A team of astronomers announces that they have identified three new gas giant exoplanets in orbit around a young star. A planetary system considered very “strange”.
The star, known as CI Tau, is very young: two million years old (comparatively, our star is about 4.6 billion years old). Located at about 500 light-years from Earth, Ci Tau is always surrounded by a vast disk of dust and ice in which objects still form. It is also known to house a first exoplanet – a hot Jupiter, that is to say a gas giant orbiting very close to its star. This first discovery – a hot Jupiter around a star so young – was already surprising. Hence the surprise of astronomers when they discovered three additional worlds.
Based on data from the Atacama Large Millimeter / Submilleter Meter Array (ALMA) in Chile, a team explains that it has indeed identified three distinct gaps in the protoplanetary disk of the young star. These are three periodic dives of luminosity betraying the presence of three new bodies in orbit. These observations therefore bring the number of exoplanets in orbit to four. Besides the number of gas giants around the star, their orbits are also amazing. The two most distant planets gravitate in fact at a distance three times greater than that of Neptune of the Sun (nearly 15 billion km from the star).
Researchers here are simply unable to explain how the outer planets were formed, nor the hot Jupiter in orbit around a star so young. “These discoveries do not necessarily correspond to the models, they explain. Saturn-mass planets are supposed to form by first accumulating a solid nucleus, then bringing a layer of gas over, but these processes are supposed to be very slow at great distance from the star. Most models have trouble forming planets of this mass at this distance.”
Additional research is already planned at different wavelengths to try to learn more about this “mystery” planetary system. The details of the study are reported in the Astrophysical Journal Letters.