The Pillars of Creation Revealed in 3D

PR Image eso1518a

3D data visualisation of the Pillars of Creation

PR Image eso1518b

Colour composite view of the Pillars of Creation from MUSE data

PR Image eso1518c

The three-dimensional view of the Pillars of Creation from MUSE

 

PR Image eso1518d

Messier 16 in the constellation of Serpens Cauda (The Tail of the Serpent)

 

PR Image eso1518e

Digitized Sky Survey Image of the Eagle Nebula 

**************************************************************************************************

Videos

PR Video eso1518a

3D data visualisation of the Pillars of Creation

PR Video eso1518b

3D data visualisation of the Pillars of Creation 

New study suggests that iconic structures more aptly named the Pillars of Destruction

Using the MUSE instrument on ESO’s Very Large Telescope (VLT), astronomers have produced the first complete three-dimensional view of the famous Pillars of Creation in the Eagle Nebula, Messier 16. The new observations demonstrate how the different dusty pillars of this iconic object are distributed in space and reveal many new details — including a previously unseen jet from a young star. Intense radiation and stellar winds from the cluster’s brilliant stars have sculpted the dusty Pillars of Creation over time and should fully evaporate them in about three million years.

The original NASA/ESA Hubble Space Telescope image of the famous Pillars of Creation was taken two decades ago and immediately became one of its most famous and evocative pictures. Since then, these billowing clouds, which extend over a few light-years [1], have awed scientists and the public alike.

The jutting structures, along with the nearby star cluster, NGC 6611, are parts of a star formation region called the Eagle Nebula, also known as Messier 16 or M16. The nebula and its associated objects are located about 7000 light-years away in the constellation of Serpens (The Serpent).

The Pillars of Creation are a classic example of the column-like shapes that develop in the giant clouds of gas and dust that are the birthplaces of new stars. The columns arise when immense, freshly formed blue–white O and B stars give off intense ultraviolet radiation and stellar winds that blow away less dense materials from their vicinity.

Denser pockets of gas and dust, however, can resist this erosion for longer. Behind such thicker dust pockets, material is shielded from the harsh, withering glare of O and B stars. This shielding creates dark "tails" or “elephant trunks”, which we see as the dusky body of a pillar, that point away from the brilliant stars.

ESO's MUSE instrument on the Very Large Telescope has now helped illustrate the ongoing evaporation of the Pillars of Creation in unprecedented detail, revealing their orientation.

MUSE has shown that the tip of the left pillar is facing us, atop a pillar that is is actually situated behind NGC 6611, unlike the other pillars. This tip is bearing the brunt of the radiation from NGC 6611’s stars, and as a result looks brighter to our eyes than the bottom left, middle and right pillars, whose tips are all pointed away from our view.

Astronomers hope to better understand how young O and B stars like those in NGC 6611 influence the formation of subsequent stars. Numerous studies have identified protostars forming in these clouds — they are indeed Pillars of Creation. The new study also reports fresh evidence for two gestating stars in the left and middle pillars as well as a jet from a young star that had escaped attention up to now.

For more stars to form in environments like the Pillars of Creation, it is a race against time as intense radiation from the powerful stars that are already shining continues to grind away at the pillars.

By measuring the Pillars of Creation’s rate of evaporation, MUSE has given astronomers a time frame for when the pillars will be no more. They shed about 70 times the mass of the Sun every million years or so. Based on the their present mass of about 200 times that of the Sun, the Pillars of Creation have an expected lifetime of perhaps three million more years — an eyeblink in cosmic time. It seems that an equally apt name for these iconic cosmic columns might be the Pillars of Destruction.

Notes

[1] The left pillar, considered as a complete object from top to bottom, is estimated to be about four light-years in length. It is the longest pillar and about twice the height of the right pillar.

More Information

This research was presented in a paper entitled "The Pillars of Creation revisited with MUSE: gas kinematics and high-mass stellar feedback traced by optical spectroscopy" by A. F. McLeod et al., to appear in the journal Monthly Notices of the Royal Astronomical Society on 30 April 2015.

The team is composed of A. F. Mc Leod (ESO, Garching, Germany), J. E. Dale (Universitäts-Sternwarte München, München, Germany; Excellence Cluster Universe, Garching bei München, Germany), A. Ginsburg (ESO), B. Ercolano (Universitats-Sternwarte München,; Excellence Cluster Universe), M. Gritschneder (Universitats-Sternwarte München), S. Ramsay (ESO) and L. Testi (ESO; INAF/Osservatorio Astrofisico di Arcetri, Firenze, Italy).

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

• Research paper
• Photos of the VLT
• Photos of MUSE

Contacts

Anna Faye Mc Leod
ESO
Garching bei München, Germany
Tel: +49 89 3200 6321
Email: amcleod@eso.org

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 

NASA's NuSTAR Captures Possible 'Screams' from Zombie Stars

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has captured a new high-energy X-ray view (magenta) of the bustling center of our Milky Way galaxy. The smaller circle shows the center of our galaxy where the NuSTAR image was taken. Credits: NASA/JPL-Caltech. Full image and caption

Peering into the heart of the Milky Way galaxy, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has spotted a mysterious glow of high-energy X-rays that, according to scientists, could be the "howls" of dead stars as they feed on stellar companions.

"We can see a completely new component of the center of our galaxy with NuSTAR's images," said Kerstin Perez of Columbia University in New York, lead author of a new report on the findings in the journal Nature. "We can't definitively explain the X-ray signal yet -- it's a mystery. More work needs to be done."

The center of our Milky Way galaxy is bustling with young and old stars, smaller black holes and other varieties of stellar corpses – all swarming around a supermassive black hole called Sagittraius A*.

