Explore the vast range of titles available.

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. GJ1132b — a nearby rocky, Earth-sized planet Zachory Berta-Thompson et al . report observations of GJ 1132b, a 1.2 Earth radius planet transiting a small star only 12 parsecs away. The Doppler mass measurement of GJ 1132b yields a density consistent with an Earth-like rock/iron composition. The planet is too hot to be habitable but is cool enough to support a substantial atmosphere. Because the host star is nearby, existing and upcoming telescopes will be able to observe the composition and dynamics of the planetary atmosphere. M-dwarf stars—hydrogen-burning stars that are smaller than 60 per cent of the size of the Sun—are the most common class of star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1. Recent results have shown that M dwarfs host Earth-sized planets in great numbers 1 , 2 : the average number of M-dwarf planets that are between 0.5 to 1.5 times the size of Earth is at least 1.4 per star 3 . The nearest such planets known to transit their star are 39 parsecs away 4 , too distant for detailed follow-up observations to measure the planetary masses or to study their atmospheres. Here we report observations of GJ 1132b, a planet with a size of 1.2 Earth radii that is transiting a small star 12 parsecs away. Our Doppler mass measurement of GJ 1132b yields a density consistent with an Earth-like bulk composition, similar to the compositions of the six known exoplanets with masses less than six times that of the Earth and precisely measured densities 5 , 6 , 7 , 8 , 9 , 10 , 11 . Receiving 19 times more stellar radiation than the Earth, the planet is too hot to be habitable but is cool enough to support a substantial atmosphere, one that has probably been considerably depleted of hydrogen. Because the host star is nearby and only 21 per cent the radius of the Sun, existing and upcoming telescopes will be able to observe the composition and dynamics of the planetary atmosphere.

A super-Earth with atmosphere 'Super-Earths' are extrasolar planets about two to ten times the mass of the Earth, too small to be considered 'Jupiters'. Observations from the MEarth Project — using two 40-cm (16-inch) telescopes that will eventually be part of an eight-telescope array — have now identified a super-Earth (GJ 1214b) transiting a nearby low mass star. GJ 1214b has a mass 6.55 times that of the Earth and a radius of 2.68 'Earths'. As the star is small and only 13 parsecs away, the planetary atmosphere is available for direct study with current observatories. 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. A decade ago, the detection of the first 1 , 2 transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres 3 . Because such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies 4 , 5 , 6 and microlensing 7 have uncovered a population of planets with minimum masses of 1.9–10 times the Earth’s mass ( M ⊕ ), called super-Earths. The first constraint on the bulk composition of this novel class of planets was afforded by CoRoT-7b (refs 8 , 9 ), but the distance and size of its star preclude atmospheric studies in the foreseeable future. Here we report observations of the transiting planet GJ 1214b, which has a mass of 6.55 M ⊕ and a radius 2.68 times Earth’s radius ( R ⊕ ), indicating that it is intermediate in stature between Earth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen–helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history. The star is small and only 13 parsecs away, so the planetary atmosphere is amenable to study with current observatories.

Measures of exoplanet bulk densities indicate that small exoplanets with radius less than 3 Earth radii (R⊕) range from low-density sub-Neptunes containing volatile elements1 to higher-density rocky planets with Earth-like2 or iron-rich3 (Mercury-like) compositions. Such astonishing diversity in observed small exoplanet compositions may be the product of different initial conditions of the planet-formation process or different evolutionary paths that altered the planetary properties after formation4. Planet evolution may be especially affected by either photoevaporative mass loss induced by high stellar X-ray and extreme ultraviolet (XUV) flux5 or giant impacts6. Although there is some evidence for the former7,8, there are no unambiguous findings so far about the occurrence of giant impacts in an exoplanet system. Here, we characterize the two innermost planets of the compact and near-resonant system Kepler-107 (ref. 9). We show that they have nearly identical radii (about 1.5–1.6R⊕), but the outer planet Kepler-107 c is more than twice as dense (about 12.6 g cm–3) as the innermost Kepler-107 b (about 5.3 g cm−3). In consequence, Kepler-107 c must have a larger iron core fraction than Kepler-107 b. This imbalance cannot be explained by the stellar XUV irradiation, which would conversely make the more-irradiated and less-massive planet Kepler-107 b denser than Kepler-107 c. Instead, the dissimilar densities are consistent with a giant impact event on Kepler-107 c that would have stripped off part of its silicate mantle. This hypothesis is supported by theoretical predictions from collisional mantle stripping10, which match the mass and radius of Kepler-107 c.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.

