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2.
Nature ; 622(7982): 255-260, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37648866

RESUMO

Neptune-sized planets exhibit a wide range of compositions and densities, depending on factors related to their formation and evolution history, such as the distance from their host stars and atmospheric escape processes. They can vary from relatively low-density planets with thick hydrogen-helium atmospheres1,2 to higher-density planets with a substantial amount of water or a rocky interior with a thinner atmosphere, such as HD 95338 b (ref. 3), TOI-849 b (ref. 4) and TOI-2196 b (ref. 5). The discovery of exoplanets in the hot-Neptune desert6, a region close to the host stars with a deficit of Neptune-sized planets, provides insights into the formation and evolution of planetary systems, including the existence of this region itself. Here we show observations of the transiting planet TOI-1853 b, which has a radius of 3.46 ± 0.08 Earth radii and orbits a dwarf star every 1.24 days. This planet has a mass of 73.2 ± 2.7 Earth masses, almost twice that of any other Neptune-sized planet known so far, and a density of 9.7 ± 0.8 grams per cubic centimetre. These values place TOI-1853 b in the middle of the Neptunian desert and imply that heavy elements dominate its mass. The properties of TOI-1853 b present a puzzle for conventional theories of planetary formation and evolution, and could be the result of several proto-planet collisions or the final state of an initially high-eccentricity planet that migrated closer to its parent star.

3.
Innovation (Camb) ; 3(4): 100271, 2022 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-35818562
4.
Science ; 374(6572): 1271-1275, 2021 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-34855492

RESUMO

Ultrashort-period (USP) exoplanets have orbital periods shorter than 1 day. Precise masses and radii of USP exoplanets could provide constraints on their unknown formation and evolution processes. We report the detection and characterization of the USP planet GJ 367b using high-precision photometry and radial velocity observations. GJ 367b orbits a bright (V-band magnitude of 10.2), nearby, and red (M-type) dwarf star every 7.7 hours. GJ 367b has a radius of 0.718 ± 0.054 Earth-radii and a mass of 0.546 ± 0.078 Earth-masses, making it a sub-Earth planet. The corresponding bulk density is 8.106 ± 2.165 grams per cubic centimeter­close to that of iron. An interior structure model predicts that the planet has an iron core radius fraction of 86 ± 5%, similar to that of Mercury's interior.

5.
Mol Metab ; 49: 101201, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33647468

RESUMO

OBJECTIVES: The only proteins known to be modified by O-linked lipidation are Wnts and ghrelin, and enzymatic removal of this post-translational modification inhibits ligand activity. Indeed, the Wnt-deacylase activity of Notum is the basis of its ability to act as a feedback inhibitor of Wnt signalling. Whether Notum also deacylates ghrelin has not been determined. METHODS: We used mass spectrometry to assay ghrelin deacylation by Notum and co-crystallisation to reveal enzyme-substrate interactions at the atomic level. CRISPR/Cas technology was used to tag endogenous Notum and assess its localisation in mice while liver-specific Notum knock-out mice allowed us to investigate the physiological role of Notum in modulating the level of ghrelin deacylation. RESULTS: Mass spectrometry detected the removal of octanoyl from ghrelin by purified active Notum but not by an inactive mutant. The 2.2 Å resolution crystal structure of the Notum-ghrelin complex showed that the octanoyl lipid was accommodated in the hydrophobic pocket of the Notum. The knock-in allele expressing HA-tagged Notum revealed that Notum was produced in the liver and present in the bloodstream, albeit at a low level. Liver-specific inactivation of Notum in animals fed a high-fat diet led to a small but significant increase in acylated ghrelin in the circulation, while no such increase was seen in wild-type animals on the same diet. CONCLUSIONS: Overall, our data demonstrate that Notum can act as a ghrelin deacylase, and that this may be physiologically relevant under high-fat diet conditions. Our study therefore adds Notum to the list of enzymes, including butyrylcholinesterase and other carboxylesterases, that modulate the acylation state of ghrelin. The contribution of multiple enzymes could help tune the activity of this important hormone to a wide range of physiological conditions.


