery

Water discovered on an exoplanet

In a fascinating discovery, astronomers found water in a planet’s atmosphere orbiting a far-flung star outside our solar system with Earth-like temperatures that could sustain life. This exoplanet is almost 110 light-years away from our world, and the discovery of water is rather exciting.

According to the research released in the journal Nature Astronomy, K2-18b is eight times the Earth’s mass. It is now the only exoplanet known to have water and temperatures possibly inhabitable. Unlike other giant exoplanets where atmospheric water has been detected, K2-18b could be rocky and rugged like Earth, Venus, and Mars.

Researchers said the planet orbits the cool dwarf star K2-18, which is in the Leo constellation.

“Finding water in a potentially habitable world other than Earth is incredibly compelling,” remarked author Angelos Tsiaras from the University College London (UCL) in the UK.

“K2-18b is not’ Earth 2.0′ as it is significantly heavier and has a different atmospheric composition. However, it brings us closer to answering the fundamental question: Is the Earth unique?” adds Tsiaras.

K2-18b was discovered in 2015. Since then, it has been researched on, and it was a bit of a tricky exoplanet to explore. We understand this rounds up quite carefully around a red dwarf star named K2-18, completing the round every 33 days. Furthermore, the stellar rates of radiation on the planet are comparable to those on Earth (except for the elevated flare activity typical of red dwarfs).

We also understand that the planet’s size is about twice as large as the earth, and about eight times the mass. Astronomers have even reduced the planet to two kinds. In 2017, a team concluded, either a rocky, atmospheric planet like Earth but more massive, or a world with a mostly watery interior covered by a dense ice shell, like Enceladus or Europa.

Kepler space telescope which used to identify planets using the transit method recognized this planet. This is possible when the star, planet and earth are in the same line. The light coming from the star is monitored and when the planet passes in between star and earth (transit), we can see a dip in star’s light. This can give us a lot of data.

It can also support us in studying the atmosphere of a planet. If the light from the star moves through specific wavelengths, certain gasses can absorb them, thus, creating a range of lines. These can be decided by comparing a spectral star profile with a spectral transit profile.

It isn’t simple, however. Even the first detection of the planet needs extremely delicate instruments to detect starry dips, as well as remarkably faint spectral absorption lines.

Tsiaras and his team used the WFC3 device on the Hubble space telescope. They pictured eight transits of the planet in front of the star, bringing them together to generate a weighted average, thereby producing the planet’s spectral profile.

After this, they had to understand what the spectral star profile conveyed through modeling.

Originally, they ran K2-18b atmosphere models with a range of atmospheric molecules that could produce absorption lines, comprising water (H2O), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and ammonia (NH3).

In the planet’s spectrum, only water could be recognized with confidence. Keeping this in mind, the team developed their analysis, now using water solely as a trace gas.

They then formed the atmosphere by applying three different approaches: cloudless, with water vapor in a hydrogen-helium atmosphere; cloudless, with water vapour, hydrogen-helium, and molecular nitrogen; and then cloudy, with water vapour and hydrogen-helium.

All three simulations produced a statistically notable atmosphere at high-resolution levels, with values so similar they couldn’t quite distinguish the three basic types.

We need a lot more data to confirm things and probably the next-generation space telescopes like James Webb telescope might clarify things

Journal Reference: Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b

main exoplanet

Researchers develop images to understand how Earth might look to aliens

In the last ten years, 4000 exoplanets which we currently know were discovered. In this period, the process shifted gradually from discovery to characterisation. In the future, advanced equipments will help to know more about the surfaces and atmospheres of exoplanets. 

Scientists raised a question about what an advanced species would see while studying the planet. Researchers from Caltech constructed a map of what Earth would appear to alien observers with the help of Earth’s multi-wavelength data. It would also serve in studying about the surface features of exoplanets similar to Earth in the future. 

The study titled “Earth as an Exoplanet: A Two-dimensional Alien Map” appeared in Science Mag journal. It is led by Siteng Fan and several scientists from Division of Geological and Planetary Sciences, California Institute of Technology and Jet Propulsion Laboratory of NASA.

