For one brief shining moment after the 2015 detection of gravitational waves from colliding black holes, astronomers held out hope that the universe's mysterious dark matter might consist of a plenitude of black holes sprinkled throughout the universe.
Based on a statistical analysis of 740 of the brightest supernovas discovered as of 2014, and the fact that none of them appear to be magnified or brightened by hidden black hole "gravitational lenses," the researchers concluded that primordial black holes can make up no more than about 40 percent of the dark matter in the universe. Primordial black holes could only have been created within the first milliseconds of the Big Bang as regions of the universe with a concentrated mass tens or hundreds of times that of the sun collapsed into objects a hundred kilometers across.The results suggest that none of the universe's dark matter consists of heavy black holes, or any similar object, including massive compact halo objects, so-called MACHOs.
Kepler-1625b i is tantalising, but I have to say I'm still somewhat sceptical. The original exomoon signatures in the Kepler transit data don't look anywhere near as compelling, thanks to better removal of systematics in the latest DR. The TTVs are pretty compelling, and the other new HST stuff is interesting though I don't think it has high significance (I don't really know how to assign a proper significance number to this! For exoplanets it's easy(-ish) ). The data is consistent with it being an exomoon, but as the article says, eliminating a 2nd planet would be a big step towards proving it. On the plus side, it transits so all we need to do is get more observations --- Tony
@jebbo: Regarding significance of the HST result, what do you think of the approach the authors actually take? Their M model seems to be strongly favored over the P (planet only), T (TTVs) and Z (Moon but only TTV aspect) models.
If it is a planetary capture could the moon have moons in turn?
Each of the giant planets within the Solar System has large moons but none of these moons have their own moons (which we call submoons). By analogy with studies of moons around short-period exoplanets, we investigate the dynamical stability of submoons. We find that 10 km-scale submoons can only survive around large (1000 km-scale) moons on wide-separation orbits. Tidal dissipation destabilizes the orbits of submoons around moons that are small or too close to their host planet; this is the case for most of the Solar System's moons. A handful of known moons are, however, capable of hosting long-lived submoons: Saturn's moons Titan and Iapetus, Jupiter's moon Callisto, and Earth's Moon. Based on its inferred mass and orbital separation, the newly-discovered exomoon candidate Kepler-1625b-I can, in principle, host submoons, although its large orbital inclination may pose a difficulty for dynamical stability. The existence, or lack thereof, of submoons, may yield important constraints on satellite formation and evolution in planetary systems.
The @NASA #technosigs18 workshop talks are now up!(link: https://www.hou.usra.edu/meetings/technosignatures2018/agenda/) hou.usra.edu/meetings/techn…@jilltarter
Michael New discusses why the workshop was about "technosignatures" and not #SETI at 13:00 ish:(link: https://www.hou.usra.edu/meetings/technosignatures2018/presentation/new.mp4) hou.usra.edu/meetings/techn…Somewhat archly admits that the term "SETI" tends to provoke "antibodies" at @NASA
Also, Martin Still is mistaken in that video about XRP being open to #SETI proposals—as recently as last year such proposals were explicitly out of scope of that program.
A Caltech-led team of researchers has observed the peculiar death of a massive star that exploded in a surprisingly faint and rapidly fading supernova. These observations suggest that the star has an unseen companion, gravitationally siphoning away the star's mass to leave behind a stripped star that exploded in a quick supernova. The explosion is believed to have resulted in a dead neutron star orbiting around its dense and compact companion, suggesting that, for the first time, scientists have witnessed the birth of a compact neutron star binary system.
Australian researchers using a CSIRO radio telescope in Western Australia have nearly doubled the known number of ‘fast radio bursts’— powerful flashes of radio waves from deep space.The team’s discoveries include the closest and brightest fast radio bursts ever detected.
The star known as Cl Tau lies roughly 500 light years away, which is a stone’s throw in astronomical terms, and scientists now believe it’s being orbited by some truly massive planets. That wouldn’t necessarily be odd, as exoplanets are spotted on a regular basis with modern telescope technology, but what makes this system so unique is that the star itself is only thought to be around two million years old.
An international team of astronomers using the VIMOS instrument of ESO’s Very Large Telescope have uncovered a titanic structure in the early Universe. This galaxy proto-supercluster — which they nickname Hyperion — was unveiled by new measurements and a complex examination of archive data. This is the largest and most massive structure yet found at such a remote time and distance — merely 2 billion years after the Big Bang.
About 99 percent of the Sun's energy emitted as neutrinos is produced through nuclear reaction sequences initiated by proton-proton (pp) fusion in which hydrogen is converted into helium, say scientists including physicist Andrea Pocar at the University of Massachusetts Amherst. Today they report new results from Borexino, one of the most sensitive neutrino detectors on the planet, located deep beneath Italy's Apennine Mountains.
A first 'snapshot' of the complete spectrum of neutrinos emitted by the sunQuoteAbout 99 percent of the Sun's energy emitted as neutrinos is produced through nuclear reaction sequences initiated by proton-proton (pp) fusion in which hydrogen is converted into helium, say scientists including physicist Andrea Pocar at the University of Massachusetts Amherst. Today they report new results from Borexino, one of the most sensitive neutrino detectors on the planet, located deep beneath Italy's Apennine Mountains.