ALMA’s Most Detailed Image of a Protoplanetary Disc

PR Image eso1611a

ALMA image of the disc around the young star TW Hydrae

PR Image eso1611b

ALMA image of the planet-forming disc around the young, Sun-like star TW Hydrae

PR Image eso1611c

Inner region of the TW Hydrae protoplanetary disc as imaged by ALMA

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PR Video eso1611a

ALMA image of the disc around the young star TW Hydrae

Evidence for planet formation in Earth-like orbit around young star

This new image from the Atacama Large Millimeter/submillimeter Array (ALMA) shows the finest detail ever seen in the planet-forming disc around the nearby Sun-like star TW Hydrae. It reveals a tantalising gap at the same distance from the star as the Earth is from the Sun, which may mean that an infant version of our home planet, or possibly a more massive super-Earth, is beginning to form there.

The star TW Hydrae is a popular target of study for astronomers because of its proximity to Earth (only about 175 light-years away) and its status as an infant star (about 10 million years old). It also has a face-on orientation as seen from Earth. This gives astronomers a rare, undistorted view of the complete protoplanetary disc around the star.

"Previous studies with optical and radio telescopes confirm that TW Hydrae hosts a prominent disc with features that strongly suggest planets are beginning to coalesce," said Sean Andrews with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, USA and lead author on a paper published today in the Astrophysical Journal Letters. "The new ALMA images show the disc in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that may indicate that a planet with an Earth-like orbit is forming there."

Other pronounced gaps that show up in the new images are located three billion and six billion kilometres from the central star, similar to the average distances from the Sun to Uranus and Pluto in the Solar System. 

They too are likely to be the results of particles that came together to form planets, which then swept their orbits clear of dust and gas and shepherded the remaining material into well-defined bands.

For the new TW Hydrae observations, astronomers imaged the faint radio emission from millimetre-sized dust grains in the disc, revealing details on the order of the distance between the Earth and the Sun (about 150 million kilometres). These detailed observations were made possible with ALMA’s high-resolution, long-baseline configuration. When ALMA's dishes are at their maximum separation, up to 15 kilometres apart, the telescope is able to resolve finer details. "This is the highest spatial resolution image ever of a protoplanetary disc from ALMA, and that won't be easily beaten in the future!" said Andrews [1].

"TW Hydrae is quite special. It is the nearest known protoplanetary disc to Earth and it may closely resemble the Solar System when it was only 10 million years old," adds co-author David Wilner, also with the Harvard-Smithsonian Center for Astrophysics.

Earlier ALMA observations of another system, HL Tauri, show that even younger protoplanetary discs — a mere 1 million years old — can display similar signatures of planet formation. By studying the older TW Hydrae disc, astronomers hope to better understand the evolution of our own planet and the prospects for similar systems throughout the Milky Way.

The astronomers now want to find out how common these kinds of features are in discs around other young stars and how they might change with time or environment.

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Notes

[1] The angular resolution of the images of HL Tauri was similar to these new observations, but as TW Hydrae is much closer to Earth, finer details can be seen.

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More Information

This research was presented in a paper "Ringed Substructure and a Gap at 1 AU in the Nearest Protoplanetary Disk", by S.M. Andrews et al., appearing in the Astrophysical Journal Letters.

The team is composed of Sean M. Andrews (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), David J. Wilner (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA) , Zhaohuan Zhu (Princeton University, Princeton, New Jersey, USA), Tilman Birnstiel (Max-Planck-Institut für Astronomie, Heidelberg, Germany), John M. Carpenter (Joint ALMA Observatory, Santiago, Chile), Laura M. Peréz (Max-Planck-Institut für Radioastronomie, Bonn, Germany), Xue-Ning Bai (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), Karin I. Öberg (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), A. Meredith Hughes (Wesleyan University, Van Vleck Observatory, Middletown, USA), Andrea Isella (Rice University, Houston, Texas, USA) and Luca Ricci (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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”.

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Links

• Research paper
• Photos of ALMA
• Other press releases featuring ALMA

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Contacts

Sean M. Andrews
Harvard-Smithsonian Center for Astrophysics
Cambridge, Massachusetts, USA
Email: sandrews@cfa.harvard.edu

Charles Blue
NRAO Public Information Officer
Tel: +1 434 296-0314
Email: cblue@nrao.edu

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: ESO

Merging black holes

Artist's impression of two black holes as they spiral towards each other before merging, releasing gravitational waves – fluctuations in the fabric of spacetime.  Copyright: ESA–C.Carreau

On 14 September, the terrestrial Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves – fluctuations in the fabric of spacetime – produced by a pair of black holes as they spiralled towards each other before merging. The signal lasted less than half a second.

The discovery was the first direct observation of gravitational waves, predicted by Albert Einstein a century ago.

Two days after the detection, the LIGO team alerted a number of ground- and space-based astronomical facilities to look for a possible counterpart to the source of gravitational waves. The nature of the source was unclear at the time, and it was hoped that follow-up observations across the electromagnetic spectrum might provide valuable information about the culprit.

Gravitational waves are released when massive bodies are accelerated, and strong emission should occur when dense stellar remnants such as neutron stars or black holes spiral towards each other before coalescing.

Models predict that the merging of two stellar-mass black holes would not produce light at any wavelength, but if one or two neutron stars were involved in the process, then a characteristic signature should be observable across the electromagnetic spectrum.

Another possible source of gravitational waves would be an asymmetric supernova explosion, also known to emit light over a range of wavelengths.

It was not possible to pinpoint the LIGO source – its position could only be narrowed down to a very long strip across the sky.

