team ’ s paper is accepted for publication in The Astrophysical Journal ( view here ).
High-mass Young Stellar Objects : Are all Stars Created Equal ?
A team of astronomers using the Gemini Near-infrared Integral Field Spectrograph ( NIFS ) on Gemini North have found the strongest evidence yet that massive stars form in much the same way as do their lower-mass brethren .
In addition to the Gemini observations , the work includes data from NASA ’ s SO- FIA airborne observatory , Calar Alto Observatory , and the European Southern Observatory . The results show that when massive stars form , they consume chunks of their surrounding accretion disks , leading to episodic explosive outbursts — much like those known to occur during the formation of average mass stars like our Sun ( only more intense ). This finding may have a profound impact on the way some astronomers believe massive stars grow , namely by the fusion of less massive stars .
The international team of astronomers , led by Alessio Caratti o Garatti of the Dublin Institute for Advanced Studies in Ireland , published its work in the November 14th issue of the journal Nature Physics ( available here ). It was thought that an accretion disk could not survive around a higher mass star due to the star ’ s strong radiation pressure , and thus it would not be a viable mechanism for producing the most massive stars , some of which can exceed 50-100 solar masses .
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The developing star observed in this study , S255IR NIRS 3 ( Figure 2 ), lies some 6,000 light years distant and has a mass estimated at about 20 solar masses . The Gemini observations reveal that the explosive outburst ’ s source is a huge clump of gas , probably about twice the mass of Jupiter , accelerated to supersonic speeds and ingested by the forming star . The team estimates that the outburst began about 16 months ago and appears to still be active , albeit much weaker .
Cluster ’ s Advanced Age is in Razor-sharp Focus
Researchers using the Gemini Multi-conjugate adaptive optics System ( GeMS ), combined with the Gemini South Adaptive Optics Imager ( GSAOI ), probed the depths of the highly compact globular cluster 6624 ( Figure 3 ). These data reveal pinpoint star images with a uniformity across the crowded field , allowing the team to perform precise photometry deep into the cluster ’ s crowded core .
The team also detected a clear “ main-sequence knee ” ( Figure 3 , inset ); this distinctive bend in the evolutionary track of low mass main-sequence stars is extremely difficult to detect without ultra-precise photometry . Indeed , this is the first time the feature has been identified in this globular cluster , and it allowed the team to determine the cluster ’ s age with extremely high precision : about 11.5- 12.5 billion years .
GeminiFocus
Figure 2 . Gemini post outburst K-band NIFS spectrum ( black at top ) of the redshifted outflow cavity of S255IR NIRS 3 . The pre-outburst spectrum obtained with SINFONI / VLT is shown in red at bottom . The Gemini spectrum in the outburst phase shows a large number of emission lines typical of disk-mediated accretion outbursts .
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