NuSTAR, launched into space in 2012, is the first telescope capable of capturing crisp images of this frenzied region in high-energy X-rays. The new images show a region around the supermassive black hole about 40 light-years across. Astronomers were surprised by the pictures, which reveal an unexpected haze of high-energy X-rays dominating the usual stellar activity.

"Almost anything that can emit X-rays is in the galactic center," said Perez. "The area is crowded with low-energy X-ray sources, but their emission is very faint when you examine it at the energies that NuSTAR observes, so the new signal stands out."

Astronomers have four potential theories to explain the baffling X-ray glow, three of which involve different classes of stellar corpses. When stars die, they don't always go quietly into the night. Unlike stars like our sun, collapsed dead stars that belong to stellar pairs, or binaries, can siphon matter from their companions. This zombie-like "feeding" process differs depending on the nature of the normal star, but the result may be an eruption of X-rays.

According to one theory, a type of stellar zombie called a pulsar could be at work. Pulsars are the collapsed remains of stars that exploded in supernova blasts. They can spin extremely fast and send out intense beams of radiation. As the pulsars spin, the beams sweep across the sky, sometimes intercepting the Earth, like lighthouse beacons.

"We may be witnessing the beacons of a hitherto hidden population of pulsars in the galactic center," said co-author Fiona Harrison of the California Institute of Technology (Caltech) in Pasadena, and principal investigator of NuSTAR. "This would mean there is something special about the environment in the very center of our galaxy."

Other possible culprits include heavy-set stellar corpses called white dwarfs, which are the collapsed, burned-out remains of stars not massive enough to explode in supernovae. Our sun is such a star, and is destined to become a white dwarf in about five billion years. Because these white dwarfs are much denser than they were in their youth, they have stronger gravity and can produce higher-energy X-rays than normal. Another theory points to small black holes that slowly feed off their companion stars, radiating X-rays as material plummets down into their bottomless pits.

Alternatively, the source of the high-energy X-rays might not be stellar corpses at all, astronomers say, but rather a diffuse haze of charged particles, called cosmic rays. The cosmic rays might originate from the supermassive black hole at the center of the galaxy as it devours material. When the cosmic rays interact with surrounding, dense gas, they emit X-rays. 

However, none of these theories match what is known from previous research, leaving the astronomers largely stumped.

"This new result just reminds us that the galactic center is a bizarre place," said co-author Chuck Hailey of Columbia University. "In the same way people behave differently walking on the street instead of jammed on a crowded rush hour subway, stellar objects exhibit weird behavior when crammed in close quarters near the supermassive black hole."

The team says more observations are planned. Until then, theorists will be busy exploring the above scenarios or coming up with new models to explain what could be giving off the puzzling high-energy X-ray glow.

"Every time that we build small telescopes like NuSTAR, which improve our view of the cosmos in a particular wavelength band, we can expect surprises like this," said Paul Hertz, the astrophysics division director at NASA Headquarters in Washington.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Pasadena, California, for NASA's Science Mission Directorate in Washington.

Felicia Chou
Headquarters, Washington
202-358-0257
felicia.chou@nasa.gov

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

Source: NASA/NuSTAR

Robotically Discovering Earth’s Nearest Neighbors

Artist’s impression of a view from the HD 7924 planetary system looking back toward our sun, which would be easily visible to the naked eye. Since HD 7924 is in our northern sky, an observer looking back at the sun would see objects like the Southern Cross and the Magellanic Clouds close to our sun in their sky. Art by Karen Teramura & BJ Fulton, UH IfA.

A team of astronomers using ground-based telescopes in Hawaii, California, and Arizona recently discovered a planetary system orbiting a nearby star that is only 54 light-years away. All three planets orbit their star at a distance closer than Mercury orbits the sun, completing their orbits in just 5, 15, and 24 days.

Astronomers from the University of Hawaii at Manoa, the University of California, Berkeley, the University of California Observatories, and Tennessee State University found the planets using measurements from the Automated Planet Finder (APF) Telescope at Lick Observatory in California, the W. M. Keck Observatory on Maunakea, Hawaii, and the Automatic Photometric Telescope (APT) at Fairborn Observatory in Arizona. 

The team discovered the new planets by detecting the wobble of the star HD 7924 as the planets orbited and pulled on the star gravitationally. APF and Keck Observatory traced out the planets’ orbits over many years using the Doppler technique that has successfully found hundreds of mostly larger planets orbiting nearby stars. APT made crucial measurements of the brightness of HD 7924 to assure the validity of the planet discoveries.

The new APF facility offers a way to speed up the planet search. Planets can be discovered and their orbits traced much more quickly because APF is a dedicated facility that robotically searches for planets every clear night. Training computers to run the observatory all night, without human oversight, took years of effort by the University of California Observatories staff and graduate students on the discovery team.

“We initially used APF like a regular telescope, staying up all night searching star to star. But the idea of letting a computer take the graveyard shift was more appealing after months of little sleep. So we wrote software to replace ourselves with a robot,” said University of Hawaii graduate student BJ Fulton.

The Keck Observatory found the first evidence of planets orbiting HD 7924, discovering the innermost planet in 2009 using the HIRES instrument installed on the 10-meter Keck I telescope. This same combination was also used to find other super-Earths orbiting nearby stars in planet searches led by UH astronomer Andrew Howard and UC Berkeley Professor Geoffrey Marcy. It took five years of additional observations at Keck Observatory and the year-and-a-half campaign by the APF Telescope to find the two additional planets orbiting HD 7924.

The Kepler Space Telescope has discovered thousands of extrasolar planets and demonstrated that they are common in our Milky Way galaxy. However, nearly all of these planets are far from our solar system. Most nearby stars have not been thoroughly searched for the small “super-Earth” planets (larger than Earth but smaller than Neptune) that Kepler found in great abundance.

