Astronomers thrilled by extreme storms on Uranus

These are infrared images of Uranus (1.6 and 2.2 microns) obtained on Aug. 6, 2014, with adaptive optics on the 10-meter Keck telescope. 

The white spot is an extremely large storm that was brighter than any feature ever recorded on the planet in the 2.2 micron band. 

The cloud rotating into view at the lower-right limb grew into the large storm that was seen by amateur astronomers at visible wavelengths. 

Credit: Imke de Pater (UC Berkeley) & Keck Observatory images.

The normally bland face of Uranus has become increasingly stormy, with enormous cloud systems so bright that for the first time ever, amateur astronomers are able to see details in the planet's hazy blue-green atmosphere.

Imke de Pater

"The weather on Uranus is incredibly active," said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and leader of the team that first noticed the activity when observing the planet with adaptive optics on the W. M. Keck II Telescope in Hawaii.

"This type of activity would have been expected in 2007, when Uranus's once every 42-year equinox occurred and the sun shined directly on the equator," noted co-investigator Heidi Hammel of the Association of Universities for Research in Astronomy.

"But we predicted that such activity would have died down by now. Why we see these incredible storms now is beyond anybody's guess."

Heidi Hammel

In all, de Pater, Hammel and their team detected eight large storms on Uranus's northern hemisphere when observing the planet with the Keck Telescope on August 5 and 6.

One was the brightest storm ever seen on Uranus at 2.2 microns, a wavelength that senses clouds just below the tropopause, where the pressure ranges from about 300 to 500 mbar, or half the pressure at Earth's surface.

The storm accounted for 30 percent of all light reflected by the rest of the planet at this wavelength.

When amateur astronomers heard about the activity, they turned their telescopes on the planet and were amazed to see a bright blotch on the surface of a normally boring blue dot.

'I got it!'

French amateur astronomer Marc Delcroix processed the amateur images and confirmed the discovery of a bright spot on an image by French amateur Régis De-Bénedictis, then in others taken by fellow amateurs in September and October.

He had his own chance on Oct. 3 and 4 to photograph it with the Pic du Midi one-meter telescope, where on the second night, "I caught the feature when it was transiting, and I thought, 'Yes, I got it!'" said Delcroix.

"I was thrilled to see such activity on Uranus. Getting details on Mars, Jupiter or Saturn is now routine, but seeing details on Uranus and Neptune are the new frontiers for us amateurs and I did not want to miss that," said Delcroix, who works for an auto parts supplier in Toulouse and has been observing the skies, Jupiter in particular, with his backyard telescope since 2006 and, since 2012, occasionally with the Pic du Midi telescope.

"I was so happy to confirm myself these first amateur images on this bright storm on Uranus, feeling I was living a very special moment for planetary amateur astronomy."

These are optical images of Uranus on Sept. 19 and Oct. 2, showing the dramatic appearance of a bright storm on a planet that normally displays only a diffuse bright polar region. 

Credit: Photo by Anthony Wesley, Murrumbateman, Australia.

Interestingly, the extremely bright storm seen by Keck in the near infrared is not the one seen by the amateurs, which is much deeper in the atmosphere than the one that initially caused all the excitement. De Pater's colleague Larry Sromovsky, a planetary scientist at the University of Wisconsin, Madison, identified the amateur spot as one of the few features on the Keck images from August 5 that was only seen at 1.6 microns, and not at 2.2 microns.

The 1.6 micron light is emitted from deeper in the atmosphere, which means that this feature is below the uppermost cloud layer of methane-ice in Uranus's atmosphere.

"The colours and morphology of this cloud complex suggests that the storm may be tied to a vortex in the deeper atmosphere similar to two large cloud complexes seen during the equinox," Sromovsky said.

Such vortices could be anchored much deeper in the atmosphere and extend over large vertical distances, as inferred from similar vortices on Jupiter, including its Great Red Spot.

An expanded team of astronomers led by Kunio M. Sayanagi, an Assistant Professor at Hampton University in Virginia, leveraged the amateur observations to activate a "Target of Opportunity" proposal on the Hubble Space Telescope, which imaged the entire planet on Oct. 14.

Observing at a variety of wavelengths, HST revealed multiple storm components extending over a distance of more than 9,000 kilometers (5,760 miles) and clouds at a variety of altitudes.

De Pater, Sromovsky, Hammel and Pat Fry of the University of Wisconsin will report the details of their observations on Nov. 12 at a meeting of the American Astronomical Society's Division of Planetary Sciences in Tucson, Ariz.

Ice giant

This is an animation showing the movement of the bright spot as Uranus rotated over a two hour period on Oct. 4, 2014. 

