Jason Wright is currently discussing these results on his Twitter feed.
Astronomer Tabetha "Tabby" Boyajian joined Paul Carr, Roger Wehbe, and Rusty Schweikart in a Google Hangout to talk about the implications of the Gaia Data Release 1 for a better understanding of KIC 8462852.
There's also yet another paper on everyone's favorite star on arxiv today: http://arxiv.org/abs/1609.04032
Quote from: as58 on 09/15/2016 10:17 amThere's also yet another paper on everyone's favorite star on arxiv today: http://arxiv.org/abs/1609.04032Well if you were building a Dyson swarm out of your solar system like any building site you'd end up with a lot of 'builders rubble' so to speak.
Quote from: Star One on 09/15/2016 11:37 amQuote from: as58 on 09/15/2016 10:17 amThere's also yet another paper on everyone's favorite star on arxiv today: http://arxiv.org/abs/1609.04032Well if you were building a Dyson swarm out of your solar system like any building site you'd end up with a lot of 'builders rubble' so to speak.There probably would be a good deal of material left over. If you were an ET with a newly built mega structure you wouldn't want all that orbiting rubble to eventually pulverize what you work so hard on making. It could be incorporated into the collectors to add mass and make them slower to react to the effects of light pressure from the host star. With all that available energy the debris could just be collected or sent to a safe location. Either way it wouldn't be contributing to excess IR. That is the problem with the alien hypothesis though. It is so easy to bend it to match the observations.
As Jason Wright said aliens can't violate thermodynamics so they are either radiating all that IR in a direction away from us or they are sending the energy out of the system. Because so much of the star's light was blocked it puts some rather harsh constraints on how efficient a potential energy collection structure could be. It would also have to be arraigned in a disk and we would have to be seeing it edge on. It is the profound lack of IR excess that makes this star so baffling.
Quote from: notsorandom on 09/15/2016 08:49 pmAs Jason Wright said aliens can't violate thermodynamics so they are either radiating all that IR in a direction away from us or they are sending the energy out of the system. Because so much of the star's light was blocked it puts some rather harsh constraints on how efficient a potential energy collection structure could be. It would also have to be arraigned in a disk and we would have to be seeing it edge on. It is the profound lack of IR excess that makes this star so baffling.Surely us looking at the star at an angle from the Earth would be an obvious answer, if anything with an IR excess is pointing away from us how would we expect to see it?
Quote from: Star One on 09/15/2016 09:27 pmQuote from: notsorandom on 09/15/2016 08:49 pmAs Jason Wright said aliens can't violate thermodynamics so they are either radiating all that IR in a direction away from us or they are sending the energy out of the system. Because so much of the star's light was blocked it puts some rather harsh constraints on how efficient a potential energy collection structure could be. It would also have to be arraigned in a disk and we would have to be seeing it edge on. It is the profound lack of IR excess that makes this star so baffling.Surely us looking at the star at an angle from the Earth would be an obvious answer, if anything with an IR excess is pointing away from us how would we expect to see it?We wouldn't. Because we see such extreme dimming and yet no IR excess we can rule out some scenarios both natural and ETI based. Basically all the ETI based explanations except for a thin disk edge on or sending all that energy out of the system are ruled out. Aliens are still in play as an explanation but only if they are doing exactly that. Sadly for the aliens something in the interstellar medium also fits the data pretty well if not better. The Gaia data looks to have ruled out a further away star that is abnormally bright but it doesn't look to do much to differentiate between interstellar medium and ETI. We are basically waiting to get the spectrum of another dip. That would be the best diagnostic we could hope for. Until that happens I doubt the mystery will be solved.
Could not agree more. Separate K2, et. science mission from Tabby's star speculation & information.
Lonely planets can blame big, pushy bullies. Giant planets may bump off most of their smaller brethren, partly explaining why the Kepler space telescope has seen so many single-planet systems.Of the thousands of planetary systems Kepler has discovered, about 80 per cent appear as single planets passing in front of their stars. The rest feature as many as seven planets – a distinction dubbed the Kepler dichotomy.Recent studies suggest even starker differences. While multiple-planet systems tend to have circular orbits that all lie in the same plane – like our solar system – the orbits of singletons tend to be more elliptical and are often misaligned with the spins of their stars.
