Tuesday, February 28, 2017

Science checkout continues for ExoMars orbiter

Title ExoMars science orbit 6–7 March
Copyright ESA, CC BY-SA 3.0 IGO - Hi-res image

ExoMars first year in orbit
Copyright: ESA


Next week, the ExoMars orbiter will devote two days to making important calibration measurements at the Red Planet, which are needed for the science phase of the mission that will begin next year.

The Trace Gas Orbiter (TGO), a joint endeavour between ESA and Roscosmos, arrived at Mars on 19 October. During two dedicated orbits in late November, the science instruments made their first calibration measurements since arriving at Mars. These included images of Mars and one of its moons, Phobos, and basic spectral analyses of the martian atmosphere.

At that time, the orbiter was in a highly elliptical path that took it from between 230 and 310 km above the surface to around 98 000 km every 4.2 days.

The main science mission will only begin once it reaches a near-circular orbit about 400 km above the planet’s surface after a year of ‘aerobraking’ – using the atmosphere to gradually brake and change its orbit.

Earlier this year, in preparation for the aerobraking phase, TGO conducted a series of manoeuvres to shift its angle of travel with respect to the planet’s equator to almost 74º. This raised it from a near-equatorial arrival orbit to one that flies over more of the northern and southern hemispheres.

This inclination will provide optimum coverage of the surface for the science instruments, while still offering good visibility for relaying data from current and future landers – including the ExoMars rover scheduled for launch in 2020.

Now, before the year-long aerobraking phase begins on 15 March, the science teams once again have the opportunity to make important calibration measurements, focusing mainly on tests to check the pointing and tracking of the instruments, but this time from the new orbit.

The spacecraft’s new one-day orbit takes it from 37 150 km at its farthest and to within about 200 km of the planet’s surface at its closest approach, which will also allow some of the closest images of the mission to be obtained.

TGO’s two spectrometer suites will make some preliminary calibration observations on 28 February and 1 March while the spacecraft’s instruments are facing towards Mars, with the main campaign taking place 5–7 March, covering two complete orbits of the planet.

During the main campaign, the spectrometers will be able to test another operational mode, such as scanning towards the horizon at sunlight scattered by the atmosphere.

By looking at how the sunlight is influenced by the atmosphere, scientists will be able to analyse the atmospheric constituents of Mars – TGO’s main science goal.

Indeed, TGO is tasked with making a detailed inventory of the atmosphere, particularly those gases that are present only in trace amounts. Of high interest is methane, which on Earth is produced primarily by biological activity or geological processes such as some hydrothermal reactions.

The spacecraft will also seek out water or ice just below the surface, and will provide colour and stereo context images of surface features, including those that may be related to possible trace gas sources.

During the upcoming observations, and in addition to pointing directly at the planet’s surface, the camera will also take important dark sky and star field calibration measurements.

Meanwhile TGO’s neutron detector will be on throughout the two orbits in order to calibrate the background flux.

“It’s great we have the opportunity to squeeze in these important observations during this very busy time preparing for the year-long aerobraking phase,” says Håkan Svedhem, ESA’s TGO project scientist. “While the aerobraking is taking place, the science teams will be able to use these essential calibration measurements to best prepare for the start of the main mission when we arrive in our science orbit next year.”


For more information, please contact:

Markus Bauer








ESA Science and Robotic Exploration Communication Officer









Tel: +31 71 565 6799









Mob: +31 61 594 3 954










Håkan Svedhem
ESA ExoMars TGO Project Scientist

Source: ESA/EXOMARS

Monday, February 27, 2017

NASA's Fermi Finds Possible Dark Matter Ties in Andromeda Galaxy

NASA’s Fermi telescope has detected a gamma-ray excess at the center of the Andromeda galaxy that's similar to a signature Fermi previously detected at the center of our own Milky Way. Watch to learn more. Credits: NASA’s Goddard Space Flight Center/Scott Wiessinger, producer 

The gamma-ray excess (shown in yellow-white) at the heart of M31 hints at unexpected goings-on in the galaxy's central region. Scientists think the signal could be produced by a variety of processes, including a population of pulsars or even dark matter.  Credits: NASA/DOE/Fermi LAT Collaboration and Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF


NASA’s Fermi Gamma-ray Space Telescope has found a signal at the center of the neighboring Andromeda galaxy that could indicate the presence of the mysterious stuff known as dark matter. The gamma-ray signal is similar to one seen by Fermi at the center of our own Milky Way galaxy.

Gamma rays are the highest-energy form of light, produced by the universe’s most energetic phenomena. They’re common in galaxies like the Milky Way because cosmic rays, particles moving near the speed of light, produce gamma rays when they interact with interstellar gas clouds and starlight.

Surprisingly, the latest Fermi data shows the gamma rays in Andromeda — also known as M31 — are confined to the galaxy’s center instead of spread throughout. To explain this unusual distribution, scientists are proposing that the emission may come from several undetermined sources. One of them could be dark matter, an unknown substance that makes up most of the universe.

