Free Astronomy Magazine January-February 2018

20 JANUARY-FEBRUARY 2018 SPACE CHRONICLES — six times greater than Jupiter’s — pulls the titanium dioxide snow out of the upper atmosphere and traps it in the lower atmosphere. Astronomers using Hubble didn’t look for titanium oxide specifically. Instead, they observed that the giant planet’s atmosphere is cooler at higher altitudes, which is con- trary to what was expected. This finding led the researchers to con- clude that a light-absorbing gaseous form of titanium oxide, commonly found in this class of star-hugging, gas giant planet known as a “hot Jupiter,” has been removed from the dayside’s atmosphere. The Hubble observations represent the first time astronomers have detected this pre- cipitation process, called a “cold trap,” on an exoplanet. Without the titanium oxide gas to absorb in- coming starlight on the daytime side, the atmospheric temperature grows colder with in- creasing altitude. Normally, titanium oxide in the atmospheres of hot Jupiters absorbs light and reradiates it as heat, making the atmosphere grow warmer at higher altitudes. Hubble observes exoplanet that snows sunscreen by NASA N ASA’s Hubble Space Telescope has found a blistering hot planet outside our solar sys- tem where it “snows” sunscreen. The problem is the sunscreen (tita- nium dioxide) precipitation only happens on the planet’s permanent nighttime side. Any possible visitors to the exoplanet, called Kepler- 13Ab, would need to bottle up some of that sunscreen, because they won’t find it on the sizzling hot, daytime side, which always faces its host star. Hubble as- tronomers suggest that powerful winds carry the titanium oxide gas around to the colder nighttime side, where it condenses into crystalline flakes called titanium dioxide, forms clouds, and precipitates as snow. Kepler-13Ab’s strong surface gravity T his illustration shows the seeth- ing hot planet Kepler-13Ab that circles very close to its host star, Ke- pler-13A. Seen in the background is the star’s binary companion, Kepler- 13B, and the third member of the multiple-star system is the orange dwarf star Kepler-13C. [NASA, ESA, and G. Bacon (STScI)]