These 5 astronomical objects Have a Weird Behavior That They Shouldn't have!
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Galaxies lacking dark matter. Disappearing pulsars.
White dwarfs switching on and off. What do they have in common?
Do you think you know the solution?
They are all astronomical objects that are not behaving as they should.
Today we will take a closer look at them: follow me in
this video about unusual objects in our universe.
5) NGC 1052-DF2
What is the nature of dark matter? This is a problem which physics is trying to solve,
but it is not as easy as it seems. Dark matter, if it exists,
behaves differently from “ordinary” matter. In particular, we can't observe dark matter
directly, while we can of course take a look at the ordinary matter in our
universe since it is clearly visible. So what we try to do is, first of all,
trying to take a look at how dark matter interacts with ordinary matter,
studying the effects on the surroundings. Well-known evidence of the presence of
dark matter in the shape of the velocity curve of some galaxies:
the velocity along our line of sight should decrease to zero for a distribution of matter
that we expect in a galaxy, and that would be a so-called Keplerian trend.
But things are not going this way, because we observe that, at a certain point,
the velocity stops decreasing and it almost remain constant in the outer parts of the galaxy.
This can only be explained by assuming that dark matter exists, and, in this case,
it has the effect of increasing the velocity of normal matter, so a gravitational effect.
Also, since this effect is really small in the inìner part of the galaxy,
we think that dark matter is present in huge quantities in the outer edge of galaxies.
Although we don't know yet what's the constitutive element of dark matter,
we know that somehow it should exist, otherwise we couldn't explain such phenomena.
However, we should be careful when talking about dark matter,
because it could also be that what appears to be dark matter
is really just a currently unknown effect of the gravity of the ordinary matter.
From time to time we find galaxies that lack dark matter, as is the case of NGC 1052.
The apparent lack of dark matter in NGC 1052-DF2 may help prove that dark matter is real:
If what appears to be dark matter is really just an unknown effect of the
gravity of ordinary matter then this apparent dark matter should also appear in this galaxy.
Further study will be needed before this and any other possible implications can be confirmed.
If confirmed, the absence of dark matter may also have implications for theories
of galaxy formation, as the dark matter has been thought to be needed for galaxy formation.
However for the moment, everything is fine and our models seem to work,
Indeed, another group of astronomers have found the existence of tidal tails in NGC 1052-DF4,
a galaxy near to NGC 1052- DF2. This indicated that the lack of
dark matter has probably been caused by the interaction with a nearby neighbour.
The interaction naturally explains the low content of dark matter inferred for this galaxy
and reconciles these types of galaxies with our current models of galaxy formation.
==================================================================== 4) Pulsar PSR J1841-0500
Pulsars are pretty cool objects. They're basically highly
magnetized rotating compact star, which emits beams of electromagnetic radiation
in the direction of their magnetic poles. A fun fact about them is that they
are so dense objects, that a teaspoon of them would weigh about 15 tons.
A more interesting property of pulsars is the extremely regular rotation period.
This means that the beam coming from the pulsar reaches the earth at extremely
regular intervals of time, so precise that you could probably use them as perfect clocks.
In 1983, certain types of pulsars were detected that, at that time, exceeded the
accuracy of atomic clocks in keeping time. Observations of a pulsar in a binary neutron
star system were used to indirectly confirm the existence of gravitational radiation. And also,
the first extrasolar planets were discovered around a pulsar, PSR B1257+12 in 1992.
However, for reasons not yet understood, pulsars can stop...pulsating for a time.
This is known as nulling. Nulling is thought to be caused
by one of two things: intrinsic effects within the pulsar or geometric effects
due to spin and rotation. On the geometric side, it is theorized that nulling is a result of the
pulsar emitting regularly but simply turning away from us so we do not see the emission.
In order to better understand what kind of pulsars are null and why researchers examine the largest
sample of nulling pulsars ever studied and look at the correlation (or lack thereof) between
nulling fraction and various pulsar parameters such as age and find some interesting results.
One famous example is the pulsar PSR J1841-0500. It is a very distant pulsar at over 22 thousand
light-years away. This pulsar was discovered in 2008 and it had a period of 9 seconds,
but in 2009, it stopped completely and went silent for 580 days, before it abruptly started pulsating
again, in 2011. We are glad it's back, but so far no other pulsar like this has been found.
What happened during those 580 days is a mystery that may never be solved.
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3) ULAS J1342+0928 and the oldest black hole in the universe.