Observatories searched their archives in case data had been serendipitously collected anywhere along this strip around the time of the gravitational wave detection. They were also asked to point their telescopes to the same region in search for any possible 'afterglow' emission.

INTEGRAL is sensitive to transient sources of high-energy emission over the whole sky, and thus a team of scientists searched through its data, seeking signs of a sudden burst of hard X-rays or gamma rays that might have been recorded at the same time as the gravitational waves were detected.

"We searched through all the available INTEGRAL data, but did not find any indication of high-energy emission associated with the LIGO detection," says Volodymyr Savchenko of the François Arago Centre in Paris, France. Volodymyr is the lead author of a paper reporting the results, published today in Astrophysical Journal Letters.

The team analysed data from the Anti-Coincidence Shield on INTEGRAL's SPI instrument. The shield helps to screen out radiation and particles coming from directions other than that where the instrument is pointing, as well as to detect transient high-energy sources across the whole sky.

The team also looked at data from INTEGRAL's IBIS instrument, although at the time it was not pointing at the strip where the source of gravitational waves was thought to be located.

"The source detected by LIGO released a huge amount of energy in gravitational waves, and the limits set by the INTEGRAL data on a possible simultaneous emission of gamma rays are one million times lower than that," says co-author Carlo Ferrigno from the INTEGRAL Science Data Centre at the University of Geneva, Switzerland.

Subsequent analysis of the LIGO data has shown that the gravitational waves were produced by a pair of coalescing black holes, each with a mass roughly 30 times that of our Sun, located about 1.3 billion light years away. Scientists do not expect to see any significant emission of light at any wavelength from such events, and thus INTEGRAL's null detection is consistent with this scenario.

Similarly, nothing was seen by the great majority of the other astronomical facilities making observations from radio and infrared to optical and X-ray wavelengths.

The only exception was the Gamma-Ray Burst Monitor on NASA's Fermi Gamma-Ray Space Telescope, which observed what appears to be a sudden burst of gamma rays about 0.4 seconds after the gravitational waves were detected. The burst lasted about one second and came from a region of the sky that overlaps with the strip identified by LIGO.

This detection sparked a bounty of theoretical investigations, proposing possible scenarios in which two merging black holes of stellar mass could indeed have released gamma rays along with the gravitational waves.

However, if this gamma-ray flare had had a cosmic origin, either linked to the LIGO gravitational wave source or to any other astrophysical phenomenon in the Universe, it should have been detected by INTEGRAL as well.

The absence of any such detection by both instruments on INTEGRAL suggests that the measurement from Fermi could be unrelated to the gravitational wave detection.

"This result highlights the importance of synergies between scientists and observing facilities worldwide in the quest for as many cosmic messengers as possible, from the recently-detected gravitational waves to particles and light across the spectrum," says Erik Kuulkers, INTEGRAL Project Scientist at ESA.

This will become even more important when it becomes possible to observe gravitational waves from space.

This has been identified as the goal for the L3 mission in ESA's Cosmic Vision programme, and the technology for building it is currently being tested in space by ESA's LISA Pathfinder mission.

Such an observatory will be capable of detecting gravitational waves from the merging of supermassive black holes in the centres of galaxies for months prior to the final coalescence, making it possible to locate the source much more accurately and thus provide astronomical observatories with a place and a time to look out for associated electromagnetic emission.

"We are looking forward to further collaborations and discoveries in the newly-inaugurated era of gravitational astronomy," concludes Erik.

Notes for Editors

"INTEGRAL Upper Limits On Gamma-Ray Emission Associated With The Gravitational Wave Event GW150914," by V. Savchenko et al. is published in Astrophysical Journal Letters.

For further information, please contact:


Markus Bauer
ESA Science Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.baueresa.int

Volodymyr Savchenko
François Arago Center
APC - Astroparticule et Cosmologie
Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire De Paris, Sorbonne Paris Cité
Paris, France
Email: savchenkapc.in2p3.fr

Carlo Ferrigno
INTEGRAL Science Data Centre
University of Geneva, Switzerland
Email: Carlo.Ferrignounige.ch

Erik Kuulkers
ESA INTEGRAL Project Scientist
Email: Erik.Kuulkersesa.int

Source: ESA/INTEGRAL

G1.9+0.3: Trigger for Milky Way's Youngest Supernova Identified

G1.9+0.3

Credit: X-ray (NASA/CXC/CfA/S.Chakraborti et al.) 

 JPEG (321 kb) - Large JPEG (2.3 MB) - Tiff (6.8 MB)

Scientists have used data from NASA's Chandra X-ray Observatory and the NSF's Jansky Very Large Array to determine the likely trigger for the most recent supernova in the Milky Way, as described in our latest press release.

Astronomers had previously identified G1.9+0.3 as the remnant of the most recent supernova in our Galaxy. It is estimated to have occurred about 110 years ago from the vantage point of Earth, in a dusty region of the Galaxy that blocked visible light from reaching Earth. This Chandra image shows G1.9+0.3 where low-energy X-rays are colored red, medium-energy X-rays are green, and a higher-energy band of X-rays is blue.

G1.9+0.3 belongs to the Type Ia category, an important class of supernovas exhibiting reliable patterns in their brightness that make them valuable tools for measuring the rate at which the universe is expanding. Most scientists agree that Type Ia supernovas occur when white dwarfs, the dense remnants of Sun-like stars that have run out of fuel, explode. However, there has been a debate over what triggers these white dwarf explosions. Two primary ideas are the accumulation of material onto a white dwarf from a companion star or the violent merger of two white dwarfs.

