Tag Archives: #quasar

Astronomers Discovered The Most X-ray Luminous Quasar SRGE J170245.3+130104 at Redshift z ≈ 5.5 (Astronomy)

Khorunzhev and colleagues reported on the discovery of the most outstanding (so far) object found in the DaLeQoprogram — the brightest X-ray and Radio distant quasar SRGE J170245.3+130104 at redshift, z > 5, identified by spectral observations on the 6th BTA optical telescope. Their study recently appeared in journal Astronomy letters.

SRGE J170245.3+130104 was discovered by the eROSITA telescope aboard the SRG space observatory on March 13-15, 2020 during the first half-year scan of its all-sky X-ray survey. The optical counterpart of the X-ray source was photometrically identified as a distant quasar candidate at z ≈ 5.5. Follow-up spectroscopic observations, done in August/September 2020 with the SCORPIO-II instrument at the BTA 6-m telescope, confirmed that SRGE J170245.3+130104 is a distant quasar at redshift zspec = 5.466. The X-ray luminosity of the quasar during the first half-year scan of the eROSITA all-sky survey was 3.6 × 1046 erg/s (in the 2–10 keV energy range), whereas its X-ray spectrum could be described by a power law with a slope of Γ = 1.8. Six months later (September 13–14, 2020), during the second half-year scan of the eROSITA all-sky survey, the quasar was detected again and its X-ray luminosity had decreased by a factor of 2 (at the ≈ 1.9σ confidence level).

Fig 1: X-ray images of the SRG/eROSITA region 100 × 100 in the energy range 0.3–2.2 keV, centered on the optical source coordinates SRGE J170245.3+130104 (white cross). Left panel — image from the first half-year scan of SRG/eROSITA All-Sky Survey, right panel — image from the second half-year scan. Aperture with a radius of 10 is shown by red circle. Images are smoothed with a Gaussian filter (σ = 800). © Khorunzhev et al.

Now, Khorunzhev and colleagues reported that X-ray quasar SRGE J170245.3+130104 at z ≈ 5.47 discovered by the SRG X-ray observatory and the BTA 6-m telescope, is the most X-ray luminous quasar among known objects in the early Universe (z > 5) and also one of the most powerful quasars in radio.

They also mentioned that large radio-loudness (R ∼ 10³) of the quasar indicated that it can be a blazar and to test this hypothesis, it is necessary to carry out interferometric radio observations of the object at several wavelengths. Note that, only a few blazars at z > 5 are currently known, and all of them have lower X-ray luminosities than the quasar SRGE J170245.3+130104.

Fig. 2: Spectral energy distribution of the SRGE J170245.3+130104 quasar. The yellow dots show measurements in the radio spectral range, red dots — in the near-infrared and visible ranges, black dots — X-ray data SRG/eROSITA. The gray area — 1σ uncertainty of the power law model (with Galactic absorption) of the X-ray spectrum. Dot-dashed line shows the average blazar template. Solid line shows the radio-loud quasar template, corrected at wavelengths λ < 1216 Å for neutral hydrogen intergalactic absorption; the continuation of the original template at wavelengths λ < 1216 Å without considering absorption is shown by the dashed line. The blue line in the inset panel shows the smoothed optical spectrum obtained on the BTA telescope. © Khorunzhev et al.

In addition, they suggested that spectroscopic measurements in the near-infrared range (λ ∼ 1.6 microns) could also significantly complement the physical picture. It is expected that a broad MgII emission line should appear in the nearIR, which could be used to measure the mass of the black hole.

“The quasar SRGE J170245.3+130104 shows significant X-ray variability in the first two scans of the eROSITA all-sky survey. We will continue to monitor its variability in the following scans.”

— wrote authors of the study

Featured image: The 2’×2’ image in the iPS Pan-STARRS filter. The arrow indicates the position of optical companion SRGE J170245.3+130104. The radius of the small circle corresponds to the 1σ localization region. The radius of the large circle (10 arcsec) determines the size of the region where optical companion of X-ray source was searched.© Khorunzhev et al.

