It’s been a week for unusual planetary systems, and I’ll cap it off with Kepler-80, a star about 1100 light years away that features five planets in extraordinarily tight orbits. Such systems are now being referred to as STIPs (Systems with Tightly-spaced Planets), a nod to our apparently imperishable drive to create acronyms. Whatever we call them, though, systems like these make us realize that our own Solar System’s configuration is but one possibility in a sea of other outcomes. Yesterday’s post on ‘warm Jupiters’ is yet another confirmation of the thought. What we have in new work from Mariah MacDonald, Darin Ragozzine (Florida Institute of Technology) and colleagues is an analysis of transit timing variations (TTVs) of the planets around this star, all of which orbit inside 1/10 AU. Here the planets’ years are 1.0, 3.1, 4.6, 7.1 and 9.5 days, respectively, close enough that gravitational perturbations can create slight changes in transit times. Although the innermost planet has...

Where exactly do ‘hot Jupiters’ come from? I usually see explanations involving planetary migration for Jupiter-class objects with tight orbital periods of 10 days or less, the thinking being that such planets are too close to their host stars to have accumulated a Jovian-style gaseous envelope there. Migration explains their placement, with gas giants forming much further out in their planetary systems and then migrating disruptively inward to become hot Jupiters. Does the scenario work? Consider the hot Jupiter WASP-47b, which has two low-mass planets nearby in its system. WASP-47b is a problem because a migrating gas giant should have produced profound gravitational issues for small worlds in the inner system, likely ejecting them entirely. A new paper from Chelsea Huang and Yanqin Wu (University of Toronto), working with Amaury Triaud (University of Cambridge), tries to explain the dilemma posed by WASP-47b. The answer turns out to be that, according to Kepler data used by the...

Small red stars are drawing increased attention as we continue to discover interesting planets around them. The past two days we've looked at the four worlds around K2-72, a red dwarf about 225 light years out in the constellation Aquarius. That two of these worlds have at least the potential for liquid water on the surface makes the system a prime target for further study. Now we return to another recently discussed system of note, TRAPPIST-1. Designated 2MASS J23062928-0502285, this ultracool dwarf is also in Aquarius, though at forty light years, much the closer target. As with K2-72, we have multiple planets here (three), and also like the K2 discovery, TRAPPIST-1 orbits a star small and dim enough to make planet detection easier -- a transiting world presents a clear signature and the study of planetary atmospheres is possible through what is known as transmission spectroscopy, wherein light from the star that has passed through the planet's atmosphere is analyzed. Today we have...

Is the K2-72 system, discussed yesterday as part of a recent exoplanet announcement from Ian Crossfield and colleagues, as intriguing as it looks? Ravi Kopparapu has some thoughts on the matter. Dr. Kopparapu's work on exoplanet habitability is well known to Centauri Dreams readers -- he offered an overview in these pages called How Common Are Potential Habitable Worlds in Our Galaxy?, which ran in 2014. An assistant research scientist at NASA GSFC and the University of Maryland, Dr. Kopparapu began his exoplanet career with James Kasting at Penn State following work on the LIGO collaboration enroute to his PhD from Louisiana State. Analyzing habitable zone possibilities around different kind of stars, as well as modeling and characterizing exoplanet atmospheres, plays a major role in his research interests. I was pleased to receive the following note on the recently announced K2-72 system and want to run his thoughts today given the interest this unusual system has already begun to...

Today’s announcement of the confirmation of over 100 planets using K2 data reminds me of how much has gone into making K2 a success. You’ll recall that K2 emerged when the Kepler spacecraft lost function in two of its four reaction wheels. Three of these were needed for pointing accuracy, but ingenious pointing techniques and software updates have made K2 into a potent project of its own. The latest announcements demonstrate that certain benefits emerged from the changed mission parameters, especially in the ability of K2 to move away from the original field of view (toward Cygnus and Lyra) and focus on targets in the ecliptic plane. What we gain from that change is that working in the ecliptic allows more chances for observation from ground-based observatories in both northern and southern hemispheres as they perform the needed exoplanet follow-up. But there are other factors that make K2 potent. With all targets being chosen by the entire scientific community (not limited to the...

A team led by Lucas Cieza (Universidad Diego Portales, Santiago, Chile) has produced the first image directly showing the water snowline in a protoplanetary disk, using the Atacama Large Millimeter/submillimeter Array (ALMA). It's fascinating to actually see a mechanism we've long discussed in these pages when analyzing exoplanetary systems (or for that matter, our own). We have a young star called V883 Orionis to thank for the possibility. It's an FU Orionis star of the kind we recently looked at in FU Orionis: Implications of Sudden Brightening for Planet Formation. And here, too, the implications are rich. FU Orionis stars are young, pre-main sequence objects that can produce extreme changes in magnitude and spectral type. The eponymous FU Orionis itself, 1500 light years away in the constellation Orion, underwent an event in 1936 that took it from a visual magnitude of 16.5 to 9.6. In the case of V883 Orionis, a similar outburst in temperature and luminosity has heated the...

A brown dwarf as a 'quieter' version of Jupiter? That's more or less the picture offered in a new paper on WISE 0855 from Andrew Skemer (UC-Santa Cruz) and colleagues. Here we're working in the Solar System's close neighborhood -- WISE 0855 is a scant 7.2 light years from Earth -- and we're observing an object that is the coldest known outside of the Solar System. That makes the observational task difficult, but it has yielded rich results in the discovery of clouds of water or water ice. We learn that WISE 0855 is about five times the mass of Jupiter, with a temperature in the range of 250 K (-23 Celsius). This is the nearest known object of planetary mass, but it is too faint to characterize with conventional spectroscopy -- separating light into its component wavelengths -- in the optical or near infrared. But it turns out the object can be studied through thermal emissions from deep in its atmosphere in the range of 5 µm (a range frequently used to study Jupiter's own deep...

Into the annals of oddball orbits now comes HD 131399Ab, a planet whose wide orbit inside a triple-star system is unlike anything we've yet seen. 320 light years from Earth in the constellation Centaurus, this is a gas giant of about four Jupiter masses that was discovered through direct imaging. The discovery was made with the European Southern Observatory's Very Large Telescope in Chile using the SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument, which exploits differential imaging to screen stellar light from planetary signatures. HD 131399Ab is the first exoplanet discovered by SPHERE, which incorporates adaptive optics, a coronagraph and, with its differential imaging features, distinguishes a planet by the polarization of reflected light. Stars emit unpolarized light -- here the electromagnetic waves oscillate randomly, and in different directions, as explained in this ESO news release. But light reflected from a planetary surface is partially polarized,...