The researchers in this latest study applied a new technique that could have implications for understanding other Type Ia supernovas. They used archival Chandra and VLA data to examine how the expanding supernova remnant G1.9+0.3 interacts with the gas and dust surrounding the explosion. The resulting radio and X-ray emission provide clues as to the cause of the explosion. In particular, an increase in X-ray and radio brightness of the supernova remnant with time is expected only if a white dwarf merger took place, according to theoretical work.

This result implies that Type Ia supernovas are either all caused by white dwarf collisions, or are caused by a mixture of white dwarf collisions and the mechanism where the white dwarf pulls material from a companion star. It is important to identify the trigger mechanism for Type Ia supernovas because if there is more than one cause then the contribution from each can change over time, affecting their use as "standard candles" in cosmology.

A paper describing these results appeared in the March 1st, 2016 issue of The Astrophysical Journal and is available online. The authors on the paper are Sayan Chakraborti, Francesca Childs, and Alicia Soderberg (Harvard). 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.

Fast Facts for G1.9+0.3:

Scale: Image is about 4.1 arcmin across (About 30 light years)
Category: Supernovas & Supernova Remnants
Coordinates (J2000): RA 17h 48m 45s | Dec -27° 10' 00"
Constellation: Sagittarius
Observation Date: 15 pointings between Feb 2007 and Jul 2011
Observation Time: 362 hours. (15 days 2 hours)
Obs. ID: 6708, 8521, 10111, 10112, 10928, 10930, 12689, 12690, 12691, 12692, 12693, 12694, 12695, 13407, 13509
Instrument: ACIS
References: Chakraborti, S. et al, 2016, ApJ, 819, 37; arXiv:1510.08851
Color Code: X-ray (Red, Green, Blue)
Distance Estimate: About 27,700 light years

Source: NASA’s Chandra X-ray Observatory

To the center of the brightest quasar

Artistic view of a quasar; a super-massive black hole in the center is being fed by a disk of gas and dust, producing collimated jets of ejected material moving at nearly the speed of light. © Wolfgang Steffen, Institute for Astronomy, UNAM, Mexico 

Artistic view of the 10-meter space radio telescope on board of the Russian satellite Spektr-R comprising the space-borne component of the RadioAstron mission.© Astro Space Center of Lebedev Physical Institute

RadioAstron observations of the extremely hot heart of quasar 3C 273

The space mission RadioAstron employing a 10-meter radio telescope on board of the Russian satellite Spektr-R has revealed the first look at the finest structure of the radio emitting regions in the quasar 3C 273 at wavelengths of 18, 6, and 1.3 cm. These ground breaking observations have been made by an international research team with four of the largest radio telescopes on Earth, including the Effelsberg 100-meter antenna. They provide an unprecedented sensitivity to radio emission at angular scales as small as 26 microarcseconds. This resolution was achieved by combining signals recorded at all antennas and effectively creating a telescope of almost 8 Earth’s diameters in size.

The results are published in the current issue of the "The Astrophysical Journal".

Supermassive black holes, containing millions to billions times the mass of our Sun, reside at the centers of all massive galaxies. These black holes can drive powerful jets that emit prodigiously, often outshining all the stars in their host galaxies. But there is a limit to how bright these jets can be – when electrons get hotter than about 100 billion degrees, they interact with their own emission to produce X-rays and Gamma-rays and quickly cool down.

Astronomers have just reported a startling violation of this long-standing theoretical limit in the quasar 3C 273. "We measure the effective temperature of the quasar core to be hotter than 10 trillion degrees!" comments Yuri Kovalev (Astro Space Center, Lebedev Physical Institute, Moscow, Russia), the RadioAstron project scientist. “This result is very challenging to explain with our current understanding of how relativistic jets of quasars radiate."

To obtain these results, the international team used the Earth-to-Space Interferometer RadioAstron. The interferometer consists of an orbiting radio telescope working together with the largest ground telescopes:  the 100-meter Effelsberg Telescope, the 110-m Green Bank Telescope, the 300-m Arecibo Observatory, and the Very Large Array. Operating together, these observatories provide the highest direct resolution ever achieved in astronomy, thousands of times finer than the Hubble Space Telescope.

“The fact  that RadioAstron has measured extreme brightness temperatures already in several objects, including the recently reported observations of BL Lacertae, these measurements indeed point out to new underlying physics behind the energetic sources of radiation in quasars”, states Andrei Lobanov, the coordinator of RadioAstron activities at the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany.

However, the incredibly high temperatures were not the only surprise the RadioAstron team has found in 3C 273. The team also discovered an effect never seen before in an extragalactic source: the image of 3C 273 has substructure caused by the effects of peering through the dilute interstellar material of the Milky Way.

"Just as the flame of a candle distorts an image viewed through the hot turbulent air above it, the turbulent plasma of our own galaxy distorts images of distant astrophysical sources, such as quasars," explains Michael Johnson of the Harvard-Smithsonian Center for Astrophysics (CfA), who led the scattering study. He continues: "These objects are so compact that we had never been able to see this distortion before. The amazing angular resolution of RadioAstron gives us a new tool to understand the extreme physics near the central supermassive black holes of distant galaxies and the diffuse plasma pervading our own galaxy."

“Our research team has been working for a long time on extending the VLBI technique to space antennas reaching baselines much larger than our Earth”, concludes Anton Zensus, director at the MPIfR and head of its Radio Astronomy/VLBI research department.  “The new discoveries on 3C 273 are a wonderful example for our successful cooperation within the RadioAstron project.”

