Thursday, April 26, 2018

Gaia creates richest star map of our Galaxy and beyond

Gaia’s sky in colour
Copyright ESA/Gaia/DPAC

ESA’s Gaia mission has produced the richest star catalogue to date, including high-precision measurements of nearly 1.7 billion stars and revealing previously unseen details of our home Galaxy.

A multitude of discoveries are on the horizon after this much awaited release, which is based on 22 months of charting the sky. The new data includes positions, distance indicators and motions of more than one billion stars, along with high-precision measurements of asteroids within our Solar System and stars beyond our own Milky Way Galaxy.

Preliminary analysis of this phenomenal data reveals fine details about the make-up of the Milky Way’s stellar population and about how stars move, essential information for investigating the formation and evolution of our home Galaxy.

The Galactic census takes shape
Copyright: ESA/Gaia/DPAC

“Gaia is an ambitious mission that relies on a huge human collaboration to make sense of a large volume of highly complex data. It demonstrates the need for long-term projects to guarantee progress in space science and technology and to implement even more daring scientific missions of the coming decades.” 

Gaia was launched in December 2013 and started science operations the following year. The first data release, based on just over one year of observations, was published in 2016; it contained distances and motions of two million stars. 

The new data release, which covers the period between 25 July 2014 and 23 May 2016, pins down the positions of nearly 1.7 billion stars, and with a much greater precision. For some of the brightest stars in the survey, the level of precision equates to Earth-bound observers being able to spot a Euro coin lying on the surface of the Moon.  

With these accurate measurements it is possible to separate the parallax of stars – an apparent shift on the sky caused by Earth’s yearly orbit around the Sun – from their true movements through the Galaxy.

The new catalogue lists the parallax and velocity across the sky, or proper motion, for more than 1.3 billion stars. From the most accurate parallax measurements, about ten per cent of the total, astronomers can directly estimate distances to individual stars.

“The second Gaia data release represents a huge leap forward with respect to ESA’s Hipparcos satellite, Gaia’s predecessor and the first space mission for astrometry, which surveyed some 118 000 stars almost thirty years ago,” says Anthony Brown of Leiden University, The Netherlands.

Anthony is the chair of the Gaia Data Processing and Analysis Consortium Executive, overseeing the large collaboration of about 450 scientists and software engineers entrusted with the task of creating the Gaia catalogue from the satellite data.

Gaia’s first and second data releases
Copyright: ESA/Gaia/DPAC
Access the video

“The sheer number of stars alone, with their positions and motions, would make Gaia’s new catalogue already quite astonishing,” adds Anthony. 

“But there is more: this unique scientific catalogue includes many other data types, with information about the properties of the stars and other celestial objects, making this release truly exceptional.”

Asteroid survey
Copyright: ESA/Gaia/DPAC   
Something for everyone

The comprehensive dataset provides a wide range of topics for the astronomy community.

As well as positions, the data include brightness information of all surveyed stars and colour measurements of nearly all, plus information on how the brightness and colour of half a million variable stars change over time. It also contains the velocities along the line of sight of a subset of seven million stars, the surface temperatures of about a hundred million and the effect of interstellar dust on 87 million.

Gaia also observes objects in our Solar System: the second data release comprises the positions of more than 14 000 known asteroids, which allows precise determination of their orbits. A much larger asteroid sample will be compiled in Gaia’s future releases.

Further afield, Gaia closed in on the positions of half a million distant quasars, bright galaxies powered by the activity of the supermassive black holes at their cores. These sources are used to define a reference frame for the celestial coordinates of all objects in the Gaia catalogue, something that is routinely done in radio waves but now for the first time is also available at optical wavelengths.

Cosmic scales covered by Gaia 
Copyright: ESA, CC BY-SA 3.0 IGO

Major discoveries are expected to come once scientists start exploring Gaia’s new release. An initial examination performed by the data consortium to validate the quality of the catalogue has already unveiled some promising surprises – including new insights on the evolution of stars.

Gaia’s Hertzsprung-Russell diagram
Copyright ESA/Gaia/DPAC

Galactic archaeology

“The new Gaia data are so powerful that exciting results are just jumping at us,” says Antonella Vallenari from the Istituto Nazionale di Astrofisica (INAF) and the Astronomical Observatory of Padua, Italy, deputy chair of the data processing consortium executive board.

“For example, we have built the most detailed Hertzsprung-Russell diagram of stars ever made on the full sky and we can already spot some interesting trends. It feels like we are inaugurating a new era of Galactic archaeology.”

Named after the two astronomers who devised it in the early twentieth century, the Hertzsprung-Russell diagram compares the intrinsic brightness of stars with their colour and is a fundamental tool to study populations of stars and their evolution.

A new version of this diagram, based on four million stars within five thousand light-years from the Sun selected from the Gaia catalogue, reveals many fine details for the first time. This includes the signature of different types of white dwarfs – the dead remnants of stars like our Sun – such that a differentiation can be made between those with hydrogen-rich cores and those dominated by helium.

Combined with Gaia measurements of star velocities, the diagram enables astronomers to distinguish between various populations of stars of different ages that are located in different regions of the Milky Way, such as the disc and the halo, and that formed in different ways. Further scrutiny suggests that the fast-moving stars thought to belong to the halo encompass two stellar populations that originated via two different formation scenarios, calling for more detailed investigations.

“Gaia will greatly advance our understanding of the Universe on all cosmic scales,” says Timo Prusti, Gaia project scientist at ESA.

“Even in the neighbourhood of the Sun, which is the region we thought we understood best, Gaia is revealing new and exciting features.”

