GW170817: The Unfolding Story of a Kilonova Told in X-rays

GW170817
Credit: X-ray: NASA/CXC/Northwestern Univ./A. Hajela et al.; Illustration: NASA/CXC/M.Weiss

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Tour of GW170817 - More Animations

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An artist’s conception illustrates the aftermath of a "kilonova," a powerful event that happens when two neutron stars merge. As described in our press release, NASA’s Chandra X-ray Observatory has been collecting data on the kilonova associated with GW170817 since shortly after it was first detected in gravitational waves by the Laser Interferometry Gravitational-wave Observatory (LIGO) and Virgo on August 17, 2017.

GW170817 was the first — and thus far the only — cosmic event where both gravitational waves and electromagnetic radiation, or light, were detected. This combination provides scientists with critical information about the physics of neutron star mergers and related phenomena, using observations at many different parts of the electromagnetic spectrum. Chandra is the only observatory still able to detect light from this extraordinary cosmic collision more than four years after the original event.

X-ray Credit: NASA/CXC/Northwestern Univ./A. Hajela et al.

Astronomers think that after neutron stars merge, the debris generates visible and infrared light from the decay of radioactive elements like platinum and gold formed in the debris from the merger. This burst of light is called a kilonova. Indeed, visible light and infrared emission were detected from GW170817 several hours after the gravitational waves.

Initially the neutron star merger likely produced a jet of high-energy particles that was not pointed directly at Earth, explaining an initial lack of X-rays seen by Chandra. The jet then slowed down and widened upon impact with surrounding gas and dust. These changes caused an increase in X-rays observed by Chandra followed by a decline in early 2018. However, since the end of 2020, the X-rays detected by Chandra have remained at a nearly constant level. The Chandra image from data taken in December 2020 and January 2021 shows X-ray emission from GW170817 and from the center of its host galaxy, NGC 4993.

A research team studying the Chandra data think this steadying of the X-ray emission comes from a shock — like a sonic boom from an airplane — as the merger debris responsible for the kilonova strikes gas around GW170817. Material heated by such a shock would glow steadily in X-rays giving a "kilonova afterglow", like Chandra has observed. The artist’s illustration shows the merger debris responsible for the kilonova in blue surrounded by a shock depicted in orange and red.

There is also an alternative explanation suggesting that the X-rays come from material falling towards a black hole that formed after the neutron stars merged. This material is depicted by a small disk in the center of the illustration. To avoid a coincidence, it is likely that only one of the two options — the kilonova afterglow or matter falling onto a black hole — is a significant source of the detected X-rays.

The two blue glowing arcs of material above and below the kilonova show where material from the now-faded jet has struck surrounding material.

To distinguish between the two explanations astronomers will keep monitoring GW170817 in X-rays and radio waves. If it is a kilonova afterglow, the radio emission is expected to get brighter over time and be detected again in the next few months or years. If the explanation involves matter falling onto a newly-formed black hole, then the X-ray output should stay steady or decline rapidly and no radio emission will be detected over time.

Researchers recently announced a source was detected in new Chandra observations performed in December 2021. Analysis of that data is ongoing. No radio detection has yet been reported.

A paper describing these results appears in the latest issue of The Astrophysical Journal Letters and is available online [link]. The authors are Aprajita Hajela (Northwestern University), Rafella Marguitti (University of California at Berkeley), Joe Bright (Berkeley), Kate Alexander (Northwestern), Brian Metzger (Columbia University), Vsevovold Nedora (University of Jena, Germany), Adithan Kathirgamarju (Berkeley), Ben Margalit (Berkeley), David Radice (Penn State University), Cristiano Guidorzi (University of Ferrara, Italy), Edo Berger (Center for Astrophysics I Harvard & Smithsonian (CfA)), Andrew MacFadyen (New York University), Dimitrios Giannios (Purdue University), Ryan Chornock (Berkeley), Ian Heywood (University of Oxford, UK), Lorenzo Sironi (Columbia), Ore Gottlieb (Tel Aviv University, Israel), Deanne Coppjans (Northwestern), Tanmoy Laskar (University of Bath, UK), Yvette Cendes (CfA), Rodolfo Barniol Duran (California State University, Sacramento), Tarraneh Eftekhari (CfA), Wen-fai Fong (Northwestern), Austin McDowell (NYU), Matt Nicholl (University of Birmingham, UK), Zhengtong Xie (University of Southampton, UK), Jonathan Zrake (Clemson University), Sebastiano Bernuzzi (University of Jena), Floor Broekgaarden (CfA), Charlie Kilpatrick (Northwestern), Giacomo Terreran (Northwestern), Ashley Villar (Columbia), Peter Blanchard (Northwestern), Sebastian Gomez (CfA), Griffin Hosseinzadeh (University of Arizona), David Jacob Matthews (Berkeley), and Jillian Rastinejad (Northwestern).

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

Fast Facts for GW170817:

Scale: Inset image is 30 arcsec across (19,000 light-years)
Category: Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 13h 09m 48.1s | Dec -23° 22´ 53.4
Constellation: Hydra
Observation Date: 7 observations from Dec 9, 2020-Jan 27, 2021
Observation Time: 53 hours
Obs. ID: 22677, 24887-24889, 23870, 24923, 24924
Instrument: ACIS
References: Hajela, A. et al., 2022, ApJL, accepted; arXiv:2104.02070
Color Code: X-ray: Purple
Distance Estimate: About 130 million light years

Source: NASA's Chandra X-Ray Observatory

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Colossal Black Holes Locked in Dance at Heart of Galaxy

Two supermassive black holes are seen orbiting each other in this artist's loopable animation. The more massive black hole, which is hundreds of millions times the mass of our sun, is shooting out a jet that changes in its apparent brightness as the duo circles each other. Astronomers found evidence for this scenario in a quasar called PKS 2131-021 after analyzing 45-years-worth of radio observations that show the system periodically dimming and brightening. The observed cyclical pattern is thought to be caused by the orbital motion of the jet. Credit: Caltech/R. Hurt (IPAC)

Artist's animation of a supermassive black hole circled by a spinning disk of gas and dust. The black hole is shooting out a relativistic jet—one that travels at nearly the speed of light. Credit: Caltech/R. Hurt (IPAC)

Three sets of radio observations of the quasar PKS 2131-02, spanning 45 years, are plotted here, with data from Owens Valley Radio Observatory (OVRO) in blue; University of Michigan Radio Astronomical Observatory (UMRAO) in brown; and Haystack Observatory in green. The observations match a simple sine wave, indicated in blue. Astronomers believe that the sine wave pattern is caused by two supermassive black holes at the heart of the quasar orbiting around each other every two years. (A period of five years was actually observed due to a Doppler effect caused by the expansion of the universe.) One of the black holes is shooting out a relativistic jet that dims and brightens periodically. Note that data from OVRO and UMRAO match for the peak in 2010, and the UMRAO and Haystack data match for the peak in 1981. The magnitudes of the peaks observed around 1980 are twice as large as those observed in recent times, presumably because more material was falling towards the black hole and being ejected at that time.

