An ultrahot Neptune in the Neptune desert

About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R⊕), or apparently rocky planets smaller than 2 R⊕. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R⊕ and a mass of 29 M⊕, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0^(+2.7)_(−2.9)% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (V_(mag) = 9.8)

CHEOPS

CHEOPS (CHaracterising ExOPlanet Satellite) is the first S-class mission from ESA, which will be launched in December 2019. CHEOPS’ payload is a telescope of 32 cm aperture. It will perform photometric observation from low Earth orbit to measure transits of already known host stars further characterize already known planetary systems. The mission goals are - to search for shallow transits on stars already known to host planets obtaining a transit signal-to-noise ratio of 5 for an Earth-size planet with a period of 50 days on G5 dwarf stars with V- magnitude brighter than 9th. - to provide precision radii for a number of hot Neptune planets orbiting stars brighter than 12th V magnitude and to search for co-aligned smaller mass planets - to measure the phase modulation due to the different contribution of the dayside of hot Jupiter planets and in some cases to measure the secondary eclipse

Auf der Suche nach Planeten um andere Sonnen

Seit der ersten zweifelsfreien Entdeckung eines extrasolaren Planeten hat sich dieser Zweig der Astronomie stürmisch entwickelt. Mit verschiedenen Methoden sucht man weltweit nach Exoplaneten, jetzt wird mit COROT ein Satellit gestartet, der dieser Aufgabe gewidmet ist. Er soll bei insgesamt 60000 Sternen mit Hilfe der Transitmethode nach Planeten suchen. Mit ihm könnte der erste Gesteinsplanet von der Größe der Erde gefunden werden

Planetary Transits and Oscillations of Stars: PLATO

Up to now, no Earth-like planet in the habitable zone around a sun-like star has been found. The majority of the detected exoplanets lack the full set of bulk parameters as radius, mass, stellar type and age. That is what PLATO is designed for: to find terrestrial planets in the habitable zone and determine their bulk densities with a precision never reached before. PLATO is a M-class mission in ESAs Cosmic Vision Programme 2015-2025. The international PLATO Consortium is lead by DLR (Prof. Heike Rauer). It will be launched in 2026 with an Ariane-6 rocket from Kourou, French Guyana. The mission duration is 4 years, an extension up to 6 years is possible. There are consumables for 8 years

Die Stellung der Erde im Kosmos

Der Nobelpreis für Physik 2019 geht zur einen Hälfte an James Peebles "für theoretische Entdeckungen in der physikalischen Kosmologie" und zur anderen Hälfte gemeinsam an Michel Mayor und Didier Queloz "für die Entdeckung eines Exoplaneten, der einen sonnenähnlichen Stern umkreist"

PLATO: Die Rückkehr zu den hellsten Sternen

Die europäische Weltraumbehörde ESA plant im Jahr 2026 eine neue Mission ins All zu schicken: PLATO, was für »Planetary Transits and Oscillations of Stars« steht. Auf einem Satelliten werden 26 Teleskope zu einem Instrument vereinigt, um Exoplaneten um helle Sterne aufzuspüren. Durch die Kombination unterschiedlicher Methoden werden die Astronomen beurteilen können, wie lebensfreundlich die neuen Welten sind

An ultrahot Neptune in the Neptune desert

About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet1,2. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R⊕), or apparently rocky planets smaller than 2 R⊕. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R⊕ and a mass of 29 M⊕, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite3 revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0+2.7−2.9% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (Vmag = 9.8).<br