Comments, criticism (constructive only), suggestions etc contact : cosmology@AbergavennyAS.org.uk
News Items discussed at the December 12th, 2016, meeting
Desperately Seeking….11 things we are sure exist but have never seen. – Black Holes
Date: 19th March, 2016 : Source: New Scientist, pp 30-37
Don’t know if the news this week can be called “seeing” a black hole but see what you think.
Spinning black hole swallowing star explains superluminous event
ESO telescopes help reinterpret brilliant explosion
Date: December 12, 2016 : Source: ESO
An extraordinarily brilliant point of light seen in a distant galaxy, and dubbed ASASSN15lh, was thought to be the brightest supernova ever seen. But new observations from several observatories, including ESO, have now cast doubt on this classification. Instead, a group of astronomers propose that the source was an even more extreme and very rare event a rapidly spinning black hole ripping apart a passing star that came too close. Link
Or, as the BBC (NI) put it
Black hole ‘swallowed star’, say Queen’s astronomers
Belfast-based astronomers have helped to discover a very rare celestial event – a star being “swallowed” after it passed too close to a black hole…………
(Prof Smartt) said the light “puzzled us for months” but based on their telescopic observations, the QUB team proposed a new explanation for the object in a galaxy far, far away.
It believes the sun-like star wandered too close to the black hole and was “ripped apart”, a phenomenon known in astronomy as a “tidal disruption event”.
In the process, the star was “spaghettified and some of the material was converted into huge amounts of radiated light,” said a QUB statement.
“This gave the event the appearance of a very bright supernova explosion, even though the star would not have become a supernova on its own as it did not have enough mass.” Link
New evidence on the formation of the solar system
Date: December 2, 2016 : Source: Monash University
International research is using new computer models and evidence from meteorites to show that a low-mass supernova triggered the formation of our solar system.
A question was asked as to how small a star involved in a Low Mass Supernova is. If you want to read the paper the link is below.
Evidence from stable isotopes and 10Be for solar system formation triggered by a low-mass supernova. http://www.nature.com/articles/ncomms13639
By investigating isotope abundance they showed that the problems of abundances in our sun created by the assumption that a large supernova (>15 Solar Masses) triggered collapse of the gas and dust cloud are removed if <12 solar mass core collapse super nova are modelled instead.
Second-generation stars identified, giving clues about their predecessors
Date: December 6, 2016 : Source: University of Notre Dame
Astronomers have identified what they believe to be the 2nd generation of stars, shedding light on the nature of the universe’s first stars.
Couple of quotes from the ScienceDaily article:-
“The CEMPno stars we see today, at least many of them, were born shortly after the Big Bang, 13.5 billion years ago, out of almost completely unpolluted material,” Yoon says. “These stars, located in the halo system of our galaxy, are true second generation stars born out of the nucleosynthesis products of the very first stars.”
Beers says it’s unlikely that any of the universe’s first stars still exist, but much can be learned about them from detailed studies of the next generation of stars.
A question was also asked if we can see the stars that were investigated. One star, from a companion paper to this one,
(Observational Constraints on First-Star Nucleosynthesis. II. Spectroscopy of an Ultra Metal-Poor CEMPno Star)
was “HE 0020-1741” or “BPS CS 30324-0063” with a magnitude of 12.89
Another example is BPS CS22892-0052 (Sneden’s Star), an old population II star located at a distance of 4.7 kpc in the galactic halo. It belongs to a class of ultra-metal-poor stars (Metallicity [Fe/H]=-3.1) with a magnitude of 13.99
News Items discussed at the March 7th, 2016, Cosmology Group meeting
- Gravitational Waves detected : Advanced Laser Interferometer Gravitational wave Observatory (aLIGO)
Date February 11th, 2016; Source Physical Review Letters, 116, 061102; Links : aLIGO/MIT : Institute of PhysicsOn the 8th February New Scientist reported that “Latest rumour of gravitational waves is probably true this time”3 days later, on the 11th Feb a paper entitled “Observation of Gravitational Waves from a Binary Black Hole Merger” was published by the members of the LIGO Scientific Collaboration and Virgo Collaboration.
The waves were produced from the collision of two black holes of 36 and 29 solar masses, respectively, which merged to form a spinning, 62 solar mass black hole, some 1.3 billion lightyears (410 mpc) away in an event dubbed GW150914A question was asked at our meeting about signal times and frequencies, the diagram, below, gives more information.
- More on Gravitational Waves – how else to look : Pulsar web could detect low frequency gravitational waves
Date February 24th, 2016; Source NASA; Link : NASA : NANOGravGravitational waves span a wide range of frequencies that require different technologies to detect.A new study from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has shown that low frequency gravitational waves could soon be detectable by existing radio telescopes.
- Discovery of a fast radio burst reveals ‘missing matter’ in the universe
Date February 24th, 2016; Source Max Planck Institute for Radio Astronomy; Links : Science Daily : Subaru TelescopeAn international research team used a combination of radio and optical telescopes to identify the precise location of a fast radio burst (FRB) in a distant galaxy, allowing them to conduct a unique census of the universe’s matter content. Their result confirms current cosmological models of the distribution of matter in the universe.
- Black holes banish matter into cosmic voids
Date February 24th, 2016; Source Royal Astronomical Society (RAS); Links : Science Daily : RAS
We live in a universe dominated by unseen matter, and on the largest scales, galaxies and everything they contain are concentrated into filaments that stretch around the edge of enormous voids.