Rotation of the Large Magellanic Cloud
Copyright: ESA/Gaia/DPAC 

Galaxy in 3D

For a subset of stars within a few thousand light-years of the Sun, Gaia has measured the velocity in all three dimensions, revealing patterns in the motions of stars that are orbiting the Galaxy at similar speeds.

Future studies will confirm whether these patterns are linked to perturbations produced by the Galactic bar, a denser concentration of stars with an elongated shape at the centre of the Galaxy, by the spiral arm architecture of the Milky Way, or by the interaction with smaller galaxies that merged with it billions of years ago.

At Gaia’s precision, it is also possible to see the motions of stars within some globular clusters – ancient systems of stars bound together by gravity and found in the halo of the Milky Way – and within our neighbouring galaxies, the Small and Large Magellanic Clouds.

 Globular cluster and dwarf galaxy orbits
Copyright: ESA/Gaia/DPAC  

Gaia data were used to derive the orbits of 75 globular clusters and 12 dwarf galaxies that revolve around the Milky Way, providing all-important information to study the past evolution of our Galaxy and its environment, the gravitational forces that are at play, and the distribution of the elusive dark matter that permeates galaxies.

“Gaia is astronomy at its finest,” says Fred Jansen, Gaia mission manager at ESA.

“Scientists will be busy with this data for many years, and we are ready to be surprised by the avalanche of discoveries that will unlock the secrets of our Galaxy.”

Parallax and proper motion on the sky
Copyright: ESA/Gaia/DPAC 
Access the video

Notes for Editors

The data from Gaia’s first release can be accessed at

The content of the second Gaia release was presented today during a media briefing at the ILA Berlin Air and Space Show in Germany.

A series of scientific papers describing the data contained in the release and their validation process will appear in a special issue of Astronomy & Astrophysics.

A series of 360-degree videos and other Virtual Reality visualisation resources are available at

Gaia is an ESA mission to survey more than one billion stars in our Galaxy and its local neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its structure, origin and evolution.

A large pan-European team of expert scientists and software developers, the Data Processing and Analysis Consortium, located in and funded by many ESA member states, is responsible for the processing and validation of Gaia’s data, with the final objective of producing the Gaia Catalogue. Scientific exploitation of the data will only take place once they are openly released to the community.

More data releases will be issued in future years, with the final Gaia catalogue to be published in the 2020s. This will be the definitive stellar catalogue for the foreseeable future, playing a central role in a wide range of fields in astronomy.

Gaia was originally planned for a five-year mission, operating until mid-2019. ESA has already approved an indicative extension until the end of 2020, which is up for confirmation at the end of this year.

For further information, please contact:

Markus Bauer
Head of the Joint Communication Office
European Space Agency

Tel: +31 71 565 6799

Mob: +31 61 594 3 954


Anthony Brown
Leiden Observatory, Leiden University
Leiden, The Netherlands

Antonella Vallenari
INAF, Astronomical Observatory of Padua

Timo Prusti
Gaia Project Scientist
European Space Agency

Fred Jansen
Gaia mission manager
European Space Agency

Source: ESA/GAIA

Wednesday, April 25, 2018

NASA’s James Webb Space Telescope Could Potentially Detect the First Stars and Black Holes

Galaxy clusters like Abell 2744 can act as a natural cosmic lens, magnifying light from more distant, background objects through gravity. NASA’s James Webb Space Telescope may be able to detect light from the first stars in the universe if they are gravitationally lensed by such clusters.Credits: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI). Hi-res image

This diagram illustrates how rays of light from a distant galaxy or star can be bent by the gravity of an intervening galaxy cluster. As a result, an observer on Earth sees the distant object appear brighter than it would look if it weren’t gravitationally lensed.Credits: NASA, ESA, and A. Feild and F. Summers (STScI). Hi-res image

The first stars in the universe blazed to life about 200 to 400 million years after the big bang. Observing those very first individual stars across such vast distances of space normally would be a feat beyond any space science telescope. However, new theoretical work suggests that under the right circumstances, and with a little luck, NASA’s upcoming James Webb Space Telescope will be able to capture light from single stars within that first generation of stars.

“Looking for the first stars and black holes has long been a goal of astronomy. They will tell us about the actual properties of the very early universe, things we’ve only modeled on our computers until now,” said Rogier Windhorst of Arizona State University, Tempe. Windhorst is lead author of the paper that appeared in the Astrophysical Journal Supplement.

“We want to answer questions about the early universe such as, were binary stars common or were most stars single? How many heavy chemical elements were produced, cooked up by the very first stars, and how did those first stars effect star formation?” added co-author Frank Timmes of Arizona State University.

The key will be to look for a star that has been gravitationally lensed, its light bent and magnified by the gravity of an intervening galaxy cluster. But not just any gravitational lensing will do. Typical gravitational lensing can magnify light by a factor of 10 to 20 times, not enough to make a first-generation star visible to Webb.

But if the distant star and closer galaxy cluster line up just right, the star’s light can be amplified 10,000 times or more, bringing it within the realm of detectability. This could be done via so-called cluster caustic transits, where the light from a first star candidate could be enormously magnified for a few months due to the motion of the galaxy cluster across the sky.

The chances of such a precise alignment are small, but not zero. Astronomers recently announced that Hubble spotted a super-magnified star known as “Icarus.” Although it was the farthest single star ever seen, it was much closer than the stars Webb might locate. With Webb, the team hopes to find a lensed example of a star that formed from the primordial mix of hydrogen and helium that suffused the early universe, which astronomers call Population III stars.

In addition to the first stars, Windhorst and his colleagues investigated the possibility of seeing accretion disks surrounding the first black holes. Such a black hole, formed by the cataclysmic death of a massive star, could shine brightly if it pulled gas from a companion star.