“We expect dark matter to accumulate in the innermost regions of the Milky Way and other galaxies, which is why finding such a compact signal is very exciting,” said lead scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research and the Research Institute in Astrophysics and Planetology in Toulouse, France. “M31 will be a key to understanding what this means for both Andromeda and the Milky Way.”

A paper describing the results will appear in an upcoming issue of The Astrophysical Journal.

Another possible source for this emission could be a rich concentration of pulsars in M31’s center. These spinning neutron stars weigh as much as twice the mass of the sun and are among the densest objects in the universe. One teaspoon of neutron star matter would weigh a billion tons on Earth. Some pulsars emit most of their energy in gamma rays. Because M31 is 2.5 million light-years away, it’s difficult to find individual pulsars. To test whether the gamma rays are coming from these objects, scientists can apply what they know about pulsars from observations in the Milky Way to new X-ray and radio observations of Andromeda.

Now that Fermi has detected a similar gamma-ray signature in both M31 and the Milky Way, scientists can use this information to solve mysteries within both galaxies. For example, M31 emits few gamma rays from its large disk, where most stars form, indicating fewer cosmic rays roaming there. Because cosmic rays are usually thought to be related to star formation, the absence of gamma rays in the outer parts of M31 suggests either that the galaxy produces cosmic rays differently, or that they can escape the galaxy more rapidly. Studying Andromeda may help scientists understand the life cycle of cosmic rays and how it is connected to star formation.

“We don’t fully understand the roles cosmic rays play in galaxies, or how they travel through them,” said Xian Hou, an astrophysicist at Yunnan Observatories, Chinese Academy of Sciences in Kunming, China, also a lead scientist in this work. “M31 lets us see how cosmic rays behave under conditions different from those in our own galaxy.”

The similar discovery in both the Milky Way and M31 means scientists can use the galaxies as models for each other when making difficult observations. While Fermi can make more sensitive and detailed observations of the Milky Way’s center, its view is partially obscured by emission from the galaxy’s disk. But telescopes view Andromeda from an outside vantage point impossible to attain in the Milky Way.

“Our galaxy is so similar to Andromeda, it really helps us to be able to study it, because we can learn more about our galaxy and its formation,” said co-author Regina Caputo, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s like living in a world where there’s no mirrors but you have a twin, and you can see everything physical about the twin.” 

While more observations are necessary to determine the source of the gamma-ray excess, the discovery provides an exciting starting point to learn more about both galaxies, and perhaps about the still elusive nature of dark matter.

“We still have a lot to learn about the gamma-ray sky,” Caputo said. “The more information we have, the more information we can put into models of our own galaxy.”

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.


For more information on Fermi, visit:  http://www.nasa.gov/fermi


Editor: Rob Garner


Saturday, February 25, 2017

Cosmic blast from the past

New image of SN 1987A

PR Image heic1704b
Supernova 1987A over time

PR Image heic1704c
Composite image of supernova 1987A



Videos

Time-lapse of SN 1987A and its ring
Time-lapse of SN 1987A and its ring

Simulation of SN 1987A
Simulation of SN 1987A

Zoom in on SN 1987A
Zoom in on SN 1987A



Hubble captures 30th anniversary image of supernova 1987A

Three decades ago, a massive stellar explosion sent shockwaves not only through space but also through the astronomical community. SN 1987A was the closest observed supernova to Earth since the invention of the telescope and has become by far the best studied of all time, revolutionising our understanding of the explosive death of massive stars.

Located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, Supernova 1987A is the nearest supernova explosion observed in hundreds of years. It marked the end of the life of a massive star and sent out a shockwave of ejected material and bright light into space. The light finally reached Earth on 23 February 1987 — like a cosmic blast from the past.

The NASA/ESA Hubble Space Telescope has been on the front line of observations of SN 1987A since 1990 and has taken a look at it many times over the past 27 years. To celebrate the 30th anniversary of the supernova and to check how its remnant has developed, Hubble took another image of the distant explosion in January 2017, adding to the existing collection.

Because of its early detection and relative proximity to Earth, SN 1987A has become the best studied supernova ever. Prior to SN 1987A, our knowledge of supernovae was simplistic and idealised. But by studying the evolution of SN 1987A from supernova to supernova remnant in superb detail, using telescopes in space and on the ground, astronomers have gained revolutionary insights into the deaths of massive stars.

Back in 1990, Hubble was the first to see the event in high resolution, clearly imaging the main ring that blazes around the exploded star. It also discovered the two fainter outer rings, which extend like mirror images in a hourglass-shaped structure. Even today, the origin of these structures is not yet fully understood.

However, by observing the expanding remnant material over the years, Hubble helped to show that the material within this structure was ejected 20 000 years before the actual explosion took place. Its shape at first surprised astronomers, who expected the dying star to eject material in a spherical shape — but faster stellar winds likely caused the slower material to pile up into ring-like structures.

