Astronomers find exoplanet with cloud-free atmosphere
London, May 8: Astronomers have found that a planet outside our solar system, which is similar to Saturn in mass and exceeds the size of Jupiter by 20 per cent, has an atmosphere free of clouds.
The hot gas giant, WASP-96b, periodically transits a Sun-like star 980 light years away in the southern constellation Phoenix.
Using the the European Southern Observatory's Very Large Telescope in Chile, the team studied the atmosphere of WASP-96b when the planet passed in front of its host-star.
This enabled the team to measure the decrease of starlight caused by the planet and its atmosphere, and thereby determine the planet's atmospheric composition.
"We've been looking at more than twenty exoplanet transit spectra. WASP-96b is the only exoplanet that appears to be entirely cloud-free and shows such a clear sodium signature, making the planet a benchmark for characterisation," said lead author of the study Nikolay Nikolov from University of Exeter in Britain.
Just like an individual's fingerprints are unique, atoms and molecules have a unique spectral characteristic that can be used to detect their presence in celestial objects.
The spectrum of WASP-96b shows the complete fingerprint of sodium, which can only be observed for an atmosphere free of clouds, according to the study published in the journal Nature.
It has long been predicted that sodium exists in the atmospheres of hot gas-giant exoplanets, and in a cloud-free atmosphere it would produce spectra that are similar in shape to the profile of a camping tent.
"Until now, sodium was revealed either as a very narrow peak or found to be completely missing. This is because the characteristic 'tent-shaped' profile can only be produced deep in the atmosphere of the planet and for most planet clouds appear to get in the way," Nikolov added.
Clouds and hazes are known to exist in some of the hottest and coldest solar system planets and exoplanets.
The presence or absence of clouds and their ability to block light plays an important role in the overall energy budget of planetary atmospheres.
"It is difficult to predict which of these hot atmospheres will have thick clouds. By seeing the full range of possible atmospheres, from very cloudy to nearly cloud-free like WASP-96b, we'll gain a better understanding of what these clouds are made of," explains study co-author Jonathan Fortney, Professor at University of California, Santa Cruz (UCSC), US.
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Confident we are going to win Kerala: Shashi Tharoor
New Delhi (PTI): Congress leader Shashi Tharoor on Thursday expressed confidence in the victory of the United Democratic Front (UDF) in Kerala, saying the Congress-led alliance will win more than 75 seats out of the total 140 in the state.
Tharoor, who hails from Kerala, said he was not surprised to see the results of the exit polls, most of which predicted a victory for the UDF that has been out of power for 10 years in the state.
"We have been on the ground. I have campaigned in 59 constituencies across 12 districts out of 14. I was very confident we are going to win.
"Everything that I have picked up from not just my party colleagues and workers but also from other observers, media and others have always convinced me that we were going to score a comfortable win of above 75 seats. And all the (exit) polls have confirmed the same thing," he told reporters here.
The Thiruvananthapuram MP said he was not surprised to see the results of the exit polls but in general he was not a big fan of exit polls in India.
"Because ours is not purely a homogenous society. We have to take into account gender issue, caste issue, class issue, regional disparities. You never get a convincingly large enough sample to give an accurate poll and now there is the additional complication that we have heard about in West Bengal this year that many people are unwilling to answer the questions of the pollsters," he said.
The Congress leader said normally, it used to be below 10 per cent that people said that they would not answer.
"Even if you are a reputable exit pollster, in Bengal, one polling company has said 60 per cent of people refused to answer. So, what is the worth of a poll where 60 per cent of your respondents have not answered," he said.
Several exit polls on Wednesday predicted a comeback by the Congress-led UDF in Kerala after 10 years, dethroning the CPI(M)-led Left Democratic Front (LDF).
Polling for the 140-member Kerala assembly was held on April 9. Results of assembly elections in West Bengal, Tamil Nadu, Assam, Puducherry, besides Kerala, will be announced on May 4.
