News & Press releases

Number of entries: 94

10
April 2018

Today ICE-CSIC/IEEC receive the first data of the experiment aboard the PAZ satellite


Today ICE-CSIC/IEEC receive the first data of the experiment aboard the PAZ satellite
The experiment led by ICE-CSIC/IEEC aboard the PAZ satellite, called Radio-Occultation and Heavy Precipitation with PAZ (ROHP-PAZ) was activated on April 4, 2018. Today the ICE/CSIC-IEEC received the first data sets! 
21
March 2018

La missió ARIEL seleccionada com a propera missió científica mitjana de l'ESA


La missió ARIEL seleccionada com a propera missió científica mitjana de l'ESA
ARIEL, una missió per respondre preguntes fonamentals sobre com es formen i evolucionen els sistemes planetaris, acaba de ser seleccionada per l'Agència Espacial Europea (ESA) com la seva propera missió científica de classe mitjana, amb data de llançament prevista pel 2028. Al llarg de 4 anys, ARIEL observarà 1000 planetes al voltant d’altres estrelles i farà el primer estudi a gran escala sobre la química de les atmosferes d’aquests exoplanetes.
 
La missió ARIEL ha estat desenvolupada per un consorci de més de 60 instituts de 15 països de l'ESA, inclosos el Regne Unit, França, Itàlia, Polònia, Espanya, Països Baixos, Bèlgica, Àustria, Dinamarca, Irlanda, Hongria, Suècia, Alemanya i Portugal, amb una col·laboració addicional de la NASA als EUA. L’IEEC lidera la participació espanyola i, a banda de la contribució científica, participa en la construcció de la missió, que inclou el sistema electrònic del satèl·lit que controla el telescopi i els moviments del mirall secundari, així com els programes informàtics que planifiquen les observacions dels planetes i que s’utilitzen a la base d’operacions de l’ESA. La resta d’institucions espanyoles involucrades són el Centro de Astrobiología, la Universidad Politécnica de Madrid i l’Instituto de Astrofísica de Canarias.
 
L'investigador principal d’ARIEL a Espanya, el Dr. Ignasi Ribas, de l'Institut de Ciències de l'Espai (ICE, CSIC) i director del Institut d'Estudis Espacials de Catalunya (IEEC) comenta: "Tot i que fins ara hem descobert al voltant de 3800 planetes que orbiten altres estrelles, la naturalesa d'aquests exoplanetes continua sent molt misteriosa. ARIEL n’estudiarà una mostra estadísticament gran per donar-nos una imatge veritablement representativa de què estan fets aquests planetes. Això ens permetrà respondre preguntes sobre com la química d'un planeta es vincula amb l'entorn en què es forma i com el seu naixement i evolució depenen de l’estrella a la qual orbiten". ARIEL estudiarà una població diversa d'exoplanetes que van des de la mida de Júpiter i Neptú fins a les anomenades súper-Terres, en una gran varietat d'ambients. El focus principal de la missió seran els planetes en òrbites properes a la seva estrella. Els exoplanetes calents, amb temperatures de fins a 2000ºC, representen un laboratori natural on estudiar la química i la formació planetàries, ja que les altes temperatures mantenen les diferents espècies moleculars en circulació per l'atmosfera i això les fa observables remotament.
 
ARIEL tindrà un telescopi amb un mirall primari d’un metre de diàmetre per recollir la llum visible i infraroja d’aquests sistemes planetaris que orbiten estrelles distants. Un espectròmetre descompondrà la llum en un "arc de Sant Martí" per extreure les empremtes químiques de les molècules atmosfèriques quan el planeta passa per davant o darrere de l'estrella. Un fotòmetre i un sistema de rastreig recolliran informació sobre la presència dels núvols a les atmosferes dels exoplanetes i permetran que el telescopi espacial apunti a cada estrella amb una gran estabilitat i precisió.
 
ARIEL serà llançat des de Kourou a la Guaiana Francesa i es posarà en òrbita al punt 2 de Lagrange (L2), que és un punt d'equilibri gravitacional a 1,5 milions de quilòmetres de l'òrbita de la Terra al voltant del Sol. Aquí, ARIEL estarà protegida del Sol i tindrà una visió sense obstacles de tot el cel per observar un gran nombre d’exoplanetes.
 
