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Space News Update — September 13, 2016 —

Contents

In the News

Story 1:

Mars Rover Views Spectacular Layered Rock Formations

Story 2:

Study: Earth’s Carbon Points to Planetary Smash-up

Story 3:

Astronomers Observe Star Reborn In a Flash

Departments

The Night Sky

ISS Sighting Opportunities

NASA-TV Highlights

Space Calendar

Food for Thought

Space Image of the Week

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1. Mars Rover Views Spectacular Layered Rock Formations

On left, this view from Curiosity shows a dramatic hillside outcrop with sandstone layers that scientists refer to as "cross-bedding." On right, Curiosity got close to this outcrop on Sept. 9, 2016, which displays finely layered rocks.

Credits: NASA/JPL-Caltech/MSSS

The layered geologic past of Mars is revealed in stunning detail in new color images returned by NASA's Curiosity

Mars rover, which is currently exploring the “Murray Buttes” region of lower Mount Sharp. The new images arguably

rival photos taken in U.S. National Parks.

Curiosity took the images with its Mast Camera (Mastcam) on Sept. 8. The rover team plans to assemble several

large, color mosaics from the multitude of images taken at this location in the near future.

"Curiosity's science team has been just thrilled to go on this road trip through a bit of the American desert

Southwest on Mars," said Curiosity Project Scientist Ashwin Vasavada, of NASA's Jet Propulsion Laboratory,

Pasadena, California.

The Martian buttes and mesas rising above the surface are eroded remnants of ancient sandstone that originated

when winds deposited sand after lower Mount Sharp had formed. "Studying these buttes up close has given us a

better understanding of ancient sand dunes that formed and were buried, chemically changed by groundwater,

exhumed and eroded to form the landscape that we see today," Vasavada said.

The new images represent Curiosity's last stop in the Murray Buttes, where the rover has been driving for just over

one month. As of this week, Curiosity has exited these buttes toward the south, driving up to the base of the final

butte on its way out. In this location, the rover began its latest drilling campaign (on Sept. 9). After this drilling is

completed, Curiosity will continue farther south and higher up Mount Sharp, leaving behind these spectacular

formations.

Curiosity landed near Mount Sharp in 2012. It reached the base of the mountain in 2014 after successfully finding

evidence on the surrounding plains that ancient Martian lakes offered conditions that would have been favorable for

microbes if Mars has ever hosted life. Rock layers forming the base of Mount Sharp accumulated as sediment within

ancient lakes billions of years ago.

On Mount Sharp, Curiosity is investigating how and when the habitable ancient conditions known from the mission's

earlier findings evolved into conditions drier and less favorable for life.

Source: NASA Return to Contents

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2. Study: Earth’s Carbon Points to Planetary Smash-up

A schematic depiction of proto Earth’s merger with a potentially Mercury-like planetary embryo, a scenario supported by

new high pressure-temperature experiments at Rice University. Magma ocean processes could lead planetary embryos to

develop silicon- or sulphur-rich metallic cores and carbon-rich outer layers. If Earth merged with such a planet early in its

history, it could explain how Earth acquired its carbon and sulphur. (Figure courtesy of Rajdeep Dasgupta)

Research by Rice University Earth scientists suggests that virtually all of Earth’s life-giving carbon could have

come from a collision about 4.4 billion years ago between Earth and an embryonic planet similar to Mercury.

The ratio of volatile elements in Earth’s mantle suggests that virtually all of the planet’s life-giving carbon came

from a collision with an embryonic planet approximately 100 million years after Earth formed.

In a new study this week in Nature Geoscience, Rice petrologist Rajdeep Dasgupta and colleagues offer a new

answer to a long-debated geological question: How did carbon-based life develop on Earth, given that most of

the planet’s carbon should have either boiled away in the planet’s earliest days or become locked in Earth’s

core?

