Spitzer Telescope Spots a Ghoulish Gourd

This infrared image from NASA's Spitzer Space telescope shows a cloud of gas and dust carved out by a massive star. A drawing overlaid on the image reveals why researchers nicknamed this region the "Jack-o'-lantern Nebula." Credit: NASA/JPL-Caltech.  › Full image and caption

A carved-out cloud of gas and dust looks like a celestial jack-o'-lantern in this image from NASA's Spitzer Space Telescope.

A massive star - known as an O-type star and about 15 to 20 times heavier than the Sun - is likely responsible for sculpting this cosmic pumpkin. A recent study of the region suggests that the powerful outflow of radiation and particles from the star likely swept the surrounding dust and gas outward, creating deep gouges in this cloud, which is known as a nebula.

Spitzer, which detects infrared light, saw the star glowing like a candle at the center of a hollowed-out pumpkin. The study's authors have fittingly nicknamed the structure the "Jack-o'-lantern Nebula."

A plethora of objects in the universe emit infrared light, often as heat, so objects tend to radiate more infrared light the warmer they are.

Invisible to the human eye, three wavelengths of infrared light compose the multicolor image of the nebula seen here. Green and red represent light emitted primarily by dust radiating at different temperatures, though some stars radiate prominently in these wavelengths as well. The combination of green and red in the image creates yellow hues. Blue represents a wavelength mostly emitted, in this image, by stars and some very hot regions of the nebula, while white regions indicate where the objects are bright in all three colors. The O-type star appears as a white spot in the center of a red dust shell near the center of the scooped-out region.

A high-contrast version of the same image makes the red wavelength more pronounced. Together, the red and green wavelengths create an orange hue. The picture highlights contours in the dust as well as the densest regions of the nebula, which appear brightest.

The study that produced these observations appears in the Astrophysical Journal and examined a region in the outer region of the Milky Way galaxy. (Our Sun is halfway to the edge of the disk-shaped galaxy.) Researchers used infrared light to count the very young stars in different stages of early development in this region. They also counted protostars - infant stars still swaddled in the dense dust clouds in which they were born. When combined with tallies of adult stars in these regions, these data will help scientists determine whether the rates of star and planet formation in the galaxy's outer regions differ from the rates in middle and inner regions.

Scientists already know that conditions differ slightly in those outer areas. For example, interstellar clouds of gas and dust are colder and more sparsely distributed there than they are near the center of the galaxy (which may reduce the rate of star formation). Star-forming clouds in those outer areas also contain lower amounts of heavy chemical elements, including carbon, oxygen and other ingredients for life as we know it. Eventually, more studies like this one might also determine whether planets similar in composition to Earth are more or less common in the outer galaxy than in our local galactic neighborhood.

The data used to create this image was collected during Spitzer's "cold mission," which ran between 2004 and 2009.

For more information about Spitzer, go to: https://www.nasa.gov/mission_pages/spitzer/main/index.html

News Media Contact

Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov

Source: JPL-Caltech/News

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TESS reveals an improbable planet

Another red giant and another exoplanet, but until we know more, they all look more or less the same. 

Illustration: ESA.

Using asteroseismology, a team led by an Instituto de Astrofísica e Ciências do Espaço (IA) researcher, studied two red-giant stars known to host exoplanets, and for one of them found a seemingly improbable planet. Several researchers connected to SAC are co-authors.

Surprise: An exoplanet shouldn't have survived the expansion of it's red giant star, but still it is there.

Using asteroseismic data from NASA’s Transiting Exoplanet Survey Satellite (TESS), an international team, led by Instituto de Astrofísica e Ciências do Espaço (IA) researcher Tiago Campante, studied the red-giant stars HD 212771 and HD 203949. These are the first detections of oscillations in previously known exoplanet-host stars by TESS. The result was published 29 October 2019 in an article in The Astrophysical Journal.

Tiago Campante (IA & Faculdade de Ciências da Universidade do Porto - FCUP) explains that detecting these oscillations was only possible because: “TESS observations are precise enough to allow measuring the gentle pulsations at the surfaces of stars. These two fairly evolved stars also host planets, providing the ideal testbed for studies of the evolution of planetary systems.”

Having determined the physical properties of both stars, such as their mass, size and age, through asteroseismology, the authors then focused their attention on the evolutionary state of HD 203949. Their aim was to understand how its planet could have avoided engulfment, since  the envelope of the star would have expanded well beyond the current planetary orbit  during the red-giant phase of evolution.

Exoplanethunter TESS - now through half of it's nominal mission.

Illustration: NASA.

Co-author Vardan Adibekyan (IA & Universidade do Porto) comments: “This study is a perfect demonstration of how stellar and exoplanetary astrophysics are linked together. Stellar analysis seems to suggest that the star is too evolved to still host a planet at such a 'short' orbital distance, while from the exoplanet analysis we know that the planet is there! 

By performing extensive numerical simulations, the team thinks that star-planet tides might have brought the planet inward from its original, wider orbit, placing it where we see it today. Adibekyan adds: “The solution to this scientific dilemma is hidden in the 'simple fact' that stars and their planets not only form but also evolve together. In this particular case, the planet managed to avoid  engulfment.”

In the past decade, asteroseismology has had a significant impact on the study of solar-type and red-giant stars, which exhibit convection-driven, solar-like oscillations. These studies have advanced considerably with space-based observatories like CoRoT (CNES/ESA) and Kepler (NASA), and are set to continue in the next decade with TESS and PLATO (ESA).

Tiago Campante explains that: “IA's involvement in TESS is at the level of the scientific coordination within the TESS Asteroseismic Science Consortium (TASC). TASC is a large and unique scientific collaboration, bringing together all relevant research groups and individuals from around the world who are actively engaged in research in the field of asteroseismology. Following in the footsteps of its successful predecessor, the Kepler Asteroseismic Science Consortium (KASC), TASC is based on a collaborative and transparent working-group structure, aimed at facilitating open collaboration between scientists.”

