Institute of Astronomy

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Our dream scenario for Philae – and mission finale for Rosetta

Astronomy News - 19 June 2015 - 10:14am

Cinzia Fantinati of the European Space Agency explains how they will get Philae to do science, and how the Rosetta mothership will end its mission







Dual asteroid strike hints at chaos in the inner solar system

Astronomy News - 19 June 2015 - 10:14am

A pair of unrelated asteroids. That's not supposed to happen. What on earth skewed their orbits, and plunged us into ice age?







Chasing shadows: How long can we keep looking for dark matter?

Astronomy News - 19 June 2015 - 10:13am

We've known we need dark matter since the 1930s, but still haven't found it. The search can't go on forever







Revived Philae poised to do comet science

Astronomy News - 19 June 2015 - 10:01am

Revived Philae poised to do comet science

Nature 522, 7556 (2015). http://www.nature.com/doifinder/10.1038/522263a

Author: Elizabeth Gibney

Comet lander has enough power to do experiments but needs a better communications link.

The mass of the Mars-sized exoplanet Kepler-138 b from transit timing

Astronomy News - 19 June 2015 - 10:01am

The mass of the Mars-sized exoplanet Kepler-138 b from transit timing

Nature 522, 7556 (2015). doi:10.1038/nature14494

Authors: Daniel Jontof-Hutter, Jason F. Rowe, Jack J. Lissauer, Daniel C. Fabrycky & Eric B. Ford

Extrasolar planets that pass in front of their host star (transit) cause a temporary decrease in the apparent brightness of the star, providing a direct measure of the planet’s size and orbital period. In some systems with multiple transiting planets, the times of the transits are measurably affected by the gravitational interactions between neighbouring planets. In favourable cases, the departures from Keplerian orbits (that is, unaffected by gravitational effects) implied by the observed transit times permit the planetary masses to be measured, which is key to determining their bulk densities. Characterizing rocky planets is particularly difficult, because they are generally smaller and less massive than gaseous planets. Therefore, few exoplanets near the size of Earth have had their masses measured. Here we report the sizes and masses of three planets orbiting Kepler-138, a star much fainter and cooler than the Sun. We determine that the mass of the Mars-sized inner planet, Kepler-138 b, is Earth masses. Its density is grams per cubic centimetre. The middle and outer planets are both slightly larger than Earth. The middle planet’s density ( grams per cubic centimetre) is similar to that of Earth, and the outer planet is less than half as dense at grams per cubic centimetre, implying that it contains a greater portion of low-density components such as water and hydrogen.

A permanent, asymmetric dust cloud around the Moon

Astronomy News - 19 June 2015 - 10:01am

A permanent, asymmetric dust cloud around the Moon

Nature 522, 7556 (2015). doi:10.1038/nature14479

Authors: M. Horányi, J. R. Szalay, S. Kempf, J. Schmidt, E. Grün, R. Srama & Z. Sternovsky

Interplanetary dust particles hit the surfaces of airless bodies in the Solar System, generating charged and neutral gas clouds, as well as secondary ejecta dust particles. Gravitationally bound ejecta clouds that form dust exospheres were recognized by in situ dust instruments around the icy moons of Jupiter and Saturn, but have hitherto not been observed near bodies with refractory regolith surfaces. High-altitude Apollo 15 and 17 observations of a ‘horizon glow’ indicated a putative population of high-density small dust particles near the lunar terminators, although later orbital observations yielded upper limits on the abundance of such particles that were a factor of about 104 lower than that necessary to produce the Apollo results. Here we report observations of a permanent, asymmetric dust cloud around the Moon, caused by impacts of high-speed cometary dust particles on eccentric orbits, as opposed to particles of asteroidal origin following near-circular paths striking the Moon at lower speeds. The density of the lunar ejecta cloud increases during the annual meteor showers, especially the Geminids, because the lunar surface is exposed to the same stream of interplanetary dust particles. We expect all airless planetary objects to be immersed in similar tenuous clouds of dust.

Astronomy: A Mars-sized exoplanet

Astronomy News - 19 June 2015 - 10:00am

Astronomy: A Mars-sized exoplanet

Nature 522, 7556 (2015). doi:10.1038/522290a

Authors: Gregory Laughlin

Analysis of Kepler data has yielded the smallest known mass for an exoplanet orbiting a normal star. Its mass and size are similar to those of Mars, setting a benchmark for the properties of exoplanets smaller than Earth. See Letter p.321

Astronomy: Stars seen forming in a far-off galaxy

Astronomy News - 19 June 2015 - 9:59am

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

Earth's gravity may force us to do quantum experiments in space

Astronomy News - 17 June 2015 - 9:18am
The same quirk of general relativity that means your head ages faster than your feet may mean we have to go to space to see large-scale quantum mechanics in action (full text available to subscribers)







Philae wake-up kicks off intense planning

Astronomy News - 16 June 2015 - 10:12am

The receipt of signals from Rosetta's Philae lander on 13 June after 211 days of hibernation marked the start of intense activity. In coordination with its mission partners, ESA teams are working to juggle Rosetta's flight plan to help with renewed lander science investigations.

‘Sunscreen’ layer detected on distant planet

Astronomy News - 16 June 2015 - 10:11am

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.


The text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Philae awakes: What next for probe after 7 month nap on comet?

Astronomy News - 16 June 2015 - 10:07am

On Saturday night the German Aerospace Center in Cologne received 85 seconds of incredibly good news: a data chirp from the missing European Space Agency lander Philae







Comet robot Philae phones home again

Astronomy News - 16 June 2015 - 9:53am

Europe's comet lander has again been in touch with Earth, making three short contacts on Sunday.

Pluto's dark and light terrains

Astronomy News - 16 June 2015 - 9:52am

The long-range camera on Nasa's New Horizons probe reveals clear evidence of discrete bright and dark regions on the dwarf planet Pluto.

Philae comet lander wakes up

Astronomy News - 16 June 2015 - 9:52am

The European Space Agency says its comet lander, Philae, has woken up and contacted Earth, seven months after it lost power.

Hubble Telescope Detects 'Sunscreen' Layer on Distant Planet

Astronomy News - 12 June 2015 - 9:32am

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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.

Amazing Sunset Sky Show

Astronomy News - 12 June 2015 - 9:31am
Venus and Jupiter are converging for a must-see close encounter at the end of June. It could be the best backyard sky show of 2015.

NASA’s Hubble Telescope Detects ‘Sunscreen’ Layer on Distant Planet

Astronomy News - 12 June 2015 - 9:29am
NASA’s Hubble Space Telescope has detected a stratosphere, one of the primary layers of Earth’s atmosphere, on a massive and blazing-hot exoplanet known as WASP-33b.

#RosettaWatch: Search party may have found missing lander Philae

Astronomy News - 12 June 2015 - 9:28am

After a painstaking search, Rosetta mission managers have ruled out four of five possible landing sites – but that doesn't mean Philae is really there







'Best candidates' for lost Philae

Astronomy News - 12 June 2015 - 9:22am

The European Space Agency releases some pictures that may include its lost comet lander, Philae.