“The challenge is to explain the origin of the volatile elements like carbon that remain outside the core in the

mantle portion of our planet,” said Dasgupta, who co-authored the study with lead author and Rice

postdoctoral researcher Yuan Li, Rice research scientist Kyusei Tsuno and Woods Hole Oceanographic Institute

colleagues Brian Monteleone and Nobumichi Shimizu.

Dasgupta’s lab specializes in recreating the high-pressure and high-temperature conditions that exist deep

inside Earth and other rocky planets. His team squeezes rocks in hydraulic presses that can simulate conditions

about 250 miles below Earth’s surface or at the core-mantle boundary of smaller planets like Mercury.

“Even before this paper, we had published several studies that showed that even if carbon did not vaporize

into space when the planet was largely molten, it would end up in the metallic core of our planet, because the

iron-rich alloys there have a strong affinity for carbon,” Dasgupta said.

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Earth’s core, which is mostly iron, makes up about one-third of the planet’s mass. Earth’s silicate mantle

accounts for the other two-thirds and extends more than 1,500 miles below Earth’s surface.

Earth’s crust and atmosphere are so thin that they account for less than 1 percent of the planet’s mass. The

mantle, atmosphere and crust constantly exchange elements, including the volatile elements needed for life.

If Earth’s initial allotment of carbon boiled away into space or got stuck in the core, where did the carbon in

the mantle and biosphere come from?

“One popular idea has been that volatile elements like carbon, sulphur, nitrogen and hydrogen were added

after Earth’s core finished forming,” said Li, who is now a staff scientist at Guangzhou Institute of

Geochemistry, Chinese Academy of Sciences. “Any of those elements that fell to Earth in meteorites and

comets more than about 100 million years after the solar system formed could have avoided the intense heat

of the magma ocean that covered Earth up to that point.

“The problem with that idea is that while it can account for the abundance of many of these elements, there

are no known meteorites that would produce the ratio of volatile elements in the silicate portion of our planet,”

Li said.

In late 2013, Dasgupta’s team began thinking about unconventional ways to address the issue of volatiles and

core composition, and they decided to conduct experiments to gauge how sulphur or silicon might alter the

affinity of iron for carbon. The idea didn’t come from Earth studies, but from some of Earth’s planetary

neighbors.

“We thought we definitely needed to break away from the conventional core composition of just iron and

nickel and carbon,” Dasgupta recalled. “So we began exploring very sulphur-rich and silicon-rich alloys, in part

because the core of Mars is thought to be sulphur-rich and the core of Mercury is thought to be relatively

silicon-rich.

“It was a compositional spectrum that seemed relevant, if not for our own planet, then definitely in the

scheme of all the terrestrial planetary bodies that we have in our solar system,” he said.

The experiments revealed that carbon could be excluded from the core — and relegated to the silicate mantle

— if the iron alloys in the core were rich in either silicon or sulphur.

“The key data revealed how the partitioning of carbon between the metallic and silicate portions of terrestrial

planets varies as a function of the variables like temperature, pressure and sulphur or silicon content,” Li said.

The team mapped out the relative concentrations of carbon that would arise under various levels of sulphur

and silicon enrichment, and the researchers compared those concentrations to the known volatiles in Earth’s

silicate mantle.

“One scenario that explains the carbon-to-sulphur ratio and carbon abundance is that an embryonic planet like

Mercury, which had already formed a silicon-rich core, collided with and was absorbed by Earth,” Dasgupta

said. “Because it’s a massive body, the dynamics could work in a way that the core of that planet would go

directly to the core of our planet, and the carbon-rich mantle would mix with Earth’s mantle.

“In this paper, we focused on carbon and sulphur,” he said. “Much more work will need to be done to

reconcile all of the volatile elements, but at least in terms of the carbon-sulphur abundances and the carbon-

sulphur ratio, we find this scenario could explain Earth’s present carbon and sulphur budgets.”

The research was supported by NASA and the National Science Foundation.

