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 .
spectral feature that may be due to methane or ammonia , other anticipated signs of these two compounds went undetected in the observations . The team ’ s spectroscopic observations also indicate that a mixture of water and methane ice grains lie within the circumbinary ring — close enough to the primary stars that the frozen methane must be shielded by dust from direct radiation .
Finally , in addition to determining that star B is an early K-type subgiant , the research revealed variable helium I emission in star B ’ s magnetosphere due to ongoing mass accretion . The 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 Nearinfrared 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 SOFIA 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 .
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 .
8 GeminiFocus January 2017