The infrared images were taken at the Pic du Midi telescope in the French Pyrénées. 

Credit: Marc Delcroix and F. Colas (S2P).

Uranus is an ice giant, about four times the diameter of Earth, with an atmosphere of hydrogen and helium, with just a bit of methane to give it a blue tint.

Because it is so distant, 30 times farther from the sun than Earth, astronomers were able to see little detail on its surface until adaptive optics on the Keck telescopes revealed features much like those on Jupiter.

De Pater and her colleagues have been following Uranus for more than a decade, charting the weather on the planet, including bands of circulating clouds, massive swirling storms and convective features at its north pole.

Bright clouds are probably caused by gases such as methane rising in the atmosphere and condensing into highly reflective clouds of methane ice.

Because Uranus has no internal source of heat, its atmospheric activity was thought to be driven solely by sunlight, which is now weak in the northern hemisphere. Hence astronomers were surprised when these observations showed such intense activity.

Observations taken with the Keck telescope by Christoph Baranec, an Assistant Professor at the University of Hawaii on Manoa, revealed that the storm was still active, but had a different morphology and possibly reduced intensity.

"If indeed these features are high-altitude clouds generated by flow perturbations associated with a deeper vortex system, such drastic fluctuations in intensity would indeed be possible," Sromovsky added.

"These unexpected observations remind us keenly of how little we understand about atmospheric dynamics in outer planet atmospheres," the authors wrote in their paper.

Exoplanet measured with remarkable precision

Barely 30 years ago, the only planets astronomers had found were located right here in our own solar system.

The Milky Way is chock-full of stars, millions of them similar to our own sun. Yet the tally of known worlds in other star systems was exactly zero.

What a difference a few decades can make.

As 2014 unfolds, astronomers have not only found more than a thousand "exoplanets" circling distant suns, but also they're beginning to make precise measurements of them.

The old void of ignorance about exoplanets is now being filled with data precise to the second decimal place.

A team led by Sarah Ballard, a NASA Carl Sagan Fellow at the University of Washington in Seattle, recently measured the diameter of a "super Earth" to within an accuracy of 148 miles total or about 1 percent, remarkable accuracy for an exoplanet located about 300 light years from Earth.

"It does indeed seem amazing," says Ballard. "The landscape of exoplanet research has changed to an almost unrecognizable degree since I started graduate school in 2007."

To size up the planet, named "Kepler 93 b," Ballard used data from NASA's Kepler and Spitzer Space Telescopes.

First, Kepler discovered the planet. As seen from Earth, Kepler 93 b passes directly in front of its parent star, causing the starlight to dim during the transit.

That dimming, which occurs once per orbit, is what allowed Kepler mission scientists to find the planet in the first place.

Kepler Space Telescope

Next, both Spitzer and Kepler Space Telescope recorded multiple transits at visible and infrared wavelengths.

Data from the observatories agreed: Kepler 93 b was really a planet and not some artefact of stellar variability.

Ballard then knew that by looking carefully at the light curve she could calculate the size of the planet relative to the star.

At that point, the only missing piece was the diameter of the star itself.

"The precision with which we measured the size of the planet is linked directly to our measurement of the star," says Ballard. "And we measured the star using a technique called astero-seismology."

Most people have heard of "seismology," the study of seismic waves moving through the Earth. "We can learn a lot about the structure of our planet by studying seismic waves," she says.

Asteroseismology is the same thing, except for stars: The outer layers of stars boil like water on top of a hot stove. Those convective motions create seismic waves that bounce around inside the core, causing the star to ring like an enormous bell. Kepler can detect that "ringing," which reveals itself as fluctuations in a star's brightness.

Ballard's colleague, University of Birmingham professor Bill Chaplin led the asteroseismic analysis for Kepler-93 b.

"By analyzing the seismic modes of the star, he was able to deduce its radius and mass to an accuracy of a percent," she says.

The new measurements confirm that Kepler-93 b is a "super-Earth" sized exoplanet, with a diameter about one-and-a-half times the size of our planet.

Previous measurements by the Keck Observatory in Hawaii had put Kepler-93 b's mass at about 3.8 times that of Earth.

The density of Kepler-93 b, derived from its mass and newly obtained radius, suggests the planet is very likely made of iron and rock, like Earth itself.

Although super-Earths are common in the galaxy, none exist in our solar system. That makes them tricky to study.

Ballard's team has shown, however, that it is possible to learn a lot about an exoplanet even when it is very far away.

NASA seeks Kuiper Belt Objects for New Horizon's post-Pluto mission

An artist’s conception of a KBO encounter by New Horizons. 