Tony Readhead / Sandra O'Neill

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Astronomers find evidence for the tightest-knit supermassive black hole duo observed to date

Locked in an epic cosmic waltz 9 billion light years away, two supermassive black holes appear to be orbiting around each other every two years. The two giant bodies each have masses that are hundreds of millions of times larger than that of our sun, and the objects are separated by a distance roughly 50 times that which separates our sun and Pluto. When the pair merge in roughly 10,000 years, the titanic collision is expected to shake space and time itself, sending gravitational waves across the universe.

A Caltech-led team of astronomers has discovered evidence for this scenario taking place within a fiercely energetic object known as a quasar. Quasars are active cores of galaxies in which a supermassive black hole is siphoning material from a disk encircling it. In some quasars, the supermassive black hole creates a jet that shoots out at near the speed of light. The quasar observed in the new study, PKS 2131-021, belongs to a subclass of quasars called blazars in which the jet is pointing toward the Earth. Astronomers already knew quasars could possess two orbiting supermassive black holes, but finding direct evidence for this has proved difficult.

Reporting in The Astrophysical Journal Letters, the researchers argue that PKS 2131-021 is now the second known candidate for a pair of supermassive black holes caught in the act of merging. The first candidate pair, within a quasar called OJ 287, orbit each other at greater distances, circling every nine years versus the two years it takes for the PKS 2131-021 pair to complete an orbit.

The telltale evidence came from radio observations of PKS 2131-021 that span 45 years. According to the study, a powerful jet emanating from one of the two black holes within PKS 2131-021 is shifting back and forth due to the pair's orbital motion. This causes periodic changes in the quasar's radio-light brightness. Five different observatories registered these oscillations, including Caltech's Owens Valley Radio Observatory (OVRO), the University of Michigan Radio Astronomy Observatory (UMRAO), MIT's Haystack Observatory, the National Radio Astronomy Observatory (NRAO), Metsähovi Radio Observatory in Finland, and NASA's Wide-field Infrared Survey Explorer (WISE) space satellite.

The combination of the radio data yields a nearly perfect sinusoidal light curve unlike anything observed from quasars before.

"When we realized that the peaks and troughs of the light curve detected from recent times matched the peaks and troughs observed between 1975 and 1983, we knew something very special was going on," says Sandra O'Neill, lead author of the new study and an undergraduate student at Caltech who is mentored by Tony Readhead, Robinson Professor of Astronomy, Emeritus.

Tightest-Knit Supermassive Black Hole Duo Found in Heart of Distant Galaxy

Ripples in Space and Time

Most, if not all, galaxies possess monstrous black holes at their cores, including our own Milky Way galaxy. When galaxies merge, their black holes "sink" to the middle of the newly formed galaxy and eventually join together to form an even more massive black hole. As the black holes spiral toward each other, they increasingly disturb the fabric of space and time, sending out gravitational waves, which were first predicted by Albert Einstein more than 100 years ago.

The National Science Foundation's LIGO (Laser Interferometer Gravitational-Wave Observatory), which is managed jointly by Caltech and MIT, detects gravitational waves from pairs of black holes up to dozens of times the mass of our sun. However, the supermassive black holes at the centers of galaxies have millions to billions of times as much mass as our sun, and give off lower frequencies of gravitational waves than those detected by LIGO.

In the future, pulsar timing arrays—which consist of an array of pulsing dead stars precisely monitored by radio telescopes—should be able to detect the gravitational waves from supermassive black holes of this heft. (The upcoming Laser Interferometer Space Antenna, or LISA, mission would detect merging black holes whose masses are 1,000 to 10 million times greater than the mass of our sun.) So far, no gravitational waves have been registered from any of these heavier sources, but PKS 2131-021 provides the most promising target yet.

In the meantime, light waves are the best option to detect coalescing supermassive black holes.

The first such candidate, OJ 287, also exhibits periodic radio-light variations. These fluctuations are more irregular, and not sinusoidal, but they suggest the black holes orbit each other every nine years. The black holes within the new quasar, PKS 2131-021, orbit each other every two years and are 2,000 astronomical units apart, about 50 times the distance between our sun and Pluto, or 10 to 100 times closer than the pair in OJ 287. (An astronomical unit is the distance between Earth and the sun.)

Revealing the 45-Year Light Curve

Readhead says the discoveries unfolded like a "good detective novel," beginning in 2008 when he and colleagues began using the 40-meter telescope at OVRO to study how black holes convert material they "feed" on into relativistic jets, or jets traveling at speeds up to 99.98 percent that of light. They had been monitoring the brightness of more than 1,000 blazars for this purpose when, in 2020, they noticed a unique case.

"PKS 2131 was varying not just periodically, but sinusoidally," Readhead says. "That means that there is a pattern we can trace continuously over time." The question, he says, then became how long has this sine wave pattern been going on?

The research team then went through archival radio data to look for past peaks in the light curves that matched predictions based on the more recent OVRO observations. First, data from NRAO's Very Long Baseline Array and UMRAO revealed a peak from 2005 that matched predictions. The UMRAO data further showed there was no sinusoidal signal at all for 20 years before that time—until as far back as 1981 when another predicted peak was observed.

"The story would have stopped there, as we didn't realize there were data on this object before 1980," Readhead says. "But then Sandra picked up this project in June of 2021. If it weren't for her, this beautiful finding would be sitting on the shelf."

O'Neill began working with Readhead and the study's second author Sebastian Kiehlmann, a postdoc at the University of Crete and former staff scientist at Caltech, as part of Caltech's Summer Undergraduate Research Fellowship (SURF) program. O'Neill began college as a chemistry major but picked up the astronomy project because she wanted to stay active during the pandemic. "I came to realize I was much more excited about this than anything else I had worked on," she says.

