ESA Herschel: Young sun's violent history solves meteorite mystery

An illustration of the wind blown by a newborn star. 

When the energetic particles hit the surrounding material, they may collide with atoms that are present in the star's environment, break them apart and produce new elements. 

Credit: ESA/ATG medialab

Astronomers using ESA's Herschel space observatory to probe the turbulent beginnings of a Sun-like star have found evidence of mighty stellar winds that could solve a puzzling meteorite mystery in our own back yard.

In spite of their tranquil appearance in the night sky, stars are scorching furnaces that spring to life through tumultuous processes, and our 4.5 billion-year-old Sun is no exception.

To glimpse its harsh early days, astronomers gather clues not only in the Solar System but also by studying young stars elsewhere in our Galaxy.

Using Herschel to survey the chemical composition of regions where stars are being born today, a team of astronomers has noticed that one object in particular is different.

The unusual source is a prolific stellar nursery called OMC2 FIR4, a clump of new stars embedded in a gaseous and dusty cloud near to the famous Orion Nebula.

"To our great surprise, we found that the proportion of two chemical species, one based on carbon and oxygen and the other on nitrogen, is much smaller in this object than in any other protostar we know," says Dr Cecilia Ceccarelli, of the Institute de Planétologie et d'Astrophysique de Grenoble, France, who lead the study with Dr Carsten Dominik of the University of Amsterdam in the Netherlands.

In an extremely cold environment, the measured proportion could arise by one of the two compounds freezing onto dust grains and becoming undetectable.

However, at the relatively 'high' temperature of about –200°C found in star-forming regions like OMC2 FIR4, this should not occur.

"The most likely cause in this environment is a violent wind of very energetic particles, released by at least one of the embryonic stars taking shape in this proto-stellar cocoon," Dr Ceccarelli adds.

Orion A, a star-forming nebula lying about 1500 light-years from Earth, as viewed by ESA’s Herschel space observatory.

Orion A is located within the ‘sword of Orion,’ below the three main stars that form the belt of the Orion constellation. 

Embedded in the gaseous and dusty environment of this molecular cloud is the prolific stellar nursery called OMC2 FIR4 (highlighted with a red circle). 

Astronomers studying OMC2 FIR4 with Herschel have discovered that at least one of the embryo stars that are taking shape in this protostellar cocoon is gusting a powerful wind of very energetic particles. 

The inset shows an illustration of the wind blown by this newborn star. 

When the energetic particles hit the surrounding material, they may collide with atoms that are present in the star's environment, break them apart and produce new elements. 

Our Sun likely gusted a similar wind of particles in its early days; this could explain the origin of a puzzling isotope of beryllium, whose traces are found in meteorites. 

Credit: Herschel image: ESA/Herschel/Ph. André, D. Polychroni, A. Roy, V. Könyves, N. Schneider for the Gould Belt survey Key Programme; inset and layout: ESA/ATG medialab

The most abundant molecule in star-forming clouds, hydrogen, can be broken apart by cosmic rays, energetic particles that permeate the entire Galaxy.

The hydrogen ions then combine with other elements that are present – albeit only in trace amounts – in these clouds: carbon and oxygen, or nitrogen.

Normally, the nitrogen compound is also quickly destroyed, yielding more hydrogen for the carbon and oxygen compound. As a result, the latter is far more abundant in all known stellar nurseries.

Strangely enough, though, this was not the case for OMC2 FIR4, suggesting that an additional wind of energetic particles is destroying both chemical species, keeping their abundances more similar.

Astronomers think that a similarly violent wind of particles also gusted through the early Solar System, and this discovery might finally point to an explanation for the origin of a particular chemical element seen in meteorites.

Meteorites are the remains of interplanetary debris that survived the trip through our planet's atmosphere.

These cosmic messengers are one of the few tools we have to directly probe the elements in our Solar System.

"Some elements detected in meteorites reveal that, long ago, these rocks contained a form of beryllium: this is quite puzzling, as we can't quite understand how it got there," explains Dr Dominik.

Isotope Beryllium-10 formation
The formation of the isotope Beryllium-10 in the Universe is an intricate puzzle of its own.

Astronomers know that it is not produced in the interior of stars, like some other elements, nor in the supernova explosion that happens at the end of a massive star's life.

The majority of beryllium-10 was formed in collisions of very energetic particles with heavier elements like oxygen, but since this isotope decays very quickly into other elements, it must have been produced just before it was incorporated in the rocks that would later appear on Earth as meteorites.

To trigger these reactions and produce an amount of beryllium matching that recorded in meteorites, our own Sun must have blown a violent wind in its youth.

These new observations of OMC2 FIR4 give a very strong hint that it is possible for a young star to do this.

"Observing star-forming regions with Herschel not only provides us with a view on what happens beyond our cosmic neighbourhood, but it's also a crucial way to piece together the past of our own Sun and Solar System," says Göran Pilbratt, ESA's Herschel project scientist.

More information: "Herschel finds evidence for stellar wind particles in a protostellar envelope: is this what happened to the young Sun?" by C. Ceccarelli et al. is published in The Astrophysical Journal Letters, July 2014. iopscience.iop.org/2041-8205/790/1/L1/article

ESA Herschel: key to discovery of spectacular gravitational lens

An irregular ring of radiation can be seen around the distant galaxy in the center of this 2.2-micron CCD photograph, made with the 10-meter Keck telescope on Hawaii. 

The lensing galaxy is associated with radio source 3C 220.3. 

The radiation of the ring originates from an extremely distant galaxy-in-formation and is a result of the gravitational-lens effect. 

