From NASA JPL Caltech: “Tarantula Nebula Spins Web of Mystery in Spitzer Image”

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From NASA JPL-Caltech

January 27, 2020

Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov

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This image from NASA’s Spitzer Space Telescope shows the Tarantula Nebula in two wavelengths of infrared light. The red regions indicate the presence of particularly hot gas, while the blue regions are interstellar dust that is similar in composition to ash from coal or wood-burning fires on Earth. Credit: NASA/JPL-Caltech

NASA/Spitzer Infrared Telescope no longer in service

The Tarantula Nebula, seen in this image by the Spitzer Space Telescope, was one of the first targets studied by the infrared observatory after its launch in 2003, and the telescope has revisited it many times since. Now that Spitzer is set to be retired on Jan. 30, 2020, scientists have generated a new view of the nebula from Spitzer data.

This high-resolution image combines data from multiple Spitzer observations, most recently in February and September 2019.

“I think we chose the Tarantula Nebula as one of our first targets because we knew it would demonstrate the breadth of Spitzer’s capabilities,” said Michael Werner, who has been Spitzer’s project scientist since the mission’s inception and is based at NASA’s Jet Propulsion Laboratory in Pasadena, California. “That region has a lot of interesting dust structures and a lot of star formation happening, and those are both areas where infrared observatories can see a lot of things that you can’t see in other wavelengths.”

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Figure 1 This annotated image from NASA’s Spitzer Space Telescope shows the Tarantula Nebula in infrared light. The supernova 1987A and the starburst region R136 are noted. The magenta-colored regions are primarily interstellar dust that is similar in composition to ash from coal or wood fires on Earth. Credit: NASA/JPL-Caltech

This anotated image from NASA’s Spitzer Space Telescope shows the Tarantula Nebula in three wavelengths of infrared light, each represented by a different color. The magenta-colored regions are dust composed of molecules called polycyclic aromatic hydrocarbons (PAHs), which are also found in ash from coal, wood and oil fires on Earth. PAHs emit in multiple wavelengths. The PAHs emit in multiple wavelengths, so the magenta color is a combination of red (corresponding to an infrared wavelength of 8 micrometers) and blue (3.6 micrometers). The green color in this image shows the presence of particularly hot gas emitting infrared light at a wavelength of 4.5 micrometers. The stars in the image are mostly a combination of green and blue. White hues indicate regions that radiate in all three wavelengths.

Figure 1 shows the location of Supernova 1987A and the starburst region R136 where massive stars form at a significantly higher rate than anywhere else in the galaxy.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.

Infrared light is invisible to the human eye, but some wavelengths of infrared can pass through clouds of gas and dust where visible light cannot. So scientists use infrared observations to view newborn stars and still-forming “protostars,” swaddled in the clouds of gas and dust from which they formed.

Located in the Large Magellanic Cloud – a dwarf galaxy gravitationally bound to our Milky Way galaxy – the Tarantula Nebula is a hotbed of star formation.

Large Magellanic Cloud by by German astrophotographer Eckhard Slawik

In the case of the Large Magellanic Cloud, such studies have helped scientists learn about rates of star formation in galaxies other than the Milky Way.

The nebula also hosts R136, a “starburst” region, where massive stars form in extremely close proximity and at a rate far higher than in the rest of the galaxy. Within R136, in an area less than 1 light-year across (about 6 trillion miles, or 9 trillion kilometers), there are more than 40 massive stars, each containing at least 50 times the mass of our Sun. By contrast, there are no stars at all within 1 light-year of our Sun. Similar starburst regions have been found in other galaxies, containing dozens of massive stars – a higher number of massive stars than what is typically found in the rest of their host galaxies. How these starburst regions arise remains a mystery.

On the outskirts of the Tarantula Nebula, you can also find one of astronomy’s most-studied stars that has exploded in a supernova. Dubbed 1987A because it was the first supernova spotted in 1987, the exploded star burned with the power of 100 million Suns for months. The shockwave from that event continues to move outward into space, encountering material ejected from the star during its dramatic death.

When the shockwave collides with dust, the dust heats up and begins to radiate in infrared light. In 2006, Spitzer observations saw that light and determined that the dust is largely composed of silicates, a key ingredient in the formation of rocky planets in our solar system. In 2019, scientists used Spitzer to study 1987A to monitor the changing brightness of the expanding shockwave and debris to learn more about how these explosions change their surrounding environment.
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07.14.06
Spitzer Spots Building Blocks of Life in Supernova Remnant

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In 1987 a massive star exploded in a neighboring galaxy, an event called a supernova.

This is an artist’s impression of the SN 1987A remnant. The image is based on real data and reveals the cold, inner regions of the remnant, in red, where tremendous amounts of dust were detected and imaged by ALMA. This inner region is contrasted with the outer shell, lacy white and blue circles, where the blast wave from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation. Image credit: ALMA / ESO / NAOJ / NRAO / Alexandra Angelich, NRAO / AUI / NSF.

