Discovered hungry quasar lying at 13 billion light-years away: it's a record!
An international group of astronomers used powerful telescopes to observe quasars, and
detected the most ancient quasar in the Universe! And we know what this means: the older an object
is, the further away it is from us. They measured a redshift of about 7.64,
that means it lies over 13 billions light-years away from us. It is older than Queen Elizabeth II!
The universe, at that time, was no more than 700.000 years old.
Astronomers are not so good in giving names to quasars, and it is called J0313-1806.
It is the most distant quasar to date. J0313-1806 it's about 1.6 billion times
more massive than our Sun, and about 1000 times brighter than our entire galaxy.
And it is very greedy: it is swallowing an equivalent of 25 solar masses per year.
But what are quasars? Why are they so important?
And how did we detect J0313-1806?
How can we reach those enormous distances? Follow me on this video to find out!
A new record for cosmic distances had been registered by a quasar.
His name is J0313-1806,
but from now on we will call it “Mr Q” because we don't like his name very much.
Quasars - a shortening of "quasi-stellar radio sources" - are the incredibly bright result of
an active galactic nucleus, with a supermassive black hole accreting material at such a rate that
the heat generated blazes across the Universe. It is commonly believed that this great luminosity
originates from the friction caused by gas and dust falling into a supermassive black hole;
they form an accretion disk, which converts about half the mass of an object into energy.
The term QUASAR was coined 56 years ago, in 1964, by the astrophysicist Hong-Yee Chiu.
It is believed that the first quasars were probably detected in the later 1950s,
as radio sources in all-sky radio surveys. 3C 48 and 3C 273 were first noted as radio
sources with no corresponding visible object. With small telescopes and the Lovell Telescope
as an interferometer, the quasars were shown to have a very small angular size.
By 1960, hundreds of these objects were recorded by 1960 and published in the Third
Cambridge Catalogue as astronomers scanned the skies for their optical counterparts.
Nowadays, hundreds of thousands of quasars are known.
They have a remarkably broad spectrum on all frequencies, from gamma rays to X-rays to
far-infrared and, for 10% of known quasars, up to radio frequencies. . Many quasars also show
an ultraviolet excess, emitting the same energy in this band as they emit in all the others.
Furthermore, the emission spectral lines are very wide, indicating that the mean
square velocity of matter in the emission region is very high, 3,000–10,000 km / s.
The other characteristic aspect is that their redshift is between z=0.056
and z=7.085, which implies rather large distances (in the order of billions of light-years).
Redshift is the displacement of the spectrum of an astronomical object toward longer (red)
wavelengths. It is generally attributed to the Doppler effect, a change in wavelength
that results when a given source of waves (e.g., light or radio waves) and an observer
are in rapid motion concerning each other. The American astronomer Edwin Powell
Hubble reported in 1929 that the distant galaxies were receding from the Milky
Way system, in which Earth is located, and that their redshifts increase proportionally with
their increasing distance. This generalization became the basis for what is called Hubble’s law,
which correlates the recessional velocity of a galaxy with its distance from Earth. That is
to say, the greater the redshift manifested by the light emanating from such an object,
the greater the distance of the object and the larger its recessional velocity . This law of
redshifts has been confirmed by subsequent research and provides the cornerstone of
modern relativistic cosmological theories that postulate that the universe is expanding.
In order to observe a quasar, one needs to make use of the most powerful telescopes on Earth,
and possibly combining them to get a higher resolution.
This technique is often used, and it's called interferometry.
It the basis for astronomical interferometer arrays, which can make measurements of
very small astronomical objects if the telescopes are spread out over a wide area.
If a large number of telescopes are used a picture can be produced which has a resolution similar
to a single telescope with the diameter of the combined spread of telescopes.
The team of researchers, led by the University of Arizona,
using the Atacama Large Millimeter/submillimeter Array (ALMA), the Magellan Baade telescope,
the Gemini North and W.M. Keck at Hawaii, found evidence of a hot quasar wind, blowing
from the supermassive black hole at the centre of Mr Q at 20 per cent of the speed of light.
The supermassive black hole at the core of this system is thought to be ingesting the
equivalent of 25 Suns every year, driving winds of hot plasma from the body.