Source: Rice University Return to Contents

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3. Astronomers Observe Star Reborn In a Flash

This image of the Stingray nebula, a planetary nebula 2700 light-years from Earth, was taken with the Wide

Field and Planetary Camera 2 (WFPC2) in 1998. In the center of the nebula the fast evolving star SAO 244567

is located. Observations made within the last 45 years showed that the surface temperature of the star

increased by almost 40 000 degree Celsius. Now new observations of the spectra of the star have revealed

that SAO 244567 has started to cool again. Credit: ESA/Hubble & NASA

An international team of astronomers using Hubble have been able to study stellar evolution in real time. Over

a period of 30 years dramatic increases in the temperature of the star SAO 244567 have been observed. Now

the star is cooling again, having been reborn into an earlier phase of stellar evolution. This makes it the first

reborn star to have been observed during both the heating and cooling stages of rebirth.

Even though the Universe is constantly changing, most processes are too slow to be observed within a human

lifespan. But now an international team of astronomers have observed an exception to this rule. “SAO 244567

is one of the rare examples of a star that allows us to witness stellar evolution in real time”, explains Nicole

Reindl from the University of Leicester, UK, lead author of the study. “Over only twenty years the star has

doubled its temperature and it was possible to watch the star ionizing its previously ejected envelope, which is

now known as the Stingray Nebula.”

SAO 244567, 2700 light-years from Earth, is the central star of the Stingray Nebula and has been visibly

evolving between observations made over the last 45 years. Between 1971 and 2002 the surface temperature

of the star skyrocketed by almost 40 000 degrees Celsius. Now new observations made with the Cosmic

Origins Spectrograph (COS) on the NASA/ESA Hubble Space Telescope have revealed that SAO 244567 has

started to cool and expand.

This is unusual, though not unheard-of [1], and the rapid heating could easily be explained if one assumed

that SAO 244567 had an initial mass of 3 to 4 times the mass of the Sun. However, the data show that SAO

244567 must have had an original mass similar to that of our Sun. Such low-mass stars usually evolve on

much longer timescales, so the rapid heating has been a mystery for decades.

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Back in 2014 Reindl and her team proposed a theory that resolved the issue of both SAO 244567’s rapid

increase in temperature as well as the low mass of the star. They suggested that the heating was due to what

is known as a helium-shell flash event: a brief ignition of helium outside the stellar core [2].

This theory has very clear implications for SAO 244567’s future: if it has indeed experienced such a flash, then

this would force the central star to begin to expand and cool again — it would return back to the previous

phase of its evolution. This is exactly what the new observations confirmed. As Reindl explains: “The release of

nuclear energy by the flash forces the already very compact star to expand back to giant dimensions — the

born-again scenario.”

It is not the only example of such a star, but it is the first time ever that a star has been observed during both

the heating and cooling stages of such a transformation.

Yet no current stellar evolutionary models can fully explain SAO 244567’s behavior. As Reindl elaborates: “We

need refined calculations to explain some still mysterious details in the behavior of SAO 244567. These could

not only help us to better understand the star itself but could also provide a deeper insight in the evolution of

central stars of planetary nebulae.”

Until astronomers develop more refined models for the life cycles of stars, aspects of SAO 244567’s evolution

will remain a mystery.

Notes

[1] The other star thought to have experienced the same type of helium flash event (see [2]) is FG Sagittae,

located in the constellation Sagitta, making SAO 244567 the second of its kind. However, other objects

undergoing similar “born-again” scenarios are known, including Sakurai’s Object, located in Sagittarius.

