Βαρυτικά κύματα:
Αποκαλύπτουν την σταθερά Hubble
και το πόσο
γρήγορα
διαστέλλεται το σύμπαν
A
gravitational-wave standard siren measurement of the Hubble constant
A gravitational-wave standard siren
measurement of the Hubble constan On 17 August 2017, the Advanced LIGO and
Virgo detectors observed the gravitational-wave event GW170817—a strong signal
from the merger of a binary neutron-star system. Less than two seconds after
the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky
consistent with the LIGO–Virgo-derived location of the gravitational-wave
source. This sky region was subsequently observed by optical astronomy
facilities, resulting in the identification of an optical transient signal
within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817
in both gravitational waves and electromagnetic waves represents the first
‘multi-messenger’ astronomical observation. Such observations enable GW170817
to be used as a ‘standard siren’ (meaning that the absolute distance to the
source can be determined directly from the gravitational-wave measurements) to
measure the Hubble constant. This quantity represents the local expansion rate
of the Universe, sets the overall scale of the Universe and is of fundamental
importance to cosmology. Here we report a measurement of the Hubble constant
that combines the distance to the source inferred purely from the
gravitational-wave signal with the recession velocity inferred from
measurements of the redshift using the electromagnetic data. In contrast to
previous measurements, ours does not require the use of a cosmic ‘distance
ladder’: the gravitational-wave analysis can be used to estimate the luminosity
distance out to cosmological scales directly, without the use of intermediate
astronomical distance measurements. We determine the Hubble constant to be
about 70 kilometres per second per megaparsec. This value is consistent with existing
measurements, while being completely independent of them. Additional standard
siren measurements from future gravitational-wave sources will enable the
Hubble constant to be constrained to high precision.
ΠΗΓΗ: A gravitational-wave standard siren measurement of the Hubble constant, στο Nature 551, 85–88, 2 November 2017.
doi:10.1038/nature24471
Received
26 September 2017
Accepted
05 October 2017
Published
online 16 October 2017.
Και: Τα βαρυτικά κύματα μας αποκαλύπτουν την σταθερά Hubble και το πόσο γρήγορα διαστέλλεται το σύμπαν.
ΛΕΞΕΙΣ-ΚΛΕΙΔΙΑ: ΒΑΡΥΤΙΚΑ ΚΥΜΑΤΑ, ΣΤΑΘΕΡΑ ΧΑΜΠΛ, ΔΙΑΣΤΟΛΗ ΣΥΜΠΑΝΤΟΣ, ΣΥΜΠΑΝ
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