CEMP stars: possible hosts to carbon planets in the early Universe

Abstract

We explore the possibility of planet formation in the carbon-rich protoplanetary disks of carbon-enhanced metal-poor (CEMP) stars, possible relics of the early Universe. The chemically anomalous abundance patterns ([C/Fe] ≥ 0.7) in this subset of low-mass stars suggest pollution by primordial core-collapsing supernovae (SNe) ejecta that are particularly rich in carbon dust grains. By comparing the dust-settling timescale in the protoplanetary disks of CEMP stars to the expected disk lifetime (assuming dissipation via photoevaporation), we determine the maximum distance r max from the host CEMP star at which carbon-rich planetesimal formation is possible, as a function of the host star's [C/H] abundance. We then use our linear relation between r max and [C/H], along with the theoretical mass-radius relation derived for a solid, pure carbon planet, to characterize potential planetary transits across host CEMP stars. Given that the related transits are detectable with current and upcoming spacebased transit surveys, we suggest initiating an observational program to search for carbon planets around CEMP stars in hopes of shedding light on the question of how early planetary systems may have formed after the Big Bang.

Dust in brown dwarfs and extrasolar planets

“…These results are not only of interest for planetary atmosphere research but also for modeling the ISM enrichment through AGB star winds and the enrichment of the early universe due to SNe ejecta (e.g. Mashian & Loeb 2016). In particular the in situ formation of carbon-rich planets in the early universe as by-product of CEMP stars would occur at C/O 0 > 10.0 (Table 1 in Mashian & Loeb 2016).…”

“…Mashian & Loeb 2016). In particular the in situ formation of carbon-rich planets in the early universe as by-product of CEMP stars would occur at C/O 0 > 10.0 (Table 1 in Mashian & Loeb 2016).…”

“…We therefore also consider extreme values (C/O 0 =3.0 and 10.0) which are guided by observations of carbon-rich Pop II stars (e.g. Table 1 in Mashian & Loeb 2016 and references therein). The results are summarizes in Table 3 ) and the carbon rich regime (C/O 0 = 1.1, 1.5, 3.0 and 10.0).…”

“…Carbon-rich planets could now form in situ as by-product of carbon-enhanced metal-poor stars (CEMPs), i.e. carbon-rich Pop II stars, as suggested by Mashian & Loeb (2016). Would such planets still have clouds?…”

Habitabilidade cósmica e a possibilidade de existência de vida em outros locais do universo

“…Outros autores ( [8,9,88]) consideram que estes elementos podem ter sido produzidos quando o Universo era ainda mais jovem (com cerca de 30 milhões de anos) e sugerem um enriquecimento de C em estrelas de baixa massa (tipos espectrais K e M), as chamadas "CEMP stars" [89]. Eles também argumentam que, a menos que a habitabilidade em torno de estrelas de baixa massa seja suprimida, a probabilidade de existência de vida, daqui a 10 trilhões de anos, será maior ao redor de estrelas com cerca de 0, 1M .…”