With the project back on the table, Readhead searched through the literature and found that the Haystack Observatory had made radio observations of PKS 2131-021 between 1975 and 1983. These data revealed another peak matching their predictions, this time occurring in 1976.

"This work shows the value of doing accurate monitoring of these sources over many years for performing discovery science," says co-author Roger Blandford, Moore Distinguished Scholar in Theoretical Astrophysics at Caltech who is currently on sabbatical from Stanford University.

Like Clockwork

Readhead compares the system of the jet moving back and forth to a ticking clock, where each cycle, or period, of the sine wave corresponds to the two-year orbit of the black holes (though the observed cycle is actually five years due to light being stretched by the expansion of the universe). This ticking was first seen in 1976 and it continued for eight years before disappearing for 20 years, likely due to changes in the fueling of the black hole. The ticking has now been back for 17 years.

"The clock kept ticking," he says, "The stability of the period over this 20-year gap strongly suggests that this blazar harbors not one supermassive black hole, but two supermassive black holes orbiting each other."

The physics underlying the sinusoidal variations were at first a mystery, but Blandford came up with a simple and elegant model to explain the sinusoidal shape of the variations.

"We knew this beautiful sine wave had to be telling us something important about the system," Readhead says. "Roger's model shows us that it is simply the orbital motion that does this. Before Roger worked it out, nobody had figured out that a binary with a relativistic jet would have a light curve that looked like this."

Says Kiehlmann: "Our study provides a blueprint for how to search for such blazar binaries in the future."

The Astrophysical Journal Letters study titled "The Unanticipated Phenomenology of the Blazar PKS 2131-021: A Unique Super-Massive Black hole Binary Candidate" was funded by Caltech, the Max Planck Institute for Radio Astronomy, NASA, National Science Foundation (NSF), the Academy of Finland, the European Research Council, ANID-FONDECYT (Agencia Nacional de Investigación y Desarrollo-Fondo Nacional de Desarrollo Científico y Tecnológico in Chile), the Natural Science and Engineering Council of Canada, the Foundation for Research and Technology – Hellas in Greece, the Hellenic Foundation for Research and Innovation in Greece, and the University of Michigan. Other Caltech authors include Tim Pearson, Vikram Ravi, Kieran Cleary, Matthew Graham, and Tom Prince. Other authors from the Jet Propulsion Laboratory, which is managed by Caltech for NASA, include Michele Vallisneri and Joseph Lazio.

Written by Whitney Clavin

Contact:

Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

 

 

Source: Caltech - California Institute of Technology/News

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Astronomers find largest radio galaxy ever

This fiery pair of plasma plumes, named Alcyoneus, forms the largest known structure made by a galaxy.
c) Martijn Oei et al.

A supermassive black hole lurks in the centre of many galaxies, which slows down the birth of new stars and therefore strongly influences the lifecycle of the galaxy as a whole. Sometimes, this leads to tumultuous scenes: the black hole can create two jet streams, that catapult the building material for baby stars out of the galaxy at almost the speed of light. In this violent process, the stardust heats up so much that it dissolves into plasma and glows in radio light. The international team of researchers from Leiden (The Netherlands), Hertfordshire, Oxford (both UK), and Paris (France) have now collected that light – with the pan-European LOFAR telescope, whose epicentre lies in a marshy Dutch ‘radio-dark’ nature reserve, where your smartphone deliberately loses signal. 

Record length

The picture of the two plasma plumes is special, because never before scientists saw a structure this big made by a single galaxy. The discovery shows that the sphere of influence of some galaxies reaches far from their direct environment. How far, exactly? That is hard to determine. Astronomical pictures are taken from a single viewpoint (Earth), and therefore do not contain depth.[1] As a result, scientists can only measure a part of the radio galaxy length: a low estimate of the total length. But even that lower bound, of more than 16 million light-years, is gargantuan, and comparable to one hundred Milky Ways in a row. Or: consider every living insect on Earth, and blow up each of them to the size of Mount Everest, before asking them to stand in a row.[2] This row also suffices (flying off not allowed).

Visible with the naked radio eye

Because Earth does not occupy a special place in the Universe, it was never very likely that such a largest galactic structure would reside in our own backyard. And indeed: the radio giant is three billion light-years away from us. Despite that mind-boggling distance, the giant looms as large in the sky as the Moon – an indication that the structure had to have a record length. The fact that the radio eyes of the LOFAR telescope only saw the giant just now, is because the plumes are relatively faint. By reprocessing a set of existing images in such a way that subtle patterns stood out, the scientists were suddenly able to spot the giant.

The giant Alcyneus

The researchers named the giant structure Alcyoneus, after the son of Ouranos, the Greek primordial god of the sky. This mythological Alcyoneus was a giant that fought against Heracles and the Olympian gods for supremacy over the cosmos. In the world-famous Pergamon Altar in Berlin, a sculpture of this Alcyoneus is carved out.

Ghostly dance

Alcyoneus’ plumes possibly reveal information about the mostly elusive filaments of the Cosmic Web. The Cosmic Web is another name for the contemporary, grown-up Universe, that looks like a network of threads and nodes that astronomers call filaments and clusters, respectively. The galaxies in filaments and clusters are clearly visible themselves, but detecting the medium between galaxies has only been successful in clusters – barring a handful of exceptions. Could Alcyoneus change this? Because Alcyoneus, just like the Milky Way, inhabits a filament, its plumes feel a headwind while moving through the medium. This subtly changes the direction and shape of the plumes: they perform a slow dance with an invisible partner. For many years, scientists have proposed that the shapes of and pressures in the plumes of radio galaxies could relate to filament properties, but never before did they find an example where that connection is as plausible as with Alcyoneus. Namely, Alcyoneus’ plumes are so big and rarefied that the surrounding medium can relatively easily mold them.

Black hole are cosmic mainstays

The Cosmic Web retains its form because the attractive force of gravity is compensated by the heat pressure of the medium in filaments and clusters. In the past two decennia it has become clear that the glowing stardust that jet streams eject from galaxies, keeps the Web warm. In this way, the central black holes in galaxies contribute to sustain the large-scale structure of our Universe. That is extra noteworthy because black holes are very small compared to filaments and clusters. It is as if something the size of a marble regulates the Earth’s temperature. Marvellous thermometres, in short.

