ESA Herschel mission examines New molecules around old stars

ESA Herschel image of the Helix Nebula using the SPIRE instrument at wavelengths around 250 micrometres, superimposed on Hubble image of the nebula. 

The spectrum corresponds to the outer region of the Helix Nebula outlined on the SPIRE image. 

It identifies the OH+ molecular ion, which is needed for the formation of water.

ESA’s Herschel space observatory is the first to detect this molecule in planetary nebulas, the product of dying Sun-like stars. 

Credit: Hubble image: NASA/ESA/C.R. O’Dell (Vanderbilt University), M. Meixner & P. McCullough (STScI); Herschel image: ESA/Herschel/SPIRE/MESS Consortium/M. Etxaluze et al.

Using ESA’s Herschel space observatory, astronomers have discovered that a molecule vital for creating water exists in the burning embers of dying Sun-like stars.

When low- to middleweight stars like our Sun approach the end of their lives, they eventually become dense, white dwarf stars.

In doing so, they cast off their outer layers of dust and gas into space, creating a kaleidoscope of intricate patterns known as planetary nebulas.

These actually have nothing to do with planets, but were named in the late 18th century by astronomer William Herschel, because they appeared as fuzzy circular objects through his telescope, somewhat like the planets in our Solar System.

Over two centuries later, planetary nebulas studied with William Herschel's namesake, the Herschel space observatory, have yielded a surprising discovery.

Like the dramatic supernova explosions of weightier stars, the death cries of the stars responsible for planetary nebulas also enrich the local interstellar environment with elements from which the next generations of stars are born.

While supernovas are capable of forging the heaviest elements, planetary nebulas contain a large proportion of the lighter 'elements of life' such as carbon, nitrogen, and oxygen, made by nuclear fusion in the parent star.

A star like the Sun steadily burns hydrogen in its core for billions of years but once the fuel begins to run out, the central star swells into a red giant, becoming unstable and shedding its outer layers to form a planetary nebula.

The remaining core of the star eventually becomes a hot white dwarf pouring out ultraviolet radiation into its surroundings.

This intense radiation may destroy molecules that had previously been ejected by the star and that are bound up in the clumps or rings of material seen in the periphery of planetary nebulas.

The Ring Nebula at optical wavelengths as seen by the Hubble Space Telescope, with Herschel data acquired with SPIRE and PACS over a wavelength range of 51–672 micrometres for the region identified. 

The spectra have been cropped and the scales stretched in order to show the OH+ emission, a molecular ion important for the formation of water. 

ESA’s Herschel space observatory is the first to detect this molecule in planetary nebulas, the product of dying Sun-like stars.

Credit: Hubble image: NASA/ESA/C. Robert O’Dell (Vanderbilt University) Herschel data: ESA/Herschel/PACS & SPIRE/ HerPlaNS survey/I. Aleman et al. 

The harsh radiation was also assumed to restrict the formation of new molecules in those regions.

But in two separate studies using Herschel astronomers have discovered that a molecule vital to the formation of water seems to rather like this harsh environment, and perhaps even depends upon it to form.

The molecule, known as OH+, is a positively charged combination of single oxygen and hydrogen atoms.

The two studies are the first to identify in planetary nebulas this critical molecule needed for the formation of water, although it remains to be seen if the conditions would actually allow water formation to proceed.

"The proximity of the Helix Nebula means we have a natural laboratory on our cosmic doorstep to study in more detail the chemistry of these objects and their role in recycling molecules through the interstellar medium," says Dr M. Etxaluze.

"Herschel has traced water across the Universe, from star-forming clouds to the asteroid belt in our own Solar System," says Göran Pilbratt, ESA's Herschel project scientist.

"Now we have even found that stars like our Sun could contribute to the formation of water in the Universe, even as they are in their death throes."

More information: "Herschel planetary nebula survey (HerPlaNS). First detection of OH+ in planetary nebulae," by I. Aleman et al., and "Herschel spectral-mapping of the Helix Nebula (NGC 7293): extended CO photodissociation and OH+ emission," by M. Etxaluze et al., are published in Astronomy & Astrophysics.

NASA Spitzer coolant loss: Future of Warm mission

Faced with a budget crunch, NASA is likely to shutter its Spitzer space telescope, an infrared space observatory, the fourth and final of NASA's Great Observatories.

The decision may help the US space agency to pump in the saved money to fund the functioning of Hubble, Kepler, Chandra and other orbiting observatories, the US space agency said in a statement.

NASA took stock of its fleet of orbiting astrophysics telescopes and decided which to save and which to shutter based on the findings of an independent review panel and turned down the Spitzer space telescope’s request for an extension.

“To me it is really sad that this country can not find just a few million bucks more to throw into this to keep these things active and running as they should be,” senior review panel chair Ben R. Oppenheimer, an astronomer at the American Museum of Natural History in New York, was quoted as saying.

However, for many, the end of road for Spitzer do not appear as abrupt as they could see it coming.

Spitzer was launched in 2003 as a multipurpose observatory targeted at the low-energy infrared wavelengths of light blocked by earth’s atmosphere.

Spitzer finished its prime mission in 2009 when it exhausted its supply of liquid helium coolant used to chill the instruments.

The loss of the coolant left two of Spitzer’s three instruments unusable, but two of the four wavelength bands on its main camera continued to operate as the Spitzer Warm Mission, Nature reported.

“Right now it can take images in a couple wavebands at tremendous sensitivity, but compared to what it used to do, its capabilities are far reduced,” Oppenheimer said.

“The committee felt that instead of chopping off a bunch of money from other missions, if we end that one large mission we can save everything else,” he explained.

This infrared image from NASA's Spitzer Space Telescope shows the Helix nebula, a cosmic starlet often photographed by amateur astronomers for its vivid colors and eerie resemblance to a giant eye.