The longer an object shines, the more likely it will drift into alignment with a gravitational lens. First-generation stars are expected to have been both massive and short-lived, lasting for just a few million years before exploding as supernovae. In contrast, a black hole stripping a companion star could shine for 10 times longer, feeding from a steady stream of gas. As a result, Webb might detect more black hole accretion disks than early stars.

The team calculates that an observing program that targets several galaxy clusters a couple of times a year for the lifetime of Webb could succeed in finding a lensed first star or black hole accretion disk. They have already selected some of the best target clusters, including the Hubble Frontier Fields clusters and the cluster known as “El Gordo."

“We just have to get lucky and observe these clusters long enough,” said Windhorst. “The astronomical community would need to continue to monitor these clusters during Webb’s lifetime.”

The James Webb Space Telescope will be the world's premier space science observatory. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

Related Links:


Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Rogier Windhorst
Arizona State University, Tempe, Arizona

Tuesday, April 24, 2018

A New Method for Galaxy Density Wave Analysis

NGC 3433 (image from SDSS). Superposed: MUSE field (red square); GHaFaS field (yellow square); projected corotation circle for the bar (solid green line); and the other measured corotation radii (dashed green lines). Large format: [ JPEG ]. 

Astronomers from the Instituto de Astrofísica de Canarias (IAC) have produced a complex velocity analysis of the spiral galaxy NGC 3433 with surprisingly precise results. They compared observations using the 2D Fabry-Perot spectrometer GHaFaS on the William Herschel Telescope (WHT) with those of the same object taken with the IFU spectrograph MUSE on the Very Large Telescope (VLT) in Chile. 

Font and Beckman (IAC) have developed a technique (FB) for finding the corotation radii in galaxies, i.e. the radii at which the spiral density waves propagate at the same angular speed as the stars and the gas. Simple theory suggests that the bar of a galaxy should stimulate a density wave outside it, which in turn stimulates and maintains the spiral arms. Using FB, the IAC researchers had shown previously in a large sample of galaxies that normally more than a single corotation is found in a galaxy, but that only one of them is related to the bar, while the others are found in the spiral arms, at increasing radii, or associated with a smaller, nuclear bar or oval distortion at small radii. 

While MUSE has a 1 arcmin × 1 arcmin field and offers spectral coverage of both stellar and gas components with a resolution of some 50 km/s in velocity, GHaFaS has a larger field of view, 3.4 arcmin × 3.4 arcmin field, gives a resolution in velocity of 6 km/sec, but it can observe only the ionised interstellar gas. 

Now with NGC 3433 they have put all of their previous work on a firmer basis by comparing it with a classical, and quite different, technique for finding corotation radii, developed by Tremaine and Weinberg (TW). They applied both methods to the velocity fields of both the stars and the insterstellar gas, using the observations of both GHaFaS and MUSE. They found four corotation radii. 

The innermost one, in the circumnuclear zone, could be detected only using FB, but was found clearly in both MUSE and GHaFaS data for the gas with a difference of 7% in the values. The second one, corresponding to the main bar, and the most intense, was measured in six different ways: using FB on the gas with GHaFaS, FB on the gas with MUSE, FB on the stars with MUSE, TW on the gas with GHaFaS, TW on the gas with MUSE, and TW on the stars with MUSE. The uncertainty in the corotation found by using all 6 values was only 4%. 

A third corotation was found using FB on gas for both GHaFaS and MUSE, and a fourth corotation, beyond the limits of the field of MUSE, was measured using FB and TW on the gas with GHaFaS. The values for the corotation radii in both cases, gave excellent agreement between the two methods used. Measured this way the corotation radii are among the most accurately determined parameters of the galaxy, compared with, for example, the bar length.

Panel (a): velocity map of NGC 3433 using the first moment map of Hα emission in the FP data cube from GHaFaS. The box in black shows the size of the MUSE data. Panel (b): velocity map of Hα emission from the central square arcmin from the MUSE data cube. Panel (c): velocity map of the stellar component from the MUSE data. Large format: [ JPEG ]. 
Although this study deals with only a single galaxy, its results are powerful because they verify FB as a method, and it is considerably easier than TW to apply to large numbers of objects, demanding less observing time. Measuring the principal corotation radius allows us to measure the pattern speed of the bar, and this allows us to perform a whole range of tests on the evolution of galaxies, including measuring the braking effects of dark matter halos. "For the time being we are confined to low redshifts, but as our techniques advance we have hopes of reaching intermediate redshift objects in the fairly near future", said John Beckman. Isaac Newton Group of Telescopes

More Information

Beckman, John E.; Font, Joan; Borlaff, Alejandro; García-Lorenzo, Begoña, 2018, "Precision Determination of Corotation Radii in Galaxy Disks: Tremaine-Weinberg versus Font-Beckman for NGC 3433", ApJ, 854, 182 [ ADS ].
"The Galaxies "tune up their musical instruments", IAC press release, 9th April 2018. 

"New Light on Dark Matter Halos", ING web news release, 13th February 2017.

Javier Méndez  
(Public Relations Officer)

Monday, April 23, 2018

Reaching New Heights at the ESO Supernova

"Reaching New Heights" poster

On Friday 4 May, a live planetarium show — Reaching New Heights — will be presented at the ESO Supernova Planetarium & Visitor Centre. This show will take the audience on a journey around ESO’s state-of-the-art facilities, immersing them in Chile’s stunning scenery and wonderful dark skies.

As the world’s leading ground-based astronomy organisation, the European Southern Observatory (ESO) builds and operates some of the best telescopes in the world, enabling exciting astronomical discoveries and the further understanding of our fascinating Universe. Reaching New Heights provides an overview of ESO, including amazing footage of the telescopes in the Atacama Desert, scientific simulations of discoveries made with these facilities, and a peek into the future as ESO sets out to build the world’s largest optical telescope, the Extremely Large Telescope (ELT).

