Constraints on the Hubble constant from supernova Refsdal's reappearance.

The gravitationally lensed supernova Refsdal appeared in multiple images produced through gravitational lensing by a massive foreground galaxy cluster. After the supernova appeared in 2014, lens models of the galaxy cluster predicted that an additional image of the supernova would appear in 2015, which was subsequently observed. We use the time delays between the images to perform a blinded measurement of the expansion rate of the Universe, quantified by the Hubble constant (H0). Using eight cluster lens models, we infer [Formula: see text]. Using the two models most consistent with the observations, we find [Formula: see text]. The observations are best reproduced by models that assign dark-matter halos to individual galaxies and the overall cluster.

A magnified compact galaxy at redshift 9.51 with strong nebular emission lines.

Ultraviolet light from early galaxies is thought to have ionized gas in the intergalactic medium. However, there are few observational constraints on this epoch because of the faintness of those galaxies and the redshift of their optical light into the infrared. We report the observation, in JWST imaging, of a distant galaxy that is magnified by gravitational lensing. JWST spectroscopy of the galaxy, at rest-frame optical wavelengths, detects strong nebular emission lines that are attributable to oxygen and hydrogen. The measured redshift is z = 9.51 ± 0.01, corresponding to 510 million years after the Big Bang. The galaxy has a radius of [Formula: see text] parsecs, which is substantially more compact than galaxies with equivalent luminosity at z ~ 6 to 8, leading to a high star formation rate surface density.

Impact of Notch3 Activation on Aortic Aneurysm Development in Marfan Syndrome.

BACKGROUND: The leading cause of mortality in patients with Marfan syndrome (MFS) is thoracic aortic aneurysm and dissection. Notch signaling is essential for vessel morphogenesis and function. However, the role of Notch signaling in aortic pathology and aortic smooth muscle cell (SMC) differentiation in Marfan syndrome (MFS) is not completely understood. METHODS: RNA-sequencing on ascending aortic tissue from a mouse model of MFS, Fbn1mgR/mgR , and wild-type controls was performed. Notch 3 expression and activation in aortic tissue were confirmed with real-time RT-PCR, immunohistochemistry, and Western blot. Fbn1mgR/mgR and wild-type mice were treated with a γ-secretase inhibitor, DAPT, to block Notch activation. Aortic aneurysms and rupture were evaluated with connective tissue staining, ultrasound, and life table analysis. RESULTS: The murine RNA-sequencing data were validated with mouse and human MFS aortic tissue, demonstrating elevated Notch3 activation in MFS. Data further revealed that upregulation and activation of Notch3 were concomitant with increased expression of SMC contractile markers. Inhibiting Notch3 activation with DAPT attenuated aortic enlargement and improved survival of Fbn1mgR/mgR mice. DAPT treatment reduced elastin fiber fragmentation in the aorta and reversed the differentiation of SMCs. CONCLUSIONS: Our data demonstrated that matrix abnormalities in the aorta of MFS are associated with increased Notch3 activation. Enhanced Notch3 activation in MFS contributed to aortic aneurysm formation in MFS. This might be mediated by inducing a contractile phenotypic change of SMC. Our results suggest that inhibiting Notch3 activation may provide a strategy to prevent and treat aortic aneurysms in MFS.

Exploring Localized Muscle Fatigue Responses at Current Upper-Extremity Ergonomics Threshold Limit Values.