Just below the lensing galaxy a neighboring galaxy can be seen, which also contributes to the lensing effects. 

Credit: ESA and the W. M. Keck Observatory.

An international team of astronomers including Dutch astronomers Peter Barthel and Léon Koopmans (University of Groningen) reports the discovery of a unique case of a cosmic gravitational lens.

Using several telescopes on the ground and in space, the scientists show that a distant radio galaxy, acting as a cosmic lens, distorts and magnifies the radiation of an even more distant mysterious dark object, thereby making that object visible.

Owing to the lens magnification, the faint background object becomes visible as a ring-like structure around the lensing foreground radio galaxy, seen well on an image made with one of the two 10-meter Keck telescopes on Hawaii.

Led by Martin Haas of Bochum University, Germany, the research started as rather simple observations with the Herschel Space Telescope of a sample of distant radio galaxies.

It rapidly grew into a project where crucial supplementary observations demonstrated the unique character of this cosmic lens.

While formally the Herschel Space Observatory did not discover this gravitational lens, it was the breakthrough Herschel performance that allowed the astronomers to measure the far-infrared emission of 3C 220.3, which in turn made them suspicious about its origin.

The original target, the very massive radio galaxy, emitted simply too much far-infrared radiation. Additional observations, with optical and radio telescopes, subsequently demonstrated unambiguously the cosmic lens effect of the radio galaxy making the dark background object visible in the far-infrared.

Astronomers have known of the cosmic gravitational lens phenomenon since 1979, although the light bending of distant stars by the Sun was already observed in 1919.

Calculations by Einstein in 1912 already predicted the existence of such cosmic lenses.

Gravitational lenses allow astronomers to investigate the properties of both the very distant lens and the even more distant object, a galaxy in the process of formation.

Modeling of the geometry of the lensing situation for instance demonstrated that the lensing galaxy which hosts the radio source contains an unexpectedly low fraction of mysterious dark matter compared with that predicted for large radio galaxies.

More information: 3C 220.3: A Radiogalaxy Lensing a Submillimeter Galaxy" by an international group of 20* astronomers led by Martin Haas (Ruhr University, Bochum, Germany) is accepted for publication in The Astrophysical Journal. Preprint: arxiv.org/abs/1406.2872

ESA Herschel Survey: Completion largest census of dust in local galaxies

Collage of galaxies in the Herschel Reference Survey at infrared /submillimetre wavelengths by Herschel (left) and at visible wavelengths from the Sloan Digital Sky Survey (SDSS, right).

The Herschel image is coloured with blue representing cold dust and red representing warm dust; the SDSS image shows young stars in blue and old stars in red. 

Together, the observations plot young, dust-rich spiral/irregular galaxies in the top left, with giant dust-poor elliptical galaxies in the bottom right.

ESA /Herschel /HRS-SAG2 and HeViCS Key Programmes /Sloan Digital Sky Survey / L. Cortese (Swinburne University)

The largest census of dust in local galaxies has been completed using data from ESA’s Herschel space observatory, providing a huge legacy to the scientific community.

Cosmic dust grains are a minor but fundamental ingredient in the recipe of gas and dust for creating stars and planets but despite its importance, there is an incomplete picture of the dust properties in galaxies beyond our own Milky Way.

Key questions include how the dust varies with the type of galaxy, and how it might affect our understanding of how galaxies evolve.

Before concluding its observations in April 2013, Herschel provided the largest survey of cosmic dust, spanning a wide range of nearby galaxies located 50–80 million light-years from Earth.

The catalogue contains 323 galaxies with varying star formation activity and different chemical compositions, observed by Herschel’s instruments across far-infrared and submillimetre wavelengths.

A sample of these galaxies is displayed in a collage, arranged from dust-rich in the top left to dust-poor in the bottom right.

The dust-rich galaxies are typically spiral or irregular, whereas the dust-poor ones are usually elliptical.

Blue and red colours represent cooler and warmer regions of dust, respectively.

Dust is gently heated across a range of temperatures by the combined light of all of the stars in each galaxy, with the warmest dust being concentrated in regions where stars are being born.

For comparison, the galaxies are also shown in visible light images obtained by the Sloan Digital Sky Survey SDSS.

Here, blue corresponds to young stars – hot, massive stars that burn through their fuel very quickly and are therefore short-lived.

Conversely, red stars are older population – they are less massive and cooler, and therefore live for longer.

The Herschel observations allow astronomers to determine how much light is emitted by the dust as a function of wavelength, providing a means to study the physical properties of the dust.

ESA Herschel Image: Star factory NGC 7538

Credit: ESA /Herschel /PACS /SPIRE. Acknowledgements: Cassie Fallscheer (University of Victoria), Mike Reid (University of Toronto) and the Herschel HOBYS team 

The billowing clouds portrayed in this image from ESA's Herschel observatory are part of NGC 7538, a stellar nursery for massive stars.

Located around 9000 light-years away, this is one of the few regions of massive-star formation that are relatively close to us, allowing astronomers to investigate this process in great detail.

Star factories like NGC 7538 consist mainly of hydrogen gas, but they also contain small amounts of cosmic dust.

It was through this minor – but crucial – component that ESA's Herschel could image these star-forming regions, because dust shines brightly at the far-infrared wavelengths that were probed by the observatory.

With a total mass of almost 400 000 Suns, NGC 7538 is an active factory where stars come to life – especially huge ones that are over eight times more massive than the Sun.

Hundreds of seeds of future stellar generations nestle in the mixture of surrounding gas and dust scattered across the image.

Once they reach a critical mass, they will ignite as stars.