The paper in The Astrophysical Journal has the title " TESS Asteroseismology of the known red-giant host stars HD 212771 and 203949"

Ole J. Knudsen

Source:  Stellar Astrophysics Centre

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ESO Telescope Reveals What Could be the Smallest Dwarf Planet Yet in the Solar System

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SPHERE image of Hygiea

 

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SPHERE images of Hygiea, Vesta and Ceres

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Videos

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ESOcast 211 Light: ESO Telescope Reveals What Could be the Smallest Dwarf Planet in the Solar System

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Location of Hygiea in the Solar System

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Impact simulation explaining the origin of Hygiea’s round shape

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Astronomers using ESO’s SPHERE instrument at the Very Large Telescope (VLT) have revealed that the asteroid Hygiea could be classified as a dwarf planet. The object is the fourth largest in the asteroid belt after Ceres, Vesta and Pallas. For the first time, astronomers have observed Hygiea in sufficiently high resolution to study its surface and determine its shape and size. They found that Hygiea is spherical, potentially taking the crown from Ceres as the smallest dwarf planet in the Solar System.

As an object in the main asteroid belt, Hygiea satisfies right away three of the four requirements to be classified as a dwarf planet: it orbits around the Sun, it is not a moon and, unlike a planet, it has not cleared the neighbourhood around its orbit. The final requirement is that it has enough mass for its own gravity to pull it into a roughly spherical shape. This is what VLT observations have now revealed about Hygiea.

“Thanks to the unique capability of the SPHERE instrument on the VLT, which is one of the most powerful imaging systems in the world, we could resolve Hygiea’s shape, which turns out to be nearly spherical,” says lead researcher Pierre Vernazza from the Laboratoire d'Astrophysique de Marseille in France. “Thanks to these images, Hygiea may be reclassified as a dwarf planet, so far the smallest in the Solar System.”

The team also used the SPHERE observations to constrain Hygiea’s size, putting its diameter at just over 430 km. Pluto, the most famous of dwarf planets, has a diameter close to 2400 km, while Ceres is close to 950 km in size.Surprisingly, the observations also revealed that Hygiea lacks the very large impact crater that scientists expected to see on its surface, the team report in the study published today in Nature Astronomy. Hygiea is the main member of one of the largest asteroid families, with close to 7000 members that all originated from the same parent body. Astronomers expected the event that led to the formation of this numerous family to have left a large, deep mark on Hygiea.

 “This result came as a real surprise as we were expecting the presence of a large impact basin, as is the case on Vesta,” says Vernazza. Although the astronomers observed Hygiea’s surface with a 95% coverage, they could only identify two unambiguous craters. “Neither of these two craters could have been caused by the impact that originated the Hygiea family of asteroids whose volume is comparable to that of a 100 km-sized object. They are too small,” explains study co-author Miroslav Brož of the Astronomical Institute of Charles University in Prague, Czech Republic.

The team decided to investigate further. Using numerical simulations, they deduced that Hygiea’s spherical shape and large family of asteroids are likely the result of a major head-on collision with a large projectile of diameter between 75 and 150 km. Their simulations show this violent impact, thought to have occurred about 2 billion years ago, completely shattered the parent body. Once the left-over pieces reassembled, they gave Hygiea its round shape and thousands of companion asteroids. “Such a collision between two large bodies in the asteroid belt is unique in the last 3–4 billion years,” says Pavel Ševeček, a PhD student at the Astronomical Institute of Charles University who also participated in the study.

Studying asteroids in detail has been possible thanks not only to advances in numerical computation, but also to more powerful telescopes. “Thanks to the VLT and the new generation adaptive-optics instrument SPHERE, we are now imaging main belt asteroids with unprecedented resolution, closing the gap between Earth-based and interplanetary mission observations,” Vernazza concludes.

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More Information

This research was presented in a paper to appear in Nature Astronomy on 28 October.

The team is composed of P. Vernazza (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France), L. Jorda (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France), P. Ševeček (Institute of Astronomy, Charles University, Prague, Czech Republic), M. Brož (Institute of Astronomy, Charles University, Prague, Czech Republic), M. Viikinkoski (Mathematics and Statistics, Tampere University, Tampere, Finland), J. Hanuš (Institute of Astronomy, Charles University, Prague, Czech Republic), B. Carry (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France), A. Drouard (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France), M. Ferrais (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), M. Marsset (Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, MA, USA), F. Marchis (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France, and SETI Institute, Carl Sagan Center, Mountain View, USA), M. Birlan (Observatoire de Paris, Paris, France), E. Podlewska-Gaca (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland, and Institute of Physics, University of Szczecin, Poland), E. Jehin (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), P. Bartczak (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland), G. Dudzinski (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland), J. Berthier (Observatoire de Paris, Paris, France), J. Castillo-Rogez (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), F. Cipriani (European Space Agency, ESTEC – Scientific Support Office, The Netherlands), F. Colas (Observatoire de Paris, Paris, France), F. DeMeo (Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, MA, USA), C. Dumas (TMT Observatory, Pasadena, USA), J. Durech (Institute of Astronomy, Charles University, Prague, Czech Republic), R. Fetick (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France and ONERA, The French Aerospace Lab, Chatillon Cedex, France), T. Fusco (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France and and ONERA, The French Aerospace Lab, Chatillon Cedex, France), J. Grice (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France and Open University, School of Physical Sciences, The Open University, Milton Keynes, UK), M. Kaasalainen (Mathematics and Statistics, Tampere University, Tampere, Finland), A. Kryszczynska (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland), P. Lamy (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France), H. Le Coroller (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France), A. Marciniak (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland), T. Michalowski (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland), P. Michel (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France), N. Rambaux (Observatoire de Paris, Paris, France), T. Santana-Ros (Departamento de Fı́sica, Universidad de Alicante, Alicante, Spain), P. Tanga (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France), F. Vachier (Observatoire de Paris, Paris, France), A. Vigan (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, France), O. Witasse (European Space Agency, ESTEC – Scientific Support Office, The Netherlands), B. Yang (European Southern Observatory, Santiago, Chile), M. Gillon (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgium), Z. Benkhaldoun (Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco), R. Szakats (Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budapest, Hungary), R. Hirsch (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland), R. Duffard (Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía S/N, Granada, Spain), A. Chapman (Buenos Aires, Argentina), J. L. Maestre (Observatorio de Albox, Almeria, Spain).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

