Posts tagged astronomy
Posts tagged astronomy
Ji-Lin Zhou, Ji-Wei Xie, Hui-Gen Liu, Hui Zhang and Yi-Sui Sun
Department of Astronomy and Key Laboratory of Modern Astronomy and Astrophysics in Ministry
of Education, Nanjing University, Nanjing 210093, China;
Received 2012 July 9; accepted 2012 July 17
With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we summarize the major statistical results that have been revealed mainly by radial velocity and transiting observations, and try to interpret them within the scope of the classical core-accretion scenario of planet formation, especially in the formation of different orbital architectures for planetary systems around main sequence stars. Based on the different possible formation routes for different planet systems, we tentatively classify them into three major catalogs: hot Jupiter systems, standard systems and distant giant planet systems. The standard systems can be further categorized into three sub-types under different circumstances: solar-like systems, hot Super-Earth systems, and sub- giant planet systems. We also review the theory of planet detection and formation in binary systems as well as planets in star clusters.
I’m reading this paper and if anyone’s interested in the formation of different planetary systems, I highly suggest reading this. It’s so interesting.
NASA’s SDO Observes Fast-Growing Sunspot
The bottom two black spots on the sun, known as sunspots, appeared quickly over the course of Feb. 19-20, 2013. These two sunspots are part of the same system and are over six Earths across. This image combines images from two instruments on NASA’s Solar Dynamics Observatory (SDO): the Helioseismic and Magnetic Imager (HMI), which takes pictures in visible light that show sunspots and the Advanced Imaging Assembly (AIA), which took an image in the 304 Angstrom wavelength showing the lower atmosphere of the sun, which is colorized in red. Credit: NASA/SDO/AIA/HMI/Goddard Space Flight Center
Seriously, I am obsessed with finding this sweater.
THANK YOU I AM NOT THE ONLY ONE.
Structure and Evolution of Galaxies
As much as we know about galaxies, the evolution of galaxies is one of the mysteries of the Universe. By looking far out into space and equivalently, far back into time, astronomers can look at the oldest galaxies and make comparisons with modern-day galaxies to get a sense of how they’re evolving. To really understand galaxy evolution, though, one must understand the details of the structure of galaxies; therein lies many wondrous secrets of galaxies. We will focus on spiral galaxies:
The Structure of Spiral Galaxies
Most spiral galaxies have similar features, the most significant of which include a dark matter halo, the galactic disc, spiral arms, a central bulge (most containing a bar-like structure), and a stellar halo.
The dark matter halo is believed to be the main structural component of the Milky Way galaxy whose functional purpose is primarily to hold together the galaxy; without it, the galaxy would not be gravitationally bound. The dark matter halo is situated well beyond the visible galactic disc which is detected using observations like rotation curves of galaxies. Current observations suggest that dark matter accounts for roughly 95% of the Milky Way’s mass, while the other 5% is accounted for with normal, baryonic matter. It is currently believed that dark matter played a significant role in the evolution of galaxies, initiating clumps of matter in the early Universe which eventually lead to structures like galaxies.
The galactic disc is the location of most of the interstellar medium (ISM, composed of gas and dust) and also contains a substantial amount of stars which orbit in roughly circular orbits confined to the galactic plane; it consists of most of the visible matter in the galaxy. The Sun is located about 8.5kpc (kiloparsecs) from the galactic center in the galactic disc. The spiral arms within the galactic disc are the main sites of star formation; the blue spiral arms are indicators of young, hot stars. Within the galactic disc is where most cosmic recycling occurs and as a result, the ISM has a higher metallicity than primordial gas. The metallicity-age relation is important for understanding galaxy evolution. Most open clusters are found in the galactic disc, but some globular clusters (roughly one third) are found here, as well. Open clusters are very young because they are loosely bound and are easily disrupted. Open clusters have high metallicities because they are formed from more recently formed ISM which has had time to become enriched with metals. In contrast, globular clusters are very old as they are strongly gravitationally bound. Since globular clusters consist of the oldest stars in the galaxy, the metallicity-age relation suggests that they should have very low metallicities but those found in the galactic disc have unusually high metallicities; this suggests that cosmic recycling enriches the contents of the globular clusters.
The stellar halo extends further than the galactic disc itself and is roughly spherical in shape. Here lie roughly two thirds of the galaxy’s globular clusters. The globular clusters found here, as expected, have very low metallicities because they are young and do not get contaminated by the cosmic recycling that takes place in the galactic disc. The stellar halo’s star formation has long since ceased; there is very little ISM left in the stellar halo. The stars within the stellar halo have largely elliptical and highly irregular orbital motions which are not confined to the galactic plane.
What Does Any of This Tell Us About Galaxy Evolution?
