New Research Reveals Fluctuating Atmosphere of Jupiter’s Volcanic Moon

Jupiter’s volcanic moon Io has a thin atmosphere that collapses in the shadow of Jupiter, condensing as ice, according to a new study by NASA-funded researchers. The study reveals the freezing effects of Jupiter’s shadow during daily eclipses on the moon’s volcanic gases.

“This research is the first time scientists have observed this remarkable phenomenon directly, improving our understanding of this geologically active moon,” said Constantine Tsang, a scientist at the Southwest Research Institute in Boulder, Colorado. The study was published Aug. 2 in the Journal of Geophysical Research.

Io is the most volcanically active object in the solar system. The volcanoes are caused by tidal heating, the result of gravitational forces from Jupiter and other moons. These forces result in geological activity, most notably volcanoes that emit umbrella-like plumes of sulfur dioxide gas that can extend up to 300 miles (480 kilometers) above Io and produce extensive basaltic lava fields that can flow for hundreds of miles.

The new study documents atmospheric changes on Io as the giant planet casts its shadow over the moon’s surface during daily eclipses. Io’s thin atmosphere, which consists primarily of sulfur dioxide (SO2) gas emitted from volcanoes, collapses as the SO2 freezes onto the surface as ice when Io is shaded by Jupiter, then is restored when the ice warms and sublimes (i.e. transforms from solid back to gas) when the moon moves out of eclipse back into sunlight.

The study used the large eight-meter Gemini North telescope in Hawaii and an instrument called the Texas Echelon Cross Echelle Spectrograph (TEXES). Data showed that Io’s atmosphere begins to “deflate” when the temperatures drop from -235 degrees Fahrenheit in sunlight to -270 degrees Fahrenheit during eclipse. Eclipse occurs two hours of every Io day (1.7 Earth days). In full eclipse, the atmosphere effectively collapses, as most of the sulfur dioxide gas settles as frost on the moon’s surface. The atmosphere redevelops as the surface warms once the moon returns to full sunlight.

Artist’s concept of the atmospheric collapse of Jupiter’s volcanic moon Io, which is eclipsed by Jupiter for two hours of each day (1.7 Earth days). The resulting temperature drop freezes sulfur dioxide gas, causing the atmosphere to “deflate,” as seen in the shadowed area on the left.

Credits: SwRI/Andrew Blanchard

“This confirms that Io’s atmosphere is in a constant state of collapse and repair, and shows that a large fraction of the atmosphere is supported by sublimation of SO2 ice,” said John Spencer, a co-author of the new study, also at the Southwest Research Institute. “Though Io’s hyperactive volcanoes are the ultimate source of the SO2, sunlight controls the atmospheric pressure on a daily basis by controlling the temperature of the ice on the surface.  We’ve long suspected this, but can finally watch it happen.”

Prior to the study, no direct observations of Io’s atmosphere in eclipse had been possible because Io’s atmosphere is difficult to observe in the darkness of Jupiter’s shadow.  This breakthrough was possible because TEXES measures the atmosphere using heat radiation, not sunlight, and the giant Gemini telescope can sense the faint heat signature of Io’s collapsing atmosphere.

The observations occurred over two nights in November 2013, when Io was more than 420 million miles (675 million kilometers) from Earth. On both occasions, Io was observed moving into Jupiter’s shadow for a period about 40 minutes before and after the start of the eclipse.

The research was funded by NASA’s Solar System Workings and Solar System Observations programs.

'Frankenstein' Galaxy Surprises Astronomers

About 250 million light-years away, there's a neighborhood of our universe that astronomers had considered quiet and unremarkable. But now, scientists have uncovered an enormous, bizarre galaxy possibly formed from the parts of other galaxies.

A new study to be published in the Astrophysical Journal reveals the secret of UGC 1382, a galaxy that had originally been thought to be old, small and typical. Instead, scientists using data from NASA telescopes and other observatories have discovered that the galaxy is 10 times bigger than previously thought and, unlike most galaxies, its insides are younger than its outsides, almost as if it had been built using spare parts.