The event is free of charge and is aimed at the general public including children over 8 years old. The show will be presented in German by ESO Supernova coordinator Tania Johnston, who will also present an English version on 15 June. More information about the show, as well as the link to book tickets for both the German and the English screenings, can be found here. Seats should be reserved before arrival.

The ESO Supernova Planetarium & Visitor Centre will open its doors to the public on 28 April 2018. To see the full range of activities on offer and to book a place at any forthcoming events, please use the following link.

More  Information

The ESO Supernova Planetarium & Visitor Centre

The ESO Supernova Planetarium & Visitor Centre is a cooperation between the European Southern Observatory (ESO) and the Heidelberg Institute for Theoretical Studies (HITS). The building is a donation from the Klaus Tschira Stiftung (KTS), a German foundation, and ESO runs the facility.



Tania Johnston
ESO Supernova Coordinator
Garching bei München, Germany
Tel: +49 89 320 061 30

Oana Sandu
Community Coordinator & Communication Strategy Officer
Tel: +49 89 320 069 65

Friday, April 20, 2018

Approaching the Universe’s origins

Credit:ESA/Hubble & NASA, RELICS

This intriguing image from the NASA/ESA Hubble Space Telescope shows a massive galaxy cluster called PSZ2 G138.61-10.84, about six billion light-years away. Galaxies are not randomly distributed in space, but rather aggregated in groups, clusters and superclusters. The latter span over hundreds of millions of light-years and contain billions of galaxies.

Our own galaxy, for example, is part of the Local Group, which in turn is part of the giant Laniakea Supercluster. It was thanks to Hubble that we were able to study massive galactic superstructures such as the Hercules-Corona Borealis Great Wall; a giant galaxy cluster that contains billions of galaxies and extends 10 billion light-years across — making it the biggest known structure in the Universe.

This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Source: ESA/Hubble/Potw

Thursday, April 19, 2018

Hubble celebrates 28th anniversary with a trip through the Lagoon Nebula

Hubble's 28th birthday picture: The Lagoon Nebula

Infrared view of the Lagoon Nebula
Infrared view of the Lagoon Nebula


Hubblecast 109: Diving into the Lagoon Nebula
Hubblecast 109: Diving into the Lagoon Nebula

The centre of the Lagoon Nebula over time
The centre of the Lagoon Nebula over time

Diving into the Lagoon Nebula
Diving into the Lagoon Nebula

Swimming across the Lagoon Nebula
Swimming across the Lagoon Nebula

Fulldome view of the Lagoon Nebula
Fulldome view of the Lagoon Nebula

Lagoon Nebula in visible and infrared light
Lagoon Nebula in visible and infrared light

Image Comparisons

Comparison image of the Lagoon Nebula in optical and infrared

This colourful cloud of glowing interstellar gas is just a tiny part of the Lagoon Nebula, a vast stellar nursery. This nebula is a region full of intense activity, with fierce winds from hot stars, swirling chimneys of gas, and energetic star formation all embedded within a hazy labyrinth of gas and dust. Hubble used both its optical and infrared instruments to study the nebula, which was observed to celebrate Hubble’s 28th anniversary.

Since its launch on 24 April 1990, the NASA/ESA Hubble Space Telescope has revolutionised almost every area of observational astronomy. It has offered a new view of the Universe and has reached and surpassed all expectations for a remarkable 28 years. To celebrate Hubble’s legacy and the long international partnership that makes it possible, each year ESA and NASA celebrate the telescope’s birthday with a spectacular new image. This year’s anniversary image features an object that has already been observed several times in the past: the Lagoon Nebula.

The Lagoon Nebula is a colossal object 55 light-year wide and 20 light-years tall. Even though it is about 4000 light-years away from Earth, it is three times larger in the sky than the full Moon. It is even visible to the naked eye in clear, dark skies. Since it is relatively huge on the night sky, Hubble is only able to capture a small fraction of the total nebula. This image is only about four light-years across, but it shows stunning details.

The inspiration for this nebula’s name may not be immediately obvious in this image. It becomes clearer only in a wider field of view, when the broad, lagoon-shaped dust lane that crosses the glowing gas of the nebula can be made out. This new image, however, depicts a scene at the very heart of the nebula.

Like many stellar nurseries, the nebula boasts many large, hot stars. Their ultraviolet radiation ionises the surrounding gas, causing it to shine brightly and sculpting it into ghostly and other-worldly shapes. The bright star embedded in dark clouds at the centre of the image is Herschel 36. Its radiation sculpts the surrounding cloud by blowing some of the gas away, creating dense and less dense regions.

Among the sculptures created by Herschel 36 are two interstellar twisters — eerie, rope-like structures that each measure half a light-year in length. These features are quite similar to their namesakes on Earth — they are thought to be wrapped into their funnel-like shapes by temperature differences between the hot surfaces and cold interiors of the clouds. At some point in the future, these clouds will collapse under their own weight and give birth to a new generation of stars.

Hubble observed the Lagoon Nebula not only in visible light but also at infrared wavelengths. While the observations in the optical allow astronomers to study the gas in full detail, the infrared light cuts through the obscuring patches of dust and gas, revealing the more intricate structures underneath and the young stars hiding within it. Only by combining optical and infrared data can astronomers paint a complete picture of the ongoing processes in the nebula.

More Information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Image credit: NASA, ESA, STScI



Mathias Jäger
ESA/Hubble, Public Information Officer
Garching bei München, Germany
Tel: +49 176 62397500

Source: ESA/Hubble/News

Wednesday, April 18, 2018

Where is the Universe's missing matter?