Thirteen of these proto-stars have masses greater than 40 Suns, and are also extremely cold, less than –250ºC.

One group of stellar seeds seem to trace a ring-like structure, visible in the left part of the image.

The ring may be the edge of a bubble carved by previous stellar explosions – as stars reach the end of their lives and explode as dramatic supernovas – but astronomers are still investigating the origin of this peculiar arrangement.

The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 250 microns (red) and spans about 50 x 50 arc minutes. North is up and east is to the left.

More information: "Herschel reveals massive cold clumps in NGC 7538." C. Fallscheer, et al. C. Fallscheer et al. 2013 ApJ 773 102 The Astrophysical Journal Volume 773 Number 2. DOI: 10.1088/0004-637X/773/2/102.

Herschel: SMA unveils how small cosmic seeds in Snake nebula grow into big stars

These two panels show the Snake nebula as photographed by the Spitzer and Herschel space telescopes. 

At mid-infrared wavelengths (the upper panel taken by Spitzer), the thick nebular material blocks light from more distant stars. 

At far-infrared wavelengths, however (the lower panel taken by Herschel), the nebula glows due to emission from cold dust. 

The two boxed regions, P1 and P6, were examined in more detail by the Submillimeter Array. 

Credit: Spitzer /GLIMPSE /MIPS, Herschel /HiGal, Ke Wang, European Southern Observatory

New images from the Smithsonian's Submillimeter Array (SMA) telescope provide the most detailed view yet of stellar nurseries within the Snake nebula.

These images offer new insights into how cosmic seeds can grow into massive stars.

Stretching across almost 100 light-years of space, the Snake nebula is located about 11,700 light-years from Earth in the direction of the constellation Ophiuchus.

In images from NASA's Spitzer Space Telescope it appears as a sinuous, dark tendril against the starry background. It was targeted because it shows the potential to form many massive stars (stars heavier than 8 times our Sun).

"To learn how stars form, we have to catch them in their earliest phases, while they're still deeply embedded in clouds of gas and dust, and the SMA is an excellent telescope to do so," explained lead author Ke Wang of the European Southern Observatory (ESO), who started the research as a predoctoral fellow at the Harvard-Smithsonian Center for Astrophysics (CfA).

The team studied two specific spots within the Snake nebula, designated P1 and P6. Within those two regions they detected a total of 23 cosmic "seeds" - faintly glowing spots that will eventually birth one or a few stars.

The seeds generally weigh between 5 and 25 times the mass of the Sun, and each spans only a few thousand astronomical units (the average Earth-Sun distance).

The sensitive, high-resolution SMA images not only unveil the small seeds, but also differentiate them in age.

Previous theories proposed that high-mass stars form within very massive, isolated "cores" weighing at least 100 times the mass of the Sun.

These new results show that that is not the case. The data also demonstrate that massive stars aren't born alone but in groups.

"High-mass stars form in villages," said co-author Qizhou Zhang of the CfA. "It's a family affair."

The team also was surprised to find that these two nebular patches had fragmented into individual star seeds so early in the star formation process.

They detected bipolar outflows and other signs of active, ongoing star formation. Eventually, the Snake nebula will dissolve and shine as a chain of several star clusters.

ESA Herschel: Crab Nebula

This image shows a composite view of the Crab nebula, an iconic supernova remnant in our Milky Way galaxy, as viewed by the Herschel Space Observatory and the Hubble Space Telescope. 

Herschel is a European Space Agency (ESA) mission with important NASA contributions, and Hubble is a NASA mission with important ESA contributions.

A wispy and filamentary cloud of gas and dust, the Crab nebula is the remnant of a supernova explosion that was observed by Chinese astronomers in the year 1054.

The image combines Hubble's view of the nebula at visible wavelengths, obtained using three different filters sensitive to the emission from oxygen and sulphur ions and is shown here in blue. Herschel's far-infrared image reveals the emission from dust in the nebula and is shown here in red.

While studying the dust content of the Crab nebula with Herschel, a team of astronomers have detected emission lines from argon hydride, a molecular ion containing the noble gas argon. This is the first detection of a noble-gas based compound in space.

The Herschel image is based on data taken with the Photoconductor Array Camera and Spectrometer (PACS) instrument at a wavelength of 70 microns; the Hubble image is based on archival data from the Wide Field and Planetary Camera 2 (WFPC2).

Image credit: ESA/Herschel/PACS/MESS Key Programme Supernova Remnant Team; NASA, ESA and Allison Loll/Jeff Hester (Arizona State University)

ESA Herschel Video: 37 thousand science observations

This animation shows the timeline of over 37 000 scientific observations made by ESA's Herschel space observatory throughout its entire mission, condensed into less than a minute.

The animation was prepared by Pedro Gómez-Alvarez in the Herschel Science Centre Community Support Group and presented by Herschel's Project Scientist Göran Pilbratt during the opening session of The Universe Explored by Herschel symposium held at ESA's ESTEC facility, in Noordwijk, the Netherlands, last month.

The animation runs from launch, on 14 May 2009, until the infrared observatory made its last observation on 29 April 2013.

Running through the centre of the graphic is the 'ecliptic plane' tracing the paths of the planets with respect to Herschel's viewpoint from its orbit around L2, which is located 1.5 million kilometres behind the Earth as viewed from the Sun.

A horseshoe shape marks the Galactic Plane, the direction in which much of the Milky Way's mass lies, and where many of Herschel's observations were focused.

In total, Herschel observed almost a tenth of the entire sky for over 23 500 hours, providing new views into the previously hidden Universe, pointing to unseen star birth and galaxy formation, and tracing water through the Universe from molecular clouds to newborn stars and to their planet-forming discs and belts of comets.

