Day 789

Wednesday.

* Chondrite: a stony (non-metallic) meteorites that have not been modified due to melting or differentiation of the parent body.  They are formed when various types of dust and small grains that were present in the early solar system accreted to form primitive asteroids.  They are the most common type of meteorite that falls to Earth (~86%).  Provides important clues for understanding the origin and age of the Solar System, the synthesis of organic compounds, the origin of life or the presence of water on Earth.  One of their characteristics is the presence of chondrules, which are round grains formed by distinct minerals, that normally constitute between 20% and 80% by volume.  Chondrites can be differentiated from iron meteorites due to their low Fe and Ni content.  Other non-metallic meteorites, chondrites, which lack chondrules, were formed more recently.

* Chondrules: round grains found in chondrites.  Chondrules form as a molten or partially molten droplets in space before being accreted to their parent asteroids.  Because chondrites represent one of the oldest solid materials within our Solar System and are believed to be the building blocks of the planetary system, it follows that an understanding f the formation of chondrules is important to understand the initial development of the planetary system.

Science
Solar nebula magnetic fields recorded in the Semarkona meteorite

Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids.  However, there have been no experimental constrains on the intensity of these fields.  Show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54pm21 muT.  This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the sun.  This implies that background B-fields in the terrestrial planet-formation region were likely 5-54 muT, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.

1411.4646
Main-sequence stars masquerading as Young Stellar Objects in the central molecular zone
Koepferl, et al

Estimate the fraction of misclassified "YSOs" to be at least 63%, which suggests that the SFR previously determined from YSOs is likely to be at least a factor of three too high.

Tons of paper dedicated to Michel Henon today: "hommage a Michel Henon".