Source: Max Planck Institute for Radio Astronomy

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Local Contact:

Dr. Andrei Lobanov

Phone:+49 228 525-191

Email: alobanov@mpifr-bonn.mpg.de

Max-Planck-Institut für Radioastronomie, Bonn

Prof. Dr. J. Anton Zensus

Director and Head of "Radio Astronomy/VLBI" Research Dept.

Phone:+49 228 525-298 (secretary)

Email: azensus@mpifr-bonn.mpg.de

Max-Planck-Institut für Radioastronomie, Bonn

Dr. Norbert Junkes

Press and Public Outreach

Phone:+49 228 525-399

Email: njunkes@mpifr-bonn.mpg.de

Max-Planck-Institut für Radioastronomie, Bonn

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Original papers

RadioAstron Observations of the Quasar 3C273: A Challenge to the Brightness Temperature Limit

Y. Y. Kovalev, N. S. Kardashev, K. I. Kellermann, A. P. Lobanov, M. D. Johnson, L. I. Gurvits, P. A. Voitsik, J. A. Zensus, J. M. Anderson, U. Bach, D. L. Jauncey, F. Ghigo, T. Ghosh, A. Kraus, Yu. A. Kovalev, M. M. Lisakov, L. Yu. Petrov, J. D. Romney, C. J. Salter, and K. V. Sokolovsky, The Astrophysical Journal Letters, Volume 820, Issue 1, article id. L9, 6 pp. (2016).

Extreme Brightness Temperatures and Refractive Substructure in 3C273 with RadioAstron

Johnson, Michael D.; Kovalev, Yuri Y.; Gwinn, Carl R.; Gurvits, Leonid I.; Narayan, Ramesh; Macquart, Jean-Pierre; Jauncey, David L.; Voitsik, Peter A.; Anderson, James M.; Sokolovsky, Kirill V.; Lisakov, Mikhail M., The Astrophysical Journal Letters, Volume 820, Issue 1, article id. L10, 6 pp. (2016).

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The RadioAstron project is led by the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences and the Lavochkin Scientific and Production Association under a contract with the Russian Federal Space Agency, in collaboration with partner organizations in Russia and other countries.

The Spektr-R antenna of RadioAstron is at an elliptical orbit around Earth reaching a maximum apogee distance of 350,000 km which would result in a virtual radio telescope of up to 27 times the Earth’s diameter.

This research is partly based on observations with the 100 m telescope of the MPIfR at Effelsberg.

MPIfR scientists involved in the project are Andrei Lobanov, J. Anton Zensus, James Anderson, Uwe Bach and Alex Kraus. Yuri Kovalev is affiliated as guest scientist with the MPIfR.

3C 273 is a quasar (active galactic nucleus) in the direction to the constellation Virgo. With a magnitude of 12.9 it is the optically brightest quasar in the sky, its redshift of 0.158 corresponding to a distance of approximately 2.4 billion light years.

The quasar 3C 273 is one of the target stations of the “Galaxy walk” at the Effelsberg Radio Observatory. Scaled 1:5x10²², the Galaxy Walk runs from Milky Way and Andromeda Galaxy (50 cm apart) to the edge of the Universe. 3C 273 forms station no. 7. With a distance of  2,4 billion light years it shows up only 450 meters away from the start (at a total length of 2.6 km for the Galaxy walk) .

Herschel reveals a ribbon of future stars

Herschel reveals a ribbon of future stars
Copyright: ESA/Herschel/SPIRE/M. Juvela (U. Helsinki, Finland)

Star formation is taking place all around us. The Milky Way is laced with clouds of dust and gas that could become the nursery of the next generation of stars. Thanks to ESA’s Herschel space observatory, we can now look inside these clouds and see what is truly going on.

It may seem ironic but when searching for sites of future star formation, astronomers look for the coldest spots in the Milky Way. This is because before the stars ignite the gas that will form their bulk must collapse together. To do that, it has to be cold and sluggish, so that it cannot resist gravity.

As well as gas, there is also dust. This too is extremely cold, perhaps just 10–20 degrees above absolute zero. To optical telescopes it appears completely dark, but the dust reveals itselfat far-infrared wavelengths.

One of the surprises is that the coldest parts of the cloud form filaments that stretch across the warmer parts of the cloud. This image shows a cold cloud filament, known to astronomers as G82.65-2.00. The blue filament is the coldest part of the cloud and contains 800 times as much mass as the Sun. The dust in this filament has a temperature of –259ºC. At this low temperature, if the filament contains enough mass it is likely that this section will collapse into stars.

This image is colour-coded so that the longest infrared wavelength, corresponding to the coldest region, is shown in blue, and the shortest wavelength, corresponding to slightly warmer dust, is shown in red.

The field of view on display here is a little more than two times the width of the full Moon. It is one of 116 regions of space observed by Herschel as part of the Galactic Cold Cores project. Each field was chosen because ESA’s cosmic microwave background mapper, Planck, showed that these regions of the galaxy possessed extremely cold dust.

Source: ESA/Space Images

Investigating the Mystery of Migrating 'Hot Jupiters'

The turbulent atmosphere of a hot, gaseous planet known as HD 80606b is shown in this simulation based on data from NASA's Spitzer Space Telescope

Image credit: NASA/JPL-Caltec. › Full image and caption

Astronomers watched an exoplanet called HD 80606b heat up and cool off during its sizzling-hot orbit around its star

Image credit: NASA/JPL-Caltech/MIT.  › Full image and caption

The Wild Temperature Swings of an Exoplanet
Youtube video

The last decade has seen a bonanza of exoplanet discoveries. Nearly 2,000 exoplanets -- planets outside our solar system -- have been confirmed so far, and more than 5,000 candidate exoplanets have been identified. Many of these exotic worlds belong to a class known as "hot Jupiters." These are gas giants like Jupiter but much hotter, with orbits that take them feverishly close to their stars. 