"This rare, 'Frankenstein' galaxy formed and is able to survive because it lies in a quiet little suburban neighborhood of the universe, where none of the hubbub of the more crowded parts can bother it," said study co-author Mark Seibert of the Observatories of the Carnegie Institution for Science, Pasadena, California. "It is so delicate that a slight nudge from a neighbor would cause it to disintegrate."

Seibert and Lea Hagen, a graduate student at Pennsylvania State University, University Park, came upon this galaxy by accident. They had been looking for stars forming in run-of-the-mill elliptical galaxies, which do not spin and are more three-dimensional and football-shaped than flat disks. Astronomers originally thought that UGC 1382 was one of those.

But while looking at images of galaxies in ultraviolet light through data from NASA's Galaxy Evolution Explorer (GALEX), a behemoth began to emerge from the darkness.

"We saw spiral arms extending far outside this galaxy, which no one had noticed before, and which elliptical galaxies should not have," said Hagen, who led the study. "That put us on an expedition to find out what this galaxy is and how it formed."

Researchers then looked at data of the galaxy from other telescopes: the Sloan Digital Sky Survey, the Two Micron All-Sky Survey (2MASS), NASA's Wide-field Infrared Survey Explorer (WISE), the National Radio Astronomy Observatory's Very Large Array and Carnegie's du Pont Telescope at Las Campanas Observatory. After GALEX revealed previously unseen structures to the astronomers, optical and infrared light observations from the other telescopes allowed the researchers to build a new model of this mysterious galaxy.

As it turns out, UGC 1382, at about 718,000 light-years across, is more than seven times wider than the Milky Way. It is also one of the three largest isolated disk galaxies ever discovered, according to the study. This galaxy is a rotating disk of low-density gas. Stars don't form here very quickly because the gas is so spread out.

But the biggest surprise was how the relative ages of the galaxy's components appear backwards. In most galaxies, the innermost portion forms first and contains the oldest stars. As the galaxy grows, its outer, newer regions have the youngest stars. Not so with UGC 1382. By combining observations from many different telescopes, astronomers were able to piece together the historical record of when stars formed in this galaxy -- and the result was bizarre.

"The center of UGC 1382 is actually younger than the spiral disk surrounding it," Seibert said. "It's old on the outside and young on the inside. This is like finding a tree whose inner growth rings are younger than the outer rings."

The unique galactic structure may have resulted from separate entities coming together, rather than a single entity that grew outward. In other words, two parts of the galaxy seem to have evolved independently before merging -- each with its own history.

At first, there was likely a group of small galaxies dominated by gas and dark matter, which is an invisible substance that makes up about 27 percent of all matter and energy in the universe (our own matter is only 5 percent). Later, a lenticular galaxy, a rotating disk without spiral arms, would have formed nearby. At least 3 billion years ago, the smaller galaxies may have fallen into orbit around the lenticular galaxy, eventually settling into the wide disk seen today.

More galaxies like this may exist, but more research is needed to look for them.

"By understanding this galaxy, we can get clues to how galaxies form on a larger scale, and uncover more galactic neighborhood surprises," Hagen said.

The GALEX mission, which ended in 2013 after more than a decade of scanning the skies in ultraviolet light, was led by scientists at Caltech in Pasadena, California. NASA's Jet Propulsion Laboratory, also in Pasadena, managed the mission and built the science instrument. Data for the 2MASS and WISE missions are archived at the Infrared Processing and Analysis Center (IPAC) at Caltech. JPL is managed by Caltech for NASA.

Light Echoes Used to Study Protoplanetary Disks

A new study published in the Astrophysical Journal uses data from NASA's Spitzer Space Telescope and four ground-based telescopes to determine the distance from a star to the inner rim of its surrounding protoplanetary disk. Researchers used a method called "photo-reverberation," also known as "light echoes." When the central star brightens, some of the light hits the surrounding disk, causing a delayed “echo.” Scientists measured the time it took for light coming directly from the star to reach Earth, then waited for its echo to arrive.

The Spitzer study marks the first time the light echo method was used in the context of protoplanetary disks.