2d surface map of earth

A 2D surface map of the Earth treated as a proxy exoplanet. S Fan et al/California Institute of Technology/arXiv

For finding potentially habitable planets out of Solar System, scientists cannot observe the exoplanets directly, to understand their atmosphere and surface features. So they have to only work with the indications which show that a planet is similar to Earth. 

Fan said that the present exoplanet studies have not set the minimum requirements for habitability. Researchers are not sure about whether the proposed criteria are either sufficient or necessary. Besides this, the observation techniques are not enough to confirm the habitability. 

As right now we know that life exists only on Earth, scientists theorized that remotely observing our planet might act as a proxy for what a habitable exoplanet might look like to an alien civilisation. The water cycle is one of the major elements of the climate on Earth and it consists of three phases. They are water vapour in the atmosphere, clouds consisting of condensed water and water bodies on the surface of Earth.

So their presence might be considered as indications of life and habitability which could be detected from a distance. To obtain Earth’s view to foreign observers, researchers compiled 9740 images that were taken every 68 to 110 minutes in 2016 and 2017 by Deep Space Climate Observatory of NASA. They were able to capture the light reflected from the atmosphere of Earth at different wavelengths. 

Images were then combined to create a 10-point reflection spectrum plotted against time, integrated over Earth’s surface. This created what Earth might look like to someone who observed Earth from several light years away for a period of two years. 

Fan said that the second principal component of the light curve of Earth is related to the fraction of land of the illuminated hemisphere. The reconstruction of the map translated to a problem of linear regression. So the team found the curve parameters for land and clouds after analysis of the resulting curves and comparing with the original images. They identified those parameters related to the land and adjusted it to Earth’s rotation which generated a contour map.

Black lines represent the surface feature and correspond to the coastlines of the continents which are coloured in green to roughly represent the continents. Red denotes the shallow sections of the ocean with blue depicting the deeper areas. These representations would help the scientists to understand if an exoplanet contained oceans, ice caps and clouds. Variation of life curve is dominated by clouds, land and oceans which are important for life on Earth. 

In the future, instruments such as James Webb Space Telescope would help in carrying out detailed exoplanet surveys. Ground-based instruments such as Extremely Large Telescope, Thirty Meter Telescope would carry out direct imaging of planets that orbit close to their stars. With all these advancements, researchers would be able to properly determine which exoplanets are habitable and soon find the next Earth. 

Journal Reference: Science Mag

space full of stars and exoplanets

Researchers recently got the most detailed observation of an exoplanet

What is an exoplanet?
Our universe includes many indefinite stars and planets. All the planets that exist in our solar system orbit around the Sun. The planets that orbit around other stars are called exoplanets. Exoplanets are very hard to see directly even with large telescopes because they are at a few light years far from us. They are concealed by the bright glare of the stars they orbit around. So, astronomers use other ways to detect and study these distant planets. They examine for exoplanets by looking at the effects these planets have on the stars they orbit.

The ESO (European Southern Observatory) has broadcasted the successful observation of an exoplanet using optical interferometry. It’s the first time an exoplanet has been actually seen in this manner and the technique offers a promising example of how we might discern new evidence about the atmospheres of exoplanets. These type of detailed investigations and characterizations are considered critical to discovering other planets in the galaxy that might support earthly life.

The term “Astronomical interferometry refers to the process of merging and combining information from multiple separate telescopes to observe a given target in greater in depth and detail than any single telescope could offer. Combining multiple smaller mirrors doesn’t offer all the compensations of a single large telescope, the total amount of light collected is smaller than a single large mirror would be but it consents for very high angular resolutions and avoids the enormous expense associated with casting huge mirrors.

The ESO scientists observed exoplanet HR8799e using the Very Large Telescope (VLT) array in Chile earlier, which combines data from four telescopes using its interferometer. Each individual telescope has an 8.2m meter range. HR8799e is one of the few exoplanets whose movement has been confirmed via direct imaging.

Directly observing the exoplanet led to some astounding discoveries. We already identified that HR8799e is a very young planet, at just 30 million years old. The planet is literally still glowing with leftover heat from its formation and an ambient temperature of ~1,000 C. The new VLT observations improved our understanding of HR8799e’s spectrum by a full order of magnitude, presenting that its atmosphere contains different compounds than expected.