At first, hot Jupiters were considered oddballs, since we don't have anything like them in our own solar system. But as more were found, in addition to many other smaller planets that orbit very closely to their stars, our solar system started to seem like the real misfit.

"We thought our solar system was normal, but that's not so much the case," said astronomer Greg Laughlin of the University of California, Santa Cruz, co-author of a new study from NASA's Spitzer Space Telescope that investigates hot Jupiter formation. 

As common as hot Jupiters are now known to be, they are still shrouded in mystery. How did these massive orbs form, and how did they wind up so shockingly close to their stars? 

The Spitzer telescope found new clues by observing a hot Jupiter known as HD 80606b, situated 190 light-years from Earth. This planet is unusual in that it has a wildly eccentric orbit almost like that of a comet, swinging very close to its star and then back out to much greater distances over and over again every 111 days. One side of the planet is thought to become dramatically hotter than the other during its harrowing close approaches. In fact, when the planet is closest to its host star, the side facing the star quickly heats up to more than 2,000 degrees Fahrenheit (1,100 degrees Celsius). 

"As the planet gets closer to the star, it feels a burst of starlight, or radiation. The atmosphere becomes a cauldron of chemical reactions, and the winds ramp up far beyond hurricane force," said Laughlin, a co-author on the Spitzer study, which is accepted for publication in The Astrophysical Journal. 

HD 80606b is thought to be in the process of migrating from a more distant orbit to a much tighter one typical of hot Jupiters. One of the leading theories of hot-Jupiter formation holds that gas giants in distant orbits become hot Jupiters when the gravitational influences from nearby stars or planets drive them into closer orbits. The planets start out in eccentric orbits, then, over a period of hundreds of millions of years, are thought to gradually settle down into tight, circular orbits.

"This planet is thought to be caught in the act of migrating inward," said Julien de Wit of the Massachusetts Institute of Technology, Cambridge, lead author of the new study. "By studying it, we are able to test theories of hot Jupiter formation."

Spitzer previously studied HD 80606b in 2009. The latest observations are more detailed, thanks to a longer observing time -- 85 hours -- and improvements in Spitzer's sensitivity to exoplanets. 

"The Spitzer data are pristine," said de Wit. "And we were able to observe the planet for much longer this time, giving us more insight into its coldest temperature and how fast it heats up, cools down and rotates."

A key question addressed in the new study is: How long is HD 80606b taking to migrate from an eccentric to a circular orbit? One way to assess this is to look at how "squishy" the planet is. When HD 80606b whips closely by its star, the gravity of the star squeezes it. If the planet is squishier, or more pliable, it can better dissipate this gravitational energy as heat. And the more heat that is dissipated, the faster the planet will transition to a circular orbit, a process known as circularization.

"If you take a Nerf ball and squeeze it a bunch of times really fast, you'll see that it heats up," said Laughlin. "That's because the Nerf ball is good at transferring that mechanical energy into heat. It's squishy as a result."

The Spitzer results show that HD 80606b does not dissipate much heat when it is squeezed by gravity during its close encounters - and thus is not squishy, but rather stiffer as a whole. This suggests the planet is not circularizing its orbit as fast as expected, and may take another 10 billion years or more to complete.

"We are starting to learn how long it may take for hot Jupiter migration to occur," said de Wit. "Our theories said it shouldn't take that long because we don't see migrating hot Jupiters very often."

"The long time scales we are observing here suggest that a leading migration mechanism may not be as efficient for hot Jupiter formation as once believed," said Laughlin. 

The Spitzer study suggests that competing theories for hot Jupiter formation -- in which gas giants form "in situ," or close to their stars, or smoothly spiral inward with the help of planet-forming disks -- may be preferred.

The new study is also the first to measure the rotation rate of an exoplanet orbiting a sun-like star. Spitzer observed changes in the planet's brightness as the planet spun on its axis, finding a rotation period of 90 hours. 

"Fifty years ago, we were measuring the rotation rates of planets in our own solar system for the first time. Now we are doing the same thing for planets orbiting other stars. That's pretty amazing," said Laughlin.

A rotation rate of 90 hours is much slower than what is predicted for HD 80606b, puzzling astronomers, and adding to the enduring mystique of hot Jupiters.

Additional study authors are: Nikole Lewis of the Space Telescope Science Institute in Baltimore; Jonathan Langton of Principia College, Elsah, Illinois; Drake Deming of University of Maryland, College Park; Konstantin Batygin of the California Institute of Technology, Pasadena; and Jonathan Fortney of the University of California, Santa Cruz.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. 

For more information about Spitzer, visit:  http://spitzer.caltech.edu / http://www.nasa.gov/spitzer

Technical journal article:  http://iopscience.iop.org/article/10.3847/2041-8205/820/2/L33


Media Contact

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
818-354-4673
whitney.clavin@jpl.nasa.gov

Source:  JPL-Caltech/news

Magnetar could have boosted explosion of extremely bright supernova

Image 1: Artist impression of a magnetar boosting a super-luminous supernova and gamma-ray burst

Credit: Kavli IPMU

Image 2: The yellow-orange host galaxy (left) before the supernova, and afterwards (right) when the ASASSN-15lh supernova’s blue light outshines its host galaxy (Credit: The Dark Energy Survey / B. Shappee / ASAS-SN team)

Image 3: Light curves of ASASSN-15lh and SN 2011kl compared with normal supernovae SN 1999em and SN 1987A. 

