David Appell errs in attributing the discovery of dark energy so completely to Saul Perlmutter’s Supernova Cosmology Project (SCP) team in “Dark Forces at Work” [Insights]. The SCP made real contributions to the discovery of dark energy, but other groups had solved some of these problems earlier.
In 1988 a Danish team searched for distant supernovae using methods anticipating those of the SCP. And the program of supernova discovery for nearby objects at Cerro Tololo Inter-American Observatory in Chile formed the basis for using supernovae as distance indicators, not the robotic search Perlmutter worked on. The SCP did publish a result in July 1997 that claimed supernova observations were unlikely to be consistent with dark energy, but our High‑Z Supernova Search Team developed superior methods for dealing with dust, published in 1996. With careful observation of supernovae, we were confident that we saw cosmic acceleration, which we announced in February 1998. A paper detailing our work was submitted to the Astronomical Journal in March 1998 and appeared in print before the SCP paper was submitted.
Everybody has a lot to be proud of, but credit should be given where it is due.
--Robert P. Kirshner
APPELL REPlIES: Kirshner is not entirely correct and, as a member of the High-Z team, perhaps not entirely objective. The Danish team did perform consequential early measurements, but only on one supernova and too late to obtain its peak brightness. Both the SCP and High-Z teams did important work and exchanged vital data and insights in both directions. But it is undisputed that the SCP announced its discovery first, on January 9, 1998, at a meeting of the American Astronomical Society. In Kirshner’s book The Extravagant Universe (Princeton University Press, 2002), he describes the two teams’ relationship as “getting it first” versus “getting it right.”
I am sure that history will acknowledge the contributions of both teams in the final analysis.