From Pennsylvania State University: “Stellar winds, the source material for the universe, are clumpy”

From Pennsylvania State University

24 January 2019

Pragati Pradhan
pup69@psu.edu
(814) 865-6834

Sam Sholtis (PIO)
samsholtis@psu.edu
(814) 865-1390

Illustration of a high-mass X-ray binary system made up of a compact, incredibly dense neutron star paired with a massive normal supergiant star. New data from NASAs Chandra X-ray Observatory shows that the neutron star in the high-mass X-ray binary, OAO 1657-415, passed through a dense patch of stellar wind from its companion star, demonstrating the clumpy nature of stellar winds. Credit: NASA/CXC/M.Weiss

NASA/Chandra X-ray Telescope

Data recorded by NASA’s Chandra X-ray Observatory of a neutron star as it passed through a dense patch of stellar wind emanating from its massive companion star provide valuable insight about the structure and composition of stellar winds and about the environment of the neutron star itself. A paper describing the research, led by Penn State astronomers, appears January 15, 2019, in the journal, Monthly Notices of the Royal Astronomical Society.

“Stellar winds are the fast-flowing material—composed of protons, electrons, and metal atoms—ejected from stars,” said Pragati Pradhan, a postdoctoral researcher in astronomy and astrophysics at Penn State and the lead author of the paper. “This material enriches the star’s surroundings with metals, kinetic energy, and ionizing radiation. It is the source material for star formation. Until the last decade, it was thought that stellar winds were homogenous, but these Chandra data provide direct evidence that stellar winds are populated with dense clumps.”

The neutron star observed is part of a high-mass X-ray binary system—the compact, incredibly dense neutron star paired with a massive ‘normal’ supergiant star. Neutron stars in binary systems produce X-rays when material from the companion star falls toward the neutron star and is accelerated to high velocities. As a result of this acceleration, X-rays are produced that can inturn interact with the materials of the stellar wind to produce secondary X-rays of signature energies at various distances from the neutron star. Neutral—uncharged—iron atoms, for example, produce fluorescence X-rays with energies of 6.4 kilo-electron volts (keV), roughly 3000 times the energy of visible light. Astronomers use spectrometers, like the instrument on Chandra, to capture these X-rays and separate them based on their energy to learn about the compositions of stars.

“Neutral iron atoms are a more common component of stars so we usually see a large peak at 6.4 keV in the data from our spectrometers when looking at X-rays from most neutron stars in a high-mass X-ray binary system,” said Pradhan. “When we looked at X-ray data from the high-mass X-ray binary system known as OAO 1657-415 we saw that this peak at 6.4 keV had an unusual feature. The peak had a broad extension down to 6.3 keV. This extension is referred to as a ‘Compton shoulder’ and indicates that the X-rays from neutral iron are being back scattered by dense matter surrounding the star. This is only the second high-mass X-ray binary system where such a feature has been detected.”

The researchers also used the Chandra’s state-of-the-art engineering to identify a lower limit on the distance from the neutron star that the X-rays from neutral iron are formed. Their spectral analysis showed that neutral iron is ionized at least 2.5 light-seconds, a distance of approximately 750 million meters or nearly 500,000 miles, from the neutron star to produce X-rays.

“In this work, we see a dimming of the X-rays from the neutron star and a prominent line from neutral iron in the X-ray spectrum—two signatures supporting the clumpy nature of stellar winds,” said Pradhan. “Furthermore, the detection of Compton shoulder has also allowed us to map the environment around this neutron star. We expect to be able to improve our understanding of these phenomenon with the upcoming launch of spacecrafts like Lynx and Athena, which will have improved X-ray spectral resolution.”

For Pradhan’s post-doctoral work at Penn State under the supervision of Professor of Astronomy and Astrophysics David Burrows, Associate Research Professor of Astronomy and Astrophysics Jamie Kennea, and Research Professor of Astronomy and Astrophysics Abe Falcone, she is majorly involved in writing algorithms for on-board detection of X-rays from transient astronomical events such as those seen from these high-mass X-ray binary systems for instruments that will be on the Athena spacecraft.

Pradhan and her team also have a follow-up campaign looking at the same high-mass X-ray binary with another NASA satellite—NuSTAR, which will cover a broader spectrum of X-rays from this source ranging in energies from ~ 3 to 70 keV—in May 2019.

NASA NuSTAR X-ray telescope

“We are excited about the upcoming NuSTAR observation too,” said Pradhan. “Such observations in hard X-rays will add another dimension to our understanding of the physics of this system and we will have an opportunity to estimate the magnetic field of the neutron star in OAO 1657-415, which is likely a million times stronger than strongest magnetic field on Earth.”

In additions to Pradhan, the research team for this paper includes Gayathri Raman and Pradhan’s Ph.D. supervisor Biswajit Paul at the Raman Research Institute in Bangalore, India.

See the full article here .

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From NASA NuSTAR: “Holy Cow! Mysterious Blast Studied with NASA Telescopes”

From NASA NuSTAR

Jan. 10, 2019

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

By Jeanette Kazmierczak
jeanette.a.kazmierczak@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

AT2018cow erupted in or near a galaxy known as CGCG 137-068, which is located about 200 million light-years away in the constellation Hercules. This zoomed-in image shows the location of the “Cow” in the galaxy. Credits: Sloan Digital Sky Survey

A brief and unusual flash spotted in the night sky on June 16, 2018, puzzled astronomers and astrophysicists across the globe. The event — called AT2018cow and nicknamed “the Cow” after the coincidental final letters in its official name — is unlike any celestial outburst ever seen before, prompting multiple theories about its source.

Over three days, the Cow produced a sudden explosion of light at least 10 times brighter than a typical supernova, and then it faded over the next few months. This unusual event occurred inside or near a star-forming galaxy known as CGCG 137-068, located about 200 million light-years away in the constellation Hercules. The Cow was first observed by the NASA-funded Asteroid Terrestrial-impact Last Alert System telescope in Hawaii.

ATLAS telescope, First Asteroid Terrestrial-impact Last Alert system (ATLAS) fully operational 8/15/15 Haleakala , Hawaii, USA, Altitude 4,205 m (13,796 ft)

So exactly what is the Cow? Using data from multiple NASA missions, including the Neil Gehrels Swift Observatory and the Nuclear Spectroscopic Telescope Array (NuSTAR), two groups are publishing papers that provide possible explanations for the Cow’s origins.

