Tag Archives: NASA

NASA’s Hubble Telescope Detects ‘Sunscreen’ Layer on WASP-33b

NASA have put out a press release about Hubble Space Telescope observations of WASP-33b.

WASP-33b is the hottest of the WASP planets, being the only one so far found orbiting a very hot A-type star. A team led by Korey Haynes from NASA’s Goddard Space Flight Center, have used Hubble to show that WASP-33b has a “stratosphere”. The spectrum in the infra-red is best explained by a temperature inversion caused by the presence of Titanium Oxide in the atmosphere.

Titanium Oxide is noted for its ability to absorb light, which is why it is often used in sunscreen lotion. NASA’s graphic shows how an absorbing layer in the atmosphere produces a “temperature inversion” with a hotter layer higher up:

WASP-33b stratosphere

WASP-33b’s stratosphere was detected by measuring the drop in light as the planet passed behind its star (top). Temperatures in the low stratosphere rise because of molecules absorbing radiation from the star (right). Without a stratosphere, temperatures would cool down at higher altitudes (left). [Image: NASA/GSFC]

By comparing models with and without a temperature inversion to the spectrum of WASP-33b, as observed with Hubble’s WFC3 instrument, Haynes et al “make a very convincing case that we have detected a stratosphere on an exoplanet”.

Spectrum of stratosphere in WASP-33b

The figure shows the spectrum of WASP-33b (left) and the temperature profile of the atmosphere (right), both for models with a temperature inversion (red) and without an inversion (blue). (From Haynes et al 2015)

The work has been reported widely, in over 100 news and science websites, such as by SciTechDaily, Pioneer News, The Daily Mail, and NY City Today.

NASA’s Chandra X-ray Observatory observes WASP-18

NASA have put out a press release about an observation of WASP-18 by the Chandra X-ray observatory.

WASP-18 was the first planet discovered to have an orbital period of less than 1 day and has the highest tidal interaction between a planet and a star of any known planetary system.

“We think the planet is ageing the star by wreaking havoc on its innards”, report the authors of the paper, “The planet’s gravity may cause motions of gas in the interior of the star that weaken the convection”, which “results in the magnetic field becoming weaker and the star to age prematurely”.

NASA have also produced a nice graphic of WASP-18 and its planet (image credit: NASA/CXC/M.Weiss):

wasp18_chandra

The press release has been picked up by several media outlets including Astronomy magazine, Phys.org, the Daily Mail online, and the International Business Times. (Spot the error in the last outlet’s sentence that: “Scientists have used data provided by NASA’s Chandra X-ray Observatory to find a planet that causes the star it orbits to act much older than it actually is, according to a new study” (added emphasis)!)

NASA finds water on three WASP planets

A team using NASA’s Hubble Space Telescope has detected water in the atmosphere of five exoplanets. Three of these are WASP planets, WASP-12b, WASP-17b and WASP-19b. They were chosen because they orbit relatively bright stars and because they are close-in “hot Jupiter” planets with bloated and puffed-up atmospheres, the best targets for the highly demanding task of discerning molecules in those atmospheres. This study demonstrates how valuable WASP planets are for exoplanet research.

WASP-12b illustration.

An artist’s conception of WASP-12b, a hot-Jupiter planet orbiting so closely that its atmosphere is blasted by irradiation from its star

The NASA press release has been reported by websites and newspapers worldwide. It reads:

Hubble Traces Subtle Signals of Water on Hazy Worlds      Dec. 3, 2013

Using the powerful­ eye of NASA’s Hubble Space Telescope, two teams of scientists have found faint signatures of water in the atmospheres of five distant planets.

The presence of atmospheric water was reported previously on a few exoplanets orbiting stars beyond our solar system, but this is the first study to conclusively measure and compare the profiles and intensities of these signatures on multiple worlds.

The five planets — WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b — orbit nearby stars. The strengths of their water signatures varied. WASP-17b, a planet with an especially puffed-up atmosphere, and HD209458b had the strongest signals. The signatures for the other three planets, WASP-12b, WASP-19b and XO-1b, also are consistent with water.

“We’re very confident that we see a water signature for multiple planets,” said Avi Mandell, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and lead author of an Astrophysical Journal paper, published today, describing the findings for WASP-12b, WASP-17b and WASP-19b. “This work really opens the door for comparing how much water is present in atmospheres on different kinds of exoplanets, for example hotter versus cooler ones.”

The studies were part of a census of exoplanet atmospheres led by L. Drake Deming of the University of Maryland in College Park. Both teams used Hubble’s Wide Field Camera 3 to explore the details of absorption of light through the planets’ atmospheres. The observations were made in a range of infrared wavelengths where the water signature, if present, would appear. The teams compared the shapes and intensities of the absorption profiles, and the consistency of the signatures gave them confidence they saw water. The observations demonstrate Hubble’s continuing exemplary performance in exoplanet research.

“To actually detect the atmosphere of an exoplanet is extraordinarily difficult. But we were able to pull out a very clear signal, and it is water,” said Deming, whose team reported results for HD209458b and XO-1b in a Sept. 10 paper in the same journal. Deming’s team employed a new technique with longer exposure times, which increased the sensitivity of their measurements.

The water signals were all less pronounced than expected, and the scientists suspect this is because a layer of haze or dust blankets each of the five planets. This haze can reduce the intensity of all signals from the atmosphere in the same way fog can make colors in a photograph appear muted. At the same time, haze alters the profiles of water signals and other important molecules in a distinctive way.

The five planets are hot Jupiters, massive worlds that orbit close to their host stars. The researchers were initially surprised that all five appeared to be hazy. But Deming and Mandell noted that other researchers are finding evidence of haze around exoplanets.

“These studies, combined with other Hubble observations, are showing us that there are a surprisingly large number of systems for which the signal of water is either attenuated or completely absent,” said Heather Knutson of the California Institute of Technology, a co-author on Deming’s paper. “This suggests that cloudy or hazy atmospheres may in fact be rather common for hot Jupiters.”Hubble’s high-performance Wide Field Camera 3 is one of few capable of peering into the atmospheres of exoplanets many trillions of miles away. These exceptionally challenging studies can be done only if the planets are spotted while they are passing in front of their stars. Researchers can identify the gases in a planet’s atmosphere by determining which wavelengths of the star’s light are transmitted and which are partially absorbed.