Its two camera/imaging spectrometers, PACS (Photoconductor Array Camera and Spectrometer) and SPIRE (Spectral and Photometric Imaging Receiver), which together covered wavelengths of 55–670 microns, provided about two thirds of Herschel's sky coverage in parallel imaging mode.

These data points are shown in yellow. PACS and SPIRE photometry observations are indicated in blue and green, which together with spectroscopy performed with PACS, SPIRE and the third science instrument, HIFI (Heterodyne Instrument for the Far Infrared, covering wavelength bands of 157–212 microns and 240–625 microns) make up the remainder.

ESA Herschel throws new light on oldest cosmic light

photons in the Cosmic Microwave Background (CMB)

This illustration shows how photons in the Cosmic Microwave Background (CMB) are deflected by the gravitational lensing effect of massive cosmic structures as they travel across the Universe. 

Using data from ESA's Planck satellite, cosmologists have been able to measure this gravitational lensing of the CMB over the whole sky for the first time. 

Credit: ESA and the Planck Collaboration

Cosmologists have achieved a first detection of a long-sought component in the Cosmic Microwave Background (CMB).

This component, known as B-mode polarisation, is caused by gravitational lensing, the bending of light by massive structures as it travels across the Universe.

The result is based on the combination of data from the South Pole Telescope and ESA's Herschel Space Observatory.

This detection is a milestone along the way to the possible discovery of another kind of B-mode signal in the polarised CMB - a signal produced by gravitational waves less than a second after the Universe began.

The Cosmic Microwave Background is the most ancient light that has travelled almost unimpeded across the Universe, and it contains a wealth of information about the origin and nature of the cosmos.

During their journey, photons from the CMB have encountered a multitude of galaxies and galaxy clusters and have been deflected by these large concentrations of matter.

This phenomenon, known as gravitational lensing, imprints a subtle distortion on the pattern of the CMB that encodes details about the large-scale distribution of structure in the Universe.

In recent years, cosmologists have detected the signature of gravitational lensing on the CMB temperature using data from ground-based and space-borne experiments, including the first all-sky image of this effect achieved using ESA's Planck satellite.

A small portion of the CMB is polarised, and gravitational lensing also affects this part of the signal. In fact, the polarised CMB is an additional and even richer treasure trove than the unpolarised signal to use to explore the Universe's past.

Now a team of cosmologists studying the polarised CMB has detected in it the signature of gravitational lensing, opening new and exciting possibilities to study the distribution of matter across the cosmos.

This result is also the first detection of the elusive second component of the CMB polarisation – the long-sought B-modes.

The study is based on the combination of data from SPTpol, the polarisation-sensitive receiver on the National Science Foundation's South Pole Telescope (SPT), and the SPIRE instrument on board ESA's Herschel Space Observatory.

The SPT is a ground-based telescope, located in Antarctica, to observe the CMB to very high angular resolution in a small patch of the southern sky.

ESA Herschel Image: Embracing Orion

Orion A. Credit: ESA/Herschel/ Ph. André, V. Könyves, N. Schneider (CEA Saclay, France) for the Gould Belt survey Key Programme

This new view of the Orion A star-formation cloud from ESA's Herschel space observatory shows the turbulent region of space that hugs the famous Orion Nebula.

The nebula lies about 1500 light years from Earth within the 'sword of Orion' – below the three main stars that form the belt of the Orion constellation.

In this view, the nebula corresponds to the brightest region in the centre of the image, where it is lit up by the Trapezium group of stars at its heart.

The scene is awash with turbulent star formation, the fierce ultraviolet radiation of massive new born stars blasting away their surrounding cloudy cocoons, carving ethereal shapes into the gas and dust.

Wispy tendrils rise like flames away from some of the most intense regions of star formation, while pillars of denser material withstand the searing blaze for longer.

Great arms of gas and dust extend from the Orion Nebula to form a ring, while a spine of cooler material weaves up through the scene to a halo of cloudy star-formation material above.

Embedded within the red and yellow filaments are a handful of point-like sources: these are protostars, the seeds of new stars that will soon ignite and begin to flood their surrounds with intense radiation.

The black regions to the top of the image and to the bottom right may seem like voids, but actually contain hints of much fainter emission that has not been emphasised in this image.

The red 'islands' of emission in the bottom right are also a subtle trick of image processing for they are connected to the main cloud by much fainter emission.

The bright 'eyes' in the two most distinct clouds indicates that the tip of each pillar has already collapsed and is forming stars.

Astronomers witness birth of Milky Way's most massive star

a) Mid-infrared Spitzer composite image. 

b) Herschel column density image of SDC335. 

c) ALMA 3.2 mm dust continuum emission of the central region of SDC335 where two cores are identified, MM1 and MM2. 

Credit: A&A 555, A112 (2013)

Scientists have observed in unprecedented detail the birth of a massive star within a dark cloud core about 10,000 light years from Earth.

The team used the new ALMA (Atacama Large Millimetre/submillimetre Array) telescope in Chile – the most powerful radio telescope in the world – to view the stellar womb which, at 500 times the mass of the Sun and many times more luminous, is the largest ever seen in our galaxy.

The researchers say their observations – to be published in the journal Astronomy and Astrophysics – reveal how matter is being dragged into the centre of the huge gaseous cloud by the gravitational pull of the forming star – or stars – along a number of dense threads or filaments.

"The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud," said lead author Dr Nicolas Peretto, from Cardiff University.

"We wanted to see how monster stars form and grow, and we certainly achieved our aim. One of the sources we have found is an absolute giant—the largest protostellar core ever spotted in the Milky Way!

