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We present this Collection of research, review and comment from Nature Research to celebrate the award of the 2019 Nobel Prize in Physics to James Peebles “for theoretical discoveries in physical cosmology” and to Michel Mayor and Didier Queloz “for the discovery of an exoplanet orbiting a solar-type star”. Together, these discoveries have changed the way we view the Universe, and our place within it.
From the first hints of unseen matter in the Universe to the present body of evidence for dark matter, James Peebles outlines the significant developments in observation and theory in the 1970s in this Insight Perspective.
The relativistic Big Bang theory is a good description of our expanding Universe. But — as discussed in this review article — a still better theory would describe a mechanism by which matter is more rapidly gathered into galaxies and groups of galaxies, better fitting the observations.
A population of extrasolar planets has been uncovered with minimum masses of 1.9–10 times the Earth's mass, called super-Earths, but atmospheric studies can be precluded by the distance and size of their stars. Here, observations of the transiting planet GJ 1214b are reported; it has a mass 6.55 times that of the Earth and a radius 2.68 times the Earth's radius. The star is small and only 13 parsecs away, permitting the study of the planetary atmosphere with current observatories.
In 1995, astronomers detected a blisteringly hot Jupiter-mass planet orbiting closer to its host star than Mercury is to the Sun. This discovery recast our thinking of how planets form and led to a new era of exoplanetary exploration.
Three Earth-sized planets—receiving similar irradiation to Venus and Earth, and ideally suited for atmospheric study—have been found transiting a nearby ultracool dwarf star that has a mass of only eight per cent of that of the Sun.
Last year, three Earth-sized planets were discovered to be orbiting the nearby Jupiter-sized star TRAPPIST-1; now, follow-up photometric observations from the ground and from space show that there are at least seven Earth-sized planets in this star system, and that they might be the right temperature to harbour liquid water on their surfaces.
We are at an interesting juncture in cosmology. Despite vast improvements in the measurement accuracy of the Hubble constant, a recent tension has arisen that is either signalling new physics or as-yet unrecognized uncertainties.
A Kavli Institute for Theoretical Physics workshop in July 2019 directed attention to the Hubble constant discrepancy. New results showed that it does not appear to depend on the use of any one method, team or source. Proposed solutions focused on the pre-recombination era.
The astronomical event GW170817, detected in gravitational and electromagnetic waves, is used to determine the expansion rate of the Universe, which is consistent with and independent of existing measurements.
The LIGO Scientific Collaboration and The Virgo Collaboration
Type Ia supernovae are thought to result from the explosion of white dwarf stars but a full understanding of their formation is lacking. In this review, Howell describes how large surveys are generating sufficient data to challenge and refine existing theories.
Mapping the optical emission of a galaxy cluster to its mass is challenging. Lensing of the cosmic microwave background by massive clusters is used to calibrate the optical richness of clusters to their total baryonic mass at the ten per cent level.
Recent observations reveal tension between various cosmological probes. Assuming dark energy to be non-constant, depending on redshift, may relieve this tension. The Dark Energy Spectroscopic Instrument survey will be able to confirm this result.
A time-dependent dark energy component of the Universe may be able to explain tensions between local and primordial measurements of cosmological parameters, shaking current confidence in the concept of a cosmological ‘constant’.
In the early Universe, fluctuations in the neutrino density produced a distinct shift in the temporal phase of sound waves in the primordial plasma. The size of this phase shift has now been constrained through baryon acoustic oscillation data.
Gravitational wave sources can be used as cosmological probes through a direct distance luminosity relation. Here, the authors demonstrate that the time delay between lensed gravitational wave signals and their electromagnetic counterparts can reduce the uncertainty in the Hubble constant.
Natural philosophers have speculated on the existence of worlds around other suns for millennia. Now that real data are available, we find a diversity far beyond that expected by scientists, or science-fiction writers.
The dawn of exoplanet discovery has unearthed a rich tapestry of planets different from anything encountered in the Solar System. Geoscientists can and should be in the vanguard of investigating what is out there in the Universe.
Simulations show that the system of three Neptune-mass planets is in a dynamically stable configuration, with theoretical calculations favouring a mainly rocky composition for both inner planets, but a significant gaseous envelope surrounding a rocky/icy core for the outer planet.
Orbital parameters for the seventh Earth-sized transiting planet around star TRAPPIST-1 are reported, along with an investigation into the complex three-body resonances linking every member of this planetary system.
Data from the Kepler spacecraft and the HARPS-N ground-based spectrograph indicate that the extrasolar planet Kepler-78b has a mean density similar to that of Earth and imply that it is composed of rock and iron.
A longitudinal thermal brightness map of the super-Earth exoplanet 55 Cancri e reveals strong day–night temperature contrast, indicating inefficient heat redistribution consistent with 55 Cancri e either being devoid of atmosphere or having an optically thick atmosphere with heat recirculation confined to the planetary dayside.
Of the more than 400 known exoplanets, about 70 transit their central star, most in small orbits (with periods of around 1 day, for instance). Here, observations are reported of the transit of CoRoT-9b, which orbits with a period of 95.274 days, on a low eccentricity, around a solar-like star. Its relatively large periastron distance yields a 'temperate' photospheric temperature estimated to be between 250 and 430 K, and its interior composition is inferred to be consistent with those of Jupiter and Saturn.
A low-mass star that is just 12 parsecs away from Earth is shown to be transited by an Earth-sized planet, GJ 1132b, which probably has a rock/iron composition and might support a substantial atmosphere.
Kepler-107 b and c have the same radius but, contrary to expectations, the outermost Kepler-107 c is much denser. This difference cannot be explained by photoevaporation by stellar high-energy particle flux and it suggests that Kepler-107 c experienced a giant impact event.
As the CHaracterising ExOPlanet Satellite (CHEOPS) is scheduled for launch later this year, European Space Agency (ESA) Project Scientist Kate Isaak and Principal Investigator Willy Benz give an overview of ESA’s first science mission dedicated to the follow-up of known exoplanets orbiting bright stars.
A small planet of at least 1.3 Earth masses is orbiting Proxima Centauri with a period of about 11.2 days, with the potential for liquid water on its surface.
An Earth-sized planet is observed orbiting a nearby star within the liquid-water, habitable zone, the atmospheric composition of which could be determined from future observations.
Analysis of 20 years of observations of Barnard’s star from seven facilities reveals a signal with a period of 233 days that is indicative of a companion planet.