NASA Neil Gehrels Swift Observatory

One paper argues that the Cow is a monster black hole shredding a passing star. The second paper hypothesizes that it is a supernova — a stellar explosion — that gave birth to a black hole or a neutron star. [No links to journals or papers provided.]

Researchers from both teams shared their interpretations at a panel discussion on Thursday, Jan. 10, at the 233rd American Astronomical Society meeting in Seattle.

See the full article here .

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NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA’s Jet Propulsion Laboratory, also in Pasadena, for NASA’s Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley ; Columbia University, New York; NASA’s Goddard Space Flight Center, Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; ATK Aerospace Systems, Goleta, Calif., and with support from the Italian Space Agency (ASI) Science Data Center.

NuSTAR’s mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission’s outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA’s Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

From NASA NuSTAR: “Holy Cow! Mysterious Blast Studied with NASA Telescopes”

From NASA NuSTAR

Jan. 10, 2019 [Just found this.]

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

By Jeanette Kazmierczak
jeanette.a.kazmierczak@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

AT2018cow erupted in or near a galaxy known as CGCG 137-068, which is located about 200 million light-years away in the constellation Hercules. This zoomed-in image shows the location of the “Cow” in the galaxy. Credits: Sloan Digital Sky Survey

A brief and unusual flash spotted in the night sky on June 16, 2018, puzzled astronomers and astrophysicists across the globe. The event — called AT2018cow and nicknamed “the Cow” after the coincidental final letters in its official name — is unlike any celestial outburst ever seen before, prompting multiple theories about its source.

Over three days, the Cow produced a sudden explosion of light at least 10 times brighter than a typical supernova, and then it faded over the next few months. This unusual event occurred inside or near a star-forming galaxy known as CGCG 137-068, located about 200 million light-years away in the constellation Hercules. The Cow was first observed by the NASA-funded Asteroid Terrestrial-impact Last Alert System telescope in Hawaii.

ATLAS telescope, First Asteroid Terrestrial-impact Last Alert system (ATLAS) fully operational 8/15/15 Haleakala , Hawaii, USA, Altitude 4,205 m (13,796 ft)

So exactly what is the Cow? Using data from multiple NASA missions, including the Neil Gehrels Swift Observatory and the Nuclear Spectroscopic Telescope Array (NuSTAR), two groups are publishing papers that provide possible explanations for the Cow’s origins.

NASA Neil Gehrels Swift Observatory

One paper argues that the Cow is a monster black hole shredding a passing star. The second paper hypothesizes that it is a supernova — a stellar explosion — that gave birth to a black hole or a neutron star.

Researchers from both teams shared their interpretations at a panel discussion on Thursday, Jan. 10, at the 233rd American Astronomical Society meeting in Seattle.

Watch what scientists think happens when a black hole tears apart a hot, dense white dwarf star. A team working with observations from NASA’s Neil Gehrels Swift Observatory suggests this process explains a mysterious outburst known as AT2018cow, or “the Cow.” Credits: NASA’s Goddard Space Flight Center

A Black Hole Shredding a Compact Star?

One potential explanation of the Cow is that a star has been ripped apart in what astronomers call a “tidal disruption event.” Just as the Moon’s gravity causes Earth’s oceans to bulge, creating tides, a black hole has a similar but more powerful effect on an approaching star, ultimately breaking it apart into a stream of gas. The tail of the gas stream is flung out of the system, but the leading edge swings back around the black hole, collides with itself and creates an elliptical cloud of material. According to one research team using data spanning from infrared radiation to gamma rays from Swift and other observatories, this transformation best explains the Cow’s behavior.

AT2018cow erupted in or near a galaxy known as CGCG 137-068, which is located about 200 million light-years away from Earth in the constellation Hercules. The yellow cross shows the location of this puzzling outburst. Credits: Sloan Digital Sky Survey

“We’ve never seen anything exactly like the Cow, which is very exciting,” said Amy Lien, an assistant research scientist at the University of Maryland, Baltimore County and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We think a tidal disruption created the quick, really unusual burst of light at the beginning of the event and best explains Swift’s multiwavelength observations as it faded over the next few months.”

Lien and her colleagues think the shredded star was a white dwarf — a hot, roughly Earth-sized stellar remnant marking the final state of stars like our Sun. They also calculated that the black hole’s mass ranges from 100,000 to 1 million times the Sun’s, almost as large as the central black hole of its host galaxy. It’s unusual to see black holes of this scale outside the center of a galaxy, but it’s possible the Cow occurred in a nearby satellite galaxy or a globular star cluster whose older stellar populations could have a higher proportion of white dwarfs than average galaxies.

A paper describing the findings, co-authored by Lien, appeared in the journal Monthly Notices of the Royal Astronomical Society.

“The Cow produced a large cloud of debris in a very short time,” said lead author Paul Kuin, an astrophysicist at University College London (UCL). “Shredding a bigger star to produce a cloud like this would take a bigger black hole, result in a slower brightness increase and take longer for the debris to be consumed.”

Or a New View of a Supernova?

A different team of scientists was able to gather data on the Cow over an even broader range of wavelengths, spanning from radio waves to gamma rays. Based on those observations, the team suggests that a supernova could be the source of the Cow. When a massive star dies, it explodes as a supernova and leaves behind either a black hole or an incredibly dense object called a neutron star. The Cow could represent the birth of one of these stellar remnants.

Astronomers using ground-based observatories caught the progression of a cosmic event nicknamed “the Cow,” as seen in these three images. Left: The Sloan Digital Sky Survey in New Mexico observed the host galaxy Z 137-068 in 2003, with the Cow nowhere in sight. (The green circle indicates the location where the Cow eventually appeared). Center: The Liverpool Telescope in Spain’s Canary Islands saw the Cow very close to the event’s peak brightness on June 20, 2018, when it was much brighter than the host galaxy. Right: The William Herschel Telescope, also in the Canary Islands, took a high-resolution image of the Cow nearly a month after it reached peak brightness, as it faded and the host galaxy came back into view.
Credits: Daniel Perley, Liverpool John Moores University

SDSS 2.5 meter Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

2-metre Liverpool Telescope at La Palma in the Canary Islands, Altitude 2,363 m (7,753 ft)

Liverpool Telescope at the Observatorio del Roque de los Muchachos, altitude 2,363 m (7,753 ft)

ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

“We saw features in the Cow that we have never seen before in a transient, or rapidly changing, object,” said Raffaella Margutti, an astrophysicist at Northwestern University in Evanston, Illinois, and lead author of a study about the Cow to be published in The Astrophysical Journal. “Our team used high-energy X-ray data to show that the Cow has characteristics similar to a compact body like a black hole or neutron star consuming material. But based on what we saw in other wavelengths, we think this was a special case and that we may have observed — for the first time — the creation of a compact body in real time.”