[2] Helium flash events, also known as late thermal pulses, occur late in the evolution of about 25% of low- to

medium-mass stars. After evolving off the main sequence, these stars enter the red giant phase, where the

star expands dramatically. Various changes occur in the star’s chemical and physical composition during this

phase, until it has burnt most of the helium available in its core, which is by then composed of carbon and

oxygen. Helium fusion continues in a thin shell around the core, but then turns off as the helium becomes

depleted. This allows hydrogen fusion to start in a layer above the helium layer. After enough additional

helium accumulates, helium fusion is reignited, leading to a thermal pulse which eventually causes the star to

expand, cool and brighten temporarily.

Source: Hubble European Space Agency Return to Contents

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The Night Sky

Source: Sky and Telescope Return to Contents

Tuesday, September 13

As dusk turns to night, Arcturus twinkles due west.

It's getting lower every week. And off to its right in

the northwest, the Big Dipper is turning more and

more level.

Wednesday, September 14

How soon after sunset can you see the big Summer

Triangle? Face east. Vega, the Triangle's brightest

star, is practically at the zenith (for skywatchers at

mid-northern latitudes). Deneb is the first bright star

you encounter to Vega's east-northeast. Altair shines

less high in the southeast.

Thursday, September 15

A winter preview: Step out before the first light of

dawn this week, and the sky displays the same starry

panorama as it will at dusk next February. Orion

stands high in the south, Sirius and Canis Major

sparkle to its lower left, and Gemini occupies the high

east.

Friday, September 16

Full Moon (exact at 3:05 p.m. Eastern Daylight Time).

As night comes on, look for the Great Square of

Pegasus to its upper left. The Square, a bit larger

than a fist at arm's length, stands on one corner.

A fairly deep penumbral (fringe) eclipse of the Moon

is visible from eastern Europe, eastern Africa, Asia,

and the westernmost Pacific.

Saturday, September 17

Now the Moon shines below the Great Square of Pegasus. From the Great Square's left corner extends a big

line of three 2nd-magnitude stars, running to the lower left, that mark the head, backbone and leg of the

constellation Andromeda. The line of three includes the Square's corner.

Upper left from the end of this line, you'll find W-shaped Cassiopeia tilting up.

Fast Mars continues to pull farther away from Saturn and Antares in its background

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ISS Sighting Opportunities (from Denver)

Date Visible Max Height Appears Disappears

Wed Sep 14, 4:28 AM 1 min 12° 12° above N 10° above NNE

Wed Sep 14, 6:05 AM 2 min 11° 10° above N 10° above NNE

Thu Sep 15, 5:12 AM 1 min 10° 10° above NNW 10° above NNE

Fri Sep 16, 4:21 AM < 1 min 10° 10° above N 10° above N

Fri Sep 16, 5:57 AM 3 min 14° 10° above NNW 12° above NE

Sat Sep 17, 5:05 AM 2 min 11° 10° above NNW 10° above NNE

Sighting information for other cities can be found at NASA’s Satellite Sighting Information

NASA-TV Highlights (all times Eastern Time Zone)

Tuesday, September 13

11 a.m. - Replay of the Expedition 49-50 Crew News Conference at the Gagarin Cosmonaut Training Center

in Star City, Russia (all channels)

3 p.m. - Replay of the ISS Expedition 50-51 Crew News Conference (Whitson, Pesquet, Novitskiy) (all

channels)

7 p.m. - NASA Television Video File News Feed of the ISS Expedition 49-50 Crew’s Departure from the

Gagarin Cosmonaut Training Center in Star City, Russia for the Baikonur Cosmodrome in Kazakhstan

(Kimbrough, Ryzhikov, Borisenko) (all channels)

9 p.m. - NASA Television Video B-Roll Feed of Training and Previous Mission of ISS Expedition 49 Flight

Engineer Shane Kimbrough of NASA (NTV-3 (Media))

11 p.m., Tuesday, September 13 - Replay of the ISS Expedition 50-51 Crew News Conference (Whitson,

Pesquet, Novitskiy) (NTV-1 (Public))

Wednesday, September 14

1 p.m. - ISS Expedition 49 In-Flight Educational Event with the Vintage High School in Napa, California and

Flight Engineer Kate Rubins of NASA (all channels)

2:30 p.m. - Live Interviews with ISS Expedition 48 Commander Jeff Williams of NASA (starts at 2:45 p.m.)