The initial burst of light from the supernova illuminated the rings. They slowly faded over the first decade after the explosion, until the shock wave of the supernova slammed into the inner ring in 2001, heating the gas to searing temperatures and generating strong X-ray emission. Hubble’s observations of this process shed light on how supernovae can affect the dynamics and chemistry of their surrounding environment, and thus shape galactic evolution.



More Information


The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Image credit: NASA, ESA, R. Kirshner, P. Challis, ESO/NAOJ/NRAO/A. Angelich, NASA/CXC/SAO.



 Links



Contacts

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


Source: ESA/news

Friday, February 24, 2017

ALMA’s Hole in the Universe

Credit: ALMA (ESO/NAOJ/NRAO)/T. Kitayama (Toho University, Japan)/ESA/Hubble & NASA


The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the Universe. As it was created nearly 14 billion years ago, this light — which exists now as weak microwave radiation and is thus named the cosmic microwave background (CMB) — has now expanded to permeate the entire cosmos, filling it with detectable photons.

The CMB can be used to probe the cosmos via something known as the Sunyaev-Zel’dovich (SZ) effect, which was first observed over 30 years ago. We detect the CMB here on Earth when its constituent microwave photons travel to us through space. On their journey to us, they can pass through galaxy clusters that contain high-energy electrons. These electrons give the photons a tiny boost of energy. Detecting these boosted photons through our telescopes is challenging but important — they can help astronomers to understand some of the fundamental properties of the Universe, such as the location and distribution of dense galaxy clusters.

This image shows the first measurements of the thermal Sunyaev-Zel’dovich effect from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile (in blue). Astronomers combined data from ALMA’s 7- and 12-metre antennas to produce the sharpest possible image. The target was one of the most massive known galaxy clusters, RX J1347.5–1145, the centre of which shows up here in the dark “hole” in the ALMA observations. The energy distribution of the CMB photons shifts and appears as a temperature decrease at the wavelength observed by ALMA, hence a dark patch is observed in this image at the location of the cluster. 

Links



Thursday, February 23, 2017

Ultracool Dwarf and the Seven Planets

 PR Image eso1706a
Artist’s impression of the TRAPPIST-1 planetary system 

PR Image eso1706b
Comparison of the TRAPPIST-1 system with the inner Solar System and the Galilean Moons of Jupiter 

PR Image eso1706c
Comparison of the TRAPPIST-1 system with the inner Solar System and the Galilean Moons of Jupiter

Comparison of the sizes of the TRAPPIST-1 planets with Solar System bodies

PR Image eso1706e
Light curve of TRAPPIST-1 — showing the dimming events caused by transits of planets 

PR Image eso1706f
The orbits of the seven planets around TRAPPIST-1 

PR Image eso1706g
VLT observations of the light curve of TRAPPIST-1 during the triple transit of 11 December 2015 

PR Image eso1706h
Light curves of the seven TRAPPIST-1 planets as they transit

Comparison of the TRAPPIST-1 system and the inner Solar System 

PR Image eso1706j
The ultracool dwarf star TRAPPIST-1 in the constellation of Aquarius 

PR Image eso1706k
Comparison between the Sun and the ultracool dwarf star TRAPPIST-1

Artist’s impression of view from planet in the TRAPPIST-1 planetary system 

Artist's illustrations of planets in TRAPPIST-1 system and Solar System’s rocky planets

Artist’s impression of the TRAPPIST-1 system

Comparing the TRAPPIST-1 planets

Seven planets orbiting the ultracool dwarf star TRAPPIST-1
 
Artist’s impression of view from distant planet in the TRAPPIST-1 planetary system

Artist’s impression of view from one of the middle planets in the TRAPPIST-1 planetary system 



Videos
ESOcast 96: Ultracool Dwarf and the Seven Planets

ESOcast 97 Light: 7 Earth-sized Worlds Found in Nearby Star System (4K UHD)

Animation of the planets orbiting TRAPPIST-1

Fly-through of the TRAPPIST-1 planetary system
Fly-through of the TRAPPIST-1 planetary system

A trip to TRAPPIST-1 and its seven planets
A trip to TRAPPIST-1 and its seven planets

Travelling from Earth to TRAPPIST-1
Travelling from Earth to TRAPPIST-1

Animation of the planets in orbit around TRAPPIST-1
Animation of the planets in orbit around TRAPPIST-1

View from the planetTRAPPIST-1f
View from the planetTRAPPIST-1f

View from above the surface of TRAPPIST-1b
View from above the surface of TRAPPIST-1b

Fulldome video of the TRAPPIST-1 system
Fulldome video of the TRAPPIST-1 system

Virtual reality view of the TRAPPIST-1 planetary system
Virtual reality view of the TRAPPIST-1 planetary system

TRAPPIST-1 planetary system seen from above (fulldome)



Temperate Earth-sized Worlds Found in Extraordinarily Rich Planetary System

Astronomers have found a system of seven Earth-sized planets just 40 light-years away. Using ground and space telescopes, including ESO’s Very Large Telescope, the planets were all detected as they passed in front of their parent star, the ultracool dwarf star known as TRAPPIST-1. According to the paper appearing today in the journal Nature, three of the planets lie in the habitable zone and could harbour oceans of water on their surfaces, increasing the possibility that the star system could play host to life. This system has both the largest number of Earth-sized planets yet found and the largest number of worlds that could support liquid water on their surfaces.