Credit: Bersten et al.

Calculations by scientists have found highly magnetized, rapidly spinning neutron stars called magnetars could explain the energy source behind two extremely unusual stellar explosions.

Stellar explosions known as supernovae usually shine a billion times brighter than the Sun. Super-luminous supernovae (SLSNe) are a relatively new and rare class of stellar explosions, 10 to 100 times brighter than normal supernovae. But the energy source of their super-luminosity, and explosion mechanisms are a mystery and remain controversial amongst scientists.

A group of researchers led by Melina Bersten, an Instituto de Astrofisica de La Plata Researcher and affiliate member of Kavli IPMU, and including Kavli IPMU Principal Investigator Ken'ichi Nomoto, tested a model that suggests that the energy to power the luminosity of two recently discovered SLSNe, SN 2011kl and ASASSN-15lh, is mainly due to the rotational energy lost by a newly born magnetar. They analyzed two recently discovered super-luminous supernovae: SN 2011kl and ASASSN-15lh.

“These supernovae can be found in very distant universe, thus possibly informing us the properties of the first stars of the universe,” said Nomoto.

Interestingly, both explosions were found to be extreme cases of SLSNe. First, SN 2011kl was discovered in 2011 and is the first supernovae to have an ultra long gamma-ray burst that lasted several hours, whereas typical long-duration gamma-ray bursts fade in a matter of minutes. The second, ASASSN-15lh, was discovered in 2015 and is possibly the most luminous and powerful explosion ever seen, more than 500 times brighter than normal supernovae. For more than a month its luminosity was 20 times brighter than the whole Milky Way galaxy.

The team performed numerical hydrodynamical calculations to explore the magnetar hypothesis, and found both SLSNe could be understood in the framework of magnetar-powered supernovae (see image 1). In particular, for ASASSN-15lh, they were able to find a magnetar source with physically allowed properties of magnetic field strength and rotation period. The solution avoided the prohibited realm of neutro-star spins that would cause the object to breakup due to centrifugal forces.

“These two extreme super-luminous supernovae put to the test our knowledge of stellar explosions,” said Bersten.

To confirm the team’s calculations, further observations would need to be carried out when the material ejected by the supernova is expected to become thin. The most powerful telescopes, including the Hubble Space Telescope, will be required for this purpose. If correct, these observations will allow scientists to probe the inner part of an exploding object, and provide new insight on its origin, and evolution of stars in the Universe.

The group’s paper was published in The Astrophysical Journal Letters in January.

Paper details

Journal: Astrophysical Journal Letters
Title: The Unusual Superluminous Supernovae SN2011KL and ASASSN-15LH
Authors: Melina C. Bersten (1,2,3) , Omar G. Benvenuto (1,2,4) , Mariana Orellana (5,6) , and Ken'ichi Nomoto (3,7)

Author affiliations:

1. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo
del Bosque S/N, B1900FWA La Plata, Argentina
2. Instituto de Astrofísica de La Plata (IALP) , CONICET, Argentina
3. Kavli Institute for the Physics and Mathematics of the Universe, The University of
 Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan
4. Member of the Carrera del Investigador Científico de la Comisión de Investigaciones
Científicas de la Provincia de Buenos Aires (CIC), Argentina
5. Sede Andina, Universidad Nacional de Río Negro, Mitre 630 (8400) Bariloche, Argentina
6. Member of the Carrera del Investigador Científico y Tecnológico del CONICET, Argentina
7. Hamamatsu Professor.

DOI: 10.3847/2041-8205/817/1/L8 (Published 20 January, 2016)

Paper abstract (Astrophysical Journal Letters)
Preprint (arXiv.org)

Media contact:
 
Motoko Kakubayashi
Press Officer
Kavli Institute for the Physics and Mathematics of the Universe
The University of Tokyo Institutes for Advanced Study,
The University of Tokyo
TEL: +81-04-7136-5980
E-mail: press@ipmu.jp


Research contact:
 
Ken'ichi Nomoto
Principal Investigator and Project Professor Kavli Institute for the Physics and Mathematics of the Universe
TEL: +81-04-7136-6567
E-mail: nomoto@astron.s.u-tokyo.ac.jp


Melina C. Bersten
Researcher
Instituto de Astrofisica de La Plata
Affiliate member
Kavli Institute for the Physics and Mathematics of the Universe
E-mail: merlinada.bersten@gmail.com


Useful links

All images can be downloaded from this page: http://web.ipmu.jp/press/201603-Magnetar

Source: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)

All Quiet in the Nursery?

LDN 1768

Credit: ESO

The dark patch snaking across this spectacular image of a field of stars in the constellation of Ophiuchus (The Serpent-bearer) is not quite what it appears to be.

Although it looks as if there are no stars here, they are hidden behind this dense cloud of dust that blocks out their light. This particular dark cloud is known as LDN 1768.

Despite their rather dull appearance, dark nebulae like LDN 1768 are of huge interest to astronomers, as it is here that new stars form. Inside these vast stellar nurseries there are protostars — stars at the earliest stage of their lives, still coalescing out of the gas and dust in the cloud.

Protostars are relatively cold and have not yet begun to produce enough energy to emit visible light. Instead, they emit radiation at submillimetre wavelengths, which human eyes cannot see. Luckily, unlike visible light, light at submillimetre wavelengths is not absorbed by the surrounding dust. By using special telescopes that are sensitive to submillimetre radiation, like the Atacama Large Millimeter/submillimeter Array (ALMA) observatory, we can see through the dust and find out more about the protostars within the cloud.

