ACTIVITY & PLANETS

The effect of stellar magnetic activity on protoplanetary discs and exoplanet detection

 Partecipanti

Mappa

 Word cloud

Esplora la "nuvola delle parole (Word Cloud) per avere un'idea di massima del progetto.

 Obiettivo del progetto (Objective)

'Many cool stars are born as rapid rotators, and therefore with a strong dynamo created magnetic field, which manifests itself as a high level of activity including strong flares and coronal mass ejections. This is the environment in which planets are formed, and it is therefore unavoidable that this activity has a significant impact on the formation and evolution of planetary systems. The phenomena caused by stellar activity can also have similar effects on stellar brightness and radial velocity as orbiting planets, making it at times difficult to distinguish between planets and activity signatures, especially when using radial velocity searches to find small Earth sized planets. Today we have a unique opportunity to address these points with the new upcoming European and global observational facilities (Atacama Large Millimetre/sub-millimetre Array and Stellar Observations Network Group). In this project we suggest two main lines of investigation: 1) Constructing a freely available database on expected effects of the activity on the detectability of the exoplanets using different methods. We will build a realistic model of activity patterns on different types of stars and using large range of stellar parameters. This model will be used to probe different activity cases, resulting in a database of activity patterns and likelihood of them mimicking different types of exoplanets. This will be crucial for detectability of small, Earth mass, planets using long-term radial velocity measurements with SONG. 2) Studying the effect of the stellar magnetic activity on the protoplanetary discs. By using mid-infrared and sub-millimetre observations of active and non-active young stars with discs a comparison of the disc properties in these two types of stars can be made. We will study the dust properties in the discs and investigate whether the additional heating from magnetic activity significantly changes the dust constitution, thus affecting the planet formation process.'

Introduzione (Teaser)

Astronomers have located hundreds of planets outside of the solar system. EU-funded researchers studied how stellar activity shapes the environment of these exoplanets, giving rise to a new perspective about magnetic phenomena.

Descrizione progetto (Article)

The "jitter" arising from the star's magnetic activity is very similar in amplitude to signals caused by orbiting low-mass planets. Disentangling these signals is the biggest challenge in the detection of exoplanets based on the radial velocity profiles.

Researchers working on 'The effect of stellar magnetic activity on protoplanetary discs and exoplanet detection' (ACTIVITY & PLANETS) project focused on the magnetically active regions such as dark spots on the stellar surface. The Sun's activity is well known and therefore was selected by project scientists to estimate the velocity variations produced by spots drifting across the face of the Sun. Their investigations were then extended to similar stars, which are of interest in the quest for an Earth-like planet.

Specifically, the jitter in radial velocity measurements was estimated from the continuum light curve of the Sun based on distortions of emission lines caused by spots. Solar observations were used by the project team as the starting point. Photometric proxies were then identified which make it possible to remove stellar activity contribution from exoplanet velocity profiles.

A combination of observations in mid-infrared and sub-millimetre wavelengths was used to study the effects of stellar magnetic activity on the first stages of planets' formation. Newly formed stars in the Orion nebula cluster which were surrounded by a swirling disc of dust and gas were selected. ACTIVITY & PLANETS scientists looked for the effects of X-ray emissions on disc chemistry.

It is well established that the tiny solids in the disc coalesce to create rocky 'planetesimals' that collide and grow to eventually form planets. However, the ACTIVITY & PLANETS scientists' findings suggest that the disc influenced by X-ray emissions is following a slightly different route to making planets. This work will allow astronomers to re-evaluate the magnetic activity on the surface of stars, providing more insight into the planet-building process.