PREVIOUS “HABITABLE PLANETS” – NEXT “ASTROBIOLOGY” There is on average one planet orbiting every star in the Universe . If this sounds exciting, you might wanna read the previous post in this series. Our Galaxy (the Milky Way) is an immense disk of gas and stars with a diameter of about 100 000 light years, hosting about 100 billion stars and, therefore, also about 100 billion planets. Take a deep breath. Now, it turns out the Milky Way is just one of 100 billion galaxies that populate our Universe, a colossal expanding stretch of spacetime with an age of 13.7 billion years. The math is trivial: There are about 10 000 000 000 000 000 000 000 = 10²² planets out there. This number is extremely large. Apparently larger than the number of grains of sand found in every beach and every desert on Earth. But how many of these planets host life? And in particular, HOW MANY PLANETS HOST INTELLIGENT LIFE WE MIGHT BE ABLE TO COMMUNICATE WITH? In order to estimate the number of technological civilizations that might exist among the stars, in 1961 Frank Drake proposed the following simple equation:

DO YOU NEED LATEX? MAYBE NOT... If you are interested in just inserting simple mathematics or simple inline LaTeX, you do not need to use a full fledged LaTeX mode described in the rest of this document. You can write both math symbols, simple formulae, and even simple LaTeX using the equation button x²y in the toolbar. Read more here. BUT IF YOU WANT TO VENTURE INTO THE LATEX WORLD, KEEP READING... Authorea supports LaTeX, a powerful typesetting program that renders beautiful math notation. In order to insert LaTeX: click on the Insert button in the toolbar and then select LaTeX from the dropdown. A LaTeX label shows next to the LaTeX block in which you can write LaTeX notation. Here are some tips for writing LaTeX in Authorea: 1. Click anywhere outside of the LaTeX block to render it. 2. Hover on Preview to see a Preview of the rendered content. 3. Do not paste an entire LaTeX article! Instead import documents from your homepage. 4. Only type LaTeX content in a LaTeX block, i.e. everything you would write after . 5. Do not type preamble (e.g. documentclass), frontmatter, macros or figures. 6. To add macros (newcommands) and packages, click Settings → Edit Macros 7. Use the Insert Figure button to insert images (and data). 8. Use math mode for equations, e.g. $\mathcal L_{EM}=-\frac14F^{\mu\nu}F_{\mu\nu}$. 9. Try the citation tool (click cite) to find and add citations, or use \cite{}. 10. To insert more LaTeX blocks click Insert → LaTeX. 11. You can use sectioning commands like \section{},\subsection{},\subsubsection{} to add headings.[1] THERE ARE DIFFERENT WAYS TO PRESENT A MATHEMATICAL EXPRESSION IN LATEX — _INLINE_, AS AN _EQUATION_ OR _DISPLAYSTYLE_. Inline mathematical expressions Inline expressions occur in the middle of a sentence. To produce an inline expression, place the math expression between dollar signs ($). For example, typing $E=mc^2$ yields E = mc². Equations Equations are mathematical expressions that are given their own line and are centered on the page. These are usually used for important equations that deserve to be showcased on their own line or for large equations that cannot fit inline. To produce an inline expression, place the mathematical expression between the symbols \[! and \verb!\]. Typing \[x=}{2a}\] yields \[x=}{2a}.\] Displaystyle To get full-sized inline mathematical expressions use \displaystyle. Typing I want this $\displaystyle ^{\infty} {n}$, not this $^{\infty} {n}$. yields: I want this $\displaystyle ^{\infty}{n}$, not this $^{\infty}{n}.$ SYMBOLS (IN _MATH_ MODE) The basics -------------------------- -------------- --------------- _description_ _command_ _output_ addition + + subtraction - − plus or minus \pm ± multiplication (times) \times × multiplication (dot) \cdot ⋅ division symbol \div ÷ division (slash) / / infinity \infty ∞ dots 1,2,3,\ldots 1, 2, 3, … dots 1+2+3+\cdots 1 + 2 + 3 + ⋯ fraction {b} ${b}$ square root $$ nth root \sqrt[n]{x} $\sqrt[n]{x}$ exponentiation a^b ab subscript a_b ab absolute value |x| |x| natural log \ln(x) ln(x) logarithms b logab exponential function e^x=\exp(x) ex = exp(x) degree \deg(f) deg(f) circle plus \oplus ⊕ circle times \otimes ⊗ equal = = not equal \ne ≠ less than < < less than or equal to \le ≤ greater than or equal to \ge ≥ approximately equal to \approx ≈ -------------------------- -------------- --------------- [1] You can toggle heading numbering on/off from the article settings. This footnote is generated via \footnote{}