Margutti’s team analyzed data from multiple observatories, including NASA’s NuSTAR, ESA’s (the European Space Agency’s) XMM-Newton and INTEGRAL satellites, and the National Science Foundation’s Very Large Array.

ESA/XMM Newton

ESA/Integral

NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

The team proposes that the bright optical and ultraviolet flash from the Cow signaled a supernova and that the X-ray emissions that followed shortly after the outburst arose from gas radiating energy as it fell onto a compact object.

Typically, a supernova’s expanding debris cloud blocks any light from the compact object at the center of the blast. Because of the X-ray emissions, Margutti and her colleagues suggest the original star in this scenario may have been relatively low in mass, producing a comparatively thinner debris cloud through which X-rays from the central source could escape.

“If we’re seeing the birth of a compact object in real time, this could be the start of a new chapter in our understanding of stellar evolution,” said Brian Grefenstette, a NuSTAR instrument scientist at Caltech and a co-author of Margutti’s paper. “We looked at this object with many different observatories, and of course the more windows you open onto an object, the more you can learn about it. But, as we’re seeing with the Cow, that doesn’t necessarily mean the solution will be simple.”

See the full article here .

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NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA’s Jet Propulsion Laboratory, also in Pasadena, for NASA’s Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley ; Columbia University, New York; NASA’s Goddard Space Flight Center, Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; ATK Aerospace Systems, Goleta, Calif., and with support from the Italian Space Agency (ASI) Science Data Center.

NuSTAR’s mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission’s outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA’s Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

From European Space Agency: “Team of telescopes finds X-ray engine inside mysterious supernova”

From European Space Agency

10 January 2019

Raffaella Margutti
Department of Physics and Astronomy
Northwestern University
Evanston, IL, USA
Email: raffaella.margutti@northwestern.edu

Indrek Vurm
Tartu Observatory
University of Tartu, Estonia
Email: indrek.vurm@ut.ee

Volodymyr Savchenko
Department of Astronomy
University of Geneva, Switzerland
Email: Volodymyr.Savchenko@unige.ch

Carlo Ferrigno
Department of Astronomy
University of Geneva, Switzerland
Email: Carlo.Ferrigno@unige.ch

Giulia Migliori
INAF–Institute of Radioastronomy
University of Bologna, Italy
Email: g.migliori@ira.inaf.it

Erik Kuulkers
ESA Integral Project Scientist
European Space Agency
Email: ekuulker@sciops.esa.int

Norbert Schartel
ESA XMM-Newton Project Scientist
European Space Agency
Email: norbert.schartel@sciops.esa.int

Markus Bauer








ESA Science Communication Officer









Tel: +31 71 565 6799









Mob: +31 61 594 3 954









Email: markus.bauer@esa.int

An image of supernova explosion AT2018cow and its host galaxy, CGCG 137-068, which is located some 200 million light years away. The image was obtained on 17 August 2018 using the DEep Imaging and Multi-Object Spectrograph (DEIMOS) on the W. M. Keck Observatory in Hawaii.

Keck/DEIMOS on Keck 2

Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level, showing also NASA’s IRTF and NAOJ Subaru

Credit: R. Margutti/W. M. Keck Observatory

The supernova was first spotted on 16 June 2018 with the ATLAS telescope, also in Hawaii. Further observations performed with a large team of telescopes – including ESA’s high-energy space telescopes Integral and XMM-Newton – revealed a source of powerful X-rays at the centre of this unprecedentedly bright and rapidly evolving stellar explosion, suggesting that it could either be a nascent black hole or neutron star with a powerful magnetic field, sucking in the surrounding material. Credit: R. Margutti/W. M. Keck Observatory

ESA’s high-energy space telescopes Integral and XMM-Newton have helped to find a source of powerful X-rays at the centre of an unprecedentedly bright and rapidly evolving stellar explosion that suddenly appeared in the sky earlier this year.

ESA/XMM Newton

ESA/Integral

The ATLAS telescope in Hawaii first spotted the phenomenon, since then named AT2018cow, on 16 June.

ATLAS is an asteroid impact early warning system of two telescopes being developed by the University of Hawaii and funded by NASA

ATLAS telescope, First Asteroid Terrestrial-impact Last Alert system (ATLAS) fully operational 8/15/15 Haleakala , Hawaii, USA, Altitude 4,205 m (13,796 ft)

They soon realised this was something completely new. In only two days the object exceeded the brightness of any previously observed supernova – a powerful explosion of an aging massive star that expels most of its material into the surrounding space, sweeping up the interstellar dust and gases in its vicinity.

A new paper, accepted for publication in The Astrophysical Journal, presents the observations from the first 100 days of the object’s existence, covering the entire electromagnetic spectrum of the explosion from radio waves to gamma rays.

The analysis, which includes observations from ESA’s Integral and XMM-Newton, as well as NASA’s NuSTAR and Swift space telescopes, found a source of high-energy X-rays sitting deep inside the explosion.

NASA NuSTAR X-ray telescope

NASA Neil Gehrels Swift Observatory

The behaviour of this source, or engine, as revealed in the data, suggests that the strange phenomenon could either be a nascent black hole or neutron star with a powerful magnetic field, sucking in the surrounding material.

“The most exciting interpretation is that we might have seen for the first time the birth of a black hole or a neutron star,” says Raffaella Margutti of Northwestern University, USA, lead author of the paper.

“We know that black holes and neutron stars form when stars collapse and explode as a supernova, but never before have we seen one right at the time of birth,” adds co-author Indrek Vurm of Tartu Observatory, Estonia, who worked on modelling the observations.