OBJECTIVE: The purpose of this study was to evaluate localized muscle fatigue responses at three upper-extremity ergonomics threshold limit value (TLV) duty cycles. BACKGROUND: Recently, a TLV equation was published to help mitigate excessive development of localized muscle fatigue in repetitive upper limb tasks. This equation predicts acceptable levels of maximal voluntary contraction (% MVC) for a given duty cycle (DC). Experimental validation of this TLV curve has not yet been reported, which can help guide utilization by practitioners. METHOD: Eighteen participants performed intermittent isometric elbow flexion efforts, in three separate counter-balanced sessions, at workloads defined by the American Conference of Governmental Industrial Hygenists' (ACGIH) TLV equation: low DC (20% DC, 29.6% MVC), medium DC (40% DC, 19.7% MVC), and high DC (60% DC, 13.9% MVC). Targeted localized muscle fatigue (LMF) of the biceps brachii was tracked across numerous response variables, including decline in strength (MVC), electromyography (EMG) amplitude and mean power frequency (MnPF), and several psychophysical ratings. RESULTS: At task completion, biceps MnPF and MVC (strength) were significantly different between each TLV workload, with the high DC condition eliciting the largest declines in MnPF and MVC. CONCLUSION: Findings demonstrate that working at different DCs along the ACGIH TLV curve may not be equivalent in preventing excessive LMF. Higher DC workloads elicited a greater LMF response across several response variables. APPLICATION: High DC work of the upper extremity should be avoided to mitigate excess LMF development. Current TLVs for repetitive upper-extremity work may overestimate acceptable relative contraction thresholds, particularly at higher duty cycles.

Emergency department encounters, hospital admissions, course of treatment, and follow-up care for behavioral health concerns in patients after Roux-en-Y gastric bypass surgery.

BACKGROUND: The benefits of bariatric surgery are well-established, however, concerns surrounding postoperative psychiatric destabilization and alcohol misuse remain. Research has initiated the process of identifying risks associated with bariatric surgery, although less is known regarding when or why psychiatric hospitalizations occur postoperatively. OBJECTIVES: The goal of the current study was to examine the incidence of, and contributing factors to, behavioral health-related emergency room (ER) encounters and hospitalization after bariatric surgery. SETTING: Integrated multispecialty health system with an accredited bariatric surgery program. METHODS: Retrospective review of patients who underwent Roux-en-Y gastric bypass (RYGB) surgery and had been readmitted to the hospital or presented to the ER after bariatric surgery at least once for a behavioral-health related reason. RESULTS: Of 1449 patients, 93 had at least 1 psychiatric or substance use-related ER visit/hospitalization post-surgery and were included in the study; 53% had 1 ER/hospital encounter after bariatric surgery; 24% had 2 encounters, 11% had 3-4 encounters, and 10% of patients had ≥5 encounters. Across 267 postbariatric surgery encounters, 42.4% were due to alcohol-related problems. The index presentation for alcohol-related reasons occurred at a mean of 1942 days (approximately 5.3 yr; SD = 1217 d). Patients' index presentation for a psychiatric concern (41.3%) occurred at a mean of 1278 days (3.5 yr; SD = 1056 d) post-surgery. CONCLUSION: A significant percentage of patients who present to the ER or hospital for behavioral health reasons after RYGB surgery had alcohol-related problems, long after their surgery. Psychologists working with bariatric surgery teams should prioritize ongoing assessment of and education on alcohol misuse in those seeking RYGB and in the long-term postoperative period.

A biomechanical evaluation of different footrest heights during standing computer work.

Working at a standing desk is a popular strategy to help reduce low back pain development during prolonged computer work. The purpose of this study was to examine how muscle activity, joint kinematics, weight distribution, balance and low back discomfort were affected by utilising footrests at different heights while working at a standing desk. Sixteen individuals performed a computer task at a standing workstation under four conditions: flat ground stance, and standing with one leg elevated on a low (10 cm), medium (20 cm), or high (30 cm) footrest. Footrest usage altered lumbo-pelvic and bilateral hip joint angles, muscle activity, weight distribution, and range of sway in the elevated limb. Additionally, footrest height altered lumbo-pelvic and hip joint position in the elevated limb. Discomfort increased with time across all conditions. Results suggest that intermittent utilisation of a footrest should be considered to promote changes in posture and muscle activity during prolonged computer use. Practitioner summary: This laboratory study showed that utilising a footrest between the heights of 10-30 cm during standing computer work may be beneficial to promote changes in posture and muscle activity over time. However, we recommend exercising caution while maintaining any standing position beyond 10 min of consecutive use. Abbreviations: LBP: low back pain; PD: pain developer; NPD: non-pain developer; GMe: gluteus medius; TFL: tensor fascia lata; LES: lumbar erector spinae; COP: centre of pressure; NDI: northern digital incorporated; CV: coefficient of variation; WHQ: waterloo handedness questionnaire; WFQ: waterloo footedness questionnaire; VAS: visual analogue scale; OBDI: Oswestry back disability index; IBS: International Society of Biomechanics; sEMG: surface electromyography; MVIC: maximum voluntary isometric contraction; RMS: root mean square; A/P: anterior/posterior; M/L: medial/lateral; % MVE: percentage of maximum voluntary excitation; ROM: range of motion; MCID: minimum clinically important difference.