The peer review process is a pillar of modern research, verifying and validating the ever-increasing output of academia. While the academic community agrees that some process of review is necessary to ensure the quality of published research, not everybody agrees on the best approach. In particular, doubts have been cast on the current peer review process: most journals select and assign one anonymous referee (few journals assign two or more) who is in charge of reviewing the manuscript and recommending it for publication or rejection. The argument is that the current peer review system is becoming inadequate. Here’s an incomplete list of issues: - Research is increasingly collaborative, complex, and specialized. Thus, it is less likely that one or a few referees can have the necessary expertise (and time) to properly handle many modern articles. Simply put, THE AVERAGE NUMBER OF AUTHORS PER PAPER HAS BEEN STEADILY INCREASING IN THE LAST FEW DECADES, WHILE THE NUMBER OF REFEREES PER PAPER HAS NOT. - “Publication pressure” means there is a growing number of papers to referee. This need can not be easily matched since scholars, who need to constantly publish and engage in the “funding race”, HAVE LESS TIME TO BE DEDICATED TO COMMUNITY SERVICE (in a “single referee” system the review process is very time consuming). - Given the anonymous nature of peer reviewing manuscripts, RESEARCHERS WHO VOLUNTEER THEIR VALUABLE TIME AND KNOWLEDGE DON’T GET RECOGNITION for contributing. - Cases of peer-review scams, mostly from predatory open access publishers, have grown in number over recent years. A number of journals, exploiting the publication pressure climate, accept and publish articles with LITTLE OR NO PEER REVIEW. - Similarly, there are reports of fraud in which authors review their own or close friends’ manuscripts to give favorable reviews .

FABIO, WHEN DID YOU DECIDE TO GO WATCH AN ECLIPSE IN THE ARCTIC? I’ve been feeling this urge to visit the northernmost parts of Earth for a while now. My PhD in Stockholm gave me the opportunity to explore the Norwegian coastline and Lapland, but the Arctic was a different story. A sort of forbidden dream. Then last year I started a postdoc at Yale, in the research group led by John Wettlaufer, who’s an expert on sea ice and the Arctic. When I heard there was gonna be a total solar eclipse at Svalbard I knew I had to go. WHERE IS SVALBARD, EXACTLY? Svalbard is an archipelago situated about half way between continental Norway and the North Pole, and it is an outpost for research and arctic exploration. In Longyearbyen, a little city of about 2000 people, and Svalbard’s capital, there is the world’s northernmost institution for higher education and research: the University Center in Svalbard.

A recent article titled The spin rate of pre-collapse stellar cores: wave driven angular momentum transport in massive stars was written on Authorea and submitted to the Astrophysical Journal (ApJ) and to the arXiv as a pre-print. While waiting on peer review from the ApJ, the authors want to test Authorea as a platform for OPEN PEER-REVIEW. By going to the document’s page, you can comment on a section, figure, observation, sentence, or the whole piece. The authors and other commenters can respond and further the discussion. And it’s all out in the open, just how science was meant to be. But it doesn’t stop there. You can also view full-size, high-resolution versions of the paper’s figures, as well as easily follow links in the References at the bottom of the page. In the paper, show for the first time how internal gravity waves, excited in the turbulent layers of stars at least ten times larger than the Sun, can radically change their internal rotation rate. In particular, these waves – somewhat analogous to ocean waves – can determine how rapidly the stellar core spins around its axis when the star is about to die and become a supernova. The spin of a pre-supernova core is important because it deeply affects the stellar explosion and determines the rotation rate of the stellar remnant (neutron star or black hole).

