MessageToEagle.com - Type Ia supernovae are violent stellar explosions but astronomers know very little about the
stars they come from and how the explosions happen.
Observations of their brightness are used to measure the expansion of the universe and have shown scientists that the
universe is expanding at an accelerating rate.
Type Ia supernovae are believed to be thermonuclear explosions of a white dwarf star that’s part of a binary system--two
stars that are physically close together and orbit around a common center of mass.
White dwarf stars are one of the densest forms of matter, second only to neutron stars and black holes. Just a teaspoon of
matter from a white dwarf would weigh five tons.
Because white dwarf stars are so dense, their gravity is particularly intense.
The white dwarf will begin to pull material off its companion star, adding that matter to itself.
When the white dwarf reaches 1.4 solar masses, or about 40 percent more massive than our Sun, a nuclear chain reaction occurs,
causing the white dwarf to explode. The resulting light is 5 billion times brighter than the Sun.
Because the chain reaction always happens in the same way, and at the same mass, the brightness of these Type Ia supernovae
are also always the same. The explosion point is known as the Chandrasekhar limit, after Subrahmanyan Chandrasekhar,
the astronomer who discovered it.
There are two different possibilities for how Type Ia supernovae are created from this type of binary system.
Multiwavelength X-ray / infrared image of SN 1572 or Tycho's Nova, the remnant of a Type Ia supernova (NASA/CXC/JPL-Caltech/Calar Alto O. Krause et al.)
In the so-called double-degenerate model, the orbit between two white dwarf stars gradually shrinks until the lighter star
gets so close to its companion that it is ripped apart by tidal forces.
Some of the lighter star’s matter is then absorbed into the primary white dwarf, causing an explosion.
In the competing single-degenerate model, the white dwarf slowly accretes mass from an ordinary, non-white dwarf star,
until it reaches an ignition point.
"Previous studies have produced conflicting results. The conflict disappears if both types of explosion are happening,”
explained lead author Ryan Foley of the Harvard-Smithsonian Center for Astrophysics.
Merging white dwarfs appear to cause Type Ia supernovae in elliptical galaxies. Sun-like stars eventually evolve
into white dwarfs; one can imagine a binary star system with two Sun-like stars one day leaving behind a pair
of white dwarfs that over millions of years slowly spiral towards one another before merging and exploding.
Image: NASA/CXC/M Weiss.
The research team studied 23 Type Ia supernovae to look for signatures of gas around the supernovae, which should be
present only in single-degenerate systems.
They found that the more powerful explosions tended to come from “gassy” systems, or systems with outflows of gas.
However, only a fraction of supernovae show evidence for outflows--the remainder likely come from double-degenerate systems.
This finding has important implications for how astronomers use supernovae to measure the universe’s expansion.
“To maximize the accuracy of our measurements we may have to separate the two kinds of Type Ia supernovae,” Simon said.
“This study gives us one potential way to tell them apart.”
The Nobel Prize in Physics was awarded December 10, 2011, to three astronomers for their "discovery of the accelerating
expansion of the Universe through observations of distant supernovae.”
New research from a team led by Harvard University and including Carnegie’s Josh Simon, Chris Burns, Nidia Morrell,
and Mark Phillips examined 23 Type Ia supernovae and helped identify the formation process for at least some of them.
Their work will be published in The Astrophysical Journal and is available online.
@ MessageToEagle.com via Carnegie Institution of Washington
Development of Earth's Life Strongly Influenced
By Exploding Massive Stars Near The Solar System
The explosion of massive stars – supernovae – near the Solar System has strongly influenced the development of life,
according to a research conducted by a Danish physicist Prof. Henrik Svensmark of the Technical University of Denmark (DTU).
When the most massive stars exhaust their available fuel and reach the end of their lives, they explode as supernovae,
tremendously powerful explosions that are briefly brighter than an entire galaxy of normal stars.
Wonderful Mobile Astronomy Apps For All Stargazers!
It doesn't matter whether you are a beginner or an experienced backyard astronomer.
It's never too late to become interested in astronomy and these superb applications can help you in your stargazing pursuits.
We have put together a selection of some wonderful applications for you mobile or ipad.
Black Hole In Scorpius Seen Firing Fast Cosmic Bullets
Located about 28,000 light-years from Earth in the constellation Scorpius, there is a black hole named H1742-322.
Racing outward at about one-quarter the speed of light, "bullets" of ionized gas are thought to arise from a region located
just outside the black hole's event horizon, the point beyond which nothing can escape.
Countless Earthlike Alien Worlds
That Will Never Be Like Earth
There could be billions of Earthlike planets in the Universe but a great majority of them may have a totally different internal and atmospheric structure.
Building planets in chemically non-solar environments (which are very common in the Universe) may lead to the formation of strange worlds, very different from the Earth!
"Bloatars" - Abnormal Stars Eating Planets
These objects are a new class of stars with luminosities of much more massive stars.
Astronomers say that the strange stars are too cool to be ordinary stars, with analysis of their
infrared light emissions indicating surface temperatures between 1700 and 2200 Kelvin.
Latest Spectacular Solar Flare Will Hit STEREO-B Spacecraft, Spitzer And Curiosity
The Sun continues to show its more violent side.
A spectacular solar flare erupted from the Sun's northeastern limb yesterday, sending an beautiful arcing jet of super-heated plasma blasting off into space.
The explosion, captured by Nasa's Solar Dynamics Observatory at about 5.45pm yesterday evening, was one of the most beautiful seen in years.
Something New Spotted On The Sun
One day in the fall of 2011, Neil Sheeley, a solar scientist at the Naval Research Laboratory in Washington, D.C., did what he always does –
look through the daily images of the sun from NASA's Solar Dynamics Observatory (SDO).
But on this day he saw something he'd never noticed before: a pattern of cells with bright centers and dark boundaries occurring in the sun's atmosphere, the corona...
Hidden Misshapen Celestial "Wonder"
It is one of the brightest and strangest objects in the Milky Way - the corpse of a star that exploded around 1000 years ago.
Only a handful of such young supernova remnants are known.
The object named G350.1-0.3 is also incredibly small (only eight light years across) and young in astronomical terms.
Mercury Surprises Scientists
On March 17, MESSENGER (MErcury Surface, Space Environment, GEochemistry, and Ranging) completed its one-year primary mission, orbiting Mercury, capturing nearly 100,000 images, and recording data
that reveals new information about the planet's core, topography, and the mysterious radar bright material in the permanently shadowed areas near the poles.
Living Earth Simulator - Supercomputer Predicting The Future
In Douglas Adams book the Hitchhikers Guide to the Galaxy we encounter a machine called Deep Thought. It is the most powerful computer ever built. Deep Thought is capable of answering questions
concerning life, the Universe, and simply everything. Now scientists are planning to create a similar machine. It is called the Living Earth Simulator (LES).