From NASA NuSTAR: “NASA’s NuSTAR Makes Illuminating Discoveries With ‘Nuisance’ Light”

National Aeronautics and Space Administration/Technical University of Denmark [Danmarks Tekniske Universite](DK)/ASI Italian Space Agency [Agenzia Spaziale Italiana](IT) NuSTAR X-ray telescope.

From NASA NuSTAR

Mar 1, 2022

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

A design quirk in the X-ray observatory has made it possible for astronomers to use previously unwanted light to study even more cosmic objects than before.

For almost 10 years, NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) X-ray space observatory has been studying some of the highest-energy objects in the universe, such as colliding dead stars and enormous black holes feasting on hot gas. During that time, scientists have had to deal with stray light leaking in through the sides of the observatory, which can interfere with observations much like external noise can drown out a phone call.

But now team members have figured out how to use that stray X-ray light to learn about objects in NuSTAR’s peripheral vision while also performing normal targeted observations. This development has the potential to multiply the insights that NuSTAR provides. A new science paper in The Astrophysical Journal describes the first use of NuSTAR’s stray light observations to learn about a cosmic object – in this case, a neutron star.

Nuggets of material left over after a star collapses, neutron stars are some of the densest objects in the universe, second only to black holes. Their powerful magnetic fields trap gas particles and funnel them toward the neutron star’s surface. As the particles are accelerated and energized, they release high-energy X-rays that NuSTAR can detect.

The new study describes a system called SMC X-1 which consists of a neutron star orbiting a living star in one of two small galaxies orbiting the Milky Way (Earth’s home galaxy). The brightness of SMC X-1’s X-ray output appears to vary wildly when viewed by telescopes, but decades of direct observations by NuSTAR and other telescopes have revealed a pattern to the fluctuations. Scientists have pinpointed several reasons why SMC X-1 changes in brightness when studied by X-ray telescopes. For example, the X-rays’ brightness dims as the neutron star dips behind the living star with each orbit. According to the paper, the stray light data was sensitive enough to pick up on some of those well-documented changes.

“I think this paper shows that this stray light approach is reliable, because we observed brightness fluctuations in the neutron star in SMC X-1 that we have already confirmed through direct observations,” said McKinley Brumback, an astrophysicist at Caltech in Pasadena, California, and lead author of the new study. “Going forward, it would be great if we could use the stray light data to look at objects when we don’t already know if they’re regularly changing in brightness and potentially use this approach to detect changes.”

Form and Function

The new approach is possible because of NuSTAR’s shape, which is similar to dumbbell or dog bone: It has two bulky components at either end of a narrow, 33-foot-long (10-meter-long) structure called a deployable mast, or boom. Typically, researchers point one of the bulky ends – which contains the optics, or the hardware that collects X-rays – at the object they want to study. The light travels along the boom to the detectors, located at the other end of the spacecraft. The distance between the two is necessary to focus the light.

But stray light also reaches the detectors by entering through the sides of the boom and bypassing the optics. It appears in NuSTAR’s field of view along with light from whatever object the telescope directly observes, and is often fairly easy to identify by eye: It forms a circle of faint light emerging from the sides of the image. (Unsurprisingly, stray light is a problem for many other space- and ground-based telescopes.)

A group of NuSTAR team members has spent the last few years separating the stray light from various NuSTAR observations. After identifying bright, known X-ray sources in the periphery of each observation, they used computer models to predict how much stray light should appear based on which bright object was nearby. They also looked at almost every NuSTAR observation to confirm the telltale sign of stray light. The team created a catalog of about 80 objects for which NuSTAR had collected stray light observations, naming the collection “StrayCats.”

“Imagine sitting in a quiet movie theater, watching a drama, and hearing the explosions in the action movie playing next door,” said Brian Grefenstette, senior research scientist at Caltech and the NuSTAR team member leading the StrayCats work. “In the past, that’s what the stray light was like – a distraction from what we were trying to focus on. Now we have the tools to turn that extra noise into useful data, opening an entire new way of using NuSTAR to study the universe.”