The host galaxy housing Mr Q was also a region where vast numbers of stars were born.
While just one star is born each year, on average, in the Milky Way,
the host galaxy for this quasar sees around 200 stars light up for the first time each year.
Mr Q – the record object – is a precious representative of the progenitors of massive
galaxies, and it may give us new fundamental elements in order to investigate their birth
and, with it, the formation of supermassive black holes within them.
In fact, the black hole at the centre is two times more massive than the previous record holder,
and its earliness with respect to the age of the universe may
exclude two of the models we use to explain their formation.
Astronomers are puzzled learning how this structure formed in such a short period of time.
The most accredited models suggest that the first supermassive black holes
formed after the explosion of the first stars, or from direct collapse of enormous gas masses,
and also suggest that they could generate black holes with an initial mass
that goes from 100.000 to 1.000.000 solar masses.
These processes can create the first “seeds” in about one hundred or
maybe two hundred million years. Later, seeds grow until they reach
the observed masses of about one billion of solar masses, through gas accretion.
But the accreting gas scatters energy in the form of light radiation that could hinder
the accretion of the black hole itself. It would be this “self-regulating growth”,
to impose a limit in terms of accretion for the black hole.
For instance, a black hole can grow of about four orders of magnitude over 400 billion of years.
This means that Mr Q's mass had to be 100.000 solar masses and it had to have a redshift
of about 15: but this would be too much. As you can see, the importance of new quasars
lies in their contribution to our understanding of the Universe.
“This is the earliest evidence of how a supermassive black hole is
affecting its host galaxy around it. From observations of less distant galaxies,
we know that this has to happen, but we have never seen it happening so early in the universe,”
said Feige Wang from Steward Observatory, managed by the University of Arizona.
Anyway, at the moment, the collapse of cold hydrogen gas directly into a black hole is the
most likely explanation for how J0313–1806 could have grown to 1.6 billion solar masses in such a
short period of time, researchers concluded. We said that our Mr Q lies at a distance of
13 billion light years away, but...it is possible to detect further objects?
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Theoretically, it is possible to detect further objects.
Also, empirically, the fact that now we know three quasars with a redshift of about 7.5,
and that all of them host black holes of about 1 billion of solar masses,
suggests that quasars with smaller black holes were already present in the primordial universe.
The problem here is that these smaller objects are very rare and progressively fainter.
This requires the ideation of new observative programs aiming
to collect multi-band images in large areas of the sky.
And now, we want you to take a look at the summary of the draft version
of this discovery's scientific paper, because we think it's really worth it.
You don't have to worry too much if you can't understand some of the following statements:
we just want to give you a small taste of what scientific discovery is, and let you
take part in the fantastic world of science. Just take a moment to read and appreciate it.
“In this letter, we report the discovery of a luminous quasar, J0313–1806, at redshift
z = 7.642. It is the most distant quasar yet identified. J0313–1806 has a bolometric luminosity
of Lbol = (1.4 ± 0.1) × 1047 erg s−1 and hosts a SMBH with a mass of (1.6 ± 0.4) × 109 M, accreting
at an Eddington ratio of 0.67 ± 0.14. The existence of such a SMBH just ∼ 670 million years
after the Big Bang puts strong constraints on the formation models of seed black holes. The quasar’s
rest-frame UV spectrum exhibits broad absorption troughs from extremely high-velocity outflows.
These outflows have a maximum velocity up to ∼ 20% of the speed of light.
We also detect strong dust emission and [C II] line emission from the host galaxy in ALMA data.
The ALMA observations suggest that J0313–1806 is hosted by an intensely star-forming galaxy
with a star formation rate of ∼ 200 Myr−1 . The continuum observations
indicate that substantial dust (∼ 7 × 107 M) was already built up in the quasar host galaxy.
The relativistic quasar outflow and the fast SMBH growth phase,
combined with the intense star-forming activity in the host galaxy, suggest that J0313–1806
is an ideal target for investigating the assembly of the earliest SMBHs and their massive
host galaxies with future high resolution ALMA and JWST NIRSpec/IFU observations.”
We hope this video contributed to making you fall in love with science.
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