Thaindian News

Washington, June 12 (IANS) A team led by University of Arizona astronomer Joshua Eisner has observed in unprecedented detail the processes giving rise to stars and planets in nascent solar systems.
The discoveries provide a better understanding of the way hydrogen gas from the protoplanetary disk is incorporated into the star.

They are swirling clouds of gas and dust that feed the growing star in its centre and eventually coalesce into planets and asteroids to form a solar system.

By coupling both Keck telescopes on Mauna Kea in Hawaii with a specifically engineered instrument named ASTRA (Astrometric and phase-Referenced Astronomy), Eisner and his colleagues were able to peer deeply into protoplanetary disks.

The big challenge facing Eisner’s team lies in obtaining the extremely fine resolution necessary to observe the processes that happen at the boundary between the star and its surrounding disk — 500 light years from earth.

“The angular resolution you can achieve with the Hubble Space Telescope is about 100 times too coarse to be able to see what is going on just outside of a nascent star not much bigger than our sun,” said Eisner, assistant professor at University of Arizona’s Steward Observatory.

In other words, even a protoplanetary disk close enough to be considered in the neighbourhood of our solar system would appear as a featureless blob.

Combining the light from the two Keck telescopes provides an angular resolution finer than Hubble’s. Eisner and his team used a technique called spectro-astrometry to boost resolution even more.

By measuring the light emanating from the protoplanetary disks at different wavelengths with both Keck telescope mirrors and manipulating it further with ASTRA, the researchers achieved the resolution needed to observe processes in the centres of the nascent solar systems.

Protoplanetary disks form in stellar nurseries when clouds of gas molecules and dust particles begin to collapse under the influence of gravity.

Initially rotating slowly, the cloud’s growing mass and gravity cause it to become more dense and more compact. The preservation of rotational momentum speeds up the cloud as it shrinks, much like a figure skater spins faster as she tugs in her arms.

The centrifugal force flattens the cloud into a spinning disk of swirling gas and dust, eventually giving rise to planets orbiting their star in roughly the same plane, said a University of Arizona release.

Eisner’s team pointed the telescopes at 15 protoplanetary disks with young stars varying in mass between one half and 10 times that of our sun. This sample of disks, all located in our own galaxy, the Milky Way, represents by far the largest of its kind.