Shedding light on the mystery of matter accretion in young stars

November 3, 2017, Institut national de la recherche scientifique
Shedding light on the mystery of matter accretion in young stars
Credit: Institut national de la recherche scientifique

An international team of researchers from multiple institutions, including INRS, is shedding light on the mystery of matter accretion in young stars. Published in the November 1, 2017 Science Advances online journal, their discovery helps explain how matter accumulates on the surface of a young star and reconciles the theory behind and observations on the accretion process—a matter of debate among astrophysicists because of the limited number of theoretical models and actual observations.

An experiment replicating the phenomenon on a star was conducted in a laboratory. Researchers took a close look at what happens when a laser-produced column of plasma impacts a solid obstacle in the presence of an . X-ray emissions measurements verified the presence of an envelope of plasma around the core of the accretion zone of the matter on the star's surface. Discovery of the envelope allows researchers to accurately calculate the matter accretion rate.

The importance of this discovery lies in the fact that a star is born, grows, reaches adult size, and then dies either by exploding or by collapsing in on itself to have much less volume but much greater density. Stars have a lifespan like any living thing. The adult phase—like our sun is in—lasts for many billions of years. Outside the birth of a planet (like Earth) or the appearance of life, it is a relatively quiet time in the life of a star.

Physicists are more interested in the birth and death of stars—these are defining moments. By looking at the emission of x-rays from the surface, scientists can also determine the rate at which grow under the influence of gravity as they pull in the interstellar surrounding them. To accurately interpret these x-rays, scientists must ensure they are not being obscured by something—hence the importance of the discovery of an envelope.

This video demonstrates a column of interstellar matter falling onto a star being formed, through the star’s surrounding matter. The dark blue on the left is the density of the matter and the red on the right is the temperature. The column of matter (yellow for density and light blue for temperature) comes from the top of the screen and collides with the star’s surface (at the bottom of the screen). The time-lapse video shows the gradual formation of an envelope arounds the accretion zone (point of impact of the interstellar matter on the star's surface). The envelope is denser and colder than the matter that naturally surrounds the star, concealing some of the x-rays emitted from the accretion zone.  Knowing that this envelope exists, scientists can measure the x-rays to accurately calculate the rate of accretion of matter on the star’s surface. Credit: Institut national de la recherche scientifique

Explore further: First clear image made of accretion disk surrounding young star

More information: Guilhem Revet et al, Laboratory unraveling of matter accretion in young stars, Science Advances (2017). DOI: 10.1126/sciadv.1700982

Related Stories

What are neutron stars?

October 16, 2017

Thrilled physicists and astronomers announced Monday the first-ever observation of the merger of two neutron stars, one of the most spectacularly violent phenomena in the Universe.

Making massive stars

August 29, 2011

How do massive stars form? Stars with more than about eight times as much mass as the sun are arguably the most important actors in the universe. Although they live only hundreds of millions of years, they are much hotter ...

Fragments falling onto the Sun

July 1, 2013

( —Stars form as gravity coalesces the gas and dust in an interstellar cloud until the material develops clumps dense enough to become stars. Even after a star begins to burn its nuclear fuel it continues to grow ...

Imaging a multiple star

April 18, 2011

( -- Multiple stars - binaries, triplets, or perhaps more stars, that orbit each other - are unique laboratories into the interactions between stars and their early environments.

Recommended for you

Making stars when the universe was half its age

January 18, 2019

The universe is about 13.8 billion years old, and its stars are arguably its most momentous handiwork. Astronomers studying the intricacies of star formation across cosmic time are trying to understand whether stars and the ...

Saturn hasn't always had rings

January 17, 2019

One of the last acts of NASA's Cassini spacecraft before its death plunge into Saturn's hydrogen and helium atmosphere was to coast between the planet and its rings and let them tug it around, essentially acting as a gravity ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) Nov 03, 2017
Amusing! Modeling a "stream" of plasma and omitting gravity to explain the accretion process. Kudos to them for actually doing lab work rather than the usual thought experiments.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.