Astronomers using the TRAPPIST–South telescope at ESO’s La Silla Observatory, the Very Large Telescope (VLT) at Paranal and the NASA Spitzer Space Telescope, as well as other telescopes around the world [1], have now confirmed the existence of at least seven small planets orbiting the cool red dwarf star TRAPPIST-1 [2]. All the planets, labelled TRAPPIST-1b, c, d, e, f, g and h in order of increasing distance from their parent star, have sizes similar to Earth [3].

Dips in the star’s light output caused by each of the seven planets passing in front of it — events known as transits — allowed the astronomers to infer information about their sizes, compositions and orbits [4]. They found that at least the inner six planets are comparable in both size and temperature to the Earth.

Lead author Michaël Gillon of the STAR Institute at the University of Liège in Belgium is delighted by the findings: “This is an amazing planetary system — not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth!”

With just 8% the mass of the Sun, TRAPPIST-1 is very small in stellar terms — only marginally bigger than the planet Jupiter — and though nearby in the constellation Aquarius (The Water Carrier), it appears very dim. Astronomers expected that such dwarf stars might host many Earth-sized planets in tight orbits, making them promising targets in the hunt for extraterrestrial life, but TRAPPIST-1 is the first such system to be found.

Co-author Amaury Triaud expands: “The energy output from dwarf stars like TRAPPIST-1 is much weaker than that of our Sun. Planets would need to be in far closer orbits than we see in the Solar System if there is to be surface water. Fortunately, it seems that this kind of compact configuration is just what we see around TRAPPIST-1!”

The team determined that all the planets in the system are similar in size to Earth and Venus in the Solar System, or slightly smaller. The density measurements suggest that at least the innermost six are probably rocky in composition.

The planetary orbits are not much larger than that of Jupiter’s Galilean moon system, and much smaller than the orbit of Mercury in the Solar System. However, TRAPPIST-1’s small size and low temperature mean that the energy input to its planets is similar to that received by the inner planets in our Solar System; TRAPPIST-1c, d and f receive similar amounts of energy to Venus, Earth and Mars, respectively.

All seven planets discovered in the system could potentially have liquid water on their surfaces, though their orbital distances make some of them more likely candidates than others. Climate models suggest the innermost planets, TRAPPIST-1b, c and d, are probably too hot to support liquid water, except maybe on a small fraction of their surfaces. The orbital distance of the system’s outermost planet, TRAPPIST-1h, is unconfirmed, though it is likely to be too distant and cold to harbour liquid water — assuming no alternative heating processes are occurring [5]. TRAPPIST-1e, f, and g, however, represent the holy grail for planet-hunting astronomers, as they orbit in the star’s habitable zone and could host oceans of surface water [6].

These new discoveries make the TRAPPIST-1 system a very important target for future study. The NASA/ESA Hubble Space Telescope is already being used to search for atmospheres around the planets and team member Emmanuël Jehin is excited about the future possibilities: “With the upcoming generation of telescopes, such as ESO’s European Extremely Large Telescope and the NASA/ESA/CSA James Webb Space Telescope, we will soon be able to search for water and perhaps even evidence of life on these worlds.”



Notes


[1] As well as the NASA Spitzer Space Telescope, the team used many ground-based facilities: TRAPPIST–South at ESO’s La Silla Observatory in Chile, HAWK-I on ESO’s Very Large Telescope in Chile,  TRAPPIST–North in Morocco, the 3.8-metre UKIRT in Hawaii, the 2-metre Liverpool and 4-metre William Herschel telescopes at La Palma in the Canary Islands, and the 1-metre SAAO telescope in South Africa.

[2] TRAPPIST–South (the TRAnsiting Planets and PlanetesImals Small Telescope–South) is a Belgian 0.6-metre robotic telescope operated from the University of Liège and based at ESO’s La Silla Observatory in Chile. It spends much of its time monitoring the light from around 60 of the nearest ultracool dwarf stars and brown dwarfs (“stars” which are not quite massive enough to initiate sustained nuclear fusion in their cores), looking for evidence of planetary transits. TRAPPIST–South, along with its twin TRAPPIST–North, are the forerunners to the SPECULOOS system, which is currently being installed at ESO’s Paranal Observatory.