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Links

• Research paper
• Supplementary material
• New SPHERE view of VESTA
• VLT’s SPHERE spies rocky worlds
• SPHERE maps the surface of Ceres
• Photos of the VLT

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Contacts

Pierre Vernazza
Laboratoire d’Astrophysique de Marseille
Marseille, France
Tel: +33 4 91 05 59 11
Email: pierre.vernazza@lam.fr

Miroslav Brož
Charles University
Prague, Czech Republic
Email: mira@sirrah.troja.mff.cuni.cz

Pavel Ševeček
Charles University
Prague, Czech Republic
Email: pavel.sevecek@gmail.com

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
Email: pio@eso.org

Souce: ESO/News

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Scientists at the Kavli Institute have identified hot gas around the most luminous quasar at an epoch when the universe was less than 4 billion years old.

Left panel: Residual visibilities showing the signal present only on very large scales. This indicates the presence of very extended hot gas. Right panel: Map of the quasar field showing the detection of a negative SZ 'bowl' (on smaller scales) to the southwest of the quasar. Hi-res image

Scientists at the Kavli Institute have identified hot gas around a galaxy which hosts one of the most luminous quasars in the Universe, seen at an epoch when the Universe was less than 4 billion years old (a redshift of 1.7). Quasars are supermassive black holes which are accreting matter at a high rate.

Models of galaxy evolution invoke negative feedback from quasars onto their host galaxies to explain the so-called 'quenching' of star formation in galaxies, which turns blue, star forming galaxies into red, passive ones. In one such feedback scenario, it is thought that the black hole at the centre of the galaxy injects thermal energy into the galaxy’s halo, reducing the accretion of fresh gas into the galaxy and eventually suppressing star formation (due to a lack of gas available inside the galaxy to form stars).

The newly-detected hot gas is distributed on very large scales (hundreds of kilo-parsecs) and can be distinguished from the galaxy's normal emission using interferometers such as the Atacama Large Millimetre Array (ALMA) which are sensitive to a large range of spatial scales.

The hot gas has a low density and is therefore difficult to detect using standard techniques. A second approach, using the so-called Sunyaev-Zeldovich effect, looks for imprints in the Cosmic Microwave Background (CMB) caused by the hot gas. The team found indications of these imprints in the CMB around HE0515-4414, which is the most luminous quasar at redshift 1.7 (when the universe was less than 4 billion years old).

Refining the observational setup of ALMA in forthcoming observations will allow astronomers to probe the very extended hot gas with higher sensitivity. With these measurements, we will be able to carry out detailed tests of the effectiveness of halo heating in quenching star formation inside galaxies, and test different models of galaxy evolution.

This investigation was led by Simcha Brownson, a PhD student at the Kavli Institute, and the results were published in this week's issue of Monthly Notices of the Royal Astronomical Society - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stz2945/5602606?guestAccessKey=a3ceea43-506b-4eeb-84f8-6e30ed8fda4f or https://arxiv.org/abs/1910.02088

Source: Kavli Institute for Cosmology, Cambridge (KICC)/News

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Chandra Spots a Mega-Cluster of Galaxies in the Making

Labeled image of Abell 1758 system

Credit: X-ray: NASA/CXC/SAO/G.Schellenberger et al.; Optical:SDSS 

Large JPEG (1.3 MB) - Tiff (32.9 MB) - More Images

A Tour of a Collision Between Four Galaxy Clusters in Abell 1758 -  More Animations

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Astronomers using data from NASA's Chandra X-ray Observatory and other telescopes have put together a detailed map of a rare collision between four galaxy clusters. Eventually all four clusters — each with a mass of at least several hundred trillion times that of the Sun — will merge to form one of the most massive objects in the universe.

Galaxy clusters are the largest structures in the cosmos that are held together by gravity. Clusters consist of hundreds or even thousands of galaxies embedded in hot gas, and contain an even larger amount of invisible dark matter. Sometimes two galaxy clusters collide, as in the case of the Bullet Cluster, and occasionally more than two will collide at the same time.

The new observations show a mega-structure being assembled in a system called Abell 1758, located about 3 billion light-years from Earth. It contains two pairs of colliding galaxy clusters that are heading toward one another. Scientists first recognized Abell 1758 as a quadruple galaxy cluster system in 2004 using data from Chandra and XMM-Newton, a satellite operated by the European Space Agency (ESA).

Each pair in the system contains two galaxy clusters that are well on their way to merging. In the northern (top) pair seen in the composite image, the centers of each cluster have already passed by each other once, about 300 to 400 million years ago, and will eventually swing back around. The southern pair at the bottom of the image has two clusters that are close to approaching each other for the first time.

X-rays from Chandra are shown as blue and white, depicting fainter and brighter diffuse emission, respectively. This new composite image also includes an optical image from the Sloan Digital Sky Survey. The Chandra data revealed for the first time a shock wave — similar to the sonic boom from a supersonic aircraft — in hot gas visible with Chandra in the northern pair's collision. From this shock wave, researchers estimate two clusters are moving about 2 million to 3 million miles per hour (3 million to 5 million kilometers per hour), relative to each other.

Chandra data also provide information about how elements heavier than helium, the "heavy elements," in galaxy clusters get mixed up and redistributed after the clusters collide and merge. Because this process depends on how far a merger has progressed, Abell 1758 offers a valuable case study, since the northern and the southern pairs of clusters are at different stages of merging.

In the southern pair, the heavy elements are most abundant in the centers of the two colliding clusters, showing that the original location of the elements has not been strongly impacted by the ongoing collision. By contrast, in the northern pair, where the collision and merger has progressed further, the location of the heavy elements has been strongly influenced by the collision. The highest abundances are found between the two cluster centers and to the left side of the cluster pair, while the lowest abundances are in the center of the cluster on the left side of the image.

Collisions between clusters affect their component galaxies as well as the hot gas that surrounds them. Data from the 6.5-meter MMT telescope in Arizona, obtained as part of the Arizona Cluster Redshift Survey, show that some galaxies are moving much faster than others, probably because they have been thrown away from the other galaxies in their cluster by gravitational forces imparted by the collision.

The team also used radio data from the Giant Metrewave Radio Telescope (GMRT), and X-ray data from ESA's XMM-Newton mission.

A paper describing these latest results by Gerrit Schellenberger, Larry David, Ewan O'Sullivan, Jan Vrtilek (all from Center for Astrophysics | Harvard & Smithsonian) and Christopher Haines (Universidad de Atacama, Chile) was published in the September 1st, 2019 issue of The Astrophysical Journal, and is available online.

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge, Massachusetts.

A Quick Look at a Collision Between Four Galaxy Clusters in Abell 1758

Source: NASA’s Chandra X-ray Observatory

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Fast Facts for Abell 1758

Scale: Image is about 16.7 arcmin (14 million light years) across.
Category: Groups & Clusters of Galaxies, Cosmology/Deep Fields/X-ray Background
Coordinates (J2000): RA 13h 32m 43.02s | Dec +50° 32´ 25.70"
Constellation: Canes Venatici
Observation Date: Aug 28, 2001
Observation Time: 56 hours 40 minutes (2 days 8 hours 40 minutes)
Obs. ID: 2213, 13997, 15538, 15540
Instrument: ACIS
References: Schellenberger G., et al, 2019, ApJ, 882, 59; arXiv:1907.10581
Color Code: X-ray: blue and white; Optical: yellow and pink
Distance Estimate: About 3.2 billion light years (z=0.28)

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First identification of a heavy element born from neutron star collision

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Artist’s impression of strontium emerging from a neutron star merger

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X-shooter spectra montage of kilonova in NGC 4993

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The galaxy NGC 4993 in the constellation of Hydra

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The sky around the galaxy NGC 4993

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Videos

PR Video eso1917a

ESOcast 210 Light: First identification of a heavy element born from neutron star collision

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Neutron star merger animation and elements formed in these events

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Animation of spectra of kilonova in NGC 4993

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For the first time, a freshly made heavy element, strontium, has been detected in space, in the aftermath of a merger of two neutron stars. This finding was observed by ESO’s X-shooter spectrograph on the Very Large Telescope (VLT) and is published today in Nature. The detection confirms that the heavier elements in the Universe can form in neutron star mergers, providing a missing piece of the puzzle of chemical element formation.

In 2017, following the detection of gravitational waves passing the Earth, ESO pointed its telescopes in Chile, including the VLT, to the source: a neutron star merger named GW170817. Astronomers suspected that, if heavier elements did form in neutron star collisions, signatures of those elements could be detected in kilonovae, the explosive aftermaths of these mergers. This is what a team of European researchers has now done, using data from the X-shooter instrument on ESO’s VLT.

Following the GW170817 merger, ESO’s fleet of telescopes began monitoring the emerging kilonova explosion over a wide range of wavelengths. X-shooter in particular took a series of spectra from the ultraviolet to the near infrared. Initial analysis of these spectra suggested the presence of heavy elements in the kilonova, but astronomers could not pinpoint individual elements until now. 

“By reanalysing the 2017 data from the merger, we have now identified the signature of one heavy element in this fireball, strontium, proving that the collision of neutron stars creates this element in the Universe,” says the study’s lead author Darach Watson from the University of Copenhagen in Denmark. On Earth, strontium is found naturally in the soil and is concentrated in certain minerals. Its salts are used to give fireworks a brilliant red colour. 

Astronomers have known the physical processes that create the elements since the 1950s. Over the following decades they have uncovered the cosmic sites of each of these major nuclear forges, except one. “This is the final stage of a decades-long chase to pin down the origin of the elements,” says Watson. “We know now that the processes that created the elements happened mostly in ordinary stars, in supernova explosions, or in the outer layers of old stars. But, until now, we did not know the location of the final, undiscovered process, known as rapid neutron capture, that created the heavier elements in the periodic table.”

Rapid neutron capture is a process in which an atomic nucleus captures neutrons quickly enough to allow very heavy elements to be created. Although many elements are produced in the cores of stars, creating elements heavier than iron, such as strontium, requires even hotter environments with lots of free neutrons. Rapid neutron capture only occurs naturally in extreme environments where atoms are bombarded by vast numbers of neutrons.

“This is the first time that we can directly associate newly created material formed via neutron capture with a neutron star merger, confirming that neutron stars are made of neutrons and tying the long-debated rapid neutron capture process to such mergers,” says Camilla Juul Hansen from the Max Planck Institute for Astronomy in Heidelberg, who played a major role in the study.

Scientists are only now starting to better understand neutron star mergers and kilonovae. Because of the limited understanding of these new phenomena and other complexities in the spectra that the VLT’s X-shooter took of the explosion, astronomers had not been able to identify individual elements until now.

“We actually came up with the idea that we might be seeing strontium quite quickly after the event. However, showing that this was demonstrably the case turned out to be very difficult. This difficulty was due to our highly incomplete knowledge of the spectral appearance of the heavier elements in the periodic table,” says University of Copenhagen researcher Jonatan Selsing, who was a key author on the paper. 

The GW170817 merger was the fifth detection of gravitational waves, made possible thanks to the NSF's Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US and the Virgo Interferometer in Italy. Located in the galaxy NGC 4993, the merger was the first, and so far the only, gravitational wave source to have its visible counterpart detected by telescopes on Earth. 

With the combined efforts of LIGO, Virgo and the VLT, we have the clearest understanding yet of the inner workings of neutron stars and their explosive mergers.

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More Information

This research was presented in a paper to appear in Nature on 24 October 2019.