"Even though we already believed that the region was a good candidate for being a massive star-forming cloud, we were not expecting to find such a massive embryonic star at its centre. This cloud is expected to form at least one star 100 times more massive than the Sun and up to a million times brighter. Only about one in 10,000 of all the stars in the Milky Way reach that kind of mass."

Different theories exist as to how these massive stars form but the team's findings lend weight to the idea that the entire cloud core begins to collapse inwards, with material raining in towards the centre to form one or more massive stars.

Co-author Professor Gary Fuller, from The University of Manchester, said: "Not only are these stars rare, but their births are extremely rapid and childhood short, so finding such a massive object so early in its evolution in our Galaxy is a spectacular result.

More information: 'Global collapse of molecular clouds as a formation mechanism for the most massive stars,' Astronomy & Astrophysics, www.aanda.org/articles/aa/pdf/2013/07/aa21318-13.pdf

Goodbye Herschel: Closing views of an icon

Herschel observed from the ground. 

Credit: N. Howes /E. Guido /Faulkes Telescope /LCOGT

This tiny dot against the streaking star field is one of the last views that ground-based observers will see of ESA's iconic Herschel space observatory.

Herschel spent over three years taking stunning images of the Universe in far infrared wavelengths, but in April the spacecraft depleted the last of its helium coolant, concluding science operations.

After this, the spacecraft operations team performed a series of engineering tests. A series of thruster burns moved it from its orbit around the L2 point 1.5 million kilometres from the Earth, and into a heliocentric orbit. Finally, in June, the spacecraft was switched off.

As well as being tracked by ESA ground stations throughout its mission, amateur astronomers have also enjoyed spotting the spacecraft.

Last week, as Herschel began moving away from Earth, astronomers Nick Howes and Ernesto Guido from the Remanzacco Observatory used the 2m diameter Faulkes Telescope North in Hawaii to image the spacecraft.

The observation was a particular challenge as the final manoeuvres made by the ESA flight control team resulted in the observatory being at a slightly different position on the sky compared to that predicted by existing orbital data.

But the imaging campaign was successful, as seen in the image presented here, with Herschel indicated by the two lines to the right of centre.

Stars appear as streaks because the astronomers were tracking the motion of Herschel through the sky.

Herschel's new orbit will send it around the Sun, coming back into Earth's neighbourhood around 13 years from now.

Determining an accurate orbit now is important, because its increasing distance will make it fainter and much harder to keep track of, in the intervening years.

ESA Herschel telescope: Fuel Tanks emptied and shut down

ESA's billion-euro Herschel space telescope has been shut down.

Controllers on Monday emptied the satellite's fuel tanks and commanded the observatory to sever all communications.

The "passivated" spacecraft is now in a slow drift around the Sun, about 2.14 million km from Earth.

With its 3.5m mirror and three state-of-the-art instruments, Herschel was the most powerful observatory of its kind ever put in space.

In its four years of operations, it gathered pictures and other data at far-infrared wavelengths that have transformed our understanding of star formation and galaxy evolution.

The final command to turn off the communications transponder was sent from the European Space Operations Centre (Esoc) in Darmstadt, Germany, at 12:25 GMT.

The great distance to Herschel meant it took six seconds for the radio message to reach the observatory and a further six seconds for ground stations on Earth to confirm the loss of signal.

Micha Schmidt

"It really was a beautiful spacecraft," said Micha Schmidt, the European Space Agency's (Esa) Herschel spacecraft operations manager.

"It never gave us too much trouble. And that allowed us to streamline things; to learn a lot about pointing the spacecraft, for example. This meant we could maximise the science," he told reporters.

Empty tanks
Decommissioning became necessary when Herschel used up the last of its superfluid helium coolant.

This had maintained the efficient working of the instruments and their detectors, which needed to be kept just fractions of a degree above absolute zero.

When the helium ran dry, Herschel was effectively blind to the objects it wanted to see on the sky.

End-of-life actions involved moving the satellite from its observation station, a gravitational "sweetspot" about 1.5 million km on the "nightside" of the Earth known as the second Lagrangian point (L2).

This will keep the 7m-long spacecraft well clear of other astronomy missions that want to use L2's very stable temperature and light conditions.

Controllers also emptied Herschel's hydrazine propellant tanks to reduce the risk of future explosion.

This involved commanding the satellite to fire its thrusters to exhaustion.

As Herschel drifts, probably in a slow tumble, it will continue to charge its batteries and provide power to the onboard computer.

"In normal circumstances, there is an automatic recovery function whereby Herschel would try to switch on the transponder, but we have overridden this," said Mr Schmidt.

"It will never contact Earth again. We could re-command it. This mode is hardwired and we can't overcome this. But we have no intention of doing that."

Next up
Although the spacecraft operation phase may be over, the huge amount of data acquired by Herschel means that the science phase is only now getting into its stride.

Astronomers will continue to scrutinise Herschel's pictures and make discoveries long into the future.

Many of its observations will also be followed up by other telescopes that are able to see some of the same wavelengths of lights. Among them is the ESO giant new Alma radio network in Chile.

"Herschel has been so impressive and its scientific discoveries will continue for a decade at least, if not longer. When you have a cryogenic telescope like this, you almost have to rush because you know it will operate only for a finite time - you have to get all your observations done as fast as you can. But then you go through the data and we will be doing that for a very long time to come," said Prof Alvaro Gimenez, Esa's science director.

"Herschel has taught us so much about stars and planets in our own galaxy. It has shown us how many stars form along great filaments [of gas and dust]. That's something we simply didn't know before," he told reporters at the Paris Air Show.