El gestor del projecte a nivell espanyol, el Dr. Josep Colomé, de l’ICE (ICE, CSIC) i del IEEC, declara: "La selecció d’ARIEL per part de l’ESA és una fantàstica notícia. És un reconeixement a la feina d’enginyeria feta durant els dos darrers anys i un impuls per la tecnologia espacial que desenvolupem per aquesta i altres missions i amb una estreta col·laboració amb la indústria del sector. ARIEL ens permet treballar amb centres de referència a nivell mundial i ens situa a la primera divisió de la tecnologia espacial."
 
ARIEL (Atmospheric Remote-Sensing Infrared Exoplanet Large-survey) en dades i xifres:

Mirall primari el·líptic: 1,1 x 0,7 metres
Instrumentació: 3 canals fotomètrics i 3 espectròmetres de baixa resolució que cobreixen de 0,5 a 7,8 micres en longitud d'ona.
Durada de la missió: 4 anys en òrbita
Data de llançament: 2028
Massa de càrrega útil: ~ 450 kg
Massa total: ~ 1300 kg
Destinació: Punt L2 de Lagrange Sol - Terra
Cost de la missió de l'ESA: ~ 450 milions d'euros, a més de les contribucions nacionals a la càrrega útil
Llançament del vehicle: Ariane 6-2 des de la Guaiana Francesa Imatges
 
04
March 2018

ESA's INTEGRAL satellite selects a figure in one of our papers as picture of the month


ESA's INTEGRAL satellite selects a figure in one of our papers as picture of the month (March 2018)
Which gamma-ray pulsars can be seen by INTEGRAL and why?

Neutron stars are a common compact endpoint of the life of stars. They have an extreme density (stars of about 10 km in size, with the mass of our Sun), and harbour the strongest magnetic fields (from 108 to 1014 times that of our Sun). Magnetized and rotating neutron stars emit beams of radiation, which can only be seen when the observer and the beam are aligned. Periodic recurrence of such alignment gives rise to pulsations, and to the name pulsar used for these objects.

Pulsars emit at all wavelengths, and their energy distribution (that is, how much power they yield at each wavelength band) varies strongly within the population. From the more than 2000 radio pulsars known, and the more than 200 gamma-ray pulsars known, we only know less than 20 of them which pulse in X-rays. The number of those detected in INTEGRAL's energy range is even lower.

What makes a pulsar shine in gamma-rays and/or X-ray energies? Ultimately, how can we predict, which pulsar will be visible to a particular X-ray instrument?

Despite the extreme precision of the observations, and the underlying complexity of the processes involved, recently a theoretical model for the spectra of pulsars has been proposed: just four physical parameters suffice to fit the emission spectrum of all gamma and/or X-ray pulsars known. When analyzing the properties for all pulsars, by grouping of these parameters, relevant correlations appear, explaining the different observational behaviours. As a bonus, the model acts as a tool to predict whether X-ray pulsars can be seen, starting from Fermi gamma-ray data. Detailed analysis of already detected and future gamma-ray pulsars can then lead to predicting whether or not INTEGRAL can detect them too.

Expectations for possible detections are shown in the image at the bottom, in the setting of the correlation of model parameters fitting the high-energy spectra of pulsars. Red and blue dots stand for gamma-ray-only, normal and millisecond pulsars, respectively. They show a strong correlation depicted with a dashed line (the shadowed region represents the 2 sigma uncertainty in this correlation). White (grey) crosses within a red/blue colored point denote a predicted flux of at least 10-13 erg cm-2 s-1 (10-14 erg cm-2 s-1) at 10 keV. The parameters of the X/gamma-ray and X-ray-only pulsars are shown with orange and black points, respectively, together with their 1 sigma uncertainty. The light cylinder Rlc of all pulsars is also noted (green pentagons). Uncertainties in the model parameters are larger (smaller) when only X-ray (both X- and GeV gamma-ray) data are available.

Reference: "Order Parameters for the high-energy spectra of pulsars"
D.F. Torres,
Nature Astronomy (2018), doi:10.1038/s41550-018-0384-5
26
February 2018

Stars in the Milky Way halo: Cosmic Space Invaders or Victims of Galactic Eviction?


