astro-news from Institute of Astronomy Library in Inoreader
Solar physics: Solar atmosphere is a hotbed of activity

Solar physics: Solar atmosphere is a hotbed of activity

Nature 514, 7523 (2014). doi:10.1038/514406a

Explosions of plasma in the Sun's atmosphere can reach temperatures of nearly 100,000 °C, much hotter than scientists had expected.The finding is one of several about the region between the solar surface and the uppermost edge of the Sun's atmosphere, or corona, revealed by

Sun’s stroke keeps Kepler online

Sun’s stroke keeps Kepler online

Nature 514, 7523 (2014).

Author: Mark Zastrow

Space telescope beats mechanical failures to begin a second mission that will trace new celestial targets.

Astronomy: Hurling comets around a planetary nursery

Astronomy: Hurling comets around a planetary nursery

Nature 514, 7523 (2014). doi:10.1038/514440a

Authors: Aki Roberge

An analysis of hundreds of star-grazing comets in a young planetary system shows that they form two families: a group of old, dried-out comets and a younger group probably related to the break-up of a larger planetary body. See Letter p.462

Two families of exocomets in the β Pictoris system

Two families of exocomets in the β Pictoris system

Nature 514, 7523 (2014). doi:10.1038/nature13849

Authors: F. Kiefer, A. Lecavelier des Etangs, J. Boissier, A. Vidal-Madjar, H. Beust, A.-M. Lagrange, G. Hébrard & R. Ferlet

The young planetary system surrounding the star β Pictoris harbours active minor bodies. These asteroids and comets produce a large amount of dust and gas through collisions and evaporation, as happened early in the history of our Solar System. Spectroscopic observations of β Pictoris reveal a high rate of transits of small evaporating bodies, that is, exocomets. Here we report an analysis of more than 1,000 archival spectra gathered between 2003 and 2011, which provides a sample of about 6,000 variable absorption signatures arising from exocomets transiting the disk of the parent star. Statistical analysis of the observed properties of these exocomets allows us to identify two populations with different physical properties. One family consists of exocomets producing shallow absorption lines, which can be attributed to old exhausted (that is, strongly depleted in volatiles) comets trapped in a mean motion resonance with a massive planet. Another family consists of exocomets producing deep absorption lines, which may be related to the recent fragmentation of one or a few parent bodies. Our results show that the evaporating bodies observed for decades in the β Pictoris system are analogous to the comets in our own Solar System.

Characterizing and predicting the magnetic environment leading to solar eruptions

Characterizing and predicting the magnetic environment leading to solar eruptions

Nature 514, 7523 (2014). doi:10.1038/nature13815

Authors: Tahar Amari, Aurélien Canou & Jean-Jacques Aly

The physical mechanism responsible for coronal mass ejections has been uncertain for many years, in large part because of the difficulty of knowing the three-dimensional magnetic field in the low corona. Two possible models have emerged. In the first, a twisted flux rope moves out of equilibrium or becomes unstable, and the subsequent reconnection then powers the ejection. In the second, a new flux rope forms as a result of the reconnection of the magnetic lines of an arcade (a group of arches of field lines) during the eruption itself. Observational support for both mechanisms has been claimed. Here we report modelling which demonstrates that twisted flux ropes lead to the ejection, in support of the first model. After seeing a coronal mass ejection, we use the observed photospheric magnetic field in that region from four days earlier as a boundary condition to determine the magnetic field configuration. The field evolves slowly before the eruption, such that it can be treated effectively as a static solution. We find that on the fourth day a flux rope forms and grows (increasing its free energy). This solution then becomes the initial condition as we let the model evolve dynamically under conditions driven by photospheric changes (such as flux cancellation). When the magnetic energy stored in the configuration is too high, no equilibrium is possible and the flux rope is ‘squeezed’ upwards. The subsequent reconnection drives a mass ejection.

Two Families of Comets Found Around Nearby Star
The HARPS instrument at ESO’s La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.
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Dark matter signal points to exotic black-hole origins
If our best sign yet of dark matter is what it seems, then the supermassive black hole at the centre of our galaxy is a complex beast

Chaotic cosmic wombs may birth backwards planets
Rebel planets orbit their stars the wrong way around – and prenatal turmoil may be to blame

AUDIO: Are we alone in the Milky Way?
Prof Brian Cox muses on whether life here on Earth is unique within the Milky Way and what this might mean.
AUDIO: Scientists study ancient comet
A recently discovered comet has flown past Mars, giving scientists a unique chance to study an object from the farthest reaches of the Solar System.
Comet immortalised before close call with spacecraft
A comet making its first trip in from the Oort cloud was caught on camera before a near miss with four spacecraft currently orbiting the Red Planet

Orbiters on alert as comet skims Mars
Scientists should get a grandstand view of a comet on Sunday when it makes a dramatic flyby of Mars.
Where will New Horizons Go After Pluto?
Peering out to the dim, outer reaches of our solar system, NASA’s Hubble Space Telescope has uncovered three Kuiper Belt objects (KBOs) the agency’s New Horizons spacecraft could potentially visit after it flies by Pluto in July 2015.
2014 Orionid Meteor Shower
Earth is entering a stream of debris from Halley's Comet, parent of the annual Orionid meteor shower. Forecasters expect the shower to peak on Tuesday, Oct. 21st.
Hubble Finds Extremely Distant Galaxy through Cosmic Magnifying Glass

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Peering through a giant cosmic magnifying glass, NASA's Hubble Space Telescope has spotted one of the farthest, faintest, and smallest galaxies ever seen. The diminutive object is estimated to be more than 13 billion light-years away. This new detection is considered one of the most reliable distance measurements of a galaxy that existed in the early universe, said the Hubble researchers. Hubble detected the galaxy due to the lensing power of the mammoth galaxy cluster Abell 2744, nicknamed Pandora's Cluster. The cluster is so massive that its powerful gravity bends the light from galaxies far behind it, making the background objects appear larger and brighter in a phenomenon called gravitational lensing.

AUDIO: Science shines light on dark matter
Scientists from the University of Leicester say they may have solved one of the most enduring mysteries in modern physics: the nature of dark matter.
Name sought for comet landing site
The public are being invited to name the site on a comet where a European robot will try to land on 12 November.
Rosetta comet: More black swan than yellow duck
A fascination of comets is their blackness
Probing the past - Most reliable remote distance measurement yet [heic1423]
Using the NASA/ESA Hubble Space Telescope astronomers have made what may be the most reliable distance measurement yet of an object that existed in the Universe's formative years. The galaxy is one of the faintest, smallest and most distant galaxies ever seen and measuring its distance with this accuracy was possible due only to the incredibly detailed mapping of how giant galaxy clusters warp the space-time around them.
NASA’s Hubble Finds Extremely Distant Galaxy through Cosmic Magnifying Glass
Peering through a giant cosmic magnifying glass, NASA’s Hubble Space Telescope has spotted a tiny, faint galaxy -- one of the farthest galaxies ever seen. The diminutive object is estimated to be more than 13 billion light-years away.