[3] In early 2016, a team of astronomers, also led by Michaël Gillon announced the discovery of three planets orbiting TRAPPIST-1. They intensified their follow-up observations of the system mainly because of a remarkable triple transit that they observed with the HAWK-I instrument on the VLT. This transit showed clearly that at least one other unknown planet was orbiting the star. And that historic light curve shows for the first time three temperate Earth-sized planets, two of them in the habitable zone, passing in front of their star at the same time!

[4] This is one of the main methods that astronomers use to identify the presence of a planet around a star. They look at the light coming from the star to see if some of the light is blocked as the planet passes in front of its host star on the line of sight to Earth — it transits the star, as astronomers say. As the planet orbits around its star, we expect to see regular small dips in the light coming from the star as the planet moves in front of it.

[5] Such processes could include tidal heating, whereby the gravitational pull of TRAPPIST-1 causes the planet to repeatedly deform, leading to inner frictional forces and the generation of heat. This process drives the active volcanism on Jupiter's moon Io. If TRAPPIST-1h has also retained a primordial hydrogen-rich atmosphere, the rate of heat loss could be very low.

[6] This discovery also represents the largest known chain of exoplanets orbiting in near-resonance with each other. The astronomers carefully measured how long it takes for each planet in the system to complete one orbit around TRAPPIST-1 — known as the revolution period — and then calculated the ratio of each planet’s period and that of its next more distant neighbour. The innermost six TRAPPIST-1 planets have period ratios with their neighbours that are very close to simple ratios, such as 5:3 or 3:2. This means that the planets most likely formed together further from their star, and have since moved inwards into their current configuration. If so, they could be low-density and volatile-rich worlds, suggesting an icy surface and/or an atmosphere.



More Information

This research was presented in a paper entitled “Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1”, by M. Gillon et al., to appear in the journal Nature.

The team is composed of M. Gillon (Université de Liège, Liège, Belgium), A. H. M. J. Triaud (Institute of Astronomy, Cambridge, UK), B.-O. Demory (University of Bern, Bern, Switzerland; Cavendish Laboratory, Cambridge, UK), E. Jehin (Université de Liège, Liège, Belgium), E. Agol (University of Washington, Seattle, USA; NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, USA), K. M. Deck (California Institute of Technology, Pasadena, CA, USA), S. M. Lederer (NASA Johnson Space Center, Houston, USA), J. de Wit (Massachusetts Institute of Technology, Cambridge, MA, USA), A. Burdanov (Université de Liège, Liège, Belgium), J. G. Ingalls (California Institute of Technology, Pasadena, California, USA), E. Bolmont (University of Namur, Namur, Belgium; Laboratoire AIM Paris-Saclay, CEA/DRF - CNRS - Univ. Paris Diderot - IRFU/SAp, Centre de Saclay, France), J. Leconte (Univ. Bordeaux, Pessac, France), S. N. Raymond (Univ. Bordeaux, Pessac, France), F. Selsis (Univ. Bordeaux, Pessac, France), M. Turbet (Sorbonne Universités, Paris, France), K. Barkaoui (Oukaimeden Observatory, Marrakesh, Morocco), A. Burgasser (University of California, San Diego, California, USA), M. R. Burleigh (University of Leicester, Leicester, UK), S. J. Carey (California Institute of Technology, Pasadena, CA, USA), A. Chaushev (University of Leicester, UK), C. M. Copperwheat (Liverpool John Moores University, Liverpool, UK), L. Delrez (Université de Liège, Liège, Belgium; Cavendish Laboratory, Cambridge, UK), C. S. Fernandes (Université de Liège, Liège, Belgium), D. L. Holdsworth (University of Central Lancashire, Preston, UK), E. J. Kotze (South African Astronomical Observatory, Cape Town, South Africa), V. Van Grootel (Université de Liège, Liège, Belgium), Y. Almleaky (King Abdulaziz University, Jeddah, Saudi Arabia; King Abdullah Centre for Crescent Observations and Astronomy, Makkah Clock, Saudi Arabia), Z. Benkhaldoun (Oukaimeden Observatory, Marrakesh, Morocco), P. Magain (Université de Liège, Liège, Belgium), and D. Queloz (Cavendish Laboratory, Cambridge, UK; Astronomy Department, Geneva University, Switzerland).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, 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. 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, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.



Links



Contacts


Michaël Gillon
University of Liege
Liege, Belgium
Tel: +32 43 669 743
Cell: +32 473 346 402
Email:
michael.gillon@ulg.ac.be

Amaury Triaud
Kavli Exoplanet Fellow, University of Cambridge
Cambridge, United Kingdom
Tel: +44 1223 766 690
Cell: +44 747 0087 217
Email:
aht34@cam.ac.uk

Emmanuël Jehin
University of Liège
Liège, Belgium
Tel: +32 495237298
Email:
ejehin@ulg.ac.be

Brice-Olivier Demory
University of Bern
Bern, Switzerland
Tel: +41 31 631 51 57
Cell: +44 78 66 476 486
Email:
brice.demory@csh.unibe.ch

