|Current Workshop | Overview||Back | Home | Search ||
Rocks, Rubble and Rings: Understanding Deep and Irregular Transits
We are at a very exciting point in understanding how planets and moons are formed around other stars. After twenty years of indirectly detecting planets by the physical effects they have on their parent stars, we are now discovering new phenomena caused by other material in these star systems. One of the most successful methods for detecting exoplanets to date is the transit method, where the orbit of an extrasolar planet brings the planet in front of the parent star and blocks out a small fraction of the stellar disk, causing the star to dim for several hours at a level of a percent (or less).
Since the star provides the light for the detection and not the planet, small telescopes can detect extrasolar transiting planets. There are many such camera systems that take pictures of a region of night sky every few minutes, and repeat this all night for many months at a time, and over three hundred exoplanets have been discovered in stellar light curves obtained from the ground alone. The flood of data from these cameras produces light curves for tens of millions of stars in the sky. Along with the discovery of transiting extrasolar planets, there have been surprising discoveries of new transient phenomena around stars – including disintegrating planets with tails, evaporating comets, warps in disks around young stars, giant exoring systems, to name a few.
The sensitivity of Kepler has revealed several stars with irregular light curves that show the star being blocked by 50% and then brightening back up within a matter of hours – likely due to objects millions of kilometers in diameter and moving at velocities of tens of kilometers per second passing in front of the star. These are referred to as “dippers” and over a dozen have been analysed, with more discoveries appearing in the literature every week.
A Disk or Ring Around the Giant Exoplanet β Pic b in 2017?
One of the few directly imaged planets is orbiting around the bright southern hemisphere star β Pictoris. Discovered five years ago, images of this planet show that its orbit is almost edge-on to our line of sight, and that the most likely time for a transit of the planet in front of its parent star is in the middle of 2017. Previous data from 1981 show that the star flickered for several days, consistent with material near the planet blocking out the light of the star. Such flickering has not been seen since. As the planet is a relatively small target, if the 1981 event was indeed associated with the planet, then it was likely due to an extended distribution of matter in the form of rings. Evidence for such giant systems of rings in another stellar system, the “super-Saturn” system called J1407b, with rings over 200 times larger than those around Saturn. Such a system may well exist around β Pictoris b, and coordinating an observational campaign is crucial. The workshop is an ideal venue to discuss and plan observing strategies for this upcoming event.
This workshop will bring together the growing community of astronomers who are discovering these unusual and transient phenomena in both ground and space data. The workshop topic is very timely as several instances of these new unusual transiting phenomena have been discovered over the past few years, and current and upcoming ground-based (e.g. LSST) and space-based (e.g. TESS, Gaia) projects will likely uncover many more of these objects in the near future.
We intend to:
· Summarise previous known astrophysical phenomena
· Brainstorm new methods of identifying these light curves in large time-series photometry data sets
· Form working groups to analyse light curves and test hypotheses about the nature of the transiting matter
· Look at what to expect from upcoming wide-field survey telescopes and other Kepler-like space missions