From AAS NOVA: “A Solar System–Sized Experiment – New Proposal for Precision Cosmology and More”

From AAS NOVA

5.26.23
Ben Cassese

NASA Pioneer 11

Using a network of faraway telescopes in the outskirts of the solar system, astronomers could measure the distance to much farther away galaxies with exquisite precision. A recent study describes how this tactic works and explores what else we could learn with such a bold experiment.

Very Very Long Baselines

Distance is notoriously a tricky quantity to measure in astrophysical contexts, and astronomers have struggled to size up the universe since Hubble first drew his famous diagram.

Edwin Hubble 1929. PNAS 2003

While they have certainly made progress over the last century, it’s natural to wonder if modern technology could enable an entirely new, more precise way to measure the gaps between galaxies.

A sketch of three detectors and a fast radio burst source. Since the wavefront is slightly curved, the same emission will strike each detector at different times. Using measurements of those differences, astronomers can back out the distance to the source. [Boone and McQuinn 2023]
Figure 1. Example of a detector configuration that can be used to measure the distance to a source from the curvature of its wave front. The signal will arrive at detector B before it is seen at detectors A or C. By comparing the arrival times at the three detectors we can infer the distance to the source. Note that we can only measure the difference in arrival times, not the distances di directly. With two detectors the distance to the source is degenerate with the angular position on the sky θ. With three detectors in two dimensions, or four detectors in three dimensions, this degeneracy is broken and the distance to the source can be inferred.

This thinking led Kyle Boone and Matthew McQuinn (University of Washington) to propose a bold new experiment. Their idea, described in a recent publication in The Astrophysical Journal Letters [below], is to scatter a fleet of radio telescopes throughout the solar system and instruct them to all observe the same flashing, repeating fast radio burst at the same time. Since each flash is emitted equally in all directions at the same time, the wavefront will be slightly curved when it arrives and will strike each satellite at a very slightly different time. Add up these nanosecond delays between each, and with some geometry you can back out the distance to the source.

Such a mission would require solving numerous intense, but feasibly surmountable, engineering challenges. Chief among these, astronomers would have to know the distances between the telescopes to within just a few centimeters, a demanding requirement considering the millions of miles separating them and the many subtle forces that affect their motion. Also, each satellite would need to nurture an ultra-precise atomic clock in the face of the unforgiving vacuum of space. But, should engineers resolve these hindrances, a constellation of four or more telescopes drifting in the outer solar system could pin down the distance to each observed flash to within 1% uncertainty.

Spanning Distances and Disciplines

The uncertainty in a measurement of the distance to a source as a function of the true distance to the source for a number of different satellite configurations. Each color represents a different possible baseline separation, and the thickness of each region marks how the uncertainty changes if the resolution of their separation varies between 0.5 and 2 cm. Note that for a source closer than 100 megaparsecs (approximately 300 million light-years), a 25 AU baseline could measure its distance to better than 1%. [Boone and McQuinn 2023]

This experiment was conceived explicitly with precision cosmology in mind, and as Boone and McQuinn show, would be demonstrably revolutionary in that field. However, should astronomers be audacious enough to build a solar system–sized hammer, there are more than a few outstanding nails the same hardware could bludgeon. Take dark matter, for example: several models suggest that invisible clumps of the stuff should occasionally fly through the solar system at high speed. This experiment would necessarily be sensitive enough to notice the slight gravitational tug of such an encounter, meaning even a non-detection of occasional jostles could help constrain our theories of dark matter’s form. Similarly, the much debated “Planet 9” would be unable to evade such an exquisitely sensitive instrument: over time, even from hundreds of AU away, any large planets lurking in the outer solar system would eventually nudge these radio telescopes out of place.

While this study may never grow into more than a thought experiment, such an exercise is constructive nonetheless and gives the astronomical community a chance to reflect on its current capabilities and muse about its future. That said, a more hopeful interpretation is to take this as a starting point for a grand, exacting, colossal mission that could one day uncover secrets of the universe, and our own backyard, all at once.

Figure 2. The triangular configuration of two detectors and the source used for timing. https://www.researchgate.net

Citation

“Solar System-scale Interferometry on Fast Radio Bursts Could Measure Cosmic Distances with Subpercent Precision,” Kyle Boone and Matthew McQuinn 2023 ApJL 947 L23.

https://iopscience.iop.org/article/10.3847/2041-8213/acc947/pdf

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “Forming the Sun on a Molecular Cloud Filament”

From AAS NOVA

5.17.23
Kerry Hensley

A complex maze of star-forming clouds make up the Circinus molecular cloud complex in this Wide-field Infrared Survey Explorer image. [NASA/JPL-Caltech/UCLA]

National Aeronautics and Space Administration Wise/NEOWISE Telescope.