Assuntos
Esterases/metabolismo , Grelina/genética , Grelina/metabolismo , Acilação , Animais , Butirilcolinesterase/metabolismo , Esterases/química , Esterases/genética , Humanos , Ligantes , Masculino , Camundongos , Camundongos Knockout
6.
J Am Coll Health ; 67(5): 397-401, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29979954

RESUMO

University officials are increasingly considering selling alcoholic beverages at campus football stadiums. To inform this decision, we report on offenses occurring at a campus football stadium and surrounding community on game day weekends between 2009 and 2013. Campus police log data for 35 home football weekends were examined, accounting for 1,940 distinct incidents. There was a general upward trend in crime incidents. On average, 330 total crime incidents occurred when alcohol was not sold (2009-2011) compared to 475 annually when alcohol was sold (2012-2013). Liquor law violations and alcohol consumption by a minor were the two most frequently cited offenses. Liquor law violations (317) was highest after alcohol sales initiated. Police incidents were markedly higher when playing a traditional football rival at home. College administrators, health officials, athletic departments, and local law enforcement must work together to weigh the potential benefit of enhanced financial profit against the risk of increased alcohol-related crime.


Assuntos
Consumo de Bebidas Alcoólicas/epidemiologia , Bebidas Alcoólicas/estatística & dados numéricos , Crime/estatística & dados numéricos , Futebol Americano , Universidades/organização & administração , Humanos , Masculino , Estudantes , Consumo de Álcool por Menores/estatística & dados numéricos , Universidades/normas , Violência/estatística & dados numéricos
7.
Astrophys J Suppl Ser ; 235(2)2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32908325

RESUMO

We present the Kepler Object of Interest (KOI) catalog of transiting exoplanets based on searching four years of Kepler time series photometry (Data Release 25, Q1-Q17). The catalog contains 8054 KOIs of which 4034 are planet candidates with periods between 0.25 and 632 days. Of these candidates, 219 are new in this catalog and include two new candidates in multi-planet systems (KOI-82.06 and KOI-2926.05), and ten new high-reliability, terrestrial-size, habitable zone candidates. This catalog was created using a tool called the Robovetter which automatically vets the DR25 Threshold Crossing Events (TCEs) found by the Kepler Pipeline (Twicken et al. 2016). Because of this automation, we were also able to vet simulated data sets and therefore measure how well the Robovetter separates those TCEs caused by noise from those caused by low signal-to-noise transits. Because of these measurements we fully expect that this catalog can be used to accurately calculate the frequency of planets out to Kepler's detection limit, which includes temperate, super-Earth size planets around GK dwarf stars in our Galaxy. This paper discusses the Robovetter and the metrics it uses to decide which TCEs are called planet candidates in the DR25 KOI catalog. We also discuss the simulated transits, simulated systematic noise, and simulated astrophysical false positives created in order to characterize the properties of the final catalog. For orbital periods less than 100 d the Robovetter completeness (the fraction of simulated transits that are determined to be planet candidates) across all observed stars is greater than 85%. For the same period range, the catalog reliability (the fraction of candidates that are not due to instrumental or stellar noise) is greater than 98%. However, for low signal-to-noise candidates found between 200 and 500 days, our measurements indicate that the Robovetter is 73.5% complete and 37.2% reliable across all searched stars (or 76.7% complete and 50.5% reliable when considering just the FGK dwarf stars). We describe how the measured completeness and reliability varies with period, signal-to-noise, number of transits, and stellar type. Also, we discuss a value called the disposition score which provides an easy way to select a more reliable, albeit less complete, sample of candidates. The entire KOI catalog, the transit fits using Markov chain Monte Carlo methods, and all of the simulated data used to characterize this catalog are available at the NASA Exoplanet Archive.