This illustration shows a star surrounded by a protoplanetary disk. Material from the thick disk flows along the star’s magnetic field lines and is deposited onto the star’s surface. When material hits the star, it lights up brightly
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The Soyuz TMA-20M rocket launches from the Baikonur Cosmodrome in Kazakhstan

The Soyuz TMA-20M rocket launches from the Baikonur Cosmodrome in Kazakhstan on Saturday, March 19, 2016 (Friday, March 18, in the U.S.), carrying Expedition 47 Soyuz Commander Alexey Ovchinin of Roscosmos, Flight Engineer Jeff Williams of NASA, and Flight Engineer Oleg Skripochka of Roscosmos into orbit to begin their five and a half month mission on the International Space Station.

Credit: NASA/Aubrey Gemignani

W pattern in northern constellation Cassiopeia

A familiar, zigzag, W pattern in northern constellation Cassiopeia is traced by five bright stars in this colorful and broad mosaic. Stretching about 15 degrees across rich starfields, the celestial scene includes dark clouds, bright nebulae, and star clusters along the Milky Way. In yellow-orange hues Cassiopeia's alpha star Shedar is a standout though. The yellowish giant star is cooler than the Sun, over 40 times the solar diameter, and so luminous it shines brightly in Earth's night from 230 light-years away. A massive, rapidly rotating star at the center of the W, bright Gamma Cas is about 550 light-years distant. Bluish Gamma Cas is much hotter than the Sun. Its intense, invisible ultraviolet radiation ionizes hydrogen atoms in nearby interstellar clouds to produce visible red H-alpha emission as the atoms recombine with electrons. Of course, night skygazers in the Alpha Centauri star system would also see the recognizable outline traced by Cassiopeia's bright stars. But from their perspective a mere 4.3 light-years away they would see our Sun as a sixth bright star in Cassiopeia, extending the zigzag pattern just beyond the left edge of this frame.


The W in Cassiopeia
Image Credit & Copyright: Rogelio Bernal Andreo (Deep Sky Colors) 
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One Year Crew Back On Mother Earth

NASA astronaut and Expedition 46 Commander Scott Kelly and his Russian counterpart Mikhail Kornienko returned to Earth Tuesday after a historic 340-day mission aboard the International Space Station. They landed in Kazakhstan at 11:26 p.m. EST (10:26 a.m. March 2 Kazakhstan time).

Joining their return trip aboard a Soyuz TMA-18M spacecraft was Sergey Volkov, also of the Russian space agency Roscosmos, who arrived on the station Sept. 4, 2015. The crew touched down southeast of the remote town of Dzhezkazgan.

“Scott Kelly’s one-year mission aboard the International Space Station has helped to advance deep space exploration and America’s Journey to Mars,” said NASA Administrator Charles Bolden. “Scott has become the first American astronaut to spend a year in space, and in so doing, helped us take one giant leap toward putting boots on Mars.”

During the record-setting One-Year mission, the station crew conducted almost 400 investigations to advance NASA’s mission and benefit all of humanity. Kelly and Kornienko specifically participated in a number of studies to inform NASA’s Journey to Mars, including research into how the human body adjusts to weightlessness, isolation, radiation and the stress of long-duration spaceflight. Kelly’s identical twin brother, former NASA astronaut Mark Kelly, participated in parallel twin studies on Earth to help scientists compare the effects of space on the body and mind down to the cellular level.

One particular research project examined fluid shifts that occur when bodily fluids move into the upper body during weightlessness. These shifts may be associated with visual changes and a possible increase in intracranial pressure, which are significant challenges that must be understood before humans expand exploration beyond Earth’s orbit. The study uses the Russian Chibis device to draw fluids back into the legs while the subject’s eyes are measured to track any changes. NASA and Roscosmos already are looking at continuing the Fluid Shifts investigation with future space station crews.

The crew took advantage of the unique vantage point of the space station, with an orbital path that covers more than 90 percent of Earth’s population, to monitor and capture images of our planet. They also welcomed the arrival of a new instrument to study the signature of dark matter and conducted technology demonstrations that continue to drive innovation, including a test of network capabilities for operating swarms of spacecraft.