Mysterious origin

What has given Alcyoneus its record length, remains a mystery for now. The scientists first thought of an exceptionally massive black hole, an extensive stellar population (and so a lot of stardust), or extraordinarily powerful jet streams. Surprisingly enough, Alcyoneus appears to be less than average on all these aspects compared to its smaller sisters and brothers. In the times ahead, the team will therefore now investigate whether the environments of radio galaxies could explain the growth of giants instead.

Paper:

The discovery of a radio galaxy of at least 5 Mpc. By: Martijn S.S.L. Oei, Reinout J. van Weeren, Martin J. Hardcastle, Andrea Botteon, Tim W. Shimwell, Pratik Dabhade, Aivin R.D.J.G.I.B. Gast, Huub J.A. Röttgering, Marcus Brüggen, Cyril Tasse, Wendy L. Williams, Aleksandar Shulevski. Accepted for publication in: Astronomy & Astrophysics (preprint).

Original press release: www.astronomie.nl

Source:  ASTRON-Netherlands Institute for Radio Astronomy/News

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Galaxy Collision Creates 'Space Triangle' in New Hubble Image

A spectacular head-on collision between two galaxies fueled the unusual triangular-shaped star-birthing frenzy, as captured in a new image from NASA's Hubble Space Telescope. The interacting galaxy duo is collectively called Arp 143. The pair contains the glittery, distorted, star-forming spiral galaxy NGC 2445 at right, along with its less flashy companion, NGC 2444 at left.

Astronomers suggest that the galaxies passed through each other, igniting the uniquely shaped star-formation firestorm in NGC 2445, where thousands of stars are bursting to life on the right-hand side of the image. This galaxy is awash in starbirth because it is rich in gas, the fuel that makes stars. However, it hasn't yet escaped the gravitational clutches of its partner NGC 2444, shown on the left side of the image. The pair is waging a cosmic tug-of-war, which NGC 2444 appears to be winning. The galaxy has pulled gas from NGC 2445, forming the oddball triangle of newly minted stars.

Credits: Image: NASA, ESA, STScI, Julianne Dalcanton Center for Computational Astrophysics, Flatiron Inst. / UWashington).  Image Processing: Joseph DePasquale (STScI)

Release Images

A spectacular head-on collision between two galaxies fueled the unusual triangular-shaped star-birthing frenzy, as captured in a new image from NASA's Hubble Space Telescope.

The interacting galaxy duo is collectively called Arp 143. The pair contains the glittery, distorted, star-forming spiral galaxy NGC 2445 at right, along with its less flashy companion, NGC 2444 at left.

Astronomers suggest that the galaxies passed through each other, igniting the uniquely shaped star-formation firestorm in NGC 2445, where thousands of stars are bursting to life on the right-hand side of the image. This galaxy is awash in starbirth because it is rich in gas, the fuel that makes stars. However, it hasn't yet escaped the gravitational clutches of its partner NGC 2444, shown on the left side of the image. The pair is waging a cosmic tug-of-war, which NGC 2444 appears to be winning. The galaxy has pulled gas from NGC 2445, forming the oddball triangle of newly minted stars.

"Simulations show that head-on collisions between two galaxies is one way of making ringsof new stars," said astronomer Julianne Dalcanton of the Flatiron Institute's Center for Computational Astrophysics in New York and the University of Washington in Seattle. "Therefore, rings of star formation are not uncommon. However, what's weird about this system is that it's a triangle of star formation. Part of the reason for that shape is that these galaxies are still so close to each other and NGC 2444 is still holding on to the other galaxy gravitationally. NGC 2444 may also have an invisible, hot halo of gas that could help to pull NGC 2445's gas away from its nucleus. So, they're not completely free of each other yet and their unusual interaction is distorting the ring into this triangle."

NGC 2444 is also responsible for yanking taffy-like strands of gas from its partner, stoking the streamers of young, blue stars that appear to form a bridge between the two galaxies.

These streamers are among the first in what appears to be a wave of star formation that started on NGC 2445's outskirts and continued inward. Researchers estimate the streamer stars were born between about 50 million and 100 million years ago. But these infant stars are being left behind as NGC 2445 continues to pull slowly away from NGC 2444.

Stars no older than 1 million to 2 million years are forming closer to the center of NGC 2445. Hubble's keen sharpness reveals some individual stars. They are the brightest and most massive in the galaxy. Most of the brilliant blue clumps are groupings of stars. The pink blobs are giant, young star clusters still enshrouded in dust and gas.

Although most of the action is happening in NGC 2445, it doesn't mean the other half of the interacting pair has escaped unscathed. The gravitational tussle has stretched NGC 2444 into an odd shape. The galaxy contains old stars and no new starbirth because it lost its gas long ago, well before this galactic encounter.

"This is a nearby example of the kinds of interactions that happened long ago. It's a fantastic sandbox to understand star formation and interacting galaxies," said Elena Sabbi of the Space Telescope Science Institute in Baltimore, Maryland.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Credits:

Writer: Donna Weaver

Release: NASA, ESA, STScI, Julianne Dalcanton (Center for Computational Astrophysics/Flatiron Inst., UWashington)

Media Contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Science Contact:

Julianne Dalcanton
Center for Computational Astrophysics, FlatIron Institute, New York, New York
University of Washington, Seattle, Washington

Contact Us: Direct inquiries to the News Team.

 

Source: HubbleSsite/News

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Astronomers Discover Widest Separation of Brown Dwarf Pair to Date

An artist’s rendition of a binary system of brown dwarfs like cwise j014611.20-050850.0ab.
Credit: William Pendrill

Maunakea, Hawaiʻi – A team of astronomers has discovered a rare pair of brown dwarfs that has the widest separation of any brown dwarf binary system found to date.

“Because of their small size, brown dwarf binary systems are usually very close together,” said Emma Softich, an undergraduate astrophysics student at the Arizona State University (ASU) School of Earth and Space Exploration and lead author of the study. “Finding such a widely separated pair is very exciting.”

The gravitational force between a pair of brown dwarfs is lower than for a pair of stars with the same separation, so wide brown dwarf binaries are more likely to break up over time, making this pair of brown dwarfs an exceptional find.

The study, which is based on observations the University of California San Diego (UC San Diego) Cool Star Lab conducted with W. M. Keck Observatory on Maunakea, Hawaiʻi Island, is published in today’s issue of The Astrophysical Journal Letters.                           