This discovery shows the type of planetary system that astronomers expect to find around many nearby stars in the coming years. “The three planets are unlike anything in our solar system, with masses 7-8 times the mass of Earth and orbits that take them very close to their host star,” explains UC Berkeley graduate student Lauren Weiss. 

“This level of automation is a game-changer in astronomy,” says Howard. “It’s a bit like owning a driverless car that goes planet shopping.”

Observations by APF, APT, and Keck Observatory helped verify the planets and rule out other explanations. “Starspots, like sunspots on the sun, can momentarily mimic the signatures of small planets. Repeated observations over many years allowed us to separate the starspot signals from the signatures of these new planets,” explains Evan Sinukoff, a UH graduate student who contributed to the discovery.

The robotic observations of HD 7924 are the start of a systematic survey for super-Earth planets orbiting nearby stars. Fulton will lead this two-year search with the APF as part of his research for his doctoral dissertation. “When the survey is complete we will have a census of small planets orbiting sun-like stars within approximately 100 light-years of Earth,” says Fulton. 

Telescope automation is relatively new to astronomy, and UH astronomers are building two forefront facilities. Christoph Baranec built the Robo-AO observatory to takes high-resolution images using a laser to remove the blur of Earth’s atmosphere, and John Tonry is developing ATLAS, a robotic observatory that will hunt for killer asteroids. 

The paper presenting this work, “Three super-Earths orbiting HD 7924,” has been accepted for publication in the Astrophysical Journal and is available at no cost at http://arxiv.org/abs/1504.06629. The other authors of the paper are Howard Isaacson (UC Berkeley), Gregory Henry (TSU), and Bradford Holden and Robert I. Kibrick (UCO).

In honor of the donations of Gloria and Ken Levy that helped facilitate the construction of the Levy spectrograph on APF and supported Lauren Weiss, the team has informally named the HD 7924 system the “Levy Planetary System.” The team also acknowledges the support of NASA, the U.S. Naval Observatory, and the University of California for its support of Lick Observatory. 

Contacts:

BJ Fulton
bfulton@hawaii.edu
+1 408-528-4858

Dr. Andrew Howard
howard@ifa.hawaii.edu
+1 808-208-1224

Ms. Louise Good
Media Contact
+1 808-381-2939
good@ifa.hawaii.edu

Versions of artwork

With labels:
Small JPEG - Large JPEG - RGB TIFF

Without labels:
Small JPEG - Large JPEG - RGB TIFF

Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Maunakea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii.

Source:  Institute for Astronomy at the University of Hawaii

Water Could Have Been Abundant in the First Billion Years

This Hubble image features dark knots of gas and dust known as "Bok globules," which are dense pockets in larger molecular clouds. Similar islands of material in the early universe could have held as much water vapor as we find in our galaxy today, despite containing a thousand times less oxygen. Credit: NASA, ESA, and The Hubble Heritage Team. High Resolution (jpg) - Low Resolution (jpg)

How soon after the Big Bang could water have existed? Not right away, because water molecules contain oxygen and oxygen had to be formed in the first stars. Then that oxygen had to disperse and unite with hydrogen in significant amounts. New theoretical work finds that despite these complications, water vapor could have been just as abundant in pockets of space a billion years after the Big Bang as it is today.

"We looked at the chemistry within young molecular clouds containing a thousand times less oxygen than our Sun. To our surprise, we found we can get as much water vapor as we see in our own galaxy," says astrophysicist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics (CfA).

The early universe lacked elements heavier than hydrogen and helium. The first generation of stars are believed to have been massive and short-lived. Those stars generated elements like oxygen, which then spread outward via stellar winds and supernova explosions. This resulted in "islands" of gas enriched in heavy elements. Even these islands, however, were much poorer in oxygen than gas within the Milky Way today.

The team examined the chemical reactions that could lead to the formation of water within the oxygen-poor environment of early molecular clouds. They found that at temperatures around 80 degrees Fahrenheit (300 Kelvin), abundant water could form in the gas phase despite the relative lack of raw materials.

"These temperatures are likely because the universe then was warmer than today and the gas was unable to cool effectively," explains lead author and PhD student Shmuel Bialy of Tel Aviv University.

"The glow of the cosmic microwave background was hotter, and gas densities were higher," adds Amiel Sternberg, a co-author from Tel Aviv University.

Although ultraviolet light from stars would break apart water molecules, after hundreds of millions of years an equilibrium could be reached between water formation and destruction. The team found that equilibrium to be similar to levels of water vapor seen in the local universe.

"You can build up significant quantities of water in the gas phase even without much enrichment in heavy elements," adds Bialy.

This current work calculates how much water could exist in the gas phase within molecular clouds that will form later generations of stars and planets. It doesn't address how much water would exist in ice form (which dominates within our galaxy) or what fraction of all the water might actually be incorporated into newly forming planetary systems

This work has been accepted for publication in the Astrophysical Journal Letters and is available online. The authors are Shmuel Bialy & Amiel Sternberg (Tel Aviv University) and Avi Loeb (CfA). This joint project was carried out as part of the Raymond and Beverly Sackler Tel Aviv University - Harvard Astronomy Program.

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
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Source: Harvard-Smithsonian Center for Astrophysics (CfA)

Strange Supernova is "Missing Link" in Gamma-Ray Burst Connection

In an ordinary core-collapse supernova with no "central engine," ejected material expands outward nearly spherically, left. At right, a strong central engine propels jets of material at nearly the speed of light and generates a gamma-ray burst (GRB). The center panel shows an intermediate supernova like SN 2012ap, with a weak central engine, weak jets, and no GRB. CREDIT: Bill Saxton, NRAO/AUI/NSF

Astronomers using the National Science Foundation's Very Large Array (VLA) have found a long-sought "missing link" between supernova explosions that generate gamma-ray bursts (GRBs) and those that don't. The scientists found that a stellar explosion seen in 2012 has many characteristics expected of one that generates a powerful burst of gamma rays, yet no such burst occurred.

