isuniverse

Pluto in False Color

Pluto is shown in false colors to help scientists differentiate between regions of different surface compositions and textures. The heart-shaped region on Pluto’s surface (seen in the photo) is unofficially named “Tombaugh Regio” in honor of the man who discovered the dwarf planet, Clyde Tombaugh. The heart of Tombaugh Regio is called “Sputnik Planum” as an homage to the first satellite to orbit the Earth – Sputnik. Within this heart of the heart, scientists have detected signs that the region contains different ices and may have even been geologically active in recent history.

In order to create this false-color global view of Pluto, four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with color data from the Ralph instrument. The images, taken when the spacecraft was 280,000 miles (450,000 kilometers) away, show features as small as 1.4 miles (2.2 kilometers).

Pluto continues to amaze. This is just the tip of the iceberg; we have 16 months of data still to come.

Image & Source Credit: NASA/JHUAPL/SwRI

Cosmic Detective Work

Supernovae are thought to be massive explosions signaling the end of a star’s life; however, stellar demise is not always the cause of these explosions. Supernovae explosions are not created equal and are divided into categories - the most common of which is a Type Ia. This class of supernova involves the detonation of small, dense, already dead stars called white dwarfs. 

New observations from NASA’s Spitzer Space Telescope have shed light on a new rare type of Type Ia supernova, involving a zombie star of sorts. The dead star (white dwarf) feeds off a neighboring aging star just like a zombie, until it has “eaten” so much material, it triggers an explosion. This new data shows just how exceptional these events are. Astronomers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland get to play detective and search through the stellar remains for any clue that will explain exactly what causes these powerful explosions. 

Supernovae provide cosmic fuel, spewing out all the elements necessary to the Universe - including heavy metals like the iron found in our blood. Typically Type Ia explosions are very consistent and astronomers use these explosions as distance markers and use them to study how the universe is expanding. 

Over the past ten years, researchers have been mounting evidence that Type Ia explosions occur when two white dwarfs collide - with only one exception - Kepler’s supernova. Named for the famous astronomer who witnessed it back in 1604, Kepler’s supernova is thought to be caused by one white dwarf and its elderly red giant companion. Scientists know the companion was a red giant based on the white dwarf remnant sitting among the gas pool and dust shed by the aging star.

These new observations show that Spitzer has now observed a second explosion just like Kepler’s supernova, dubbed N103B. Located approximately 160,000 light-years away in our galactic neighbor, the Large Magellanic Cloud, lies Kepler’s older cousin - N103B. However, unlike Kelper’s supernova, there are no recorded historical sightings of the explosion. 

Both N103B and Kepler’s supernova are thought to have formed from an aging red giant orbiting and already “dead” white dwarf. Typically older stars molt (meaning they shed their outer layers) and this material falls onto the companion white dwarf. Once the white dwarf has accumulated enough mass, it will become unstable and ultimately explode. 

Just a decade ago, scientists thought the white dwarf red giant scenario was the common cause of Type Ia explosions, scientists now suggest that a pair of white dwarf stars are the more likely (and common) culprit. The new Spitzer data shows how complex these explosions are and how there are many different triggers. However, the exact reason as to why these “dead” stars explode is still to be determined. 

-ALT

Image & Source Credit: NASA/JPL-CalTech

Why comets are like deep-fried ice cream…

Yes, you read that correctly. Comets are like deep fried ice cream - although you wouldn’t want to eat them. They resemble the delectable dessert in that they have a hard, outer crust covering a soft interior. Right now the ESA-led Rosetta mission is busy analyzing features on comet 67P/Churyumov-Gerasimenko in order to better understand the perplexing nature of a comet.

While the Rosetta spacecraft is busy orbiting comet 67P and beaming back precious data, scientists here on Earth are busy tinkering with ice and organics in the lab in an effort to better understand the nature of comets. Astronomers experimented with with an icebox-like instrument, called Himalaya, and believe they know why comets have a hard, outer crust.

“A comet is like deep fried ice cream,” said Murthy Gudipati of NASA’s Jet Propulsion Laboratory in Pasadena, California, corresponding author of a recent study appearing in The Journal of Physical Chemistry. “The crust is made of crystalline ice, while the interior is colder and more porous. The organics are like a final layer of chocolate on top.”

Thanks to Himalaya, the researchers discovered that fluffy surface ice would crystallize and harden as the comet heated on its approach to the Sun. Crystals of water-ice would form, becoming denser and more structured as other organic molecules would be pushed to the surface, resulting in a crunchy crust littered with organic dust.

Scientists already knew that comets have soft interiors and seemingly hard crusts. NASA’s Deep Impact and the European Space Agency’s Rosetta spacecraft both inspected comets up close, finding evidence of soft, porous interiors. Last Nov., Rosetta’s Philae probe attempted to make the first ever landing on a comet’s surface. Due to the extremely hard surface, the lander bounced several times and is hibernating in the shadows somewhere on the comet’s surface.The Deep Impact mission had also observed black, soot-like coats of comets, made up of organic molecules and dust.

Despite everything we know know about comets, the exact composition of the crust and how it forms still remains a mystery. In the latest study, researchers used amorphous, or porous ice, which is what comets are thought to be composed of, to make a crystallized comet crust model.

“In this state, water vapor molecules are flash-frozen at extremely cold temperatures of around 30 Kelvin (minus 243 degrees Celsius, or minus 405 degrees Fahrenheit), sort of like Han Solo in the Star Wars movie “The Empire Strikes Back.” Disorderly states are preserved: Water molecules are haphazardly mixed with other molecules, such as the organics, and remain frozen in that state. Amorphous ice is like cotton candy,” explains Gudipati: “light and fluffy and filled with pockets of space.”

On Earth, all ice is in the crystalline form, as our planet is not cold enough to form amorphous ice. Even a handful of loose snow is in the crystalline form, but contains much smaller ice crystals than those in snowflakes.

Gudipati and Lignell used the Himalaya instrument to slowly warm their amorphous ice mixtures from 30 Kelvin to 150 Kelvin (minus 123 degrees Celsius, or minus 190 degrees Fahrenheit), simulating conditions a comet would experience as it approaches the Sun. The ice had been infused with a type of organics, called polycyclic aromatic hydrocarbons (PAHs), which are prevalent in deep space. The results of their experiment were quite surprising.

“The PAHs stuck together and were expelled from the ice host as it crystallized. This may be the first observation of molecules clustering together due to a phase transition of ice, and this certainly has many important consequences for the chemistry and physics of ice,” said Lignell.

With PAHs ejected from the ice mixtures, the water molecules had room to link up and form the more tightly packed structures of crystalline ice.

“What we saw in the lab — a crystalline comet crust with organics on top — matches what has been suggested from observations in space,” said Gudipati. Deep fried ice cream is really the perfect analogy, because the interior of the comets should still be very cold and contain the more porous, amorphous ice.”

Understanding how comets are formed is key to understanding the role they played in delivering water and other organics to the early Earth. Data from the Rosetta mission indicates asteroids, not comets, may have been the primary carriers of life; however, the debate is still ongoing and comets could play a part. If scientists can unlock the secrets of these icy bodies, they can unlock the secrets of the early solar system.

Gudipati said, “It’s beautiful to think about how far we have come in our understanding of comets. Future missions designed to bring cold samples of comets back to Earth could allow us to fully unravel their secrets.”

-ALT

Image & Source Credit: NASA/ESA