Nine Degree-of-Freedom Kinematic Modeling of the Upper-Limb Complex for Constrained Workspace Evaluation.

The design of rehabilitation devices for patients experiencing musculoskeletal disorders (MSDs) requires a great deal of attention. This article aims to develop a comprehensive model of the upper-limb complex to guide the design of robotic rehabilitation devices that prioritize patient safety, while targeting effective rehabilitative treatment. A 9 degree-of-freedom kinematic model of the upper-limb complex is derived to assess the workspace of a constrained arm as an evaluation method of such devices. Through a novel differential inverse kinematic method accounting for constraints on all joints1820, the model determines the workspaces in which a patient is able to perform rehabilitative tasks and those regions where the patient needs assistance due to joint range limitations resulting from an MSD. Constraints are imposed on each joint by mapping the joint angles to saturation functions, whose joint-space derivative near the physical limitation angles approaches zero. The model Jacobian is reevaluated based on the nonlinearly mapped joint angles, providing a means of compensating for redundancy while guaranteeing feasible inverse kinematic solutions. The method is validated in three scenarios with different constraints on the elbow and palm orientations. By measuring the lengths of arm segments and the range of motion for each joint, the total workspace of a patient experiencing an upper-limb MSD can be compared to a preinjured state. This method determines the locations in which a rehabilitation device must provide assistance to facilitate movement within reachable space that is limited by any joint restrictions resulting from MSDs.

Measuring the Hubble constant with a sample of kilonovae.

Kilonovae produced by the coalescence of compact binaries with at least one neutron star are promising standard sirens for an independent measurement of the Hubble constant (H0). Through their detection via follow-up of gravitational-wave (GW), short gamma-ray bursts (sGRBs) or optical surveys, a large sample of kilonovae (even without GW data) can be used for H0 contraints. Here, we show measurement of H0 using light curves associated with four sGRBs, assuming these are attributable to kilonovae, combined with GW170817. Including a systematic uncertainty on the models that is as large as the statistical ones, we find [Formula: see text] and [Formula: see text] for two different kilonova models that are consistent with the local and inverse-distance ladder measurements. For a given model, this measurement is about a factor of 2-3 more precise than the standard-siren measurement for GW170817 using only GWs.

Enhanced Notch3 signaling contributes to pulmonary emphysema in a Murine Model of Marfan syndrome.

Marfan syndrome (MFS) is a heritable disorder of connective tissue, caused by mutations in the fibrillin-1 gene. Pulmonary functional abnormalities, such as emphysema and restrictive lung diseases, are frequently observed in patients with MFS. However, the pathogenesis and molecular mechanism of pulmonary involvement in MFS patients are underexplored. Notch signaling is essential for lung development and the airway epithelium regeneration and repair. Therefore, we investigated whether Notch3 signaling plays a role in pulmonary emphysema in MFS. By using a murine model of MFS, fibrillin-1 hypomorphic mgR mice, we found pulmonary emphysematous-appearing alveolar patterns in the lungs of mgR mice. The septation in terminal alveoli of lungs in mgR mice was reduced compared to wild type controls in the early lung development. These changes were associated with increased Notch3 activation. To confirm that the increased Notch3 signaling in mgR mice was responsible for structure alterations in the lungs, mice were treated with N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglucine t-butyl ester (DAPT), a γ-secretase inhibitor, which inhibits Notch signaling. DAPT treatment reduced lung cell apoptosis and attenuated pulmonary alteration in mice with MFS. This study indicates that Notch3 signaling contributes to pulmonary emphysema in mgR mice. Our results may have the potential to lead to novel strategies to prevent and treat pulmonary manifestations in patients with MFS.