Tens of thousands of innovators met in Austin, Texas last week to discuss emerging tech, science, and innovation. It was the Interactive portion of South by Southwest (SxSW). Authorea was there. Among many great events, the MIT Media Lab presented “SOLVE”, an initiative set to bring together the most gifted researchers and innovators to identify and tackle challenges where new thinking and emerging technologies have the potential to make the world a better place. SOLVE identified four main themes: Learn, Cure, Fuel, Make.

The core rotation rates of massive stars have a substantial impact on the nature of core collapse supernovae and their compact remnants. We demonstrate that internal gravity waves (IGW), excited via envelope convection during a red supergiant phase or during vigorous late time burning phases, can have a significant impact on the rotation rate of the pre-SN core. In typical (10 M⊙ ≲ M ≲ 20 M⊙) supernova progenitors, IGW may substantially spin down the core, leading to iron core rotation periods $P_{\rm min,Fe} \gtrsim 50 \, {\rm s}$. Angular momentum (AM) conservation during the supernova would entail minimum NS rotation periods of $P_{\rm min,NS} \gtrsim 3 \, {\rm ms}$. In most cases, the combined effects of magnetic torques and IGW AM transport likely lead to substantially longer rotation periods. However, the stochastic influx of AM delivered by IGW during shell burning phases inevitably spin up a slowly rotating stellar core, leading to a maximum possible core rotation period. We estimate maximum iron core rotation periods of $P_{\rm max,Fe} \lesssim 10^4 \, {\rm s}$ in typical core collapse supernova progenitors, and a corresponding spin period of $P_{\rm max, NS} \lesssim 400 \, {\rm ms}$ for newborn neutron stars. This is comparable to the typical birth spin periods of most radio pulsars. Stochastic spin-up via IGW during shell O/Si burning may thus determine the initial rotation rate of most neutron stars. For a given progenitor, this theory predicts a Maxwellian distribution in pre-collapse core rotation frequency that is uncorrelated with the spin of the overlying envelope.

WORDS ARE IMPORTANT. THEY CONVEY OUR THOUGHTS, OUR IDEAS, OUR INTUITIONS. PASSION, LOVE, DISCOVERY, THEY ALL MATERIALIZE FROM WORDS EMERGING FROM THE INNER WORKINGS OF OUR MINDS. AND WHEN WE WRITE, WHEN WE FILL WITH WORDS THE EMPTY CANVAS IN FRONT OF US, SOMETIMES THOSE INTUITIONS, THOSE FEELINGS, THOSE BEAUTIFUL BUNDLES OF THOUGHTS, THEY SUDDENLY BECOME CLEARER. ALL OF THE SUDDEN WE REALLY UNDERSTAND. THE WRITERS. THE READERS. THE LOVERS. TO LOVE, PASSION, DISCOVERY. TO WORDS. Happy Writing, - Matteo and The Authorea Team

The core rotation rates of massive stars have a substantial impact on the nature of core collapse supernovae and their compact remnants. We demonstrate that internal gravity waves (IGW), excited via envelope convection during a red supergiant phase or during vigorous late time burning phases, can have a significant impact on the rotation rate of the pre-SN core. In typical (10 M⊙ ≲ M ≲ 20 M⊙) supernova progenitors, IGW may substantially spin down the core, leading to iron core rotation periods $(P_{\rm min,Fe} \gtrsim 50 \, {\rm s})$. Angular momentum (AM) conservation during the supernova would entail minimum NS rotation periods of $P_{\rm min,NS} \gtrsim 3 \, {\rm ms}$. In most cases, the combined effects of magnetic torques and IGW AM transport likely lead to substantially longer rotation periods. However, stochastic influxes of AM delivered by IGW during shell burning phases also entail a maximum core rotation period. We estimate maximum iron core rotation periods of $P_{\rm max,Fe} \lesssim 10^4 \, {\rm s}$ in typical core collapse supernova progenitors, and a corresponding spin period of $P_{\rm max, NS} \lesssim 400 \, {\rm ms}$ for newborn neutron stars. This is comparable to the typical birth spin periods of most radio pulsars. Stochastic spin-up via IGW during shell O/Si burning may thus determine the initial rotation rate of most ordinary pulsars. For a given progenitor, this theory predicts a Maxwellian distribution in pre-collapse core rotation frequency that is uncorrelated with the spin of the overlying envelope.

