Scientific interest in the event was enormous, with dozens of preliminary papers (and almost 100
preprints) published the day of the announcement, including 8 letters in
Science, 6 in
Nature, and 32 in a special issue of
The Astrophysical Journal Letters devoted to the subject. The interest and effort was global: The paper describing the multi-messenger observations is authored by almost 4,000 astronomers (about one-third of the worldwide astronomical community) from more than 900 institutions, using more than 70 observatories on all 7 continents and in space. The event provided a limit on the difference between the
speed of light in vacuum and that of gravity. Assuming the first photons were emitted between zero and ten seconds after peak gravitational wave emission, the difference between the speeds of gravitational and electromagnetic waves, v_{\text{GW}} - v_{\text{EM}}, is constrained to be between −3×10−15 and +7×10−16 times the speed of light, which improves on the previous estimate by about 14 orders of magnitude. In addition, GW170817 allowed investigation of the
equivalence principle (through
Shapiro delay measurement) and
Lorentz invariance. The limits of possible violations of Lorentz invariance (values of "gravity sector coefficients") are reduced by the new observations by up to ten orders of magnitude. The event also excluded some
alternatives to general relativity,
Hořava–Lifshitz gravity, and
bimetric gravity, Furthermore, an analysis published in July 2018 used GW170817 to show that gravitational waves propagate fully through the (3+1)–dimensional curved spacetime described by general relativity, ruling out hypotheses involving "leakage" into higher, non-compact spatial dimensions. Gravitational wave signals such as GW170817 may be used as a
standard siren to provide an independent measurement of the
Hubble constant. An initial estimate of the constant derived from the observation is (km/s)/Mpc, broadly consistent with current
best estimates. Further studies improved the measurement to (km/s)/Mpc. Together with the observation of future events of this kind, the uncertainty is expected to reach two percent within five years and one percent within ten years.Analyses of GW170817 provide more information on the dynamics of the mergers of neutron stars. Electromagnetic observations indicate that these events are responsible for
nucleosynthesis via the rapid neutron capture or
r-process—previously assumed to be associated with supernova explosions—and are therefore the primary source of
r-process elements heavier than iron, including gold and platinum. The first identification of
r-process elements in a neutron star merger was obtained during a re-analysis of GW170817 spectra. The spectra provided direct proof of
strontium production during such an event. Since then, several
r-process elements have been identified in the ejecta including
yttrium,
lanthanum and
cerium. However, GW170817 alone is insufficient for ascertaining the yields of the production of heavy elements. GW170817 alone has enabled an empirical determination of the maximum mass for a neutron star, the
Tolman–Oppenheimer–Volkoff limit, to be around 2.01 to 2.16 M_{\odot} (solar masses), though there are known neutron stars that are heavier, such as
PSR J0952−0607 (2.35 M_{\odot}). and the possible range of radii for neutron stars. In September 2018, astronomers reported related studies about possible mergers of
neutron stars (NS) and
white dwarfs (WD): including NS–NS, NS–WD, and WD–WD mergers. In October 2017,
Stephen Hawking, in what turned out to be his last broadcast interview, discussed the overall scientific importance of GW170817. He mentioned an independent determination of cosmological distances, the formation of heavy elements, the birth of black holes, testing general relativity in the strong–field regime, and the behavior of matter at extreme densities. ==Retrospective comparisons==