Eventually, the protostars will become dense and hot enough to start the nuclear reactions that will produce visible light and they will start to shine. When this happens, they will blow away the cocoon of dust surrounding them and cause any remaining gas to emit light as well, creating the spectacular light show known as an HII region.

Source: ESO/Images

A cosmic kaleidoscope

MACS J0416.1-2403

Credit: NASA, ESA, CXC, NRAO/AUI/NSF, STScI, and G. Ogrean (Stanford University)

Acknowledgment: NASA, ESA, and J. Lotz (STScI), and the HFF team

At first glance, this cosmic kaleidoscope of purple, blue and pink offers a strikingly beautiful — and serene — snapshot of the cosmos. However, this multi-coloured haze actually marks the site of two colliding galaxy clusters, forming a single object known as MACS J0416.1-2403 (or MACS J0416 for short).

MACS J0416 is located about 4.3 billion light-years from Earth, in the constellation of Eridanus. This new image of the cluster combines data from three different telescopes: the NASA/ESA Hubble Space Telescope (showing the galaxies and stars), the NASA Chandra X-ray Observatory (diffuse emission in blue), and the NRAO Jansky Very Large Array (diffuse emission in pink). Each telescope shows a different element of the cluster, allowing astronomers to study MACS J0416 in detail.

As with all galaxy clusters, MACS J0416 contains a significant amount of dark matter, which leaves a detectable imprint in visible light by distorting the images of background galaxies. In this image, this dark matter appears to align well with the blue-hued hot gas, suggesting that the two clusters have not yet collided; if the clusters had already smashed into one another, the dark matter and gas would have separated. MACS J0416 also contains other features — such as a compact core of hot gas — that would likely have been disrupted had a collision already occurred.

Together with five other galaxy clusters, MACS J0416 is playing a leading role in the Hubble Frontier Fields programme, for which this data was obtained. Owing to its huge mass, the cluster is in fact bending the light of background objects, acting as a magnifying lens. Astronomers can use this phenomenon to find galaxies that existed only hundreds of million years after the big bang.

For more information on both Frontier Fields and the phenomenon of gravitational lensing, see Hubblecast 90: The final frontier.


Links

• Hubblecast 90: The final frontier
• Link to Hubblesite release

 Source: ESA/Hubble - Space Telescope

The Wilds of the Local Group

PR Image eso1610a

The WLM galaxy on the edge of the Local Group 

PR Image eso1610b

The dwarf galaxy WLM in the constellation of Cetus

PR Image eso1610c 

Wide-field view of the sky around the dwarf galaxy WLM

Videos

PR Video eso1610a

Zooming in on the dwarf galaxy WLM

PR Video eso1610b

The WLM galaxy on the edge of the Local Group

This scene, captured by ESO’s OmegaCAM on the VLT Survey Telescope, shows a lonely galaxy known as Wolf-Lundmark-Melotte, or WLM for short. Although considered part of our Local Group of dozens of galaxies, WLM stands alone at the group’s outer edges as one of its most remote members. In fact, the galaxy is so small and secluded that it may never have interacted with any other Local Group galaxy — or perhaps even any other galaxy in the history of the Universe.

Rather like an uncontacted tribe living deep in the Amazon rainforest or on an island in Oceania, WLM offers a rare insight into the primordial nature of galaxies that have been little disturbed by their environment.

WLM was discovered in 1909 by German astronomer Max Wolf, and identified as a galaxy some fifteen years later by astronomers Knut Lundmark and Philibert Jacques Melotte — explaining the galaxy’s unusual moniker. The dim galaxy is located in the constellation of Cetus (The Sea Monster) about three million light-years away from the Milky Way, which is one of the three dominant spiral galaxies in the Local Group.

WLM is quite small and lacks structure, hence its classification as a dwarf irregular galaxy. WLM spans about 8000 light-years at its greatest extent, a measurement that includes a halo of extremely old stars discovered in 1996 (eso9633).

Astronomers think that comparatively small primeval galaxies gravitationally interacted with each other and in many cases merged, building up into larger composite galaxies. Over billions of years, this merging process assembled the large spiral and elliptical galaxies that now appear to be common in the modern Universe. 

Galaxies congregating in this manner is similar to the way in which human populations have shifted over thousands of years and intermixed into larger settlements, eventually giving rise to today’s megacities.

WLM has instead developed on its own, away from the influence of other galaxies and their stellar populations. Accordingly, like a hidden human population with limited contact with outsiders, WLM represents a relatively unperturbed “state of nature”, where any changes occurring over its lifetime have taken place largely independent of activity elsewhere.

This small galaxy features an extended halo of very dim red stars, which stretches out into the inky blackness of the surrounding space. This reddish hue is indicative of advanced stellar age. It is likely that the halo dates back to the original formation of the galaxy itself, helpfully offering clues about the mechanisms that spawned the very first galaxies.

The stars at the centre of WLM, meanwhile, appear younger and bluer in colour. In this image, pinkish clouds highlight areas where the intense light from young stars has ionised ambient hydrogen gas, making it glow in a characteristic shade of red.

This detailed image was captured by the OmegaCAM wide-field imager, a huge camera mounted on ESO’s VLT Survey Telescope (VST) in Chile — a 2.6-metre telescope exclusively designed to survey the night sky in visible light. OmegaCAM’s 32 CCD detectors create 256-megapixel images, offering a very detailed wide-field view of the cosmos.