Copyright: ESA/XMM-Newton; J-T. Li (University of Michigan, USA); 
Sloan Digital Sky Survey (SDSS)  

Astronomers using ESA’s XMM-Newton space observatory have probed the gas-filled haloes around galaxies in a quest to find ‘missing’ matter thought to reside there, but have come up empty-handed – so where is it? 

All the matter in the Universe exists in the form of ‘normal’ matter or the notoriously elusive and invisible dark matter, with the latter around six times more prolific. 

Curiously, scientists studying nearby galaxies in recent years have found them to contain three times less normal matter than expected, with our own Milky Way Galaxy containing less than half the expected amount. 

“This has long been a mystery, and scientists have spent a lot of effort searching for this missing matter,” says Jiangtao Li of the University of Michigan, USA, and lead author of a new paper.  

“Why is it not in galaxies — or is it there, but we are just not seeing it? If it’s not there, where is it? It is important we solve this puzzle, as it is one of the most uncertain parts of our models of both the early Universe and of how galaxies form.”

Rather than lying within the main bulk of the galaxy, the part can be observed optically, researchers thought it may instead lie within a region of hot gas that stretches further out into space to form a galaxy’s halo. 

These hot, spherical haloes have been detected before, but the region is so faint that it is difficult to observe in detail – its X-ray emission can become lost and indistinguishable from background radiation. Often, scientists observe a small distance into this region and extrapolate their findings but this can result in unclear and varying results. 

Jiangtao and colleagues wanted to measure the hot gas out to larger distances using ESA’s XMM-Newton X-ray space observatory. They looked at six similar spiral galaxies and combined the data to create one galaxy with their average properties. 

“By doing this, the galaxy’s signal becomes stronger and the X-ray background becomes better behaved,” adds co-author Joel Bregman, also of the University of Michigan. 

“We were then able to see the X-ray emission to about three times further out than if observing a single galaxy, which made our extrapolation more accurate and reliable.” 

Massive and isolated spiral galaxies offer the best chance to search for missing matter. They are massive enough to heat gas to temperatures of millions of degrees so that they emit X-rays, and have largely avoided being contaminated by other material through star formation or interactions with other galaxies.

Still missing

The team’s results showed that the halo surrounding galaxies like the ones observed cannot contain all of the missing matter after all. Despite extrapolating out to almost 30 times the radius of the Milky Way, nearly three-quarters of the expected material was still missing.

There are two main alternative theories as to where it could be: either it is stored in another gas phase that is poorly observed – perhaps either a hotter and more tenuous phase or a cooler and denser one – or within a patch of space that is not covered by our current observations or emits X-rays too faintly to be detected.

Either way, since the galaxies do not contain enough missing matter they may have ejected it out into space, perhaps driven by injections of energy from exploding stars or by supermassive black holes.

“This work is important to help create more realistic galaxy models, and in turn help us better understand how our own Galaxy formed and evolved,” says Norbert Schartel, ESA XMM-Newton project scientist. “This kind of finding is simply not possible without the incredible sensitivity of XMM-Newton.”

“In the future, scientists can add even more galaxies to our study samples and use XMM-Newton in collaboration with other high-energy observatories, such as ESA’s upcoming Advanced Telescope for High-ENergy Astrophysics, Athena, to probe the extended, low-density parts of a galaxy’s outer edges, as we continue to unravel the mystery of the Universe’s missing matter.”

Notes for Editors

“Baryon budget of the hot circumgalactic medium of massive spiral galaxies,” by J-T Li et al. (2018) is published in The Astrophysical Journal Letters. DOI: 10.3847/2041-8213/aab2af.

For further information, please contact:

Jiangtao Li
University of Michigan, USA
Tel: 734-383-2089 

Joel Bregman
University of Michigan, USA
Tel: 734-764-2667 

Norbert Schartel
XMM-Newton Project Scientist
European Space Agency

Monday, April 16, 2018

A Key Element to Life is Lacking in the Crab Nebula

A composite of infrared (shown as red), visible (green) and ultraviolet (violet) images of the Crab Nebula, with IR enhanced and visible/UV balanced to yield neutral star colours. Composite image made with the Cosmic Coloring Compositor. Credit: NRAO. Large format: [ PNG ].

Work by Jane Greaves and Phil Cigan from Cardiff University, UK suggests there may be a cosmic paucity of a chemical element essential to life. Greaves has been searching for phosphorus in the universe, because of its link to life on Earth. If this element is lacking in other parts of the cosmos, then it could be difficult for extra-terrestrial life to exist. 

She explains "Phosphorus is one of just six chemical elements on which Earth organisms depend, and it is crucial to the compound adenosine triphosphate (ATP), which cells use to store and transfer energy. Astronomers have just started to pay attention to the cosmic origins of phosphorus, and found quite a few surprises. In particular, phosphorus is created in supernovae - the explosions of massive stars - but the amounts seen so far don't match our computer models. I wondered what the implications were for life on other planets if unpredictable amounts of phosphorus are spat out into space, and later used in the construction of new planets." 

The team used LIRIS on the William Herschel Telescope (WHT) to observe infrared light from phosphorus and iron in the Crab Nebula, a supernova remnant around 6,500 light-years away in the constellation of Taurus. 

Spectrum of one position near the centre of the Crab Nebula, taken with LIRIS at the WHT. The overlaid dotted line is a synthetic representation of how the phosphorus line would appear if the Crab Nebula had the same ratio of phosphorus to iron as the median value in Cas A, the only other supernova remnant where phosphorus was studied previously. Credit: Jane Greaves and Phil Cigan. Large format: [ PNG ]. 