The team is composed of D. Watson (Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), C. J. Hansen (Max Planck Institute for Astronomy, Heidelberg, Germany), J. Selsing (Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), A. Koch (Center for Astronomy of Heidelberg University, Germany), D. B. Malesani (DTU Space, National Space Institute, Technical University of Denmark, & Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), A. C. Andersen (Niels Bohr Institute, University of Copenhagen, Denmark), J. P. U. Fynbo (Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), A. Arcones (Institute of Nuclear Physics, Technical University of Darmstadt, Germany & GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany), A. Bauswein (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany & Heidelberg Institute for Theoretical Studies, Germany), S. Covino (Astronomical Observatory of Brera, INAF, Milan, Italy), A. Grado (Capodimonte Astronomical Observatory, INAF, Naples, Italy), K. E. Heintz (Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Reykjavík, Iceland & Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), L. Hunt (Arcetri Astrophysical Observatory, INAF, Florence, Italy), C. Kouveliotou (George Washington University, Physics Department, Washington DC, USA & Astronomy, Physics and Statistics Institute of Sciences), G. Leloudas (DTU Space, National Space Institute, Technical University of Denmark, & Niels Bohr Institute, University of Copenhagen, Denmark), A. Levan (Department of Physics, University of Warwick, UK), P. Mazzali (Astrophysics Research Institute, Liverpool John Moores University, UK & Max Planck Institute for Astrophysics, Garching, Germany), E. Pian (Astrophysics and Space Science Observatory of Bologna, INAF, Bologna, Italy).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

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Links

• Research paper 
• ESO Telescopes Observe First Light from Gravitational Wave Source
• Photos of the VLT

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Contacts

Darach Watson
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen
Copenhagen, Denmark
Cell: +45 24 80 38 25
Email: darach@nbi.ku.dk

Camilla J. Hansen
Max Planck Institute for Astronomy
Heidelberg, Germany
Tel: +49 6221 528-358
Email: hansen@mpia.de

Jonatan Selsing
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen
Copenhagen, Denmark
Cell: +45 61 71 43 46
Email: jselsing@nbi.ku.dk

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
Email: pio@eso.org

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A Monster Galaxy From the Dawn of the Universe Discovered by Accident

An artist’s impression of what a massive galaxy in the early universe might look like. The galaxy is undergoing an explosion of star formation, lighting up the gas surrounding the galaxy. Thick clouds of dust obscure most of the light, causing the galaxy to look dim and disorganized, very different from galaxies seen today. Credit: James Josephides/Swinburne Astronomy Productions, Christina Williams/University of Arizona, Ivo Labbe/Swinburne

The early universe is filled with monsters, a new study revealed. Researchers led by astronomer Christina Williams discovered a previously invisible galaxy, and perhaps a new galaxy population waiting to be discovered.

Astronomers accidentally discovered the footprints of a monster galaxy in the early universe that has never been seen before. Like a cosmic Yeti, the scientific community generally regarded these galaxies as folklore, given the lack of evidence of their existence, but astronomers in the United States and Australia managed to snap a picture of the beast for the first time.

Published today (October 22, 2019) in the Astrophysical Journal, the discovery provides new insights into the first growing steps of some of the biggest galaxies in the universe.

University of Arizona astronomer Christina Williams, lead author of the study, noticed a faint light blob in new sensitive observations using the Atacama Large Millimeter Array, or ALMA, a collection of 66 radio telescopes high in the Chilean mountains. Strangely enough, the shimmering seemed to be coming out of nowhere, like a ghostly footstep in a vast dark wilderness.

“It was very mysterious because the light seemed not to be linked to any known galaxy at all,” said Williams, a National Science Foundation postdoctoral fellow at the Steward Observatory. “When I saw this galaxy was invisible at any other wavelength, I got really excited because it meant that it was probably really far away and hidden by clouds of dust.”

The researchers estimate that the signal came from so far away that it took 12.5 billion years to reach Earth, therefore giving us a view of the universe in its infancy. They think the observed emission is caused by the warm glow of dust particles heated by stars forming deep inside a young galaxy. The giant clouds of dust conceal the light of the stars themselves, rendering the galaxy completely invisible.

Study co-author Ivo Labbé, of the Swinburne University of Technology, Melbourne, Australia, said: “We figured out that the galaxy is actually a massive monster galaxy with as many stars as our Milky Way, but brimming with activity, forming new stars at 100 times the rate of our own galaxy.”

The discovery may solve a long-standing question in astronomy, the authors said. Recent studies found that some of the biggest galaxies in the young universe grew up and came of age extremely quickly, a result that is not understood theoretically. Massive mature galaxies are seen when the universe was only a cosmic toddler at 10% of its current age. Even more puzzling is that these mature galaxies appear to come out of nowhere: astronomers never seem to catch them while they are forming.

Smaller galaxies have been seen in the early universe with the Hubble Space Telescope, but such creatures are not growing fast enough to solve the puzzle. Other monster galaxies have also been previously reported, but those sightings have been far too rare for a satisfying explanation.

“Our hidden monster galaxy has precisely the right ingredients to be that missing link,” Williams explains, “because they are probably a lot more common.”

An open question is exactly how many of them there are. The observations for the current study were made in a tiny part of the sky, less than 1/100th the disc of the full moon. Like the Yeti, finding footprints of the mythical creature in a tiny strip of wilderness would either be a sign of incredible luck or a sign that monsters are literally lurking everywhere.

Williams said researchers are eagerly awaiting the March 2021 scheduled launch of NASA’s James Webb Space Telescope to investigate these objects in more detail.

“JWST will be able to look through the dust veil so we can learn how big these galaxies really are and how fast they are growing,

But for now, the monsters are out there, shrouded in dust and a lot of mystery.

By University of Arizona 

Source: ScitechDaily/News/Space

Animation of a Massive, Active Galaxy Shrouded in Dust

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Reference:

“Discovery of a Dark, Massive, ALMA-only Galaxy at z ~ 5–6 in a Tiny 3 mm Survey” by Christina C. Williams, Ivo Labbe, Justin Spilker, Mauro Stefanon, Joel Leja, Katherine Whitaker, Rachel Bezanson, Desika Narayanan, Pascal Oesch and Benjamin Weiner, 22 October 2019, Astrophysical Journal.