Using Keck Observatory’s Near-Infrared Echellette Spectrometer, or NIRES instrument,  members of the UC San Diego Cool Star Lab, including Physics Professor Adam Burgasser and graduate students Christian Aganze and Dino Hsu, obtained infrared spectra of the brown dwarf binary system, called CWISE J014611.20-050850.0AB. The data revealed the two brown dwarfs are about 12 billion miles apart, or three times the separation of Pluto from the Sun. This distance confirms the unusual brown dwarf couple breaks the record for having the widest separation from each other.

“Keck’s exceptional sensitivity in the infrared with this instrument was critical for our measurements,” said co-author Burgasser, who leads the Cool Star Lab. “The secondary brown dwarf of this system is exceptionally faint, but with Keck we were able to obtain good enough spectral data to classify both sources and identify them as members of a rare class of blue L dwarfs.”

“Wide, low-mass systems like CWISE J014611.20-050850.0AB are usually disrupted early on in their lifetimes, so the fact that this one has survived until now is pretty remarkable,” said co-author Adam Schneider of the U.S. Naval Observatory, Flagstaff Station and George Mason University.

WISE (left) and the Dark Energy Survey Collaboration (DES) (right) images of CWISE J0146-0508AB. In the lower-resolution WISE image, the pair are blended into a single point-source, while two distinct entities are visible in the higher-resolution DES image. The reddish hue of both objects in the DES image shows that they emit much of their light in the infrared, a trait typical of brown dwarfs. Credit: WISE/DES/Softich et al.

Brown dwarfs are celestial objects that are smaller than a normal star. These objects are not massive enough to sustain nuclear fusion and shine like normal stars, but are hot enough to radiate energy.

Many brown dwarfs have been discovered with data from NASA’s Wide-field Infrared Survey Explorer (WISE) via the Backyard Worlds: Planet 9 citizen science project, which solicits help from the public to search the WISE image data bank to find brown dwarfs and low-mass stars, some of the Sun’s nearest neighbors.

For this study, the researchers inspected images of Backyard Worlds discoveries, where companion brown dwarfs may have been overlooked. In doing so, they discovered the rare CWISE J014611.20 050850.0AB brown dwarf binary system.

Softich went through about 3,000 brown dwarfs from Backyard Worlds one by one and compared the WISE images to other survey images, looking for evidence of a brown dwarf companion to the original target. The team then used data from the Dark Energy Survey (DES) to confirm that it was indeed a brown dwarf pair.

They then used Keck Observatory’s NIRES to confirm the brown dwarfs have spectral types L4 and L8, and that they are at an estimated distance of about 40 parsecs, or 130.4 light-years from Earth, with a projected separation of 129 astronomical units, or 129 times the distance between the Sun and the Earth.

The team hopes this discovery will allow astronomers the chance to study brown dwarf binary systems and to develop models and procedures that will help in recognizing more of them in the future.

“Binary systems are used to calibrate many relations in astronomy, and this newly discovered pair of brown dwarfs will present an important test of brown dwarf formation and evolution models,” said co-author Jennifer Patience, Softich’s adviser at ASU.

Source: W. M. Keck Observatory

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About NIRES

The Near Infrared Echellette Spectrograph (NIRES) is a prism cross-dispersed near-infrared spectrograph built at the California Institute of Technology by a team led by Chief Instrument Scientist Keith Matthews and Prof. Tom Soifer. Commissioned in 2018, NIRES covers a large wavelength range at moderate spectral resolution for use on the Keck II telescope and observes extremely faint red objects found with the Spitzer and WISE infrared space telescopes, as well as brown dwarfs, high-redshift galaxies, and quasars. Support for this technology was generously provided by the Mt. Cuba Astronomical Foundation.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaiʻi feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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Studying the Next Interstellar Interloper with Webb

Artist's Impression of 1I/'Oumuamua
Credits: Artwork: NASA, ESA, Joseph Olmsted (STScI), Frank Summers (STScI)

Interstellar Comet 2I/Borisov
Credits: IMAGE: NASA, ESA, David Jewitt (UCLA)
Image Processing: Joseph DePasquale (STScI)
Release Images

One of the most exciting findings in planetary science in recent years is the discovery of interstellar objects passing through our solar system. So far, astronomers have confirmed only two of these interlopers from other star systems — 1I/'Oumuamua in 2017 and 2I/Borisov in 2018 — but many, many more are thought to exist. Scientists have had only limited ability to study these objects once discovered, but all of that is about to change with NASA's James Webb Space Telescope.

"The supreme sensitivity and power of Webb now present us with an unprecedented opportunity to investigate the chemical composition of these interstellar objects and find out so much more about their nature: where they come from, how they were made, and what they can tell us about the conditions present in their home systems," explained Martin Cordiner, principal investigator of a Webb Target of Opportunity program to study the composition of an interstellar object.

"The ability to study one of these and find out its composition — to really see material from around another planetary system close up — is truly an amazing thing," said Cordiner, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland and The Catholic University of America. The first two interstellar objects detected were very different: One was very comet-like, and one was not. Cordiner and his team hope to find out how unique those objects were and whether they're representative of the broader population of interstellar objects.

Triggering Process

Astronomers are constantly monitoring various sources of information, ranging from amateur observers to professional observatories, in the hopes of finding the next interstellar interloper. When the next such object is first detected, scientists won't immediately be certain if it's an interstellar object. They'll need additional observations over a period of days, weeks, or even months to confirm it — depending on its brightness.

Once they have confirmation that the object came from outside the solar system based on its "hyperbolic" orbit, and they are certain the object didn't come from the outer reaches of our own solar system or the Oort cloud, they can calculate the trajectory of the object across the sky. If that trajectory intersects with Webb's viewing field, Cordiner and his team will make the observations.

The Science

The team will use Webb's spectroscopic capabilities in both the near-infrared and mid-infrared bands to study two different aspects of the interstellar object. First, using the Near-Infrared Spectrograph (NIRSpec), they will analyze the chemical fingerprints of gases released by the object as any ices that might be present are vaporized by our Sun's heat. Second, with the Mid-Infrared Instrument (MIRI), they will observe any dust that the object is producing — small, microscopic particles; larger grains; and even pebbles that may be lifted off the surface and surrounding the object.

With its high spectral resolution, NIRSpec can pick out the emission from individual gases, allowing the team to detect specific molecules such as water, methanol, formaldehyde, carbon dioxide, carbon monoxide, and methane. MIRI, in the mid-infrared, is more tuned to the heat spectrum produced by solid particles, such as dust grains or the object's nucleus.

