Institute of Astronomy

Astronomy News

Dark-matter hunt fails to find the elusive particles

9 November 2017 - 9:39am

Dark-matter hunt fails to find the elusive particles

Nature 551, 7679 (2017). http://www.nature.com/doifinder/10.1038/551153a

Author: Elizabeth Gibney

Physicists begin to embrace alternative explanations for the missing material.

'Zombie' star survived going supernova

9 November 2017 - 9:36am

Astronomers discover the astronomical equivalent of a horror film villain: a star that wouldn't stay dead.

Powering Saturn's Active Ocean Moon

8 November 2017 - 9:17am

Heat from friction could power hydrothermal activity on Saturn's moon Enceladus for billions of years if the moon has a highly porous core, according to a new modeling study by European and U.S. researchers working on NASA's Cassini mission.

News Article Type: Homepage ArticlesPublished: Tuesday, November 7, 2017 - 12:13

<p>A black hole’s jets light up in less than a second</p>

8 November 2017 - 9:17am

A black hole’s jets light up in less than a second

<p>A black hole’s jets light up in less than a second</p>, Published online: 06 November 2017; doi:10.1038/d41586-017-05527-2

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Plasma jets start to shine just after less-fortunate material swirls towards its doom.

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Enceladus’s hot, gritty core may cook up ingredients for life

7 November 2017 - 10:11am

Saturn’s moon Enceladus seems to have a sandy core that warms water passing between the grains. This heating could help create conditions that are right for life

Electronics Demonstrate Operability in Simulated Venus Conditions

7 November 2017 - 10:10am
Technology Development 

NASA’s future planetary exploration efforts, including missions to Venus, require electronics capable of surviving temperatures of 470° C and above for long durations. Such durable electronics eliminate the need for cooling systems to enable sustained operations. Previous operation of electronics at Venus surface conditions (e.g., in Venus missions) has been limited to a few hours in a protected pressure/temperature enclosure, due to the extreme environment. Standard electronics used commercially and for planetary exploration are based on silicon semiconductors, which do not operate at Venus temperatures. A team at NASA Glenn Research Center (GRC) has been working to develop hightemperature electronics based on silicon carbide (SiC) semiconductors that can operate at Venus temperatures and above. Recently, the team demonstrated that a variety of the world’s first moderately complex SiC-based microcircuits (tens or more of transistors) could withstand up to 4000 hours of operation at 500° C. These demonstrations included core circuits such as digital logic circuits and analog operational amplifiers that are used throughout electronic systems.

Top: GEER replicates Venus simulated surface conditions, including temperature, pressure, and chemical composition. Bottom: High temperature ring oscillator continues stable operation in these “Venus conditions” for 521 hours.

Testing of two these circuits occurred in the Glenn Extreme Environments Rig (GEER), which simulates Venus surface conditions including high temperature and pressure. In April 2016, the team demonstrated a SiC high-temperature 12-transistor ring oscillator at Venus surface conditions (460° C, 93 atm pressure, supercritical CO² and trace gases) in the GEER for 21.7 days (521 hours) with good stability throughout the entire test. This Venus surface demonstration of moderately complex electronics is a significant world record—orders of magnitude in duration beyond any other Venus surface condition electronics demonstration. Testing in Venus conditions was ended after 21 days for scheduling reasons; similar ring oscillator circuits have shown thousands of hours of operations at 500° C in Earth-air ambient oven conditions.

SiC high-temperature electronics before and after testing in Venus surface conditions (rugged operation for extended durations). (Credits: top: Marvin Smith, NASA GRC; Bottom: David Spry, NASA GRC) Impact 

These advances are a paradigm shift that broadly enables new science exploration, especially for the Venus surface. SMD began a project in FY17—the Long-Life In-situ Solar System Explorer (LLISSE)—that will incorporate these new SiC electronics. LLISSE is developing a functioning prototype of a low-cost scientific probe capable of providing basic, but highvalue, science measurements from the surface of Venus continuously for months or longer. Such a probe was not viable previously, and will revolutionize our understanding of the Venus surface. This new technology also impacts potential development of probes exploring the Gas Giants (Jupiter, Saturn, Uranus and Neptune) or the surface of Mercury. SiCbased electronics could also enable an intelligent aeronautics engine to monitor and respond to its own health state, and could be used in a range of commercial applications, such as deep oil well drilling or industrial processing.