The radioactive atoms found in meteorites tell a subtle and complicated story about the Sun’s birth. In a recent article, researchers translated this story to discover that our solar system could have formed in a dense molecular cloud buffeted by a supernova.

Meteorites as Messengers from the Early Solar System

In the hub–filament model of star formation, low-mass stars form in dense molecular cloud filaments, while high-mass stars form where filaments meet. [Adapted from Arzoumanian et al. 2023]

Meteorites — remnants of primordial solar system rubble that fall to Earth — contain information about the early days of the solar system, including when it formed and what elements were present at that time. Among the information contained in a meteorite comes in the form of radioactive atoms, as well as the stable atoms they decay into. These atoms are produced by massive stars and spread throughout the galaxy by winds and supernova explosions. As a result, the abundance of radioactive atoms in meteorites can tell us something about the environment in which the Sun was born, and models of solar system formation must be able to explain the abundances of these elements.

In a recent research article, Doris Arzoumanian (National Astronomical Observatory of Japan) and collaborators discussed the radioactive content of meteorites in the context of what’s known as the “hub–filament model”. In this model, Sun-like stars form along narrow, dense clouds of molecular hydrogen gas known as filaments, while massive stars form where two or more filaments meet — at a hub. Arzoumanian and coauthors suggested that the hub–filament model might provide a natural way to explain the amounts of radioactive species found in meteorites.

Forming on a Filament

Nearby high-mass stars of spectral type O and B suffuse their surroundings with high-energy photons, heating the gas. A dense filament might shield a young star from this radiation. [Adapted from Arzoumanian et al. 2023]

Radioactive atoms can be incorporated into a budding solar system in a few ways. They can be present in the cloud material from which the planetary system forms, placed there by previous generations of massive stars; they can be produced when atoms within the cloud are bombarded by high-energy charged particles from outside the galaxy; or they can be injected by a nearby massive star through winds or a supernova explosion. Based on the particular blend of radioactive atoms found in meteorites, Arzoumanian’s team favors the last explanation, though that opens a new question: how did our nascent solar system survive a supernova next door?

This is where the hub–filament model shows its usefulness. While a planetary system in the early stages of formation should be disrupted by a supernova, a dense filament could shield the young Sun and its planet-forming material. Not only does the filament protect the planetary system, it may also provide a natural way to funnel radioactive-species-rich material to the system via accretion streamers, which have been observed in young star systems.

A Supernova Solution

Massive stars add short-lived radionuclides (SLRs) like aluminum-26 to their surroundings. [Adapted from Arzoumanian et al. 2023]

Arzoumanian and collaborators delved deeper into the model by estimating the abundance of aluminum-26 (a radioactive form of aluminum) initially present in the molecular cloud where the Sun formed. They then added an extra dose of aluminum from either a supernova explosion or a nearby massive star with powerful winds. This material diffuses into the cloud and snakes onto the young star via accretion streamers.

These calculations show that a 25-solar-mass star exploding as a supernova or an even more massive (40–60 solar masses) star shaking off material through stellar winds could provide the abundance of aluminum and its daughter elements that we find in meteorites. Future simulations should explore these scenarios in more detail.

Citation

“Insights on the Sun Birth Environment in the Context of Star Cluster Formation in Hub–Filament Systems,” Doris Arzoumanian et al 2023 ApJL 947 L29.
https://iopscience.iop.org/article/10.3847/2041-8213/acc849/pdf

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “Serendipitous Supernovae”

From AAS NOVA

5.12.23
Ben Cassese

An image of the nearest supernova explosion seen in modern times, SN 1987A. [NASA, ESA; R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation); M. Mutchler and R. Avila (STScI)]

These days, astronomers find so many possible supernovae each night with automated photometric surveys that it’s impossible to follow up on all of them. Recently, however, a new article takes the first steps toward using unrelated spectroscopic surveys to fill in the gaps when luck allows.

Industrial Flash Detection

When a distant, massive star explodes as a supernova, the only sign of the monstrous violence seen from Earth is a tiny, modest flash in the night sky. Consequently, observations of these brief and easy-to-miss eruptions used to be pretty rare: astronomers would have to patiently and manually check the same patch of sky over and over again, hoping that in one of their images they’d see a bright speck of light that wasn’t there before.

But no more. With the advent of large telescopes, advanced imagers, and sophisticated software, this tedious process has been supplanted by a much more efficient workflow. These days, large surveys such as the Zwicky Transient Facility (ZTF) image huge swaths of the sky every night and automate the flash-detection process.

Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Credit: Caltech Optical Observatories.

Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, altitude 1712 m (5617 ft). Credit: Caltech.

While astronomers previously treasured each “transient” as a unique discovery, observers tapped into the data stream of these programs have the luxury to examine any number of the million or so transients detected each night.