An image of supernova explosion AT2018cow and its host galaxy, CGCG 137-068, which is located some 200 million light years away. The image was obtained on 17 August 2018 using the DEep Imaging and Multi-Object Spectrograph (DEIMOS) on the W. M. Keck Observatory in Hawaii. The insert in the top left shows a zoom onto the galaxy, indicating the location of the supernova. The supernova was first spotted on 16 June 2018 with the ATLAS telescope, also in Hawaii. Further observations performed with a large team of telescopes – including ESA’s high-energy space telescopes Integral and XMM-Newton – revealed a source of powerful X-rays at the centre of this unprecedentedly bright and rapidly evolving stellar explosion, suggesting that it could either be a nascent black hole or neutron star with a powerful magnetic field, sucking in the surrounding material. Credit: R. Margutti/W. M. Keck Observatory

The AT2018cow explosion was not only 10 to 100 times brighter than any other supernova previously observed: it also reached peak luminosity much faster than any other previously known event – in only a few days compared to the usual two weeks.

Integral made its first observations of the phenomenon about five days after it had been reported and kept monitoring it for 17 days. Its data proved crucial for the understanding of the strange object.

“Integral covers a wavelength range which is not covered by any other satellite,” says Erik Kuulkers, Integral project scientist at ESA. “We have a certain overlap with NuSTAR in the high-energy X-ray part of the spectrum but we can see higher energies, too.”

So while data from NuSTAR revealed the hard X-ray spectrum in great detail, with Integral the astronomers were able to see the spectrum of the source entirely, including its upper limit at soft gamma-ray energies.

“We saw a kind of a bump with a sharp cut-off in the spectrum at the high-energy end,” says Volodymyr Savchenko, an astronomer at the University of Geneva, Switzerland, who worked on the Integral data. “This bump is an additional component of the radiation released by this explosion, shining through an opaque, or optically thick, medium.”

“This high-energy radiation most likely came from an area of very hot and dense plasma surrounding the source,” adds Carlo Ferrigno, also of the University of Geneva.

The evolution of supernova explosion AT2018cow as observed at soft X-rays with NASA’s Swift (red circles) and ESA’s XMM-Newton (red triangles) space observatories, and at hard X-rays with NASA’s NuSTAR (orange circles) and ESA’s INTEGRAL (yellow circles) satellites. The supernova was first spotted on 16 June 2018 with the ATLAS telescope in Hawaii. The data shown in this animation were collected between 22 June and 22 July. These observations revealed a source of powerful X-rays at the centre of this unprecedentedly bright and rapidly evolving stellar explosion, suggesting that it could either be a nascent black hole or neutron star with a powerful magnetic field, sucking in the surrounding material. Credit: R. Margutti et al (2019)

Because Integral kept monitoring the AT2018cow explosion over a longer period of time, its data was also able to show that the high-energy X-ray signal was gradually fading.

Raffaella explains that this high-energy X-ray radiation that went away was the so-called reprocessed radiation – radiation from the source interacting with material ejected by the explosion. As the material travels away from the centre of the explosion, the signal gradually wanes and eventually disappears completely.

In this signal, however, the astronomers were able to find patterns typical of an object that draws in matter from its surroundings – either a black hole or a neutron star.

“This is the most unusual thing that we have observed in AT2018cow and it’s definitely something unprecedented in the world of explosive transient astronomical events,” says Raffaella.

Meanwhile, XMM-Newton looked at this unusual explosion twice over the first 100 days of its existence. It detected the lower-energy part of its X-ray emission, which, according to the astronomers, comes directly from the engine at the core of the explosion. Unlike the high-energy X-rays coming from the surrounding plasma, the lower-energy X-rays from the source are still visible.

The astronomers plan to use XMM-Newton to perform a follow-up observation in the future, which will allow them to understand the source’s behaviour over a longer period of time in greater detail.

“We are continuing to analyse the XMM-Newton data to try to understand the nature of the source,” says co-author Giulia Migliori of University of Bologna, Italy, who worked on the X-ray data. “Accreting black holes leave characteristic imprints in X-rays, which we might be able to detect in our data.”

“This event was completely unexpected and it shows that there is a lot of which we don’t completely understand,” says Norbert Schartel, ESA’s XMM-Newton project scientist. “One satellite, one instrument alone, would never be able to understand such a complex object. The detailed insights we were able to gather into the inner workings of the mysterious AT2018cow explosion were only achievable thanks to the broad cooperation and combination of many telescopes.”

See the full article here .

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The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

From NASA Goddard Space Flight Center: “NASA’s NuSTAR Mission Proves Superstar Eta Carinae Shoots Cosmic Rays”

From NASA Goddard Space Flight Center

July 3, 2018
Francis Reddy
francis.j.reddy@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

A new study using data from NASA’s NuSTAR space telescope suggests that Eta Carinae, the most luminous and massive stellar system within 10,000 light-years, is accelerating particles to high energies — some of which may reach Earth as cosmic rays.

NASA NuSTAR X-ray telescope

Eta Carinae Image Credit: N. Smith, J. A. Morse (U. Colorado) et al., NASA

“We know the blast waves of exploded stars can accelerate cosmic ray particles to speeds comparable to that of light, an incredible energy boost,” said Kenji Hamaguchi, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the lead author of the study. “Similar processes must occur in other extreme environments. Our analysis indicates Eta Carinae is one of them.”

Astronomers know that cosmic rays with energies greater than 1 billion electron volts (eV) come to us from beyond our solar system. But because these particles — electrons, protons and atomic nuclei — all carry an electrical charge, they veer off course whenever they encounter magnetic fields. This scrambles their paths and masks their origins.

Zoom into Eta Carinae, where the outflows of two massive stars collide and shoot accelerated particles — cosmic rays — into space.
Credits: NASA’s Goddard Space Flight Center

Eta Carinae, located about 7,500 light-years away in the southern constellation of Carina, is famous for a 19th century outburst that briefly made it the second-brightest star in the sky. This event also ejected a massive hourglass-shaped nebula, but the cause of the eruption remains poorly understood.

The system contains a pair of massive stars whose eccentric orbits bring them unusually close every 5.5 years. The stars contain 90 and 30 times the mass of our Sun and pass 140 million miles (225 million kilometers) apart at their closest approach — about the average distance separating Mars and the Sun.

“Both of Eta Carinae’s stars drive powerful outflows called stellar winds,” said team member Michael Corcoran, also at Goddard. “Where these winds clash changes during the orbital cycle, which produces a periodic signal in low-energy X-rays we’ve been tracking for more than two decades.”

NASA’s Fermi Gamma-ray Space Telescope also observes a change in gamma rays — light packing far more energy than X-rays — from a source in the direction of Eta Carinae. But Fermi’s vision isn’t as sharp as X-ray telescopes, so astronomers couldn’t confirm the connection.

Eta Carinae shines in X-rays in this image from NASA’s Chandra X-ray Observatory.

