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With simulations that go into finer details than ever before, Brooke Polak of the University of Heidelberg and Hubert Klahr at the Max Planck Institute for Astronomy (MPIA) have modeled a key phase in the formation of planets in our solar system: the way that centimeter-size pebbles aggregate into so-called planetesimals tens to hundreds kilometers in size. The simulation reproduces the initial size distribution of planetesimals, which can be checked against observations of present-day asteroids. It also predicts the prevalence of close binary planetesimals in our solar system.

In a new study published on arXiv and accepted for publication in The Astrophysical Journal, astrophysicists Brooke Polak from the University of Heidelberg and Hubert Klahr from the Max Planck Institute for Astronomy used simulations to derive key properties of so-called planetesimals—the intermediate-size bodies from which planets formed in our solar system roughly 4.5 billion years ago.

Using an innovative method for simulating planetesimal formation, the two researchers were able to predict the initial size distribution of planetesimals in our solar system: how many are likely to have formed in the different “size brackets” between roughly 10 km and 200 km.

Think of bringing a pot of water to the boil: As the temperature reaches the boiling point, bubbles form in the water, burst and evaporate as the water boils. This continues until there is no more water changing phase from liquid to steam.

This is roughly the idea of what happened in the very early universe, right after the Big Bang, 13.7 billion years ago.

The idea comes from particle physicists Martin S. Sloth from the Center for Cosmology and Particle Physics Phenomenology at University of Southern Denmark and Florian Niedermann from the Nordic Institute for Theoretical Physics (NORDITA) in Stockholm. Niedermann is a previous postdoc in Sloth’s research group. In this new scientific article, they present an even stronger basis for their idea.

An international team of space scientists reports that the moon exerts a tidal impact on the plasmasphere. For their paper published in the journal Nature Physics, the group used data from multiple spacecraft over a nearly 40-year period to measure tidal perturbations in the plasmapause. Balázs Heilig, with the Institute of Earth Physics and Space Science, in Hungary, has published a News & Views piece in the same journal issue, explaining the nature of the plasmasphere and outlining the work in this new effort.

Early scientists found a connection between the tides and the movement of the thousands of years ago. More recent evidence suggests the moon’s pull acts on the ionosphere as well. In this new study, the researchers wondered if the moon might also have an impact on the plasmasphere.

The plasmasphere is a toroidal mass of plasma that surrounds the Earth. It lies beyond the ionosphere and is made up mostly of electrons and protons. Its particles are charged by the ionosphere, and its outer boundary is known as the plasmapause.

On Jan. 16, 2003 space shuttle Columbia left Earth for its 28th and last flight. Even though at the time building the International Space Station was the main goal of the shuttle program, STS-107 (Columbia’s final mission) emphasized pure research, according to Space.com.

The seven-member crew — Rick Husband, commander; Michael Anderson, payload commander; David Brown, mission specialist; Kalpana Chawla, mission specialist; Laurel Clark, mission specialist; William McCool, pilot; and Ilan Ramon, payload specialist from the Israeli Space Agency — had spent 24 hours a day doing science experiments in two shifts.

The seven astronauts on board Columbia were killed on Feb. 1, 2003 when the space shuttle broke up while it was returning to Earth.

Seqenenre Tao was the pharaoh who ruled southern Egypt in the late 17th dynasty, roughly between 1,558 and 1,553 BC.

That was a troubled time. The Hyksos (whose name in ancient Egyptian was Heqau-khasut, “the rulers of foreign lands”) occupied the northern part of Egypt and took Avaris (present-day Tell el Dabaa) as their capital during a time called the “second intermediate period” (1650−1550 BC).

Although the pharaohs maintained power over the south (with capital in Thebes), the entire territory was forced to pay tribute to the invaders.

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