DOI: 10.3847/1538-4357/ab44aa

The study was funded by the National Science Foundation.

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The Whole Picture of Distant Supercluster in Three Dimensions

Figure 1: The 3-D and 2-D maps of the number density of galaxies associated with the supercluster. In the 2-D map, the large-scale structures of galaxies located in the slice at about 7.3 billion years ago are shown. The white areas show the structures already known from previous studies, and the yellow areas show the structures newly discovered by this study. The structures marked by the dotted ellipses are to be confirmed by future works. The white vertical line in the figure corresponds to a distance of about 30 million light-years (i.e., 10 Mpc). (Credit: NAOJ)

Using the Subaru Telescope and Gemini-North Telescope, a team of astronomers has revealed that the supercluster CL1604, a distant supercluster located about 7.3 billion light-years away, is a large-scale 3-D structure extending over about 160 million light-years in the north-south direction. This is more than two times more extended than what was already known. Until now, we saw merely the “tip of the iceberg” of the supercluster. The wide-field capability of the Subaru Telescope enabled us to survey the whole of the supercluster and the Gemini-North Telescope played a critical role in confirming the structures. This is the outcome of the good synergy of the telescopes of the Maunakea observatories.

Galaxies are distributed inhomogeneously in the Universe. It is well-known that nearby galaxies are strongly influenced by their environment, e.g., whether they are located in dense areas called galaxy clusters or less dense areas called voids. However, how galaxies form and evolve along with the growth of the cosmic web structures is one of the hot topics of astronomy. A wide-field survey of the distant Universe allows us to witness what actually happened with galaxies in the early phase of structure formation in the Universe. Among the few superclusters currently known, one of the best targets for study is the supercluster CL1604. Based on previous studies, its extent is 80 million light-years and its era is 7.3 billion years ago.

The uniqueness of the data taken by Hyper Suprime-Cam (HSC) on the Subaru Telescope is the deep imaging data over a field wide enough to fully cover the known supercluster and the surrounding area. A team led by Masao Hayashi and Yusei Koyama from NAOJ estimated the distances of individual galaxies from the galaxy colors using a technique called “photometric redshift.” Then, the three dimensional picture of the large-scale structures appears, which consists of several galaxy clusters newly discovered in the north-south direction as well as the structures already known (Figure 1). 

Figure 2: The distribution of redshift (i.e., distance in the depth direction) of the galaxies confirmed by our spectroscopic observations. In each area, the histogram is color-coded by the distance of the galaxies. The same color for the histograms means that the galaxy clusters are located at the same distance in the depth direction irrespective of the location on the sky. (Credit: NAOJ)

Furthermore, the team used the Faint Object Camera and Spectrograph (FOCAS) on the Subaru Telescope and the Gemini Multi-Object Spectrograph (GMOS) on Gemini-North to confirm the precise distances of 137 galaxies associated with the galaxy clusters revealed by HSC (Figure 2). It is found that the supercluster is a complex large-scale structure not only over the vast projected area but also along the line-of-sight direction in 3D. The galaxies spread over the 160 million light-years seem to be independent due to the vast area, however, the spectroscopic observations tell us that the galaxies formed simultaneously and then evolve along with the growth of large-scale structures. 

Our Galaxy is a member of Local Group on the outskirts of Virgo Galaxy Cluster. A team led by an astronomer from the University of Hawaii recently revealed that the Virgo Cluster is a member of a more extended enormous large-scale structure named the Laniakea Supercluster. "The supercluster we discovered 7.3 billion years ago may grow to be a huge large-scale structure similar to Laniakea where we live" said Hayashi. 

These results were published in Publications of the Astronomical Society of Japan (Hayashi et al., "The whole picture of the large-scale structure of the CL1604 supercluster at z∼0.9"). A preprint is available here.

Links

• Gemini Helps Map Larger than Expected Structure of Ancient Supercluster (Press Release from Gemini Observatory) 

Source: Subaru Telescope

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The Clumpy and Lumpy Death of a Star

Tycho supernova remnant

Credit: X-ray: NASA/CXC/RIKEN & GSFC/T. Sato et al; Optical: DSS

 JPEG (530.4 kb)  -  Large JPEG (2.3 MB)  -  Tiff (47.3 MB)

A Tour of Tycho's Supernova Remnant - More Animations

Astronomers now know that Tycho's new star was not new at all. Rather it signaled the death of a star in a supernova, an explosion so bright that it can outshine the light from an entire galaxy. This particular supernova was a Type Ia, which occurs when a white dwarf star pulls material from, or merges with, a nearby companion star until a violent explosion is triggered. The white dwarf star is obliterated, sending its debris hurtling into space.

As with many supernova remnants, the Tycho supernova remnant, as it's known today (or "Tycho," for short), glows brightly in X-ray light because shock waves — similar to sonic booms from supersonic aircraft — generated by the stellar explosion heat the stellar debris up to millions of degrees. In its two decades of operation, NASA's Chandra X-ray Observatory has captured unparalleled X-ray images of many supernova remnants. 

Chandra reveals an intriguing pattern of bright clumps and fainter areas in Tycho. What caused this thicket of knots in the aftermath of this explosion? Did the explosion itself cause this clumpiness, or was it something that happened afterward? 

This latest image of Tycho from Chandra is providing clues. To emphasize the clumps in the image and the three-dimensional nature of Tycho, scientists selected two narrow ranges of X-ray energies to isolate material (silicon, colored red) moving away from Earth, and moving towards us (also silicon, colored blue). The other colors in the image (yellow, green, blue-green, orange and purple) show a broad range of different energies and elements, and a mixture of directions of motion. In this new composite image, Chandra's X-ray data have been combined with an optical image of the stars in the same field of view from the Digitized Sky Survey.

By comparing the Chandra image of Tycho to two different computer simulations, researchers were able to test their ideas against actual data. One of the simulations began with clumpy debris from the explosion. The other started with smooth debris from the explosion and then the clumpiness appeared afterwards as the supernova remnant evolved and tiny irregularities were magnified.