Status and Future Plans 

In August 2016, the team completed fabrication of “next-generation” extreme temperature integrated circuit wafers featuring significantly more complex digital and analog circuits (more than 100 transistors). In October, the team initiated prolonged 500° C testing (Earth-air atmosphere) of “next-generation” integrated circuits with more than 100 transistors. Plans include producing increasingly complex high temperature SiC electronics to meet the needs of the LLISSE project and other applications. NASA will use a “design and build” approach to increase the capabilities of the basic electronics components, while providing new circuit types as needed for specific applications.

Sponsoring Organization

Multiple projects have supported this technology development in 2016. PSD’s PICASSO program sponsored work to develop a range of SiC core circuits for multiple applications and missions. SMD’s LLISSE Project worked to refine high-temperature SiC circuits for use on a Venus surface lander. Additionally, the NASA Aeronautics Research Mission Directorate’s Transformative Tool and Technologies Project supported development of high-temperature electronics for aeronautic engine applications.

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Heating ocean moon Enceladus for billions of years

7 November 2017 - 10:09am

Enough heat to power hydrothermal activity inside Saturn's ocean moon Enceladus for billions of years could be generated through tidal friction if the moon has a highly porous core, a new study finds, working in favour of the moon as a potentially habitable world.

Return of the Comet: 96P Spotted by ESA, NASA Satellites

6 November 2017 - 9:22am
Portal origin URL: Return of the Comet: 96P Spotted by ESA, NASA SatellitesPortal origin nid: 412733Published: Friday, November 3, 2017 - 09:28Featured (stick to top of list): noPortal text teaser: Sun-gazing missions SOHO and STEREO watched the return of comet 96P/Machholz when it entered their fields of view between Oct. 25-30. It is extremely rare for comets to be seen simultaneously from two different locations in space, and these are the most comprehensive parallel observations ever taken of this comet.Portal image: animation of STEREO observations of comet 96PScience Categories: Sun

Hubble Sees Nearby Asteroids Photobombing Distant Galaxies

6 November 2017 - 9:22am

Like rude relatives who jump in front of your vacation snapshots of landscapes, some of our solar system's asteroids have photobombed deep images of the universe taken by NASA's Hubble Space Telescope. These asteroids reside, on average, only about 160 million miles from Earth — right around the corner in astronomical terms. Yet they've horned their way into this picture of thousands of galaxies scattered across space and time at inconceivably farther distances.

News Article Type: Homepage ArticlesPublished: Friday, November 3, 2017 - 15:08

ALMA Discovers Cold Dust Around Nearest Star

6 November 2017 - 9:21am
The ALMA Observatory in Chile has detected dust around the closest star to the Solar System, Proxima Centauri. These new observations reveal the glow coming from cold dust in a region between one to four times as far from Proxima Centauri as the Earth is from the Sun. The data also hint at the presence of an even cooler outer dust belt and may indicate the presence of an elaborate planetary system. These structures are similar to the much larger belts in the Solar System and are also expected to be made from particles of rock and ice that failed to form planets.

Why Hawking’s PhD thesis is now an internet-breaking inspiration

3 November 2017 - 8:57am

Millions rushed to freely access Stephen Hawking's early musings when they went online. More of the same would help ignite young minds everywhere, says Geraint Lewis

Launch your design with CHEOPS

3 November 2017 - 8:55am

ESA is offering graphic designers and artists a unique opportunity to feature their work on the rocket carrying the CHEOPS satellite.

A gravitational-wave standard siren measurement of the Hubble constant

2 November 2017 - 9:22am

A gravitational-wave standard siren measurement of the Hubble constant

Nature 551, 7678 (2017). doi:10.1038/nature24471

Authors:

On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817—a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO–Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first ‘multi-messenger’ astronomical observation. Such observations enable GW170817 to be used as a ‘standard siren’ (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic ‘distance ladder’: the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.