MLT These notes are mostly inspired from reading Cox & Giuli (“Principles of stellar structure”); some insights are from A.Maeder (“Physics, formation and evolution of rotating stars”) and Kippenhahn & Weigert (“Stellar Structure and Evolution”) Pressure Scale Height In hydrostatic equilibrium we can define the total pressure scale height, $\hp$, as -{\D r} \equiv {\hp} = {\p} where $\p$ is the total pressure ($ + $). The pressure scale height is a measure of the distance over which the pressure changes by an appreciable fraction of itself.

A revolution has occurred in the last two decades in the world of astrophysics. It all started in the mid ’90s with the first discovery of new worlds around other stars. The term “Extrasolar planet” (or Exoplanet) became widely used to identify planets orbiting a star other than the Sun. A planet is a celestial body massive enough to be bounded by its self gravity (unlike a rock or an asteroid, that are kept together by electromagnetic forces), but not massive enough to produce energy through nuclear fusion (as stars do). Planetary scientists have confirmed the existence of more than 1500 exoplanets and have identified a few thousand exoplanet candidates that require more investigation before they can join the planet club (see exoplanets.org for the most recent figures). The most remarkable discoveries came only in the last couple of years thanks to the Kepler space telescope. This amazing instrument has been patiently looking for the extremely tiny dimming induced by the passage of a planet in front of its host star. The wealth of data provided by Kepler has revealed an astonishing fact: “When you wish upon a star, you are wishing upon a star with planets” (W. Borucki). There is on average ONE PLANET ORBITING EVERY STAR IN THE UNIVERSE . Just in our Galaxy this means we have 100 billion planets. Since we have about 100 billion galaxies in the Universe, there are about 10,000,000,000,000,000,000,000 = 10²² planets out there.

In 1937, just one year before suddenly disappearing under mysterious circumstances, a brilliant italian physicist named ETTORE MAJORANA predicted the existence of a very peculiar particle. Having the exciting property of being its own antiparticle (that is it simultaneosly behaves as matter and anti-matter) the elusive “MAJORANA PARTICLE” has been finally observed by a group of scientists at Princeton University . To achieve the important result they used a two-story-tall microscope to observe the end of a superconducting wire.

RISE AND FALL OF THE BIGGEST DISCOVERY OF THE CENTURY HIGHLIGHTS THE IMPORTANCE OF OPEN, COLLABORATIVE SCIENCE. On 17 March 2014 BICEP2, a South Pole based experiment aimed at studying the very first moments of the universe, made a sensational announcement. They claimed to have detected for the first time the signature of an extremely rapid expansion of space that occurred right after the universe’s birth. This expansion, also called inflation, is believed to be responsible for the existence of large-scale structures like clusters of galaxies, as well as to explain why the properties of the universe appear to be the same for all observers. If confirmed, the existence of inflation would represent the first evidence of a fundamental connection between gravity (general relativity) and quantum physics.

THEORY OF EVOLUTION AND DEATH OF MASSIVE STARS Overview of the material that will be covered at the “Look & Listen” School 2014 Abstract We will first cover some basic principles of stellar evolution, with a particular emphasis on the physics of massive stars. Then we will focus on the phenomena that are currently believed to prominently influence the life of massive stars and determine the conditions at the pre-SN stage. Informed by the most recent observational results, we will also focus on some unsolved problems in stellar physics and how they could impact the death of massive stars and their stellar remnants. Schedule 1. Tuesday 14 Jan - Principles of stellar evolution (20+10) - Massive Stars evolution: Main Sequence and He-Burning (20+10) - Massive Stars evolution: Late evolutionary stages (20+10) 2. Thursday 16 Jan - Stellar Rotation (20+10) - Stellar Rotation and Magnetic Fields (20+10) - Mass loss (20+10) 3. Friday 17 Jan - Massive Binary Stars (20+10) - Very Massive Stars (20+10) - Progenitors of NS/BH, SNe, PISNe, GRBs (20+10)