Reference: G.A. Khorunzhev, A.V. Meshcheryakov, P.S. Medvedev, V.D. Borisov, R.A. Burenin, R.A. Krivonos, R.I. Uklein, E.S. Shablovinskaya, V.L. Afanasyev, S.N. Dodonov, R.A. Sunyaev, S.Yu. Sazonov, M.R. Gilfanov, “Discovery of the most X-ray luminous quasar SRGE J170245.3+130104 at redshift z≈5.5”, Letters to Astronomical Journal, Volume: 47, Number: 3 Year: 2021 Pages: 155-173. DOI:  10.31857 / S0320010821030037

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Astronomers Discovered Most Distant Radio-loud Quasar (Astronomy)

Radio jets from active galactic nuclei (AGNs) are thought to play a key role in the coevolution of supermassive black holes and their host galaxies, as well as in the early growth of massive black holes. Yet, strong radio emission seems to be a rare or at least short-lived phenomenon. Only about 10% of all quasars are strong radio emitters, almost independent of their redshifts up to z ∼ 6. Now, Banados and colleagues presented the discovery of the most distant radioloud source to date, the quasar P172+18 with an Mg II-based redshift of z = 6.823 and is so distant that light from it has travelled for about 13 billion years to reach us: we see it as it was when the Universe was just around 780 million years old.. Their study recently appeared in ArXiv on dated 4 Mar 2021.

The quasar has a black hole mass of ∼ 2.9×108 M and an Eddington ratio of ∼2.2. It is known that there are large uncertainties on the estimates of black hole mass and Eddington ratio associated with the scaling relations used. Therefore, they compared the properties of P172+18 to other quasars using the same scaling relation and bolometric correction. With this in mind, P172+18 is among the fastest accreting quasars at both low and high redshift (Featured image).

The quasar shows a strong Lyα line that can be modeled with a narrow Gaussian and a broad one (shown in fig 1). The large measured near-zone size, RNZ,corr ∼ 6 pMpc, suggests an ionized intergalactic medium (IGM) around the quasar and implies that P172+18’s lifetime exceeds the average lifetime of the z ⪰ 6 quasar population.

Figure 1: Zoom-in on the main broad emission lines from near-infrared spectroscopy © Banados et al.

The quasar’s radio emission is unresolved (with size smaller than 1.”90 × 0.”87) and showed a steep radio spectrum (α = −1.31 ± 0.08) between 1.5 and 3.0 GHz (∼11–23 GHz in the rest frame). Extrapolating the spectrum to 5 GHz rest frame, the quasar has a radio-loudness of R2500 = 91 ± 9 (shown in fig. 2 below).

Figure 2. Radio spectral energy distribution of P172+18, including data from their VLA follow-up observations (red diamond), the VLBI measurements (green circles) from Momjian et al. (2021), and a 3σ upper limit from the TGSS (purple square). The power-law index, α, is shown between the measurements as well as the radio-loudness by extrapolating the radio emission to rest-frame 5GHz. The dotted line with α = 1.24 represents the turnover required for P172+18 to be classified as radio-quiet (i.e., R2500 < 10). © Banados et al.

The follow-up L-band radio data are a factor ∼ 2 fainter than what is expected from the FIRST observations taken two decades previously. This fact, together with the long lifetime implied by the size of P172+18’s near-zone, could indicate that they are witnessing the quasar phase turning off.

Figure 3. VLA L- and S-band observations (blue contours) centered on the position of P172+18 over optical and Near-infrared imaging as labeled in the figure; north is up and east is left © Banados et al.

In addition to detecting the quasar, the follow-up VLA radio observations revealed a second radio source 23.’’1 from P172+18 at a position angle of 128.25° (see Figure 3). This source was not detected in the FIRST survey and has no counterpart in their current optical/near-infrared images.

Featured image: Black hole mass vs. bolometric luminosity. The gray points and contours showed the distribution of SDSS DR7 quasars at 0.35 < z < 2.25. Red points and contours highlight the SDSS DR7 radio-loud quasar subsample. They showed z > 6 radio-quiet and radio-loud quasars from a collection of studies in the literature with blue circles and magenta squares, respectively. P172+18 (orange star) is consistent with accreting matter at super-Eddington rate. The dominant systematic uncertainty on black hole mass estimates from scaling relations (∼0.55 dex) is shown in the bottom right corner. All black hole masses shown here are estimated using the same scaling relation, and the same bolometric correction was applied for all bolometric luminosities © Banados et al.