Surveillance Intensity Comparison by Risk for T1NX Locally Excised Rectal Adenocarcinoma: a Cost-Effective Analysis.

BACKGROUND: Controversy exists regarding the optimal surveillance strategy following local excision of T1NX rectal adenocarcinoma. This study aims to determine the cost-effectiveness of surveillance strategies for locally excised T1NX rectal adenocarcinoma based on histopathologic and local staging risk factors. METHODS: A Markov model with 10-year follow-up was developed for cost-effectiveness analysis of high-, medium-, and low-intensity surveillance strategies after local excision of T1NX rectal adenocarcinoma. Literature review and expert consensus were utilized to populate state/transition probabilities and rewards. Based on this data, 87% of T1NX patients undergoing local excision were low risk. Healthcare utilization costs were based on Centers for Medicare and Medicaid Services data. The primary outcomes were costs in 2018 US dollars and effectiveness in life-years presented as net monetary benefit and incremental cost-effectiveness ratios. One-way sensitivity and probabilistic sensitivity analyses were performed. RESULTS: Net monetary benefit for low-, medium-, and high-intensity surveillance strategies ($393,117.00, $397,978.80, and $397,290.00) shows medium-intensity surveillance to be optimal. One-way sensitivity analysis shows medium-intensity surveillance to be optimal when the cohort is 73-94% low risk. High-intensity surveillance is preferred when less than 73% of the cohort is low risk. Low-intensity surveillance is preferred when greater than 94% is low risk. Probabilistic sensitivity analysis of the base-case shows medium-intensity surveillance is the optimal strategy for 51.5% of the iterations performed. CONCLUSIONS: Medium-intensity surveillance is the most cost-effective surveillance strategy for locally excised T1NX rectal adenocarcinoma in a clinically representative population model.

Disrupting prolonged sitting reduces IL-8 and lower leg swell in active young adults.

BACKGROUND: Evidence suggests that disrupting prolonged bouts of sitting with short bouts of physical activity can significantly reduce blood glucose and improve insulin sensitivity; however, limited research is available on the impact of such disruptions on inflammation and swelling. The purpose of this study was to determine whether short bouts of exercise performed each hour during a 4 h sitting session were able to negate the effects of prolonged sitting (PS) on several cardiometabolic outcomes. METHODS: Eligible participants (n = 10) attended two laboratory sessions: PS (uninterrupted sitting for 4 h) and disrupted sitting (DS; 4 h sitting session disrupted by 3 min of exercise each hour (60-s warm-up at 50 W, 5 s of unloaded cycling, 20-s sprint at 5% body weight, and 95-s cool-down at 50 W)). The exercise bouts were performed at minute 60, 120, and 180. Blood and saliva samples, and measures of heart rate and blood pressure were assessed before (T1) and after (T2) each session; leg swell was measured continuously. RESULTS: Concentrations of salivary IL-8 increased during PS (T1: 0.19 ± 0.32; T2: 0.50 ± 1.00 pg/µg of protein) but decreased during DS (T1: 0.41 ± 0.23; T2: 0.22 ± 0.11 pg/µg of protein, d: 0.51, p = 0.002). Leg swell increased and plateaued in PS, but was attenuated during DS. CONCLUSION: It appears that short bouts of exercise significantly reduce swelling in the lower leg and IL-8 levels in the saliva, indicating that even among healthy, active, young adults, disrupting prolonged sitting can significantly reduce swelling and systemic inflammation.