Herschel was launched in 2009 with the Planck Surveyor, which was also stationed at L2.

This telescope, which has been studying the "oldest light" in the Universe, is expected to end its mission around October and will be passivated in the same way as its sibling.

Esa's next mission to the Lagrangian point will be Gaia.

Scheduled to launch in September, this space telescope will make the most precise map yet of the stars in our Milky Way Galaxy.

ESA Herschel Detects more gas in the Galaxy than constructed by astronomers

Artist's impression of molecular gas across the Milky Way's plane. Credit: ESA - C. Carreau

A survey from ESA Herschel has revealed that the reservoir of molecular gas in the Milky Way is hugely underestimated - almost by one third - when it is traced with traditional methods.

Monitoring the emission from ionised carbon, the new study identified molecular gas in the intermediate evolutionary stage between diffuse, atomic gas and the densest star-forming molecular clouds.

The discovery not only indicates that there is more raw material for the formation of new stars in the Galaxy, but also that it extends farther than astronomers knew.

In the Milky Way, as well as in other galaxies, stars are born from the collapse of the densest and coldest clumps of matter in a molecular cloud.

These clouds are gigantic star-forming complexes consisting mainly of molecular hydrogen (H2), a gas that does not emit any light at the low temperatures found in molecular clouds.

Astronomers investigating the early stages of star formation are not only interested in how molecular clouds fragment to form stars, but also in the processes that take place even earlier and initially cause molecular clouds to take shape from diffuse, atomic hydrogen gas.

For this purpose, astronomers study the distribution and properties of H2 across the Galaxy – but without the benefit of direct observations, they must resort to alternative methods to trace it.

The most widely used proxy to track down molecular gas in star-forming regions is carbon monoxide (CO).

A mere contaminant in molecular clouds, CO radiates much more efficiently than H2 and can be detected easily.

However, such indirect tracers can be biased, since there is no guarantee that all portions of a cloud containing H2 also contain CO, in which case observations of CO would miss these regions entirely.

To achieve a more complete picture of the Milky Way's molecular content, astronomers in the past decades have combined observations of CO with other tracers of H2.

These include the emission from dust – another contaminant in molecular clouds – and the gamma rays that are produced when cosmic ray particles interact with atomic and molecular hydrogen in the interstellar medium (ISM).

The combination of such data had suggested the presence of more molecular gas in the Milky Way than indicated by CO alone.

New data from ESA's Herschel Space Observatory are now confirming this earlier suspicion: almost one third of all molecular gas in the Milky Way had remained undetected.

Jorge Pineda

In addition, there is more: the new survey, which probes H2 through a different tracer – ionised carbon (C+) – has established the three-dimensional distribution of the molecular gas across the Milky Way.

"This is the first survey of ionised carbon across the Galactic Plane – where most of the Milky Way's stars and star-forming clouds are concentrated – that combines both high spectral and angular resolution," comments Jorge Pineda from the Jet Propulsion Laboratory (JPL), Caltech, USA, who led the study.

Read more here

More information: Technical paper: J. L. Pineda, et al., "A Herschel [C II] Galactic plane survey I: the global distribution of ISM gas components", 2013, Astronomy & Astrophysics, 554, A103. arxiv.org/abs/1304.7770 and dx.doi.org/10.1051/0004-63
61/201321188

ESA Herschel: Shining a light on cool pools of gas in the galaxy

This illustration shows a newfound reservoir of stellar fuel discovered by the Herschel space observatory (red). 

Credit: ESA/NASA/JPL-Caltech

Newly formed stars shine brightly, practically crying out, "Hey, look at me!" But not everything in our Milky Way galaxy is easy to see.

The bulk of material between the stars in the galaxy -- the cool hydrogen gas from which stars spring -- is nearly impossible to find.

A new study from the Hershel Space Observatory, a European Space Agency mission with important NASA participation, is shining a light on these hidden pools of gas, revealing their whereabouts and quantities.

In the same way that dyes are used to visualize swirling motions of transparent fluids, the Herschel team has used a new tracer to map the invisible hydrogen gas.

The discovery reveals that the reservoir of raw material for making stars had been underestimated before -- almost by one third -- and extends farther out from our galaxy's center than known before.

Jorge Pineda

"There is an enormous additional reservoir of material available to form new stars that we couldn't identify before," said Jorge Pineda of NASA's Jet Propulsion Laboratory, Pasadena, Calif., lead author of a new paper on the findings published in the journal Astronomy and Astrophysics.

"We had to go to space to solve this mystery because our atmosphere absorbs the specific radiation we wanted to detect," said William Langer of JPL, principal investigator of the Herschel project to map the gas.

"We also needed to see far-infrared light to pinpoint the location of the gas. For both these reasons, Herschel was the only telescope for the job."

Stars are created from clouds of gas, made of hydrogen molecules. The first step in making a star is to squeeze gas together enough that atoms fuse into molecules.

William Langer

The gas starts out sparse but, through the pull of gravity and sometimes other constricting forces, it collects and becomes denser.

When the hydrogen gets dense enough, nuclear fusion takes place and a star is born, shining with starlight.

Astronomers studying stars want to follow this journey, from a star's humble beginnings as a cloud of molecules to a full-blown blazing orb.

To do so requires mapping the distribution of the stellar hydrogen fuel across the galaxy.

Unfortunately, most hydrogen molecules in space are too cold to give off any visible light. They lurk unseen by most telescopes.

For decades, researchers have turned to a tracer molecule called carbon monoxide, which goes hand-in-hand with the hydrogen molecules, revealing their location, but this method has limitations.