"This is a striking result that provides a key insight about the mechanism underlying these explosions," said Sayan Chakraborti, of the Harvard-Smithsonian Center for Astrophysics (CfA). "This object fills in a gap between GRBs and other supernovae of this type, showing us that a wide range of activity is possible in such blasts," he added.

The object, called Supernova 2012ap (SN 2012ap) is what astronomers term a core-collapse supernova. This type of blast occurs when the nuclear fusion reactions at the core of a very massive star no longer can provide the energy needed to hold up the core against the weight of the outer parts of the star. The core then collapses catastrophically into a superdense neutron star or a black hole. The rest of the star's material is blasted into space in a supernova explosion.

The most common type of such a supernova blasts the star's material outward in a nearly-spherical bubble that expands rapidly, but at speeds far less than that of light. These explosions produce no burst of gamma rays.

In a small percentage of cases, the infalling material is drawn into a short-lived swirling disk surrounding the new neutron star or black hole. This accretion disk generates jets of material that move outward from the disk's poles at speeds approaching that of light. This combination of a swirling disk and its jets is called an "engine," and this type of explosion produces gamma-ray bursts.

The new research shows, however, that not all "engine-driven" supernova explosions produce gamma-ray bursts.

"This supernova had jets moving at nearly the speed of light, and those jets were quickly slowed down, just like the jets we see in gamma-ray bursts," said Alicia Soderberg, also of CfA.

An earlier supernova seen in 2009 also had fast jets, but its jets expanded freely, without experiencing the slowdown characteristic of those that generate gamma-ray bursts. The free expansion of the 2009 object, the scientists said, is more like what is seen in supernova explosions with no engine, and probably indicates that its jet contained a large percentage of heavy particles, as opposed to the lighter particles in gamma-ray-burst jets. The heavy particles more easily make their way through the material surrounding the star.

"What we see is that there is a wide diversity in the engines in this type of supernova explosion," Chakraborti said. "Those with strong engines and lighter particles produce gamma-ray bursts, and those with weaker engines and heavier particles don't," he added.

"This object shows that the nature of the engine plays a central role in determining the characteristics of this type of supernova explosion," Soderberg said.

Chakraborti and Soderberg worked with an international team of scientists from five continents. In addition to the VLA, they also used data from the Giant Meterwave Radio Telescope (GMRT) in India and the InterPlanetary Network (IPN) of spacecraft equipped with GRB detectors. The team, led by Chakraborti, is reporting their work in a paper accepted to the Astrophysical Journal. Other articles, led by co-authors Raffaella Margutti and Dan Milisavljevic, also report on the X-ray and optical follow-up on SN 2012ap using a suite of space and ground-based facilities.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Contact:

Dave Finley, Public Information Officer
(575) 835-7302
dfinley@nrao.edu

Source:  National Radio Astronomy Observatory (NRAO)

Birth of a Radio Phoenix

A false-color X-ray image of the galaxy cluster Abell 1033. The white contours help identify the X-ray flux levels, and the red contours trace the radio emission. The elongated red structure in the lower center is a radio phoenix: fossil gas that has been reheated by shocks from a nearby galaxy merger (obscured in this view). Credit: Chandra, VLA

Abell 1033 is a cluster of over 350 galaxies located about 1.7 billion light-years away. Collisions between galaxies in clusters are common events, and each merger heats and shocks the nearby gas. The rapidly moving, ionized gas then radiates intensely at radio wavelengths. There are three types of radio sources found in these clusters. The first, called radio relics, are found in the outskirts of galaxies and have radiation signatures characteristic of shocked material over large scales. The second type, called radio haloes, are centrally located in the cluster and are probably the result of large turbulent motions set up during collisions. 

A radio phoenix is the third type of cluster radio source, and is much less well studied. After the initial effects of a collision have died down and the gas has cooled, the radio emission subsides. But a subsequent merger nearby can produce a strong shock wave, and if that passes through the fossil material it can compress and re-energize it to emit in the radio again. 

CfA astronomers Georgiana Ogrean and Reinout van Weeren, with five colleagues, used data from the Chandra X-ray Observatory, the Westerbork Synthesis Radio Telescope, the Very Large Array ad the optical Sloan Digital Sky Survey to study the Abell 1033 cluster and its family of galaxies. They discovered two subclusters in the source that seem to have recently collided; they were spotted from their X-ray emission. Close to this region, and to a galactic nucleus, the team spotted a radio source with the emission and charged particle characteristics of a radio phoenix. The scientists conclude that shocks from the recent merger have propagated into old gas, reinvigorating this fossil remnant to new life.

Reference(s):

"Abell 1033: Birth of a Radio Phoenix," F. de Gasperin, G. A. Ogrean, R. J. van Weeren, W. A. Dawson, M. Bruggen, A. Bonafede1 and A. Simionescu, MNRAS 448, 2197, 2015.