8.
Antimicrob Agents Chemother ; 60(10): 6091-9, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27480853

RESUMO

The increasing global prevalence of drug resistance among many leading human pathogens necessitates both the development of antibiotics with novel mechanisms of action and a better understanding of the physiological activities of preexisting clinically effective drugs. Inhibition of peptidoglycan (PG) biosynthesis and cross-linking has traditionally enjoyed immense success as an antibiotic target in multiple bacterial pathogens, except in Mycobacterium tuberculosis, where it has so far been underexploited. d-Cycloserine, a clinically approved antituberculosis therapeutic, inhibits enzymes within the d-alanine subbranch of the PG-biosynthetic pathway and has been a focus in our laboratory for understanding peptidoglycan biosynthesis inhibition and for drug development in studies of M. tuberculosis During our studies on alternative inhibitors of the d-alanine pathway, we discovered that the canonical alanine racemase (Alr) inhibitor ß-chloro-d-alanine (BCDA) is a very poor inhibitor of recombinant M. tuberculosis Alr, despite having potent antituberculosis activity. Through a combination of enzymology, microbiology, metabolomics, and proteomics, we show here that BCDA does not inhibit the d-alanine pathway in intact cells, consistent with its poor in vitro activity, and that it is instead a mechanism-based inactivator of glutamate racemase (MurI), an upstream enzyme in the same early stage of PG biosynthesis. This is the first report to our knowledge of inhibition of MurI in M. tuberculosis and thus provides a valuable tool for studying this essential and enigmatic enzyme and a starting point for future MurI-targeted antibacterial development.


Assuntos
Isomerases de Aminoácido/química , Antituberculosos/farmacologia , Proteínas de Bactérias/química , Inibidores Enzimáticos/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , beta-Alanina/análogos & derivados , Isomerases de Aminoácido/antagonistas & inibidores , Isomerases de Aminoácido/genética , Isomerases de Aminoácido/metabolismo , Sequência de Aminoácidos , Antituberculosos/química , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Clonagem Molecular , Inibidores Enzimáticos/química , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Cinética , Testes de Sensibilidade Microbiana , Mycobacterium tuberculosis/enzimologia , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/crescimento & desenvolvimento , Peptidoglicano/biossíntese , Ligação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Especificidade por Substrato , beta-Alanina/química , beta-Alanina/farmacologia
9.
Nature ; 519(7542): 187-192, 2015 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-25731175

RESUMO

Signalling by Wnt proteins is finely balanced to ensure normal development and tissue homeostasis while avoiding diseases such as cancer. This is achieved in part by Notum, a highly conserved secreted feedback antagonist. Notum has been thought to act as a phospholipase, shedding glypicans and associated Wnt proteins from the cell surface. However, this view fails to explain specificity, as glypicans bind many extracellular ligands. Here we provide genetic evidence in Drosophila that Notum requires glypicans to suppress Wnt signalling, but does not cleave their glycophosphatidylinositol anchor. Structural analyses reveal glycosaminoglycan binding sites on Notum, which probably help Notum to co-localize with Wnt proteins. They also identify, at the active site of human and Drosophila Notum, a large hydrophobic pocket that accommodates palmitoleate. Kinetic and mass spectrometric analyses of human proteins show that Notum is a carboxylesterase that removes an essential palmitoleate moiety from Wnt proteins and thus constitutes the first known extracellular protein deacylase.


Assuntos
Carboxilesterase/metabolismo , Proteínas de Drosophila/metabolismo , Esterases/metabolismo , Proteínas Wnt/química , Proteínas Wnt/metabolismo , Via de Sinalização Wnt , Acilação , Animais , Sítios de Ligação , Carboxilesterase/química , Proteínas de Drosophila/química , Esterases/química , Esterases/genética , Ácidos Graxos Monoinsaturados/metabolismo , Glicosilfosfatidilinositóis/metabolismo , Glipicanas/metabolismo , Humanos , Cinética , Ligantes , Espectrometria de Massas , Modelos Moleculares , Ligação Proteica
10.
J Prim Prev ; 35(6): 409-16, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25236926

RESUMO

While alcohol consumption has been consistently linked to college football games in the United States, this literature lacks (a) field-based event-level analyses; (b) assessments of the context of drinking, such as days leading to an event, that occurs in conjunction with a contest; (c) investigations of non-student drinking; and (d) objective assessments of opponent rating. Therefore, the present study: (1) examines the extent to which breath alcohol concentrations (BrAC) among restaurant and bar district patrons differ for low- and high-profile games and (2) explores the relationship between an objective rating of a team's opponent and BrAC levels. Data were collected throughout the fall 2011 football season via six anonymous field studies in a bar district within a southeastern college community. During low-profile game weekends, respondents recorded significantly lower BrAC levels than those during high-profile game weekends. Additionally, there was a positive correlation between opponent rating and BrAC levels, such that mean BrAC readings were highest prior to the game featuring the highest rated opponent. Overall, participants exhibited significantly higher BrACs when a higher-rated opponent was playing that weekend. When resources (money, manpower) are limited, community-based prevention and enforcement efforts should occur during the weekends surrounding higher-profile games.