These preliminary results suggest that material blown out into space could vary dramatically in chemical composition. Greaves remarks "The route to carrying phosphorus into new-born planets looks rather precarious. We already think that only a few phosphorus-bearing minerals that came to the Earth - probably in meteorites - were reactive enough to get involved in making proto-biomolecules." 

She adds: "If phosphorus is sourced from supernovae, and then travels across space in meteoritic rocks, I'm wondering if a young planet could find itself lacking in reactive phosphorus because of where it was born? That is, it started off near the wrong kind of supernova? In that case, life might really struggle to get started out of phosphorus-poor chemistry on another world otherwise similar to our own."Isaac Newton Group of Telescopes

More Information

"Paucity of phosphorus hints at precarious path for extraterrestrial life", European Week of Astronomy and Space Science press release, 3rd April 2018.


Javier Méndez  (Public Relations Officer)

Friday, April 13, 2018

A colossal cluster

Credit: ESA/Hubble & NASA, RELICS

This NASA/ESA Hubble Space Telescope image shows a massive galaxy cluster glowing brightly in the darkness. Despite its beauty, this cluster bears the distinctly unpoetic name of PLCK_G308.3-20.2. 

Galaxy clusters can contain thousands of galaxies all held together by the glue of gravity. At one point in time they were believed to be the largest structures in the Universe — until they were usurped in the 1980s by the discovery of superclusters, which typically contain dozens of galaxy clusters and groups and span hundreds of millions of light-years. However, clusters do have one thing to cling on to; superclusters are not held together by gravity, so galaxy clusters still retain the title of the biggest structures in the Universe bound by gravity.

One of the most interesting features of galaxy clusters is the stuff that permeates the space between the constituent galaxies: the intracluster medium (ICM). High temperatures are created in these spaces by smaller structures forming within the cluster. This results in the ICM being made up of plasma — ordinary matter in a superheated state. Most luminous matter in the cluster resides in the ICM, which is very luminous X-rays. However, the majority of the mass in a galaxy cluster exists in the form of non-luminous dark matter. Unlike plasma, dark matter is not made from ordinary matter such as protons, neutrons and electrons. It is a hypothesised substance thought to make up 80 % of the Universe’s mass, yet it has never been directly observed.

This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Thursday, April 12, 2018

NASA's Juno Mission Provides Infrared Tour of Jupiter's North Pole

This infrared 3-D image of Jupiter's north pole was derived from data collected by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard NASA's Juno spacecraft. Image credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM.  › Larger view

Scientists working on NASA's Juno mission to Jupiter shared a 3-D infrared movie depicting densely packed cyclones and anticyclones that permeate the planet's polar regions, and the first detailed view of a dynamo, or engine, powering the magnetic field for any planet beyond Earth. Those are among the items unveiled during the European Geosciences Union General Assembly in Vienna, Austria, on Wednesday, April 11.

In this animation the viewer is taken low over Jupiter's north pole to illustrate the 3-D aspects of the region's central cyclone and the eight cyclones that encircle it. The movie utilizes imagery derived from data collected by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard NASA's Juno mission during its fourth pass over the massive planet. Infrared cameras are used to sense the temperature of Jupiter's atmosphere and provide insight into how the powerful cyclones at Jupiter's poles work. In the animation, the yellow areas are warmer (or deeper into Jupiter's atmosphere) and the dark areas are colder (or higher up in Jupiter's atmosphere). In this picture the highest "brightness temperature" is around 260K (about -13°C) and the lowest around 190K (about -83°C). The "brightness temperature" is a measurement of the radiance, at 5 µm, traveling upward from the top of the atmosphere towards Juno, expressed in units of temperature.

Juno mission scientists have taken data collected by the spacecraft's Jovian InfraRed Auroral Mapper (JIRAM) instrument and generated the 3-D fly-around of the Jovian world's north pole. Imaging in the infrared part of the spectrum, JIRAM captures light emerging from deep inside Jupiter equally well, night or day. The instrument probes the weather layer down to 30 to 45 miles (50 to 70 kilometers) below Jupiter's cloud tops. The imagery will help the team understand the forces at work in the animation - a north pole dominated by a central cyclone surrounded by eight circumpolar cyclones with diameters ranging from 2,500 to 2,900 miles (4,000 to 4,600 kilometers).

NASA's Juno mission has provided the first view of the dynamo, or engine, powering Jupiter's magnetic field. The new global portrait reveals unexpected irregularities and regions of surprising magnetic field intensity. Red areas show where magnetic field lines emerge from the planet, while blue areas show where they return. As Juno continues its mission, it will improve our understanding of Jupiter's complex magnetic environment. 

"Before Juno, we could only guess what Jupiter's poles would look like," said Alberto Adriani, Juno co-investigator from the Institute for Space Astrophysics and Planetology, Rome. "Now, with Juno flying over the poles at a close distance it permits the collection of infrared imagery on Jupiter's polar weather patterns and its massive cyclones in unprecedented spatial resolution." 

Another Juno investigation discussed during the media briefing was the team's latest pursuit of the interior composition of the gas giant. One of the biggest pieces in its discovery has been understanding how Jupiter's deep interior rotates. 

"Prior to Juno, we could not distinguish between extreme models of Jupiter's interior rotation, which all fitted the data collected by Earth-based observations and other deep space missions," said Tristan Guillot, a Juno co-investigator from the Université Côte d'Azur, Nice, France. "But Juno is different -- it orbits the planet from pole-to-pole and gets closer to Jupiter than any spacecraft ever before. 

Thanks to the amazing increase in accuracy brought by Juno's gravity data, we have essentially solved the issue of how Jupiter's interior rotates: The zones and belts that we see in the atmosphere rotating at different speeds extend to about 1,900 miles (3,000 kilometers).