Powerful New Insights

In our own solar system, comets are icy remnants from the era of planet formation around our Sun, so they can provide unique insight into the chemical conditions present in the earliest history of our solar system. This Webb program has the ability to reveal — for the first time — similarly powerful insights into the chemistry of the formation of planets around other stars. 

 

Astronomers don't fully understand the exact chemical processes involved in forming planets. For example, how does a planet arise from simple chemical ingredients? Does it happen in the same way around all stars? Was there anything peculiar about the way our own planets formed around our Sun, compared with how they form around other stars elsewhere in the galaxy? If scientists can get proof of the chemical conditions present in other planetary systems by observing an interstellar object and seeing what it's made of, then they can get a much clearer picture of the true extent of chemistry that's possible in those other planetary systems.

A New Window with Webb

Interstellar objects have not been observed before in these important near- and mid-infrared wavelength ranges, so the possibilities for new discoveries are quite profound. With trillions and trillions of interstellar objects buzzing around the galaxy, the team doesn't know what they are going to find, but they know that it will be fascinating.

"With Webb, we can do really interesting science at much fainter magnitudes or brightnesses," explained teammate Cristina Thomas, an assistant professor of astronomy at Northern Arizona University. "Also, we've never been able to observe interstellar objects in this region of the infrared. It opens a lot of opportunities for the different compositional signatures that we're interested in. That's going to be a huge boon for us!"

The James Webb Space Telescope is the world's premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Credits:

Media Contact:

Ann Jenkins
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Contact Us: Direct inquiries to the News Team.

Source: James Webb Space Telescope/News

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NASA’s IXPE Sends First Science Image

This image of the supernova remnant Cassiopeia A combines some of the first X-ray data collected by NASA’s Imaging X-ray Polarimetry Explorer, shown in magenta, with high-energy X-ray data from NASA’s Chandra X-Ray Observatory, in blue. Credits: NASA/CXC/SAO/IXPE

This image from NASA’s Imaging X-ray Polarimetry Explorer maps the intensity of X-rays coming from the observatory’s first target, the supernova remnant Cassiopeia A. Colors ranging from cool purple and blue to red and hot white correspond with the increasing brightness of the X-rays. The image was created using X-ray data collected by IXPE between Jan. 11-18. Credits: NASA

In time for Valentine’s Day, NASA’s Imaging X-Ray Polarimetry Explorer which launched Dec. 9, 2021, has delivered its first imaging data since completing its month-long commissioning phase.

All instruments are functioning well aboard the observatory, which is on a quest to study some of the most mysterious and extreme objects in the universe.

IXPE first focused its X-ray eyes on Cassiopeia A, an object consisting of the remains of a star that exploded in the 17^th century. The shock waves from the explosion have swept up surrounding gas, heating it to high temperatures and accelerating cosmic ray particles to make a cloud that glows in X-ray light. Other telescopes have studied Cassiopeia A before, but IXPE will allow researchers to examine it in a new way.

In the image above, the saturation of the magenta color corresponds to the intensity of X-ray light observed by IXPE. It overlays high energy X-ray data, shown in blue, from NASA’s Chandra X-Ray Observatory. Chandra and IXPE, with different kinds of detectors, capture different levels of angular resolution, or sharpness. An additional version of this image is available showing only IXPE data. These images contain IXPE data collected from Jan. 11 to 18.

After Chandra launched in 1999, its first image was also of Cassiopeia A. Chandra’s X-ray imagery revealed, for the first time, that there is a compact object in the center of the supernova remnant, which may be a black hole or neutron star.

“The IXPE image of Cassiopeia A is as historic as the Chandra image of the same supernova remnant,” said Martin C. Weisskopf, the IXPE principal investigator based at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “It demonstrates IXPE’s potential to gain new, never-before-seen information about Cassiopeia A, which is under analysis right now.”

A key measurement that scientists will make with IXPE is called polarization, a way of looking at how X-ray light is oriented as it travels through space. The polarization of light contains clues to the environment where the light originated. IXPE’s instruments also measure the energy, the time of arrival, and the position in the sky of the X-rays from cosmic sources. 

“The IXPE image of Cassiopeia A is bellissima, and we look forward to analyzing the polarimetry data to learn even more about this supernova remnant,” said Paolo Soffitta, the Italian principal investigator for IXPE at the National Institute of Astrophysics (INAF) in Rome.

With polarization data from Cassiopeia A, IXPE will allow scientists to see, for the first time, how the amount of polarization varies across the supernova remnant, which is about 10 light-years in diameter. Researchers are currently working with the data to create the first-ever X-ray polarization map of the object. This will reveal new clues about how X-rays are produced at Cassiopeia A.

“IXPE's future polarization images should unveil the mechanisms at the heart of this famous cosmic accelerator,” said Roger Romani, an IXPE co-investigator at Stanford University. “To fill in some of those details, we’ve developed a way to make IXPE’s measurements even more precise using machine learning techniques. We’re looking forward to what we’ll find as we analyze all the data.”

IXPE launched on a Falcon 9 rocket from Cape Canaveral, and now orbits 370 miles (600 kilometers) above Earth’s equator. The mission is a collaboration between NASA and the Italian Space Agency with partners and science collaborators in 12 countries. Ball Aerospace, headquartered in Broomfield, Colorado, manages spacecraft operations.

https://www.nasa.gov/mission_pages/ixpe/index.html

 

Elizabeth Landau
NASA Headquarters
elizabeth.r.landau@nasa.gov
202-358-0845

Molly Porter
NASA's Marshall Space Flight Center
molly.a.porter@nasa.gov
256-424-5158

Source: NASA/Imaging X-Ray Polarimetry Explorer (IXPE)

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Supermassive black hole caught hiding in a ring of cosmic dust

PR Image eso2203a

Galaxy Messier 77 and close-up view of its active centre 

 

PR Image eso2203b

A close-up view of Messier 77’s active galactic nucleus

 

PR Image eso2203c

Dazzling galaxy Messier 77

 

PR Image eso2203d

Artist’s impression of the active galactic nucleus of Messier 77

 

PR Image eso2203e

The active galaxy Messier 77 in the constellation of Cetus 

 

PR Image eso2203f

Wide-field image of the sky around Messier 77

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Video

PR Video eso2203b

Artist’s animation of the active galactic nucleus of Messier 77 

 

PR Video eso2203c

The Unified Model of active galactic nuclei

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The European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI) has observed a cloud of cosmic dust at the centre of the galaxy Messier 77 that is hiding a supermassive black hole. The findings have confirmed predictions made around 30 years ago and are giving astronomers new insight into “active galactic nuclei”, some of the brightest and most enigmatic objects in the universe.