JAVASCRIPT, D3.JS, AND D3PO.JS Javascipt offers many ways to create data-driven graphics. A popular solution is D3.js, a JavaScript library to create and control web-based dynamic and interactive graphical forms. A gallery of some beautiful d3.js plots can be found here. Authorea now supports most Javascript-based data visualization solutions. The example below - Figure [fig:1] - is a plot generated using D3po.js which is a javascript extension of d3.js. D3po allows anyone with no special data visualization skills, to make an interactive, publication-quality figure that has staged builds and linked brushing through scatter plots. What’s even cooler is that the plot below is based on actual data (astrophysics data, yay!). The figure describes how metallicity affects color in cool stars. It is based on work of graduate student Elizabeth Newton and others . TRY CLICKING AND DRAGGING IN THE SCATTER PLOTS to understand the power of linked brushing in published figures. You should know that THIS ENTIRE VISUALIZATION IS RUNNING WITHIN AUTHOREA. The Javascript, HTML, CSS and ALL THE DATA associated with this image are all part of this blog post. They are individual files which can be found by clicking on the folder icon on the top left corner of this page.

Asteroseismology of 1.0 − 2.0M⊙ red giants by the _Kepler_ satellite has enabled the first definitive measurements of interior rotation in both first ascent red giant branch (RGB) stars and those on the Helium burning clump. The inferred rotation rates are 10 − 30 days for the ≈0.2M⊙ He degenerate cores on the RGB and 30 − 100 days for the He burning core in a clump star. Using the MESA code we calculate state-of-the-art stellar evolution models of low mass rotating stars from the zero-age main sequence to the cooling white dwarf (WD) stage. We include transport of angular momentum due to rotationally induced instabilities and circulations, as well as magnetic fields in radiative zones (generated by the Tayler-Spruit dynamo). We find that all models fail to predict core rotation as slow as observed on the RGB and during core He burning, implying that an unmodeled angular momentum transport process must be operating on the early RGB of low mass stars. Later evolution of the star from the He burning clump to the cooling WD phase appears to be at nearly constant core angular momentum. We also incorporate the adiabatic pulsation code, ADIPLS, to explicitly highlight this shortfall when applied to a specific _Kepler_ asteroseismic target, KIC8366239.

The search for extrasolar planets (EXOPLANETS) is one of the most rapidly expanding fields in astrophysics. Thanks to recent space-based efforts the number of detected planets in extrasolar stellar systems has increased dramatically, and more than 900 objects have been identified as of today, see e.g. http://exoplanet.eu/catalog/. With candidates identified in the so-called habitable zone (HZ)[1] the question of extraterrestrial life becomes very actual. Here we discuss ideas that could lead to infer the presence (or the past existence) of an extraterrestrial civilization by the detection of artifacts in orbit around the host planet. [1] The theoretical band around a star where a planet could orbit and host liquid water

Thermohaline mixing has recently been proposed to occur in low-mass red giants, with large consequence for the chemical yields of low-mass stars. We investigate the role of thermohaline mixing during the evolution of stars between 1$\mso$ and 3$\mso$, in comparison with other mixing processes acting in these stars. We use a stellar evolution code which includes rotational mixing, internal magnetic fields and thermohaline mixing. We confirm that during the red giant stage, thermohaline mixing has the potential to decrease the abundance of ³He, which is produced earlier on the main sequence. In our models we find that this process is working on the RGB only in stars with initial mass $ \le 1.5\mso$. Moreover we report that thermohaline mixing is also present during core He-burning and beyond, and has the potential to change the surface abundances of AGB stars. While we find rotational and magnetic mixing to be negligible compared to the thermohaline mixing in the relevant layers, the interaction of thermohaline motions with the differential rotation may be essential to establish the timescale of thermohaline mixing in red giants. To explain the surface abundances observed at the bump in the luminosity function, the speed of the mixing process needs to be more than two orders of magnitude higher than in our models. However it is not clear if thermohaline mixing is the only physical process responsible for these surface-abundance anomalies. Therefore it is not possible at this stage to calibrate the efficiency of thermohaline mixing against the observations.