Accretion tagged posts

Southwest Research Institute scientists developed a new process in planetary formation modeling that explains the size and mass difference between the Earth and Mars. Mars is much smaller and has only 10 percent of the mass of the Earth. Conventional solar system formation models generate good analogs to Earth and Venus, but predict that Mars should be of similar-size, or even larger than Earth. Credit: Image Courtesy of NASA/JPL/MSSS

Using a new process in planetary formation modeling, where planets grow from tiny bodies called ‘pebbles,’ scientists can explain why Mars is so much smaller than Earth. This same process also explains the rapid formation of the gas giants Jupiter and Saturn, as reported earlier this year.

“This numerical simulation actually reproduces the structure of the in...

An accretion disc around a black hole. Credit: Image courtesy of University of Leicester

Astronomers have discovered a previously unknown link between the way young stars grow and the way black holes and other exotic space objects feed from their surroundings. The study shows how the ‘flickering’ in the visible brightness of young stellar objects (YSOs) – very young stars in the final stages of formation – is similar to the flickering seen from black holes or white dwarfs as they violently pull matter from their surroundings ie accretion.

The relatively cool accretion discs around young stars, whose inner edges can be several times the size of the Sun, show the same behaviour as the hot, violent accretion discs around planet-sized white dwarfs, city-sized black holes and supermassive black...

Figure showing the different size scales of accreting objects. Credit: Simone Scaringi

Accretion is the growth in mass of an object by gravitationally collecting material from its surroundings. “In our paper (Astrophysical accretion is a universal process in objects from proto-stars to supermassive black holes), we discovered a relationship that spans the range of different types of accreting objects, from proto-stars, much like our sun was at its time of birth, to white dwarfs to supermassive black holes with a billion times the mass of the sun located in galaxies millions of light-years away,” Maccarone said.

“In these systems there is some characteristic timescale for the variability – typically the large brightenings and fadings occur with that timescale...