Hubble's law
Observed values of the Hubble constant
There are multiple methods to determine the Hubble constant, their results differ significantly. As of 2019, the cause of the discrepancy is not understood.

Hubble's law

Section Title: Observed values of the Hubble constant
Table Section Text: There are multiple methods to determine the Hubble constant, their results differ significantly. As of 2019, the cause of the discrepancy is not understood.

Date published	Hubble constant (km/s)/Mpc	Observer	Citation	Remarks / methodology

after 1996

before 1996	50–90 (est.)

2019-03-28	68.0+4.2 −4.1	Fermi-LAT	Gamma ray attenuation due to extragalactic light. Independent of the cosmic distance ladder and the cosmic microwave background.

2019-03-18	74.03±1.42	Hubble Space Telescope	Precision HST photometry of Cepheids in the Large Magellanic Cloud (LMC) reduce the uncertainty in the distance to the LMC from 2.5% to 1.3%.

2019-02-08	67.78+0.91 −0.87	Joseph Ryan et al.	Quasar angular size and baryon acoustic oscillations, assuming a flat LambdaCDM model. Alternative models result in different (generally lower) values for the Hubble constant.

2018-11-06	67.77±1.30	DES Collaboration	Supernova measurements using the inverse distance ladder method based on baryon acoustic oscillations.

2018-09-05	72.5+2.1 −2.3	H0LiCOW collaboration	Observations of multiply imaged quasars, independent of the cosmic distance ladder and independent of the cosmic microwave background measurements.

2018-07-18	67.66±0.42	Planck Mission	Final Planck 2018 results.

2018-04-27	73.52±1.62	Hubble Space Telescope and Gaia	Additional HST photometry of galactic Cepheids with early Gaia parallax measurements. The revised value increases tension with CMB measurements at the 3.8σ level.

2018-02-22	73.45±1.66	Hubble Space Telescope	Parallax measurements of galactic Cepheids for enhanced calibration of the distance ladder; the value suggests a discrepancy with CMB measurements at the 3.7σ level.

2017-10-16	70.0+12.0 −8.0	The LIGO Scientific Collaboration and The Virgo Collaboration	Measurement was independent of a cosmic ‘distance ladder'; the gravitational-wave analysis of a binary neutron star (BNS) merger GW170817 directly estimated the luminosity distance out to cosmological scales.

2016-11-22	71.9+2.4 −3.0	Hubble Space Telescope	Uses time delays between multiple images of distant variable sources produced by strong gravitational lensing. Collaboration known as Lenses in COSMOGRAIL's Wellspring (H0LiCOW).

2016-08-04	76.2+3.4 −2.7	Cosmicflows-3	Comparing redshift to other distance methods, including Tully–Fisher, Cepheid variable, and Type Ia supernovae. A restrictive estimate from the data implies a more precise value of 75±2.

2016-07-13	67.6+0.7 −0.6	SDSS-III Baryon Oscillation Spectroscopic Survey	Baryon acoustic oscillations. An extended survey (eBOSS) began in 2014 and is expected to run through 2020.

2016-05-17	73.24±1.74	Hubble Space Telescope	Type Ia supernova, the uncertainty is expected to go down by a factor of more than two with upcoming Gaia measurements and other improvements.

2015-02	67.74±0.46	Planck Mission	Results from an analysis of Planck's full mission were made public on 1 December 2014 at a conference in Ferrara, Italy.

2013-10-01	74.4±3.0	Cosmicflows-2	Comparing redshift to other distance methods, including Tully–Fisher, Cepheid variable, and Type Ia supernovae.

2013-03-21	67.80±0.77	Planck Mission	The ESA Planck Surveyor was launched in May 2009. Over a four-year period, it performed a significantly more detailed investigation of cosmic microwave radiation than earlier investigations using HEMT radiometers and bolometer technology to measure the CMB at a smaller scale than WMAP.

2012-12-20	69.32±0.80	WMAP (9 years), combined with other measurements.

2010	70.4+1.3 −1.4	WMAP (7 years), combined with other measurements.	These values arise from fitting a combination of WMAP and other cosmological data to the simplest version of the ΛCDM model.

2010	71.0±2.5	WMAP only (7 years).

2009-02	70.5±1.3	WMAP (5 years), combined with other measurements.

2009-02	71.9+2.6 −2.7	WMAP only (5 years)

2007	70.4+1.5 −1.6	WMAP (3 years), combined with other measurements.

2006-08	76.9+10.7 −8.7	Chandra X-ray Observatory	Combined Sunyaev–Zel'dovich effect and Chandra X-ray observations of galaxy clusters. Adjusted uncertainty in table from Planck Collaboration 2013.

2001-05	72±8	Hubble Space Telescope Key Project	This project established the most precise optical determination, consistent with a measurement of H0 based upon Sunyaev–Zel'dovich effect observations of many galaxy clusters having a similar accuracy.

after 1996

before 1996	50–90 (est.)

early 1970s	~55 (est.)	Allan Sandage and Gustav Tammann

1958	75 (est.)	Allan Sandage	This was the first good estimate of H0, but it would be decades before a consensus was achieved.

1956	180	Humason, Mayall and Sandage

1929	500	Edwin Hubble, Hooker telescope

1927	625	Georges Lemaître	First measurement and interpretation as a sign of the expansion of the universe

Sentence(s)

The Planck mission published in 2018 indicated a value of 67.66±0.42 and in 2019, a value of 74.03±1.42 has been determined using the Hubble Space Telescope.

final_sentence: The Planck mission published in 2018 indicated a value of 67.66±0.42 and in 2019, a value of 74.03±1.42 has been determined using the Hubble Space Telescope.