HD 219134 is a K-dwarf star at a distance of 6.5 parsecs around which several low-mass planets were recently discovered 1 , 2 . The Spitzer Space Telescope detected a transit of the innermost of these planets, HD 219134 b, whose mass and radius (4.5  M ⊕ and 1.6  R ⊕ respectively) are consistent with a rocky composition 1 . Here, we report new high-precision time-series photometry of the star acquired with Spitzer revealing that the second innermost planet of the system, HD 219134c, is also transiting. A global analysis of the Spitzer transit light curves and the most up-to-date HARPS-N velocity data set yields mass and radius estimations of 4.74 ± 0.19  M ⊕ and 1.602 ± 0.055  R ⊕ for HD 219134 b, and of 4.36 ± 0.22  M ⊕ and 1.511 ± 0.047  R ⊕ for HD 219134 c. These values suggest rocky compositions for both planets. Thanks to the proximity and the small size of their host star (0.778 ± 0.005 R ⊙ ) 3 , these two transiting exoplanets — the nearest to the Earth yet found — are well suited for a detailed characterization (for example, precision of a few per cent on mass and radius, and constraints on the atmospheric properties) that could give important constraints on the nature and formation mechanism of the ubiquitous short-period planets of a few Earth masses. The authors find that a nearby planetary system has two terrestrial planets that transit in front of their star (from our perspective). Transiting terrestrial planets are sought after, as they can be characterized in detail, including their atmospheres. Having two in the same system is very rare.

To evaluate the imaging methods used at the emergency department (ED) of a cancer center, with emphasis on computed tomography (CT). A descriptive, retrospective, single-center study was conducted by reviewing imaging exams and medical records, after approval of the institution’s Ethics Review Board. The demographic data, cancer history, and imaging exam requested were evaluated for all patients and the indications and results of head, chest, and abdominopelvic CT scans were also evaluated. During the study period, there were 8710 visits to the ED, and 5999 imaging studies were requested in 3788 patients (43.5 % of total of visits). One thousand eight hundred twenty-nine CT exams were used in 1121 visits (12.9 % of total of visits). The mean age of patients was 57.7 years and most patients (93.2 %) had a known primary tumor. The most common indications for abdominopelvic CT were non-oncologic emergencies (26.7 %) and postoperative complications (19.2 %), and the results were negative in 36.6 %, positive for clinical suspicion in 49.0 %, and incidental positive in 14.5 %. The most frequent indication for chest CT was suspected pulmonary embolism (34.4 %); however, only 11.1 % confirmed the diagnosis. The results of head TC were negative in 72.9 % and the indications that had more positive findings were suspected metastasis (32.1 %) and focal neurological sign/altered level of consciousness (24.5 %). CT plays an important role in driving the cancer patients visiting the ED. However, the high rate of negative or discordant results causes a concern for the inadvertent and excessive use of this imaging modality.

Doppler spectroscopy was the first technique used to reveal the existence of extrasolar planetary systems hosted by solar-type stars. Radial-velocity surveys led to the detection of a rich population of super-Earths and Neptune-type planets. The numerous detected systems revealed a remarkable diversity. Combining Doppler measurements with photometric observations of planets transiting their host stars further provides access to the planet bulk density, a first step towards comparative exoplanetology. The development of new high-precision spectrographs and space-based facilities will ultimately lead us to characterize rocky planets in the habitable zone of our close stellar neighbours.

Exoplanets down to the size of Earth have been found, but not in the habitable zone—that is, at a distance from the parent star at which water, if present, would be liquid. There are planets in the habitable zone of stars cooler than our Sun, but for reasons such as tidal locking and strong stellar activity, they are unlikely to harbour water–carbon life as we know it. The detection of a habitable Earth-mass planet orbiting a star similar to our Sun is extremely difficult, because such a signal is overwhelmed by stellar perturbations. Here we report the detection of an Earth-mass planet orbiting our neighbour star α Centauri B, a member of the closest stellar system to the Sun. The planet has an orbital period of 3.236 days and is about 0.04 astronomical units from the star (one astronomical unit is the Earth–Sun distance). The detection of an Earth-mass planet orbiting our neighbour star α Centauri B is reported; the planet has an orbital period of 3.236 days and is about 0.04 astronomical units from the star. A nearby Earth-mass exoplanet discovered An exoplanet with an Earth-like mass has been discovered orbiting the nearby star α Centauri B. The planet is not in the habitable zone — it is much nearer to its star than we are to the Sun, orbiting at only about 0.04 astronomical units from its star (an astronomical unit is the mean distance between Earth and the Sun). Statistical studies suggest that low-mass planets form preferentially in multi-planet systems, so it is possible that other planets are orbiting α Centauri B, perhaps in its habitable zone.