Origin of the heavy elements in binary neutron-star mergers from a gravitational-wave event

2 November 2017 - 9:22am

Origin of the heavy elements in binary neutron-star mergers from a gravitational-wave event

Nature 551, 7678 (2017). doi:10.1038/nature24453

Authors: Daniel Kasen, Brian Metzger, Jennifer Barnes, Eliot Quataert & Enrico Ramirez-Ruiz

The cosmic origin of elements heavier than iron has long been uncertain. Theoretical modelling shows that the matter that is expelled in the violent merger of two neutron stars can assemble into heavy elements such as gold and platinum in a process known as rapid neutron capture (r-process) nucleosynthesis. The radioactive decay of isotopes of the heavy elements is predicted to power a distinctive thermal glow (a ‘kilonova’). The discovery of an electromagnetic counterpart to the gravitational-wave source GW170817 represents the first opportunity to detect and scrutinize a sample of freshly synthesized r-process elements. Here we report models that predict the electromagnetic emission of kilonovae in detail and enable the mass, velocity and composition of ejecta to be derived from observations. We compare the models to the optical and infrared radiation associated with the GW170817 event to argue that the observed source is a kilonova. We infer the presence of two distinct components of ejecta, one composed primarily of light (atomic mass number less than 140) and one of heavy (atomic mass number greater than 140) r-process elements. The ejected mass and a merger rate inferred from GW170817 imply that such mergers are a dominant mode of r-process production in the Universe.

A kilonova as the electromagnetic counterpart to a gravitational-wave source

2 November 2017 - 9:22am

A kilonova as the electromagnetic counterpart to a gravitational-wave source

Nature 551, 7678 (2017). doi:10.1038/nature24303

Authors: S. J. Smartt, T.-W. Chen, A. Jerkstrand, M. Coughlin, E. Kankare, S. A. Sim, M. Fraser, C. Inserra, K. Maguire, K. C. Chambers, M. E. Huber, T. Krühler, G. Leloudas, M. Magee, L. J. Shingles, K. W. Smith, D. R. Young, J. Tonry, R. Kotak, A. Gal-Yam, J. D. Lyman, D. S. Homan, C. Agliozzo, J. P. Anderson, C. R. Angus, C. Ashall, C. Barbarino, F. E. Bauer, M. Berton, M. T. Botticella, M. Bulla, J. Bulger, G. Cannizzaro, Z. Cano, R. Cartier, A. Cikota, P. Clark, A. De Cia, M. Della Valle, L. Denneau, M. Dennefeld, L. Dessart, G. Dimitriadis, N. Elias-Rosa, R. E. Firth, H. Flewelling, A. Flörs, A. Franckowiak, C. Frohmaier, L. Galbany, S. González-Gaitán, J. Greiner, M. Gromadzki, A. Nicuesa Guelbenzu, C. P. Gutiérrez, A. Hamanowicz, L. Hanlon, J. Harmanen, K. E. Heintz, A. Heinze, M.-S. Hernandez, S. T. Hodgkin, I. M. Hook, L. Izzo, P. A. James, P. G. Jonker, W. E. Kerzendorf, S. Klose, Z. Kostrzewa-Rutkowska, M. Kowalski, M. Kromer, H. Kuncarayakti, A. Lawrence, T. B. Lowe, E. A. Magnier, I. Manulis, A. Martin-Carrillo, S. Mattila, O. McBrien, A. Müller, J. Nordin, D. O’Neill, F. Onori, J. T. Palmerio, A. Pastorello, F. Patat, G. Pignata, Ph. Podsiadlowski, M. L. Pumo, S. J. Prentice, A. Rau, A. Razza, A. Rest, T. Reynolds, R. Roy, A. J. Ruiter, K. A. Rybicki, L. Salmon, P. Schady, A. S. B. Schultz, T. Schweyer, I. R. Seitenzahl, M. Smith, J. Sollerman, B. Stalder, C. W. Stubbs, M. Sullivan, H. Szegedi, F. Taddia, S. Taubenberger, G. Terreran, B. van Soelen, J. Vos, R. J. Wainscoat, N. A. Walton, C. Waters, H. Weiland, M. Willman, P. Wiseman, D. E. Wright, Ł. Wyrzykowski & O. Yaron

Gravitational waves were discovered with the detection of binary black-hole mergers and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova. The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate. Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short γ-ray burst. The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 ± 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 ± 0.1 times light speed. The power source is constrained to have a power-law slope of −1.2 ± 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90–140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.