Two stellar groups on opposite sides of the galactic plane originated by tidal interaction between the Milky Way and a satellite galaxy
A group of astronomers led by the Max Planck Institute for Astronomy (MPIA) and with participation of the Institute of Space Sciences (ICE, CSIC) and the Institute of Space Studies of Catalonia (IEEC) have investigated a small population of stars in the halo of the Milky Way Galaxy, finding its chemical composition to closely match that of the Galactic disk. This similarity provides compelling evidence that these stars have originated from within the disc, rather than from merged dwarf galaxies. The reason for this stellar migration is thought to be the theoretically proposed oscillations of the Milky Way disc as a whole, induced by the tidal interaction of the Milky Way’s dark matter halo with a passing massive satellite galaxy.

The stars investigated belong to two different structures located in the Galactic halo, the Triangulum-Andromeda (TriAnd) and A13 overdensities. These two structures are located on opposite sides of the Milky Way, about 14.000 light years below and above the Galactic plane (see Figure 1), and were initially thought to be the debris left behind by smaller galaxies that invaded the Milky Way in the past.

But in the study published today in Nature, astronomers present compelling evidence showing that these structures actually originate from the Milky Way's disc itself, but were kicked out towards the halo.
 
The key to understanding the origin of these stars lies in their detailed abundance patterns, obtained using the high-resolution spectra taken with the Keck and the VLT (Very Large Telescope, ESO) telescopes. "The analysis of chemical abundances is a very powerful test which allows, similarly to the DNA matching, to identify the parent population of the star. Different parent populations, such as the Milky Way disc or halo, dwarf satellite galaxies or globular clusters, are known to have radically different chemical compositions. So once we know what the stars are made of, we can immediately link them to their parent populations.”, explains M. Bergemann, the leading author of the study.

The comparison of the chemical composition of these stars shows that they are almost identical, both within and between groups. Even more surprisingly, their composition closely matches the typical abundance pattern of Milky Way disk stars. This provides compelling evidence that these stars likely originate from the Galactic thin disk itself, rather than being debris from the disruption of one or many of the smaller galaxies that are thought to have been accreted by our Galaxy in the past.

But how did the stars then get to these extreme positions above and below the Galactic disk? Models of the evolution of the Milky Way predict this "Galactic eviction" to happen as the result of oscillations of the Galactic disk as a whole. The favoured explanation for these oscillations is the tidal interaction of the Milky Way with a massive satellite galaxy.
The results published in Nature now provide the clearest evidence for these oscillations of the Milky Way's disk so far. These results indicate that the dynamics of the Milky Way's disk is significantly more complex than previously thought and disk stars can be relocated to distant locations from their birthplace.

“Future work includes the improved determination of the distances and motions of the stars in these overdensities, especially critical will be the data from the Gaia space mission. This will test our interpretation that the overdensities are the crests of the large-scale Galactic wave. Moreover, future determination of ages of the stars with asteroseismology will allow to date when the interaction of the Milky Way and the satellite galaxy happened.” said M. Bergemann and A. Serenelli.

Background informationThe results described here were published in Bergemann et al., “Two chemically similar stellar overdensities on opposite sides of the Galactic disc plane" in the journal Nature (http://dx.doi.org/ using the identifier 10.1038/nature25490)

Aldo Serenelli, from the Institute of Space Sciences (ICE, CSIC) and Institute of Space Studies of Catalonia (IEEC) in collaboration with Maria Bergemann (Max Planck Institute for Astronomy, MPIA) , Branimir Sesar (MPIA), Judith G. Cohen (California Institute of Technology), Allyson Sheffield (City University of New York), Ting S. Li (Fermi National Accelerator Laboratory), Luca Casagrande (The Australian National University), Kathryn Johnston and Chervin F.P. Laporte (both Columbia University, New York), Adrian M. Price-Whelan (Princeton University) and Ralph Schönrich (University of Oxford, UK), Andrew Gould (MPIA)
 
22
February 2018

PAZ launched succesfully


PAZ launched succesfully on Thursday 22 @ 15:17 CET
The satellite PAZ with instrumentation of Institute of Space Science (ICE, CSIC) and Institut d'Estudis Espacials de Catalunya (IEEC) has been launch this afternoon from California (USA).
15
February 2018

Black holes outpace galaxies in growth


Two new studies show that the growth of the biggest black holes is outrunning the rate of star formation in the galaxies they inhabit
Over many years, astronomers have gathered data on the formation of stars in galaxies and the growth of supermassive black holes (that is, those with millions or billions the mass of the Sun) in their centers. These data suggested that the black holes and the stars in their host galaxies grow in tandem with each other. 