And yet, even as these surveys churn out transients on an industrial scale, astronomers usually want to know more about each one than the fact of their existence. Historically, they’ve gone about this by recording not just images, but also spectra of each object. Unfortunately, although spectroscopic surveys have also grown immensely more efficient, they have not kept pace with their photometric counterparts, meaning that most transients discovered by ZTF will never see their spectra documented.

When Telescopes Align

Cutout images of the nine transients which were “active” according to ZTF when HETDEX happened to observe them. [Vinkó et al. 2023]

As a team led by József Vinkó (University of Texas at Austin) demonstrated in a recent article, however, sometimes we get lucky. Vinkó and collaborators looked at data collected through the Hobby-Eberly Telescope Dark Energy eXperiment (HETDEX) survey, which from 2018 to 2022 was minding its own business taking spectra of high-redshift galaxies in one corner of the sky while ZTF frantically and repeatedly snapped away at the whole northern hemisphere.

U Texas McDonald Observatory Hobby-Eberly 9.1 meter Telescope, Altitude 2,070 m (6,790 ft).

By comparing ZTF’s alerts with logs of where HETDEX was pointing each night, the team found that 538 transients went off in the exact same area the unrelated project was already observing. Even more fortuitously, nine of these transients were still glowing as HETDEX took its unrelated measurements.

The HETDEX spectrum of ZTF20aatpoos compared to the best-fitting template of a supernova spectrum. [Vinkó et al. 2023]

Out of all of these overlapping events, Vinkó and collaborators successfully identified two supernovae and managed to classify hundreds of others as either fussy active galactic nuclei or other known astronomical objects using the HETDEX spectra. While there was nothing particularly remarkable about the supernovae themselves, the circumstances of its classification are much more exciting: this discovery marks the first serendipitous classification of a transient event by HETDEX and a step forward into an era of automated transient follow-up. As more industrial-style surveys come on line in the coming decade, we can hopefully look forward to more of these lucky alignments in the near future.

Citation

“Searching for Supernovae in HETDEX Data Release 3,” József Vinkó et al 2023 ApJ 946 3.
https://iopscience.iop.org/article/10.3847/1538-4357/acbfa8/pdf

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “Searching for a Star That Survived a Supernova”

From AAS NOVA

5.3.23
Kerry Hensley

This Hubble Space Telescope image shows a supernova remnant named N 63A. [NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/Aura); Acknowledgment: Y.-H. Chu and R. M. Williams (UIUC)]

Researchers searched the remains of an exploded star for signs of its one-time companion. Though they found a suitable candidate, the star is in some ways an unlikely participant in a Type Ia supernova explosion.

A Companion to an Exploding Star

Astronomers use a class of exploding stars called Type Ia supernovae to measure the distances to other galaxies and even determine the universe’s expansion rate. In theory, all Type Ia supernovae are equally luminous, making them useful signposts. However, research increasingly suggests that Type Ia supernovae are not all alike, and their varied formation mechanisms might lead to varied brightnesses as well, which complicates their role as cosmic distance markers.

In general, Type Ia supernovae can result from two main pathways: two white dwarfs colliding (the double-degenerate scenario) or a white dwarf stealing matter from a companion star (the single-degenerate scenario). In order to determine the event that triggered a supernova, astronomers search the rubble of these cataclysmic events for signs of a companion star scurrying from the site of the explosion; neither white dwarf survives the double-degenerate scenario, while in the single-degenerate scenario the companion star might withstand the blast and live on.

And Yet It Lives

In a recent research article, a team led by Pilar Ruiz-Lapuente (Institute of Fundamental Physics, Spanish National Research Council; Institute of Cosmos Sciences of the University of Barcelona) analyzed 3,082 stars in the vicinity of a nearby supernova remnant called G272.2-3.2 to search for signs of a surviving stellar companion. If present, the companion star would 1) have a high velocity, 2) be traceable back to the center of the supernova remnant when the explosion occurred about 7,500 years ago, and 3) potentially be chemically enriched by catching debris from the exploding star.

Using data from the Gaia spacecraft, the team identified a single fast-moving star that was likely to have been in the right place at the right time. Curiously, the star is an M dwarf — the coolest, smallest type of star. And though the star didn’t show the expected chemical enrichment, Ruiz-Lapuente’s team notes that M dwarfs, unlike more massive stars, are fully convective, which means that any enriched material that falls onto the star would be mixed throughout it rather than remaining near the surface.

Small Star, Big Questions

M dwarfs don’t typically participate in Type Ia supernovae. Because of their small size, they can only transfer a small amount of mass, meaning that a white dwarf with an M-dwarf companion is more likely to undergo repeated nova outburst than a one-time, cataclysmic supernova. However, researchers suspect that the strong magnetic fields of an M dwarf and a white dwarf might help funnel material between the stars, cranking up the transfer rate and triggering a supernova. If it’s possible for M dwarfs to facilitate Type Ia supernovae, we can expect to find more cases like that of G272.2-3.2, since M dwarfs are the most common stars in the universe.