Assuntos
Alcoolismo/epidemiologia , Futebol Americano , Adulto , Testes Respiratórios , Etanol/sangue , Feminino , Humanos , Entrevistas como Assunto , Masculino , Pessoa de Meia-Idade , Estados Unidos/epidemiologia , Universidades , Adulto Jovem
11.
Science ; 344(6181): 277-80, 2014 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-24744370

RESUMO

The quest for Earth-like planets is a major focus of current exoplanet research. Although planets that are Earth-sized and smaller have been detected, these planets reside in orbits that are too close to their host star to allow liquid water on their surfaces. We present the detection of Kepler-186f, a 1.11 ± 0.14 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized, that transit a 0.47 ± 0.05 solar-radius star. The intensity and spectrum of the star's radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form.


Assuntos
Planetas , Astros Celestes , Planeta Terra , Exobiologia , Meio Ambiente Extraterreno , Água
12.
Nature ; 499(7456): 55-8, 2013 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-23803764

RESUMO

Most stars and their planets form in open clusters. Over 95 per cent of such clusters have stellar densities too low (less than a hundred stars per cubic parsec) to withstand internal and external dynamical stresses and fall apart within a few hundred million years. Older open clusters have survived by virtue of being richer and denser in stars (1,000 to 10,000 per cubic parsec) when they formed. Such clusters represent a stellar environment very different from the birthplace of the Sun and other planet-hosting field stars. So far more than 800 planets have been found around Sun-like stars in the field. The field planets are usually the size of Neptune or smaller. In contrast, only four planets have been found orbiting stars in open clusters, all with masses similar to or greater than that of Jupiter. Here we report observations of the transits of two Sun-like stars by planets smaller than Neptune in the billion-year-old open cluster NGC6811. This demonstrates that small planets can form and survive in a dense cluster environment, and implies that the frequency and properties of planets in open clusters are consistent with those of planets around field stars in the Galaxy.

13.
Science ; 340(6132): 587-90, 2013 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-23599262

RESUMO

We present the detection of five planets--Kepler-62b, c, d, e, and f--of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R⊕), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets, Kepler-62e and -62f, are super-Earth-size (1.25 R⊕ < planet radius ≤ 2.0 R⊕) planets in the habitable zone of their host star, respectively receiving 1.2 ± 0.2 times and 0.41 ± 0.05 times the solar flux at Earth's orbit. Theoretical models of Kepler-62e and -62f for a stellar age of ~7 billion years suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk.


Assuntos
Planetas , Água , Exobiologia , Meio Ambiente Extraterreno , Modelos Teóricos , Astros Celestes
14.
Nature ; 494(7438): 452-4, 2013 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-23426260

RESUMO

Since the discovery of the first exoplanets, it has been known that other planetary systems can look quite unlike our own. Until fairly recently, we have been able to probe only the upper range of the planet size distribution, and, since last year, to detect planets that are the size of Earth or somewhat smaller. Hitherto, no planets have been found that are smaller than those we see in the Solar System. Here we report a planet significantly smaller than Mercury. This tiny planet is the innermost of three that orbit the Sun-like host star, which we have designated Kepler-37. Owing to its extremely small size, similar to that of the Moon, and highly irradiated surface, the planet, Kepler-37b, is probably rocky with no atmosphere or water, similar to Mercury.

15.
Nature ; 481(7382): 475-9, 2012 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-22237021

RESUMO

Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ∼1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.


Assuntos
Planetas , Meio Ambiente Extraterreno/química , Voo Espacial , Astronave , Astros Celestes
16.
Nature ; 482(7384): 195-8, 2011 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-22186831

RESUMO

Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth's radius (R(⊕)), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R(⊕)) and the other smaller than the Earth (0.87R(⊕)), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere.

17.
Science ; 333(6049): 1602-6, 2011 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-21921192

RESUMO

We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.