The Helix nebula, located about 700 light-years away in the constellation Aquarius, belongs to a class of objects called planetary nebulae.

Discovered in the 18th century, these colourful astronomical beauties were named for their resemblance to gas-giant planets like Jupiter.

Read more about the future of a warmer Spitzer and its role in providing new scientific discovery in the stark coldness of space. 

NASA WISE Image: Helix Nebula

A dying star, called the Helix nebula, is shown surrounded by the tracks of asteroids in an image captured by NASA's Wide-field Infrared Survey Explorer (WISE). 

Image Credit: NASA/JPL-Caltech/UCLA

In an unexpected juxtaposition of cosmic objects that are actually quite far from each other, a newly released image from NASA's Wide-Field Infrared Survey Explorer (WISE) shows a dying star, called the Helix nebula, surrounded by the tracks of asteroids.

The nebula is far outside our solar system, while the asteroid tracks are inside our solar system.

The portrait, discovered by chance in a search for asteroids, comes at a time when the mission's team is celebrating its fourth launch anniversary -- and new lease on life.

In August, NASA decided to bring WISE out of hibernation to search for more asteroids. The mission was rechristened NEOWISE, formerly the name of the asteroid-hunting portion of WISE.

"I was recently looking for asteroids in images collected in 2010, and this picture jumped out at me," said Amy Mainzer, the NEOWISE principal investigator at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "I recognized the Helix nebula right away."

WISE launched into the morning skies above Vandenberg Air Force Base in central California on Dec. 14, 2009.

By early 2011, it had finished scanning the entire sky twice in infrared light, snapping pictures of nearly one billion objects, including remote galaxies, stars and asteroids.

Upon completing its main goals, WISE was put to sleep. Now, engineers are bringing the spacecraft out of slumber, as it cools back down to the chilly temperatures required for infrared observations.

The spacecraft no longer has onboard coolant, but two of its infrared channels still work and can be used for asteroid hunting.

"WISE is the spacecraft that keeps on giving," said Ned Wright of UCLA, the principal investigator of WISE before it transitioned into NEOWISE.

In the Helix nebula image, infrared wavelengths of light have been assigned different colors, with longer wavelengths being red, and shorter, blue.

The bluish-green and red materials are expelled remnants of what was once a star similar to our sun. As the star aged, it puffed up and its outer layers sloughed off.

The burnt-out core of the star, called a white dwarf, is heating the expelled material, inducing it to glow with infrared light.

Over time, the brilliant object, known as a planetary nebula, will fade away, leaving just the white dwarf.

GALEX Image of the Helix Nebula: Bigger in Death than Life

A dying star is throwing a cosmic tantrum in this combined image from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena. 

In death, the star's dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.

Image credit: NASA/JPL-Caltech.


This object, called the Helix nebula, lies 650 light-years away in the constellation of Aquarius.

Also known as NGC 7293, it is a typical example of a class of objects called a planetary nebulae.

Discovered in the 18th century, these cosmic works of art were erroneously named for their resemblance to gas-giant planets.

Planetary nebulae are actually the remains of stars that once looked a lot like our sun. These stars spend most of their lives turning hydrogen into helium in massive runaway nuclear fusion reactions in their cores.

In fact, this process of fusion provides all the light and heat that we get from our sun. Our sun will blossom into a planetary nebula when it dies in about five billion years.

When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen.

Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf.

The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!

The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared.

GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in red, yellow and green.

Where red Spitzer and blue GALEX data combine in the middle, the nebula appears pink. A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA's all-sky Wide-field Infrared Survey Explorer (WISE).

The white dwarf star itself is a tiny white pinprick right at the center of the nebula.

NASA GALEX, Spitzer, WISE Image: Helix Nebula - Unraveling

A dying star is throwing a cosmic tantrum in this combined image from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena.

In death, the star's dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.

This object, called the Helix nebula, lies 650 light-years away, in the constellation of Aquarius.

Also known by the catalog number NGC 7293, it is a typical example of a class of objects called planetary nebulae.

Discovered in the 18th century, these cosmic works of art were erroneously named for their resemblance to gas-giant planets.

Planetary nebulae are actually the remains of stars that once looked a lot like our sun.

These stars spend most of their lives turning hydrogen into helium in massive runaway nuclear fusion reactions in their cores.

In fact, this process of fusion provides all the light and heat that we get from our sun. Our sun will blossom into a planetary nebula when it dies in about five billion years.

When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen.

Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf.

The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!

The glow from planetary nebulae is particularly intriguing as it appears surprisingly similar across a broad swath of the spectrum, from ultraviolet to infrared.

The Helix remains recognizable at any of these wavelengths, but the combination shown here highlights some subtle differences.

The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared.

GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in yellow

A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA's all-sky Wide-field Infrared Survey Explorer (WISE). The white dwarf star itself is a tiny white pinprick right at the center of the nebula.

The brighter purple circle in the very center is the combined ultraviolet and infrared glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved).

This dust was most likely kicked up by comets that survived the death of their star.

Before the star died, its comets, and possibly planets, would have orbited the star in an orderly fashion.

When the star ran out of hydrogen to burn, and blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, kicking up an ongoing cosmic dust storm.

Any inner planets in the system would have burned up or been swallowed as their dying star expanded.

Infrared data from Spitzer for the central nebula is rendered in green (wavelengths of 3.6 to 4.5 microns) and red (8 to 24 microns), with WISE data covering the outer areas in green (3.4 to 4.5 microns) and red (12 to 22 microns). Ultraviolet data from GALEX appears as blue (0.15 to 2.3 microns).

Image Credit: NASA/JPL-Caltech