The X-ray counterpart to the gravitational-wave event GW170817

2 November 2017 - 9:22am

The X-ray counterpart to the gravitational-wave event GW170817

Nature 551, 7678 (2017). doi:10.1038/nature24290

Authors: E. Troja, L. Piro, H. van Eerten, R. T. Wollaeger, M. Im, O. D. Fox, N. R. Butler, S. B. Cenko, T. Sakamoto, C. L. Fryer, R. Ricci, A. Lien, R. E. Ryan, O. Korobkin, S.-K. Lee, J. M. Burgess, W. H. Lee, A. M. Watson, C. Choi, S. Covino, P. D’Avanzo, C. J. Fontes, J. Becerra González, H. G. Khandrika, J. Kim, S.-L. Kim, C.-U. Lee, H. M. Lee, A. Kutyrev, G. Lim, R. Sánchez-Ramírez, S. Veilleux, M. H. Wieringa & Y. Yoon

A long-standing paradigm in astrophysics is that collisions—or mergers—of two neutron stars form highly relativistic and collimated outflows (jets) that power γ-ray bursts of short (less than two seconds) duration. The observational support for this model, however, is only indirect. A hitherto outstanding prediction is that gravitational-wave events from such mergers should be associated with γ-ray bursts, and that a majority of these bursts should be seen off-axis, that is, they should point away from Earth. Here we report the discovery observations of the X-ray counterpart associated with the gravitational-wave event GW170817. Although the electromagnetic counterpart at optical and infrared frequencies is dominated by the radioactive glow (known as a ‘kilonova’) from freshly synthesized rapid neutron capture (r-process) material in the merger ejecta, observations at X-ray and, later, radio frequencies are consistent with a short γ-ray burst viewed off-axis. Our detection of X-ray emission at a location coincident with the kilonova transient provides the missing observational link between short γ-ray bursts and gravitational waves from neutron-star mergers, and gives independent confirmation of the collimated nature of the γ-ray-burst emission.

Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger

2 November 2017 - 9:21am

Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger

Nature 551, 7678 (2017). doi:10.1038/nature24298

Authors: E. Pian, P. D’Avanzo, S. Benetti, M. Branchesi, E. Brocato, S. Campana, E. Cappellaro, S. Covino, V. D’Elia, J. P. U. Fynbo, F. Getman, G. Ghirlanda, G. Ghisellini, A. Grado, G. Greco, J. Hjorth, C. Kouveliotou, A. Levan, L. Limatola, D. Malesani, P. A. Mazzali, A. Melandri, P. Møller, L. Nicastro, E. Palazzi, S. Piranomonte, A. Rossi, O. S. Salafia, J. Selsing, G. Stratta, M. Tanaka, N. R. Tanvir, L. Tomasella, D. Watson, S. Yang, L. Amati, L. A. Antonelli, S. Ascenzi, M. G. Bernardini, M. Boër, F. Bufano, A. Bulgarelli, M. Capaccioli, P. Casella, A. J. Castro-Tirado, E. Chassande-Mottin, R. Ciolfi, C. M. Copperwheat, M. Dadina, G. De Cesare, A. Di Paola, Y. Z. Fan, B. Gendre, G. Giuffrida, A. Giunta, L. K. Hunt, G. L. Israel, Z.-P. Jin, M. M. Kasliwal, S. Klose, M. Lisi, F. Longo, E. Maiorano, M. Mapelli, N. Masetti, L. Nava, B. Patricelli, D. Perley, A. Pescalli, T. Piran, A. Possenti, L. Pulone, M. Razzano, R. Salvaterra, P. Schipani, M. Spera, A. Stamerra, L. Stella, G. Tagliaferri, V. Testa, E. Troja, M. Turatto, S. D. Vergani & D. Vergani