Credit: JHUAPL/SwRI.

Are you ready for the summer of 2015? A showdown of epic proportions is in the making, as NASA's New Horizons spacecraft is set to pass within 12,500 kilometres of Pluto, roughly a third of the distance of the ring of geosynchronous satellites orbiting the Earth, a little over a year from now on July 14th, 2015.

But another question is already being raised, one that's assuming center stage even before we explore Pluto and its retinue of moons: will New Horizons have another target available to study for its post-Pluto encounter out in the Kuiper Belt?

Researchers say time is of the essence to find it.

To be sure, it's a big solar system out there, and it's not that researchers haven't been looking.

New Horizons was launched from Cape Canaveral Air Force Station on January 19th, 2006 atop an Atlas V rocket flying in a 551 configuration in one of the fastest departures from Earth ever: it took New Horizons just nine hours to pass Earth's moon after launch.

The idea has always been out there to send New Horizons onward to explore and object beyond Pluto in the Kuiper Belt, but thus far, searches for a potential target have turned up naught.

A recent joint statement from NASA's Small Bodies and Outer Planets Assessment Groups (SBAG and OPAG) has emphasized the scientific priority needed for identifying a possible Kuiper Belt Object (KBO) for the New Horizons mission post-Pluto encounter.

The assessment notes that such a chance to check out a KBO up close may only come once in our lifetimes: even though it's currently moving at a heliocentric velocity of just under 15 kilometres a second, it will have taken New Horizons almost a decade to traverse the 32 A.U. distance to Pluto.

The report also highlights the fact that KBOs are expected to dynamically different from Pluto as well and worthy of study.

The statement also notes that the window may be closing to find such a favourable target after 2014, as the upcoming observational apparition of Pluto as seen from Earth, and the direction New Horizons is headed afterwards, reaches opposition this summer on July 4th.

But time is of the essence, as it will allow researchers to plan for a burn and trajectory change for New Horizons shortly after its encounter with Pluto and Charon using what little fuel it has left.

Then there's the issue of debris in the Pluto system that may require fine-tuning its trajectory pre-encounter as well.

New Horizons will begin long range operations later this year in November, switching on permanently for two years of operations pre-, during and post- encounter with Pluto.

New Horizons spends its last days on Earth pre-encapsulation. Credit: NASA/KSC

And there currently isn't a short-list of "next best thing" targets for New Horizons post-Pluto encounter.

One object, dubbed VNH0004, may be available for distant observations in January of next year, but even this object will only pass 75 million kilometres, about 0.5 A.U. from New Horizons at its closest.

Ground based assets such as the Keck, Subaru and Gemini observatories have been repeatedly employed in the search over the past three years.

The best hopes lie with the Hubble Space Telescope, which can go deeper and spy fainter targets.

Nor could New Horizons carry out a search for new targets on its own. Its eight inch (20 cm in diameter) LORRI instrument has a limiting magnitude of about +18, which is not even close to what would be required for such a discovery.

New Horizons currently has 130 metres/sec of hydrazine fuel available to send it onwards to a possible KBO encounter, limiting its range and maneuverability into a narrow cone straight ahead of the spacecraft.

This restricts the parameters for a potential encounter to 0.35 A.U. off of its nominal path for a target candidate be to still be viable objective.

New Horizons will exit the Kuiper Belt at around 55 A.U. from the Sun, and will probably end its days joining the Voyager missions probing the outer solar system environment.

Like Pioneers 10 and 11, Voyagers 1 and 2 and the upper stage boosters that deployed them, New Horizons will escape our solar system and orbit the Milky Way galaxy for millions of years.

We recently proposed a fun thought experiment concerning just how much extraterrestrial "space junk" might be out there, littering the galactic disk.

Keck: Studying photosynthesis, from outer space

This is an illustration of the process of measuring photosynthesis from space, courtesy of the Keck Institute for Space Studies. 

Credit: Keck Institute for Space Studies

Plants convert energy from sunlight into chemical energy during a process called photosynthesis.

This energy is passed on to humans and animals that eat the plants, and thus photosynthesis is the primary source of energy for all life on Earth.

But the photosynthetic activity of various regions is changing due to human interaction with the environment, including climate change, which makes large-scale studies of photosynthetic activity of interest.

New research from a team including Carnegie's Joe Berry reveals a fundamentally new approach for measuring photosynthetic activity as it occurs around the planet.

It is published this week by Proceedings of the National Academy of Sciences.

Their work is based on a breakthrough in the capacity to use satellite technology to measure light that is emitted by plant leaves as a byproduct of photosynthesis.