Source: Smithsonian Astrophysical Observatory

Astronomers Find New Details about Star Formation in Ancient Galaxy Protoclusters

Figure 1: Pseudo-color composite image of PKS 1138-262 region, derived from Hubble Space Telescope's ACS/WFC data archive (F814W and F475W). This region is one of the target protoclusters observed by MOIRCS on Subaru Telescope. (Credit: NAOJ/HST)

Figure 2: Mass-growth history expected of massive cluster of galaxies that have about 10^15 solar masses present day. Red spots are from this study. Black and grayer are for other massive cluster of galaxies, studied by the author's team and other research teams, respectively. (Credit: NAOJ)

Figure 3: Plot of stellar mass of the galaxies versus metallicity of gas in them. Gray and pale blue curves are for the present-day (nearby) galaxies and field galaxies at 11 billion years ago, respectively. Red is the current study about the proto-cluster of galaxies. The galaxies in the proto-clusters clearly show higher metallicity compared with the ones in the general fields at about the same time of the history in the universe. (Credit: NAOJ)

Figure 4: Illustrations of the metal enrichment processes (chemical evolution) in the field galaxies and the proto-cluster galaxies. Left (figure 4a) is for the galaxies in the general fields while the middle and the right (figures 4b and 4c, respectively) show their model that explain the unique enrichment processes of the heavy elements in the galaxies in the proto-clusters. (Credit: NAOJ)

Ongoing studies of distant galaxy protoclusters using the Multi-Object Infrared Camera and Spectrograph (MOIRCS) instrument on the Subaru Telescope is giving astronomers a closer look at the characteristics of star-forming regions in galaxies in the early universe. A team of astronomers from the National Astronomical Observatory of Japan (NAOJ) and SOKENDAI (Graduate University of Advanced Studies, Japan) are tracking velocity structures and gaseous metallicities in galaxies in two protoclusters located in the direction of the constellation Serpens. These appear around the radio galaxies PKS 1138-262 (at a redshift of 2.2, Figure 1) and USS 1558-003 (at a redshift of 2.5). The clusters appear as they would have looked 11 billion years ago, and the team concluded that they are in the process of cluster formation that has led to present-day galaxy clusters.

The MOIRCS near-infrared spectrograph is very effective for studies focused on the distant, early universe because strong emission lines from star-forming galaxies are redshifted from the optical to the near-infrared regime. This gives astronomers unique insights into these activities. (Note 1)

Based on the MOIRCS data, the team estimated that both protoclusters have a weight of about 10^14 solar masses (Figure 2). These follow the typical mass growth history of the today's most massive clusters, such as the 'Coma Cluster.' That makes the two protoclusters ideal laboratories for exploring early phasesof galaxy formation in a unique clustered environment.

The metallicity of the gases in the protocluster galaxies was studied using multiple spectral lines emitted from them. The result shows their gaseous metallicities are chemically enriched compared with those of galaxies in the general fields (Figure 3). Metals (elements heavier than hydrogen and helium) are created in the interiors of stars as they evolve and then released into surrounding gas through supernova explosions or stellar winds (often referred to as chemical evolution; Figure 4a).

The difference in gaseous metallicity between protoclusters and general fields suggests that star-formation histories and/or gas inflow/outflow processes should be different in the protocluster regions. The result also suggests that galaxy formation has already been influenced by environmental conditions in the era that star-formation activities are the most active across the universe. This would be an early phase of strong environmental effects seen in the present galaxy clusters.

In order to explain the metallicity excess in the protoclusters, the team members focused attention on the environmental effects of inflow and outflow mechanism on the galaxy formation process. Recent works report that inflow and outflow activities were most significant eleven billion years ago (at redshift ~2), and were about a hundred times more active relative to those in the local universe.

Clusters of galaxies are large self-gravitating systems in which galaxies and ionized gas are bound by massive amounts of dark matter. In such unique, dense environments, galaxies move at a speed of about 1000 kilometers per second. Due to this high speed, the galaxies are exposed to high pressure from intercluster medium. As a result, the outer regions with relatively poor metallicity are stripped. It is like the strong air resistance of air a bicycle rider experiences. In this case, the gaseous metallicities become higher because the chemical enrichment process takes place mainly in metal-rich central regions (Figure 4b). Another possibility is that the surrounding high-pressure, inter-cluster medium prevents outflowing gas from escaping from the galaxies (Figure 4c). This also results in higher gaseous metallicities of the cluster galaxies.

The research team concludes that the metallicity excess in the protocluster regions results from unique phenomena occurring in the cluster environment. The PI of this research, Mr. Rhythm Shimakawa of NAOJ and SOKENDAI (Note 2), is determined to continue studying the detailed physical properties of individual forming galaxies in the protoclusters to find clear evidence that proves this hypothesis.

This article is based on results from two research papers published in the Monthly Notices of the Royal Astronomical Society:

Rhythm Shimakawa, Tadayuki Kodama, Ken-ichi Tadaki, Ichi Tanaka, Masao Hayashi and Yusei Koyama, "Identification of the progenitors of rich clusters and member galaxies in rapid formation at z > 2", Volume 441, Issue 1, p.L1-L5, published in June 11, 2014,
and
Rhythm Shimakawa, Tadayuki Kodama, Ken-ichi Tadaki, Masao Hayashi, Yusei Koyama, Ichi Tanaka "An early phase of environmental effects on galaxy properties unveiled by near-infrared spectroscopy of protocluster galaxies at z>2", Volume 448, Issue 1, p.666-680, published in March 21, 2015.

This research is supported in part by a Grant-in-Aid for the Scientific Research (Nos. 21340045 and 24244015) by the Japanese Ministry of Education, Culture, Sports, Science and Technology.