In regions where the gas is just beginning to pool -- the earliest stage of cloud formation -- there is no carbon monoxide.

"Ultraviolet light destroys the carbon monoxide," said Langer. "In the space between stars, where the gas is very thin, there is not enough dust to shield molecules from destruction by ultraviolet light."

A different tracer -- ionized carbon -- does, however, linger in these large but relatively empty spaces, and can be used to pin down the hydrogen molecules.

Researchers have observed ionized carbon from space before, but Herschel has, for the first time, provided a dramatically improved geographic map of its location and abundance in the galaxy.

"Thanks to Herschel's incredible sensitivity, we can separate material moving at different speeds," said Paul Goldsmith, a co-author and the NASA Herschel Project Scientist at JPL. "We finally can get the whole picture of what's available to make future generations of stars."

Read a more in-depth story about this research from the European Space Agency at http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51909 .

The technical paper is online at http://arxiv.org/abs/1304.7770

Herschel captures image of NGC 6334 the Cat's Paw Nebula

In this false-colour image of NGC 6334, red represents the Herschel 70 micron IR image, green represents the IRAC 8 micron image and blue represents the NEWFIRM 1 micron J band. 

The region is about 70 light years wide.

CREDIT: S. Willis (CfA+ISU); ESA/Herschel; NASA/JPL-Caltech/ Spitzer; CTIO/NOAO/AURA/NSF.

A nebula that shines about 5,500 light-years from Earth could be going through a "baby boom," according to a new study.

NGC 6334 (the Cat's Paw Nebula) might be one of the most productive star-forming regions in the Milky Way.

The nebula is home to tens of thousands of newly formed stars and plays host to about 200,000 suns' worth of star-creating material.

"NGC 6334 is forming stars at a more rapid pace than Orion — so rapidly that it appears to be undergoing what might be called a burst of star formation," the study's lead author Sarah Willis of the Harvard-Smithsonian Center for Astrophysics (CfA) and Iowa State University said in a statement.

"It might resemble a 'mini-starburst,' similar to a scaled-down version of the spectacular bursts sometimes seen in other galaxies."

More than 2,000 of the stars in the nebula are very young and are still trapped inside the "dusty cocoons" that birthed them, scientists said.

Willis presented the new findings here today (June 5) at the 222nd meeting of the American Astronomical Society.

Astronomers have observed distant, bright starbursting galaxies before, but because the Cat's Paw Nebula is a region within the Milky Way, scientists can get a better sense of why starburst regions might form and what they look like closer-up.

"Because NGC 6334 is nearby, astronomers can probe it in much greater detail, even down to counting the numbers of individual stars of various types and ages," CfA officials wrote.

Astronomers are still trying to investigate the origin of the starburst. Some researchers think that a blast from a supernova explosion or galactic collisions could create starbursts; however, neither of those explanations appear to explain the Cat's Paw Nebula's recent activity.

Scientists expect that the starburst will last for a relatively short amount of time in cosmic terms. In total, NGC 6334's burst will probably endure for only a few million years.

"We’re lucky, not only because it’s nearby but also because we’re catching it while the starburst is happening," Willis said.

ESA Herschel: Revealing Milky Way's warm heart

What heats gas near supermassive black holes at the centre of galaxies? 

Astronomers have looked at the centre of our Galaxy, the Milky Way, with ESA's Herschel Space Observatory and discovered a rich variety of molecules at surprisingly high temperatures - up to 1000 K. 

The new data suggest that the molecular gas is heated up by shocks, in addition to ultraviolet radiation from massive stars close to the Galactic Centre. 

Shocks develop in the gas as the material surges towards Sagittarius A*, the region harbouring the supermassive black hole at the heart of the Milky Way.

About 26 000 light-years away, the central region of the Galaxy, known as Sagittarius A*, or Sgr A*, hosts the closest super-massive black hole to Earth.

With an estimated mass equivalent to about four million times that of our Sun, this black hole currently accretes matter from its surroundings at a very gentle pace, like the majority of super-massive black holes in massive galaxies across the Universe.

A few hundred times closer to Earth than the nearest galaxy hosting an actively accreting black hole, Sgr A* provides a unique chance to study the environment of super-massive black holes in great detail.

However, we observe the Galactic Centre through the dense disc of the Milky Way, where gas and dust in the spiral arms of the Galaxy absorb visible light.

The best way to study the interstellar material around Sgr A* is thus via infrared and radio observations.

New research based on spectroscopic data from ESA's Herschel Space Observatory has resolved the innermost portion of the Milky Way – a few light-years around Sgr A* – for the first time at far-infrared wavelengths.

The team of astronomers, led by Javier Goicoechea from the Centro de Astrobiología in Madrid, Spain, was able to isolate the far-infrared emission from all the interstellar components that surround Sgr A* – neutral atomic, molecular and ionised gas, as well as dust.

Javier Goicoechea

In particular, they exploited the characteristic signature from several molecules to trace the temperature, density and other properties of the material that orbits the central black hole and is possibly falling onto it.

"We detected a surprisingly rich variety of molecules in the environment of Sgr A* that really exceeded our expectations," comments Goicoechea.

"The molecules range from highly excited carbon monoxide and water vapour, to hydrogen cyanide and many light molecules that play a critical role in the chemistry of the interstellar medium. Some of them had not been detected before Herschel," he adds.

More information on ESA Herschel site here

ESA Herschel Captures Infra-red Image of Horsehead Nebula

Credit: ESA/Herschel /PACS, SPIRE/N. Schneider, Ph. André, V. Könyves (CEA Saclay, France) for the “Gould Belt survey” Key Programme

Wednesday, May 1, 2013: A new view shows the Horsehead Nebula in the context of its surroundings. 