Citation

“A Possible Surviving Companion of the SN Ia in the Galactic SNR G272.2-3.2,” P. Ruiz-Lapuente et al 2023 ApJ 947 90.
https://iopscience.iop.org/article/10.3847/1538-4357/acad74/pdf

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “More Supernova Detections May Be on the Horizon with High-Energy Neutrinos”

From AAS NOVA

4.21.23
Colin Stuart

This X-ray image shows the supernova remnant Cassiopeia A. [NASA/CXC/SAO]

Astronomers can get a better view of more distant supernova explosions by searching for high-energy neutrinos, according to a study conducted by researchers at Uppsala University in Sweden.

Detecting Ghostly Particles from Collapsing Stars

University of Wisconsin IceCube Neutrino Observatory Detector at the Amundsen-Scott South Pole Station in Antarctica South Pole, elevation of 2835 metres (9301 feet).

A core-collapse supernova represents the cataclysmic end of a massive star’s life. As the star collapses, its iron core disintegrates, producing vast numbers of sub-atomic particles called neutrinos that stream outwards in unimaginable quantities — somewhere around 10 billion trillion trillion trillion trillion of them. Their outwards pressure blasts the star apart and detonates the supernova.

There are various neutrino detectors scattered across the planet, including IceCube in Antarctica. It can detect the neutrinos produced by core-collapse supernovae, which typically have energies in the mega-electronvolt range. However, the way its detectors work means that supernova neutrinos from farther away than the Magellanic Clouds — the largest satellite galaxies of the Milky Way — are too faint for it to see.

Circumstellar Collisions and Choked Jets

Nora Valtonen-Mattila and Erin O’Sullivan (both Uppsala University) think that there may be higher-energy neutrinos on offer, which would extend that range to more than a hundred million light-years. That would include supernovae in many other galaxies and local galaxy clusters.

These neutrinos — in the giga- to tera-electronvolt range — aren’t produced by the supernova itself, though. Instead Valtonen-Mattila and O’Sullivan consider two alternative production mechanisms.

Before stars go supernova they tend to eject vast amounts of material in fierce stellar winds. When the supernova detonates, the debris from the explosion hits this circumstellar material. Protons collide like they do in particle accelerators here on Earth and should produce high-energy neutrinos in the process. However, these neutrinos have yet to be observed.

A similar thing could be achieved through a jet of material that becomes trapped behind the star’s outer shell. This is called a choked jet. Ordinary particles may be trapped, but neutrinos are famously ghost-like and can stream through dense material with ease. In fact, a light-year of lead would only have fifty-fifty chance of stopping a neutrino.

Expanding Our Horizons

It’s these high-energy neutrinos from choked jets that offer the greatest possible extension to IceCube’s range, pushing it out to 277 million light-years in the northern sky and 65 million light-years in the southern sky. However, choked jets are rare, with just 1–4% of core-collapse supernovae thought to have one.

These are important considerations, particularly in light of the ongoing upgrade to IceCube-Gen2, which should be completed by 2033. Perhaps then we’ll have a clearer picture of core-collapse supernovae and the neutrinos they produce.

Citation

“Prospects for Extending the Core-collapse Supernova Detection Horizon Using High-Energy Neutrinos,” Nora Valtonen-Mattila and Erin O’Sullivan 2023 ApJ 945 98.

https://iopscience.iop.org/article/10.3847/1538-4357/acb33f/pdf
See the science paper for instructive material with images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “How to Make (and Find) Neutron Stars with a Dash of Dark Matter”

From AAS NOVA

4.12.23
Kerry Hensley

When a white dwarf captures mass from a stellar companion, it can collapse to form a neutron star. If the white dwarf contained a small amount of dark matter, the dark matter might leave a noticeable imprint on the signal of the collapse. [NASA/CXC/M.Weiss]

Extremely compact stellar remnants made of a mixture of normal matter and dark matter could explain a variety of puzzling observations, but it’s not clear exactly how these objects might form. Now, researchers have modeled a potential formation pathway and proposed a way to track them down.

Where Dark Matter and Normal Matter Meet

An infographic describing the gravitational wave event GW190814, which contained a 2.50–2.67-solar-mass object of unknown type. [LIGO Scientific Collaboration]

In some parts of the universe, where dark matter is especially dense, normal matter and dark matter might intermingle and swirl together to form stars. If these dark-matter-containing stars evolve into neutron stars — extremely dense stellar remnants about the size of a city — such an object might explain the too-heavy neutron star thought to have participated in the gravitational wave event GW190814, among other curious observations.

A team led by Ho-Sang Chan (The Chinese University of Hong Kong) has proposed that neutron stars containing a small amount of dark matter might form through a circuitous route. First, a low- to intermediate-mass star composed of normal and dark matter evolves to become a white dwarf: an Earth-sized sphere containing roughly the mass of the Sun. If this white dwarf has a giant stellar companion, it can steal some of the companion’s gas and become so massive that it collapses under its own gravity. Usually, this would lead to a supernova explosion, but under certain conditions, the white dwarf might shrink down to become a neutron star instead.

