John Blakeslee
Science Highlights
GNIRS time-sequence spectra trace onset of dust and CO
production in a nearby core-collapse supernova, GMOS-South
monitors orbital motion to determine the mass of a record-
setting ultra metal-poor star, and archival NICI data provide first
epoch observations of the first exoplanet found within the gap
of a transition disk.
Nearby Supernova Illuminates Early Origins of Distant Dust
Interstellar dust constitutes about 1% of the mass of interstellar matter in the Milky Way.
Most of this dust is thought to originate in intermediate-mass evolved stars that ejected
their outer layers as red giants or thermally pulsating asymptotic giant branch stars. Once
the ejecta cool to temperatures lower than about 2,000 K, dust particles inevitably start
to form from carbon and other elements. However, this process cannot explain the large
amounts of dust observed in some galaxies in the early Universe, since such stars would
not have had time to evolve to the dust-producing stage. The only viable explanation
for the dust observed in such galaxies is production in the ejecta of core-collapse super-
novae (ccSNe), and this can be tested through careful observations of ccSNe in the local
Universe. Until now, detailed evolution of dust production in such supernovae, which can
take place over several years, has only been followed in one object, SN 1987A in the Large
Magellanic Cloud.
However, the recent explosion of SN 2017eaw in the nearby galaxy NGC 6946 has provided
another excellent opportunity to follow that evolution in detail over an extended period.
NGC 6946 is only about 7 megaparsecs away and is popularly known as the Fireworks Gal-
axy because it is a prodigious producer of supernovae, all of the core-collapse variety. SN
2017eaw was discovered in May 2017, just as its host galaxy became observable in the east-
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GeminiFocus
January 2019