A team of astronomers uncovered a puzzling situation when they examined X-ray data from DEM L238 and DEM L249, the remnants of two supernovas in a nearby galaxy. On the one hand, the unusually high concentration of iron atoms implied that the remnants are the products of thermonuclear explosions of white dwarf stars, a well-known type of supernova known as ‘Type Ia’. On the other hand, the hot gas in the remnants was much denser and brighter in X-rays than typical Type Ia remnants.
A white dwarf, the dense final stage in the evolution of a sun-like star, is a very stable object and will not explode on its own. However, if a white dwarf has a close companion star it can grow beyond a critical mass by pulling gas off the companion and explode.
Computer simulations of Type Ia supernova remnants showed that the most likely explanation for the X-ray data is that the white dwarfs exploded into very dense environments. This suggests that the stars which evolved into these white dwarfs were more massive than usual, because heavier stars are known to expel more gas into their surroundings.
"We know that the more massive a star is, the shorter its lifetime," said Kazimierz Borkowski of North Carolina State University, Raleigh, USA. "If such a star could also begin to pull matter from its companion at an early stage, then this star would have a much shorter fuse and explode in only about 100 million years - much less than other Type Ia supernovas."
Other teams have independently found evidence for prompt Type Ia explosions using optical observations, but at much greater distances where the environment of the stellar explosion cannot be probed. The X-ray data of DEM L238 and DEM L249 represent nearby examples of prompt Type Ia supernovas.
"We still need to know more about the details of these explosions since they are such an important tool for studying cosmology," said Stephen Reynolds also of North Carolina State University. "So, it's exciting to discover we have some really nearby examples, astronomically speaking, of this different class of explosion."
The luminosity of Type Ia explosions is thought to be very consistent from star to star, and astronomers have used observations of Type Ia supernovas in optical light as cosmic mile markers to study the accelerating expansion of the cosmos caused by dark energy.
If Type Ia supernovas can occur so quickly, they can exist much earlier in the Universe's history than generally believed, allowing them to probe the expansion at these epochs. Another possibility is that the prompt Type Ia’s may also differ in other properties. If so, the assumption that Type Ia’s are standard candles may be compromised, complicating attempts to study dark energy.
"We weren't around to see these stars before they exploded," said Sean Hendrick of Millersville University, Pennsylvania,USA, "but these X-ray clues tell us that something unusual happened in the case of these two."
After finding this evidence for prompt Type Ia explosions in the Large Magellanic Cloud, a nearby galaxy, the researchers are looking at other supernova remnants within the Milky Way to see if they might be examples of this potential new class. For example, the famous supernova observed by Johannes Kepler in 1604 might have been a prompt Type Ia supernova.
Norbert Schartel | alfa
Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)
Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences