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Clear skies on exo-Neptune - Smallest exoplanet ever found to have water vapour [heic1420]

Astronomy News - 24 September 2014 - 6:00pm
Astronomers using data from the NASA/ESA Hubble Space Telescope, the Spitzer Space Telescope, and the Kepler Space Telescope have discovered clear skies and steamy water vapour on a planet outside our Solar System. The planet, known as HAT-P-11b, is about the size of Neptune, making it the smallest exoplanet ever on which water vapour has been detected. The results will appear in the online version of the journal Nature on 24 September 2014.

Water found in atmosphere of exo-Neptune

Astronomy News - 24 September 2014 - 6:00pm
The smallest exoplanet yet to have its atmosphere probed is full of water and heavy elements, hinting it formed far from its star






Clear skies on exo-Neptune

Astronomy News - 24 September 2014 - 6:00pm

Astronomers have discovered clear skies and steamy water vapour on a gaseous planet outside our solar system. The planet, known as HAT-P-11b, is about the size of Neptune, making it the smallest-ever planet for which water vapour has been detected.

Using data from the NASA/ESA Hubble Space Telescope, the Spitzer Space Telescope, and the Kepler Space Telescope, an international team including astronomers from the University of Cambridge found that HAT-P-11b is blanketed in water vapour, hydrogen gas, and other yet-to-be-identified molecules. The results are published today (24 September) in the online version of the journal Nature.

“This discovery is milepost on the road to eventually searching for molecules in the atmospheres of smaller, rocky planets more like Earth,” said John Grunsfeld, assistant administrator of NASA’s Science Mission Directorate. “Such achievements are only possible when we combine the capabilities of these unique and powerful observatories.”

Clouds in the atmospheres of planets can block the view to underlying molecules that reveal information about the planets’ compositions and histories. Finding clear skies on a Neptune-size planet is a good sign that smaller planets might have similarly good visibility.

“When astronomers go observing at night with telescopes, they say ‘clear skies’ to mean good luck,” said Jonathan Fraine of the University of Maryland, the study’s lead author. “In this case, we found clear skies on a distant planet. That's lucky for us because it means clouds didn't block our view of water molecules.”

HAT-P-11b is a so-called exo-Neptune — a Neptune-sized planet that orbits another star. It is located 120 light-years away in the constellation of Cygnus (The Swan). Unlike Neptune, this planet orbits closer to its star, making one lap roughly every five days. It is a warm world thought to have a rocky core, a mantle of fluid and ice, and a thick gaseous atmosphere. Not much else was known about the composition of the planet, or other exo-Neptunes like it, until now.

Part of the challenge in analysing the atmospheres of planets like this is their size. Larger Jupiter-like planets are easier to observe and researchers have already been able to detect water vapour in the atmospheres of some of these giant planets. Smaller planets are more difficult to probe — and all the smaller ones observed to date have appeared to be cloudy.

The team used Hubble’s Wide Field Camera 3 and a technique called transmission spectroscopy, in which a planet is observed as it crosses in front of its parent star. Starlight filters through the rim of the planet’s atmosphere and into a telescope. If molecules like water vapour are present, they absorb some of the starlight, leaving distinct signatures in the light that reaches our telescopes.

“We set out to look at the atmosphere of HAT-P-11b without knowing if its weather would be cloudy or not,” said Dr Nikku Madhusudhan, from Cambridge’s Institute of Astronomy, who was part of the study team. “By using transmission spectroscopy, we could use Hubble to detect water vapour in the planet. This told us that the planet didn’t have thick clouds blocking the view and is a very hopeful sign that we can find and analyse more cloudless, smaller, planets in the future. It is ground-breaking!”

Before the team could celebrate they had to be sure that the water vapour was from the planet and not from cool starspots — “freckles” on the face of stars — on the parent star. Luckily, Kepler had been observing the patch of sky in which HAT-P-11b happens to lie for years. Those visible-light data were combined with targeted infrared Spitzer observations. By comparing the datasets the astronomers could confirm that the starspots were too hot to contain any water vapour, and so it must belong to the planet.

The results from all three telescopes demonstrate that HAT-P-11b is blanketed in water vapour, hydrogen gas, and other yet-to-be-identified molecules. So in fact it is not only the smallest planet to have water vapour found in its atmosphere but is also the smallest planet for which molecules of any kind have been directly detected using spectroscopy. Theorists will be drawing up new models to explain the planet’s makeup and origins.

Although HAT-P-11b is dubbed as an exo-Neptune it is actually quite unlike any planet in our Solar System. It is thought that exo-Neptunes may have diverse compositions that reflect their formation histories. New findings such as this can help astronomers to piece together a theory for the origin of these distant worlds.

“We are working our way down the line, from hot Jupiters to exo-Neptunes,” said Drake Deming, a co-author of the study also from University of Maryland. “We want to expand our knowledge to a diverse range of exoplanets.”