An infrared view of Jupiter's North Pole. The movie utilizes imagery derived from data collected by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard NASA's Juno mission. The images were obtained during Juno's fourth pass over Jupiter. Infrared cameras are used to sense the temperature of Jupiter's atmosphere and provide insight into how the powerful cyclones at Jupiter's poles work. In the animation, the yellow areas are warmer (or deeper into Jupiter's atmosphere) and the dark areas are colder (or higher up in Jupiter's atmosphere). In this picture the highest "brightness temperature" is around 260K (about -13°C) and the lowest around 190K (about -83°C). The "brightness temperature" is a measurement of the radiance, at 5 µm, traveling upward from the top of the atmosphere towards Juno, expressed in units of temperature.

"At this point, hydrogen becomes conductive enough to be dragged into near-uniform rotation by the planet's powerful magnetic field."

The same data used to analyze Jupiter's rotation contain information on the planet's interior structure and composition. Not knowing the interior rotation was severely limiting the ability to probe the deep interior. "Now our work can really begin in earnest -- determining the interior composition of the solar system's largest planet," said Guillot.

At the meeting, the mission's deputy-principal investigator, Jack Connerney of the Space Research Corporation, Annapolis, Maryland, presented the first detailed view of the dynamo, or engine, powering the magnetic field of Jupiter.

Connerney and colleagues produced the new magnetic field model from measurements made during eight orbits of Jupiter. From those, they derived maps of the magnetic field at the surface and in the region below the surface where the dynamo is thought to originate. Because Jupiter is a gas giant, "surface" is defined as one Jupiter radius, which is about 44,400 miles (71,450 kilometers).

These maps provide an extraordinary advancement in current knowledge and will guide the science team in planning the spacecraft's remaining observations.

"We're finding that Jupiter's magnetic field is unlike anything previously imagined,"said Connerney. "Juno's investigations of the magnetic environment at Jupiter represent the beginning of a new era in the studies of planetary dynamos."

The map Connerney's team made of the dynamo source region revealed unexpected irregularities, regions of surprising magnetic field intensity, and that Jupiter's magnetic field is more complex in the northern hemisphere than in the southern hemisphere. About halfway between the equator and the north pole lies an area where the magnetic field is intense and positive. It is flanked by areas that are less intense and negative. In the southern hemisphere, however, the magnetic field is consistently negative, becoming more and more intense from the equator to the pole.

The researchers are still figuring out why they would see these differences in a rotating planet that's generally thought of as more-or-less fluid.

"Juno is only about one third the way through its planed mapping mission and already we are beginning to discover hints on how Jupiter's dynamo works," said Connerney. "The team is really anxious to see the data from our remaining orbits."

Juno has logged nearly 122 million miles (200 million kilometers) to complete those 11 science passes since entering Jupiter's orbit on July 4, 2016. Juno's 12th science pass will be on May 24.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. The Italian Space Agency (ASI), contributed two instruments, a Ka-band frequency translator (KaT) and the Jovian Infrared Auroral Mapper (JIRAM). Lockheed Martin Space, Denver, built the spacecraft.

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DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.

JoAnna Wendel
NASA Headquarters, Washington

Wednesday, April 11, 2018

SPHERE Reveals Fascinating Zoo of Discs Around Young Stars

SPHERE images a zoo of dusty discs around young stars

PR Image eso1811b
SPHERE images the edge-on disc around the star GSC 07396-00759

PR Image eso1811c
SPHERE image of the dusty disc around IM Lupi

ESOcast 156 Light: Weird and Wonderful Dusty Discs (4K UHD)
ESOcast 156 Light: Weird and Wonderful Dusty Discs (4K UHD)

New images from the SPHERE instrument on ESO’s Very Large Telescope are revealing the dusty discs surrounding nearby young stars in greater detail than previously achieved. They show a bizarre variety of shapes, sizes and structures, including the likely effects of planets still in the process of forming.

The SPHERE instrument on ESO’s Very Large Telescope (VLT) in Chile allows astronomers to suppress the brilliant light of nearby stars in order to obtain a better view of the regions surrounding them. This collection of new SPHERE images is just a sample of the wide variety of dusty discs being found around young stars.

These discs are wildly different in size and shape — some contain bright rings, some dark rings, and some even resemble hamburgers. They also differ dramatically in appearance depending on their orientation in the sky — from circular face-on discs to narrow discs seen almost edge-on.

SPHERE’s primary task is to discover and study giant exoplanets orbiting nearby stars using direct imaging. But the instrument is also one of the best tools in existence to obtain images of the discs around young stars — regions where planets may be forming. Studying such discs is critical to investigating the link between disc properties and the formation and presence of planets.

Many of the young stars shown here come from a new study of T Tauri stars, a class of stars that are very young (less than 10 million years old) and vary in brightness. The discs around these stars contain gas, dust, and planetesimals — the building blocks of planets and the progenitors of planetary systems.

These images also show what our own Solar System may have looked like in the early stages of its formation, more than four billion years ago.

Most of the images presented were obtained as part of the DARTTS-S (Discs ARound T Tauri Stars with SPHERE) survey. The distances of the targets ranged from 230 to 550 light-years away from Earth. For comparison, the Milky Way is roughly 100 000 light-years across, so these stars are, relatively speaking, very close to Earth. But even at this distance, it is very challenging to obtain good images of the faint reflected light from discs, since they are outshone by the dazzling light of their parent stars.