NASA/Chandra X-ray Telescope

The colors indicate different energies. Red spans 300 to 1,000 electron volts (eV), green ranges from 1,000 to 3,000 eV and blue covers 3,000 to 10,000 eV. For comparison, the energy of visible light is about 2 to 3 eV. NuSTAR observations (green contours) reveal a source of X-rays with energies some three times higher than Chandra detects. X-rays seen from the central point source arise from the binary’s stellar wind collision. The NuSTAR detection shows that shock waves in the wind collision zone accelerate charged particles like electrons and protons to near the speed of light. Some of these may reach Earth, where they will be detected as cosmic ray particles. X-rays scattered by debris ejected in Eta Carinae’s famous 1840 eruption may produce the broader red emission. Credits: NASA/CXC and NASA/JPL-Caltech

To bridge the gap between low-energy X-ray monitoring and Fermi observations, Hamaguchi and his colleagues turned to NuSTAR. Launched in 2012, NuSTAR can focus X-rays of much greater energy than any previous telescope. Using both newly taken and archival data, the team examined NuSTAR observations acquired between March 2014 and June 2016, along with lower-energy X-ray observations from the European Space Agency’s XMM-Newton satellite over the same period.

ESA/XMM Newton

Eta Carinae’s low-energy, or soft, X-rays come from gas at the interface of the colliding stellar winds, where temperatures exceed 70 million degrees Fahrenheit (40 million degrees Celsius). But NuSTAR detects a source emitting X-rays above 30,000 eV, some three times higher than can be explained by shock waves in the colliding winds. For comparison, the energy of visible light ranges from about 2 to 3 eV.

The team’s analysis, presented in a paper published on Monday, July 2, in Nature Astronomy, shows that these “hard” X-rays vary with the binary orbital period and show a similar pattern of energy output as the gamma rays observed by Fermi.

The researchers say that the best explanation for both the hard X-ray and the gamma-ray emission is electrons accelerated in violent shock waves along the boundary of the colliding stellar winds. The X-rays detected by NuSTAR and the gamma rays detected by Fermi arise from starlight given a huge energy boost by interactions with these electrons.

Some of the superfast electrons, as well as other accelerated particles, must escape the system and perhaps some eventually wander to Earth, where they may be detected as cosmic rays.

“We’ve known for some time that the region around Eta Carinae is the source of energetic emission in high-energy X-rays and gamma rays”, said Fiona Harrison, the principal investigator of NuSTAR and a professor of astronomy at Caltech in Pasadena, California. “But until NuSTAR was able to pinpoint the radiation, show it comes from the binary and study its properties in detail, the origin was mysterious.”

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. Caltech manages JPL for NASA.

For more information on NuSTAR, visit:

https://www.nasa.gov/nustar

http://www.nustar.caltech.edu

See the full article here.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

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NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

NASA/Goddard Campus

From JPL: “NuSTAR’s First Five Years in Space”

JPL-Caltech

June 13, 2017
Written by Whitney Clavin, Caltech

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
Elizabeth.landau@jpl.nasa.gov

Whitney Clavin
Caltech, Pasadena, Calif.
626-395-1856
wclavin@caltech.edu

This artist’s concept shows NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) spacecraft on orbit. Credit: NASA/JPL-Caltech

Five years ago, on June 13, 2012, Caltech’s Fiona Harrison, principal investigator of NASA’s NuSTAR mission, watched with her team as their black-hole-spying spacecraft was launched into space aboard a rocket strapped to the belly of an aircraft. The launch occurred over the Kwajalein Atoll in the Marshall Islands. Many members of the team anxiously followed the launch from the mission’s operations center at the University of California, Berkeley, anxious to see what NuSTAR would find.

Now, Harrison shares her take on five of the mission’s many iconic images and artist concepts — ranging from our flaring sun to distant, buried black holes. NuSTAR is the first telescope capable of focusing high-energy X-rays — and it has taken the most detailed images of the sky in this energy regime to date.

This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. Image credit: NASA/JPL-Caltech

Untangling the Remains of Cassiopeia A Image credit: NASA/JPL-Caltech/CXC/SAO

“This is a beautiful image, and one of the things we built NuSTAR to do — to make the first-ever map of emission from radioactivity in the remnant of an exploded star,” Harrison said. “We spent years developing specialized detectors to have the capability to make this image. From the image, we were able to determine the mechanism that caused the star to explode.” NuSTAR data show high-energy X-rays from radioactive material in blue. Non-radioactive materials are red, yellow and green.

NuSTAR Finds a Pulse in Cigar Galaxy. Low-energy X-ray data from NASA’s Chandra X-ray Observatory are colored blue, and higher-energy X-ray data from NuSTAR are pink. The bulk of a galaxy called Messier 82 (M82), or the “Cigar galaxy,” is seen in visible-light data captured by the National Optical Astronomy Observatory’s 2.1-meter telescope at Kitt Peak in Arizona. Image credit: NASA/JPL-Caltech/SAO/NOAO

NASA/Chandra Telescope

2.1 meter NOAO telescope, Kitt Peak, AZ, USA

NuSTAR Stares at the Sun. High-energy X-rays from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) are shown in blue; low-energy X-rays from Japan’s Hinode spacecraft are green; and extreme ultraviolet light from NASA’s Solar Dynamics Observatory (SDO) is yellow and red. Image credit: NASA/JPL-Caltech/GSFC/JAXA

“With NuSTAR, we see flaring, active regions of the sun where high-energy particles are being created. NuSTAR was built as an astrophysics mission, not to study the sun,” Harrison said. “People thought we were crazy at first to point such a sensitive observatory at the sun and potentially ruin it. But now, by studying the sun with much greater sensitivity in high-energy X-rays, we are making important contributions to the field of solar physics.”.

JAXA/HINODE spacecraft

NASA/SDO

“This is a beautiful image, and one of the things we built NuSTAR to do — to make the first-ever map of emission from radioactivity in the remnant of an exploded star,” Harrison said. “We spent years developing specialized detectors to have the capability to make this image. From the image, we were able to determine the mechanism that caused the star to explode.” NuSTAR data show high-energy X-rays from radioactive material in blue. Non-radioactive materials are red, yellow and green.
NuSTAR Finds a Pulse in Cigar Galaxy

“This result was one of the biggest surprises from NuSTAR. We detected X-ray pulses from an object in a galaxy that everybody had assumed was a black hole, thereby showing it was actually a stellar remnant called a pulsar. At the time, it was by far the brightest pulsar known. At first nobody believed it, but the signal was so strong and clear,” Harrison said. Since this discovery two other extremely bright pulsars have been found — prompted by NuSTAR’s discovery. High-energy X-rays from the pulsar are seen in pink at the center of the
image.

