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The next hunt for exoplanets is officially launched. NASA's Exoplanets Survey Satellite (TESS), launched in April (SN: 5/12/18, p. 7), took his first open-air scientific image and confirmed his first exoplanet.
The "first light" image (nickname of the first useful image of a new telescope) taken on August 7 with the four telescope cameras and broadcast on September 17 shows a star field and two of the satellite galaxies of the Milky Way. Little magellanic clouds. Some stars are so bright that they have saturated the light detector of the telescope, creating streaks of light throughout the image.
TESS spotted the new planet, called Pi Men c, crossing in front of its brilliant 60-light-years star of the Earth and blocking the light of the stars, data collected from July 25 to August 22. This transit revealed that the planet represents 2.14 times the radius of the Earth and revolves around its star every 6.27 days, reports the TESS team on 18 September on arXiv.org.
The researchers then found unseen evidence from the planet in data from the HARPS Spectrograph and the Anglo-Australian Planet Search, which have monitored the star Pi Mensae over the past 20 years. These observations show how the gravity of the planet shoots the star, allowing researchers to determine that the mass of the planet is about 4.8 times greater than that of the Earth. These telescopes had already revealed another planet, this one the size of Jupiter, orbiting Pi Mensae every 5.7 years.
The combination of the mass and the radius of the new planet shows that it has a density similar to that of pure water. "Of course, we should not imagine the planet as a water globe," writes the TESS team. Instead, it probably has a core of iron and rock, surrounded by an ocean or atmosphere of lighter materials like water, methane, hydrogen, and helium.
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