18.
Epilepsia ; 52(11): 2028-35, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21762441

RESUMO

PURPOSE: Psychogenic nonepileptic seizures (PNES) continue to represent a serious diagnostic challenge for neurologists. Video-electroencephalography (EEG) studies have provided detailed knowledge of the spectrum of visible PNES manifestations. However, little is known about how patients or seizure witnesses experience PNES, although many diagnoses in seizure clinics are made on the basis of self-reported information rather than video-EEG observations. This study describes the range of PNES manifestations as they are reported by patients or seizure witnesses. METHODS: Three hundred eight candidates for this study were consecutively diagnosed with PNES on the basis of video-EEG recordings of habitual seizures involving impairment of consciousness without epileptic ictal EEG activity at the Royal Hallamshire Hospital in Sheffield and the National Hospital for Neurology in London, United Kingdom. One hundred patients responded to a postal questionnaire and participated in this study. Eighty-four of the questionnaires completed by patients were accompanied by questionnaires completed by seizure witness. The patient questionnaire contained 12 demographic and clinical questions and the 86-item Paroxysmal Event Profile (PEP), asking patients to rate statements about their attacks on a five-point Likert scale ("always,""frequently,""sometimes,""rarely,""never"). The Paroxysmal Event Observer (PEO) questionnaire uses 34-items with the same Likert scale. The PEP questionnaire includes inquiries about symptoms of panic or dissociation as well as symptoms previously found to distinguish between generalized tonic-clonic seizures and syncope or thought to differentiate between epilepsy and PNES. KEY FINDINGS: The item-by-item analysis revealed the inter- and intraindividual variability of PNES experiences. The majority of patients with PNES reported some phenomena, which have traditionally been attributed to epilepsy (such as seizures from sleep, experiencing a rising sensation in their body, postictal myalgia). Although most PNES were experienced as striking without warning and reported to cause loss or impairment of consciousness, most patients also reported seizure warnings in at least some of the seizures. Despite the clinical heterogeneity apparent from these findings, a correlation matrix showed that symptoms were not randomly distributed. Significant correlations were seen between duration of seizures and seizures from reported sleep (r = -0.28, p = 0.006), seizure-related motor activity and seizures from reported sleep (p = -0.48, p < 0.001), flashbacks and anxiety (p = 0.44, p < 0.001) or dissociation (p = 0.66, p < 0.001), and anxiety and dissociation (r = 0.53, p < 0.001). The comparison of similarly worded items on the PEP and PEO questionnaires showed that witnesses were more often aware of seizure triggers and a relationship between PNES and emotional stress than were patients (p = 0.001/p < 0.001). SIGNIFICANCE: These findings based on the self-report of patients with well-characterized PNES and witnesses of their seizures demonstrate why it can be difficult to distinguish descriptions of PNES from those of epilepsy on the basis of factual items. The differences between patient and witness reports suggest that clinicians have to take note of the source of information they use in their diagnostic considerations. The intra- and interindividual variability of reported PNES manifestations demonstrates the clinical heterogeneity of PNES disorders. The positive correlation of symptoms of dissociation and anxiety in these patients may reflect psychopathologic differences between subgroups of PNES patients.


Assuntos
Transtorno Conversivo/fisiopatologia , Convulsões/fisiopatologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Encéfalo/fisiopatologia , Transtorno Conversivo/diagnóstico , Eletroencefalografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Convulsões/diagnóstico , Inquéritos e Questionários , Adulto Jovem
19.
Science ; 330(6000): 51-4, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20798283

RESUMO

The Kepler spacecraft is monitoring more than 150,000 stars for evidence of planets transiting those stars. We report the detection of two Saturn-size planets that transit the same Sun-like star, based on 7 months of Kepler observations. Their 19.2- and 38.9-day periods are presently increasing and decreasing at respective average rates of 4 and 39 minutes per orbit; in addition, the transit times of the inner body display an alternating variation of smaller amplitude. These signatures are characteristic of gravitational interaction of two planets near a 2:1 orbital resonance. Six radial-velocity observations show that these two planets are the most massive objects orbiting close to the star and substantially improve the estimates of their masses. After removing the signal of the two confirmed giant planets, we identified an additional transiting super-Earth-size planet candidate with a period of 1.6 days.

20.
Science ; 327(5968): 977-80, 2010 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-20056856

RESUMO

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (approximately 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.

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