{"id":23238,"date":"2021-09-16T00:00:00","date_gmt":"2021-09-16T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=23238"},"modified":"2021-10-22T11:41:22","modified_gmt":"2021-10-22T11:41:22","slug":"tiny-planet-could-be-water-world","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2021\/09\/16\/tiny-planet-could-be-water-world\/","title":{"rendered":"Tiny planet could be water world"},"content":{"rendered":"\n

The body is the smallest exoplanet ever measured by looking at its star\u2019s wobble<\/span><\/p>\n\n

\"\"
An artist\u2019s impression of a planet orbiting the star L98\u201359; one of the worlds in its planetary system may be made up of 30 per cent water <\/figcaption><\/figure>\n\n

A newly <\/strong>discovered exoplanet could be flooded by a global ocean. With a mass just half that of Venus, the tiny world is the smallest planet ever studied using the radial velocity technique, which looks for the wobble caused by the planet pulling on its host star to measure its size and mass.<\/p>\n\n

The planet is one of three discovered around the star L98\u201359 in 2019 by the Transiting Exoplanet Survey Satellite (TESS), which searches the sky looking for the shadows cast by planets as they pass in front of their host stars. This method allows astronomers to measure the size of the planet, while also revealing that all three planets were probably small, rocky worlds. It also identified that several of the planets were in the star\u2019s \u2018habitable zone\u2019, where liquid water could potentially persist on the surface.<\/p>\n\n

The trio of planets immediately attracted the attention of astronomers, who noted similarities to the inner planets of our own Solar System, especially as L98-59 is only 35 lightyears away. The Very Large Telescope (VLT) soon followed up the discovery, using the radial velocity technique to reveal the masses of the planets, which in turn allowed astronomers to work out their densities. This showed that two of the planets probably had some water while mostly being dry, but the third could be as much as 30 per cent water by mass \u2013 enough water that the whole surface would be flooded.<\/span><\/p>\n\n

Astronomers are keen to understand the planet\u2019s atmosphere and hunt for any signs of water around the planet. However, the world is too small for such observations with the telescopes of today. Instead, it will have to wait for the next generation of telescopes such as the James Webb Space Telescope (JWST),<\/span> due to launch later this year and ESO\u2019s Extremely Large Telescope (ELT), which is under construction in Chile\u2019s Atacama Desert and set to start observing in 2027.<\/p>\n\n

\u201cThis [planetary] system announces what is to come,\u201d says Oliver Demangeon from Portugal\u2019s University of Porto, who led the study. \u201cAs a society we have been chasing terrestrial planets since the birth of astronomy and now we are finally getting closer to the detection of a terrestrial planet in the habitable zone of its star, of which we could study the atmosphere.\u201d<\/p>\n\n

The team has also found \u2018hidden\u2019 exoplanets that had not previously been spotted in this planetary system. They discovered a fourth planet and suspect a fifth in a zone at the right distance from the star for liquid water to exist. \u201cWe have hints of the presence of a terrestrial planet in the habitable zone of this system,\u201d says Demangeon. www.eso.org<\/a><\/p>\n\n

Photo: ILLUSTRATION ESO\/M. KORNMESSER, NASA\/DANIEL RUTTER, JO\u00c3O ALVES\/ESO VISIONS<\/p>\n","protected":false},"excerpt":{"rendered":"

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