'Hot Super-Earths': Spanish scientists find new planetary systems

ASTROPHYSICISTS in Spain have discovered two new planetary systems circulating around red dwarf stars, made up of 'Earths' and 'Super-Earths'.

The National Research Council (CSIC), led by the Andalucía Astrophysics Institute (IAA) in the province of Granada, detected the planets using the telescope Carmenes at the observatory in Calar Alto (Almería province), and says what they have seen 'reinforces the idea that dwarf stars tend to house rocky planets'.

Research team leader Pedro J Amado says the 'current conception' about how low-mass planets are formed in orbits close to very small stars 'points to the fact that these may be abundant in number', with an average of 'at least one planet per star'.

“Despite this abundance, though, we have very little data on the density of these planets which would enable us to work out their composition,” Dr Amado says.

The new systems, in which the team has discovered 'three hot planets', orbit the dwarf stars G264-012 and GI393.

Two planets with a minimum mass of at least 2.5 to 3.8 times that of Earth have been identified, and they take 2.3 and 8.1 Earth days to orbit their star, so a 'day' on the latter planet would be just over a week in our own terms.

The planet orbiting GI393 takes exactly one Earth week to complete a full 'day', and is said to be at least 1.7 times the density of our planet.

According to the CSIC, the three planets fall into the category of 'Hot Earths' and 'Hot Super-Earths', where the temperatures reached are too high to allow the presence of water in liquid form on their surfaces.

This means, in theory, they do not have the necessary conditions for life on them.

Dr Amado says that to be able to understand how the planetary systems his team are observing form and evolve, they would need 'robust statistics' about how many planets there are and information about their density and 'the architecture of the planetary systems'.

That way, the researchers would be able to explain those which do not fit into known planetary mechanisms, such as the GJ3512 system also found via Carmenes and which features a giant planet orbiting a very small dwarf star; also, it would enable them to confirm or refute their hypothesis that dwarf stars tend to house multiple planetary systems.

Additionally, their work has allowed them to discover a new factor that appears to influence how planets are detected: The planet orbiting star GI393 had gone unnoticed during a number of observatory campaigns, even using telescopes known to be extremely efficient at planet-spotting, and it seems that red dwarf stars display 'intense activity' – in the form of fiery explosions or 'sun storms' – which often mask the signal of planets circulating around them.

The last few observation campaigns were carried out during times of 'high activity', Dr Amado explains.

Planets orbiting dwarf stars are therefore easier to spot at times of low activity, or where the stars themselves are not highly active, the team leader says.