The nebula resides in the constellation Orion, about 1300 light-years away, which makes up part of the vast Orion Molecular Cloud complex. 

Flame Nebula

The nebula appears to poke its horse’s head shape above the surrounding gas and dust at the far right-hand side, pointing towards the Flame Nebula. 

Intense radiation streaming away from newborn stars heats up the surrounding dust and gas (pink and white). 

To the left lie two other star formation sites, NGC 2068 and NGC 2071 (Messier 78). 

Cool gas and dust networks weave throughout the scene as red and yellow filaments. Some of these may host newly forming low-mass stars.

ESA Herschel: Deep-space Infra-red telescope runs out of Helium Coolant

Europe's deep-space Herschel telescope has given up the ghost -- running out of coolant after a successful mission to observe the birth of stars and galaxies, the European Space Agency said Monday.

"Herschel has made over 35,000 scientific observations, amassing more than 25,000 hours' worth of science data from about 600 observing programmes," it said in a eulogy.

"The archive will become the legacy of the mission. It is expected to provide even more discoveries than have been made during the lifetime of the Herschel mission."

Launched in May 2009, Herschel carried 2,300 litres of liquid helium coolant, which has been slowly evaporating.

Herschel became the largest and most powerful infrared telescope in space. Its expected lifetime was 3.5 years.

The helium was used to cool the satellite's instruments to near absolute zero (minus 273.15 degrees Celsius or minus 459.67 degrees Fahrenheit) to enable it to make its observations.

At 7.5 metres (24.3 feet) high and four metres (13 feet) wide, Herschel had a launch mass of 3.4 tonnes. It cost 1.1 billion euros ($1.4 billion)

It was named after Sir William Herschel, the German-born British astronomer who discovered Uranus in 1781 and infrared radiation in 1800.

It carried three cameras and spectrometers and a primary mirror 3.5 metres (11.37 feet) across -- able to collect almost 20 times more light than any previous infrared space telescope.

Its infrared technology allowed Herschel to see galaxies that were previously hidden from scientists' view by cosmic dust clouds.

In 2011, it was reported that Herschel found the first confirmed evidence of oxygen molecules in space.

"Herschel has offered us a new view of the hitherto hidden Universe, pointing us to a previously unseen process of star birth and galaxy formation, and allowing us to trace water through the Universe from molecular clouds to newborn stars and their planet-forming discs and belts of comets," said Goran Pilbratt, an ESA Herschel Project Scientist.

The telescope will still be able to communicate with its ground stations for some time, placed in a "parking orbit" around the Sun.

ESA's Herschel space observatory links Jupiter's water to comet impact

Credit: Shoemaker-Levy 9 impact site G

ESA's Herschel space observatory has solved a long-standing mystery as to the origin of water in the upper atmosphere of Jupiter, finding conclusive evidence that it was delivered by the dramatic impact of comet Shoemaker-Levy 9 in July 1994.

During the spectacular week-long collision, a string of 21 comet fragments pounded into the southern hemisphere of Jupiter, leaving dark scars in the planet's atmosphere that persisted for several weeks.

The remarkable event was the first direct observation of an extraterrestrial collision in the Solar System. It was followed worldwide by amateur and professional astronomers with many ground-based telescopes and the NASA/ESA Hubble Space Telescope.



ESA's Infrared Space Observatory was launched in 1995 and was the first to detect and study water in Jupiter's upper atmosphere. It was widely speculated that comet Shoemaker-Levy 9 may have been the origin of this water, but direct proof was missing.

Scientists were able to exclude an internal source, such as water rising from deeper within the planet's atmosphere, because it is not possible for water vapour to pass through the 'cold trap' that separates the stratosphere from the visible cloud deck in the troposphere below.

Thus the water in Jupiter's stratosphere must have been delivered from outside. But determining its origin had to wait more than 15 years, until Herschel used its sensitive infrared eyes to map the vertical and horizontal distribution of water's chemical signature.

Water in Jupiter’s atmosphere.

Herschel's observations found that there was 2–3 times more water in the southern hemisphere of Jupiter than in the northern hemisphere, with most of it concentrated around the sites of the 1994 comet impact.

Additionally, it is only found at high altitudes.

"Only Herschel was able to provide the sensitive spectral imaging needed to find the missing link between Jupiter's water and the 1994 impact of comet Shoemaker-Levy 9," says Thibault Cavalié of the Laboratoire d'Astrophysique de Bordeaux, lead author of the paper published in Astronomy and Astrophysics.

"According to our models, as much as 95% of the water in the stratosphere is due to the comet impact."

This shows an abundance of water in Jupiter's stratosphere. 

The north-south asymmetry is clearly observed. 

The green and red areas correspond to the highest abundances. 

Credit: Astronomy & Astrophysics, Cavalié et al. 2013, A&A, 553, A21 

Another possible source of water would be a steady rain of small interplanetary dust particles onto Jupiter.

But, in this case, the water should be uniformly distributed across the whole planet and should have filtered down to lower altitudes.

Also, one of Jupiter's icy moons could deliver water to the planet via a giant vapour torus, as Herschel has seen from Saturn's moon Enceladus, but this too has been ruled out.

None of Jupiter's large moons is in the right place to deliver water to the locations observed.

Finally, the scientists were able to rule out any significant contributions from recent small impacts spotted by amateur astronomers in 2009 and 2010, along with local variations in the temperature of Jupiter's atmosphere. Shoemaker-Levy 9 is the only likely culprit.