Of course, the stray light data can’t replace direct observations by NuSTAR. Aside from stray light being unfocused, many objects that NuSTAR can observe directly are too faint to appear in the stray light catalog. But Grefenstette said multiple Caltech students have combed through the data and found instances of rapid brightening from peripheral objects, which might be any number of dramatic events, such as thermonuclear explosions on the surfaces of neutron stars. Observing the frequency and intensity of a neutron star’s changes in brightness can help scientists decipher what’s happening to those objects.

“If you’re trying to look for a pattern in the long-term behavior or brightness of an X-ray source, the stray light observations could be a great way to check in more often and establish a baseline,” said Renee Ludlam, a NASA Hubble Fellowship Program Einstein fellow at Caltech and member of the StrayCats team. “They could also let us catch odd behaviors in these objects when we don’t expect them or when we wouldn’t normally be able to point NuSTAR directly at them. The stray light observations don’t replace direct observations, but more data is always good.”

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

NASA’s NuSTAR X-ray Telescope is a Small Explorer mission led by California Institute of Technology (US) and managed by NASA’s JPL-Caltech (US) for the agency’s Science Mission Directorate (US) in Washington. NuSTAR was developed in partnership with the Technical University of Denmark[Danmarks Tekniske Universitet](DK) and the ASI Italian Space Agency [Agenzia Spaziale Italiana](IT). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia(US) (now part of Northrop Grumman). NuSTAR’s mission operations center is at University of California-Berkeley (US), and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center(US). ASI provides the mission’s ground station and a mirror archive. JPL is a division of Caltech

The National Aeronautics and Space Administration (NASA) (US) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA] Greenhouse Gases Observing Satellite.

From NASA NuSTAR : “Seeing Some Cosmic X-Ray Emitters Might Be a Matter of Perspective”

From NASA NuSTAR

July 9, 2021

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

This illustration shows SS 433, a black hole or neutron star, as it pulls material away from its companion star. The stellar material forms a disk around SS 433, and some of the material is ejected into space in the form of two thin jets (pink) traveling in opposite directions away from SS 433. Credits: DESY Electron Synchrotron[ Deütsches Elektronen-Synchrotron](DE)/Science Communication Lab.

Known as ultraluminous X-ray sources, the emitters are easy to spot when viewed straight on, but they might be hidden from view if they point even slightly away from Earth.

It’s hard to miss a flashlight beam pointed straight at you. But that beam viewed from the side appears significantly dimmer. The same holds true for some cosmic objects: Like a flashlight, they radiate primarily in one direction, and they look dramatically different depending on whether the beam points away from Earth (and nearby space telescopes) or straight at it.

New data from NASA’s NuSTAR space observatory indicates that this phenomenon holds true for some of the most prominent X-ray emitters in the local universe: ultraluminous X-ray sources, or ULXs. Most cosmic objects, including stars, radiate little X-ray light, particularly in the high-energy range seen by NuSTAR. ULXs, by contrast, are like X-ray lighthouses cutting through the darkness. To be considered a ULX a source must have an X-ray luminosity that is about a million times brighter than the total light output of the Sun (at all wavelengths). ULXs are so bright, they can be seen millions of light-years away, in other galaxies.

The new study [MNRAS] shows that the object known as SS 433, located in the Milky Way galaxy and only about 20,000 light-years from Earth, is a ULX, even though it appears to be about 1,000 times dimmer than the minimum threshold to be considered one.

This faintness is a trick of perspective, according to the study: The high-energy X-rays from SS 433 are initially confined within two cones of gas extending outward from opposite sides of the central object. These cones are similar to a mirrored bowl that surrounds a flashlight bulb: They corral the X-ray light from SS 433 into a narrow beam, until it escapes and is detected by NuSTAR. But because the cones are not pointing directly at Earth, NuSTAR can’t see the object’s full brightness.