Active galactic nuclei (AGNs) are extremely energetic sources powered by supermassive black holes and found at the centre of some galaxies. These black holes feed on large volumes of cosmic dust and gas. Before it is eaten up, this material spirals towards the black hole and huge amounts of energy are released in the process, often outshining all the stars in the galaxy.

Astronomers have been curious about AGNs ever since they first spotted these bright objects in the 1950s. Now, thanks to ESO’s VLTI, a team of researchers, led by Violeta Gámez Rosas from Leiden University in the Netherlands, have taken a key step towards understanding how they work and what they look like up close. The results are published today in Nature.

By making extraordinarily detailed observations of the centre of the galaxy Messier 77, also known as NGC 1068, Gámez Rosas and her team detected a thick ring of cosmic dust and gas hiding a supermassive black hole. This discovery provides vital evidence to support a 30-year-old theory known as the Unified Model of AGNs.

Astronomers know there are different types of AGN. For example, some release bursts of radio waves while others don’t; certain AGNs shine brightly in visible light, while others, like Messier 77, are more subdued. The Unified Model states that despite their differences, all AGNs have the same basic structure: a supermassive black hole surrounded by a thick ring of dust.

According to this model, any difference in appearance between AGNs results from the orientation at which we view the black hole and its thick ring from Earth. The type of AGN we see depends on how much the ring obscures the black hole from our view point, completely hiding it in some cases.

Astronomers had found some evidence to support the Unified Model before, including spotting warm dust at the centre of Messier 77. However, doubts remained about whether this dust could completely hide a black hole and hence explain why this AGN shines less brightly in visible light than others.

“The real nature of the dust clouds and their role in both feeding the black hole and determining how it looks when viewed from Earth have been central questions in AGN studies over the last three decades,” explains Gámez Rosas. “Whilst no single result will settle all the questions we have, we have taken a major step in understanding how AGNs work.”

The observations were made possible thanks to the Multi AperTure mid-Infrared SpectroScopic Experiment (MATISSE) mounted on ESO’s VLTI, located in Chile’s Atacama Desert. MATISSE combined infrared light collected by all four 8.2-metre telescopes of ESO’s Very Large Telescope (VLT) using a technique called interferometry. The team used MATISSE to scan the centre of Messier 77, located 47 million light-years away in the constellation Cetus.

“MATISSE can see a broad range of infrared wavelengths, which lets us see through the dust and accurately measure temperatures. Because the VLTI is in fact a very large interferometer, we have the resolution to see what’s going on even in galaxies as far away as Messier 77. The images we obtained detail the changes in temperature and absorption of the dust clouds around the black hole,” says co-author Walter Jaffe, a professor at Leiden University.

Combining the changes in dust temperature (from around room temperature to about 1200 °C) caused by the intense radiation from the black hole with the absorption maps, the team built up a detailed picture of the dust and pinpointed where the black hole must lie. The dust — in a thick inner ring and a more extended disc — with the black hole positioned at its centre supports the Unified Model. The team also used data from the Atacama Large Millimeter/submillimeter Array, co-owned by ESO, and the National Radio Astronomy Observatory’s Very Long Baseline Array to construct their picture.

“Our results should lead to a better understanding of the inner workings of AGNs,” concludes Gámez Rosas. “They could also help us better understand the history of the Milky Way, which harbours a supermassive black hole at its centre that may have been active in the past.”  

The researchers are now looking to use ESO’s VLTI to find more supporting evidence of the Unified Model of AGNs by considering a larger sample of galaxies.

Team member Bruno Lopez, the MATISSE Principal Investigator at the Observatoire de la Côte d’Azur in Nice, France, says: “Messier 77 is an important prototype AGN and a wonderful motivation to expand our observing programme and to optimise MATISSE to tackle a wider sample of AGNs."

ESO’s Extremely Large Telescope (ELT), set to begin observing later this decade, will also aid the search, providing results that will complement the team’s findings and allow them to explore the interaction between AGNs and galaxies.

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More Information

This research was presented in the paper “Thermal imaging of dust hiding the black hole in the Active Galaxy NGC 1068” (doi: 10.1038/s41586-021-04311-7) to appear in Nature.

The team is composed of Violeta Gámez Rosas (Leiden Observatory, Leiden University, Netherlands [Leiden]), Jacob W. Isbell (Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), Walter Jaffe (Leiden), Romain G. Petrov (Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France [OCA]), James H. Leftley (OCA), Karl-Heinz Hofmann (Max Planck Institute for Radio Astronomy, Bonn, Germany [MPIfR]), Florentin Millour (OCA), Leonard Burtscher (Leiden), Klaus Meisenheimer (MPIA), Anthony Meilland (OCA), Laurens B. F. M. Waters (Department of Astrophysics/IMAPP, Radboud University, the Netherlands; SRON, Netherlands Institute for Space Research, the Netherlands), Bruno Lopez (OCA), Stéphane Lagarde (OCA), Gerd Weigelt (MPIfR), Philippe Berio (OCA), Fatme Allouche (OCA), Sylvie Robbe-Dubois (OCA), Pierre Cruzalèbes (OCA), Felix Bettonvil (ASTRON, Dwingeloo, the Netherlands [ASTRON]), Thomas Henning (MPIA), Jean-Charles Augereau (Univ. Grenoble Alpes, CNRS, Institute for Planetary sciences and Astrophysics, France [IPAG]), Pierre Antonelli (OCA), Udo Beckmann (MPIfR), Roy van Boekel (MPIA), Philippe Bendjoya (OCA), William C. Danchi (NASA Goddard Space Flight Center, Greenbelt, USA), Carsten Dominik (Anton Pannekoek Institute for Astronomy, University of Amsterdam, The Netherlands [API]), Julien Drevon (OCA), Jack F. Gallimore (Department of Physics and Astronomy, Bucknell University, Lewisburg, Pennsylvania, USA), Uwe Graser (MPIA), Matthias Heininger (MPIfR), Vincent Hocdé (OCA), Michiel Hogerheijde (Leiden; API), Josef Hron (Department of Astrophysics, University of Vienna, Austria), Caterina M.V. Impellizzeri (Leiden), Lucia Klarmann (MPIA), Elena Kokoulina (OCA), Lucas Labadie (1st Institute of Physics, University of Cologne, Germany), Michael Lehmitz (MPIA), Alexis Matter (OCA), Claudia Paladini (European Southern Observatory, Santiago, Chile [ESO-Chile]), Eric Pantin (Centre d'Etudes de Saclay, Gif-sur-Yvette, France), Jörg-Uwe Pott (MPIA), Dieter Schertl (MPIfR), Anthony Soulain (Sydney Institute for Astronomy, University of Sydney, Australia [SIfA]), Philippe Stee (OCA), Konrad Tristram (ESO-Chile), Jozsef Varga (Leiden), Julien Woillez (European Southern Observatory, Garching bei München, Germany [ESO]), Sebastian Wolf (Institute for Theoretical Physics and Astrophysics, University of Kiel, Germany), Gideon Yoffe (MPIA), and Gerard Zins (ESO-Chile).