What makes a rocky planet Earth-like?Astronomers and geoscientists have joined forces using data from the Sloan Digital Sky Survey (SDSS) to study the mix of elements in exoplanet host stars, and to consider what this reveals about their planets.In results presented today at the American Astronomical Society (AAS) meeting in Grapevine, Texas, astronomer Johanna Teske explained, “our study combines new observations of stars with new models of planetary interiors. We want to better understand the diversity of small, rocky exoplanet composition and structure — how likely are they to have plate tectonics or magnetic fields?”Earth-sized planets have been found around many stars — but Earth-sized does not necessarily mean Earth-like. Some of these Earth-sized planets have been found orbiting stars with chemical compositions quite different from our Sun, and those differences in chemistry could have important consequences.Astronomers in the Sloan Digital Sky Survey have made these observations using the APOGEE (Apache Point Observatory Galactic Evolution Experiment) spectrograph on the 2.5m Sloan Foundation Telescope at Apache Point Observatory in New Mexico. This instrument collects light in the near-infrared part of the electromagnetic spectrum and disperses it, like a prism, to reveal signatures of different elements in the atmospheres of stars. A fraction of the almost 200,000 stars surveyed by APOGEE overlap with the sample of stars targeted by the NASA Kepler mission, which was designed to find potentially Earth-like planets. The work presented today focuses on ninety Kepler stars that show evidence of hosting rocky planets, and which have also been surveyed by APOGEE.In particular, Teske and colleagues presented solar systems around the stars Kepler 102 and Kepler 407. Kepler 102 is slightly less luminous than the Sun and has five known planets; Kepler 407 is a star almost identical in mass to the Sun and hosts at least two planets, one with a mass less than 3 Earth masses.“Looking at these two exoplanet systems in particular,” Teske explains, “we determined that Kepler 102 is like the Sun, but Kepler 407 has a lot more silicon.”
(Submitted on 11 Jan 2017) We present the discovery of two extended ~0.12 mag dimming events of the weak-lined T-Tauri star V1334. The start of the first event was missed but came to an end in late 2003, and the second began in February 2009, and continues as of November 2016. Since the egress of the current event has not yet been observed, if this event is periodic, suggests a period of >13 years. Spectroscopic observations may suggest the presence of a small inner disk, although the spectral energy distribution shows no infrared excess. We explore the possibility that the extending dimming event is caused by an orbiting body (e.g. a disk warp or dust trap), enhanced disk winds, hydrodynamical fluctuations of the inner disk, or a significant increase in the magnetic field flux at the surface of the star. We also find a ~0.32 day periodic photometric signal that persists throughout the 2009 dimming which appears to not be due to ellipsoidal variations from a close stellar binary. High precision photometric observations of V1334 Tau during the K2 campaign 13 combined with simultaneous photometric and spectroscopic observations from the ground will provide crucial information about the photometric variability and its origin.
Intermediate polars are interesting binary systems because the low-density star drops gas toward the compact dwarf, which catches the matter using its strong magnetic field and funnels it to the surface, a process called accretion. The gas emits X-rays and optical light as it falls, and we see regular light variations as the stars orbit and spin. Graduate student Mark Kennedy studied the light variations in detail during the three months the Kepler Space Telescope was pointing at FO Aquarii in 2014. Kennedy is a Naughton Fellow from University College, Cork, in Ireland who spent a year and a half working at Notre Dame on interacting binary stars. “Kepler observed FO Aquarii every minute for three months, and Mark’s analysis of the data made us think we knew all we could know about this star,” Garnavich said.Once Kepler was pointed in a new direction, Garnavich and his group used the Krizmanich Telescope to continue the study.“Just after the star came around the sun last year, we started looking at it through the Krizmanich Telescope, and we were shocked to see it was seven times fainter than it had ever been before,” said Colin Littlefield, a member of the Garnavich lab. “The dimming is a sign that the donating star stopped sending matter to the compact dwarf, and it’s unclear why. Although the star is becoming brighter again, the recovery to normal brightness has been slow, taking over six months to get back to where it was when Kepler observed.”“Normally, the light that we’d see would come from the accretion energy, and it got a lot weaker when the gas flow stopped. We are now following the recovery over months,” Garnavich said.One theory is that a star spot, a cool region on the companion, rotated into just the right position to disrupt the flow of hydrogen from the donating star. But that doesn’t explain why the star hasn’t then recovered as quickly as it dimmed.Garnavich and his team also found that the light variations of FO Aquarii became very complex during its low state. The low gas transfer rate had meant the dominant, 20-minute signal had faded and allowed other periods to show up. Instead of a steady 20 minutes between flashes, sometimes there was an 11-minute signal and at other times a 21-minute pulse.“We had never seen anything like this before,” Garnavich said. “For two hours, it would flash quickly and then the next two hours it would pulse more slowly.”