Authors:

• Rhythm Shimakawa (Subaru Telescope, National Astronomical Observatory of Japan [NAOJ]/SOKENDAI(Graduate University for Advanced Studies))
• Tadayuki Kodama (Optical and Infrared Astronomy Division, NAOJ/SOKENDAI)
• Ichi Tanaka (Subaru Telescope, NAOJ)
• Kenichi Tadaki (Max-Planck-Institute fur Extraterrestrische Physic, Germany)
• Masao Hayashi (Optical and Infrared Astronomy Division, NAOJ)
• Yusei Koyama (Institute of Space Astronomical Science, Japan Aerospace Exploration Agency)

Notes:

1. See the Web release by M. Hayashi, "Discovery of an Ancient Celestial City Undergoing Rapid Growth: A Young Protocluster of Active Star-Forming Galaxies".
2. Mr. Rhythm Shimakawa received the first "SOKENDAI Future Scientist Award" for his research "Environmental effects on galaxy formation: When and how did spiral and elliptical galaxies diverge?", which includes the two papers referred in this article.

Source: Subaru Telescope

Astronomers Find Runaway Galaxies

This schematic illustrates the creation of a runaway galaxy. In the first panel, an "intruder" spiral galaxy approaches a galaxy cluster center, where a compact elliptical galaxy (cE) already revolves around a massive central elliptical galaxy. In the second panel, a close encounter occurs and the compact elliptical receives a gravitational kick from the intruder. In the third panel, the compact elliptical escapes the galaxy cluster while the intruder is devoured by the giant elliptical galaxy in the cluster center. Credit: NASA, ESA, and the Hubble Heritage Team. High Resolution (jpg) - Low Resolution (jpg) - unlabeled image

Cambridge, MA - We know of about two dozen runaway stars, and have even found one runaway star cluster escaping its galaxy forever. Now, astronomers have spotted 11 runaway galaxies that have been flung out of their homes to wander the void of intergalactic space.

"These galaxies are facing a lonely future, exiled from the galaxy clusters they used to live in," said astronomer Igor Chilingarian (Harvard-Smithsonian Center for Astrophysics/Moscow State University). Chilingarian is the lead author of the study, which is appearing in the journal Science.

An object is a runaway if it's moving faster than escape velocity, which means it will depart its home never to return. In the case of a runaway star, that speed is more than a million miles per hour (500 km/s). A runaway galaxy has to race even faster, traveling at up to 6 million miles per hour (3,000 km/s).

Chilingarian and his co-author, Ivan Zolotukhin (L'Institut de Recherche en Astrophysique et Planetologie/Moscow State University), initially set out to identify new members of a class of galaxies called compact ellipticals. These tiny blobs of stars are bigger than star clusters but smaller than a typical galaxy, spanning only a few hundred light-years. In comparison, the Milky Way is 100,000 light-years across. Compact ellipticals also weigh 1000 times less than a galaxy like our Milky Way.

Prior to this study, only about 30 compact elliptical galaxies were known, all of them residing in galaxy clusters. To locate new examples Chilingarian and Zolotukhin sorted through public archives of data from the Sloan Digital Sky Survey and the GALEX satellite.

Their search identified almost 200 previously unknown compact ellipticals. Of those, 11 were completely isolated and found far from any large galaxy or galaxy cluster.

"The first compact ellipticals were all found in clusters because that's where people were looking. We broadened our search, and found the unexpected," said Zolotukhin.

These isolated compact galaxies were unexpected because theorists thought they originated from larger galaxies that had been stripped of most of their stars through interactions with an even bigger galaxy. So, the compact galaxies should all be found near big galaxies.

Not only were the newfound compact ellipticals isolated, but also they were moving faster than their brethren in clusters.

"We asked ourselves, what else could explain them? The answer was a classic three-body interaction," stated Chilingarian.

A hypervelocity star can be created if a binary star system wanders close to the black hole at the center of our galaxy. One star gets captured while the other is thrown away at tremendous speed.

Similarly, a compact elliptical could be paired with the big galaxy that stripped it of its stars. Then a third galaxy blunders into the dance and flings the compact elliptical away. As punishment, the intruder gets accreted by the remaining big galaxy.

This discovery represents a prominent success of the Virtual Observatory - a project to make data from large astronomical surveys easily available to researchers. So-called data mining can result in finds never anticipated when the original data was collected.

"We recognized we could use the power of the archives to potentially unearth something interesting, and we did," added Chilingarian.

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
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Source: Harvard-Smithsonian Center for Astrophysics (CfA)

Celestial fireworks celebrate Hubble’s 25th anniversary

PR Image heic1509a

Westerlund 2 — Hubble’s 25th anniversary image

PR Image heic1509b

Wide-field image of Westerlund 2 (ground-based image)

PR Image heic1509c

The star cluster Westerlund 2

PR Image heic1509d

Star-forming region Gum 29

PR Image heic1509e

Pillars around Westerlund 2

PR Image heic1509f

New stars around Westerlund 2 

******************************************************************************************

VIDEOS

PR Video heic1509a

Hubblecast Episode 84: A starry snapshot for Hubble’s 25th

PR Video heic1509b

Zoom into Westerlund 2

PR Video heic1509c

Westerlund 2 for fulldome

PR Video heic1509d

Pan across Westerlund 2

PR Video heic1509e

Flight through star cluster Westerlund 2 — fast

PR Video heic1509f

Flight through star cluster Westerlund 2 - slow

The glittering tapestry of young stars flaring to life in this new NASA/ESA Hubble Space Telescope image aptly resembles an exploding shell in a fireworks display. This vibrant image of the star cluster Westerlund 2 has been released to celebrate Hubble’s 25th year in orbit and a quarter of a century of new discoveries, stunning images and outstanding science.

On 24 April 1990 the NASA/ESA Hubble Space Telescope was sent into orbit aboard the space shuttle Discovery as the first space telescope of its kind. It offered a new view of the Universe and has, for 25 years, reached and surpassed all expectations, beaming back data and images that have changed scientists’ understanding of the Universe and the public’s perception of it.