This illustration shows SS 433, a black hole or neutron star, as it pulls material away from its companion star. The stellar material forms a disk around SS 433, and some of the material is ejected into space in the form of two thin jets (pink) traveling in opposite directions away from SS 433. Credits: DESY/Science Communication Lab.

“We’ve long suspected that some ULXs emit light in narrow columns, rather than in every direction like a bare lightbulb,” said Matt Middleton, a professor of astrophysics at the University of Southampton (UK) and the study’s lead author. “In our study, we confirm this hypothesis by showing that SS 433 would qualify as a ULX to a face-on observer.”

If a ULX relatively close to Earth can hide its true brightness because of how it is oriented, then there are likely more ULXs – particularly in other galaxies – disguised in a similar way. That means the total ULX population should be far larger than scientists currently observe.

Cone of Darkness

About 500 ULXs have been found in other galaxies, and their distance from Earth means it’s often nearly impossible to tell what type of object generates the X-ray emission. The X-rays likely come from a large amount of gas being heated to extreme temperatures as it is pulled in by the gravity of a very dense object. That object could be either a neutron star (the remains of a collapsed star) or a small black hole, one that is no more than about 30 times the mass of our Sun. The gas forms a disk around the object, like water circling a drain. Friction in the disk drives up the temperature, causing it to radiate, sometimes growing so hot that the system erupts with X-rays. The faster the material falls onto the central object, the brighter the X-rays.

Astronomers suspect that the object at the heart of SS 433 is a black hole about 10 times the mass of our Sun. What’s known for sure is that it is cannibalizing a large nearby star, its gravity siphoning away material at a rapid rate: In a single year SS 433 steals the equivalent of about 30 times the mass of Earth from its neighbor, which makes it the greediest black hole or neutron star known in our galaxy.

“It’s been known for a long time that this thing is eating at a phenomenal rate,” said Middleton. “This is what sets ULXs apart from other objects, and it’s likely the root cause of the copious amounts of X-rays we see from them.”

The object in SS 433 has eyes bigger than its stomach: It’s stealing more material than it can consume. Some of the excess material gets blown off the disk and forms two hemispheres on opposite sides of the disk. Within each one is a cone-shaped void that opens up into space. These are the cones that corral the high-energy X-ray light into a beam. Anyone looking straight down one of the cones would see an obvious ULX. Though composed only of gas, the cones are so thick and massive that they act like lead paneling in an X-ray screening room and block X-rays from passing through them out to the side.

The cosmic object SS 433 contains a bright source of X-ray light surrounded by two hemispheres of hot gas. The gas corrals the light into beams pointing in opposite directions away from the source. SS 433 tilts periodically, causing one X-ray beam to point toward Earth. Credits: NASA/JPL-Caltech.

Scientists have suspected that some ULXs might be hidden from view for this reason. SS 433 provided a unique chance to test this idea because, like a top, it wobbles on its axis – a process astronomers call precession.

Most of the time, both of SS 433’s cones point well away from Earth. But because of the way SS 433 precesses, one cone periodically tilts slightly toward Earth, so scientists can see a little bit of the X-ray light coming out of the top of the cone. In the new study, the scientists looked at how the X-rays seen by NuSTAR change as SS 433 moves. They show that if the cone continued to tilt toward Earth so that scientists could peer straight down it, they would see enough X-ray light to officially call SS 433 a ULX.

Black holes that feed at extreme rates have shaped the history of our universe. Supermassive black holes, which are millions to billions of times the mass of the Sun, can profoundly affect their host galaxy when they feed. Early in the universe’s history, some of these massive black holes may have fed as fast as SS 433, releasing huge amounts of radiation that reshaped local environments. Outflows (like the cones in SS 433) redistributed matter that could eventually form stars and other objects.

But because these quickly consuming behemoths reside in incredibly distant galaxies (the one at the heart of the Milky Way isn’t currently eating much), they remain difficult to study. With SS 433, scientists have found a miniature example of this process, much closer to home and much easier to study, and NuSTAR has provided new insights into the activity occurring there.