Reference: Eduardo Banados, Chiara Mazzucchelli, Emmanuel Momjian, Anna-Christina Eilers, Feige Wang, Jan-Torge Schindler, Thomas Connor, Irham Taufik Andika, Aaron J. Barth, Chris Carilli, Frederick B. Davies, Roberto Decarli, Xiaohui Fan, Emanuele Paolo Farina, Joseph F. Hennawi, Antonio Pensabene, Daniel Stern, Bram P. Venemans, Lukas Wenzl, Jinyi Yang, “The discovery of a highly accreting, radio-loud quasar at z=6.82”, Astrophysical Journal, 2021. https://arxiv.org/abs/2103.03295

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The Earliest Supermassive Black Hole and Quasar in the Universe (Astronomy)

NOIRLab facilities provide key observations.

The most distant quasar known has been discovered. The quasar, observed just 670 million years after the Big Bang, is 1000 times more luminous than the Milky Way. It is powered by the earliest known supermassive black hole, which weighs in at more than 1.6 billion times the mass of the Sun. Seen more than 13 billion years ago, this fully formed distant quasar is also the earliest yet discovered, providing astronomers with insight into the formation of massive galaxies in the early Universe. The result was released today at the January 2021 meeting of the American Astronomical Society.

An artist’s impression of quasar J0313-1806 showing the supermassive black hole and the extremely high velocity wind. The quasar, seen just 670 million years after the Big Bang, is 1000 times more luminous than the Milky Way, and is powered by the earliest known supermassive black hole, which weighs in at more than 1.6 billion times the mass of the Sun. Credit: NOIRLab/NSF/AURA/J. da Silva

Quasars, which are powered by the feeding frenzies of colossal supermassive black holes, are the most energetic objects in the Universe. They occur when gas in the superheated accretion disk around a supermassive black hole is inexorably drawn inwards, shedding energy across the electromagnetic spectrum. The amount of electromagnetic radiation emitted by quasars is enormous, with the most massive examples easily outshining entire galaxies. Today, an international team of astronomers has announced the discovery of J0313-1806, the most distant quasar known to date.[1]

The most distant quasars are crucial for understanding how the earliest black holes formed and for understanding cosmic reionization — the last major phase transition of our Universe,” said Xiaohui Fan, study co-author and Regents Professor of Astronomy at the University of Arizona.[2]

J0313-1806 is seen more than 13 billion years ago. As the most distant quasar known, it is also the earliest, being fully formed only about 670 million years after the Big Bang. The new quasar is more than ten trillion times as luminous as our Sun — meaning that it pours out one thousand times more energy than the entire Milky Way Galaxy. The source of this quasar’s power is a supermassive black hole 1.6 billion times as massive as the Sun — the earliest black hole currently known to exist in the Universe.[3]

The presence of such a massive black hole so early in the Universe’s history challenges theories of black hole formation as astronomers need to explain how it came into existence when it barely had the time to do so. Feige Wang, NASA Hubble fellow at the University of Arizona and lead author of the research paper, explains: “Black holes created by the very first massive stars could not have grown this large in only a few hundred million years.

Video: This is CosmoView Episode 17 for press release noirlab2102: The Earliest Supermassive Black Hole and Quasar in the Universe Credit: Images and Videos: NOIRLab/NSF/AURA/J. da Silva, ESO/M.Kornmesser, CTIO/D. Munizaga, International Gemini Observatory/Kwon O Chul. Music: Stellardrone – Comet Halley

The observations that led to this discovery were made using a variety of telescopes, including three National Science Foundation NOIRLab facilities — the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American ObservatoryGemini South, and Gemini North. Data from the Blanco Telescope, taken as part of the DESI Legacy Imaging Surveys, which are served to the astronomical community via the Astro Data Lab at NOIRLab’s Community Science and Data Center (CSDC), helped to first identify J0313-1806, while Gemini South observations were used to confirm its identity as a quasar. High-quality spectra from two Maunakea observatories in Hawai‘i — Gemini North and W. M. Keck Observatory —  were used to measure the mass of the central supermassive black hole. 

The most distant quasars and earliest black holes are important markers in the history of the Universe,” said Program Director Martin Still of the National Science Foundation. “The researchers combined several of NSF’s NOIRLab facilities to make this discovery.” 

As well as weighing the monster black hole, the Gemini North and Keck Observatory observations uncovered an extremely fast outflow emanating from the quasar in the form of a high-velocity wind, which is traveling at 20% of the speed of light. “The energy released by such an extreme high-velocity outflow is large enough to impact the star formation in the entire quasar host galaxy,” said Jinyi Yang, Peter A. Strittmatter postdoctoral fellow of Steward Observatory at the University of Arizona. This is the earliest known example of a quasar sculpting the growth of its host galaxy, making J0313-1806 a promising target for future observations.

