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HD 40307

HD 40307 is an extrasolar multiplanetary system located 42 light-years away in the southern constellation Pictor (the Easel).
 
The central star is an orange dwarf (spectral type K2.5V) with three fourth of the mass of the Sun and a surface temperature of 5000 kelvins (4700 °C). With a visual magnitude of 7.2, it can easily be seen with binoculars but it is located too much in the south to be observable from Switzerland.
 
Ten years ago this month, Michel Mayor and colleagues, most of them now PlanetS members, announced the discovery of three super-Earths around this star [1]. These planets, HD 40307 b, c and d, have minimum masses of 4, 7 and 9 Earth masses, and orbital periods of 4.3, 9.6 and 20.5 days.
Three additional planets, HD 40307 e, f and g, were announced by Tuomi et al. in 2012 at periods of 34.6, 51.6 and about 200 days [2]. However, a later study by a team including mostly astronomers from Geneva and Bern [3] could only confirm HD 40307 f, a planet with a minimum mass around 4 Earth masses. The other two candidates were not confirmed and are therefore not represented in the animation.
The three studies mentioned above were based on data from the Geneva-built HARPS spectrograph.
[1] Mayor et al., A&A 493:639, 2009 [https://www.aanda.org/articles/aa/pdf/2009/02/aa10451-08.pdf]
see also ESO’s press release [http://www.eso.org/public/news/eso0819/]
[2] Tuomi et al., A&A 549:A48, 2013 [https://www.aanda.org/articles/aa/pdf/2013/01/aa20268-12.pdf].
[3] Díaz et al., A&A 585:A134, 2016 [https://www.aanda.org/articles/aa/pdf/2016/01/aa26729-15.pdf].
Mass(MJ) Radius (RJ) Period (days) Discovery
HD 40307b  0.012 4.3 2008
HD 40307c  0.02 9.6 2008
HD 40307d  0.027 20.4 2008
HD 40307e  0.011 34.6 2012
HD 40307f  0.011 51.6 2012
HD 40307g 0.022 197.8 2012

 

Categories: Planet of the month

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