Thought to be almost empty until now, a group of astronomers based in Austria, Germany and the US now believe these dark holes could contain as much as 20% of the ‘normal’ matter in the cosmos and that galaxies make up only 1/500th of the volume of the universe.
- Astronomer detected a new source of intense gamma-radiation in the sky
Date February 17th,2016; Source Lomonosov Moscow State University; Links : Science Daily : RASAnalyzing the data collected by the Fermi Gamma-ray Space Telescope Maxim Pshirkov (The Sternberg Astronomical Institute, MSU) discovered a new source that confirmed the fact that binary systems with strong colliding stellar winds comprise a separate new population of high-energy gamma-ray sources.
- Lasers might push spacecraft all the way to Mars in just 3 days
Date February 24th, 2016; Source com; Links : UC Santa Barbara : zmescience
This could be possible using a ‘photonic propulsion’ system, says NASA scientist Philip Lubin.
A massive laser based on Earth would fire bursts of photons into the ‘sail’ of the spacecraft and accelerated it up to 26% the speed of light, which is unheard of in space flight. But that’s only for a tiny object with a 1 meter solar sail. Larger, more practical crafts, would be accelerated to between 1-3% the speed of light, which is still fantastic.
Lubin and colleagues have now received a proof-of-concept grant from NASA to assess whether or not a photonic propulsion system for long distance space applications is viable
Some extra items on the GW discovery that were not discussed but caught my attention:-
Comment: Gravitational waves: Numbers don’t do them justice
Date 12th February, 2016; Source BBC; Link : BBC news
David Reitze, executive director of the Laser Interferometer Gravitational Wave Observatories (LIGO), described it thus: “Take something about 150km in diameter, and pack 30 times the mass of the Sun into that, and then accelerate it to half the speed of light. Now, take another thing that’s 30 times the mass of the Sun, and accelerate that to half the speed of light. And then collide [the two objects] together. That’s what we saw here. It’s mind boggling.”
In that moment of union, the holes radiate pure energy in the form of gravitational waves, and lose mass equivalent to three times that of our Sun. Energy equals mass times the speed of light, squared (E=mc2). Everyone knows the equation; this is it in action.
New insights emerge from LIGO’s gravitational wave data
Date Feb 15, 2016; Link : Institute of Physics
Researchers from the LIGO collaboration who last week announced they had detected the first ever gravitational waves – spewed out from two merging black holes – have also picked up a second possible gravitational wave event. Although the signal from “LVT151012″ is much weaker than the confirmed “GW150914” event, the LIGO team says it most likely has an astrophysical source and arose from two coalescing black holes. The researchers have in addition spotted “several even less significant events in the data, most likely just due to some disturbance at the detectors”, which they are now analysing to see if any are from gravitational waves. Their conclusions, expected over the course of this year, will see the new era of gravitational wave astronomy finally start.
Indian gravitational wave observatory wins governmental approval
Date Feb 17, 2016; Link : Institute of Physics
Hot on the heels of last week’s monumental discovery of gravitational waves – made by researchers working on the Advanced Laser Interferometer Gravitational wave Observatory (aLIGO) in the US – India’s Union Cabinet has given its “in principle” approval for a similar observatory, dubbed LIGOIndia, to be built in the country. The project will be led by the Indian Initiative in Gravitationalwave Observations (IndIGO), which has been a member of the international LIGO collaboration since 2011 and contributed towards last week’s discovery.
Once built, LIGOIndia will join the global network of LIGO observatories, which currently includes the US, Germany, Italy and Japan.
News Items discussed at the February 8th, 2016 Cosmology Meeting
- China Rover Releases HD Pictures of the Moon
Date 2nd Feb., 2016; Source ZMEScience; Links: The Planetary Society : ZME Science
China’s National Space Administration (CNSA) released hundreds of HD and never before seen images of the Moon. The Rover, known as “Jade Rabbit”, landed in December, 2013, near the crater Zi Wei in the Imbrium Basin.
- Astronomers indirectly spot neutrinos released just 1 second after the “birth” of the universe.
Date 1st Dec., 2015; Physical Review Letters; Links: Scientific American
The cosmic microwave background (CMB), 380,000 years after the big bang, is as far as we have been able to look back to date. Unfortunately this means that it obscures what lies beyond this boundary.
Now astronomers think they have peeked beyond even the CMB by capturing evidence of neutrinos travelling since the cosmos was just a second old.
- What Is Space?
Date 23rd Jan., 2016; Source : Wired.com; Links: Wired : Quanta Magazine
There has long been a conflict between Einstein’s view of gravity and an attempt to produce a theory of quantum gravity. Now a new approach suggests that Space-Time itself derives from quantum time entanglement
- Galactic centre’s gamma rays unlikely to originate from dark matter
Date 3rd Feb., 2016; Physical Review Letters; Links: Science Daily
Previous studies suggested that gamma rays coming from the dense region of space in the inner Milky Way galaxy could be caused when invisible dark matter particles collide.
Using new statistical analysis methods, two research teams, at Princeton and in the Netherlands, have independently found that the gamma ray signals are uncharacteristic of those expected from dark matter.
- 3,200-year-old papyrus contains astrophysical information about the Algol star
Date 17th Dec., 2015; Source PLoS ONE; Links ZMEScience
Many ancient civilizations made astronomical notes, but according to researchers, this is the earliest historical document of naked eye observations on a variable star – Algol, 90 ly distant in the Perseus constellation.
Lauri Jetsu and Sebastian Porceddu, University of Helsinki, said: “Our statistical analysis leads us to argue that the mythological texts of the Cairo Calendar contain astrophysical information about Algol”.