The astronomers plan to examine more exo-Neptunes in the future, and hope to apply the same method to smaller super-Earths — massive, rocky cousins to our home world with up to ten times the mass of Earth. Our solar system does not contain a super-Earth, but NASA’s Kepler mission is finding them around other stars in droves, and the NASA/ESA James Webb Space Telescope, scheduled to launch in 2018, will search super-Earths for signs of water vapour and other molecules. However, finding signs of oceans and potentially habitable worlds is likely a way off.

This work is important for future studies of super-Earths and even smaller planets. It could allow astronomers to pick out in advance the planets with atmospheres clear enough for molecules to be detected. Once again, astronomers will be crossing their fingers for clear skies.

Smallest exoplanet ever found to have water vapour

This is a very hopeful sign that we can find and analyse more cloudless, smaller, planets in the futureNikku MadhusudhanNASA/JPL-CaltechIllustration of the view from HAT-P-11b

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NASA Telescopes Find Clear Skies and Water Vapor on Exoplanet

Astronomy News - 24 September 2014 - 5:00pm
Astronomers using data from three of NASA's space telescopes -- Hubble, Spitzer and Kepler -- have discovered clear skies and steamy water vapor on a gaseous planet outside our solar system. The planet is about the size of Neptune, making it the smallest planet from which molecules of any kind have been detected.

Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet

Astronomy News - 24 September 2014 - 1:00am

Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet

Nature 513, 7519 (2014). doi:10.1038/nature13785

Authors: Jonathan Fraine, Drake Deming, Bjorn Benneke, Heather Knutson, Andrés Jordán, Néstor Espinoza, Nikku Madhusudhan, Ashlee Wilkins & Kamen Todorov

Transmission spectroscopy has so far detected atomic and molecular absorption in Jupiter-sized exoplanets, but intense efforts to measure molecular absorption in the atmospheres of smaller (Neptune-sized) planets during transits have revealed only featureless spectra. From this it was concluded that the majority of small, warm planets evolve to sustain atmospheres with high mean molecular weights (little hydrogen), opaque clouds or scattering hazes, reducing our ability to observe the composition of these atmospheres. Here we report observations of the transmission spectrum of the exoplanet HAT-P-11b (which has a radius about four times that of Earth) from the optical wavelength range to the infrared. We detected water vapour absorption at a wavelength of 1.4 micrometres. The amplitude of the water absorption (approximately 250 parts per million) indicates that the planetary atmosphere is predominantly clear down to an altitude corresponding to about 1 millibar, and sufficiently rich in hydrogen to have a large scale height (over which the atmospheric pressure varies by a factor of e). The spectrum is indicative of a planetary atmosphere in which the abundance of heavy elements is no greater than about 700 times the solar value. This is in good agreement with the core-accretion theory of planet formation, in which a gas giant planet acquires its atmosphere by accreting hydrogen-rich gas directly from the protoplanetary nebula onto a large rocky or icy core.

Extrasolar planets: Window on a watery world

Astronomy News - 24 September 2014 - 1:00am

Extrasolar planets: Window on a watery world

Nature 513, 7519 (2014). doi:10.1038/513493a

Authors: Eliza M. R. Kempton

The first definitive signs of water have been seen in the atmosphere of a Neptune-sized exoplanet, paving the way towards the search for water on smaller Earth-like planets. See Letter p.526

VIDEO: Brian Cox: 'Multiverse' makes sense

Astronomy News - 23 September 2014 - 3:31pm
The presenter and physicist Brian Cox says he supports the idea that many universes can exist at the same time.

AUDIO: Space inflation and a physics bet

Astronomy News - 23 September 2014 - 1:45pm
One of the biggest scientific claims of the year has received another set-back, putting the result of a bet between two significant physicists in jeopardy.

Ripples from dawn of creation vanish in a puff of dust

Astronomy News - 22 September 2014 - 4:00pm
We thought the BICEP2 telescope had seen gravitational waves from the universe's creation, but the Planck spacecraft suggests cosmic dust was the source






Cosmic study 'underestimated' dust

Astronomy News - 22 September 2014 - 9:04am
Scientists who claimed to have found evidence for a cosmic super-expansion just after the Big Bang underestimated a key confounding factor in their research, according to a new analysis.

NASA’s Newest Mars Mission Spacecraft Enters Orbit around Red Planet

Astronomy News - 21 September 2014 - 5:00pm
NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft successfully entered Mars’ orbit at 10:24 p.m. EDT Sunday, Sept. 21, where it now will prepare to study the Red Planet’s upper atmosphere as never done before. MAVEN is the first spacecraft dedicated to exploring the tenuous upper atmosphere of Mars.

