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

First British Astronaut to the ISS, American, Russian and Briton Join International Space Station Crew

Hatches between the International Space Station and an arriving Soyuz spacecraft opened at 2:58 p.m. EST Tuesday, signaling the arrival of three new crew members, including NASA astronaut Tim Kopra. They will join other residents on the station to continue important research that advances NASA's journey to Mars, while making discoveries that can benefit all of humanity.
Kopra, Russian Federal Space Agency (Roscosmos) cosmonaut Yuri Malenchenko and ESA (European Space Agency) astronaut Tim Peake launched from the Baikonur Cosmodrome in Kazakhstan at 6:03 a.m. (5:03 p.m. in Baikonur) and, after orbiting Earth four times, manually docked to the station at 12:33 p.m.

The arrival of Kopra, Malenchenko and Peake returns the station's crew complement to six. The three join Expedition 46 Commander Scott Kelly of NASA and Flight Engineers Sergey Volkov and Mikhail Kornienko of Roscosmos. During more than five months on humanity’s only microgravity laboratory, the Expedition 46 crew members will conduct more than 250 science investigation in fields including biology, Earth science, human research, physical sciences and technology development.


Kopra, Malenchenko and Peake will remain aboard the station until early June 2016. Kelly and Kornienko will return to Earth at the conclusion of their one-year mission on March 1, 2016, along with Volkov. The pair will have spent 340 consecutive days living and working in space to advance understanding of the medical, psychological and biomedical challenges astronauts face during long duration spaceflight, in addition to developing countermeasures to reverse those effects.

Ongoing station research also includes the Microbial Payload Tracking Series project, which uses microbial analysis techniques to establish a census of the microorganisms living on surfaces and in the atmosphere of the space station. Along with crew members and experimental payloads, the space station is home to a variety of microbes, which are a cleaning nuisance and potentially threatening to crew health and station equipment. Analyzing these microbes can help determine whether some are more virulent in space, and which genetic changes might be involved in this response. Results from the investigation can be used to evaluate cleaning strategies, and to mitigate microbe-related risks to crew health and spacecraft system performance.

The crew members are scheduled to receive several cargo spacecraft -- including multiple U.S. commercial resupply vehicles from SpaceX and Orbital ATK -- each delivering tons of food, fuel, supplies and research.

SpaceX will deliver on its eighth commercial resupply services mission an important technology project that could help drive future exploration. Developed under a public-private partnership, the Bigelow Expandable Activity Module (BEAM) is an expandable habitat technology demonstration for the International Space Station. Expandable habitats can greatly decrease the amount of transport volume for future space missions, weighing less and taking up less room on a rocket. These habitats have the potential to provide a comfortable area for astronauts to live and work, as well as a varying degree of protection from solar and cosmic radiation, space debris and other elements of the space environment. Highly reliable habitation systems will be essential to keep future crews healthy and productive in the deep-space environment during missions in lunar orbit where the systems will be validated for future missions to Mars that could last as long as 1,100 days.

For 15 years, humans have been living continuously aboard the station to advance scientific knowledge and demonstrate new technologies, making research breakthroughs not possible on Earth that also will enable long-duration human and robotic exploration into deep space. A truly global endeavor, more than 200 people from 15 countries have visited the unique microgravity laboratory that has hosted more than 1,700 research investigations from researchers in more than 80 countries.

SOHO Celebrates 20 Years of Space-based Science

After 20 years in space, ESA and NASA’s Solar and Heliospheric Observatory, or SOHO, is still going strong. Originally launched in 1995 to study the sun and its influence out to the very edges of the solar system, SOHO revolutionized this field of science, known as heliophysics, providing the basis for nearly 5,000 scientific papers. SOHO also found an unexpected role as the greatest comet hunter of all time—reaching 3,000 comet discoveries in September 2015.

-Dr. Joe Gurman of NASA's Goddard Space Flight Center provides commentary on selected shots from SOHO's 20 years in space-

Credits
Genna Duberstein (USRA): Producer
Scott Wiessinger (USRA): Producer
Joe Gurman (NASA/GSFC): Scientist
Bernhard Fleck (ESA): Scientist

Courtesy of NASA

Water World

Although Enceladus and Saturn's rings are largely made up of water ice, they show very different characteristics. The small ring particles are too tiny to retain internal heat and have no way to get warm, so they are frozen and geologically dead. Enceladus, on the other hand, is subject to forces that heat its interior to this very day. This results in its famous south polar water jets, which are just visible above the moon’s dark, southern limb, along with a sub-surface ocean.

Recent work by Cassini scientists suggests that Enceladus (313 miles or 504 kilometers across) has a global ocean of liquid water under its surface. This discovery increases scientists' interest in Enceladus and the quest to understand the role of water in the development of life in the solar system. (For more on the sub-surface ocean, see this story.)

This view looks toward the unilluminated side of the rings from about 0.3 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 29, 2015.

The view was acquired at a distance of approximately 630,000 miles (1.0 million kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase angle of 155 degrees. Image scale is 4 miles (6 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov or http://www.nasa.gov/cassini . The Cassini imaging team homepage is at http://ciclops.org .