Now, findings from two independent groups of researchers indicate that the black holes in massive galaxies have grown much faster than in the less massive ones.

“We are trying to reconstruct a race that started billions of years ago,” said Guang Yang of Penn State who led one of the two studies. “We are using extraordinary data taken from different telescopes to figure out how this cosmic competition unfolded.”

Using large amounts of data from NASA's Chandra X-ray Observatory, the Hubble Space Telescope and other observatories, Yang and his colleagues studied the growth rate of black holes in galaxies at distances of 4.3 to 12.2 billion light years from Earth. The X-ray data included the Chandra Deep Field-South & North and the COSMOS-Legacy surveys.

The scientists calculated the ratio between a supermassive black hole's growth rate and the growth rate of stars in its host galaxy. A common idea is that this ratio is approximately constant for all galaxies. 

Instead, Yang and colleagues found that this ratio is much higher for more massive galaxies. For galaxies containing about 100 billion solar masses worth of stars, the ratio is about ten times higher than it is for galaxies containing about 10 billion solar masses worth of stars.

“An obvious question is why?” said co-author Niel Brandt, also of Penn State. “Maybe massive galaxies are more effective at feeding cold gas to their central supermassive black holes than less massive ones.”

Another group of scientists independently found evidence that the most massive black holes’ growth has outstripped that of stars in their host galaxies. Mar Mezcua, of the Institute of Space Sciences (ICE, CSIC) and of the Institut d'Estudis Espacials de Catalunya (IEEC) in Spain, and her colleagues studied black holes in some of the brightest and most massive galaxies in the Universe. They studied 72 galaxies located at the center of galaxy clusters at distances ranging up to about 3.5 billion light years from Earth. The study used X-ray data from Chandra and radio data from the Australia Telescope Compact Array, the Karl G. Jansky Very Large Array and Very Long Baseline Array. 

Mezcua and her colleagues estimated the masses of black holes in these galaxy clusters by using a well-known relationship that connects the mass of a black hole to the X-ray and radio emission associated with the black hole. The black hole masses were found to be about ten times larger than masses estimated by another method using the assumption that the black holes and galaxies grew in tandem. 

“We found black holes that are far bigger than we expected,” said Mezcua. “Maybe they got a head start in this race to grow, or maybe they’ve had an edge in speed of growth that’s lasted billions of years.”

The researchers found that almost half of the black holes in their sample had masses estimated to be at least 10 billion times the mass of the Sun. This places them in an extreme weight category that some astronomers call “ultramassive” black holes.

"We know that black holes are extreme objects,” said co-author J. Hlavacek-Larrondo of the University of Montreal, “so it may not come as a surprise that the most extreme examples of them would break the rules we thought they should follow."

The work by Mezcua et al. was published in the February 2018 issue of Monthly Notices of the Royal Astronomical Society (MNRAS) and is available online (https://arxiv.org/abs/1710.10268). The paper by Yang et al. has been accepted and will appear in the April 2018 issue of the MNRAS (available online: https://arxiv.org/abs/1710.09399). 

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.
15
February 2018

Investigadores del Instituto de Ciencias del Espacio (ICE, CSIC) incorporan al satélite PAZ tecnología para detectar y cuantificar lluvias intensas


Lanzamiento del satélite PAZ con equipo del Instituto de Ciencias del Espacio
Un equipo de investigadores del Instituto de Ciencias del Espacio (ICE, CSIC) y del Instituto de Estudios Espaciales de Cataluña (IEEC) ha sido el encargado de diseñar e incorporar al satélite español de observación de la Tierra PAZ instrumentación capaz de detectar y cuantificar precipitaciones intensas. Las medidas que obtenga el satélite, cuyo lanzamiento está previsto para el próximo sábado, 17 de febrero, a las 15:17 hora peninsular española, servirán para profundizar en parámetros atmosféricos clave en la predicción del tiempo.