The galaxy hosting J0313-1806 is undergoing a spurt of star formation, producing new stars 200 times faster than the Milky Way. The combination of this intense star formation, the luminous quasar, and the high-velocity outflow make J0313-1806 and its host galaxy a promising natural laboratory for understanding the growth of supermassive black holes and their host galaxies in the early Universe.

This would be a great target to investigate the formation of the earliest supermassive black holes,” concluded Feige Wang. “We also hope to learn more about the effect of quasar outflows on their host galaxy — as well as to learn how the most massive galaxies formed in the early Universe.


[1] At a redshift of 7.64.

[2] There are two phase transitions of the Universe.

[3] Distance and time are closely entwined in astronomy, as the light from distant objects takes time to reach observers here on Earth. We see the Sun as it was 8 minutes ago, and our latest observations of the heart of the Milky Way show it as it was over 25,000 years ago. The further astronomers look from Earth, the further back in time they see.

Reference: Feige Wang, Jinyi Yang, Xiaohui Fan, Joseph F. Hennawi, Aaron J. Barth, Eduardo Banados, Fuyan Bian, Konstantina Boutsia, Thomas Connor, Frederick B. Davies, Roberto Decarli, Anna-Christina Eilers, Emanuele Paolo Farina, Richard Green, Linhua Jiang, Jiang-Tao Li, Chiara Mazzucchelli, Riccardo Nanni, Jan-Torge Schindler, Bram Venemans, Fabian Walter, Xue-Bing Wu, Minghao Yue, “A Luminous Quasar at Redshift 7.642”, ArXiv, 2021. https://arxiv.org/abs/2101.03179

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SDSS J125809.31+351943.0 (J1258): New Extremely Variable Quasar (Astronomy)

By analyzing data from astronomical surveys, Japanese astronomers have reported a new, extremely variable quasi-stellar object (QSO), SDSS J125809.31+351943.0 (J1258), which brightened in optical for 4 mag from 1983 to 2015, which is one of the largest quasar brightening events so far.

Time-series of the photometric data of J1258 in optical and mid-infrared. Credit: Nagoshi et al., 2020.

Quasars are active galactic nuclei of very high luminosity, emitting electromagnetic radiation observable in radio, infrared, visible, ultraviolet and X-ray wavelengths. They are among the brightest and most distant objects in the known universe, and serve as fundamental tools for numerous studies in astrophysics as well as cosmology. For instance, quasars have been used to investigate the large-scale structure of the universe and the era of reionization. They also improved our understanding of the dynamics of supermassive black holes and the intergalactic medium.

Some distant quasars exhibit broad emission lines (BELs) that appear or disappear, which is known as a so-called optical “changing-look” phenomenon. Most of these changing-look quasars (CLQ) showcase large optical luminosity variations exceeding 1.0 mag. Besides CLQs, such large luminosity changes have been also observed in hyper-variable quasars (HVQs) and changing-state quasars (CSQs). The classification of HVQs is based on the change of optical brightness, while that of the CSQ is on the change of BELs, optical continuum flux density and mid-infrared luminosities.

Now, a team of astronomers led by Shumpei Nagoshi of the Kyoto University in Japan reports the finding of a new quasar that exhibits a large amplitude of variability and appears to be a CSQ. The discovery of SDSS J125809.31+351943.0 (or J1258 for short) was based on data from programs including the Survey and All Sky Automated Survey for Super Novae (ASAS-SN), the Sloan Digital Sky Survey (SDSS) and NASA’s Wide-field Infrared Survey Explorer (WISE).

The observational data span the period between 1983 and 2015. It was found that J1258 exhibited a monotonic increase of luminosity for as much as 4 mag over about 30 years. The astronomers noted that this is one of the largest amplitudes of monotonic variations with the longest timescale of any quasar’s variability reported to date.

Furthermore, the observations revealed significant changes in the mid-infrared luminosity and in the intensity of the broad emission line of J1258. The results also show the weakness of radio emission, which indicates that the variability is not caused by the quasar’s jet. In addition, it was found the flux in mid-infrared changed following the optical band. This supports the assumption that the accretion disk itself changed, rather than the variation of absorption, took place.