Updated Masses for the TRAPPIST-1 Planets (arXiv)QuoteThe newly detected TRAPPIST-1 system, with seven low-mass, roughly Earth-sized planets transiting a nearby ultra-cool dwarf, is one of the most important exoplanet discoveries to date. The short baseline of the available discovery observations, however, means that the planetary masses (obtained through measurement of transit timing variations of the planets of the system) are not yet well constrained. The masses reported in the discovery paper were derived using a combination of photometric timing measurements obtained from the ground and from the Spitzer spacecraft, and have uncertainties ranging from 30\% to nearly 100\%, with the mass of the outermost, P=18.8d, planet h remaining unmeasured. Here, we present an analysis that supplements the timing measurements of the discovery paper with 73.6 days of photometry obtained by the K2 Mission. Our analysis refines the orbital parameters for all of the planets in the system. We substantially improve the upper bounds on eccentricity for inner six planets (finding e<0.02 for inner six known members of the system), and we derive masses of 0.79±0.27M⊕, 1.63±0.63M⊕, 0.33±0.15M⊕, 0.24+0.56−0.24M⊕, 0.36±0.12M⊕, 0.566±0.038M⊕, and 0.086±0.084M⊕ for planets b, c, d, e, f, g, and h, respectively.QuoteFigure 4 indicates that – to within the errors of our determinations – the four most distant planets are consistent with pure water compositions, and in any event, are substantially less dense either Mars or Venus.
The newly detected TRAPPIST-1 system, with seven low-mass, roughly Earth-sized planets transiting a nearby ultra-cool dwarf, is one of the most important exoplanet discoveries to date. The short baseline of the available discovery observations, however, means that the planetary masses (obtained through measurement of transit timing variations of the planets of the system) are not yet well constrained. The masses reported in the discovery paper were derived using a combination of photometric timing measurements obtained from the ground and from the Spitzer spacecraft, and have uncertainties ranging from 30\% to nearly 100\%, with the mass of the outermost, P=18.8d, planet h remaining unmeasured. Here, we present an analysis that supplements the timing measurements of the discovery paper with 73.6 days of photometry obtained by the K2 Mission. Our analysis refines the orbital parameters for all of the planets in the system. We substantially improve the upper bounds on eccentricity for inner six planets (finding e<0.02 for inner six known members of the system), and we derive masses of 0.79±0.27M⊕, 1.63±0.63M⊕, 0.33±0.15M⊕, 0.24+0.56−0.24M⊕, 0.36±0.12M⊕, 0.566±0.038M⊕, and 0.086±0.084M⊕ for planets b, c, d, e, f, g, and h, respectively.
Figure 4 indicates that – to within the errors of our determinations – the four most distant planets are consistent with pure water compositions, and in any event, are substantially less dense either Mars or Venus.
A critical bottleneck for stellar astrophysics and exoplanet science using data from the Kepler mission has been the lack of precise radii and evolutionary states of the observed target stars. Here we present revised radii of 186,813 Kepler stars derived by combining parallaxes from Gaia Data Release 2 with the DR25 Kepler Stellar Properties Catalog. The median radius precision is ≈8%, a factor 4-5 improvement over previous estimates for typical Kepler stars. We find that ≈65% (≈ 128,000) of all Kepler targets are main-sequence stars, ≈23% (≈ 40,600) are subgiants, and ≈12% (≈ 23,000) are red giants, demonstrating that subgiant contamination is less severe than previously thought and that the Kepler parent population mostly consists of unevolved main-sequence stars. Using the revised stellar radii, we recalculate the radii for 2218 confirmed and 1958 candidate exoplanets. Our results confirm the presence of a gap in the radius distribution of small, close-in planets, but yield evidence that the gap is mostly limited to incident fluxes >200F⊕ and may be located closer to 2R⊕. We furthermore find several confirmed exoplanets which occupy the "hot super-Earth desert", detect direct evidence for a correlation of gas-giant planet inflation with increasing incident flux, and establish a bona-fide sample of 8 confirmed planets and 34 planet candidates with <2R⊕ in the habitable zone. The results presented here demonstrate the enormous potential for the precise characterization of stellar and exoplanet populations using the transformational dataset provided by Gaia.