The universe is full of both verified and hypothesized objects that do not fit neatly
into the humdrum world of standard classes of planets, moons, galaxies and well understood
phenomena.
So here are ten bizarre deep space astronomical objects that have either been discovered,
or may well exist out there somewhere amongst the stars.
Number 10.
Moonmoons
One of the most common questions I get is can a moon have its own moon.
And, the answer is yes, or so it’s thought.
While no example of this kind of object has ever been discovered, it’s one of those
instances in astronomy that seems likely to eventually happen.
It’s the concept of a subsatellite, or moonmoon, where a moon of a planet has a moon of its
own.
While in most cases this isn’t likely to occur in a planetary system, there are situations
where it can.
And, indeed, we ourselves have created artificial moonmoons in orbit of our own moon, though
doing so is tricky.
There are however natural candidates for this.
Saturn’s moon Iapetus has a very pronounced unusual ridge extending around it that may
have been caused by a past moonmoon.
But even stranger is the case of Saturn’s moon Rhea.
Last year, what appears to be a ring system was discovered around this moon, creating
the odd situation of a ringed moon orbiting a ringed planet.
It was determined that if it had a ring system, the tiny moon could have a stable moonmoon
in principle.
A search of the data from the Cassini mission has failed to find such a moon, but it does
tick a box in favor of moonmoons existing in the universe.
Number 9.
Rogue Planets
At first glance, interstellar space may seem very empty other than dust and the occasional
atom of hydrogen.
But in reality, interstellar space also hosts an entire class of planet that sits alone
from planets confined in star systems.
They are rogue planets.
Rogue planets typically start as members of star systems, but instabilities within those
systems leads to their ejection.
Indeed, it’s thought by some scientists that early in the solar system’s history,
a Neptune sized planet that formed here was ejected through a close encounter with Jupiter.
Where that planet is now is anyone’s guess, but having been ejected an estimated 4 billion
years ago, it’s very likely very far away.
One candidate for a free floating rogue planet is an object known as SIMP J013656.5+093347.
Once thought to be a brown dwarf, the size of this planet has been constrained down to
12.7 Jupiter masses, making it seem like more of a massive planet than a brown dwarf, though
the line is blurred.
This object is particularly interesting because variations in its light curve have been interpreted
as variations in cloud patterns in its atmosphere, and indeed evidence for very powerful auroras
has also been found, suggesting the planet has a very strong magnetic field.
Apart from giant worlds, there should be a population of smaller rogue planets as well,
including planets that might have otherwise have been similar to earth.
Interestingly, the concept of a rogue planet wandering the darkness of interstellar space
doesn’t seem conducive to life ever arising in such a place, but with geothermal heating
such a planet could have liquid water.
Who knows where lifet might get a foothold, though it might seem rather sad if a rogue
planet is ever discovered that had evidence of life, but that life went extinct long ago
when the planet froze over in the depths of space.
Number 8.
The Anti-Matter Fountain
The matter/Anti-matter reaction is the ultimate in efficiency.
If you have exactly one gram of matter, and one gram of anti-matter, and put them together
they will violently annihilate each other in a 100 percent conversion of mass into energy.
But there is a rabbit hole here.
There’s no clear reason why the big bang wouldn’t have produced equal amounts of
matter and anti-matter.
But for some reason, not yet understood, it seems that slightly more matter was created
than anti-matter, allowing for the universe’s matter to exist today as we see it.
But, anti-matter can still be created, even in nature.
At the center of the galaxy lies an anti-matter fountain that spews massive amounts of positrons
out, which then go on to annihilate on contact with normal matter.
What’s actually at the heart of the fountain producing this material is unknown, but hypotheses
range from them being somehow created by a black hole, or even that they are somehow
being created by some reaction involving dark matter, though no one knows how that would
even work.
Number 7.
The Double Quasar
This entry is a kind of two for one punch in strangeness, not only because of the nature
of what it is, but also a strange occurrence associated with it that was caught entirely
by pure chance.
In 1979 the object QSO 0957+561 was discovered.
Initially, it appeared to be two quasars located very close to each other, something that seemed
unlikely.
As study of the object progressed, it was realized that the two quasars were so similar
that they would essentially have to be twins, making the whole thing even more unlikely.
Later, instead of being two quasars, it was found that they were actually two images of
the same quasar that were being gravitationally lensed by a galaxy in the foreground.
This was one of the first gravitationally lensed objects ever found, and confirms Einstein’s
view of space-time being warped, and capable of lensing objects.