(all channels)

3:30 p.m., 7 p.m. and 11 p.m. - Replay of ISS Expedition 49 In-Flight Educational Event with the Vintage

High School in Napa, California and Flight Engineer Kate Rubins of NASA (all channels)

Friday, September 16

7 a.m. and 11 a.m. - Replay of ISS Expedition 49 In-Flight Educational Event with the Vintage High School

in Napa, California and Flight Engineer Kate Rubins of NASA (all channels)

Watch NASA TV online by going to the NASA website. Return to Contents

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Space Calendar

Sep 13 - Tiangong 2 CZ-2F Launch (2nd Chinese Space Station)

Sep 13 - Comet 188P/LINEAR-Mueller Closest Approach To Earth (1.786 AU)

Sep 13 - Comet 228P/LINEAR At Opposition (3.831 AU)

Sep 13 - Comet C/2015 H2 (PANSTARRS) Perihelion (4.967 AU)

Sep 13 - Comet 95P/Chiron Closest Approach To Earth (17.399 AU)

Sep 13 - Asteroid 1217 Maximiliana Closest Approach To Earth (1.465 AU)

Sep 14 - Comet 302P/Lemmon-PANSTARRS Closest Approach To Earth (2.360 AU)

Sep 14 - Comet C/2016 N4 (MASTER) At Opposition (3.686 AU)

Sep 14 - Amor Asteroid 2016 RG18 Near-Earth Flyby (0.086 AU)

Sep 14 - Amor Asteroid 2016 QM10 Near-Earth Flyby (0.094 AU)

Sep 14 - Asteroid 116939 Jonstewart Closest Approach To Earth (1.627 AU)

Sep 14 - 180th Anniversary (1836), Aubres Meteorite Fall in France

Sep 15 - Perusat 1/ SkySat 4-7 Vega Launch

Sep 15 - Moon Occults Neptune

Sep 15 - Comet 124P/Mrkos At Opposition (3.852 AU)

Sep 15 - Comet 95P/Chiron At Opposition (17.400 AU)

Sep 15 - Asteroid 2 Pallas Occults 2UCAC 33492853 (12.3 Magnitude Star)

Sep 15 - Apollo Asteroid 2011 BT15 Near-Earth Flyby (0.051 AU)

Sep 15 - Atira Asteroid 434326 (2004 JG6) Closest Approach To Earth (0.692 AU)

Sep 15 - Asteroid 71000 Hughdowns Closest Approach To Earth (1.441 AU)

Sep 15 - 25th Anniversary (1991), UARS Launch from Space Shuttle Discovery

Sep 15 - Jean-Sylvain Bailly's 280th Birthday (1736)

Sep 16 - Progress MS-3 Soyuz U Launch (International Space Station 64P)

Sep 16 - WorldView 4 (GeoEye 2) Atlas 5 Launch

Sep 16 - Penumbral Lunar Eclipse

Sep 16 - International Day for the Preservation of the Ozone Layer

Sep 16 - Comet 255P/Levy Closest Approach To Earth (1.831 AU)

Sep 16 -Aten Asteroid 2016 RT20 Near-Earth Flyby (0.040 AU)

Sep 16 - Centaur Object 2015 KJ153 At Opposition (2.982 AU)

Sep 16 - 20th Anniversary (1996), STS-79 Launch (Space Shuttle Atlantis, Mir Space Station)

Sep 16 - Seth Chandler's 170th Birthday (1846)

Sep 17 - Comet C/2013 P3 (Palomar) At Opposition (8.624 AU)

Sep 17 - Apollo Asteroid 2016 QL44 Near-Earth Flyby (0.009 AU)