Kelly and Kornienko saw the arrival of six resupply spacecraft during their mission. Kelly was involved in the robotic capture of two NASA-contracted cargo flights -- SpaceX’s Dragon during the company’s sixth commercial resupply mission and Orbital ATK’s Cygnus during the company’s fourth commercial resupply mission. A Japanese cargo craft and three Russian resupply ships also delivered several tons of supplies to the station.

Kelly ventured outside the confines of the space station for three spacewalks during his mission. The first included a variety of station upgrade and maintenance tasks, including routing cables to prepare for new docking ports for U.S. commercial crew spacecraft. On a second spacewalk, he assisted in the successful reconfiguration of an ammonia cooling system and restoration of the station to full solar power-generating capability. The third spacewalk was to restore functionality to the station’s Mobile Transporter system.

Including crewmate Gennady Padalka, with whom Kelly and Kornienko launched on March 27, 2015, 10 astronauts and cosmonauts representing six different nations (the United States, Russia, Japan, Denmark, Kazakhstan and England) lived aboard the space station during the yearlong mission.

With the end of this mission, Kelly now has spent 520 days in space, the most among U.S. astronauts. Kornienko has accumulated 516 days across two flights, and Volkov has 548 days on three flights.

Expedition 47 continues operating the station, with NASA astronaut Tim Kopra in command. Kopra, Tim Peake of ESA (European Space Agency) and Yuri Malenchenko of Roscosmos will operate the station until the arrival of three new crew members in about two weeks. NASA astronaut Jeff Williams and Russian cosmonauts Alexey Ovchinin and Oleg Skripochka are scheduled to launch from Baikonur, Kazakhstan, on March 18.

The International Space Station is a convergence of science, technology and human innovation that enables us to demonstrate new technologies and make research breakthroughs not possible on Earth. It has been continuously occupied since November 2000 and, since then, has been visited by more than 200 people and a variety of international and commercial spacecraft. The space station remains the springboard to NASA's next giant leap in exploration, including future missions to an asteroid and Mars.

NASA’s IBEX Observations Pin Down Interstellar Magnetic Field

Immediately after its 2008 launch, NASA’s Interstellar Boundary Explorer, or IBEX, spotted a curiosity in a thin slice of space: More particles streamed in through a long, skinny swath in the sky than anywhere else. The origin of the so-called IBEX ribbon was unknown – but its very existence opened doors to observing what lies outside our solar system, the way drops of rain on a window tell you more about the weather outside.

Now, a new study uses IBEX data and simulations of the interstellar boundary – which lies at the very edge of the giant magnetic bubble surrounding our solar system called the heliosphere – to better describe space in our galactic neighborhood. The paper, published Feb. 8, 2016, in The Astrophysical Journal Letters, precisely determines the strength and direction of the magnetic field outside the heliosphere. Such information gives us a peek into the magnetic forces that dominate the galaxy beyond, teaching us more about our home in space.

(Artist concept) Far beyond the orbit of Neptune, the solar wind and the interstellar medium interact to create a region known as the inner heliosheath, bounded on the inside by the termination shock, and on the outside by the heliopause.

Credits: NASA/IBEX/Adler Planetarium

The new paper is based on one particular theory of the origin of the IBEX ribbon, in which the particles streaming in from the ribbon are actually solar material reflected back at us after a long journey to the edges of the sun’s magnetic boundaries. A giant bubble, known as the heliosphere, exists around the sun and is filled with what’s called solar wind, the sun’s constant outflow of ionized gas, known as plasma. When these particles reach the edges of the heliosphere, their motion becomes more complicated. 

“The theory says that some solar wind protons are sent flying back towards the sun as neutral atoms after a complex series of charge exchanges, creating the IBEX ribbon,” said Eric Zirnstein, a space scientist at the Southwest Research Institute in San Antonio, Texas, and lead author on the study. “Simulations and IBEX observations pinpoint this process – which takes anywhere from three to six years on average – as the most likely origin of the IBEX ribbon.”Outside the heliosphere lies the interstellar medium, with plasma that has different speed, density, and temperature than solar wind plasma, as well as neutral gases. These materials interact at the heliosphere’s edge to create a region known as the inner heliosheath, bounded on the inside by the termination shock – which is more than twice as far from us as the orbit of Pluto – and on the outside by the heliopause, the boundary between the solar wind and the comparatively dense interstellar medium.  

