Hello Space Fans and welcome to another edition
of Space Han News.
Earlier this month, astronomers from the University
of Central Lancashire in the UK have released
a study showing that black holes are growing
faster than expected.
As many of you already know, lurking at the
centers of most galaxies are black holes that
can weigh anywhere from one million to one
billion times as much as the Sun.
Well new research shows that these black holes
are growing at much larger rates than had
been thought possible.
Even the black hole in our own Milky Way Galaxy,
which otherwise appears very quiet, has probably
been consuming the equivalent of one Sun every
3000 years.
Until recently astronomers had thought that
black holes grow mostly when galaxies crash
into each other.
Mostly.
During these collisions and mergers a large
concentration of gas forms around the black
hole and gets very hot, shining very brightly
and we get something called an active galactic
nucleus.
This gas gets so bright that active galactic
nuclei can be seen all the way back to shortly
after the Universe first formed.
This theory held that black holes in the centers
of ordinary spiral galaxies like our own Milky
Way cannot grow much because they haven't
collided as much as, say elliptical galaxies
have.
Elliptical galaxies are much older than spirals
and they got elliptical by banging around
with other galaxies.
However, the team at the University of Central
Lancashire used computer simulations to show
that black holes even in spiral galaxies must
grow by large amounts and they do it without
the need for collisions.
To back this up, recent observations by the
Hubble Space Telescope have indicated that
black holes can grow even in quiet spiral
galaxies.
Some spiral galaxies have active galactic
nuclei and they may outnumber those in merging
galaxies.
The team of researchers used a property of
black holes that was first discovered by the
Hubble Space Telescope, that their masses
can be quite accurately predicted from the
speed of stars in the galaxies they live in.
Faster stars whipping around mean larger black
holes than those with slower stars.
The team claims to have successfully disproven
the previous theory that black holes are unable
to grow unless it's colliding and merging
by using computer simulations to compare the
masses of black holes in spiral galaxies with
those of elliptical galaxies.
Elliptical galaxies are what you get after
spirals have been merging for a long time.
They are much older and much larger.
Take a look at my video on IC 1101 to see
just how big.
This comparison found no mismatch between
the two.
The black holes in the two types of galaxies
are consistent with a constant feeding, not
a haphazard set of collisions, and for this
to have happened, black holes had to have
been growing even when it wasn't colliding.
The black hole that has grown the most can
be found in the Sombrero galaxy.
The researchers estimate that this black hole
has been swallowing the equivalent of one
Sun every 20 years and is now over 500 million
times as heavy as the Sun.
This new research provides the theoretical
basis for understanding the emerging picture
that galaxy collisions and mergers are a relatively
small contribution to the growth of black
holes, contrary to what everyone thought before.
Just like downtown.
Next, astronomers using NASA's Chandra X-Ray
Observatory have found what may be the youngest
black hole in our galaxy.
New data from Chandra suggest a highly distorted
supernova remnant may contain the most recent
black hole formed in the Milky Way galaxy.
The remnant appears to be the product of a
rare explosion in which matter is ejected
at high speeds along the poles of a rotating
star.
The remnant, called W49B, is only about a
thousand years old as seen from Earth and
is located only 26,000 light-years away.
According to the new study done by astronomers
at MIT, W49B is the first of its kind to be
discovered in our galaxy.
It appears its parent star ended its life
in a way that most others don't.
Usually when a massive star runs out of fuel,
the central region of the star collapses,
triggering a chain of events that quickly
culminate in a supernova explosion.
Most of these explosions are generally symmetrical,
meaning when the star exploded the stellar
material flew out more or less evenly in all
directions.
But, in the W49B supernova, this didn't happen.
Material near the poles of the rotating star
was ejected at a much higher speed than material
coming from its equator.
This effect, along with huge jets shooting
away from the star's poles is what mainly
shaped the supernova explosion and its aftermath.
The remnant now glows brightly in X-rays and
other wavelengths, offering the evidence for
a peculiar explosion.
By tracing the distribution and amounts of
different elements in the stellar debris field,
researchers were able to compare the Chandra
data to theoretical models of how a star explodes.
For example they found iron in only half of
the remnant while other elements such as sulfur
and silicon were spread throughout.
This matches predictions for what you'd expect
to see in an asymmetric explosion.
So what was left behind after the explosion?
Most of the time, massive stars that collapse
into supernovas leave a dense, spinning core
called a neutron star.
Astronomers can often detect neutron stars
through their X-ray or radio pulses.
But a careful search of the Chandra data found
no evidence for a neutron star.
The lack of any remnant implies, well, that
a black hole may have formed.
Now they admit that this is a bit circumstantial,
but because this remnant is so close to us,
they have a great opportunity in future studies
to get a really good look to see what's in
there to make sure.
Even more sobering given how close this thing
is to us, is that if it did form a black hole,
then there may also have been an associated
Gamma Ray Burst.
Supernova explosions driven by jets like the
one in W49B have been linked to gamma-ray
bursts (GRBs) in other objects.
GRBs, which have been seen only in distant
galaxies, are thought to mark the birth of
a black hole.
There is no evidence the W49B supernova produced
a GRB, but it may have properties – including
being jet-driven and possibly forming a black
hole – that are in common with those of
a GRB.
Having stars explode so close to us and possibly
producing a GRB only 26,000 light years away,
can make for a very bad day here on Earth
if one of those jets is pointed at us.
Now you know why I'm always telling you to
keep looking up!
Finally, astronomers used the Green Bank radio
telescope in West Virginia to calculate that
fewer than one in a million stars in the Milky
Way Galaxy have planetary civilizations advanced
enough to transmit beacons we could detect.
Astronomers at the University of California
Berkeley studied 86 of Kepler's 2,740 identified
exoplanets and while they didn’t find ET,
they were able to use this statistical sample
to, for the first time, put explicit limits
on the presence of intelligent civilizations
transmitting in the radio band where they
searched.
Still, don't get too bummed out.
Even with one in a million odds, there could
still be millions of advanced civilizations
in the galaxy.
Because of Kepler and other research, it has
recently been determined that there are around
a trillion planets in the Milky Way Galaxy,
that's more planets than there are stars.
There is still reason to think that in the
future, we may contact another civilization
at some point down the line.
At least, that's what I keep telling myself.
The 86 stars in this study were chosen last
year based on a list of 1,235 planet candidates
known at that time.
The scientists chose stars with five or six
planets in orbit and that could be in the
habitable zone.
The Green Bank telescope, spent 12 hours collecting
five minutes of radio emissions from each
star in a frequency range that on Earth falls
between the cellphone and TV bands.
They then combed through the data looking
for high-intensity signals with a narrow bandwidth
(5 Hz) that are only produced artificially
– presumably by intelligent life.
Most of the stars were more than 1,000 light
years away, so only signals intentionally
aimed in our direction would have been detected.
The scientists say that in the future, more
sensitive radio telescopes, such as the Square
Kilometer Array, should be able to detect
much weaker radiation, perhaps even unintentional
leakage radiation, from civilizations like
our own.
According to the Berkeley researchers, "This
work illustrates the power of leveraging our
latest understanding of exoplanets in SETI
searches.
We no longer have to guess about whether we
are targeting Earth-like environments, we
know it with certainty.”
Well, that's it for this week Space Fans,
thank you for watching and as always, Keep
Looking Up!