Chan and collaborators suggest that observing these events, called “accretion-induced collapse”, might yield a way to study the properties of these unusual neutron stars and of dark matter itself.

Conceptualizing Collapse

While the visible-light signature of a white dwarf collapsing to form a neutron star would be faint, Chan and collaborators have suggested that we might be able to track them down via their gravitational wave emission. The team used two-dimensional fluid dynamics simulations to study how a dark-matter-containing white dwarf would collapse into a neutron star and estimated the gravitational waves that would be emitted in the collapse.

The team set the mass of their dark matter particles to a little more than a tenth of the mass of a proton, and they considered white dwarfs containing 1–20% dark matter by mass. Additionally, they considered different rotation profiles for the stars: rigid rotation (like a spinning top) and Keplerian rotation (like planets in the solar system, the velocity is highest near the center and lowest farther out).

Observational Prospects

Normalized gravitational wave strain (related to the wave amplitude) from the collapse of Kepler-rotating white dwarfs containing, from top to bottom, 0%, 1%, 5%, 10%, and 20% dark matter by mass. [Chan et al. 2023]

Chan and collaborators found that the rotation of the star is key to determining the shape of the gravitational wave profile. For rigid rotators, there was essentially no difference between the gravitational waves emitted by stars containing dark matter and those made of solely normal matter. For Keplerian rotators, though, the presence of dark matter softens some peaks in the gravitational wave signal, and these differences are likely detectable with current gravitational wave facilities.

Hopefully, future gravitational wave observations will yield new information about these theorized neutron stars, potentially illuminating the nature of dark matter.

Citation

“Accretion-induced Collapse of Dark Matter-admixed Rotating White Dwarfs: Dynamics and Gravitational-wave Signals,” Ho-Sang Chan et al 2023 ApJ 945 133.
https://iopscience.iop.org/article/10.3847/1538-4357/acbc1d/pdf
See the science paper for instructive material with images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “First Detection of Hot Molecular Cloud Cores in the Small Magellanic Cloud”

From AAS NOVA

4.7.23
Kerry Hensley

Webb captured this near-infrared view of the star-forming region NGC 346 in the Small Magellanic Cloud. [SCIENCE: Olivia C. Jones (UK ATC), Guido De Marchi (ESTEC), Margaret Meixner (USRA)/NASA/ESA/CSA; IMAGE PROCESSING: Alyssa Pagan (STScI), Nolan Habel (USRA), Laura Lenkić (USRA), Laurie E. U. Chu (NASA Ames)]

National Aeronautics Space Agency/European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU)/ Canadian Space Agency [Agence Spatiale Canadienne](CA) James Webb Infrared Space Telescope annotated, finally launched December 25, 2021, ten years late.

Researchers have detected hot molecular cloud cores in the Small Magellanic Cloud for the first time. This discovery enhances our understanding of star formation in the nearby universe and will guide future explorations of extragalactic star-forming regions.

From Cold Cloud to Hot Core

A view of the Small Magellanic Cloud from the European Southern Observatory’s Visible and Infrared Survey Telescope for Astronomy.

Part of The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europaiche Sûdsternwarte] (EU)(CL)’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

New stars form in massive clouds of molecular hydrogen gas. As the cloud swirls, gas collects in cold, dense clumps, creating the conditions for star formation. When a massive star begins to form in one of these clumps, the gas heats up, creating a hot molecular cloud core. Researchers have previously detected hot molecular cloud cores in the Milky Way and in several nearby galaxies, but they have remained elusive in one of our nearest neighbors: the Small Magellanic Cloud.

The Small Magellanic Cloud is an interesting place to search for hot cores because this small, irregularly shaped galaxy is poor in metals — elements heavier than helium — compared to galaxies like the Milky Way. If we find hot cores in such a metal-poor galaxy, we can study how the formation of massive stars varies between metal-rich and metal-poor galaxies in the universe today. This can also help us understand star formation billions of years ago, when the universe was substantially less metal rich than it is now.

Core Candidates

Locations of the two protostars/hot core candidates, S07 and S09, within the Small Magellanic Cloud. The observations were made at infrared wavelengths. [Shimonishi et al. 2023]

Takashi Shimonishi (Niigata University) and collaborators began their search for hot cores with two sources in the Small Magellanic Cloud that had been flagged as high-mass protostars. Previous observations found that these two soon-to-be stars are swathed in clouds containing dust and ice, which suggests that the protostars might be embedded within dense gas.

The team combined new and archival data from the Atacama Large Millimeter/submillimeter Array (ALMA) to determine the properties of the gas surrounding the two sources.