Estimates of persistent inward current in human motor neurons during postural sway.

Persistent inward current (PIC) plays a critical role in setting the gain of spinal motor neurons. In humans, most estimates of PIC are made from plantarflexor or dorsiflexor motor units in a seated position. This seated and static posture negates the task-dependent nature of the monoaminergic drive and afferent inhibition that modulate PIC activation. Our purpose was to estimate PIC during both the conventional seated posture and in a more functionally relevant anterior postural sway. We hypothesized that paired motor unit estimates of PIC would be greater when during standing compared with sitting. Soleus motor neuron PIC was estimated via the paired motor unit (PMU) technique. For each motor unit pair, difference in reference unit firing frequency (ΔF) estimates of PIC were made during isometric ramps in plantarflexion force during sitting (conventional approach) and during standing anterior postural sway (new approach). Baseline reciprocal inhibition (RI) was also measured in each posture using the poststimulus time histogram technique. ΔF estimates during standing postural sway were not different [2.64 ± 0.95 pulses/s (pps), P = 0.098] from seated PIC estimates (3.15 ± 1.45 pps) measured from the same motor unit pair. Similarly, reciprocal inhibition at the onset of each task was the same in standing (-0.60 ± 0.32, P = 0.301) and seated (-0.86 ± 0.82) postures. PMU recordings made during standing postural sway met all assumptions that underlay the PMU technique, including rate modulation ≥0.5 pps (3.11 ± 1.90 pps), rate-rate correlation r ≥ 0.7 (0.84 ± 0.13), and time between reference and test unit recruitment ≥1 s (1.83 ± 0.81 s). This study presents a novel, functionally relevant standing method for investigating PIC in humans.NEW & NOTEWORTHY Paired motor unit (PMU) estimates of persistent inward current (PIC) in human soleus motor units are typically made in seated posture. Our study demonstrates that these estimates can be made during standing forward sway, a task that more accurately reflects the postural role of human soleus muscle. PMU recordings made during standing postural sway were validated using all previously published criteria used to test the assumptions of the PMU technique. Standing estimates of PIC did not differ from seated estimates made from the same motor unit pairs.

EFFECTS OF A BAND LOOP ON LOWER EXTREMITY MUSCLE ACTIVITY AND KINEMATICS DURING THE BARBELL SQUAT.

BACKGROUND: Medial knee collapse can signal an underlying movement issue that, if uncorrected, can lead to a variety of knee injuries. Placing a band around the distal thigh may act as a proprioceptive aid to minimize medial collapse of the knee during squats; however, little is known about EMG and biomechanics in trained and untrained individuals during the squat with an elastic band added. HYPOTHESIS/PURPOSE: To investigate the effects of the TheraBand® Band Loop on kinematics and muscle activity of the lower extremity during a standard barbell back squat at different intensities in both trained and untrained individuals. STUDY DESIGN: Cross-sectional, repeated measures. METHODS: Sixteen healthy, male, university aged-participants were split into two groups of eight, consisting of a trained and untrained group. Participants performed both a 3-repetition maximum (3-RM) and a bodyweight load squat for repetitions to failure. Lower extremity kinematics and surface electromyography of four muscles were measured bilaterally over two sessions, an unaided squat and a band session (band loop placed around distal thighs). Medial knee collapse, measured as a knee width index, and maximum muscle activity were calculated. RESULTS: During the 3-RM, squat weight was unaffected by band loop intervention (p = 0.486) and the trained group lifted more weight than the untrained group (p<0.007). The trained group had a greater squat depth for both squat conditions, regardless of the band (p = 0.0043). Knee width index was not affected by the band during the eccentric phase of bodyweight squats in the trained (band: 0.76 ± 0.08, no band: 0.73 ± 0.08) or untrained group (band: 0.77 ± 0.70, no band: 0.75 ± 0.13) (p = 0.670). During the concentric phase, knee width index was significantly lower for 3-RM squats, regardless of group. CONCLUSION: Despite minimal changes in kinematics for the untrained group, increased muscle activity with the band loop may suggest that a training aid may, over time, lead to an increase in barbell squat strength by increasing activation of agonist muscles more than traditional, un-banded squats. Greater maximal muscle activity in most muscles during band loop sessions may provide enhanced knee stability via increased activation of stabilizing muscles. LEVEL OF EVIDENCE: 3.