Without the dark matter halo, our galaxy wouldn’t be gravitationally bound the way it is today. With this, along with the fact that dark matter consists of 95% of the galaxy’s mass, it is suggested that dark matter played a key role in the initial formation of galaxies. The spiral arms of the galaxy suggest that the galaxy is rotating, which is well supported by observations. Older stars contained in the stellar halo having irregular, elliptical orbits and younger stars confined in the galactic disc having regular, circularized orbits suggests that the galaxy started out in a disordered state which over time settled down to a more orderly state; the galaxy originated as a large gas cloud that eventually collapsed and through the conservation of angular momentum, became a flat, rotating disc. The fact that globular clusters within the galactic disc have unusually high metallicities suggest that cosmic recycling is the origin; as time progresses, high mass stars explode and contaminate the surrounding ISM to further enrich future stars’ chemical composition. Furthermore, globular clusters which were once believed to originate from the Milky Way are now believed to having been captured by the Sagittarius Dwarf galaxy, which suggests that even though the galactic halo is the oldest component of the galaxy, it is still a dynamic part of the Milky Way. Currently, the Milky Way is in a collision course with its neighbour, the Andromeda galaxy. In about 4 billion years, the two spiral galaxies will collide to form what astronomers like to call the Milkomeda galaxy.
A couple of days ago I uploaded the Io, Ganymede transit of Jupiter. Unfortunately, my original video was missing a few frames of the transit, but a fellow astronomer was kind enough to send me the missing images, so here is the finished video of the complete Io, Ganymede transit.
I just need this on my blog.
(Not including Earth)
Our of curiosity, I made a survey for this. Mostly because I’m interested in what people consider “interesting” when it comes to these things, but also whether or not that impacts how much you like it. But please do not answer the questions unless you have an actual answer for both of them. In other words, don’t just choose one randomly without giving it any thought.
The survey can be found here. I’ll post the results a week from today, on January 13th.
Oh, the ignominy of a collapsing protostellar gas cloud which must undergo nuclear fusion to support its gravitational attraction.
I have no idea what’s going on right now.
Relations I will need for my astronomy midterm tomorrow. Beautiful.
The Light of Stars
What’s moving? Time lapse videos of the sky can be quite spectacular when they last long enough for stars, planets, aurora, and clouds to appear to move in just a few seconds. Pictured above, however, astrovideographer Daniel López not only treats us to several inspiring time lapse videos of the night sky, but shows us how he used sliders and motorized cranes to move the imaging cameras themselves, creating a thrilling three-dimensional sense of depth. The video sequences were taken from Tenerife on the Canary Islands of Spain over the past two months, and show scenes including sunset shadows approaching Observatorio del Teide, the Milky Way shifting as the sky rotates, bright planets Venus and trailing Jupiter setting, a reddened Moon rising through differing layers of atmospheric refraction, the MAGIC gamma-ray telescopes slewing to observe a new source, and unusual foreground objects including conic Echium wildpretii plants, unusual rock formations, and a spider moving about its web. The video concludes by showing the Belt of Venus descending on Mt. Teide as the morning sun rises.
FreeMat Rapid engineering and scientific prototyping and data processing
K3DSurf Visualize and manipulate multidimensional surfaces
Octave High-level language, primarily intended for numerical computations
Scilab Numerical computational package
Computer Algebra systems
Axiom For research and development of mathematical algorithms
Mathomatic Fast and easy-to-use console mode Computer Algebra System
Maxima System for the manipulation of symbolic and numerical expressions
PARI/GP Designed for fast computations in number theory
Sage Integrates an included distribution of specialized mathematics software
PSPP Free replacement of the proprietary program, SPSS
R Environment for statistical computing and graphics
Gnuplot Command-driven interactive function plotting program
QtiPlot Fully fledged plotting software
EMBOSS The European Molecular Biology Open Software Suite
GROMACS Molecular dynamics simulator, with building and analysis tools
VMD Displays, animates, and analyzes large biomolecular systems
Avogadro Advanced molecular editor
Gabedit Graphical user interface to computational chemistry packages
GAMESS General ab initio quantum chemistry package
MOSCITO Performs molecular dynamics simulations of rigid and/or flexible molecules
MPQC Computes the properties of molecules, ab initio
Open Babel Converts and manipulates chemical data files
PyMOL OpenGL molecular graphics system written in Python
CompHEP Automatic computations in High Energy Physics
Gerris Flow Solver Tool for generic numerical simulations of flows
Octopus Real-space, real-time implementation of TDDFT
OpenFOAM Facilitates the numerical solution of partial differential equations
ROOT Solves the data analysis challenges of high-energy physics
Celestia Real-time space simulation
KStars Desktop planetarium for KDE
Skychart Prepare different sky maps for a particular observation
Stellarium A virtual planetarium
Electronic & Engineering
Elmer Multiphysical simulation software
Qucs Integrated circuit simulator
Geographic Information Systems
GRASS Geographic Resources Analysis Support System
Quantum GIS Create, visualise, query and analyse geospatial data
SAGA Analysis of spatial data
uDig Spatial data viewer/editor
gretl Regression, Econometric and Time-Series Library
Kile User-friendly LaTeX source editor and TeX shell and KDE
LyX Advanced open source document processor
TeXmacs WYSIWYW scientific word processor