More Information

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

• Photos of the VST
• Other images from the VST

Contacts:

Richard Hook
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org 

Source: ESO

Caught For The First Time: The Early Flash Of An Exploding Star

The brilliant flash of an exploding star’s shockwave—what astronomers call the “shock breakout” -- is illustrated in this video animation. The cartoon video begins with a view of a red supergiant star that is 500 hundred times bigger and 20,000 brighter than our sun. When the star’s internal furnace can no longer sustain nuclear fusion its core to collapses under gravity. A shockwave from the implosion rushes upward through the star’s layers. The shockwave initially breaks through the star’s visible surface as a series of finger-like plasma jets. Only 20 minute later the full fury of the shockwave reaches the surface and the doomed star blasts apart as a supernova explosion. This animation is based on photometric observations made by NASA’s Kepler space telescope. By closely monitoring the star KSN 2011d, located 1.2 billion light-years away, Kepler caught the onset of the early flash and subsequent explosion. Credits: Credit: NASA Ames, STScI/G. Bacon.  Youtube

The diagram illustrates the brightness of a supernova event relative to the sun as it unfolds. For the first time, a supernova shockwave has been observed in the optical wavelength or visible light as it reaches the surface of the star. This early flash of light is called a shock breakout. The explosive death of this star, called KSN 2011d, as it reaches its maximum brightness takes 14 days. The shock breakout itself lasts only about 20 minutes, so catching the flash of energy is an investigative milestone for astronomers. The unceasing gaze of NASA's Kepler space telescope allowed astronomers to see, at last, this early moment as the star blows itself to bits. Supernovae like these — known as Type II — begin when the internal furnace of a star runs out of nuclear fuel causing its core to collapse as gravity takes over. This type of star is called a red supergiant star and it is 20,000 times brighter than our sun. As the supergiant star goes supernova, the energy traveling from the core reaches the surfaces with a burst of light that is 130,000,000 times brighter than the sun. The star continues to explode and grow reaching maximum brightness that is about 1,000,000,000 times brighter than the sun. Credits: NASA Ames/W. Stenzel

The brilliant flash of an exploding star’s shockwave—what astronomers call the “shock breakout”—has been captured for the first time in the optical wavelength or visible light by NASA's planet-hunter, the Kepler space telescope. 

An international science team led by Peter Garnavich, an astrophysics professor at the University of Notre Dame in Indiana, analyzed light captured by Kepler every 30 minutes over a three-year period from 500 distant galaxies, searching some 50 trillion stars. They were hunting for signs of massive stellar death explosions known as supernovae.

In 2011, two of these massive stars, called red supergiants, exploded while in Kepler’s view. The first behemoth, KSN 2011a, is nearly 300 times the size of our sun and a mere 700 million light years from Earth. The second, KSN 2011d, is roughly 500 times the size of our sun and around 1.2 billion light years away.
“To put their size into perspective, Earth's orbit about our sun would fit comfortably within these colossal stars,” said Garnavich.

Whether it’s a plane crash, car wreck or supernova, capturing images of sudden, catastrophic events is extremely difficult but tremendously helpful in understanding root cause. Just as widespread deployment of mobile cameras has made forensic videos more common, the steady gaze of Kepler allowed astronomers to see, at last, a supernova shockwave as it reached the surface of a star. The shock breakout itself lasts only about 20 minutes, so catching the flash of energy is an investigative milestone for astronomers.

“In order to see something that happens on timescales of minutes, like a shock breakout, you want to have a camera continuously monitoring the sky,” said Garnavich. “You don’t know when a supernova is going to go off, and Kepler's vigilance allowed us to be a witness as the explosion began.”

Supernovae like these — known as Type II — begin when the internal furnace of a star runs out of nuclear fuel causing its core to collapse as gravity takes over.

The two supernovae matched up well with mathematical models of Type II explosions reinforcing existing theories. But they also revealed what could turn out to be an unexpected variety in the individual details of these cataclysmic stellar events.

While both explosions delivered a similar energetic punch, no shock breakout was seen in the smaller of the supergiants. Scientists think that is likely due to the smaller star being surrounded by gas, perhaps enough to mask the shockwave when it reached the star's surface.

“That is the puzzle of these results,” said Garnavich. “You look at two supernovae and see two different things. That’s maximum diversity.”

Understanding the physics of these violent events allows scientists to better understand how the seeds of chemical complexity and life itself have been scattered in space and time in our Milky Way galaxy

"All heavy elements in the universe come from supernova explosions. For example, all the silver, nickel, and copper in the earth and even in our bodies came from the explosive death throes of stars," said Steve Howell, project scientist for NASA's Kepler and K2 missions at NASA’s Ames Research Center in California's Silicon Valley. "Life exists because of supernovae."

Garnavich is part of a research team known as the Kepler Extragalactic Survey or KEGS. The team is nearly finished mining data from Kepler’s primary mission, which ended in 2013 with the failure of reaction wheels that helped keep the spacecraft steady. However, with the reboot of the Kepler spacecraft as NASA's K2 mission, the team is now combing through more data hunting for supernova events in even more galaxies far, far away.

"While Kepler cracked the door open on observing the development of these spectacular events, K2 will push it wide open observing dozens more supernovae," said Tom Barclay, senior research scientist and director of the Kepler and K2 guest observer office at Ames. "These results are a tantalizing preamble to what's to come from K2!"

In addition to Notre Dame, the KEGS team also includes researchers from the University of Maryland in College Park; the Australian National University in Canberra, Australia; the Space Telescope Science Institute in Baltimore, Maryland; and the University of California, Berkeley.

The research paper reporting this discovery has been accepted for publication in the Astrophysical Journal.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

Authored by H. Pat Brennan/JPL and Michele Johnson/Ames

 Media contact: 

Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-6982
michele.johnson@nasa.gov

Source: NASA/Kepler and K2