En concreto, los científicos han agregado una tecnología para realizar radio ocultaciones que, por primera vez, serán obtenidas en dos polarizaciones. Estas medidas, que se basan en el Sistema de Posicionamiento Global (GPS por sus siglas en inglés), dan pistas sobre las propiedades termodinámicas de la atmósfera (temperatura, presión y humedad) y, además, a diferentes alturas.

“Además de esto, la polarimetría nos permitirá probar cosas nuevas, conceptos de medida que nunca antes se habían planteado. En particular, utilizaremos la información de las dos polarizaciones recibidas para hacer medidas de precipitación intensa. Representaría el primer instrumento o sensor capaz de medir, simultáneamente, las propiedades termodinámicas y la precipitación intensa”, explica la investigadora del CSIC Estel Cardellach, que trabaja en el Instituto de Ciencias del Espacio.

Según la investigadora, es clave poder medir las lluvias intensas, difíciles de predecir. “En el contexto del cambio climático, donde se prevé que los fenómenos extremos sucedan más a menudo, los modelos de clima no se ponen del todo de acuerdo. Seguramente porque son fenómenos que no se han podido estudiar bien por falta de datos. Intentaremos que PAZ contribuya a solventar este problema”, agrega.

Las radio ocultaciones
Las radio ocultaciones son una técnica de observar un medio, normalmente la atmósfera de un planeta, utilizando dos elementos: uno que transmite señales radio o microondas (fuente) y otro elemento que los recibe (receptor). La particularidad de esta técnica es que, si se unen en línea recta los elementos transistor y receptor, esta cruza la Tierra, o sea, los elementos están ocultos por la Tierra. A pesar de ello, la señal sigue recibiéndose porque el rayo se flexiona.

“La clave está en relacionar la flexión de la trayectoria de la señal con las propiedades de la atmósfera. En el planeta Tierra, esta técnica se realiza con señales de los sistemas globales de navegación por satélite, como, por ejemplo, los GPS”, explica Cardellach.

Los sistemas de navegación son las fuentes, y un receptor a bordo de un satélite a baja altura orbital (como el satélite PAZ) contiene el receptor. El receptor puede medir con mucha precisión el ángulo de flexión de la señal, y de este ángulo se extraen perfiles verticales de temperatura, presión y humedad de la atmósfera.

El proyecto PAZEl satélite PAZ con tecnología radar es una misión dual, con aplicaciones civiles y militares. HISDESAT es la propietaria, operadora y explotadora del satélite, que ofrecerá información precisa para múltiples aplicaciones desde su órbita polar alrededor de la Tierra.

(Nota de prensa adaptada de la elaborada por el Departamento de Comunicación del CSIC)
12
February 2018

What gamma-ray pulsars are X-ray bright? And why?


Paper of Diego F. Torres in Nature Astronomy.
Neutron stars are a common compact endpoint of the life of stars. They have an extreme density (stars of about 10 km in size, with the mass of our Sun), and harbour the strongest magnetic fields (from 108 to 1014 times that of our Sun). Magnetized and rotating neutron stars emit beams of radiation, which can only be seen when the observer and the beam stand aligned. Periodic recurrence of such alignment gives rise to pulsations, and to the name pulsar used for these objects.

Pulsars were discovered 50 years ago, but many of their main characteristics are still elusive.

They emit at essentially all frequencies, and their energy distribution (that is, how much power they yield at each frequency band) is very varied. In fact, one of the most intriguing mysteries of pulsars relates to the origin of this spectral variety.

From the more than 2000 radio pulsars known, and the more than 200 gamma-ray pulsars known, we only know less than 20 X-ray pulsars.  This lack of pulsators in X-rays hampers having a global population understanding, as well as the ability of doing individual pulsar studies.

What makes a pulsar shine in gamma-rays and/or X-ray energies? Why some do at only one and not the other frequency? Ultimately, how can we predict, based on observations on only a part of the emission spectra, what will the pulsar emit in other bands?

Diego F. Torres,  director of the Institute of Space Sciences (ICE, CSIC) in Barcelona, ICREA Professor and also a member of  of the Institut d'Estudis Espacials de Catalunya (IEEC) has presented a theoretical model with which to handle these questions.

His results are published today in an article in Nature Astronomy.

Despite the extreme precision of the observations, and the underlying complexity of the processes involved, just four physical parameters suffice in his model to fit the spectrum of all gamma and/or X-ray pulsars known.