In this image, the sparkling centrepiece of Hubble’s silver anniversary fireworks is a giant cluster of about 3000 stars called Westerlund 2 [1][2]. The cluster resides in a raucous stellar breeding ground known as Gum 29, located 20 000 light-years away in the constellation Carina.

The stellar nursery is difficult to observe because it is surrounded by dust, but Hubble’s Wide Field Camera 3 peered through the dusty veil in near-infrared light, giving astronomers a clear view of the cluster. Hubble’s sharp vision resolves the dense concentration of stars in the central cluster, which measures only about 10 light-years across.

The giant star cluster is only about two million years old, but contains some of the brightest, hottest and most massive stars ever discovered. Some of the heftiest stars are carving deep cavities in the surrounding material by unleashing torrents of ultraviolet light and high speed streams of charged particles, known as stellar winds. These are etching away the enveloping hydrogen gas cloud in which the stars were born and are responsible for the weird and wonderful shapes of the clouds of gas and dust in the image.

The pillars in the image are composed of dense gas and dust, and are resisting erosion from the fierce radiation and powerful winds. These gaseous monoliths are a few light-years tall and point to the central cluster. Other dense regions surround the pillars, including dark filaments of dust and gas.

Besides sculpting the gaseous terrain, the brilliant stars can also help create a succeeding generation of offspring. When the stellar winds hit dense walls of gas, they create shocks, which generate a new wave of star birth along the wall of the cavity. The red dots scattered throughout the landscape are a rich population of forming stars that are still wrapped in their gas and dust cocoons. These stellar foetuses have not yet ignited the hydrogen in their cores to light-up as stars. However, Hubble’s near-infrared vision allows astronomers to identify these fledglings. The brilliant blue stars seen throughout the image are mostly in the foreground.

The image’s central region, containing the star cluster, blends visible-light data taken by the Advanced Camera for Surveys and near-infrared exposures taken by the Wide Field Camera 3. The surrounding region is composed of visible-light observations taken by the Advanced Camera for Surveys.

This image is a testament to Hubble’s observational power and demonstrates that, even with 25 years of operations under its belt, Hubble’s story is by no means over. Hubble has set the stage for its companion the James Webb Space Telescope — scheduled for launch in 2018 — but will not be immediately replaced by this new feat of engineering, instead working alongside it. Now, 25 years after launch, is the time to celebrate Hubble’s future potential as well as its remarkable history.

Notes

[1] A new anniversary image is released every year; last year Hubble snapped the ethereal Monkey Head Nebula (heic1406). The year 2013 saw the release of a strikingly delicate view of the Horsehead Nebula (heic1307), and Hubble’s 22nd year was marked by a huge mosaic of a celestial spider (heic1206)! Other images include a multicoloured view of Saturn (opo9818a), a Tolkien-esque shot of the Carina Nebula (heic1007a), and a beautiful cosmic rose made up of merging galaxies (heic1107a). More anniversary images can be seen here.

[2] Westerlund 2 is named after Swedish astronomer Bengt Westerlund, who discovered the grouping in the 1960s.

Notes for Editors

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

More Information

Image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team

The original observations of Westerlund 2 were obtained by the science team: Antonella Nota (ESA/STScI), Elena Sabbi (STScI), Eva Grebel and Peter Zeidler (Astronomisches Rechen-Institut Heidelberg), Monica Tosi (INAF, Osservatorio Astronomico di Bologna), Alceste Bonanos (National Observatory of Athens, Astronomical Institute), Carol Christian (STScI/AURA) and Selma de Mink (University of Amsterdam). Follow-up observations were made by the Hubble Heritage team: Zoltan Levay (STScI), Max Mutchler, Jennifer Mack, Lisa Frattare, Shelly Meyett, Mario Livio, Carol Christian (STScI/AURA), and Keith Noll (NASA/GSFC).

Links

• Images of Hubble
• For more information on the anniversary activities you can visit the website.

Contacts

Georgia Bladon
ESA/Hubble, Public Information Officer
Garching, Germany
Cell: +44 7816291261
Email: gbladon@partner.eso.org

Ray Villard
Space Telescope Science Institute
Baltimore, USA
Tel: +1-410-338-4514
Email: villard@stsci.edu

Source: ESA/HUBBLE - Space Telescope

Cosmologically Complicating Dust

The Planck astronomy satellite's new submillimeter wavelength image of ripples in the cosmic background, as refined with data taken with the South Pole BICEP2/Keck Array facilities. Scientists from the two teams combined their data to conclude that previously reported measurements attributed to the effects of cosmic inflation are instead almost certainly due to the effects of galactic dust. Credit: ESA, NASA, Planck/BICEP.

The universe was created 13.7 billion years ago in a blaze of light: the big bang. Roughly 380,000 years later, after matter (mostly hydrogen) had cooled enough for neutral atoms to form, light was able to traverse space freely. That light, the cosmic microwave background radiation (CMBR), comes to us from every direction in the sky uniformly ... or so it first seemed. In the last decades, astronomers discovered that the radiation actually has very faint ripples and bumps in it at a level of brightness of only a part in one hundred thousand – the seeds for future structures, like galaxies.

Astronomers have conjectured that these ripples also contain traces of an initial burst of expansion -- the so-called inflation – which swelled the new universe by thirty-three orders of magnitude in a mere ten-to-the-power-minus-33 seconds. Clues about the inflation should be faintly present in the way the cosmic ripples are curled, an effect that is expected to be perhaps one hundred times fainter than the ripples themselves. One year ago, CfA astronomers working at the South Pole amazed the world by reporting evidence for such curling, the "B-mode polarization," and cautiously calculated that the measured strength supported the simplest models of inflation.