Galaxy NGC 1448 with Active Galactic Nucleus.

“This image illustrates another major accomplishment NuSTAR was designed for — to find hidden black holes buried by dust and gas,” Harrison said. “This is a wonderful result, led by two graduate students. What they found is that there is a thick layer of gas and dust hiding the active black hole in the galaxy NGC 1448 from our sight.”

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA.

For more information on NuSTAR, visit:

https://www.nasa.gov/nustar

http://www.nustar.caltech.edu

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

From JPL-Caltech: “NuSTAR Probes Puzzling Galaxy Merger”

JPL-Caltech

March 27, 2017
Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau@jpl.nasa.gov

This optical image shows the Was 49 system, which consists of a large disk galaxy, Was 49a, merging with a much smaller “dwarf” galaxy Was 49b. Image credit: DCT/NRL [Discovery Channel Telescope, Happy Jack, AZ, USA/ Naval Research Laboratory.]

A supermassive black hole inside a tiny galaxy is challenging scientists’ ideas about what happens when two galaxies become one.

Was 49 is the name of a system consisting of a large disk galaxy, referred to as Was 49a, merging with a much smaller “dwarf” galaxy called Was 49b. The dwarf galaxy rotates within the larger galaxy’s disk, about 26,000 light-years from its center. Thanks to NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) mission, scientists have discovered that the dwarf galaxy is so luminous in high-energy X-rays, it must host a supermassive black hole much larger and more powerful than expected.

NASA/NuSTAR

“This is a completely unique system and runs contrary to what we understand of galaxy mergers,” said Nathan Secrest, lead author of the study and postdoctoral fellow at the U.S. Naval Research Laboratory in Washington.

Data from NuSTAR and the Sloan Digital Sky Survey suggest that the mass of the dwarf galaxy’s black hole is huge, compared to similarly sized galaxies, at more than 2 percent of the galaxy’s own mass.

SDSS Telescope at Apache Point Observatory, NM, USA

“We didn’t think that dwarf galaxies hosted supermassive black holes this big,” Secrest said. “This black hole could be hundreds of times more massive than what we would expect for a galaxy of this size, depending on how the galaxy evolved in relation to other galaxies.”

The dwarf galaxy’s black hole is the engine of an active galactic nucleus (AGN), a cosmic phenomenon in which extremely high-energy radiation bursts forth as a black hole devours gas and dust. This particular AGN appears to be covered by a donut-shaped structure made of gas and dust. NASA’s Chandra and Swift missions were used to further characterize the X-ray emission.

NASA/Chandra Telescope

NASA/SWIFT Telescope

Normally, when two galaxies start to merge, the larger galaxy’s central black hole becomes active, voraciously gobbling gas and dust, and spewing out high-energy X-rays as matter gets converted into energy. That is because, as galaxies approach each other, their gravitational interactions create a torque that funnels gas into the larger galaxy’s central black hole. But in this case, the smaller galaxy hosts a more luminous AGN with a more active supermassive black hole, and the larger galaxy’s central black hole is relatively quiet.

Normally, when two galaxies start to merge, the larger galaxy’s central black hole becomes active, voraciously gobbling gas and dust, and spewing out high-energy X-rays as matter gets converted into energy. That is because, as galaxies approach each other, their gravitational interactions create a torque that funnels gas into the larger galaxy’s central black hole. But in this case, the smaller galaxy hosts a more luminous AGN with a more active supermassive black hole, and the larger galaxy’s central black hole is relatively quiet.

An optical image of the Was 49 system, compiled using observations from the Discovery Channel Telescope in Happy Jack, Arizona, uses the same color filters as the Sloan Digital Sky Survey.

Discovery Channel Telescope at Lowell Observatory, Happy Jack AZ, USA

Since Was 49 is so far away, these colors are optimized to separate highly-ionized gas emission, such as the pink-colored region around the feeding supermassive black hole, from normal starlight, shown in green. This allowed astronomers to more accurately determine the size of the dwarf galaxy that hosts the supermassive black hole.

The pink-colored emission stands out in a new image because of the intense ionizing radiation emanating from the powerful AGN. Buried within this region of intense ionization is a faint collection of stars, believed to be part of the galaxy surrounding the enormous black hole. These striking features lie on the outskirts of the much larger spiral galaxy Was 49a, which appears greenish in the image due to the distance to the galaxy and the optical filters used.

Scientists are still trying to figure out why the supermassive black hole of dwarf galaxy Was 49b is so big. It may have already been large before the merger began, or it may have grown during the very early phase of the merger.

“This study is important because it may give new insight into how supermassive black holes form and grow in such systems,” Secrest said. “By examining systems like this, we may find clues as to how our own galaxy’s supermassive black hole formed.”

In several hundred million years, the black holes of the large and small galaxies will merge into one enormous beast.

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive.

For more information on NuSTAR, visit:

http://www.nasa.gov/nustar

http://www.nustar.caltech.edu

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

From Astronomy: “This nearby supermassive black hole packs a pretty big punch”

Astronomy Magazine

March 01, 2017
Alison Klesman

NGC 6814 is a stunning example of a Seyfert galaxy. Like IRAS 13224−3809, this galaxy hosts a bright, highly X-ray variable supermassive black hole at its center. ESA/Hubble & NASA; Acknowledgement: Judy Schmidt (Geckzilla)

Supermassive black holes are associated with the vast majority of galaxies. They’re believed to evolve with their host galaxies and even to affect galaxy growth over time, owing to their ability to gobble up vast amounts of gas and dust and shoot high-energy radiation back out into their surroundings.

There are measurable correlations between the mass of a supermassive black hole and the properties of its host galaxy’s bulge, such as the luminosity of the bulge and the movements of stars within it. The reasons for these correlations are still unknown, but astronomers have long believed that supermassive black holes affect the star formation around them via some sort of feedback process.

In a letter printed today in Nature, a group of astronomers led by Michael Parker at the Institute of Astronomy in Cambridge, UK, report their observations of IRAS 13224−3809, a nearby Seyfert galaxy hosting an active galactic nucleus, or AGN. Seyfert galaxies shine intensely in infrared light due to the activity of their supermassive black holes, which are relatively low mass but are accreting at high rates. IRAS 13224−3809 hosts a central supermassive black hole weighing about 6,000,000 times the mass of our Sun.