When analyzing the fitting for all pulsars, grouping of these parameters and relevant correlations appear, explaining the different observational behaviors.

"This model answers at once what process is behind the emission spectra and how the spectral variety arises. It explains intricacies such as why we have detected flat spectra at low and high energies. And most importantly, it provides a predictive tool by which to identify new X-ray pulsars."

In fact, testing of the model with archival data has proven that it correctly pinpoint already known pulsars, and has already lead to new detections.

It is expected that via the use of the model by Prof. Torres, not only we shall understand the physics of these objects better, but that the population of pulsars detected at X-ray energies will rise notably.

To read the original article:
"Order Parameters for the high-energy spectra of pulsars"
D. F. Torres
Nature Astronomy (2018), DOI: 10.1038 / s41550-018-0384-5 (http://dx.doi.org).
 
09
February 2018

11 de febrero, es el Día Internacional de la Mujer y la Niña en la Ciencia


11 de febrero, es el Día Internacional de la Mujer y la Niña en la Ciencia
11 de febrero, es el Día Internacional de la Mujer y la Niña en la Ciencia. Las mujeres que trabajamos en el Instituto de Ciencias del Espacio (ICE, CSIC) y en el Institut d'Estudis Espacials de Catalunya (IEEC) celebramos este día, y también el resto del año, nuestra pasión por la Astrofísica.
05
February 2018

ESA creates quietest place in space


LISA Pathfinder new Results
ESA creates quietest place in space
 
Imagine a packed party: music is blaring and you can feel the bass vibrate in your chest, lights are flashing, balloons are falling from the ceiling and the air is filled with hundreds of separate conversations. At the same time your cell phone is vibrating in your pocket and your drink is fizzing in the glass. Now imagine you can block out this assault on your senses to create a perfectly quiet bubble around you, only letting in the unmistakable voice of your best friend who’s trying to get your attention from the other side of the room.
 
Applied to the grand scale of the Universe, that’s a bit like the level of noise detection and reduction ESA has proven with its LISA Pathfinder mission in order to create the quietest place in space. Why? To set the stage for its successor, LISA, to detect gravitational waves from high-energy events in space. 
 
Gravitational waves are ripples in the fabric of spacetime that travel out from the source. Even as you accidentally bump into someone at the crowded party you make a gravitational wave, but it is so insignificantly small as to be undetectable. You need the interaction between attention-seeking objects with a large gravity, something as large and powerful as the collision of two black holes, or the explosion of a dying star, or the dance of two super-dense neutron stars spinning wildly around one another, to create any noticeable ripple in spacetime.
 
But even then the distortion effects are at the minuscule scale of a few millionths of a millionth of a metre over a distance of a million kilometres. You wouldn’t even notice if such a gravitational wave passed through you while you were reading this article, but yet the Universe is teeming with their echoes.
 
The trick in detecting them is first to reduce all external noises, and then look out for the minute stretch-and-squeeze effect by the change they induce to space, which can be measured, for example, using a laser beam. That is, if the space between two points gets stretched it takes longer for the laser beam to go from one point to another; conversely, if it gets compressed, the beam reaches the second point slightly quicker.
 
This concept has already been proven on Earth with the Laser Interferometer Gravitational-Wave Observatory, LIGO, and the Virgo observatory. These facilities, operated by an international collaboration of over a thousand scientists, comprise pairs of either three or four km-long ‘arms’ at 90º to one another, each equipped with a laser beam and mirror system. As a gravitational wave passes through, the lengths of the arms are lengthened and shortened respectively by a minuscule fraction, tiny but enough to be noticeable as a change in the reflected laser pattern by the highly accurate equipment. This was first achieved in 2015 when a gravitational wave was recorded, produced by a pair of coalescing black holes several tens the mass of our Sun, about 1.3 billion light-years away. With the detection of this brief 0.2 second signal, Einstein’s century-old prediction about the very existence of gravitational waves was proven right.
 
However, Earth detectors have limited space and they cannot escape external influences, ranging from vehicles passing by to local seismic activity. Their size is great for detecting high-frequency (10–1000 Hz) gravitational waves, like those coming from coalescing pairs of stellar-mass black holes or neutron stars, but isn’t sensitive to lower frequency waves (0.00002–0.1 Hz) generated by supermassive black holes a million times more massive than the Sun. In addition, a cosmological background of gravitational waves covering the entire spectrum down to even lower frequencies (0.000000000000001 Hz)  are thought to be produced by the formation of Universe itself in the theorised phase of ‘inflation’, the brief, accelerated expansion in its first moments 13.8 billion years ago.
 