Some solar wind protons that flow out from the sun to this boundary region will gain an electron, making them neutral and allowing them to cross the heliopause. Once in the interstellar medium, they can lose that electron again, making them gyrate around the interstellar magnetic field. If those particles pick up another electron at the right place and time, they can be fired back into the heliosphere, travel all the way back toward Earth, and collide with IBEX’s detector. The particles carry information about all that interaction with the interstellar magnetic field, and as they  hit the detector they can give us unprecedented insight into the characteristics of that region of space.

“Only Voyager 1 has ever made direct observations of the interstellar magnetic field, and those are close to the heliopause, where it’s distorted,” said Zirnstein. “But this analysis provides a nice determination of its strength and direction farther out.”

The directions of different ribbon particles shooting back toward Earth are determined by the characteristics of the interstellar magnetic field. For instance, simulations show that the most energetic particles come from a different region of space than the least energetic particles, which gives clues as to how the interstellar magnetic field interacts with the heliosphere.

For the recent study, such observations were used to seed simulations of the ribbon’s origin. Not only do these simulations correctly predict the locations of neutral ribbon particles at different energies, but the deduced interstellar magnetic field agrees with Voyager 1 measurements, the deflection of interstellar neutral gases, and observations of distant polarized starlight.

However, some early simulations of the interstellar magnetic field don’t quite line up. Those pre-IBEX estimates were based largely on two data points – the distances at which Voyagers 1 and 2 crossed the termination shock.  

“Voyager 1 crossed the termination shock at 94 astronomical units, or AU, from the sun, and Voyager 2 at 84 AU,” said Zirnstein. One AU is equal to about 93 million miles, the average distance between Earth and the sun. “That difference of almost 930 million miles was mostly explained by a strong, very tilted interstellar magnetic field pushing on the heliosphere.” 

But that difference may be accounted for by considering a stronger influence from the solar cycle, which can lead to changes in the strength of the solar wind and thus change the distance to the termination shock in the directions of Voyager 1 and 2. The two Voyager spacecraft made their measurements almost three years apart, giving plenty of time for the variable solar wind to change the distance of the termination shock.

“Scientists in the field are developing more sophisticated models of the time-dependent solar wind,” said Zirnstein.

The simulations generally jibe well with the Voyager data.

The IBEX ribbon is a relatively narrow strip of particles flying in towards the sun from outside the heliosphere. A new study corroborates the idea that particles from outside the heliosphere that form the IBEX ribbon actually originate at the sun – and reveals information about the distant interstellar magnetic field.

Credits: SwRI

“The new findings can be used to better understand how our space environment interacts with the interstellar environment beyond the heliopause,” said Eric Christian, IBEX program scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in this study. “In turn, understanding that interaction could help explain the mystery of what causes the IBEX ribbon once and for all.”

The Southwest Research Institute leads IBEX with teams of national and international partners. NASA Goddard manages the Explorers Program for the agency’s Heliophysics Division within the Science Mission Directorate in Washington.

Courtesy of NASA

NASA's Spitzer, Hubble Find "Twins" of Superstar Eta Carinae in Other Galaxies

Eta Carinae, the most luminous and massive stellar system within 10,000 light-years, is best known for an enormous eruption seen in the mid-19th century that hurled at least 10 times the sun's mass into space. This expanding veil of gas and dust, which still shrouds Eta Carinae, makes it the only object of its kind known in our galaxy. Now a study using archival data from NASA's Spitzer and Hubble space telescopes has found five objects with similar properties in other galaxies for the first time.  

"The most massive stars are always rare, but they have tremendous impact on the chemical and physical evolution of their host galaxy," said lead scientist Rubab Khan, a postdoctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland. These stars produce and distribute large amounts of the chemical elements vital to life and eventually explode as supernovae.

Located about 7,500 light-years away in the southern constellation of Carina, Eta Carinae outshines our sun by 5 million times. The binary system consists of two massive stars in a tight 5.5-year orbit. Astronomers estimate that the more massive star has about 90 times the sun’s mass, while the smaller companion may exceed 30 solar masses.

