LIFETIME AND SPECTRAL EVOLUTION OF A MAGMA OCEAN WITH A STEAM ATMOSPHERE: ITS DETECTABILITY BY FUTURE DIRECT IMAGING

Keiko Hamano, Hajime Kawahara, Yutaka Abe, Masanori Onishi, Joji Hashimoto

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

We present the thermal evolution and emergent spectra of solidifying terrestrial planets along with the formation of steam atmospheres. The lifetime of a magma ocean and its spectra through a steam atmosphere depends on the orbital distance of the planet from the host star. For a Type I planet, which is formed beyond a certain critical distance from the host star, the thermal emission declines on a timescale shorter than approximately 106 years. Therefore, young stars should be targets when searching for molten planets in this orbital region. In contrast, a Type II planet, which is formed inside the critical distance, will emit significant thermal radiation from near-infrared atmospheric windows during the entire lifetime of the magma ocean. The Ks and L bands will be favorable for future direct imaging because the planet-to-star contrasts of these bands are higher than approximately 10-7-10-8. Our model predicts that, in the Type II orbital region, molten planets would be present over the main sequence of the G-type host star if the initial bulk content of water exceeds approximately 1 wt%. In visible atmospheric windows, the contrasts of the thermal emission drop below 10-10 in less than 105 years, whereas those of the reflected light remain 10-10 for both types of planets. Since the contrast level is comparable to those of reflected light from Earth-sized planets in the habitable zone, the visible reflected light from molten planets also provides a promising target for direct imaging with future ground- and space-based telescopes.

Original languageEnglish
Article number216
JournalAstrophysical Journal
Volume806
Issue number2
DOIs
Publication statusPublished - Jun 20 2015

Fingerprint

steam
magma
planets
oceans
planet
atmospheres
life (durability)
atmosphere
ocean
stars
atmospheric windows
thermal emission
orbitals
terrestrial planets
thermal radiation
ultrahigh frequencies
thermal evolution
telescopes
near infrared
timescale

Keywords

  • Infrared: planetary systems
  • Planets and satellites: terrestrial planets
  • Radiative transfer

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

LIFETIME AND SPECTRAL EVOLUTION OF A MAGMA OCEAN WITH A STEAM ATMOSPHERE : ITS DETECTABILITY BY FUTURE DIRECT IMAGING. / Hamano, Keiko; Kawahara, Hajime; Abe, Yutaka; Onishi, Masanori; Hashimoto, Joji.

In: Astrophysical Journal, Vol. 806, No. 2, 216, 20.06.2015.

Research output: Contribution to journalArticle

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