We found a Blackhole that shouldn't exist or, better to say, it shouldn't be that massive.
It belongs to the quasar ULAS J1342+0928, which is the second most distant quasar
known. Why?
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To understand this, we have to do a step back. Something like a 14 billion years step back.
Its mass is 800 million solar masses, and it was born 690 million years after the big bang.
At that time, the universe was pretty different from what we are used to,
and astrophysicists refer to that period as the re-ionization period.
Quasars may be the key to understanding something more about this epoch of the universe.
We think that, at that time, there was not enough material
to give birth to such a massive black hole. Being such an early object, this black hole
intuitively shouldn't be as massive as it is. Abut we observe it and we know it exists.
So, are our current models of black hole formation wrong, or is our data incomplete?
Are we missing something? I guess only time will tell.
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2) TW Pictoris
Another unusual unexplained astronomical object is the TW Pictoris star.
It is a white dwarf. Astronomers know very well this type of star.
White dwarfs are dense, dim, stellar corpses — the last observable stage
of evolution for low- and medium-mass stars. Whilst most massive stars will eventually go
supernova, a low or medium mass star with a mass less than about 8 times
the mass of the sun will eventually become a white dwarf, according to NASA. Approximately
97% of the stars in the Milky Way will eventually become white dwarfs, according to researchers.
One of the things that we know for sure about white dwarfs is that
they like to be bound in binary systems. In that case, usually at a certain point
one of the two stars starts feeding the other, and a surrounding accretion disk is formed.
TW pictoris is a cataclysmic variable system located about 1,400 light-years
away in the constellation of Pictor. The accretion disk is fuelled by hydrogen
and helium from its smaller companion star. As the white dwarf accretes it becomes brighter.
Using data from the TESS space telescope, astronomers found the white dwarf in TW Pictoris
lose brightness in 30 minutes, a very small amount of time if compared to the others
previously seen to occur in other systems over a period of several days to months.
To see the brightness of TW Pictoris plummet in 30 min is in itself extraordinary as it has
never been seen in other accreting white dwarfs and is totally unexpected from our understanding
of how these systems are supposed to feed through the accretion disk. It
basically appears to be switching on and off. Because the flow of material onto the white
dwarf’s accretion disk from its companion star is relatively constant it should not drastically
affect its luminosity on such short timescales. Instead, the astronomers believe what they are
witnessing could be reconfigurations of the white dwarf’s surface magnetic field.
When the brightness is high, the white dwarf feeds off the accretion disk as it normally would.
But then abruptly the system turns ‘off’ and its brightness plummets.
Scientists thoughts this happens because at that point the magnetic field is spinning so rapidly
that it stops the fuel coming from the accretion disk.
After some time, the system sporadically turns ‘on-again, and the brightness
increases back to its original level. More of this type of situation must be seen
(and probably will be), but so far...nothing yet: TW Pictoris seems to be really unique.
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1) Weird exoplanets and uniqueness of the solar system
One thing that we know for sure about our solar system is that...it seems to be pretty unique.
Since the first discovery of exoplanets (and therefore,
since the first discovery of another planetary system),
we have always found evidence for planets that are pretty different from the ones we are used to.
For example, a lot of planets were detected with the mass of Jupiter, orbiting really close to
their host star, the famous Hot Jupiters. Also, we discovered small planets orbiting
really close to their host stars, and sometimes these stars are pretty different from our sun.
Maybe they are colder stars and so planetary atmospheres can be pretty different from the
ones we are used to in our solar system. But the most important question is:
our solar system is the only planetary system we know which hosts life.
Is it possible to find life on an exoplanet? And where are we supposed to find it?
Maybe on an Earth-Sized planet? Well, if that was the case, everything
would be harder, because it's difficult to detect Earth-sized planets orbiting around other stars.
Also, we think we are biased, in the sense that our instrumentation and detection techniques are.
Some methods are able to preferentially discover Hot Jupiters, and others are giving us precious
information about smaller planets. This doesn't mean that Hot Jupiters are the
vast majority of the planets. It is more likely that we are lacking technology and instruments.
It could also be that Earth-like planets are merely
rare and that would be something to explain. Anyway, as we characterize our ever-growing sample
of exoplanets, it should become apparent whether the solar system truly is a rare configuration,
or if it has analogues in the local neighbourhood of stars.
Do you think another solar system could exist?
"This video ends here! Thanks for watching everyone! What's the most unusual object you
heard of? Let us know in the comment below! See you next time on the channel!