Another new SPHERE observation is the discovery of an edge-on disc around the star GSC 07396-00759, found by the SHINE (SpHere INfrared survey for Exoplanets) survey. This red star is a member of a multiple star system also included in the DARTTS-S sample but, oddly, this new disc appears to be more evolved than the gas-rich disc around the T Tauri star in the same system, although they are the same age.This puzzling difference in the evolutionary timescales of discs around two stars of the same age is another reason why astronomers are keen to find out more about discs and their characteristics.

Astronomers have used SPHERE to obtain many other impressive images, as well as for other studies including the interaction of a planet with a disc, the orbital motions within a system, and the time evolution of a disc.

The new results from SPHERE, along with data from other telescopes such as ALMA, are revolutionising astronomers’ understanding of the environments around young stars and the complex mechanisms of planetary formation.

More Information

The images of T Tauri star discs were presented in a paper entitled “Disks Around T Tauri Stars With SPHERE (DARTTS-S) I: SPHERE / IRDIS Polarimetric Imaging of 8 Prominent T Tauri Disks”, by H. Avenhaus et al., to appear in in the Astrophysical Journal. The discovery of the edge-on disc is reported in a paper entitled “A new disk discovered with VLT/SPHERE around the M star GSC 07396-00759”, by E. Sissa et al., to appear in the journal Astronomy & Astrophysics.

The first team is composed of Henning Avenhaus (Max Planck Institute for Astronomy, Heidelberg, Germany; ETH Zurich, Institute for Particle Physics and Astrophysics, Zurich, Switzerland; Universidad de Chile, Santiago, Chile), Sascha P. Quanz (ETH Zurich, Institute for Particle Physics and Astrophysics, Zurich, Switzerland; National Center of Competence in Research “PlanetS”), Antonio Garufi (Universidad Autonónoma de Madrid, Madrid, Spain), Sebastian Perez (Universidad de Chile, Santiago, Chile; Millennium Nucleus Protoplanetary Disks Santiago, Chile), Simon Casassus (Universidad de Chile, Santiago, Chile; Millennium Nucleus Protoplanetary Disks Santiago, Chile), Christophe Pinte (Monash University, Clayton, Australia; Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France), Gesa H.-M. Bertrang (Universidad de Chile, Santiago, Chile), Claudio Caceres (Universidad Andrés Bello, Santiago, Chile), Myriam Benisty (Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU; Universidad de Chile, Santiago, Chile; Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France) and Carsten Dominik (Anton Pannekoek Institute for Astronomy, University of Amsterdam, The Netherlands).

The second team is composed of: E. Sissa (INAF-Osservatorio Astronomico di Padova, Padova, Italy), J. Olofsson (Max Planck Institute for Astronomy, Heidelberg, Germany; Universidad de Valparaíso, Valparaíso, Chile), A. Vigan (Aix-Marseille Université, CNRS, Laboratoire d’Astrophysique de Marseille, Marseille, France), J.C. Augereau (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France) , V. D’Orazi (INAF-Osservatorio Astronomico di Padova, Padova, Italy), S. Desidera (INAF-Osservatorio Astronomico di Padova, Padova, Italy), R. Gratton (INAF-Osservatorio Astronomico di Padova, Padova, Italy), M. Langlois (Aix-Marseille Université, CNRS, Laboratoire d’Astrophysique de Marseille Marseille, France; CRAL, CNRS, Université de Lyon, Ecole Normale Suprieure de Lyon, France), E. Rigliaco (INAF-Osservatorio Astronomico di Padova, Padova, Italy), A. Boccaletti (LESIA, Observatoire de Paris-Meudon, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, Meudon, France), Q. Kral (LESIA, Observatoire de Paris-Meudon, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, Meudon, France; Institute of Astronomy, University of Cambridge, Cambridge, UK), C. Lazzoni (INAF-Osservatorio Astronomico di Padova, Padova, Italy; Universitá di Padova, Padova, Italy), D. Mesa (INAF-Osservatorio Astronomico di Padova, Padova, Italy; University of Atacama, Copiapo, Chile), S. Messina (INAF-Osservatorio Astrofisico di Catania, Catania, Italy), E. Sezestre (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), P. Thébault (LESIA, Observatoire de Paris-Meudon, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, Meudon, France), A. Zurlo (Universidad Diego Portales, Santiago, Chile; Unidad Mixta Internacional Franco-Chilena de Astronomia, CNRS/INSU; Universidad de Chile, Santiago, Chile; INAF-Osservatorio Astronomico di Padova, Padova, Italy), T. Bhowmik (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), M. Bonnefoy (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), G. Chauvin (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France; Universidad Diego Portales, Santiago, Chile), M. Feldt (Max Planck Institute for Astronomy, Heidelberg, Germany), J. Hagelberg (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), A.-M. Lagrange (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), M. Janson (Stockholm University, Stockholm, Sweden; Max Planck Institute for Astronomy, Heidelberg, Germany), A.-L. Maire (Max Planck Institute for Astronomy, Heidelberg, Germany), F. Ménard (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), J. Schlieder (NASA Goddard Space Flight Center, Greenbelt, Maryland, USA; Max Planck Institute for Astronomy, Heidelberg, Germany), T. Schmidt (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), J. Szulági (Institute for Particle Physics and Astrophysics, ETH Zurich, Zurich, Switzerland; Institute for Computational Science, University of Zurich, Zurich, Switzerland), E. Stadler (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), D. Maurel (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), A. Deboulbé (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), P. Feautrier (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), J. Ramos (Max Planck Institute for Astronomy, Heidelberg, Germany) and R. Rigal (Anton Pannekoek Institute for Astronomy, Amsterdam, The Netherlands).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 15 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Henning Avenhaus
Max Planck Institute for Astronomy
Heidelberg, Germany

Elena Sissa
INAF - Astronomical Observatory of Padova
Padova, Italy

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591

Source: ESO/News