Weekly Science Update

Wednesday, February 07, 2007
The Birth of Twins
More than about half of all stars roughly similar to the Sun or larger (in mass) are part of multiple systems -- binary stars, or even triplets, that orbit around one another. This tendency reflects the conditions that existed when stars like the Sun were born, since most probably such stars were born as multiplets and did not pair up later on in their lives. The local conditions in turn reveal the prevailing environment when planets (if any) form. If, for example, orbiting binary stars tend to disrupt the formation of any planets around them, then our Sun's family of planets might be a rarer phenomenon than currently envisioned.

SAO astronomers Todd Hunter, David Wilner, Qizhou Zhang, and Paul Ho, along with six of their colleagues, have used SAO's Submillimeter Array (SMA) to probe a newly formed, massive star and its environment. The SMA, which can obtain very sharp images of cool dust and gas in the environment of young stars, revealed the presence of two clumps where a single star was thought to reside. But in principle these two objects might not be physically related.

In order to study the pair more carefully, the scientists had to utilize some clever technical tricks. Normally distant quasars are used as calibration objects for telescope arrays like the SMA that combine the light from multiple telescopes in order to achieve their precision -- but there were no sufficiently bright quasars accessible for this project. Instead, the astronomers calibrated on the emission from water masers present in a relatively nearby region, and they verified the stability of the masers' properties by a second level of checks against hot dust around a bright reference star. With these reliable measurements the team was able to measure the total mass of the gas and dust in the source -- about sixty solar-masses worth, or just about enough to bind the two objects together gravitationally. The results not only help to identify the birth of a possible, massive twin, but also illustrate the success of innovative techniques that are developed to capitalize on as new astronomical instruments used to peer into the heavens.


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