Other exotic processes are at work in the universe to make this daunting measurement even more challenging. The principal one is the scattering of light by dust particles in the galaxy that have been aligned by magnetic fields; the light is polarized and twisted in a way that emulates the curling effects of inflation. In 2009, the European Space Agency, with NASA as a partner, launched the Planck satellite to study the CMBR. The first papers from Planck substantially refined the values of key cosmological parameters. In the course of studying the cosmic light, it unavoidably encountered emission from dust grains. Writing in the latest issue of Physical Review Letters, CfA astronomers K.D. Alexander, C.A. Bischoff, I. Buder, J. Connors, C. Dvorkin, K.S. Karkare, J. Kovac, S. Richter, and C.L. Wong joined over one hundred colleagues in reporting their analysis of the galactic dust contribution to the curled CMBR signature using data from both South Pole and Planck experiments.

The scientists conclude that the previously reported curl signal is genuine, but almost certainly due to galactic dust, whose effect turned out to be considerably stronger than had been previously expected, swamping the cosmological signal. The new paper provides much more sensitive limits to cosmological effects, however, and notes that several next-generation experiments at the South Pole and elsewhere are continuing to probe even more deeply. In the next few years, they predict, substantial progress towards finding the faint traces of inflation will be made, and the improved results used to refine the details of cosmic inflation.

Reference(s):

"Joint Analysis of BICEP2/Keck Array and Planck Data," P.A.R. Ade et al. (BICEP2/Keck and Planck Collaborations, Physical Review Letters 114, 101301, 2015

Source: Smithsonian Astrophysical Observatory

Tau Ceti: The next Earth? Probably not

How would an alien world like this look? That’s the question that undergraduate art major Joshua Gonzalez attempted to answer. He worked with Professor Patrick Young’s group to learn how to analyze stellar spectra to find chemical abundances, and inspired by the scientific results, he created two digital paintings of possible unusual extrasolar planets, one being Tau Ceti for his Barrett Honors Thesis. Credit: Joshua Gonzalez.

The list of potential life-supporting planets just got a little shorter

 

As the search continues for Earth-size planets orbiting at just the right distance from their star, a region termed the habitable zone, the number of potentially life-supporting planets grows. In two decades we have progressed from having no extrasolar planets to having too many to search. Narrowing the list of hopefuls requires looking at extrasolar planets in a new way. Applying a nuanced approach that couples astronomy and geophysics, Arizona State University researchers report that from that long list we can cross off cosmic neighbor Tau Ceti.

The Tau Ceti system, popularized in several fictional works, including Star Trek, has long been used in science fiction, and even popular news, as a very likely place to have life due to its proximity to Earth and the star’s sun-like characteristics. Since December 2012 Tau Ceti has become even more appealing, thanks to evidence of possibly five planets orbiting it, with two of these – Tau Ceti e and f – potentially residing in the habitable zone.

Using the chemical composition of Tau Ceti, the ASU team modeled the star’s evolution and calculated its habitable zone. Although their data confirms that two planets (e and f) may be in the habitable zone it doesn’t mean life flourishes or even exists there.

“Planet e is in the habitable zone only if we make very generous assumptions. Planet f initially looks more promising, but modeling the evolution of the star makes it seem probable that it has only moved into the habitable zone recently as Tau Ceti has gotten more luminous over the course of its life,” explains astrophysicist Michael Pagano, ASU postdoctoral researcher and lead author of the paper appearing in the Astrophysical Journal. The collaboration also included ASU astrophysicists Patrick Young and Amanda Truitt and mineral physicist Sang-Heon (Dan) Shim.

Based upon the team’s models, planet f has likely been in the habitable zone much less than 1 billion years. This sounds like a long time, but it took Earth’s biosphere about 2 billion years to produce potentially detectable changes in its atmosphere. A planet that entered the habitable zone only a few hundred million years ago may well be habitable and even inhabited, but not have detectable biosignatures.

According to Pagano, he and his collaborators didn’t pick Tau Ceti “hoping, wanting, or thinking” it would be a good candidate to look for life, but for the idea that these might be truly alien new worlds.

Tau Ceti has a highly unusual composition with respect to its ratio of magnesium and silicon, which are two of the most important rock forming minerals on Earth. The ratio of magnesium to silicon in Tau Ceti is 1.78, which is about 70% more than our sun.

The astrophysicists looked at the data and asked, “What does this mean for the planets?”

Building on the strengths of ASU’s School of Earth and Space Exploration, which unites earth and space scientists in an effort to tackle research questions through a holistic approach, Shim was brought on board for his mineral expertise to provide insights into the possible nature of the planets themselves.

“With such a high magnesium and silicon ratio it is possible that the mineralogical make-up of planets around Tau Ceti could be significantly different from that of Earth. Tau Ceti’s planets could very well be dominated by the mineral olivine at shallow parts of the mantle and have lower mantles dominated by ferropericlase,” explains Shim.

Considering that ferropericlase is much less viscous, or resistant to flowing, hot, yet solid, mantle rock would flow more easily, possibly having profound effects on volcanism and tectonics at the planetary surface, processes which have a significant impact on the habitability of Earth.

“This is a reminder that geological processes are fundamental in understanding the habitability of planets,” Shim adds.

“Tau Ceti has been a popular destination for science fiction writers and everyone's imagination as somewhere there could possibly be life, but even though life around Tau Ceti may be unlikely, it should not be seen as a letdown, but should invigorate our minds to consider what exotic planets likely orbit the star, and the new and unusual planets that may exist in this vast universe,” says Pagano.

This work was supported by funding from the NASA Astrobiology Institute and NASA Nexus for Exoplanet System Science.

Written by Nikki Cassis

Source: School of Earth and Space Exploration (SESE) - Arizona State University (ASU)