As one of the nearest laboratories for studying high-mass stars, Eta Carinae has been a unique astronomical touchstone since its eruption in the 1840s. To understand why the eruption occurred and how it relates to the evolution of massive stars, astronomers needed additional examples. Catching rare stars during the short-lived aftermath of a major outburst approaches needle-and-haystack levels of difficulty, and nothing matching Eta Carinae had been found prior to Khan's study.

"We knew others were out there," said co-investigator Krzysztof Stanek, a professor of astronomy at Ohio State University in Columbus. "It was really a matter of figuring out what to look for and of being persistent."

Working with Scott Adams and Christopher Kochanek at Ohio State and George Sonneborn at Goddard, Khan developed a kind of optical and infrared fingerprint for identifying possible Eta Carinae twins, or "Eta twins" for short.

Dust forms in gas ejected by a massive star. This dust dims the star’s ultraviolet and visible light, but it absorbs and reradiates this energy as heat at longer mid-infrared wavelengths. "With Spitzer we see a steady increase in brightness starting at around 3 microns and peaking between 8 and 24 microns," explained Khan. "By comparing this emission to the dimming we see in Hubble's optical images, we could determine how much dust was present and compare it to the amount we see around Eta Carinae."

An initial survey of seven galaxies from 2012 to 2014 didn't turn up any Eta twins, underscoring their rarity. It did, however, identify a class of less massive and less luminous stars of scientific interest, demonstrating the search was sensitive enough to find Eta Carinae-like stars had they been present.


The nearby spiral galaxy M83 is currently the only one known to host two potential Eta Carinae twins. This composite of images from the Hubble Space Telescope's Wide Field Camera 3 instrument shows a galaxy ablaze with newly formed stars. A high rate of star formation increases the chances of finding massive stars that have recently undergone an Eta Carinae-like outburst. Bottom: Insets zoom into Hubble data to show the locations of M83's Eta twins.
Credits: NASA, ESA, the Hubble Heritage Team (STScI/AURA) and R. Khan (GSFC and ORAU)

In a follow-on survey in 2015, the team found two candidate Eta twins in the galaxy M83, located 15 million light-years away, and one each in NGC 6946, M101 and M51, located between 18 and 26 million light-years away. These five objects mimic the optical and infrared properties of Eta Carinae, indicating that each very likely contains a high mass star buried in five to 10 solar masses of gas and dust. Further study will let astronomers more precisely determine their physical properties. The findings were published in the Dec. 20 edition of The Astrophysical Journal Letters.
Researchers found likely Eta twins in four galaxies by comparing the infrared and optical brightness of each candidate source. Infrared images from NASA's Spitzer Space Telescope revealed the presence of warm dust surrounding the stars. Comparing this information with the brightness of each source at optical and near-infrared wavelengths as measured by instruments on Hubble, the team was able to identify candidate Eta Carinae-like objects. Top: 3.6-micron images of candidate Eta twins from Spitzer's IRAC instrument. Bottom: 800-nanometer images of the same sources from various Hubble instruments.
Credits: NASA, ESA, and R. Khan (GSFC and ORAU)

NASA's James Webb Space Telescope, set to launch in late 2018, carries an instrument ideally suited for further study of these stars. The Mid-Infrared Instrument (MIRI) has 10 times the angular resolution of instruments aboard Spitzer and is most sensitive at the wavelengths where Eta twins shine brightest. "Combined with Webb's larger primary mirror, MIRI will enable astronomers to better study these rare stellar laboratories and to find additional sources in this fascinating phase of stellar evolution," said Sonneborn, NASA's project scientist for Webb telescope operations. It will take Webb observations to confirm the Eta twins as true relatives of Eta Carinae.

The Spitzer Space Telescope is managed by NASA's Jet Propulsion Laboratory in Pasadena, California. The Spitzer Science Center at the California Institute of Technology in Pasadena conducts science operations.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

For more information about Spitzer, visit:

http://www.nasa.gov/spitzer

For more information about Hubble, visit:

http://www.nasa.gov/hubble

Courtesy of NASA, Goddard Space Flight Center