HR 8799e artist impression

HR 8799e artist impression. (Credit: ESO/L. Calçada)

The analysis further exhibited that HR8799e had an atmosphere containing more carbon monoxide than methane, something not expected from equilibrium chemistry. This was explained by team leader Sylvestre Lacour who is a researcher at the Observatoire de Paris, and the Max Planck Institute for Extraterrestrial Physics. “We can best explain this astonishing result with great vertical winds within the atmosphere preventing the carbon monoxide from reacting and retorting with hydrogen to form methane.”

The atmosphere was also found to contain clouds of iron and silicate dust, implying that the entire gas giant is engulfed in a colossal storm. Lacour suggests the planet is lit and ignited from within, with rays of light penetrating stormy, dark clouds. The silicates and iron then “rain” into the interior. This last process isn’t unique to HR8799e as the astronomers believe that diamonds fall like rain within Jupiter and Saturn as well.

Astronomers hope to accomplish more unswerving observations of exoplanet atmospheres in the future. We may have found nearly 3,000 exoplanets, but our understanding of their atmospheres and their composition is still very limited. As this continues, every planet we image and research will likely tell us something we didn’t know before about the likely atmospheric composition of diverse worlds and where to focus our search for life, in the future.

Nasa Kepler Exoplanet System

NASA’s Kepler Space Telescope detects the first exoplanet candidate in 10 years

At the fifth Kepler/K2 Science Conference which was held in Glendale, CA on Tuesday, March 5th 2019, Ashley Chontos, an astronomer of NASA’s Kepler Mission announced the confirmed identification of the first exoplanet candidate.

The Kepler Telescope was launched by NASA almost exactly 10 years ago. The mission was designed specifically to survey the region of the Milky Way galaxy to discover hundreds of Earth-size and smaller planets in or near the habitable zone and so far, it has done its best. It is in search of hundreds of billions of stars in our galaxy that might have such planets.

The Kepler-1658b was the first planet candidate discovered by the Kepler Telescope and so it was named after its telescope, which by the way characterized as a big star by the Kepler data later recorded.

It came out to be three times larger than previously thought. “Our new analysis, which uses stellar sound waves observed in the Kepler data to characterize the host star, demonstrated that the star is in fact three times larger than previously thought. This in turn means that the planet is three times larger, revealing that Kepler-1658b is actually a hot Jupiter-like planet,” said Chontos.

NASA Kepler Telescope

Illustration of NASA’s Kepler telescope. (Credit: NASA)

Although the team of astronomers led by Chontos had refined analysis and everything pointed to the object truly being a planet, but confirmation from new observation was still needed.

“We alerted Dave Latham (a senior astronomer at the Smithsonian Astrophysical Observatory, and co-author on the paper) and his team collected the necessary spectroscopic data to unambiguously show that Kepler-1658b is a planet,” said Dan Huber, co-author and astronomer at the University of Hawaii. “As one of the pioneers of exoplanet science and a key figure behind the Kepler mission, it was particularly fitting to have Dave be part of this confirmation.”

Being three times larger in size than the Sun itself, Kepler-1658b is 50% more massive. It is one of the closest-in planets around a more evolved star orbiting at a distance of only twice the star’s diameter. As seen from the earth, the star would appear to be 60 times larger in diameter of the Sun if one is standing on the planet.

It is however, very rare for a planet similar to Kepler-1658b to orbit around an evolved star and the reason for this absence is poorly understood yet. The extreme nature of the Kepler-1658b system allows astronomers to place new constraints on the complex physical interactions that can cause planets to spiral into their host stars.

According to the studies and insights gained from Kepler-1658b, this process happens slower than thought earlier. Although, this might not be the primary reason for the lack of planets existing around more evolved stars.

“Kepler-1658b is a perfect example of why a better understanding of host stars of exoplanets is so important.” said Chontos. “It also tells us that there are many treasures left to be found in the Kepler data.”

About NASA’s Kepler Space Telescope

About Kepler Mission:
Launched in 2009, the Kepler mission is specifically designed to survey the region of the Milky Way galaxy in order discover hundreds of Earth-sized and smaller planets in or near the habitable zone and determine hundreds of billions of stars in our galaxy that might have such planets.