The astronomers therefore concluded that J1258 is a CSQ and also one of the most drastically variable objects so far detected.

References: Nagoshi et al., Discovery of a new extreme changing-state quasar with 4 mag variation, SDSS J125809.31+351943.0, arXiv:2011.01127 [astro-ph.GA] arxiv.org/abs/2011.01127

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Hanny’s Voorwerp Is A Puzzling Space Object Discovered By A Dutch School teacher (Astronomy)

Many people dream of making the next big discovery to change the way humans think about the universe. For most of history, that dream has been off limits to all but research scientists. In recent decades, however, citizen science has given regular people a chance to make those big discoveries. That’s how one of the strangest space objects ever witnessed was discovered by a 24-year-old schoolteacher from the Netherlands.

Hanny’s Voorwerp Is The Green Cloud Near The Bottom, With Its Sister Galaxy IC 2497 Right above. ©WIYN/William keel/Anna Manning

But, why we are covering this? Because the fact that a regular citizen can make a huge scientific discovery is a testament to the power of citizen science. It makes us wonder…. could we make the next big space discovery?

Discoverer Hanny van Arkel told the story of the bizarre object’s discovery on her website. As a citizen volunteer for Galaxy Zoo—a citizen-science organization she discovered through her fandom of Queen-guitarist-turned-phD Brian May—van Arkel spent her free summer months in 2007 classifying galaxies from Hubble images. She had only been volunteering a week when she classified an anti-clockwise spiral galaxy…and stopped. There was more to the image than just the galaxy. “I noticed it had a nice neighbour, although I wasn’t sure it was a galaxy, so maybe ‘the smudge under it’ is a better way of explaining what I saw,” van Arkel writes. “I read on the site about irregular galaxies and this ‘smudge’ made me think of one of those, although it was much bluer and it had a remarkable form.”

She submitted the image to the Galaxy Zoo forums to see if anyone knew what the “smudge” was. No one did, but that didn’t stop them from puzzling over it. One member, who knew van Arkel was Dutch, looked up the Dutch word for “object” and posted “Hanny, here’s your Voorwerp.” “Hanny’s Voorwerp” was given a name.

Hanny Van Arkel, Discoverer Of Hanny’s Voorwerp


In January 2008, the astronomers in charge of Galaxy Zoo began investigating Hanny’s Voorwerp. What they discovered was the interaction between a region of star formation and cloud of gas flowing out from the spiral galaxy van Arkel originally classified. At the core of that galaxy is a quasar, whose black-hole-powered radiation blast sent a powerful beam of light at Hanny’s Voorwerp and turned its gas cloud an eerie green color. According to NASA, “Radio studies have revealed that Hanny’s Voorwerp is not just an island gas cloud floating in space. The glowing blob is part of a long, twisting rope of gas, or tidal tail, about 300,000 light-years long that wraps around the galaxy. The only optically visible part of the rope is Hanny’s Voorwerp. The illuminated object is so huge that it stretches from 44,000 light-years to 136,000 light-years from the galaxy’s core.” That all may mean that this galaxy collided with another galaxy around a billion years ago, thereby teaching astronomers something new about how galaxies merge.

Hanny van Arkel discovered something new about the universe. While this may have been nearly impossible for a 20-something schoolteacher in decades past, the internet has proven to be an egalitarian place where anyone can achieve amazing things, as long as they keep on trying.

Astronomers Find The First Galaxy Whose UV Luminosity Is Comparable To That Of A Quasar (Astronomy)

Astronomers using Gran Telescopio Canarias (GTC) and with the ATACAMA Large Millimeter/submillimetre Array (ALMA) have found the first galaxy whose ultraviolet luminosity is comparable to that of a quasar.


The galaxy, called BOSS-EUVLG1, has a red-shift of 2.47. This is a measure of the reddening of the light coming from the galaxy, and can be used to find its distance: the further away the galaxy, the greater the value. For BOSS-EUVLG1, the value of 2.47 means that the galaxy has been observed when the universe was some 2000 million years old, around 20% of its present age.

The large values of redshift and luminosity of BOSS-EUVLG1 caused it to be classified previously in the BOSS (Baryon Oscillation Spectroscopic Survey) project as a quasar. However, from the observations made with the OSIRIS and EMIR instruments on the GTC, and with the millimeter-wave telescope ALMA, the researchers have shown that it is not a quasar, but in fact a galaxy with extreme, exceptional properties.

