CFHT: Newborn Giant Planet Grazes Its Sun

[bystander]

Newborn Giant Planet Grazes Its Sun
Canada France Hawaii Telescope | 2016 June 20

[img3="Artist's impression of a young giant planet in the immediate vicinity of a star in formation. (Credit: Mark Garlick)"]http://news.yorku.ca/files/Artist-view- ... 00x479.jpg[/img3][hr][/hr]

For the last 20 years the giant planets known as hot Jupiters have presented astronomers with a puzzle. How did they settle into orbits 100 times closer to their host stars than our own Jupiter is to the Sun? An international team of astronomers has announced this week the discovery of a newborn hot Jupiter, orbiting an infant sun -- only 2 million years old, the stellar equivalent of a week-old human baby. The discovery that hot Jupiters can already be present at such an early stage of star-planet formation represents a major step forward in our understanding of how planetary systems form and evolve.

For this discovery, the team monitored a 2-million-year-old infant star called V830 Tau, located in the Taurus stellar nursery, some 430 light-years away. Over the 1.5 months of the campaign, a regular 4.9-day “wobble” in the velocity of the host star revealed a giant planet almost as massive as Jupiter, orbiting its host star at a distance of only one-twentieth that of the Sun-to-Earth distance. “Our discovery demonstrates for the first time that such bodies can be generated at very early stages of planetary formation, and likely play a central role in shaping the overall architecture of planetary systems,” explains Jean-François Donati, CNRS astronomer at IRAP/OMP and lead author of a new paper in the current issue of the journal Nature.

The team used the twin spectropolarimeters ESPaDOnS and Narval to monitor V830 Tau for a total of 47 hours. ESPaDOnS is mounted at the 3.6-meter Canada-France-Hawaii Telescope (CFHT) on Maunakea and can be fiber-fed from either CFHT itself, or via GRACES, a 300-m optical-fiber link from the nearby 8-meter Gemini North telescope. The team used ESPaDOnS in both modes, providing the opportunity to monitor the star using light from the Gemini North telescope when the instrument was unavailable at CFHT. The team also used Narval, mounted at the 2-meter Télescope Bernard Lyot (TBL) atop Pic du Midi in the French Pyrénées. “Using all three telescopes was essential for monitoring regularly V830 Tau throughout our campaign and for detecting its giant planet” stresses Lison Malo, CFHT astronomer, a coauthor of the study and leader in coordinating the observations. ...

Newborn giant planet found orbiting an infant sun
York University, Canada | 2016 June 20

Newborn giant planet grazes its star
National Center for Scientific Research | 2016 June 20

A hot Jupiter orbiting a 2-million-year-old solar-mass T Tauri star - J. F. Donati et al

• Nature (online 20 June 2016) DOI: 10.1038/nature18305

[neufer]

The ejection of a bubble of hot gas from XZ Tauri, a binary system of T Tauri stars. The scale is much larger than the Solar System.

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<<T Tauri stars (TTS) are a class of variable stars named after their prototype – T Tauri. They are found near molecular clouds and identified by their optical variability and strong chromospheric lines. T Tauri stars are pre-main-sequence stars in the process of contracting to the main sequence along the Hayashi track, a luminosity-temperature relationship obeyed by infant stars of less than 3 solar masses (M_☉) in the pre-main-sequence phase of stellar evolution. It ends when a star of 0.5 M_☉ develops a radiative zone, or when a larger star commences nuclear fusion on the main sequence.

T Tauri stars are the youngest visible F, G, K, M spectral type stars (<2 M_☉). Their surface temperatures are similar to those of main-sequence stars of the same mass, but they are significantly more luminous because their radii are larger. Their central temperatures are too low for hydrogen fusion. Instead, they are powered by gravitational energy released as the stars contract, while moving towards the main sequence, which they reach after about 100 million years. They typically rotate with a period between one and twelve days, compared to a month for the Sun, and are very active and variable.

There is evidence of large areas of starspot coverage, and they have intense and variable X-ray and radio emissions (approximately 1000 times that of the Sun). Many have extremely powerful stellar winds; some eject gas in high-velocity bipolar jets. Another source of brightness variability are clumps (protoplanets and planetesimals) in the disk surrounding T Tauri stars.

[b][color=#0000FF]Alfvén S-waves, flow from the base of black hole jets. An Alfvén wave is a type of magnetohydrodynamic wave in which ions oscillate in response to a restoring force provided by an effective tension on the magnetic field lines.[/color][/b]

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Their spectra show a higher lithium abundance than the Sun and other main-sequence stars because lithium is destroyed at temperatures above 2,500,000 K. From a study of lithium abundances in 53 T Tauri stars, it has been found that lithium depletion varies strongly with size, suggesting that "lithium burning" by the P-P chain, during the last highly convective and unstable stages during the later pre–main sequence phase of the Hayashi contraction may be one of the main sources of energy for T Tauri stars. Rapid rotation tends to improve mixing and increase the transport of lithium into deeper layers where it is destroyed. T Tauri stars generally increase their rotation rates as they age, through contraction and spin-up, as they conserve angular momentum. This causes an increased rate of lithium loss with age. Lithium burning will also increase with higher temperatures and mass, and will last for at most a little over 100 million years.

Roughly half of T Tauri stars have circumstellar disks, which in this case are called protoplanetary discs because they are probably the progenitors of planetary systems like the Solar System. Circumstellar discs are estimated to dissipate on timescales of up to 10 million years. Most T Tauri stars are in binary star systems. In various stages of their life, they are called Young Stellar Objects (YSOs). It is thought that the active magnetic fields and strong solar wind of Alfvén waves of T Tauri stars are one means by which angular momentum gets transferred from the star to the protoplanetary disc. A T Tauri stage for the Solar System would be one means by which the angular momentum of the contracting Sun was transferred to the protoplanetary disc and hence, eventually to the planets.>>