A statistical analysis using a technique that is sensitive to the number and size of clumps and holes in images was then used. Comparing results for the Chandra and simulated images, scientists found that the Tycho supernova remnant strongly resembles a scenario in which the clumps came from the explosion itself. While scientists are not sure how, one possibility is that star's explosion had multiple ignition points, like dynamite sticks being set off simultaneously in different locations. 

Understanding the details of how these stars explode is important because it may improve the reliability of the use of Type Ia supernovas "standard candles" — that is, objects with known inherent brightness, which scientists can use to determine their distance. This is very important for studying the expansion of the universe. These supernovae also sprinkle elements such as iron and silicon, that are essential for life as we know it, into the next generation of stars and planets. 

A paper describing these results appeared in the July 10th, 2019 issue of The Astrophysical Journal and is available online. The authors are Toshiki Sato (RIKEN in Saitama, Japan, and NASA's Goddard Space Flight Center in Greenbelt, Maryland), John (Jack) Hughes (Rutgers University in Piscataway, New Jersey), Brian Williams, (NASA's Goddard Space Flight Center), and Mikio Morii (The Institute of Statistical Mathematics in Tokyo, Japan).

3D printed model of Tycho's Supernova Remnant

Credit: RIKEN/G. Ferrand, et al & NASA/CXC/SAO/A. Jubett, N. Wolk & K. Arcand

Another team of astronomers, led by Gilles Ferrand of RIKEN in Saitama, Japan, has constructed their own three-dimensional computer models of a Type Ia supernova remnant as it changes with time. Their work shows that initial asymmetries in the simulated supernova explosion are required so that the model of the ensuing supernova remnant closely resembles the Chandra image of Tycho, at a similar age. This conclusion is similar to that made by Sato and his team. 

A paper describing the results by Ferrand and co-authors appeared in the June 1st, 2019 issue of The Astrophysical Journal and is available online. 

NASA's Marshall Space Flight Center manages the  Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge, Massachusetts.

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Fast Facts for Tycho's Supernova Remnant:

Scale: Image is about 12 arcmin (45 light years) across.
Category: Supernovas & Supernova Remnants
Coordinates (J2000):  RA 00h 25m 17s | Dec +64° 08' 37"
Constellation:  Cassiopeia
Observation Date: 14 pointings between Oct 1, 2001 & April 22, 2016
Observation Time: 336 hours 2 minutes (14 days 0 hours 2 minutes)
Obs. ID: 115, 3837, 7539, 8551, 10093-10097; 10902-10904; 10906, 15998
Instrument: ACIS
Also Known As:  G120.1+01.4, SN 1572
References: Sato, T. et al. 2019, ApJ, 879, 64; arXiv:1903.00764
Color Code: X-ray Broadband: Red: 0.3-1.2 keV, Yellow: 1.2-1.6 keV, Cyan: 1.6-2.26 keV, Navy: 2.2-4.1 keV, Purple: 4.4-6.1 keV; X-ray Motion Shift Orange: 1.7666-1.7812 keV, Blue: 1.9564-1.971 keV; Optical: Red, Blue
Distance Estimate:  About 13,000 light years

Source: NASA’s Chandra X-ray Observatory

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Hubble Observes New Interstellar Visitor

PR Image heic1918a

Comet 2I/Borisov 

PR Image heic1918a

Comet 2I/Borisov

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Video

PR Video heic1918a

Animation of Comet 2I/Borisov

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On 12 October 2019, the NASA/ESA Hubble Space Telescope provided astronomers with their best look yet at an interstellar visitor — Comet 2I/Borisov — which is believed to have arrived here from another planetary system elsewhere in our galaxy.

This observation is the sharpest  view ever of the interstellar comet. Hubble reveals a central concentration of dust around the solid icy nucleus.

Comet 2I/Borisov is only the second such interstellar object known to have passed through our Solar System. In 2017, the first identified interstellar visitor, an object dubbed ‘Oumuamua, swung within 38 million kilometres of the Sun before racing out of the Solar System.

“Whereas ‘Oumuamua looked like a bare rock, Borisov is really active, more like a normal comet. It’s a puzzle why these two are so different,” explained David Jewitt of UCLA, leader of the Hubble team who observed the comet.

As the second interstellar object found to enter our Solar System, the comet provides various invaluable insights. For example, it offers clues to the chemical composition, structure, and dust characteristics of a planetary building block presumably forged in an alien star system a long time ago and far away.

“Because another star system could be quite different from our own, the comet could have experienced  significant changes during its long interstellar journey. Yet its properties are very similar to those of the Solar System’s building blocks, and this is very remarkable,” said Amaya Moro-Martin of the Space Telescope Science Institute in Baltimore, Maryland.

Hubble photographed the comet at a distance of approximately 420 million kilometres from Earth [1]. The comet is travelling toward the Sun and will make its closest approach to the Sun on 7 December, when it will be twice as far from the Sun as Earth. It is also following a hyperbolic path around the Sun, and is currently blazing along at the extraordinary velocity of over 150 000 kilometres per hour. 

By the middle of 2020, the comet will be on its way back into interstellar space where it will drift for millions of years before maybe one day approaching another star system.

Crimean amateur astronomer Gennady Borisov first discovered the comet on 30 August 2019. After a week of observations by amateur and professional astronomers all over the world, the International Astronomical Union’s Minor Planet Center computed an orbit for the comet which showed that it came from interstellar space. Until now, all catalogued comets have come either from a ring of icy debris at the periphery of our Solar System, called the Kuiper belt, or from the Oort cloud, a shell of icy objects which is thought to be in the outermost regions of our Solar System, with its innermost edge at about 2000 times the distance between the Earth and the Sun.

2I/Borisov and ‘Oumuamua are only the beginning of the discoveries of interstellar objects paying a brief visit to our Solar System. There may be thousands of such interstellar objects here at any given time; most, however, are too faint to be detected with present-day telescopes.

Observations by Hubble and other telescopes have shown that rings and shells of icy debris encircle young stars where planet formation is underway. A gravitational interaction between these comet-like objects and other massive bodies could hurtle them deep into space where they go adrift among the stars.

Future Hubble observations of 2I/Borisov are planned through January 2020, with more being proposed.

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Notes

[1] This observation was made as part of DD Program #16009.

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More Information

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

Image credit: NASA, ESA, D. Jewitt (UCLA)

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Links

• Images of Hubble 
• Hubblesite release

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Contact

David Jewitt
UCLA, Los Angeles, California
USA
Email: djewitt@gmail.com

Stuart Wolpert
UCLA, Los Angeles, California
USA
Email: swolpert@stratcomm.ucla.edu

Bethany Downer
ESA/Hubble, Public Information Officer
Garching, Germany
Email: bethany.downer@partner.eso.org

Source: ESA/HUBBL/News

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DARKSuper Spirals Spin Super Fast

Mosaic of Super Spirals 
Credits: Top row: NASA , ESA , P. Ogle and J. DePasquale (STScI )
Bottom row: SDSS, P. Ogle and J. DePasquale (STScI )

 Read News Release

When it comes to galaxies, how fast is fast? The Milky Way, an average spiral galaxy, spins at a speed of 130 miles per second (210 km/sec) in our Sun’s neighborhood. New research has found that the most massive spiral galaxies spin faster than expected. These “super spirals,” the largest of which weigh about 20 times more than our Milky Way, spin at a rate of up to 350 miles per second (570 km/sec).

Super spirals are exceptional in almost every way. In addition to being much more massive than the Milky Way, they’re also brighter and larger in physical size. The largest span 450,000 light-years compared to the Milky Way’s 100,000-light-year diameter. Only about 100 super spirals are known to date. Super spirals were discovered as an important new class of galaxies while studying data from the Sloan Digital Sky Survey (SDSS) as well as the NASA/IPAC Extragalactic Database (NED).

“Super spirals are extreme by many measures,” says Patrick Ogle of the Space Telescope Science Institute in Baltimore, Maryland. “They break the records for rotation speeds.”

Ogle is first author of a paper that was published October 10, 2019 in the Astrophysical Journal Letters . The paper presents new data on the rotation rates of super spirals collected with the Southern African Large Telescope (SALT), the largest single optical telescope in the southern hemisphere. Additional data were obtained using the 5-meter Hale telescope of the Palomar Observatory, operated by the California Institute of Technology. Data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission was crucial for measuring the galaxy masses in stars and star formation rates.

Referring to the new study, Tom Jarrett of the University of Cape Town, South Africa says, “This work beautifully illustrates the powerful synergy between optical and infrared observations of galaxies, revealing stellar motions with SDSS and SALT spectroscopy, and other stellar properties — notably the stellar mass or ‘backbone’ of the host galaxies — through the WISE mid-infrared imaging."

Theory suggests that super spirals spin rapidly because they are located within incredibly large clouds, or halos, of dark matter. Dark matter has been linked to galaxy rotation for decades. Astronomer Vera Rubin pioneered work on galaxy rotation rates, showing that spiral galaxies rotate faster than if their gravity were solely due to the constituent stars and gas. An additional, invisible substance known as dark matter must influence galaxy rotation. A spiral galaxy of a given mass in stars is expected to rotate at a certain speed. Ogle’s team finds that super spirals significantly exceed the expected rotation rate.

Super spirals also reside in larger than average dark matter halos. The most massive halo that Ogle measured contains enough dark matter to weigh at least 40 trillion times as much as our Sun. That amount of dark matter would normally contain a group of galaxies rather than a single galaxy.

“It appears that the spin of a galaxy is set by the mass of its dark matter halo,” Ogle explains.

The fact that super spirals break the usual relationship between galaxy mass in stars and rotation rate is a new piece of evidence against an alternative theory of gravity known as Modified Newtonian Dynamics, or MOND. MOND proposes that on the largest scales like galaxies and galaxy clusters, gravity is slightly stronger than would be predicted by Newton or Einstein. This would cause the outer regions of a spiral galaxy, for example, to spin faster than otherwise expected based on its mass in stars. MOND is designed to reproduce the standard relationship in spiral rotation rates, therefore it cannot explain outliers like super spirals. The super spiral observations suggest no non-Newtonian dynamics is required.

Despite being the most massive spiral galaxies in the universe, super spirals are actually underweight in stars compared to what would be expected for the amount of dark matter they contain. This suggests that the sheer amount of dark matter inhibits star formation. There are two possible causes: 1) Any additional gas that is pulled into the galaxy crashes together and heats up, preventing it from cooling down and forming stars, or 2) The fast spin of the galaxy makes it harder for gas clouds to collapse against the influence of centrifugal force.

“This is the first time we’ve found spiral galaxies that are as big as they can ever get,” Ogle says.

Despite these disruptive influences, super spirals are still able to form stars. Although the largest elliptical galaxies formed all or most of their stars more than 10 billion years ago, super spirals are still forming stars today. They convert about 30 times the mass of the Sun into stars every year, which is normal for a galaxy of that size. By comparison, our Milky Way forms about one solar mass of stars per year.

Ogle and his team have proposed additional observations to help answer key questions about super spirals, including observations designed to better study the motion of gas and stars within their disks. After its 2021 launch, NASA’s James Webb Space Telescope could study super spirals at greater distances and correspondingly younger ages to learn how they evolve over time. And NASA’s WFIRST mission may help locate more super spirals, which are exceedingly rare, thanks to its large field of view.

The Space Telescope Science Institute is expanding the frontiers of space astronomy by hosting the science operations center of the Hubble Space Telescope, the science and operations center for the James Webb Space Telescope, and the science operations center for the future Wide Field Infrared Survey Telescope (WFIRST). STScI also houses the Mikulski Archive for Space Telescopes (MAST) which is a NASA-funded project to support and provide to the astronomical community a variety of astronomical data archives, and is the data repository for the Hubble, Webb, Kepler, K2, TESS missions and more.

Source: HubbleSite/News

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