The study revealed that the high luminosity of BOSS-EUVLG1 in the ultraviolet and in Lyman-alpha emission is due to the large number of young, massive stars in the galaxy. This high luminosity, well above the range for other galaxies, gave rise to its initial identification as a quasar. However, in quasars, the high luminosity is due to the activity around the supermassive black holes in their nuclei and not to star formation.

“BOSS-EUVLG1 seems to be dominated by a burst of formation of young, very massive stars, with hardly any dust, and with a very low metallicity,” explains Rui Marques Chaves, a researcher at the CAB, formerly a doctoral student at the Instituto de Astrofísica de Canarias and the University of La Laguna (ULL), and first author of the article.

Left and centre: Image of the region of the sky containing BOSS-EUVLG1, which stands out due to its blue colour. Credit: DESI Legacy Imaging Surveys. Right: Artist’s drawing of the burst of star formation in BOSS-EUVLG1, which contains a large number of young massive stars, and hardly any dust. Credit: Gabriel Pérez Díaz, SMM (IAC).

The rate of star formation in this galaxy is very high, around 1000 solar masses per year, which is about 1000 times higher than that in the Milky Way, although the galaxy is 30 times smaller. This rate of star formation is comparable only to the most luminous infrared galaxies known, but the absence of dust in BOSS-EUVLG1 allows its ultraviolet and visible emission to reach us with hardly any attenuation.

The results of the study suggest that BOSS-EUVLG1 is an example of the initial phases of the formation of massive galaxies. In spite of its high luminosity and star formation rate, its low metallicity shows that the galaxy has hardly had time to enrich its interstellar medium with dust and newly formed metals. Nevertheless, says IAC doctoral student and co-author Camilo E. Jiménez Ángel, “the galaxy will evolve toward a dustier phase, similar to the infrared galaxies. Also, its high luminosity in the UV will last only a few hundred million years, a very short period in the evolution of a galaxy.”

“This would explain why other galaxies similar to BOSS-EUVLG1 have not been discovered,” says Claudio Dalla Vecchia, a researcher at the IAC, and a co-author of the article.

BOSS-EUVLG1 was discovered via the analysis of a half-million spectra of galaxies and quasars in the BOSS project of the Sloan Digital Sky Survey (SDSS) and observations with large telescopes such as the GTC and ALMA.

References: R. Marques-Chaves, J. Alvarez-Marquez, L. Colina, I. Perez-Fournon, D. Schaerer, C. Dalla Vecchia, T. Hashimoto, C. Jimenez-Angel, Y. Shu, ‘The discovery of the most UV-Lya luminous star-forming galaxy: a young, dust- and metal-poor starburst with QSO-like luminosities’, ArXiv, 2020. arXiv:2009.02177 link: https://arxiv.org/abs/2009.02177v1

Astronomers Find Three Luminous Dual Quasars (Astronomy)

Using the Subaru Telescope and W. M. Keck and Gemini observatories, astronomers have spotted three dual quasars — merging galaxy systems that have two supermassive black holes on a collision course with each other.

SDSS J141637.44+003352.2, a dual quasar at a distance for which the light reaching us was emitted 4.6 billion years ago. The two quasars are 13,000 light-years apart on the sky, placing them near the center of a single massive galaxy that appears to be part of a group, as shown by the neighboring galaxies in the left panel. In the lower panels, optical spectroscopy has revealed broad emission lines associated with each of the two quasars, indicating that the gas is moving at thousands of kilometers per second in the vicinity of two distinct supermassive black holes. The two quasars are different colors, due to different amounts of dust in front of them. Image credit: Silverman et al, doi: 10.3847/1538-4357/aba4a3.

Quasars are one of the most luminous, energetic objects known in the Universe, powered by supermassive black holes that are millions to billions times more massive than our Sun.

As material swirls around a black hole at the center of a galaxy, it is heated to high temperatures, releasing so much light that the quasar can outshine its host galaxy.

This makes a merging pair of galaxies with quasar activity hard to detect; it is difficult to separate the light from the two quasars because they are in such close proximity to each other.

Also, observing a wide enough area of the sky to catch these rare events in sufficient numbers is a challenge.

To overcome these obstacles, Dr. John Silverman, an astronomer at the Kavli Institute for the Physics and Mathematics of the Universe, and colleagues took advantage of a sensitive wide survey of the sky using the Hyper Suprime-Cam (HSC) camera on the Subaru Telescope.