The merger of two neutron stars is predicted to give rise to three major detectable phenomena: a short burst of γ-rays, a gravitational-wave signal, and a transient optical–near-infrared source powered by the synthesis of large amounts of very heavy elements via rapid neutron capture (the r-process). Such transients, named ‘macronovae’ or ‘kilonovae’, are believed to be centres of production of rare elements such as gold and platinum. The most compelling evidence so far for a kilonova was a very faint near-infrared rebrightening in the afterglow of a short γ-ray burst at redshift z = 0.356, although findings indicating bluer events have been reported. Here we report the spectral identification and describe the physical properties of a bright kilonova associated with the gravitational-wave source GW170817 and γ-ray burst GRB 170817A associated with a galaxy at a distance of 40 megaparsecs from Earth. Using a series of spectra from ground-based observatories covering the wavelength range from the ultraviolet to the near-infrared, we find that the kilonova is characterized by rapidly expanding ejecta with spectral features similar to those predicted by current models. The ejecta is optically thick early on, with a velocity of about 0.2 times light speed, and reaches a radius of about 50 astronomical units in only 1.5 days. As the ejecta expands, broad absorption-like lines appear on the spectral continuum, indicating atomic species produced by nucleosynthesis that occurs in the post-merger fast-moving dynamical ejecta and in two slower (0.05 times light speed) wind regions. Comparison with spectral models suggests that the merger ejected 0.03 to 0.05 solar masses of material, including high-opacity lanthanides.

Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger

2 November 2017 - 9:20am

Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger

Nature 551, 7678 (2017). doi:10.1038/nature24291

Authors: Iair Arcavi, Griffin Hosseinzadeh, D. Andrew Howell, Curtis McCully, Dovi Poznanski, Daniel Kasen, Jennifer Barnes, Michael Zaltzman, Sergiy Vasylyev, Dan Maoz & Stefano Valenti

The merger of two neutron stars has been predicted to produce an optical–infrared transient (lasting a few days) known as a ‘kilonova’, powered by the radioactive decay of neutron-rich species synthesized in the merger. Evidence that short γ-ray bursts also arise from neutron-star mergers has been accumulating. In models of such mergers, a small amount of mass (10−4–10−2 solar masses) with a low electron fraction is ejected at high velocities (0.1–0.3 times light speed) or carried out by winds from an accretion disk formed around the newly merged object. This mass is expected to undergo rapid neutron capture (r-process) nucleosynthesis, leading to the formation of radioactive elements that release energy as they decay, powering an electromagnetic transient. A large uncertainty in the composition of the newly synthesized material leads to various expected colours, durations and luminosities for such transients. Observational evidence for kilonovae has so far been inconclusive because it was based on cases of moderate excess emission detected in the afterglows of γ-ray bursts. Here we report optical to near-infrared observations of a transient coincident with the detection of the gravitational-wave signature of a binary neutron-star merger and with a low-luminosity short-duration γ-ray burst. Our observations, taken roughly every eight hours over a few days following the gravitational-wave trigger, reveal an initial blue excess, with fast optical fading and reddening. Using numerical models, we conclude that our data are broadly consistent with a light curve powered by a few hundredths of a solar mass of low-opacity material corresponding to lanthanide-poor (a fraction of 10−4.5 by mass) ejecta.

Gravitational waves: A golden binary

2 November 2017 - 9:20am

Gravitational waves: A golden binary

Nature 551, 7678 (2017). doi:10.1038/nature24153

Authors: M. Coleman Miller

The discovery of gravitational waves from a neutron-star merger and the detection of the event across the electromagnetic spectrum give insight into many aspects of gravity and astrophysics. See Letter p.64, p.67, p.71, p.75 & p.80

Astrophysics: Chasing ghosts in Antarctica

2 November 2017 - 9:18am

Astrophysics: Chasing ghosts in Antarctica

Nature 551, 7678 (2017). doi:10.1038/551030a

Author: Alexandra Witze

Alexandra Witze welcomes a history of IceCube, an ambitious neutrino observatory.