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

Source: ESO

Wednesday, February 22, 2017

Tune your radio: galaxies sing while forming stars

The radio observations were based on the KINGFISH (“Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel”) sample of galaxies. The compilation shows composite infrared images of these galaxies created from Spitzer and Herschel observations.  © Maud Galametz 

What radio emission tells us about star formation in distant spiral galaxies

A team of astronomers led by Fatemeh Tabatabaei from the Instituto de Astrofisica de Canarias (IAC), including scientists from two Max Planck institutes (MPIfR, Bonn and MPIA, Heidelberg), has measured the radio emission for a large sample of galaxies with the Effelsberg 100-m radio telescope at different wavelengths. These galaxies were selected from the KINGFISH sample previously observed in the infrared with the Herschel satellite. This allows for the first time a comparative study of a total of 52 spiral galaxies. A reliable method could be established to determine the star formation rate exclusively from radio data without including other spectral regimes.

Almost all the light we see in the universe comes from stars which form inside dense clouds of gas in the interstellar medium of galaxies. The rate at which they form (referred to as star formation rate) depends on the reserves of gas and its physical properties like density, temperature, and magnetic field strength. To understand how star formation works, measuring the star formation rate is a key task.

In order to derive the star formation rates, a variety of observations at different wavelengths had been undertaken until now, each with its advantages and disadvantages. The tracers used in the visible and the ultraviolet can be partly absorbed by interstellar dust. This led to the use of hybrid tracers, which combine two or more different wavelength ranges, among them the infrared, which can help to correct for the dust absorption. However, other emissions which are not related to the formation of massive stars can intervene and lead to confusion.

Now, an international research team made a detailed analysis of the spectral energy distribution of a subsample of the KINGFISH galaxies (Fig. 1). The scientists determined for the first time the emitted radio energy which can be used as a tracer to calculate their star formation rates. “We have used the radio emission at intermediate frequencies between 1 and 10 GHz because a tight correlation between the radio and the infrared emission was detected in previous studies, covering a total range of more than four orders of magnitude,” says Fatemeh Tabatabaei from the IAC (La Laguna, Tenerife), the leading author of the study.  In order to improve this relation, more precise studies were needed to understand the energy sources and how radio emission from galaxies is produced.

Spiral Galaxy NGC 4725. Contour lines of radio continuum emission at a frequency of 8.5 GHz, observed with the Effelsberg 100-m radio telescope, overlayed onto an optical image of the galaxy. ©Ancor Damas-Segovia (radio map & combined image), Martin Pugh/martinpughastrophotography.id.au (optical image)


“We decided within the research group to make studies of galaxies from the KINGFISH sample at a series of radio wavelengths”, recalls Eva Schinnerer from the Max-Planck-Institut für Astronomie (MPIA) in Heidelberg, Germany. The final sample consists of 52 galaxies with very diverse properties. “As a single dish, the 100-m Effelsberg telescope with its high sensitivity is the ideal instrument to receive reliable radio fluxes of weak extended objects like galaxies”, explains Marita Krause from the Max-Planck-Institut für Radioastronomie (MPIfR) in Bonn, Germany, who was in charge of the radio observations of those galaxies with the Effelsberg radio telescope. “We named it the KINGFISHER project, meaning KINGFISH galaxies Emitting in Radio.” Fig. 2 shows the radio emission of one galaxy from the sample (NGC 4725).

The results of this project, published today in The Astrophysical Journal, show that the radio emission over the frequency range used is an ideal tracer for calculating the star formation rate, for several reasons. Firstly, the interstellar dust does not attenuate or absorb radiation at this wavelength; secondly, it is emitted by massive stars during several phases of their formation, from young stellar objects to HII regions (zones of ionized gas) and supernova remnants, and finally, there is no need to combine it with any other tracer. For these reasons, measurements in the chosen range are a more rigorous way to measure the formation rate of massive stars than the tracers traditionally used.
“Now we can apply this method to many more galaxies, using the Effelsberg 100-m telescope”, concludes Rainer Beck from MPIfR, also a co-author of the study.

The research team comprises F.S. Tabatabaei, E. Schinnerer, M. Krause, G. Dumas, S. Meidt, A. Damas-Segovia, R. Beck, E.J. Murphy, D.D. Mulcahy, B. Groves, A. Bolatto, D. Dale, M. Galametz, K. Sandstrom, M. Boquien, D. Calzetti, R.C. Kennicutt, L.K. Hunt, I. de Looze and E.W. Pellegrini. Co-authors from MPIfR are Marita Krause, Ancor Damas-Segovia and Rainer Beck.

Fatemeh Tabatabaei started to investigate the radio and infrared emission of galaxies as part of her PhD thesis at MPIfR, followed by postdoc positions at MPIfR and MPIA. At present she is a researcher at the Instituto de Astrofisica de Canarias (IAC), La Laguna.

