The spectral energy distribution of protostars

Aug 06, 2012
The spectral energy distribution of protostars
A simulated image of what a young star looks like in the far infrared. A dark disk is seen edge-on and outflow material is also apparent. A new paper compares models with these simulations to measure their accuracy. Credit: Offner et al., 2012

(Phys.org) -- Stars form when gravitational forces coalesce the gas and dust in interstellar clouds until the material forms clumps dense enough to become stars. Precisely how this happens, however, is still very uncertain. The infall of matter is probably not symmetric, it may be inhibited by the pressure of very hot radiation around the young stellar embryo, or perhaps it is constrained in other ways. These processes enable surrounding material to develop into disks around the stars, and it in turn can evolve into planets. The differences in the conditions are important to our understanding of the formation of our solar system because planets like the Earth are built from just such material that does not make it into the star.

Observing these various processes directly is difficult. Young stars are embedded in obscuring dust, and moreover they are generally far enough away that the imaging ability of instruments is unable to distinguish a star from its disk or surrounding cloud except in a few cases. Instead of relying on pictures, astronomers measure the total energy emitted by the star and its environment across wavelengths from the optical through several decades of infrared into the submillimeter. The so-called "spectral energy distribution (SED)" samples the 's emission at wavelengths where the bulk of its energy lies - in the optical from the star and in infrared bands from dust in the disk or surroundings, with each band highlighting different temperature material. A range of modern space telescopes including the and the Herschel have been used to collect these data.

Astronomers use models to reconstruct from the measured SED the detailed physical processes underway. CfA astronomer Tom Robitaille (who recently left CfA) was one of the most successful people modeling young , and his codes have been widely used for about six years. In the new issue of The , he and CfA astronomer Stella Offner, together with three colleagues, ask the question: How accurate are the models?

To test them, they use a sophisticated simulation of star formation whose results they use to calculate SEDs which they compare with the models. Of course the simulations, too, make approximations and might be neglecting something important, but they provide an excellent verification for most features such as the importance of the viewing angle in determining the observed SED. Their conclusion: Overall the models are very good at determining a young star's evolutionary state, accretion rate, and stellar mass, but are less good in determining the properties of the disk or envelope. The characteristics of the dust are among the parameters that need to be refined in order to improve the modeling. Their work is continuing, and future research will make it possible to infer even more details of stellar evolution from observations of the spectral energy distribution.

Explore further: An old-looking galaxy in a young universe

Related Stories

Making massive stars

Aug 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 ...

Stellar embryos

Jan 23, 2012

(PhysOrg.com) -- Stars form as gravity coalesces the gas and dust in interstellar clouds until the material produces clumps dense enough to become stars. But precisely how this happens, and whether or not ...

Young stars flicker amidst clouds of gas and dust

Feb 29, 2012

(PhysOrg.com) -- Astronomers have spotted young stars in the Orion nebula changing right before their eyes, thanks to the European Space Agency's Herschel Space Observatory and NASA's Spitzer Space Telescope. ...

Imaging a multiple star

Apr 18, 2011

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

Flaring Young Stars

Jan 04, 2010

(PhysOrg.com) -- The constellation of Vela (visible only from the southern hemisphere) contains a set of giant clouds of gas and dust known collectively as the Vela Molecular complex.

Recommended for you

An old-looking galaxy in a young universe

11 hours ago

A team of astronomers, led by Darach Watson, from the University of Copenhagen used the Very Large Telescope's X-shooter instrument along with the Atacama Large Millimeter/submillimeter Array (ALMA) to observe ...

Giant methane storms on Uranus

12 hours ago

Most of the times we have looked at Uranus, it has seemed to be a relatively calm place. Well, yes its atmosphere is the coldest place in the solar system. But, when we picture the seventh planet in our ...

Where do stars form in merging galaxies?

14 hours ago

Collisions between galaxies, and even less dramatic gravitational encounters between them, are recognized as triggering star formation. Observations of luminous galaxies, powered by starbursts, are consistent ...

Could the Milky Way become a quasar?

Feb 27, 2015

A quasar is what you get when a supermassive black hole is actively feeding on material at the core of a galaxy. The region around the black hole gets really hot and blasts out radiation that we can see billions ...

Galactic dinosaurs not extinct

Feb 27, 2015

One of the biggest mysteries in galaxy evolution is the fate of the compact massive galaxies that roamed the early Universe.

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

jsdarkdestruction
1 / 5 (1) Aug 06, 2012
"Precisely how this happens, however, is still very uncertain"
*waits for kevinrtrs to use that statement for a strawman attack on science*
Birger
not rated yet Aug 07, 2012
*waits for kevinrtrs to use that statement for a strawman attack on science*


Ha ha, yes. The article mentions suns... and the sun is involved in climate...therefore scientists know nothing about climate! (sarcasm)

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.