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)/National Radio Astronomy Observatory/National Astronomical Observatory of Japan(JP) ALMA Observatory (CL).

They detected spectral lines from numerous molecules and molecular ions, including carbon monoxide, methanol, and sulfur dioxide. The data suggested that the gas surrounding the protostars is dense, hot (here, “hot” means warmer than 100K), and concentrated in a small region around each protostar — exactly the characteristics of a hot core!

Testing Molecular Tracers

Finding hot cores in the metal-poor Small Magellanic Cloud suggests that hot core formation is an expected part of massive star formation for galaxies with a wide range of metal abundances. Specifically, Shimonishi and collaborators have shown that hot cores can form in galaxies in which metals are 80% less abundant relative to hydrogen than they are in the gas from which the Sun formed.

Comparison of the sulfur dioxide (SO2) and methanol (CH3OH) emission for the hot core S07. The source region of the sulfur dioxide emission is more compact and warmer. [Adapted from Shimonishi et al. 2023]

Interestingly, the team found key differences between the Small Magellanic Cloud hot cores and those in other galaxies. Generally, researchers use methanol emission to find hot cores, but the methanol emission from the newly found cores was extended and cool — not what we’d expect for a hot core. Instead, it was sulfur dioxide emission that traced the cores effectively. Why might methanol be a poor core tracer in the Small Magellanic Cloud when it’s so effective in other environments? This might point to differences in how methanol and sulfur dioxide form in metal-poor hot cores, making sulfur dioxide a better indicator of hot cores in these regions.

Citation

“The Detection of Hot Molecular Cores in the Small Magellanic Cloud,” Takashi Shimonishi et al 2023 ApJL 946 L41.
https://iopscience.iop.org/article/10.3847/2041-8213/acc031/pdf
See the science paper for instructive material with images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “X Marks the Spot – A Treasure Map for High-Energy Cosmic Rays”

From AAS NOVA

3.27.23
Kerry Hensley

We’ve observed cosmic rays originating from star clusters like the one pictured here, but the precise sources of these energetic particles have been hard to pin down. [NASA/U. Virginia/INAF, Bologna, Italy/USRA/Ames/STScI/AURA]

Researchers have explored the best places to search for ultra-high-energy cosmic rays: charged particles that can travel at nearly the speed of light. New cosmic ray “treasure maps” bring us one step closer to tracking down the origins of these rare particles.

Cosmic Particle Accelerators

Cosmic rays produced by high-energy astrophysics sources ASPERA collaboration AStroParticle ERAnet.

Across the universe, cosmic rays are accelerated to extraordinary velocities. These speedy particles are mostly protons or the nuclei of helium atoms, with electrons and the nuclei of atoms heavier than helium rounding out the population. When these particles reach Earth, they can make quite a splash — the highest-energy cosmic ray ever detected had an energy of 320 exaelectronvolts (that’s 3.2×1020 electronvolts!) and earned the moniker the “Oh-My-God particle.”

Where in the universe cosmic rays reach their extreme speeds is still up for debate, though supernovae, accreting supermassive black holes, highly magnetized stellar remnants called magnetars, and gamma-ray bursts are all possible sites of cosmic-ray acceleration. Complicating the hunt for these sites is the fact that after cosmic rays are shot into space, they’re buffeted and misdirected by a tangled web of magnetic fields. As a result, where we see a cosmic ray come from might not be where it actually came from.

The loss-of-number density, aGZK, as a function of the distance of the cosmic-ray source, shown for nitrogen nuclei (dot-dashed green line) and iron nuclei (dashed orange line) with energies greater than 150 exaelectronvolts. The source distance at which 95% of particles fail to reach Earth is marked for each species with an arrow. In this simulation, the detector is sensitive to particles with masses greater than 12 atomic mass units. [Adapted from Globus et al. 2023]

Looking for Paired Particles

In a recent research article, a team led by Noémie Globus (University of California-Santa Cruz and the Institute of Physical and Chemical Research, Japan) suggested that we may be able to identify the sites of cosmic-ray acceleration by detecting two cosmic rays from the same source arriving from the same direction at the same time. Magnetic fields between the cosmic-ray source and Earth make this kind of coordination unlikely. Globus and collaborators proposed that these paired particles might arrive more often from some parts of the sky than others.

The team focused on cosmic rays with energies in excess of 150 exaelectronvolts, about two of which are caught by our cosmic ray detectors each year. In addition to considering how magnetic fields affect the passage of these particles, the team also considered which cosmic rays are most likely to survive the journey to Earth. As cosmic rays zip through space, they interact with photons from the cosmic microwave background that suffuses the universe. This interaction strips protons and neutrons away from the cosmic ray, reducing its mass and energy. This means that the distance a cosmic ray can travel before being disassembled — and therefore, the distance of the cosmic-ray sources we can detect — depends on its initial mass and energy.