The astronomers identified 421 candidates at distances less than 12.4 billion light-years.

However, there was still the chance many of these were not bona-fide dual quasars but rather chance projections such as starlight from our own Milky Way Galaxy.

Confirmation required detailed analysis of the light from the candidates to search for definitive signs of two distinct quasars.

Using Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS) and Gemini Observatory’s Near-Infrared Integral Field Spectrometer, the team identified three dual quasars, two of which were previously unknown.

Each object in the pair showed the signature of gas moving at thousands of km per second under the influence of a supermassive black hole.

In spite of their rarity, dual quasars represent an important stage in the evolution of galaxies, where the central giant is awakened, gaining mass, and potentially impacting the growth of its host galaxy.

References: John D. Silverman et al. 2020. Dual Supermassive Black Holes at Close Separation Revealed by the Hyper Suprime-Cam Subaru Strategic Program. ApJ 899, no. 2, 2020; doi: 10.3847/1538-4357/aba4a3 link: https://iopscience.iop.org/article/10.3847/1538-4357/aba4a3

Introducing The Universe’s Most Epic Object: Blazar (Astronomy)

What’s the most powerful thing in the universe? A star? A supernova? A black hole? None of those compare to the epic awesomeness that is a blazar.

A blazar is the turducken of awesome space objects: it’s a supermassive black hole inside a radioactive accretion disk inside an active galaxy. Oh, and it shoots jets of radiation from either end at close to the speed of light, right in our direction. Let us explain.


Most large galaxies contain supermassive black holes at their centers (even our own Milky Way). Black holes suck the gas, dust, and other debris around them so fast that not everything can keep up. This forms a sort of traffic jam around the black hole known as an accretion disk. The gravitational pressure exerted by the black hole on this disk is enough to heat it up to millions of degrees, making it emit a massive amount of radiation. The black hole, meanwhile, is spinning rapidly, which forms a magnetic field strong enough to turn the radioactive material into powerful jets that blast out of each end at close to the speed of light for hundreds of thousands of light years.

Technically, we just described three objects. How’s that? A black hole that shoots a radioactive jet perpendicular to our vantage point is called a radio galaxy. If that jet is at an angle, it’s called a quasar. If the jet is pointed right at us—making it bright enough to be detectable by Earth-based instruments as far as 9 billion light-years away—it’s a blazar.

Spinning Black Hole Powers Jet By Magnetic Flux (Astronomy)

Spinning black holes in the centres of galaxies can release powerful magnetised jets. When the jets are observed at angles of less than a few degrees to the line-of-sight, they are called blazars, showing variable non-thermal emission across the electromagnetic spectrum from radio waves to gamma rays. It is commonly believed that shock waves are responsible for this dissipation of jet energy.

Fig: The centre of quasar 3C279 emits flickering gamma radiation, which is characteristic of the phenomenon of magnetic reconnection. Credit: Amit Shukla

In the recent study researchers showed, gamma-ray observations of the blazar 3C 279 with the space-borne telescope Fermi-LAT. They discovered that the core of the jet, which was found in the millimeter wavelength range, also emits high-energy gamma radiation, but with an extremely flickering brightness.

The special pattern of the sequence of brightness changes is characteristic of a universal process called magnetic reconnection, which occurs in many astrophysical objects with strong magnetic fields. Solar activity also has to do with the dynamics of magnetic fields and reconnection. This was recently demonstrated by observing ‘campfires’ in the solar atmosphere with the Solar Orbiter mission of the European Space Agency ESA.

During reconnection, energy that is initially stored invisibly in the magnetic field is suddenly released in numerous “mini-jets.” In these jets, particles are accelerated, which then produce the observed gamma radiation. Magnetic reconnection would explain how the energy reaches the jet’s core from the black hole and where it ultimately comes from.

According to professor Karl Mannheim, spacetime near the black hole in the quasar 3C279 is forced to swirl around in corotation. Magnetic fields anchored to the plasma around the black hole expel the jet slowing down the black hole’s rotation and converting part of its rotational energy into radiation.

References: A. Shukla et al. Gamma-ray flares from relativistic magnetic reconnection in the jet of the quasar 3C 279, Nature Communications (2020). DOI: 10.1038/s41467-020-17912-z link: https://www.nature.com/articles/s41467-020-17912-z