This light is called fluorescence and it is produced when sunlight excites the photosynthetic pigment chloropyll.

The method offers a direct measurement of activity occurring as the satellite passes overhead. Other approaches to detecting photosynthetic activity on a large scale are less direct, so until now, models have been the primary tool for estimating photosynthetic productivity on a planetary scale. The accuracy of these models has been difficult to evaluate.

"This new method uses satellites to sense fluorescence emitted during photosynthesis," Berry said. "It changes everything. It gives us a direct observation of photosynthesis on a large scale for the first time ever."

The team's paper reports on observations of fluorescence from large areas of crops in the Midwestern Corn Belt. The data show that the previous model-based estimates of photosynthesis are too low.

What's more, these studies provide a new-and-improved tool to evaluate the comparative productivity of the breadbaskets of the world, such as the Indo-Gangetic Plain and Eastern China.

The relationship between fluorescence measured from space and gross primary production measured in the Corn Belt also provides a way for researchers to assess in near real-time the production of other, non-agricultural areas of the world, including vast expanses of uncultivated forests and grasslands.

More information: Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence, www.pnas.org/cgi/doi/10.1073/pnas.1320008111

Keck Observatory's NIRSPEC: Water vapour detected in the atmosphere of a hot Jupiter

Simulated data showing the method used for detecting water vapor features detected around the hot Jupiter tau Boo b. 

In this example, the planetary signal has been increased in strength relative by several orders of magnitude relative to the actual signal. 

The dotted lines show the blue- and red-shifts of the planetary and stellar lines in the data, respectively, due to the orbital motion of two bodies in the system. 

Credit: Alexandra Lockwood (CalTech), Background Image David Aguilar (CFA).

California Institute of Technology (Caltech) astronomers using data gathered at the W. M. Keck Observatory have developed a new technique for planetary scientists that could provide insight into how many water planets like Earth exist within our universe.

The results have been published on February 24th by Astrophysical Letters.

Alexandra Lockwood

Scientists have detected water vapour on other planets in the past, but these detections could only take place under very specific circumstances, according to graduate student Alexandra Lockwood, the first author of the study.

"When a planet transits, or passes in orbit, in front of its host star, we can use information from this event to detect water vapour and other atmospheric compounds."

"Alternatively, if the planet is sufficiently far away from its host star, we can also learn about a planet's atmosphere by imaging it."

However, a significant portion of the population of extrasolar planets does not fit either of these criteria and there wasn't really a way to find information about the atmospheres of these planets.

Geoffrey Blake

Looking to resolve this problem, Lockwood and her advisor Geoffrey Blake, Caltech professor of cosmochemistry, planetary sciences and chemistry, were inspired by the recent detection of carbon monoxide in the extrasolar planet, 'Tau Boo b' and they wondered if they could detect water in a similar manner.

The method used to detect carbon monoxide utilized the radial velocity (RV) technique, a technique commonly used in the visible region of the spectrum, to which our eyes are sensitive, for discovering non-transiting exoplanets.

Using the Doppler effect, RV detection traditionally determines the motion of a star due to the gravitational pull of a companion planet; the star moves opposite that of the orbital motion of the planet, and stellar features shift in wavelength. A large planet or a planet closer to its host star provides a larger shift.

An artistic impression of extrasolar planet, 'Tau Boo b' 

The team used the carbon monoxide study as a guide to expand the RV technique into the infrared to determine the orbit of extrasolar planet, 'Tau Boo b' around its star, and added further analysis of the light shifts via spectroscopy, an analysis of the light's spectrum.

Since every molecule emits a different wavelength of light, this unique light signature allows the researchers to analyze molecules that comprise the planet's atmosphere.

Using data of extrasolar planet, 'Tau Boo b' collected with the Near Infrared Echelle Spectrograph (NIRSPEC) instrument at the W. M. Keck Observatory in Hawai'i, the researchers were able to compare the molecular signature of water to the light spectrum emitted by the planet, confirming that the atmosphere did indeed include water vapour.

"The readout we get from Keck Observatory's NIRSPEC is like listening to an orchestra performance; you hear all of the music together, but if you listen carefully, you can pick out a trumpet or a violin or a cello, and you know that those instruments are present," Lockwood said.

"The instrument allows you to pick out different pieces; like this wavelength of light means that there is sodium, or this one means that there's water."

More information: "Near-IR Direct Detection of Water Vapour in Tau Boo b." Alexandra C. Lockwood, John A. Johnson, Chad F. Bender, John S. Carr, Travis Barman, Alexander J.W. Richert, Geoffrey A. Blake. arXiv:1402.0846 [astro-ph.EP].