To access the lower-frequency waves, we need to use the playground of space. Enter ESA’s Laser Interferometer Space Antenna – LISA – a three-satellite fleet that will create a triangular formation separated by 2.5 million km and connected by laser beams, following Earth in orbit around the Sun. Such an endeavour, planned for launch in 2034, is pushing the boundaries of current technology.
 
Indeed, the key requirement for a space mission to measure any possible distortion caused by a passing gravitational wave is that it is isolated from all external and internal forces, which are present even in space, except gravity. To prove the fundamental concept of such a mission, ESA and its partners built LISA Pathfinder, which successfully concluded last year, having demonstrated that offending internal and external ‘noise’ sources could indeed be removed to provide the quiet environment needed to make gravitational wave detections with the full-size LISA mission.
 
To achieve this, the technology demonstrator mission used two 2 kg free-falling cubes separated by 38 cm and linked by lasers. The spacecraft acted as a shield around them, protecting them from external sources. It manoeuvred around them using tiny micro-newton thrusters to oppose solar radiation pressure and wind of particles, sensing the test mass motion and adjusting its own to compensate: essentially flying to within an accuracy of a few billionths of a metre and being able to sense the relative positions of the metal cubes to within a trillionth of a metre.
 
The mission already outperformed itself[Emily Bal1]  in the first week of operations, and now the final report card is in, showing that it even surpassed some of the requirements for its next-generation successor. These results are published today [EB2] in Physical Review Letters.
The improvements since the initial two months dataset focused on the lower frequencies, since at higher frequencies, between 60 mHz and 1 Hz, the mission’s precision was limited only by the sensing noise of the equipment used to monitor the position and orientation of the test masses.
 
After many more months in space, the data showed a 10-fold reduction in the effect of escaping residual gas pressure inside the spacecraft, which caused gas molecules to bounce off the cubes – just as gas bubbles in your fizzy drink bounce off ice cubes or the glass, and the drink eventually goes ‘flat’.
 
More data also led to improved understanding of the small inertial force acting on the cubes caused by a combination of the shape of LISA Pathfinder’s orbit and the effect of the noise in the signal of the startrackers used to orient it – improved control in LISA will eliminate this force further.
 
A more accurate calculation of the electrostatic forces of the onboard electrical systems and magnetic fields has also now eliminated a systematic source of low-frequency noise.

Importantly, statistical analysis has allowed scientists to remove the effects of additional sporadic events to measure the noise at even lower frequencies than expected, down to 0.00002 Hz, essentially creating the quietest place in space. Overall, this proves that measurements at the low frequencies needed for LISA can be realised. It means that instead of only being able to detect a passing gravitational wave from a single event for a fraction of a second, LISA will be able to detect month- or even years-long chatter of multiple signals.
 
Furthermore, it will be sensitive to the first signs of a supermassive black hole merger, weeks before it has fully collided. This will give time to alert other ground- or space-based observatories so that they can also tune in to study the object at a range of other complementary wavelengths.
 
The mission will also likely uncover other currently unknown exotic sources of gravitational waves.
 
It will then be up to Europe’s next generation of scientists to decipher which soundtrack emanates from which mysterious broadcaster in the Universe, giving us all VIP access to the guest list at the gravitational wave party.
 
The Gravitational Astronomy-LISA group of the Institute of Space Sciences (ICE, CSIC) and of the Institute of Space Studies of Catalonia (IEEC) has lead the Spanish contribution to the LISA Pathfinder mission, the Data and Diagnostic Subsystem (DDS), and is currently leading the developments for the LISA mission.  Miquel Nofrarias, member of the group and of the LISA Instrument Group, says: “LISA Pathfinder has been the first gravitational laboratory in orbit and, as such, has required intense planning and monitoring during operations. The results and experience that we have acquired will be crucial for the success of the future gravitational wave observatory, LISA”.  Carlos F. Sopuerta, also member of the group and of the LISA consortium Board says: “The performance of LISA Pathfinder is incredible and very encouraging for the development of LISA.  This gives us even more confidence that with LISA we can make revolutionary discoveries with impact in Astrophysics, Cosmology, and Fundamental Physics”.
 