Milky Way map swirls with 219 million stars

Astronomy News - 19 September 2014 - 5:19pm
The most detailed map of our galaxy ever made reveals the incomprehensible majesty of our neighbourhood






Strangest star: 6 things we didn't know about the sun

Astronomy News - 18 September 2014 - 8:00pm
With its fiery rains, speedy magnetic flips and an atmosphere that defies the laws of physics – our home star is as weird as it gets (full text available to subscribers)






Astronomy Photographer of the Year 2014

Astronomy News - 18 September 2014 - 11:19am
Twinkling stars and swirling gases - winning visions of the night sky

Gaia discovers its first supernova

Astronomy News - 18 September 2014 - 11:16am

While scanning the sky to measure the positions and movements of stars in our Galaxy, Gaia has discovered its first stellar explosion in another galaxy far, far away.

This powerful event, now named Gaia14aaa, took place in a distant galaxy some 500 million light-years away, and was revealed via a sudden rise in the galaxy’s brightness between two Gaia observations separated by one month.

Gaia, which began its scientific work on 25 July, repeatedly scans the entire sky, so that each of the roughly one billion stars in the final catalogue will be examined an average of 70 times over the next five years.

“This kind of repeated survey comes in handy for studying the changeable nature of the sky,” comments Simon Hodgkin from the Institute of Astronomy in Cambridge, UK.

Many astronomical sources are variable: some exhibit a regular pattern, with a periodically rising and declining brightness, while others may undergo sudden and dramatic changes.

Light curve

“As Gaia goes back to each patch of the sky over and over, we have a chance to spot thousands of ‘guest stars’ on the celestial tapestry,” notes Dr Hodgkin. “These transient sources can be signposts to some of the most powerful phenomena in the Universe, like this supernova.”

Dr Hodgkin is part of Gaia’s Science Alert Team, which includes astronomers from the Universities of Cambridge, UK, and Warsaw, Poland, who are combing through the scans in search of unexpected changes.

It did not take long until they found the first ‘anomaly’ in the form of a sudden spike in the light coming from a distant galaxy, detected on 30 August. The same galaxy appeared much dimmer when Gaia first looked at it just a month before.

“We immediately thought it might be a supernova, but needed more clues to back up our claim,” explains Łukasz Wyrzykowski from the Warsaw University Astronomical Observatory, Poland.

Other powerful cosmic events may resemble a supernova in a distant galaxy, such as outbursts caused by the mass-devouring supermassive black hole at the galaxy centre.

Supernova Gaia14aaa and its host galaxy

However, in Gaia14aaa, the position of the bright spot of light was slightly offset from the galaxy’s core, suggesting that it was unlikely to be related to a central black hole.

So, the astronomers looked for more information in the light of this new source. Besides recording the position and brightness of stars and galaxies, Gaia also splits their light to create a spectrum. In fact, Gaia uses two prisms spanning red and blue wavelength regions to produce a low-resolution spectrum that allows astronomers to seek signatures of the various chemical elements present in the source of that light.

Read the full story on Gaia's first supernova discovery on the ESA Portal.

VIDEO: Astronomy Photographer of the Year 2014

Astronomy News - 18 September 2014 - 8:41am
Twinkling stars and swirling gases - winning visions of the night sky

Rainbow galaxies reveal why cosmos is full of spirals

Astronomy News - 17 September 2014 - 7:30pm
Psychedelic pictures of 30 galactic collisions show for the first time that merging galaxies often spawn disc-shaped offspring like our Milky Way






Hubble Helps Find Smallest Known Galaxy with a Supermassive Black Hole

Astronomy News - 17 September 2014 - 6:00pm

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Astronomers have found an unlikely object in an improbable place: a monster black hole lurking inside one of the tiniest galaxies known. The dwarf galaxy containing the black hole is the densest galaxy ever seen, cramming 140 million stars within a diameter of about 300 light-years (just 1/500th of our Milky Way galaxy's diameter). However, the black hole inside the galaxy is five times the mass of the black hole at the center of our Milky Way. This suggests that the dwarf galaxy may actually be the stripped remnant of a larger galaxy that was torn apart during a close encounter with a more massive galaxy. The finding implies that there are many other compact galaxies in the universe that contain supermassive black holes.

Big surprises can come in small packages - Hubble helps astronomers find smallest known galaxy with supermassive black hole [heic1419]

Astronomy News - 17 September 2014 - 6:00pm
Astronomers using the NASA/ESA Hubble Space Telescope have found a monster lurking in a very unlikely place. New observations of the ultracompact dwarf galaxy M60-UCD1 have revealed a supermassive black hole at its heart, making this tiny galaxy the smallest ever found to host a supermassive black hole. This suggests that there may be many more supermassive black holes that we have missed, and tells us more about the formation of these incredibly dense galaxies. The results will be published in the journal Nature on 18 September 2014.

Hubble Helps Find Smallest Known Galaxy Containing a Supermassive Black Hole

Astronomy News - 17 September 2014 - 5:00pm
Astronomers using data from NASA’s Hubble Space Telescope and ground observation have found an unlikely object in an improbable place -- a monster black hole lurking inside one of the tiniest galaxies ever known.