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. Like Earth — but a lot hotter A few exoplanets of about the size or mass of Earth have been discovered. Now, for the first time, both size and mass have been determined for one of them. Kepler-78b, first described in August this year, is close-in to its host star, which it orbits every 8.5 hours. Two groups have been able to exploit the closeness of planet and star to make Doppler spectroscopic measurements of the mass of Kepler-78b. The teams, led by Andrew Howard and Francesco Pepe, used different telescopes to arrive at mass estimates of 1.69 ± 0.41 and 1.86 +0.38/−0.245 Earth masses, respectively. They calculate the planet's mean density at 5.3 and 5.57 g cm −3 , very similar to Earth's and consistent with an Earth-like composition of rock and iron. Recent analyses 1 , 2 , 3 , 4 of data from the NASA Kepler spacecraft 5 have established that planets with radii within 25 per cent of the Earth’s ( ) are commonplace throughout the Galaxy, orbiting at least 16.5 per cent of Sun-like stars 1 . Because these studies were sensitive to the sizes of the planets but not their masses, the question remains whether these Earth-sized planets are indeed similar to the Earth in bulk composition. The smallest planets for which masses have been accurately determined 6 , 7 are Kepler-10b (1.42 ) and Kepler-36b (1.49 ), which are both significantly larger than the Earth. Recently, the planet Kepler-78b was discovered 8 and found to have a radius of only 1.16 . Here we report that the mass of this planet is 1.86 Earth masses. The resulting mean density of the planet is 5.57 g cm −3 , which is similar to that of the Earth and implies a composition of iron and rock.

The presence of a Jupiter-mass companion to the star 51 Pegasi is inferred from observations of periodic variations in the star’s radial velocity. The companion lies only about eight million kilometres from the star, which would be well inside the orbit of Mercury in our Solar System. This object might be a gas-giant planet that has migrated to this location through orbital evolution, or from the radiative stripping of a brown dwarf.

In search of solar lithium Stars similar to the Sun in age, mass and composition show a wide range of lithium abundances, which is hard to explain. The surface lithium abundance of the Sun itself is 140 times less than the primordial Solar System value, yet the Sun's surface convective zone is thought not to extend far enough into the interior to reach regions where lithium can get hot enough to be burned. A new survey of Sun-like stars with and without detected planets now suggests that the planets may hold the key to the Sun's missing lithium. The stars with planets have less than 1% of the primordial lithium abundance, whereas those with no detected planets range more widely, with half of them having about 10% of primordial abundance. It is possible that the presence of protoplanets increases mixing in the stellar disk so that lithium reaches interior regions where the temperatures are sufficient to destroy it. Although a large range of lithium (Li) abundances is observed in solar-type stars, this range has proved theoretically difficult to understand. An earlier suggestion that Li is more depleted in stars with planets was weakened by the lack of a proper comparison sample of stars without detected planets. Here, Li abundances are reported for an unbiased sample of solar-analogue stars with and without detected planets. It is found that about 50% of the solar analogues without detected planets have on average ten times more Li that those with planets. The surface abundance of lithium on the Sun is 140 times less than the protosolar value 1 , yet the temperature at the base of the surface convective zone is not hot enough to burn—and hence deplete—Li (refs 2 , 3 ). A large range of Li abundances is observed 4 , 5 in solar-type stars of the same age, mass and metallicity as the Sun, but such a range is theoretically difficult to understand 3 , 6 , 7 . An earlier suggestion 8 , 9 , 10 that Li is more depleted in stars with planets was weakened by the lack of a proper comparison sample of stars without detected planets. Here we report Li abundances for an unbiased sample of solar-analogue stars with and without detected planets. We find that the planet-bearing stars have less than one per cent of the primordial Li abundance, while about 50 per cent of the solar analogues without detected planets have on average ten times more Li. The presence of planets may increase the amount of mixing and deepen the convective zone to such an extent that the Li can be burned.