KINGFISH (“Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel”) is a survey of 61 galaxies in the Nearby Universe. KINGFISHER (“KINGFISH galaxies Emitting in Radio”) provides a subsample of these galaxies north of -21 degrees declination. For 17 of these galaxies radio data from the Effelsberg 100-m radio telescope at different frequencies did already exist (see “Atlas of Galaxies” web page), 35 galaxies were newly observed with the Effelsberg telescope. Both data sets with a total of 52 galaxies were used for the present study.



Original Paper

Tuesday, February 21, 2017

The brightest furthest pulsar in the Universe

NGC 5907 X-1: record-breaking pulsar
The record-breaking pulsar, identified as NGC 5907 X-1, is in the spiral galaxy NGC 5907, which is also known as the Knife Edge Galaxy or Splinter Galaxy. The image comprises X-ray emission data (blue/white) from ESA’s XMM-Newton space telescope and NASA’s Chandra X-ray observatory, and optical data from the Sloan Digital Sky Survey (galaxy and foreground stars).

The inset shows the X-ray pulsation of the spinning neutron star, which has a period of 1.13 s, as determined by XMM-Newton’s European Photon Imaging Camera. Copyright: ESA/XMM-Newton; NASA/Chandra and SDSS.   Hi-res JPG


ESA’s XMM-Newton has found a pulsar – the spinning remains of a once-massive star – that is a thousand times brighter than previously thought possible.

The pulsar is also the most distant of its kind ever detected, with its light travelling 50 million light-years before being detected by XMM-Newton.

Pulsars are spinning, magnetised neutron stars that sweep regular pulses of radiation in two symmetrical beams across the cosmos. If suitably aligned with Earth these beams are like a lighthouse beacon appearing to flash on and off as it rotates. They were once massive stars that exploded as a powerful supernova at the end of their natural life, before becoming small and extraordinarily dense stellar corpses.

This X-ray source is the most luminous of its type detected to date: it is 10 times brighter than the previous record holder. In one second it emits the same amount of energy released by our Sun in 3.5 years.

XMM-Newton observed the object several times in the last 13 years, with the discovery a result of a systematic search for pulsars in the data archive – its 1.13 s periodic pulses giving it away.

The signal was also identified in NASA’s Nustar archive data, providing additional information.

“Before, it was believed that only black holes at least 10 times more massive than our Sun feeding off their stellar companions could achieve such extraordinary luminosities, but the rapid and regular pulsations of this source are the fingerprints of neutron stars and clearly distinguish them from black holes,” says Gian Luca Israel, from INAF-Osservatorio Astronomica di Roma, Italy, lead author of the paper describing the result published in Science this week.

The archival data also revealed that the pulsar’s spin rate has changed over time, from 1.43 s per rotation in 2003 to 1.13 s in 2014. The same relative acceleration in Earth’s rotation would shorten a day by five hours in the same time span.

“Only a neutron star is compact enough to keep itself together while rotating so fast,” adds Gian Luca.

Although it is not unusual for the rotation rate of a neutron star to change, the high rate of change in this case is likely linked to the object rapidly consuming mass from a companion.

“This object is really challenging our current understanding of the ‘accretion’ process for high-luminosity stars,” says Gian Luca. “It is 1000 times more luminous than the maximum thought possible for an accreting neutron star, so something else is needed in our models in order to account for the enormous amount of energy released by the object.”

The scientists think there must be a strong, complex magnetic field close to its surface, such that accretion onto the neutron star surface is still possible while still generating the high luminosity.

“The discovery of this very unusual object, by far the most extreme ever discovered in terms of distance, luminosity and rate of increase of its rotation frequency, sets a new record for XMM-Newton, and is changing our ideas of how such objects really ‘work’,” says Norbert Schartel, ESA’s XMM-Newton project scientist.



Notes for Editors

“An accreting pulsar with extreme properties drives an ultraluminous X-ray source in NGC 5907” by G.L. Israel is published in Science.

The discovery was made as a result of the “Exploring the X-ray Transient and variable Sky” (EXTraS) project.


For further information, please contact:

Markus Bauer








ESA Science and Robotic Exploration Communication Officer









Tel: +31 71 565 6799









Mob: +31 61 594 3 954









Email: markus.bauer@esa.int

Gian Luca Israel
INAF, Osservatorio Astronomico di Roma, Italy
Email: gianluca@oa-roma.inaf.it

Norbert Schartel
XMM-Newton project scientist
Email: Norbert.Schartel@esa.int



Monday, February 20, 2017

Las Cumbres Observatory Provides Vital Early Observations of a Supernova

Artist impression of radiation from an exploding star (depicted as squiggly white lines, detail at right) lighting up a relatively dense shell of gas that had been shed by the star in its last days. Credit: Bill Saxton, NRAO/AUI/NSF and Ofer Yaron, WIS. 