Treasure Maps for Rare Cosmic Rays

An example treasure map for a nitrogen nucleus with an energy of 150 exaelectronvolts. The projection is centered on the galactic anticenter (GA), while the galactic center (GC) appears at the right and left sides. [Adapted from Globus et al. 2023]

By modeling how cosmic rays of different masses, energies, and source locations navigate the magnetic fields within the Milky Way and beyond it, Globus and coauthors determined the likeliest places on the sky to search for paired cosmic rays. These “treasure maps” show that the detection probability depends on the location of the cosmic-ray observatory, the location on the sky, and the mass of the cosmic-ray particle.

In addition to suggesting where to look, the team notes that their work can be used to guide how to look. Because a cosmic ray’s mass determines how far it can travel before being destroyed, building detectors that can measure the mass of cosmic rays reaching Earth can help us pinpoint where the particles originated.

Citation

“Treasure Maps for Detections of Extreme Energy Cosmic Rays,” Noémie Globus et al 2023 ApJ 945 12.
https://iopscience.iop.org/article/10.3847/1538-4357/acaf5f/pdf

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “Investigating Polarized Magnetar Flares”

From AAS NOVA

3.24.23
Colin Stuart

An artist’s impression of a magnetar with a cracked crust and a polar hot spot. [NASA/Goddard Space Flight Center Conceptual Image Lab]

Astronomers have observed polarized X-rays emitted by a magnetar, opening the door to understanding these extreme objects in more detail.

Magnetic Remnants

A magnetar is the remnant of the death a medium-sized star. It is a type of rapidly spinning neutron star with a typical rotation period of between one and twelve seconds. However, its magnetic field is one thousand times stronger than an ordinary neutron star. In fact, if you were to replace the Moon with a magnetar it would wipe the credit card details of everyone on Earth.

Their strong magnetic fields make magnetars prone to dramatic outbursts, emitting radiation across the electromagnetic spectrum. A magnetar’s X-ray bursts are particularly spectacular, with their X-ray flux suddenly leaping by a factor of up to a thousand.

The National Aeronautics and Space Agency/The Italian Space Agency A.S.I. [Agenzia Spaziale Italiana] (IT) IXPE spacecraft.

Focusing on Flares

It hasn’t always been clear, however, where these flares are coming from. They could spring from the crust of the magnetar itself, or they could launch from material trapped in an atmosphere around it. A team led by Silvia Zane (University College London) recently went looking for answers using the Imaging X-ray Polarimetry Explorer (IXPE). Launched at the end of 2021, it is a joint mission between NASA and the Italian Space Agency.

As its name suggests, IXPE observes the polarization of X-rays. Light is polarized if its waves all vibrate in the same plane. Zane’s team used IXPE to observe the polarization of the magnetar known as 1RXS J170849.0-40091 to see if they could work out what was corralling the X-rays.

Belts, Caps, and More

Polarization of the magnetar in different energy bands. The colors of the circles represent different detector units (DUs), and the orange stars and green crosses show the predictions for the “belt plus cap” and “cap plus cap” models, respectively. [Adapted from Zane et al. 2023]

They found that about 20% of the low-energy X-rays produced by 1RXS J170849.0-40091 are polarized, but this rises to around 80% for higher-energy X-rays.

The team ran simulations of various magnetar configurations to see if they could explain this result, settling on two possibilities. The first, which they call “belt plus cap,” has a warm region around the magnetar’s equator and a hotter atmosphere confined to a circular polar cap. The second, called “cap plus cap,” has the X-ray emission emanating from two circular spots. One is on the surface of the magnetar, and there’s a hotter atmospheric spot located in the opposite hemisphere.

Further work to untangle these two possibilities could have wider implications. Astronomers have previously suggested that magnetars are the main source of fast radio bursts, for example. Understanding why magnetars flare could help cement this link and assist astronomers in explaining these mysterious events.

Citation

A Strong X-Ray Polarization Signal from the Magnetar 1RXS J170849.0-400910, Silvia Zane et al 2023 ApJL 944 L27.
https://iopscience.iop.org/article/10.3847/2041-8213/acb703/pdf

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From AAS NOVA: “How Quickly Do We Need to Track Down the Next Neutron Star Merger?”

From AAS NOVA

3.8.23
Kerry Hensley

Artist’s impression of a kilonova: the explosion resulting from the collision of two neutron stars or a neutron star and a black hole. [Joseph Olmsted/NASA(STScI)]

Scientists may have detected violent collision between neutron star and a black hole, “All the Gold in the Universe” from The University of California-Santa Cruz 2017.

A Groundbreaking Event

In August 2017, a pair of gravitational wave detectors identified a signal from two neutron stars — the ultra-dense remnants of massive stars — colliding 130 million light-years away. In the hours that followed, a network of telescopes raced to search for the electromagnetic counterpart to the event (dubbed AT2017gf), with telescopes locking on to the source 11 hours after the merger was detected.