And, there’s an interesting effect with this case.
Any change in the quasar is seen in one image, but because the other image represents a slightly
different path, the same change is not seen in the other image for over a year later.
This quasar also happens to be extremely distant at 7.8 billion light-years, and the galaxy
that is in front just over half that This led to a strange incident in 1996.
Astronomers caught an odd dip in the light of the quasar.
Unfortunately, it can’t ever be confirmed, but one idea that’s on the table for this
dip is that it was caused by the transit of a 3 earth mass exoplanet in front of the quasar.
This would place that exoplanet within the galaxy that’s lensing the quasar, and would
be by far the most distant exoplanet ever detected, at a whopping four billion light-years.
Number 6.
Omega Centauri
The Milky Way is full of spectacular star clusters.
These are full fledged members of our galaxy, having formed here.
But one stands out.
Omega Centauri.
And it’s not just any star cluster, it’s very brightly visible from earth, even at
a distance of nearly 16,000 light-years.
And, it basically breaks most of the rules that define globular star clusters in the
Milky Way.
For example, a typical star cluster of the Milky Way has hundreds of thousands of stars,
such as M-80, which is visible in small telescopes.
By contrast, Omega Centauri has millions of stars.
Globular clusters in the Milky Way tend to be a bit homogenous as far as the types and
ages of the stars within them.
Omega Centauri is not like this at all, and contains a varied profile of stars, all born
at different times, evidenced by their types and metallicities.
And the whole thing is spinning, which normal star clusters tend not to do.
All of this points to an unusual origin for Omega Centauri.
Rather than being a member of the Milky Way, it may not be from here at all and could represent
the nucleus of an entire other galaxy that the Milky Way absorbed and cannibalized at
some point until all that was left was the core.
This would mean that scattered across the Milky Way are stars and possibly planets from
another galaxy entirely.
And, this process of galaxy mergers has not stopped, indeed, we are currently careening
towards the great Andromeda Galaxy for a merger in about 4.5 billion years.
Number 5.
Hoag’s Object
When this object was first discovered, it wasn’t immediately clear just what it was.
One idea is that it was something similar to the double quasar, in that it was a quasar
behind a foreground elliptical galaxy that was being gravitationally lensed around it.
This did not turn out to be the case however, and as it turned out the object is actually
a cohesive galaxy.
Yet, it’s structured very differently from normal galaxies.
Instead of a normal spiral galaxy structure, this object has a core of older yellower stars,
then a large gap, and then a blue outer ring of generally younger stars.
There aren’t any dead ringer answers on just how this came to be, but on the table
is a very specific encounter with another small galaxy where it barreled through rapidly
and creating the effect.
But this would have had to have happened relatively recently, and no small galaxy seems to be
in the vicinity.
Another is that it is the result of some type of instability that can happen in barred galaxies,
yet Hoag’s object doesn’t appear to have ever been a barred galaxy.
No option fully explains just how Hoag’s object came to be this way.
And, it’s unique.
While there are other ring type galaxies, they are very rare, and none are quite like
Hoag’s object.
And to add another enigmatic twist to this story is that as rare as they are, there is
a second ringed galaxy at a completely different distance and totally unrelated to Hoag’s
object that just happens to be lined up just so as to appear within the gap of Hoag’s
object.
The chances of two very rare galaxies appearing like that are, well, astronomical.
Number 4.
SN2006gy
It’s hard to envision anything more cataclysmic than a supernova.
There are two main types, Type I where a white dwarf gains material from a companion star
until the accruing mass causes the white dwarf to begin fusing carbon, and the star explodes.
Type II is the more familiar stellar collapse of an old star ending its life by imploding
and exploding.
But there appears to be a rarer third type, and one was witnessed in 2006.
This was SN2006gy, and exploded with a violence estimated to be as much as 100 times the power
of a normal supernova, in essence, a hypernova.
Stars that can do this must be enormous, the largest stars in the universe, and the rarest.
And, they don’t live long, they tend to only live for a few tens of millions of years
before exploding.
While it’s not entirely clear how these massive explosions occur, one idea is that
stars this massive produce gamma rays, and that in turn can create matter/anti-matter
pairs.
This creates a matter anti-matter reaction as they annihilate each other, which then
goes out of control inside the star causing it to collapse and explode.
This type of supernova is odd in another way, in a normal Type II supernova, a neutron star
is left behind.
But in the case of these giant supernovas, the star is entirely blown up.
And, another of these is coming.
And it will be much closer.
SN2006gy was in another galaxy entirely, but the Milky Way star Eta Carinae is just this
type of star, and it could explode at any time.
When it does, it won’t pose a threat to earth, but will be a spectacular sight, and
will probably be visible from earth even in daylight for a time.
Number 3.
Thorne-Zytkow Objects
These strange objects are still only hypothesized to exist, though there are candidates for
them, and likely do exist, though are probably rare and probably limited to very dense areas
of stars, such as globular clusters and very special circumstances in binary star systems.
So rare that there could be as few as 20 of these objects in the Milky Way at any given
time.
A Thorne-Zytkow object forms when a neutron star collides with a giant star and essentially
becomes engulfed within it.
If the combined two are of a high enough mass, the whole thing will collapse into a blackhole,
and probably creating yet another type of supernova.
If not, the strange state of affairs will eventually result in a single, more massive
neutron star.
While no confirmed thorne-zytkow object has ever been discovered, there are several candidates.
And one particularly interesting system where an F type star is being orbited by an unseen
object, likely a black hole.
It’s thought that this system GRO J1655-40 might have went through a stage as a thorne-zytkow
object.
Number 2.
Stephan’s Quintet.
This strange case is an instance where one solved mystery leads to another.
That is not uncommon in science, to say the least.
But in this case solving the first mystery ended up reopening the very same question.
The objects in question are a group of galaxies known as Stephan’s quintet and the mystery
involves red shift.
Red shift is a major way of determining distance and motion in the universe, in this case the
distance to these galaxies.
At first glance, the galaxies in the quintet appeared intertwined, as if they were all
physically connected with each other.
But there was a problem.
The redshift of one of the galaxies, the one at the lower left, indicated that it was only
about 30 million light years away, whereas the rest were ten times more distant.
So, how could they be interacting?
Were scientists completely wrong about red shift?
This led to questions about whether red shift can be trusted.
This was an uncomfortable prospect, because if it had been wrong, then we’d be wrong
about distances in the universe, and even the size of the observable universe.
It wasn’t until the year 2000 that the mystery was finally solved using the Hubble Space
telescope.
They imaged the galaxies, and found that the oddball galaxy’s individual stars could
be resolved, and the other galaxies could not be.
In short, it was an optical illusion, and the oddball galaxy had to be ten times closer,
and the reliability of red shift was safe.
Or was it?
Not long after, the mystery arose again, in the same group of galaxies.
Another of the galaxies had an odd star-like feature near its nucleus.
Spectroscopy showed that the object is in fact a quasar with an enormous red shift,
suggesting that it’s billions of light years further away than the galaxy is.
Yet it appears to be in front of the galaxy and interacting with it.
In the end, Stephan’s Quintet opened up more questions than it answered.
Is there something wrong with red shift?
Is there just a chance hole in the galaxy that allows the quasar to be visible and the
interaction just an illusion?
Is there something wrong with our interpretation of quasars?
The questions are open.
Number 1.
Diamond Planets
Carbon is a very common element in the universe, and indeed forms the basis for the chemistry
of life itself.
In protoplanetary disks, it should be possible that ones rich in carbon, but poor in oxygen
might exist.
These would in turn form a very different kind of planet to anything in our solar system.
A carbon planet.
While there is at least one candidate for this type of planet, 55 Cancri, none have
been confirmed.
That particular planet seems to have a surface made up of graphite and diamond, but it’s
also very hot.
Carbon planets would be very different planets indeed.
If a carbon planet has sufficient pressure internally, it might maintain a thick layer
of diamond from which material might be transported to the surface through volcanism, creating
diamond volcanos, such as what might be happening at 55 Cancri.
Cooler versions of these planets might sport liquid hydrocarbons on their surfaces, but
what the probably wouldn’t have is water.
That doesn’t preclude life on a world like this, any more than it does on Titan, but
that life would probably be forever microbial, if it could happen at all.
But within this is an even stranger object that probably can’t even be called a planet,
though it would look like one.
Orbiting the millisecond pulsar PSR J1719-1438 is a planet like object that appears to be
made almost entirely of solid diamond.
It’s known to be very small, yet has a mass similar to Jupiter.
But this object didn’t start out as a planet at all, but rather a star.
This spherical chunk of diamond is the remnant of an apparently evaporated white dwarf.
In short, it’s a diamond star cinder.
Thanks for listening!
I am futurist and science fiction author John Michael Godier and be sure to check out my
books at your favorite online book retailer and subscribe to my channels for regular,
in-depth explorations into the interesting, weird and unknown aspects of this amazing
universe in which we live.