“When we launched NuSTAR, I don’t think anyone expected that ULXs would be such a rich area of research for us,” said Fiona Harrison, principal investigator for NuSTAR and a professor of physics at Caltech in Pasadena, California. “But NuSTAR is unique in that it can see almost the whole range of X-ray wavelengths emitted by these objects, and that gives us insight into the extreme processes that must be driving them.”

For more information about NuSTAR, visit:

https://www.nasa.gov/mission_pages/nustar/main/index.html

https://www.nustar.caltech.edu/

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

NASA’s NuSTAR X-ray Telescope is a Small Explorer mission led by California Institute of Technology (US) and managed by NASA’s JPL-Caltech (US) for the agency’s Science Mission Directorate (US) in Washington. NuSTAR was developed in partnership with the Technical University of Denmark[Danmarks Tekniske Universitet](DK) and the ASI Italian Space Agency [Agenzia Spaziale Italiana](IT). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia(US) (now part of Northrop Grumman). NuSTAR’s mission operations center is at University of California-Berkeley (US), and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center(US). ASI provides the mission’s ground station and a mirror archive. JPL is a division of Caltech

The National Aeronautics and Space Administration (NASA) (US) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA] Greenhouse Gases Observing Satellite.

From NASA Chandra and From NASA NuSTAR: “Reclusive Neutron Star May Have Been Found in Famous Supernova”

NASA Chandra X-ray Space Telescope

From NASA Chandra

February 23, 2021

Media contacts:
Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu

Molly Porter
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
molly.a.porter@nasa.gov

Astronomers now have evidence from two X-ray telescopes (Chandra and NuSTAR) for a key component of a famous supernova remnant.

NASA/DTU/ASI NuSTAR X-ray telescope.

Supernova 1987A was discovered on Earth on February 24, 1987, making it the first such event witnessed during the telescopic age.

SN 1987A remnant, imaged by ALMA. The inner region is contrasted with the outer shell, lacy white and blue circles, where the blast wave from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation. Image credit: ALMA / ESO / NAOJ / NRAO / Alexandra Angelich, NRAO / AUI / NSF.

SN1987A. Credit: NASA/ESA Hubble Space Telescope in January, 2017 using its Wide Field Camera 3 (WFC3).

NASA/ESA Hubble WFC3

NASA/ESA Hubble Telescope.

For decades, scientists have searched for a neutron star in SN 1987A, i.e. a dense collapsed core that should have been left behind by the explosion.

This latest study shows that a “pulsar wind nebula” created by such a neutron star may be present.
________________________________________________________________________________________________________

Astronomers have found evidence for the existence of a neutron star at the center of Supernova 1987A (SN 1987A), which scientists have been seeking for over three decades. As reported in our latest press release, SN 1987A was discovered on February 24, 1987. The panel on the left contains a 3D computer simulation, based on Chandra data, of the supernova debris from SN 1987A crashing into a surrounding ring of material. The artist’s illustration (right panel) depicts a so-called pulsar wind nebula, a web of particles and energy blown away from a pulsar, which is a rotating, highly magnetized neutron star. Data collected from NASA’s Chandra X-ray Observatory and NuSTAR in a new study support the presence of a pulsar wind nebula at the center of the ring.

If this result is upheld by future observations, it would confirm the existence of a neutron star in SN 1987A, the collapsed core that astronomers expect would be present after the star exploded. The pulsar would also be the youngest one ever found.

NuSTAR and Chandra images of Supernova 1987A. Credit: NASA.

When a star explodes, it collapses onto itself before the outer layers are blasted into space. The compression of the core turns it into an extraordinarily dense object, with the mass of the Sun squeezed into an object only about 10 miles across. Neutron stars, as they were dubbed because they are made nearly exclusively of densely packed neutrons, are laboratories of extreme physics that cannot be duplicated here on Earth. Some neutron stars have strong magnetic fields and rotate rapidly, producing a beam of light akin to a lighthouse. Astronomers call these objects “pulsars,” and they sometimes blow winds of charged particles that can create pulsar wind nebulas.

Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

With Chandra and NuSTAR, the team found relatively low-energy X-rays from the supernova debris crashing into surrounding material. The team also found evidence of high-energy particles, using NuSTAR’s ability to detect higher-energy X-rays.

There are two likely explanations for this energetic X-ray emission: either a pulsar wind nebula, or particles being accelerated to high energies by blast wave of the explosion. The latter effect doesn’t require the presence of a pulsar and occurs over much larger distances from the center of the explosion.

The latest X-ray study supports the case for the pulsar wind nebula on a couple of fronts. First, the brightness of the higher energy X-rays remained about the same between 2012 and 2014, while the radio emission increased. This goes against expectations in the scenario of energetic particles in the explosion debris. Next, authors estimate it would take almost 400 years to accelerate the electrons up to the highest energies seen in the NuSTAR data, which is over ten times older than the age of the remnant.

The Chandra and NuSTAR data also support a 2020 result from the Atacama Large Millimeter Array (ALMA) that provided possible evidence for the structure of a pulsar wind nebula in the radio band.

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

While this “blob” had other potential explanations, its identification as a pulsar wind nebula could be substantiated with the new X-ray data.

The center of SN 1987A is surrounded by gas and dust. The authors used state-of-the-art simulations to understand how this material would absorb X-rays at different energies, enabling more accurate interpretation of the X-ray spectrum, that is, the spread of X-rays over wavelength. This enables them to estimate what the spectrum of the central regions of SN 1987A is without the obscuring material.

A paper describing these results is being published this week in The Astrophysical Journal Letters. The authors of the paper are Emanuele Greco and Marco Miceli (University of Palermo[Università degli Studi di Palermo](IT)), Salvatore Orlando, Barbara Olmi and Fabrizio Bocchino (Palermo Astronomical Observatory[Giuseppe S. Vaiana Astronomical Observatory](IT), an Italian National Institute for Astrophysics [Istituto Nazionale di Astrofisica](IT) research facility); Shigehiro Nagataki and Masaomi Ono (Astrophysical Big Bang Laboratory, RIKEN Institute of Physical and Chemical Research [Kokuritsu Kenkyū Kaihatsu Hōjin Rikagaku Kenkyūsho (国立研究開発法人理化学研究所](JP) ); Akira Dohi (Kyushu University[九州大学, Kyūshū Daigaku](JP), and Giovanni Peres (University of Palermo).

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory for the agency’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Technical University of Denmark[Danmarks Tekniske Universitet](DK) and the ASI Italian Space Agency [Agenzia Spaziale Italiana](IT). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia(US) (now part of Northrop Grumman). NuSTAR’s mission operations center is at UC Berkeley(US), and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center(US). ASI provides the mission’s ground station and a mirror archive. JPL is a division of Caltech.

Quick Look: Supernova 1987A Pulsar Wind Nebula

See the full article here.

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Please help promote STEM in your local schools.

Stem Education Coalition

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory for the agency’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Technical University of Denmark[Danmarks Tekniske Universitet](DK) and the ASI Italian Space Agency [Agenzia Spaziale Italiana](IT). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia(US) (now part of Northrop Grumman). NuSTAR’s mission operations center is at UC Berkeley(US), and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center(US). ASI provides the mission’s ground station and a mirror archive. JPL is a division of Caltech.