These observations revealed bright but rapidly fading emission at blue wavelengths in the first day after the collision was detected. Though scientists have proposed many causes for this early blue emission, two theories have risen to the top: radioactive decay of newly fused elements and heating from a shock wave. Researchers suspect that in order to distinguish between these theories, we need ultraviolet data from the first few hours after the merger is detected. We missed those critical data in 2017, with ultraviolet observations beginning 15 hours after detection — how can we ensure we capture them in the future?

Astronomers are still debating the origin of the blue-tinted emission from colliding neutron stars detected in 2017.

Stymied by missing data from the crucial first few hours of that event, researchers have determined just how quickly we’ll need to catch the next one.

Observed (symbols) and modeled (lines) light curves for AT2017gfo, the electromagnetic counterpart to the gravitational wave signal GW170817. [Adapted from Cowperthwaite et al. 2017]

When Theories Collide

Bas Dorsman (University of Amsterdam) and collaborators proposed that an ultraviolet satellite with a wide field of view could capture the necessary data next time around. To test this possibility, the team modeled the emission from an AT2017gfo–like collision of two neutron stars, finding that both theories produce ultraviolet emission that matches observations at 15 hours after the event was detected but diverges at earlier times.

Simulated ultraviolet light curves for an AT2017gfo–like neutron star merger. The orange and green lines show the results for two versions of the radioactive decay model, the blue line shows the output from the shock heating model, and the gray line shows the time at which the ultraviolet observations of AT2017gfo began. [Dorsman et al. 2023]

To estimate just how quickly we’d need to begin collecting ultraviolet data to draw firm conclusions, Dorsman and coauthors considered the capabilities of a proposed ultraviolet satellite called Dorado. Using their model results, the team simulated what a Dorado-like spacecraft would detect during the early hours of an AT2017gfo–like event. Ultimately, they found that if the ultraviolet data collection starts 1.2 hours after the event is detected — the best-case scenario based on the satellite’s capabilities — we’d be able to distinguish between the two theories for events within about 522 million light-years of Earth. As the time of first observation grows later, the events need to be closer for us to tell what drives the early blue emission: out to 424 million light-years for data starting at 3.2 hours and out to 196 million light-years for data starting at 5.2 hours.

Awaiting Spacecraft

While the team’s results show the promise of collecting early ultraviolet data, we’ll need to wait at least a few years to put the plan into practice. The Dorado spacecraft described in this work didn’t proceed beyond a concept study, but there are two similar spacecraft farther along in the selection process: the Ultraviolet Transient Astronomy Satellite (ULTRASAT; launch planned for 2026) and the Ultraviolet Explorer (UVEX; launch in 2027 or later, if selected).

ULTRASAT Israeli space satellite. Weizmann Institute of Science and Israel Space Agency.

NASA UVEX spacecraft depiction

These missions should overlap with the fifth observing run for the LIGO, Virgo, and KAGRA gravitational wave observatories, which is slated to begin in 2027.

___________________________________________________________________
LIGO-VIRGO-KAGRA-GEO 600-LIGO-India-ESA/NASA LISA

Caltech /MIT Advanced aLigo.

Caltech/MIT Advanced aLigo detector installation Livingston, LA. installation. Credit: Caltech.

Caltech/MIT Advanced aLigo Hanford, WA. installation. Credit: Caltech.

VIRGO Gravitational Wave interferometer installation, near Pisa (IT).

KAGRA Large-scale Cryogenic Gravitational Wave Telescope Project installation (JP).

GEO600 Gravitational wave detector installation, situated 20 kilometers south of Hannover close to Sarstedt near the village Ruthe. (DE)

LIGO-India installation in the Hingoli district in western India (IN).

Gravity is talking. Lisa will listen. Dialogos of Eide.

The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU)National Aeronautics and Space Administration eLISA space based, the future of gravitational wave research, due to launch in 2037.

___________________________________________________________________

LIGO Virgo Kagra Masses in the Stellar Graveyard. Credit: Frank Elavsky and Aaron Geller at Northwestern University.

___________________________________________________________________

Localizations of gravitational-wave signals detected by LIGO in 2015 (GW150914, LVT151012, GW151226, GW170104), more recently, by the LIGO-Virgo network (GW170814, GW170817) after Virgo (IT) came online in August 2018.

___________________________________________________________________

Hopefully — a decade after the detection of AT2017gfo — we’ll be able to get some answers!

Citation

“Prospects of Gravitational-wave Follow-up through a Wide-field Ultraviolet Satellite: A Dorado Case Study,” Bas Dorsman et al 2023 ApJ 944 126.
https://iopscience.iop.org/article/10.3847/1538-4357/acaa9e/pdf

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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

Please help promote STEM in your local schools.

Stem Education Coalition

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.