March 13, 1998

High-Z Supernova Search Team

The Astronomical Journal receives the High-Z team's acceleration manuscript

The date commemorated as a publication is actually a line in the journal record: 'Received 1998 March 13.' The team had gone looking for cosmic slowing — and submitted evidence for the opposite.

13 March 1998: a manuscript arrives

On 13 March 1998, The Astronomical Journal received a manuscript from the High-Z Supernova Search Team, with Adam Riess as lead author: 'Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant.'

Nothing was published publicly that day — the paper was revised on 6 May, posted to arXiv on 15 May, and appeared in the September 1998 issue. The famous date is the journal's received stamp, not a publication.

Fifty stellar explosions, one reversal

The analysis compared 16 high-redshift Type Ia supernovae — including 10 newly presented at redshifts 0.16 to 0.62 — against 34 nearby ones. The distant supernovae averaged only 10 to 15 percent farther away than a low-density, no-cosmological-constant universe predicted.

That small discrepancy carried the argument: the team's two fitting methods supported present-day acceleration at 2.8 and 3.9 standard deviations, favoring a positive cosmological constant. A team that set out to measure how much the universe's expansion was slowing had found it speeding up.

Priority, carefully stated

The rival Supernova Cosmology Project had publicly presented acceleration evidence in January 1998, while NASA describes the High-Z September paper as the first published evidence — the two independent teams discovered the effect separately, and historical accounts distinguish announcement, preprint and refereed-publication priority.

The recognition was ultimately shared: Science named the accelerating universe its 1998 Breakthrough of the Year, and Saul Perlmutter, Brian Schmidt and Adam Riess shared the 2011 Nobel Prize in Physics. What the 1998 data did not do, by themselves, was identify the physical nature of the dark energy behind the acceleration.

Sources

Researched 23 Aug 2026 6 sources 3 audit passes

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

What the sources leave uncertain

The date itself is secure, but its meaning has been misreported: 13 March is the journal's manuscript-received date, not the publication date.
Priority language requires care. The Supernova Cosmology Project publicly presented acceleration evidence in January 1998; NASA describes the High-Z September paper as the first published evidence. The two teams independently discovered the effect and jointly received later recognition.