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

It was the closest supernova to Earth since the invention of the telescope centuries ago. Now, a team using the Spitzer Space Telescope and the 8-meter Gemini South infrared telescope in Chile have probed the supernova remnant and found the building blocks of rocky planets and all living creatures.

Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

“Supernova 1987A is changing right before our eyes,” said Dr. Eli Dwek, a cosmic dust expert at NASA Goddard Space Flight Center in Greenbelt, Md. For several years Dwek has been following this supernova, named 1987A for the year it was discovered in the Large Magellanic Cloud, a neighboring dwarf galaxy. “What we are seeing now is a milestone in the evolution of a supernova.”

Using infrared telescopes, Dwek and his colleagues detected silicate dust created by the star from before it exploded. This dust survived the intense radiation from the explosion. Nearly 20 years onward, the supernova shock wave blasting through the debris that was shed by the star prior to its fiery death is now sweeping up this dust, making the material “visible” to infrared detectors.

Dust — chemical particles and crystals finer than beach sand — is both a frustration and a fascination for astronomers. Dust can obscure observations of distant stars. Yet dust is the stuff from which all solid bodies are formed. This is why dust research, as bland as it sounds, is one of the most important topics in astronomy and astrobiology.

Dust is made in stars and hurled into space by stellar winds and supernovae, and it is found everywhere in the universe. But little is known about its origin and the processes that affect it. How much dust is made in a star? How much survives the star explosion and subsequent journey through interstellar space? And how do wispy dust clouds form planets and ultimately life?

These are the questions that scientists such as Eli Dwek and his colleague Dr. Patrice Bouchet of the Observatoire de Paris want to answer. With 1987A, they have a perfect laboratory to watch the process unfold.

This is new territory for astronomers, said Bouchet, whose research team made infrared observations of SN 1987A with the Gemini South telescope in Chile. Bouchet’s team is witnessing processes never before seen. This is the first time scientists have direct evidence of dust from a large star surviving a supernova; the first time they detect cold dust intermingled in hot, X-ray-emitting gas of millions of degrees; and the first time they are witnessing sputtering, the process in which dust is eroded by collisions with hot gas.

They frankly don’t know what to expect, and they have already stumbled upon a few surprises.

Infrared telescopes are crucial for this kind of observation. The dust is over a hundred degrees below the freezing point of water and too cold to emit visible light. Infrared is a less-energetic form of radiation than visible light. So while optical telescopes like Hubble can see gas, infrared instruments, similar to night-vision goggles, are needed to see the cold, dark dust.

Through high-resolution infrared imaging with the 8-meter Gemini South telescope, the science team determined that the dust is in the region of the equatorial ring of gas around SN 1987A. This ring of gas and dust, about a light year across, is expanding only very slowly. This suggests that the ring was shed by the star about 600,000 years before it exploded, and that the dust in the ring was formed in the stellar wind and not in the following supernova explosion.

The blast wave from the star’s explosion has now caught up with the ring. The collision has shocked the gas and raised the gas temperature to 10 million degrees, which heats the dust, causing it to glow at infrared wavelengths.

“This much was expected,” said Bouchet. “The collision between the ejecta of Supernova 1987A and the equatorial ring was predicted to occur sometime in the interval of 1995 to 2007, and it is now underway.”

With the location of the dust determined, the scientists used the fine eye of NASA’s Spitzer Space Telescope to determine the composition of the dust. To their great surprise, the dust was pure silicate particles.

Another key finding is that the team has detected far less dust than expected. A star as massive as the one that blew apart in SN 1987A likely produced more silicate dust in the years before the supernova. The under-abundance of dust detected by Spitzer and Gemini South could mean that supernova blast waves destroy more dust than thought possible. If confirmed, this will have broad implications for determining dust origins throughout the universe.

Yet this is a work in progress. “Overall, we are witnessing the interaction of the supernova blast wave with its surrounding medium, creating an environment that is rapidly evolving at all wavelengths,” said Bouchet.

For that reason scientists are planning a series of new infrared, optical, and X-ray observations of SN 1987A with Spitzer, Hubble and Chandra, NASA’s three Great Observatories, now that the supernova has once again become very interesting. Who knows what will be revealed once the dust settles?

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More From Spitzer

To see more amazing images from Spitzer, check out the NASA Selfies App, which has a bundle of new Spitzer images. Available for iOS and Android, the app lets you create a snapshot of yourself in a virtual spacesuit, posing in front of gorgeous cosmic locations, including the Tarantula Nebula. Its simple interface lets you snap a photo of yourself, pick your background and share on social media while also providing you some of the science behind the images.

For an even more immersive Spitzer experience, check out the new Spitzer Final Voyage VR experience, which places you in a 360-degree starscape that replicates Spitzer’s current location orbiting the Sun, about 160 million miles (260 million kilometers) behind Earth. The narrated video shows you how the infrared telescope operates and what the universe looks like in infrared light. The VR experience is viewable on the Spitzer YouTube channel using mobile-based VR headsets, and in the Exoplanets Excursion VR app via Oculus Rift and HTC Vive headsets.

More information about Spitzer is available at the following site:

https://www.nasa.gov/mission_pages/spitzer/main

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