Tractography guides the approach for resection of thalamopeduncular tumors.

BACKGROUND: Thalamopeduncular tumors arise at the junction of the inferior thalamus and cerebral peduncle, and present with a common clinical syndrome of progressive spastic hemiparesis. METHOD: Formal preoperative magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were performed. Postoperative MRI was obtained to evaluate the extent of tumor resection. A prospective analysis of clinical outcomes was then conducted by the senior author. CONCLUSIONS: Preoperative tractography is a useful adjunct to surgical planning in tumors that displace motor pathways. Gross total resection of pilocytic astrocytomas usually results in cure, and therefore should be entertained when developing treatment strategies for thalamopeduncular tumors of childhood.

Sonography of traumatic quadriceps tendon tears with surgical correlation.

OBJECTIVES: Using surgical correlation as the reference standard, the purpose of this study was to assess the ability of sonography to detect quadriceps tendon tears that require surgical treatment (high-grade partial tears and complete ruptures). METHODS: Two hundred thirty-nine consecutive sonographic reports of the knee (May 2001 to October 2008) with subsequent surgical correlation were retrospectively reviewed for surgical intervention on the quadriceps tendon. All sonograms were blindly and retrospectively reviewed. Surgical findings were compared with results from the consensus review. Results from the original sonographic reports (nonretrospective interpretation) were also compared with the surgical findings. RESULTS: On the retrospective consensus review, the sensitivity (23 of 23), specificity (16 of 16), and accuracy (39 of 39) were 100% for identifying high-grade partial tears or complete ruptures versus a normal quadriceps tendon. For the original, nonretrospective sonographic reports, 22 of 23 high-grade partial tears or complete ruptures (96%) were correctly diagnosed. CONCLUSIONS: Sonography is an effective tool for identifying quadriceps tendon tears that require surgical treatment (high-grade partial tears and complete ruptures).

Astrophysics. Multiple images of a highly magnified supernova formed by an early-type cluster galaxy lens.

In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z = 0.54 elliptical galaxy in the MACS J1149.6+2223 cluster. The cluster's gravitational potential also creates multiple images of the z = 1.49 spiral supernova host galaxy, and a future appearance of the supernova elsewhere in the cluster field is expected. The magnifications and staggered arrivals of the supernova images probe the cosmic expansion rate, as well as the distribution of matter in the galaxy and cluster lenses.

A luminous, blue progenitor system for the type Iax supernova 2012Z.

Type Iax supernovae are stellar explosions that are spectroscopically similar to some type Ia supernovae at the time of maximum light emission, except with lower ejecta velocities. They are also distinguished by lower luminosities. At late times, their spectroscopic properties diverge from those of other supernovae, but their composition (dominated by iron-group and intermediate-mass elements) suggests a physical connection to normal type Ia supernovae. Supernovae of type Iax are not rare; they occur at a rate between 5 and 30 per cent of the normal type Ia rate. The leading models for type Iax supernovae are thermonuclear explosions of accreting carbon-oxygen white dwarfs that do not completely unbind the star, implying that they are 'less successful' versions of normal type Ia supernovae, where complete stellar disruption is observed. Here we report the detection of the luminous, blue progenitor system of the type Iax SN 2012Z in deep pre-explosion imaging. The progenitor system's luminosity, colours, environment and similarity to the progenitor of the Galactic helium nova V445 Puppis suggest that SN 2012Z was the explosion of a white dwarf accreting material from a helium-star companion. Observations over the next few years, after SN 2012Z has faded, will either confirm this hypothesis or perhaps show that this supernova was actually the explosive death of a massive star.

