Astronomy: Stars seen forming in a far-off galaxy
Nature 522, 7556 (2015). doi:10.1038/522259a
Astronomers have seen their best glimpse yet of stars forming in the early Universe.The ALMA radio telescope in Chile explored the SDP.81 galaxy, which is 3.6 billion parsecs (11.7 billion light years) away from Earth. Its light was magnified and distorted by the gravitational
The presence of a stratosphere can provide clues about the composition of a planet and how it formed. This atmospheric layer includes molecules that absorb ultraviolet and visible light, acting as a kind of ‘sunscreen’ for the planet it surrounds. Until now, scientists were uncertain whether these molecules would be found in the atmospheres of large, extremely hot planets in other star systems.
The results are published today (12 June) in The Astrophysical Journal.
“Detecting the presence of a stratosphere in an exoplanet and the chemical compound causing it is a major advancement in our ability to study exoplanetary atmospheres,” said co-author Dr Nikku Madhusudhan of the Institute of Astronomy at Cambridge.
In Earth’s atmosphere, the stratosphere sits above the troposphere – the turbulent, active-weather region that reaches from the ground to the altitude where nearly all clouds top out. In the troposphere, the temperature is warmer at the bottom – ground level – and cools down at higher altitudes.
The stratosphere is just the opposite. In this layer, the temperature increases with altitude, a phenomenon called temperature inversion. On Earth, temperature inversion occurs because ozone in the stratosphere absorbs much of the sun’s ultraviolet radiation, preventing it from reaching the surface, protecting the biosphere, and therefore warming the stratosphere instead.
Similar temperature inversions occur in the stratospheres of other planets in our solar system, such as Jupiter and Saturn. In these cases, the culprit is a different group of molecules called hydrocarbons. Neither ozone nor hydrocarbons, however, could survive at the high temperatures of most known exoplanets, which are planets outside our solar system. This leads to a debate as to whether stratospheres would exist on them at all.
“Some of these planets are so hot in their upper atmospheres, they’re essentially boiling off into space,” said Avi Mandell, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a co-author of the study. “At these temperatures, we don’t necessarily expect to find an atmosphere that has molecules that can lead to these multi-layered structures.”
Using NASA’s Hubble Space Telescope, the researchers have settled this debate by identifying a temperature inversion in the atmosphere of WASP-33b, which has about four-and-a-half times the mass of Jupiter. Team members also think they know which molecule in WASP-33b’s atmosphere caused the inversion – titanium oxide.
“These two lines of evidence together make a very convincing case that we have detected a stratosphere on an exoplanet,” said Korey Haynes, lead author of the study. Haynes was a graduate student at George Mason University in Fairfax, Virginia, and was working at Goddard with Mandell when the research was conducted.
The researchers analysed observations made with Hubble’s Wide Field Camera 3 by co-author Drake Deming at the University of Maryland. Wide Field Camera 3 can capture a spectrum of the near-infrared region where the signature for water appears. Scientists can use the spectrum to identify water and other gases in a distant planet’s atmosphere and determine its temperature.
Haynes and her colleagues used the Hubble observations, and data from previous studies, to measure emission from water and compare it to emission from gas deeper in the atmosphere. The team determined that emission from water was produced in the stratosphere at about 3300 degrees Celsius. The rest of the emission came from gas lower in the atmosphere that was at a temperature about 1650 degrees Celsius.
The team also presented the first observational evidence that WASP-33b’s atmosphere contains titanium oxide, one of only a few compounds that is a strong absorber of visible and ultraviolet radiation and capable of remaining in gaseous form in an atmosphere as hot as this one.
“Understanding the links between stratospheres and chemical compositions is critical to studying atmospheric processes in exoplanets,” said Madhusudhan. “Our finding marks a key breakthrough in this direction.”