MATISSE was designed, funded and built in close collaboration with ESO, by a consortium composed of institutes in France (J.-L. Lagrange Laboratory — INSU-CNRS — Côte d’Azur Observatory — University of Nice Sophia-Antipolis), Germany (MPIA, MPIfR and University of Kiel), the Netherlands (NOVA and University of Leiden), and Austria (University of Vienna). The Konkoly Observatory and Cologne University have also provided some support in the manufacture of the instrument.

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration in astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates APEX and ALMA on Chajnantor, two facilities that observe the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.

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Contacts:

Violeta Gámez Rosas
Leiden University
Leiden, the Netherlands
Tel: +31 71 527 5737
Email: gamez@strw.leidenuniv.nl

Walter Jaffe
Leiden University
Leiden, the Netherlands
Tel: +31 71 527 5737
Email: jaffe@strw.leidenuniv.nl

Bruno Lopez
MATISSE Principal Investigator
Observatoire de la Côte d’ Azur, Nice, France
Tel: +33 4 92 00 30 11
Email: Bruno.Lopez@oca.eu

Romain Petrov
MATISSE Project Scientist
Observatoire de la Côte d’ Azur, Nice, France
Tel: +33 4 92 00 30 11
Email: Romain.Petrov@oca.eu

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

Source: ESO/News

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Three’s a crowd

(130) Elektra
Credit: ESO/Berdeu et al., Yang et al.

Between Mars and Jupiter lie some of the relics of the early Solar System: the main asteroid belt. This belt is full of unusual asteroids whose origins reveal the building blocks of the early terrestrial planets. Of these, one of the more intriguing is Elektra, imaged here using the instrument SPHERE, installed on ESO’s Very Large Telescope at Paranal, Chile. 

Previously, Elektra was known to have not one but two moons orbiting it, shown by the orange and green orbits respectively. But now a team of astronomers, led by Anthony Berdeu, from the National Astronomical Research Institute of Thailand, have found a new satellite orbiting the asteroid — shown with the blue orbit. This discovery makes Elektra the first ever quadruple asteroid system.

This new, third moonlet of Elektra, provisionally named S/2014 (130) 2, lies closer to its parent asteroid than the other moons, at an average distance just under 350 km, and is 15000 times fainter than Elektra. The team used public data from the ESO science archive and a new processing technique to reveal this small moon. The discovery will help astronomers understand how these satellites form and, in turn, provides crucial information about planetary formation and evolution of our own solar system.

SPHERE, the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument, is a powerful planet-finding instrument. It uses an extreme adaptive optics system which allows for real time corrections of turbulence in the Earth’s atmosphere which causes stars to twinkle. It was only with SPHERE’s sensitivity and spatial resolution, coupled with cutting-edge data processing techniques, that the team was able to spot Elektra’s newest satellite.

Link

• Video showing the asteroid and its moons in motion
• Three's a crowd (non-annotated)

Source: ESO/potw

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A Galaxy Far, Far, Away: Cosmic Behemoths, and their Origins

Artist impression of the 14 galaxies detected by ALMA as they appear in the very early, very distant universe. These galaxies are in the process of merging and will eventually form the core of a massive galaxy cluster.

A century ago two prominent astronomers held a debate at the Smithsonian Museum of Natural History. The topic concerned the nature of the faint spiral nebulae seen in the night sky—are they galaxies that each contain billions of stars like our own Milky Way, or are they found within the Milky Way itself? The answer to this question would have profound implications for the size of our universe. We now know that these nebulae are indeed separate galaxies, but we still don’t fully understand how they form and evolve. It is a question the Next Generation Very Large Array (ngVLA) will help us understand. The ngVLA will study galaxy evolution by comparing how the fuel available for making stars matches up with the rate at which they are formed throughout the history of the cosmos.

Stars are born in stellar nurseries swaddled in enormous clouds of gas. The coldest, densest clouds of gas collapse under gravity, until enough material is pulled together in one spot to form a star, or multiple stars, in several parts of the cloud. But nature provides challenges to star formation. For example, powerful jets can shoot out during the process of star formation and push back on the collapsing gas clouds against gravity. Furthermore, baby stars themselves emit hot radiation that can act to evaporate the surrounding gas. Understanding the fine-tuned balance between these different competing phenomena in galaxies is a major goal of the ngVLA, primarily by looking at the cold gas itself rather than the end product of the whole process. This will be important for scientists to evaluate if their models of the star formation process correctly describe what happens in reality inside our cosmic neighbors, and in the universe beyond.

Tracing the cold gas content of galaxies throughout cosmic history is key to understanding how the stars and planetary systems we find in galaxies today were originally made, and thus, how galaxy evolution takes place. This evolution began only a few hundred million years after the Big Bang (i.e., more than 13 billion years ago) when galaxies first formed. In a single day of observations, the ngVLA will find tens to hundreds of galaxies in the early Universe based on the emission from the star-forming gas within them, while at the same time mapping the distribution and motion of the gas down to the size scales of individual star-forming clouds. Enabled by broad support in the US and from the worldwide astronomical community, these studies will transform our understanding of galaxy formation and evolution across cosmic history in the coming decade.

By Daniel Dale*

*Daniel Dale is the Harry C. Vaughan Professor of Astronomy at the University of Wyoming, where he studies star formation in nearby galaxies.

Source: National Radio Astronomy Observatory (NRAO)/Blogs

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