- 3983 - QUASAR - largest found. Quasars, the most extreme phenomena in the universe, are triggered when galactic collisions deliver gas to feeding black holes.
------------------------------ 3983 - QUASAR - largest found.
- Scientists
may have solved a 60-year-old mystery by discovering that “quasars”, energetic
objects that are powered by supermassive black holes and outshine trillions of
stars combined, form when galaxies collide and merge.
-
- The Milky
Way could host a quasar of its own when it collides with the neighboring
Andromeda galaxy several billion years from now.
-
- Scientists
have previously tracked quasars' bright, energetic emissions to regions at the
hearts of galaxies that span roughly the width of the solar system, meaning
quasars must come from incredibly compact objects.
-
- The leading
theory suggests that quasars are supermassive black holes heating huge amounts
of surrounding gas, thus releasing tremendous amounts of radiation before the
material falls onto the black hole's surface.
-
- Since their
discovery sixty years ago, quasars have puzzled scientists, mainly because it's
unclear just how supermassive black holes can draw in enough raw material to
fuel such powerful emissions. While supermassive black holes dwell at the
centers of most galaxies, the gas needed to fuel quasars tends to orbit on the
outskirts of galaxies. Thus, there must be some delivery service moving gas
toward the hearts of galaxies.
-
- Deep imaging
observations from the “Isaac Newton Telescope” in Spain's Canary Islands to
finally solve this puzzle. To understand
how quasars are ignited we need to determine how gas can fall into the center
of the host galaxies at sufficiently high rates.
-
- One idea is
that the necessary radial infall is caused by collisions between galaxies,
whose associated gravitational forces can perturb the gas from its usual
circular orbits.
-
- When
comparing 48 nearby galaxies hosting
quasars to 100 non-quasar galaxies, the researchers discovered the presence of
distorted structures at the edges of the quasar-hosting galaxies. These
structures also indicate a past or ongoing collision and merger with another
galaxy.
-
- Astronomers
found a high rate of such structures in quasar-hosting galaxies, three times
that measured for a carefully matched control sample of non-quasar galaxies
that were imaged with the same techniques.
This provides strong evidence that quasars are triggered in galaxy
collisions.
-
- Quasars can
have a large influence on the evolution of galaxies that host them; better
understanding how quasars ignite could help scientists hone their models of
galaxy evolution and the evolution of the universe as a whole.
-
- It's
important to understand how, when, and where quasars are triggered, as once
triggered, the enormous radiative power generated by a quasar can have a major,
damaging effect on the surrounding host galaxy.
-
- The
pressure of the radiation can expel the remaining gas in the remnant galaxy system.
Since gas is required to form new stars, this will cut off any future star
formation activity, effectively the death throes of the galaxy.
-
- The
nearest large galaxy, the “Andromeda Spiral”, is coming directly towards us
at a high velocity, and will collide and merge with the Milky Way in around 5
billion years. When this happens, it's
likely that a quasar will be triggered as gas falls into the center of the
remnant system.
-
- Black
holes like these, known as quasars, are the biggest types of black holes we
know about. Black holes are some of the
most massive single objects in space, but what's the biggest one in existence,
and how big can they get?
-
- There is a
theoretical limit to the size of black holes, celestial objects so massive that even light cannot
escape them. And the largest directly observed black hole with a confirmed mass
is right around this limit.
-
- This
monster, named “TON 618”, weighs roughly 40 billion solar masses. TON 618 has a
radius of over 1,000 astronomical units (AU), which means that if the black
hole was placed in the center of the solar system, by the time you reached
Pluto, you would be less than 5% of the
way from the center of the black hole to its edge.
-
- TON 618 sits
about 18.2 billion light-years away from Earth. In the night sky, it sits on the border between the constellations
Canes Venatici and Coma Berenices. Astronomers first spotted it in a 1957. They first thought it was a faint blue star,
but observations a decade later revealed that the astronomers had glimpsed
intense radiation from the material falling into the giant black hole.
-
- TON 618
powers a quasar, one of the brightest objects in the entire universe with the
illuminating power of 140 trillion suns. Quasars draw light from the
gravitational energy of the central black hole. Material around the black hole
falls in, and as it does so it compresses and heats up, releasing enormous
amounts of radiation.
-
- While
individual events like the most powerful supernovas can briefly outshine
quasars, they only last a few weeks. In contrast, quasars can shine for
millions of years. However, quasars are
so far away that they only appear as faint spots of visible light in even the
most powerful telescopes, and astronomers first detected them by their powerful
radio emissions.
-
-
Supermassive black holes become enormous through a combination of
merging with other black holes and by constantly feeding on surrounding
material.
-
- The feeding rate is what sets the limit on the
size of a black hole. These cosmic vacuum cleaners can only consume so much
material in a given amount of time. As material falls in, it heats up and
releases radiation (creating a quasar), but that radiation heats the material
itself, preventing it from quickly falling into the black hole.
-
- This
self-regulation prevents black holes from growing too quickly. Astronomers can
estimate a maximum mass for a black hole by taking that feeding rate and
multiplying it by the known age of the universe, giving an estimated maximum
mass of around 50 billion solar masses.
-
- That is only
an estimate. There may be other, more exotic, ways to create large black holes,
such as from the direct collapse of large clumps of dark matter in the early
universe. So, it's still possible that
there are even more massive black holes out there.
-
April 30, 2023 QUASAR -
largest found.
3983
----------------------------------------------------------------------------------------
----- Comments
appreciated and Pass it on to whomever is interested. ---
--- Some
reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email
feedback, corrections, request for copies or Index of all reviews
--- to: ------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Tuesday, May 2, 2023
---------------------------
-
No comments:
Post a Comment