The supernova SN 2013fs was discovered, in a galaxy about 160 million light-years from Earth, on 6 October 2013 by scientists at the Palomar Observatory. Las Cumbres Observatory provided early follow-up observations and obtained one of the first light spectra of the event. Data from LCO followed the luminosity of the supernova from the first hours through months after the explosion.

LCO scientists Andy Howell and Iair Arcavi were part of a team of researchers that used this vital early data to discover previously-unknown characteristics of the massive stars which explode as the most common type of supernova. Their work was published this week in an article in Nature Physics. The full article is available here

A multi-observatory campaign, including Las Cumbres Observatory, provided the earliest spectra that showed signatures of mass lost by the star just before it exploded. The later observations established the type of supernova as one of the most common. Together these two pieces of evidence told scientists that even the most common supernova star progenitors can have episodes where they lose a great quantity of mass just before they explode. Dr. Arcavi summarized this discovery by saying that “we have witnessed an exploding star that illuminated and then destroyed its own wind”. He went on to describe the significance, “This tells us that most massive stars signal their impending doom through violent mass ejections.  We still don’t fully understand how they do it, but this is one way we might be able to predict supernovae before they happen”.

This important discovery has received coverage in the press and you can follow the story in these articles:

Science Mag.: http://www.sciencemag.org/news/2017/02/exploding-star-yields-its-secrets

Space.com: http://www.space.com/35689-supernova-baby-discovery-star-explosions.html

Astronomy.com: http://astronomy.com/news/2017/02/supernova-big-boom



Author: Sandy Seale
(Director of Development)



Saturday, February 18, 2017

Astronomers Propose a Cell Phone Search for Galactic Fast Radio Bursts

Artist impression of a Fast Radio Burst (FRB) reaching Earth. The colors represent the burst arriving at different radio wavelengths, with long wavelengths (red) arriving several seconds after short wavelengths (blue). This delay is called dispersion and occurs when radio waves travel through cosmic plasma. Credit: Jingchuan Yu, Beijing Planetarium / NRAO.  Low Resolution (jpg)


The other known FRBs seem to also come from distant galaxies, but there is no obvious reason that, every once in a while, an FRB wouldn't occur in our own Milky Way galaxy too. If it did, astronomers suggest that it would be "loud" enough that a global network of cell phones or small radio receivers could "hear" it.

"The search for nearby fast radio bursts offers an opportunity for citizen scientists to help astronomers find and study one of the newest species in the galactic zoo," says theorist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics (CfA).

Previous FRBs were detected at radio frequencies that match those used by cell phones, Wi-Fi, and similar devices. Consumers could potentially download a free smartphone app that would run in the background, monitoring appropriate frequencies and sending the data to a central processing facility.

"An FRB in the Milky Way, essentially in our own back yard, would wash over the entire planet at once. If thousands of cell phones picked up a radio blip at nearly the same time, that would be a good sign that we've found a real event," explains lead author Dan Maoz of Tel Aviv University.

Finding a Milky Way FRB might require some patience. Based on the few, more distant ones, that have been spotted so far, Maoz and Loeb estimate that a new one might pop off in the Milky Way once every 30 to 1,500 years. However, given that some FRBs are known to burst repeatedly, perhaps for decades or even centuries, there might be one alive in the Milky Way today. If so, success could become a yearly or even weekly event.

A dedicated network of specialized detectors could be even more helpful in the search for a nearby FRB. For as little as $10 each, off-the-shelf devices that plug into the USB port of a laptop or desktop computer can be purchased. If thousands of such detectors were deployed around the world, especially in areas relatively free from Earthly radio interference, then finding a close FRB might just be a matter of time.

This work has been accepted for publication in the Monthly Notices of the Royal Astronomical Society and is available online.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.


For more information, contact:

Christine Pulliam
Media Relations Manager
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu



Friday, February 17, 2017

Sidekick or star of the show?

Credit: ESA/Hubble & NASA


This image was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), a highly efficient wide-field camera covering the optical and near-infrared parts of the spectrum. While this lovely image contains hundreds of distant stars and galaxies, one vital thing is missing — the object Hubble was actually studying at the time! 

This is not because the target has disappeared. The ACS actually uses two detectors: the first captures the object being studied — in this case an open star cluster known as NGC 299 — while the other detector images the patch of space just ‘beneath’ it. This is what can be seen here.

Technically, this picture is merely a sidekick of the actual object of interest — but space is bursting with activity, and this field of bright celestial bodies offers plenty of interest on its own. It may initially seem to show just stars, but a closer look reveals many of these tiny objects to be galaxies. The spiral galaxies have arms curving out from a bright centre. The fuzzier, less clearly shaped galaxies might be ellipticals. Some of these galaxies contain millions and millions of stars, but are so distant that all of their starry residents are contained within just a small pinprick of light that appears to be the  same size as a single star!

The bright blue dots are very hot stars, sometimes distorted into crosses by the struts supporting Hubble’s secondary mirror. The redder dots are cooler stars, possibly in the red giant phase when a dying star cools and expands.