Credit: NASA/JPL-Caltech/Space Science Institute

Shoot the Supermoon Eclipse like a Pro

Much of the United States will be treated to a rare combination supermoon and lunar eclipse on Sunday night, Sept. 27. Since the next celestial event of this kind won’t happen until 2033, you might want to preserve the memory with a great photo.
Enter Bill Ingalls, NASA’s senior photographer and a fixture at NASA Headquarters, with a salt-and-pepper ponytail and a ready smile. Bill has traveled all over the world for more than 25 years photographing missions for NASA, but he can also be found right in his own backyard – the DC area – anytime there’s a supermoon, meteor shower or other eye candy in the heavens.

Bill’s #1 tip for capturing that great lunar photo: “Don’t make the mistake of photographing the moon by itself with no reference to anything,” he said. “I’ve certainly done it myself, but everyone will get that shot. Instead, think of how to make the image creative—that means tying it into some land-based object. It can be a local landmark or anything to give your photo a sense of place.”

Ingalls goes to great lengths to scout out the perfect vantage point to juxtapose the moon with various Washington monuments. “It means doing a lot of homework. I use Google Maps and other apps – even a compass -- to plan where to get just the right angle at the right time.”  He often scouts locations a day or more in advance, getting permission to access rooftops or traveling to remote areas to avoid light pollution.

A slight miscalculation can result in a mad scramble; he recalls seeing hundreds of photographers who set tripods hundreds of yards away for a supermoon shot from Washington’s Iwo Jima monument. “I thought my calculations were wrong, but – sure enough – the moon popped up right where I expected, and then came the stampede,” he chuckled.

You don’t have to live near an iconic landmark or talk your way onto a rooftop to get the perfect shot. Instead, work with what you have. Ingalls trekked to Shenandoah National Park in 2009 to photograph Comet Lulin and faced a challenge. “I had just basic equipment and saw all these people with great telescopes making a picture I could never get. So what could I do differently?” Ingalls aimed his long lens between the trees, using the red light of his headlamp to paint the forest with a long exposure. The result was magical, with National Geographic naming his comet image one of the top 10 space photos of the year.

Ingalls says the Sep. 27 supermoon eclipse can be a great family activity, since it’s not too much past bedtime. “I think this would be a lot of fun to do with kids, if nothing else, to just have them witness it and talk about what’s taking place.” He recommends personalizing the experience by using people in the shot. “There are lots of great photos of people appearing to be holding the moon in their hand and that kind of thing. You can get really creative with it,” he said.

Unlike a meteor shower or an ISS pass, time is on your side on Sep. 27. The eclipse will last more than an hour, peaking at 10:47 p.m. EDT. So you have lots of time to experiment with different locations, exposure times and foregrounds.

Is it hopeless to attempt a supermoon eclipse with a smartphone camera? Ingalls says, “It’s all relative. For me, it would be maddening and frustrating--yet it may be a good challenge, actually. You’re not going to get a giant moon in your shot, but you can do something more panoramic, including some foreground that’s interesting. Think about being in an urban area where it’s a little bit brighter.”

To get the right light balance of the moon on newer iPhones and other smartphones, “Tap the screen and hold your finger on the object (in this case, the moon) to lock the focus. Then slide your finger up or down to darken or lighten the exposure.”

For digital SLR photography, Ingalls uses the daylight white balance setting for capturing moonlight, since sunlight is being reflected. For those with longer lenses he advises, “Keep in mind that the moon is a moving object. It’s a balancing act between trying to get the right exposure and realizing that the shutter speed typically needs to be a lot faster.”

Ingalls will be traveling in Colorado during the upcoming eclipse, but – not surprisingly – “I’ll be bringing my equipment, so who knows?”

Distorted Green Flash Sunset over Italy

This was one strange sunset. For one thing, the typically round Sun appeared distorted, geometrically, and multiply layered. For another, some of these layers appeared unusually green. The Sun, of course, was just fine -- its odd appearance was caused entirely by its light refracting in the Earth's atmosphere. When layers of the Earth's atmosphere are unusually warm, layers of the Sun may appear distorted or even seen multiple times. The effect is most strong nearest sunrise and sunset when terrestrial inversion layers occupy distinct altitudes above the horizon. Different colors of the Sun may also become deflected by significantly different amounts, so that the uppermost superior image may appear momentarily green -- a phenomenon known as a green flash. This
image was taken in February from Porto Venere, Italy, with San Pietro church situated in the foreground.

Pointy stars and peculiar galaxies Arp 159 and NGC 4725

Pointy stars and peculiar galaxies span this cosmic snapshot, a telescopic view toward the well-groomed constellation Coma Berenices. Bright enough to show off diffraction spikes, the stars are in the foreground of the scene, well within our own Milky Way. But the two prominent galaxies lie far beyond our own, some 41 million light-years distant. Also known as NGC 4747, the smaller distorted galaxy at left is the 159th entry in the Arp Atlas of Peculiar Galaxies, with extensive tidal tails indicative of strong gravitational interactions in its past. At about a 100,000 light-years across, its likely companion on the right is the much larger NGC 4725. At first glance NGC 4725 appears to be a normal spiral galaxy, its central region dominated by the yellowish light of cool, older stars giving way to younger hot blue star clusters along dusty spiral outskirts. Still, NGC 4725 does look a little odd with only one main spiral arm.