Readability of the Patient Education Section of the AOFAS Website.

BACKGROUND: One of the goals of the AOFAS website is to provide easily understandable information about orthopaedic foot and ankle conditions to the public. However, validation of this goal has not been conducted. Evaluation of text reading level is frequently performed using the Flesch-Kincaid formula (FKF). This study evaluated whether the patient information section of the AOFAS website meets recommended readability guidelines for medical information. MATERIALS AND METHODS: Seventy-nine publicly accessible entries within the patient education section of the AOFAS website were analyzed for grade level readability using the FKF. RESULTS: Two entries were unable to be effectively evaluated using the FKF. The average grade reading level of all patient education entries was 8.3 (95% CI 7.8 to 8.9). Only 20.8% of entries were at or below a 6th grade reading level. Almost 30% were above the 8th grade level. The average grade levels of the constituent sections were: ;;Ailments and Conditions'', 8.7; ;;Steps to Recovery'', 7.1; ;;Adult Feet'', 8.3; ;;Children's Feet'', 7.5; ;;Foot Health and Fitness'', 7.8; ;;Shoes'', 8.5; and ;;Glossary'', 10.1. The percentage of entries within these sections below a 7th grade reading level were 13%, 30%, 0%, 0%, 43%, 24% and 0%, respectively. CONCLUSION: The percentage of entries at or below the recommended 6th grade reading level on the AOFAS website compared favorably with other orthopaedic organizations' websites. However, the majority still exceeds a recommended reading level. To enhance the readability of patient education materials, we believe use of computer aided readability assessment tools should be considered in future website revisions.

A non-spherical core in the explosion of supernova SN 2004dj.

An important and perhaps critical clue to the mechanism driving the explosion of massive stars as supernovae is provided by the accumulating evidence for asymmetry in the explosion. Indirect evidence comes from high pulsar velocities, associations of supernovae with long-soft gamma-ray bursts, and asymmetries in late-time emission-line profiles. Spectropolarimetry provides a direct probe of young supernova geometry, with higher polarization generally indicating a greater departure from spherical symmetry. Large polarizations have been measured for 'stripped-envelope' (that is, type Ic; ref. 7) supernovae, which confirms their non-spherical morphology; but the explosions of massive stars with intact hydrogen envelopes (type II-P supernovae) have shown only weak polarizations at the early times observed. Here we report multi-epoch spectropolarimetry of a classic type II-P supernova that reveals the abrupt appearance of significant polarization when the inner core is first exposed in the thinning ejecta (approximately 90 days after explosion). We infer a departure from spherical symmetry of at least 30 per cent for the inner ejecta. Combined with earlier results, this suggests that a strongly non-spherical explosion may be a generic feature of core-collapse supernovae of all types, where the asphericity in type II-P supernovae is cloaked at early times by the massive, opaque, hydrogen envelope.

An asymmetric energetic type Ic supernova viewed off-axis, and a link to gamma ray bursts.

Type Ic supernovae, the explosions after the core collapse of massive stars that have previously lost their hydrogen and helium envelopes, are particularly interesting because of their link with long-duration gamma ray bursts. Although indications exist that these explosions are aspherical, direct evidence has been missing. Late-time observations of supernova SN 2003jd, a luminous type Ic supernova, provide such evidence. Recent Subaru and Keck spectra reveal double-peaked profiles in the nebular lines of neutral oxygen and magnesium. These profiles are different from those of known type Ic supernovae, with or without a gamma ray burst, and they can be understood if SN 2003jd was an aspherical axisymmetric explosion viewed from near the equatorial plane. If SN 2003jd was associated with a gamma ray burst, we missed the burst because it was pointing away from us.