Inset image: NASA scientists detected a stratosphere and chemical compounds on WASP-33b by measuring light emitted from the dayside atmosphere of the planet observed as it passed behind its star (top). Temperatures in the stratosphere increase with height (right) because of molecules absorbing radiation from the star entering from the top and reemitting it locally; otherwise, temperatures would cool down at higher altitudes (left). Credit: NASA/GSFC
On a blazing-hot exoplanet known as WASP-33b, a team of astronomers including researchers from the University of Cambridge has detected a stratosphere, one of the primary layers of Earth’s atmosphere.Understanding the links between stratospheres and chemical compositions is critical to studying atmospheric processes in exoplanetsNikku Madhusudhan NASA/GSFCOn a massive planet around a nearby star, NASA’s Hubble Space Telescope has detected a stratosphere, one of the primary layers of the atmospheres of Earth and other planets in our solar system.
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Researchers using NASA's Hubble Space Telescope have detected a stratosphere and temperature inversion in the atmosphere of a planet several times the mass of Jupiter, called WASP-33b. Earth's stratosphere sits above the troposphere, the turbulent, active-weather region that reaches from the ground to the altitude where nearly all clouds top out. In the troposphere, the temperature is warmer at the bottom ground level and cools down at higher altitudes. The stratosphere is just the opposite: There, the temperature rises at higher altitudes. This is called a temperature inversion, and it happens because ozone in the stratosphere absorbs some of the sun's radiation, preventing it from reaching the surface and warming this layer of the atmosphere. Similar temperature inversions occur in the stratospheres of other planets in our solar system, such as Jupiter and Saturn. But WASP-33b is so close to its star that its atmosphere is a scathing 10,000 degrees Fahrenheit, and its atmosphere is so hot the planet might actually have titanium oxide rain.
This magnificent spiral galaxy is at the edge of what astronomers call the Local Void. The Local Void is a huge volume of space that is at least 150 million light-years across that doesn't seen to contain anything much. There are no obvious galaxies. This void is simply part of the structure of the universe where matter grows clumpy over time so that galaxies form clusters and chains, which are separated by regions mostly devoid of galaxies. This results in sort of a "soap bubble" structure on large scales. The galaxy, as photographed by NASA's Hubble Space Telescope, is especially colorful where bright red patches of gas can be seen scattered through its spiral arms. Bright blue regions contain newly forming stars. Dark brown dust lanes snake across the galaxy's bright arms and center, giving it a mottled appearance.
Small particles dominate Saturn’s Phoebe ring to surprisingly large distances
Nature 522, 7555 (2015). doi:10.1038/nature14476
Authors: Douglas P. Hamilton, Michael F. Skrutskie, Anne J. Verbiscer & Frank J. Masci
Saturn’s faint outermost ring, discovered in 2009 (ref. 1), is probably formed by particles ejected from the distant moon Phoebe. The ring was detected between distances of 128 and 207 Saturn radii (RS = 60,330 kilometres) from the planet, with a full vertical extent of 40RS, making it well over ten times larger than Saturn’s hitherto largest known ring, the E ring. The total radial extent of the Phoebe ring could not, however, be determined at that time, nor could particle sizes be significantly constrained. Here we report infrared imaging of the entire ring, which extends from 100RS out to a surprisingly distant 270RS. We model the orbital dynamics of ring particles launched from Phoebe, and construct theoretical power-law profiles of the particle size distribution. We find that very steep profiles fit the data best, and that elevated grain temperatures, arising because of the radiative inefficiency of the smallest grains, probably contribute to the steepness. By converting our constraint on particle sizes into a form that is independent of the uncertain size distribution, we determine that particles with radii greater than ten centimetres, whose orbits do not decay appreciably inward over 4.5 billion years, contribute at most about ten per cent to the cross-sectional area of the ring’s dusty component.
Astronomy: Megaflare seen on star surface
Nature 522, 7555 (2015). doi:10.1038/522131d
Astronomers have spotted an enormous surge of light and magnetic energy on a nearby star.A team led by Wouter Vlemmings at Chalmers University of Technology near Gothenburg, Sweden, pointed the ALMA radio telescope in northern Chile at the red giant Mira A, a star