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.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

From NASA JPL-Caltech: “NASA Satellite Spots a Mystery That’s Gone in a Flash”

From NASA JPL-Caltech

September 4, 2019
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov

This visible-light image of the Fireworks galaxy (NGC 6946) comes from the Digital Sky Survey, and is overlaid with data from NASA’s NuSTAR observatory (in blue and green). Credit: NASA/JPL-Caltech

NASA/DTU/ASI NuSTAR X-ray telescope

Pops of bright blue and green in this image of the Fireworks galaxy (NGC 6946) show the locations of extremely bright sources of X-ray light captured by NASA’s NuSTAR space observatory. Generated by some of the most energetic processes in the universe, these X-ray sources are rare compared to the many visible light sources in the background image. A new study, published in The Astrophysical Journal, offers some possible explanations for the surprise appearance of the green source near the center of the galaxy, which came into view and disappeared in a matter of weeks.

The primary objective of the NuSTAR observations was to study the supernova – the explosion of a star much more massive than our Sun – that appears as a bright blue-green spot at upper right. These violent events can briefly produce enough visible light to outshine entire galaxies consisting of billions of stars. They also generate many of the chemical elements in our universe that are heavier than iron.

The green blob near the bottom of the galaxy wasn’t visible during the first NuSTAR observation but was burning bright at the start of a second observation 10 days later. NASA’s Chandra X-ray Observatory later observed that the source – known as an ultraluminous X-ray source, or ULX – had disappeared just as quickly.

NASA/Chandra X-ray Telescope

The object has since been named ULX-4 because it is the fourth ULX identified in this galaxy. No visible light was detected with the X-ray source, a fact that most likely rules out the possibility that it is also a supernova.

“Ten days is a really short amount of time for such a bright object to appear,” said Hannah Earnshaw, a postdoctoral researcher at Caltech in Pasadena, California, and lead author on the new study. “Usually with NuSTAR, we observe more gradual changes over time, and we don’t often observe a source multiple times in quick succession. In this instance, we were fortunate to catch a source changing extremely quickly, which is very exciting.”

Possible Black Hole

The new study explores the possibility that the light came from a black hole consuming another object, such as a star. If an object gets too close to a black hole, gravity can pull that object apart, bringing the debris into a close orbit around the black hole. Material at the inner edge of this newly formed disk starts moving so fast that it heats up to millions of degrees and radiates X-rays. (The surface of the Sun, by comparison, is about 10,000 degrees Fahrenheit, or 5,500 degrees Celsius.)

Most ULXs are typically long-lived because they’re created by a dense object, like a black hole, that “feeds” on the star for an extended period of time. Short-lived, or “transient,” X-ray sources like ULX-4 are far more rare, so a single dramatic event – like a black hole quickly destroying a small star – might explain the observation.

However, ULX-4 might not be a one-off event, and the paper’s authors explored other potential explanations for this object. One possibility: The source of ULX-4 could be a neutron star. Neutron stars are extremely dense objects formed from the explosion of a star that wasn’t massive enough to form a black hole. With about the same mass as our Sun but packed into an object about the size of a large city, neutron stars can, like black holes, draw in material and create a fast-moving disk of debris. These can also generate slow-feeding ultraluminous X-ray sources, although the X-ray light is produced through slightly different processes than in ULXs created by black holes.

Neutron stars generate magnetic fields so strong they can create “columns” that channel material down to the surface, generating powerful X-rays in the process. But if the neutron star spins especially fast, those magnetic fields can create a barrier, making it impossible for material to reach the star’s surface.

“It would kind of be like trying to jump onto a carousel that’s spinning at thousands of miles per hour,” said Earnshaw.

The barrier effect would prevent the star from being a bright source of X-rays except for those times when the magnetic barrier might waver briefly, allowing material to slip through and fall onto the neutron star’s surface. This could be another possible explanation for the sudden appearance and disappearance of ULX-4. If the same source were to light up again, it might support this hypothesis.

“This result is a step towards understanding some of the rarer and more extreme cases in which matter accretes onto black holes or neutron stars,” Earnshaw said.

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. in Dulles, Virginia. NuSTAR’s mission operations center is at the University of California 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.

To read more about NASA’s NuSTAR mission, go here:

https://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.

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, 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 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.

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Please help promote STEM in your local schools.

Stem Education Coalition

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.