Sep 17 - Asteroid 1282 Utopia Closest Approach To Earth (1.854 AU)

Sep 17 - 60th Anniversary (1956), Inauguration of Stockert Radio Telescope

Sep 17 - Bernhard Riemann's 190th Birthday (1826)

Source: JPL Space Calendar Return to Contents

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Food for Thought

Detailed Age Map Shows How Milky Way Came Together

Age structure of the Milky Way’s halo

Using colors to identify the approximate ages of more than 130,000 stars in the Milky Way’s halo, University of

Notre Dame astronomers have produced the clearest picture yet of how the galaxy formed more than 13.5

billion years ago.

Astrophysicist Daniela Carollo, research assistant professor in the Department of Physics at the University of

Notre Dame, and Timothy Beers, Notre Dame Chair of Astrophysics, along with research assistant professor

Vinicius Placco and their colleagues, published their findings in Nature Physics, including a chronographic (age)

map that supports a hierarchical model of galaxy formation. That model, developed by theoreticians over the

past few decades, suggests that the Milky Way formed by merging and accretion of small mini-halos

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containing stars and gas, and that the oldest of the Milky Way’s stars are at the center of the galaxy and

younger stars and galaxies merged with the Milky Way, drawn in by gravity over billions of years.

“We haven’t previously known much about the age of the most ancient component of the Milky Way, which is

the Halo System,” Carollo said. “But now we have demonstrated conclusively for the first time that ancient

stars are in the center of the galaxy and the younger stars are found at longer distances. This is another piece

of information that we can use to understand the assembly process of the galaxy, and how galaxies in general

formed.”

Using data from the Sloan Digital Sky Survey, in which Notre Dame is a partner, the scientists identified more

than 130,000 blue horizontal-branch stars, which burn helium in their cores, and exhibit different colors based

on their ages. They are the only type of star whose age can be estimated by color alone. The technique they

employed is one that Beers helped develop about 25 years ago when he was still a postdoctoral fellow.

The mapped stars show a clear hierarchy, with the oldest stars near the center of the galaxy, and younger

stars further away.

“The colors, when the stars are at that stage of their evolution, are directly related to the amount of time that

star has been alive, so we can estimate the age,” Beers said. “Once you have a map, then you can determine

which stars came in first and the ages of those portions of the galaxy. We can now actually visualize how our

galaxy was built up and inspect the stellar debris from some of the other small galaxies being destroyed by

their interaction with ours during its assembly.”

Carollo explained that initial gas clouds containing primordial material, such as hydrogen and helium, formed

the first stars. Clouds with various masses and gas content behaved differently: The smaller clouds formed

one or two generation of stars (older objects) and then merged with other clouds and ended in the center of

the galaxy pulled in by gravity, while larger mass clouds formed multiple generation of stars (younger objects)

before they merged.

Still larger galaxies, such as the Milky Way, grew as their gravity pulled in and forced mergers with these

smaller galaxies.

Today, it is only possible to use these techniques in our own galaxy and in the dwarf satellite galaxies that

surround the Milky Way. However, the James Webb Space Telescope, set to be launched in 2018, is expected

to gather much more data from distant galaxies, including the first glows from the Big Bang. Using the aging

method that Beers’ Galactic Archaeology group at Notre Dame employed, those data can fill in pieces of the

puzzle on our own galaxy’s formation, as well as questions about how the universe came into being.

Source: University of Notre Dame Return to Contents

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Space Image of the Week

Explanation: Follow the handle of the Big Dipper away from the dipper's bowl, until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well-defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (left), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the human eye, the above long-exposure, deep-field image taken earlier this year shows much of the faint complexity that actually surrounds the smaller galaxy. Thousands of the faint dots in background of the featured image are actually galaxies far across the universe.

Source: NASA APOD Return to Contents

The Whirlpool Galaxy and Beyond Image Credit & Copyright: Álvaro Ibáñez Pérez