Parker and his coauthors studied observations of IRAS 13224−3809 taken with the X-ray Multi-Mirror Mission [ESA/XMM-Newton] over the course of 17 days and with the Nuclear Spectroscopic Telescope Array [NASA/NuSTAR] over the course of six days. They observed X-ray variability on scales of minutes to weeks.

ESA/XMM Newton

NASA/NuSTAR

By looking at the X-ray spectrum of the source, they were able to determine that this object offers a relatively unhindered view right down into the inner portions of the accretion disk near the black hole itself.

When astronomers “look” at a supermassive black hole, they’re actually observing light from the accretion disk of matter around the black hole, which hasn’t yet fallen past the event horizon and become invisible. Supermassive black holes show variability over time in a variety of wavelengths, including optical light, infrared light, and X-rays. This variability is believed to arise from changes in the accretion disk, such as clumps of matter or outflows of gas and radiation.

IRAS 13224−3809’s black hole shows extraordinary X-ray variability — in fact, it’s the most variable AGN observed at X-ray wavelengths. Parker’s group was able to watch the effects of an ultrafast outflow, which is associated with areas of the accretion disk within a few hundred times the size of the event horizon. Ultrafast outflows, or UFOs, are outflows moving faster than about 6,000 miles per second (10,000 km/s). They’re believed to be triggered by X-ray radiation associated with accretion at the innermost portions of the disk, just a few times the size of the event horizon.

IRAS 13224−3809’s outflow was clocked at 44,000 miles per second (71,000 km/s), or about 0.236 times the speed of light. This puts it in the top 5 percent of UFOs ever observed. What’s more, the power it’s putting out is on par with quasars that are three orders of magnitude more massive.

Because of their immense power, IRAS 13224−3809’s outflows may be strong enough to drive feedback in its host galaxy, just as more massive quasars do in the much more distant universe.

While all black holes are variable, the timescale of variability typically scales with size. This makes sense when you think of variability relating to the accretion disk, which also scales with size. Thus, IRAS 13224−3809 shows much faster variability than the variability observed in quasars, which are similar but much more massive objects. Parker and his group were able to watch IRAS 13224−3809’s X-ray light undergo changes that took only hours, rather than months in a quasar.

Studying IRAS 13224−3809 could thus help astronomers finally start to answer questions about how UFOs and other outflows are created. It could also shed light on how black hole feedback affects the host galaxy. This object’s unique properties would allow studies to be performed more easily and with much shorter observing times than those focused on faraway, slower-acting quasars.

See the full article here .

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From JPL-Caltech: “NuSTAR Finds New Clues to ‘Chameleon Supernova'”

JPL-Caltech

January 24, 2017
Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
Elizabeth.landau@jpl.nasa.gov

This visible-light image from the Sloan Digital Sky Survey shows spiral galaxy NGC 7331, center, where astronomers observed the unusual supernova SN 2014C .

The inset images are from NASA’s Chandra X-ray Observatory, showing a small region of the galaxy before the supernova explosion (left) and after it (right). Red, green and blue colors are used for low, medium and high-energy X-rays, respectively.

SDSS Telescope at Apache Point, NM, USA

Fast Facts:

— Supernova SN 2014C dramatically changed its appearance over a year

— It appears SN 2014C threw off a lot of material before it exploded

— The study suggests astronomers should pay attention to the lives of massive stars in the centuries before they explode

“We’re made of star stuff,” astronomer Carl Sagan famously said. Nuclear reactions that happened in ancient stars generated much of the material that makes up our bodies, our planet and our solar system. When stars explode in violent deaths called supernovae, those newly formed elements escape and spread out in the universe.

One supernova in particular is challenging astronomers’ models of how exploding stars distribute their elements. The supernova SN 2014C dramatically changed in appearance over the course of a year, apparently because it had thrown off a lot of material late in its life. This doesn’t fit into any recognized category of how a stellar explosion should happen. To explain it, scientists must reconsider established ideas about how massive stars live out their lives before exploding.

“This ‘chameleon supernova’ may represent a new mechanism of how massive stars deliver elements created in their cores to the rest of the universe,” said Raffaella Margutti, assistant professor of physics and astronomy at Northwestern University in Evanston, Illinois. Margutti led a study about supernova SN 2014C published this week in The Astrophysical Journal.

A supernova mystery

Astronomers classify exploding stars based on whether or not hydrogen is present in the event. While stars begin their lives with hydrogen fusing into helium, large stars nearing a supernova death have run out of hydrogen as fuel. Supernovae in which very little hydrogen is present are called “Type I.” Those that do have an abundance of hydrogen, which are rarer, are called “Type II.”

But SN 2014C, discovered in 2014 in a spiral galaxy about 36 million to 46 million light-years away, is different. By looking at it in optical wavelengths with various ground-based telescopes, astronomers concluded that SN 2014C had transformed itself from a Type I to a Type II supernova after its core collapsed, as reported in a 2015 study led by Dan Milisavljevic at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Initial observations did not detect hydrogen, but, after about a year, it was clear that shock waves propagating from the explosion were hitting a shell of hydrogen-dominated material outside the star.

In the new study, NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) satellite, with its unique ability to observe radiation in the hard X-ray energy range — the highest-energy X-rays — allowed scientists to watch how the temperature of electrons accelerated by the supernova shock changed over time. They used this measurement to estimate how fast the supernova expanded and how much material is in the external shell.

NASA/NuSTAR

To create this shell, SN 2014C did something truly mysterious: it threw off a lot of material — mostly hydrogen, but also heavier elements — decades to centuries before exploding. In fact, the star ejected the equivalent of the mass of the sun. Normally, stars do not throw off material so late in their life.

“Expelling this material late in life is likely a way that stars give elements, which they produce during their lifetimes, back to their environment,” said Margutti, a member of Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics.

NASA’s Chandra and Swift observatories were also used to further paint the picture of the evolution of the supernova.

NASA/Chandra Telescope

NASA/SWIFT Telescope

The collection of observations showed that, surprisingly, the supernova brightened in X-rays after the initial explosion, demonstrating that there must be a shell of material, previously ejected by the star, that the shock waves had hit.