Notes for Editors
 “Beyond the Required LISA Free Fall Performance: New LISA Pathfinder Results down to 20μHz” by Armano et al., is published in Physical Review Letters (https://link.aps.org/doi/10.1103/PhysRevLett.120.061101)
LISA Pathfinder is an ESA mission with important contributions from its member states and NASA.
The LISA Technology Package payload has been delivered by several national funding agencies and ESA, in particular: Italy (ASI), Germany (DLR), the United Kingdom (UKSA), France (CNES), Spain (MINECO), Switzerland (SSO), and the Netherlands (SRON). LISA Pathfinder also carries the Disturbance Reduction System payload, provided by NASA.
LISA recently passed its Mission Definition Review, during which the design feasibility and the science and technology requirements are reviewed and defined. The mission is scheduled for launch in 2034.
 
For more information, please contact:
Dr. Carlos F. Sopuerta and Dr. Miquel Nofrarias
Institute of Space Sciences (ICE, CSIC) and Institute of Space Studies of Catalonia (IEEC)
Campus UAB
Carrer de Can Magrans s/n
08193 Cerdanyola del Vallès
Phone: + 34 93 737 9788 (ext. 933021)
sopuerta@ice.csic.es
nofrarias@ice.cat
 
Paul McNamara
LISA Pathfinder Project Scientist
European Space Agency
Tel: +31 71 565 8239
Email: paul.mcnamara@esa.int
 
Stefano Vitale
LISA Technology Package Principal Investigator
University of Trento and INFN, Italy
Tel: +39 046 128 1568
Email: stefano.vitale@unitn.it
 
Karsten Danzmann
LISA Technology Package Co-Principal Investigator
Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Leibniz University, Hannover, Germany
Phone: +49 511 762 2356
Email: Karsten.Danzmann@aei.mpg.de
 
Markus Bauer
ESA Science Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int
 
Graphics:
+ http://www.esa.int/spaceinvideos/Videos/2015/09/Gravitational_waves
+ http://www.esa.int/spaceinvideos/Videos/2015/11/Inside_LISA_Pathfinder_with_narration
+ new graphs below

Short: LISA Pathfinder performance analysis
Long: Analysis of the LISA Pathfinder mission results towards the end of the mission (red line) compared with the first results published shortly after the spacecraft began science operations (blue line). The initial requirements (top, wedge-shaped area) and that of the future gravitational wave detection mission LISA (middle, striped area) are included for comparison, and show that it far exceeded expectations.
 
At the heart of the LISA Pathfinder spacecraft, two identical, 2 kg, 46 mm gold–platinum cubes were falling freely through space under the influence of gravity alone. The LISA Pathfinder team measured the remaining forces acting on the test masses, and identified the main sources of noise, depending on the frequency.
 
Compared with the initial results [EB4] following the first two months of science operations, statistical analysis over the larger dataset allowed scientists to measure the noise at even lower frequencies than expected, down to 20 µHz.
 
In addition, the many more months in space allowed a 10-fold reduction in the effect of escaping residual gas pressure inside the spacecraft, which caused gas molecules to bounce off the cubes. More data also led to improved understanding of the small inertial force acting on the cubes caused by a combination of the shape of LISA Pathfinder’s orbit and the effect of the noise in the signal of the startrackers used to orient it. A more accurate calculation of the electrostatic forces of the onboard electrical systems and magnetic fields has also now eliminated a systematic source of low-frequency noise.
 
Overall, the results show that LISA Pathfinder has clearly surpassed its original requirements, reaching a level of precision closer to that required by the future gravitational-wave observatory, LISA.
 
http://www.esa.int/Our_Activities/Space_Science/LISA_Pathfinder_exceeds_expectations
https://link.aps.org/doi/10.1103/PhysRevLett.120.061101
http://www.aei.mpg.de/2201298/lisa-mdr
http://sci.esa.int/LISA-pathfinder/57869-LISA-pathfinder-performance/
Institute of Space Sciences (IEEC-CSIC)

Campus UAB, Carrer de Can Magrans, s/n
08193 Barcelona.
Phone: +34 93 737 9788
Email: ice@ice.csic.es
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya