Colossal object found in the zone of avoidance!
Did you know Flamingos can be useful to study our universe?
No, no, I’m not talking about those pinky birds with a S shaped neck…
I’ll get to that later, but first…let’s take a step back.
If you ever happened to go out during the night, far from the city lights, you might
have seen the Milky Way. It’s something incredible, to be seen at
least once in your lifetime! This is how it looks like from the Atacama
Desert.
What we really observe is the internal part of our galaxy.
The solar system is rotating around the center, also called “bulge” of the galaxy, along
with millions of other stars, and when we look at the Milky way in the sky we are actually
looking towards more central regions in the disk.
The term ‘bulge’ is used to describe the dense spheroidal swarm of stars often found
in the centres of spiral and S0 galaxies. The bulge of the Milky Way appears to be
fairly typical – a slightly flattened sphere of radius ~6,500 light years – while bulge
sizes in other galaxies vary from several hundred to several tens of thousands of light
years, depending on the type and size of the galaxy.
If we look to the most central part, we notice the Milky Way is kind of faint, and even the
most powerful optical telescopes can’t do much about it.
It’s really hard to study the visible light coming from the stars in the bulge of the
Milky Way, because they are covered by clouds and dust. Such clouds and dust belong to our
galaxy, and they constitute a huge problem for astronomers. They named it “The zone
of avoidance”, because stars, interstellar dust and clouds block something like 20% of
the light coming from the central regions. The reason we can't see it — at least with
standard visible light telescopes — is because the Milky Way's bulging center blocks our
view of it; the center of our galaxy is so dense with stars, dust and other matter that
light from the zone of avoidance gets scattered or absorbed before reaching Earth's telescopes.
As a result, optical galaxy catalogues are usually incomplete close to the galactic plane.
The fantastic news is that astronomers have detected an enormous extragalactic structure
hiding in the zone of avoidance, proving that perhaps this region is not completely empty.
Follow me in this video to get to know more about it!
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The zone of avoidance is represented by this blank spot on our map of the universe:
It’s always been really hard for scientists to find some kind of object in the zone of
avoidance, but they have recently uncovered the zone’s secrets with telescopes that
can detect infrared radiation.
The infrared radiation is an electromagnetic radiation, just like the visible light. The
only difference is that, while on one hand human eyes are able to see the visible light,
they are not able to detect infrared waves. But astronomers are true experts of light,
and they know infrared light can give you a lot of important information about the universe.
Moreover, the infrared light has the well known property of being powerful enough to
shine throug dense clouds of gas and dust.
Just to get a sense of that, this is the view of the galactic center in four different wavelength
bands.
Atop, from a survey in the infrared; below that, in the mid-IR; below that, in the near-IR,
and at the bottom in visible light, where the dust obscures everything of interest.
If light was a car, the visible light would crash all the dust particles it finds along
the way, while infrared light would be so smooth in passing through the chaotic traffic
of the universe. In this way, the red light can reach our telescopes on Earth, and we
can unveil the secrets of galaxies, stars and planets.
============= Over time, astronomers have built a number
of infrared telescopes, both working from the ground or from space.
Some of the most important ones are the Spitzer space telescope and the James Webb Space telescope.
Among many other accomplishments in its 16 years of operation, Spitzer discovered a giant
ring of Saturn, revealed a system of seven Earth-size planets around a star 40 light-years
away, and studied the most distant known galaxies.
James Webb needs no presentations: I’m sure you know how powerful this brand new insturment
is and how beautiful the images it delivers us everytime. However, just in case you missed
it, here’s a summary of the major discoveries it made so far:
As for the telescopes on the ground, we have the infrared telescope facility at Mauna Kea,
Hawaii, or the infrared observatory of Wyoming.
Mauna Kea observatory, for instance, was used to confirm EGS-zs8-1’s age, a really ancient
galaxy, born right after the big bang.
In order to assess its age, astronomers used a powerful spectrograph at Mauna Kea called
Mosfire. This device measured the redshift, or its light broadening to longer wavelengths,
of EGS-zs8-1. Wow!
Other infrared surveys of the universe have shown how external galaxies lie beyond the
zone of avoidance, and that the enormous mass concentration known as the Great attractor
lies within it!
It is a strange place in the sky where everything seems to be attracted.
Unfortunately, though, it is on the other side of the Milky Way, so we can’t see it
and we don’t really know what’s the reason of all this attracting.
The great majority of the galaxies close to the milky way is going towards the great attractror,
and we are, too! Who knows what lies out there!
In any case, this misterious object is not the only one we expect to find in the zone
of avoidance. For instance, the italian astronomer Paolo Maffei observed two distant galaxies,
for the first time in the sixties. They were named Maffei 1 and 2, and they lie near the
boarder between the constellations Perseus and Cassiopeia.
Maffei 1 is a large elliptical galaxy, while Maffei 2 has a spiral structure.
Now, researchers have combined data from several infrared surveys, and they found the most
colossal structure ever detected in the zone of avoidance.
This structure, if it really exists, is located approximately 3 billion light-years from Earth,
and it consists of a large cluster of galaxies. Galaxy clusters are the largest objects in
the universe that are held together by their own gravity. They contain hundreds or thousands
of galaxies, lots of hot plasma, and a large amount of invisible dark matter. The Perseus
Cluster, for example, has more than a thousand galaxies and is one of the most luminous sources
of X-rays in the sky. Galaxy clusters are home to the biggest galaxies in the known
universe, and provide us with information about the structure of the universe on the
largest scales.
So… a bunch of new galaxies bounded together by their mutual attraction, with a shared
center of gravity. But how many galaxies did the team find? And how was such an incredible
discovery possible? Hey, if you are still watching, it means you
really like this video! Why don’t you subscribe and press the notification bell?
The team was able to spot this cluster within the Zone of avoidance using the VVV Survey,
a project that scans the Milky Way bulge at infrared wavelengths using the European Southern
Observatory’s Visible and Infrared Survey Telescope for Astronomy (VISTA) in Paranal,
Chile. As was stated in the project: “the main
purpose of the wide field survey telescope and camera facility is to perform extensive
surveys of the southern skies whose sensitivity is matched to the needs of today’s 8-m class
telescopes.” The discovery of this cluster was only possible
because, as we’ve said earlier, longer wavelengths of light, including in the infrared band,
are able to travel through the Milky Way’s haze to reach telescopes on Earth.
An instrument called Flamingo-2, installed on the Gemini South Telescope in Chile, gave
crucial help to the team. FLAMINGOS-2 is a near-infrared imaging spectrograph, meaning
that it can give us important informations on the nature of the objects it observes.
For isntance, it allowed to identify measurements of redshift, that can be used to estimate
the distance and velocities of objects in space.
The team is quite sure whatv they observed is a cluster of galaxies, because they picked
some samples in the cluster and they used Flamingos-2 to study the spectra of these
objects. Here is a sneak peak of the original paper,
still to be peer reviewed, that shows the absorption features of these objects, as detected
by Flamingos-2. All of them are compatible with galactic spectra, as stated in the paper.
In fact, the spectral lines detected in the majority of galaxies are FeI, SiI, TiI, and
MgI. Besides that, CrI, KI, CaI, and MnI lines have been detected in some cases, as can be
seen in the picture.
The team estimated the cluster is huge, containing something like 58 galaxies, but i twill take
time and more observations to be sure of its accurate mass and content. We can say for
sure that… it is massive.
Besides the discovery of 58 new galaxies, the detection of this colossal object shows
that the zone of avoidance may not be as inscrutable as was once thought. Future infrared studies
— including potential observations by the James Webb Space Telescope, will further help scientists
unlock the hidden secrets beyond the Milky Way's bulge.
As you can understand, every single corner of our universe is full of surprises. New
discoveries are awaiting for us, we just need the proper instrumentation and the right passionate
people.
Hey! My talk ends here! Thanks for watching! Make sure to like the video, and maybe turn
on the notifications! See you next time!