Challenging existing theories

Why would the star throw off so much hydrogen before exploding? One theory is that there is something missing in our understanding of the nuclear reactions that occur in the cores of massive, supernova-prone stars. Another possibility is that the star did not die alone — a companion star in a binary system may have influenced the life and unusual death of the progenitor of SN 2014C. This second theory fits with the observation that about seven out of 10 massive stars have companions.

The study suggests that astronomers should pay attention to the lives of massive stars in the centuries before they explode. Astronomers will also continue monitoring the aftermath of this perplexing supernova.

“The notion that a star could expel such a huge amount of matter in a short interval is completely new,” said Fiona Harrison, NuSTAR principal investigator based at Caltech in Pasadena. “It is challenging our fundamental ideas about how massive stars evolve, and eventually explode, distributing the chemical elements necessary for life.”

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA.

For more information on NuSTAR, visit:

http://www.nasa.gov/nustar

http://www.nustar.caltech.edu

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

From Space Science Laboratory at UC Berkeley: “NuSTAR – Black Holes Hide in our Cosmic Backyard”

UC Berkeley

Space Science Laboratory

No image caption. No image credit.

NuSTAR

January 12, 2017
Christopher Scholz

Monster black holes sometimes lurk behind gas and dust, hiding from the gaze of most telescopes. But they give themselves away when material they feed on emits high-energy X-rays that NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) mission can detect. That’s how NuSTAR recently identified two gas-enshrouded supermassive black holes, located at the centers of nearby galaxies.

“These black holes are relatively close to the Milky Way, but they have remained hidden from us until now,” said Ady Annuar, a graduate student at Durham University in the United Kingdom, who presented the results at the American Astronomical Society meeting in Grapevine, Texas. “They’re like monsters hiding under your bed.”

Both of these black holes are the central engines of what astronomers call “active galactic nuclei,” a class of extremely bright objects that includes quasars and blazars. Depending on how these galactic nuclei are oriented and what sort of material surrounds them, they appear very different when examined with telescopes.

Active galactic nuclei are so bright because particles in the regions around the black hole get very hot and emit radiation across the full electromagnetic spectrum — from low-energy radio waves to high-energy X-rays. However, most active nuclei are believed to be surrounded by a doughnut-shaped region of thick gas and dust that obscures the central regions from certain lines of sight. Both of the active galactic nuclei that NuSTAR recently studied appear to be oriented such that astronomers view them edge-on. That means that instead of seeing the bright central regions, our telescopes primarily see the reflected X-rays from the doughnut-shaped obscuring material.

“Just as we can’t see the sun on a cloudy day, we can’t directly see how bright these active galactic nuclei really are because of all of the gas and dust surrounding the central engine,” said Peter Boorman, a graduate student at the University of Southampton in the United Kingdom.

Boorman led the study of an active galaxy called IC 3639, which is 170 million light years away.

IC 3639, a galaxy with an active galactic nucleus, is seen in this image combining data from the Hubble Space Telescope and the European Southern Observatory.

This galaxy contains an example of a supermassive black hole hidden by gas and dust. Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA’s Chandra X-Ray Observatory and the Japanese-led Suzaku satellite.

NASA/Chandra Telescope

JAXA/Suzaku satellite

The findings from NuSTAR, which is more sensitive to higher energy X-rays than these observatories, confirm the nature of IC 3639 as an active galactic nucleus that is heavily obscured, and intrinsically much brighter than observed.

Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA’s Chandra X-Ray Observatory and the Japan-led Suzaku satellite. NuSTAR also provided the first precise measurement of how much material is obscuring the central engine of IC 3639, allowing researchers to determine how luminous this hidden monster really is.

More surprising is the spiral galaxy that Annuar focused on: NGC 1448.

NGC 1448 (also designated NGC 1457 and ESO 249-16) is a spiral galaxy located about 60 million light-years away in the constellation Horologium. It has a prominent disk of young and very bright stars surrounding its small, shining core. The galaxy is receding from us with 1168 kilometers per second.

NGC 1448 has recently been a prolific factory of supernovae, the dramatic explosions that mark the death of stars: after a first one observed in this galaxy in 1983 (SN 1983S), two more have been discovered during the past decade.

Visible as a red dot inside the disc, in the upper right part of the image, is the supernova observed in 2003 (Type II supernova SN 2003hn), whereas another one, detected in 2001 (Type Ia supernova SN 2001el), can be noticed as a tiny blue dot in the central part of the image, just below the galaxy’s core. If captured at the peak of the explosion, a supernova might be as bright as the whole galaxy that hosts it.

A Type Ia supernova is a result from the violent explosion of a white dwarf star. This category of supernovae produces consistent peak luminosity. The stability of this luminosity allows these supernovae to be used as standard candles to measure the distance to their host galaxies because the visual magnitude of the supernovae depends primarily on the distance.

A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, and no more than 40–50 times the mass of the Sun for this type of explosion. It is distinguished from other types of supernova by the presence of hydrogen in its spectrum. Type II supernovae are mainly observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies.

This image was obtained using the 8.2-metre telescopes of ESO’s Very Large Telescope. It combines exposures taken between July 2002 and the end of November 2003.

ESO/VLT at Cerro Paranal, Chile, ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

Credit: ESO

The black hole in its center was only discovered in 2009, even though it is at the center of one of the nearest large galaxies to our Milky Way. By “near,” astronomers mean NGC 1448 is only 38 million light years away (one light year is about 6 trillion miles).

Annuar’s study discovered that this galaxy also has a thick column of gas hiding the central black hole, which could be part of a doughnut-shaped region. X-ray emission from NGC 1448, as seen by NuSTAR and Chandra, suggests for the first time that, as with IC 3639, there must be a thick layer of gas and dust hiding the active black hole in this galaxy from our line of sight.

Researchers also found that NGC 1448 has a large population of young (just 5 million year old) stars, suggesting that the galaxy produces new stars at the same time that its black hole feeds on gas and dust. Researchers used the European Southern Observatory New Technology Telescope to image NGC 1448 at optical wavelengths, and identified where exactly in the galaxy the black hole should be. A black hole’s location can be hard to pinpoint because the centers of galaxies are crowded with stars. Large optical and radio telescopes can help detect light from around black holes so that astronomers can find their location and piece together the story of their growth.

“It is exciting to use the power of NuSTAR to get important, unique information on these beasts, even in our cosmic backyard where they can be studied in detail,” said Daniel Stern, NuSTAR project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA.

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Stem Education Coalition

Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.