Historical research guide · 0812 · 1998

Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant

Adam G. Riess · Alexei V. Filippenko · Peter Challis · Alejandro Clocchiatti · Alan Diercks · Peter M. Garnavich · Ron L. Gilliland · Craig J. Hogan · Saurabh Jha · Robert P. Kirshner · B. Leibundgut · M. M. Phillips · David Reiss · Brian P. Schmidt · Robert A. Schommer · R. Chris Smith · J. Spyromilio · Christopher Stubbs · Nicholas B. Suntzeff · John Tonry

In one minute

Type Ia supernovae all detonate at close to the same brightness, so how faint one looks tells you how far away it sits. Adam Riess and the High-Z Supernova Search Team measured ten new ones between redshift 0.16 and 0.62, combined them with six more of their own and thirty-four nearby ones, and found the distant explosions 10 to 15 per cent farther away than a universe braked only by its own matter allows. The straightforward reading is that the expansion is speeding up, and that something with negative pressure is doing the work. The paper names it in its opening paragraphs: an energy of the vacuum, Einstein’s cosmological constant. Two independent light-curve fitting methods agree. Assuming a flat universe, they put roughly two-thirds to five-sixths of everything into that vacuum term, and rule out a universe closed by ordinary matter at seven to nine sigma. Riess and colleagues then spend a whole section trying to kill their own result with dust, evolution and selection effects, and cannot.

Connection

This is the measurement that turned the energy of empty space from a bookkeeping term into the dominant component of the universe. Chapter 2 takes it as the observational anchor for a real, energetic vacuum, and chapter 13 treats the number it delivers as the first hard figure any unified account of zero-point energy has to reproduce.

From the source

Ten new type Ia supernovae between redshift 0.16 and 0.62, combined with six earlier High-Z Team objects and thirty-four nearby supernovae, give luminosity distances that are on average 10 to 15 per cent — 0.25 to 0.28 magnitudes — greater than a low mass-density universe with no cosmological constant predicts.Abstract; Sect. 5, Discussion, second paragraph
The vacuum energy density is inconsistent with zero at the 3.0 sigma to 4.0 sigma confidence level, and the expansion is currently accelerating at the 2.8 sigma to 3.9 sigma level, for the two independent light-curve fitting methods, assuming only that the mass density is not negative.Sect. 6, Conclusions 1 and 2
Imposing a spatially flat universe gives a vacuum energy density of 0.68 plus or minus 0.10 by the MLCS method and 0.84 plus or minus 0.09 by template fitting, and rules out a universe closed by ordinary matter at the 7 sigma to 9 sigma level.Sect. 4, paragraph following Eq. (14); Table 8
The same data give a dynamical age for the universe of 14.2 plus or minus 1.5 billion years, including systematic uncertainties, subject to the zero point of the Cepheid distance scale used for three nearby host galaxies.Sect. 6, Conclusion 4
Grey extinction, sample selection bias, progenitor and metallicity evolution, a local void, weak gravitational lensing and sample contamination were each estimated, and none of them reconciles the data with zero vacuum energy and a decelerating expansion. The detection is limited by systematic rather than statistical error.Sect. 5; Sect. 6, Conclusion 6
The authors name the sharpest independent test ahead: supernovae constrain the difference between mass density and vacuum energy density, while the angular scale of the first Doppler peak in the cosmic microwave background constrains their sum, so the two constraints are nearly orthogonal and their intersection would fix both.Sect. 5, final three paragraphs

The way in

https://arxiv.org/abs/astro-ph/9805201

Historical source-access record. This guide links to the original; it does not reproduce the paper text.

LICENCE CHECK, 2026-09-08. The preprint arXiv:astro-ph/9805201v1, posted 15 May 1998, carries the arXiv assumed licence for postings of 1991 to 2003 — checked on the arXiv abstract page — which is not a Creative Commons grant and does not permit redistribution. The version of record is The Astronomical Journal 116, 1009 (1998). No Creative Commons statement appears in the text. So this sheet carries the summary, the claims and the authors’ own abstract, and sends the reader to the source, where the full 28-page paper with its appendices and tables is free to read. The abstract below is the arXiv posting’s, with the mathematical symbols for less than and greater than written out as words. This paper is the High-Z Supernova Search Team’s result; the independent Supernova Cosmology Project result of Perlmutter and colleagues followed in 1999, and the two together won the 2011 Nobel Prize in Physics for Riess, Schmidt and Perlmutter. Section and equation numbers in the claims are the preprint’s. The registry record listed eight of the twenty authors; the complete list, as printed on the paper, is used here.

How to cite it

Adam G. Riess, Alexei V. Filippenko, Peter Challis, Alejandro Clocchiatti, Alan Diercks, Peter M. Garnavich, Ron L. Gilliland, Craig J. Hogan, Saurabh Jha, Robert P. Kirshner, B. Leibundgut, M. M. Phillips, David Reiss, Brian P. Schmidt, Robert A. Schommer, R. Chris Smith, J. Spyromilio, Christopher Stubbs, Nicholas B. Suntzeff, John Tonry (1998) Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant doi:10.1086/300499

Where it sits in the curriculum

The vacuum at cosmic scale