The
universe is full of mysteries, and sometimes, even the most familiar celestial bodies can
surprise us with something truly shocking.
Case in point: the Andromeda galaxy, which has always been a subject of intense scientific
scrutiny owing to its proximity to us.
However, the latest revelation about Andromeda from the cutting-edge James Webb Space Telescope
has left scientists baffled and fearful.
What could be the discovery that shakes up our understanding of this galaxy and possibly
even affects our own planet?
Join us as we embark on a thrilling journey to uncover the terrifying truth that the JWST
has uncovered about Andromeda.
The Andromeda galaxy, our closest cosmic neighbor, is a mysterious, distant wonder that can only
be seen with the naked eye on a clear night from a very dark location.
To the unaided eye, it appears as a fuzzy patch of stars about half the width and length
of the full moon.
But with a powerful telescope, you can see that it's actually six times larger than that.
Like our Milky Way, Andromeda is a spiral galaxy with a concentrated bulge of matter
at its center, surrounded by a disk of gas, dust, and stars, and an enormous halo.
Despite containing a trillion stars compared to the Milky Way's 250 billion, the Milky
Way is larger because it's believed to have more dark matter.
Andromeda has been known to humans for centuries.
The first known report of our nearest neighbor was by the Persian astronomer Abd Al-Rahman
al-Sufi, who described it as a small cloud in 964 in his book of fixed stars.
But it wasn't until the 1920s that astronomers began debating whether it was a separate galaxy
or part of the Milky Way.
The debate was finally settled in 1925 when Edwin Hubble discovered a Cepheid variable
within Andromeda, allowing for precise distance measurement.
This discovery led to the realization that the fuzzy patch of stars was too far away
to be contained within the Milky Way, leading to Hubble's conclusion that the Universe was
expanding.
Further observations of Andromeda, including radio maps created in the 1950s and recent
studies, have given us an even better understanding of the size and complexity of this fascinating
galaxy.
In 2015, the Hubble Space Telescope gave us an incredible surprise - the halo surrounding
the Andromeda galaxy was six times larger and a thousand times more massive than previously
thought!
Some experts even speculated that the Milky Way could have a halo too, and that the two
galaxies' halos might be in the process of merging.
This discovery is backed up by new estimates of the galaxy's size made in 2005 and 2007
based on observations of star motions.
The Hubble Space Telescope mosaic of Andromeda released in 2015 is the most detailed image
of the galaxy ever captured.
It took 7,398 exposures over 411 telescope pointings to create the image, revealing over
100 million stars, dust structures, and other features.
This groundbreaking image will help scientists extrapolate the structure of spiral galaxies
that are even further away from us, making them easier to study in detail.
However, in 2017, researchers found not just one but two supermassive black holes, which
were so tightly intertwined that they could barely be distinguished from one another.
That's not all - earlier studies using NASA's Chandra X-ray telescope identified a whopping
26 black hole candidates in Andromeda, the largest group ever seen in any galaxy besides
our own.
The Nuclear Spectroscopic Telescope Array found an additional 40 black holes in 2016,
further cementing the galaxy's reputation as a black hole haven.
But it's not all about black holes - in 2017, astronomers also detected gamma ray radiation
that could indicate the presence of dark matter, an elusive substance that scientists believe
holds galaxies together.
However, with the James Webb Space Telescope up and running, scientists now have a powerful
new tool to explore and expand our knowledge of Andromeda.
One of the exciting things the JWST allows astronomers to investigate is the newly detected
mass migration of stars converging on Andromeda.
We already know that galaxies grow by merging with other galaxies, a phenomenon currently
happening in our own Milky Way.
However, scientists have recently discovered evidence of an ancient mass migration of stars
into another galaxy for the first time.
They found over 7,000 stars in Andromeda that merged with the galaxy approximately 2 billion
years ago.
The James Webb Space Telescope is at the forefront of studying this growth and evolution of galaxies.
While the JWST is the star of the show, it's not the only telescope that can shed light
on this problem.
The Dark Energy Spectroscopic Instrument (DESI) has made significant new observations of Andromeda
and the inward migration of stars.
Designed to evaluate the effect of dark energy on the expansion of the universe, DESI collects
optical spectra from tens of millions of objects, mainly galaxies and quasars, and creates a
3D map of the results.
Similar to the more well-known Gaia spacecraft, which aims to map the positions and motions
of billions of stars in the Milky Way, DESI's data has led to a slew of new discoveries
about our own Galaxy.
However, it is limited to mapping stars in the Milky Way.
And now, for the first time, scientists have been able to capture a detailed map of the
stars in Andromeda using DESI, revealing their fascinating history.
This map includes the motions of almost 7,500 stars in the Andromeda galaxy's inner halo
and provides insight into the galaxy's growth and evolution.
The DESI observations have uncovered evidence of a galactic immigration event in Andromeda,
which occurred about 2 billion years ago when another galaxy merged with it.
The 7,500 stars measured by DESI suggest that they originated from this other galaxy.
This discovery is detailed in a paper called "DESI Observations the Andromeda Galaxy: Revealing
the Immigration History of our Nearest Neighbor" that will be published in the Astrophysical
Journal, with Arjun Dey as the lead author.
The new findings reveal that the night sky is far from static, and galaxies like the
Andromeda and Milky Way are continuously growing by merging with smaller galaxies.
The Andromeda Galaxy's history appears to be similar to that of the Milky Way, with
both dominated by a single immigration event in their inner halos.
The structures resulting from this merger include debris streams, shells, rings, and
plumes, which scientists have never seen so clearly in the motions of stars before.
By studying this event in Andromeda, astronomers can learn more about the Milky Way's own ancient
history.
The authors of the paper write that while hints of coherent structures have previously
been detected in M31, this is the first time they've been seen with such detail and clarity
in a galaxy beyond the Milky Way.
The observations reveal a stunningly intricate structure of positions and velocities of stars,
streams, and chevrons, providing a wealth of insights into the Andromeda galaxy's history.
However, the discovery was not solely due to the positions and velocities of the 7500
stars, but also to their metallicity.
High metallicity stars were found in all of the merger's substructures, suggesting an
extended star formation history for the progenitor galaxy or galaxies, possibly more representative
of larger galaxies.
This study is a testament to the importance of mergers in the evolution and growth of
galaxies, highlighting similarities between Andromeda and the Milky Way.
Both galaxies' inner halos are dominated by stars from a single accretion event, with
Andromeda showing chevron-shaped kinematic substructures reminiscent of those found in
the Milky Way.
DESI played a crucial role in these discoveries, collecting spectra from 5,000 objects simultaneously
and mapping the large-scale structure of the universe while shedding light on how galaxies
emerge over time.
With just a few hours of observing time, DESI surpassed more than a decade of spectroscopy
with much larger telescopes.
This feat leaves us wondering what the more powerful James Webb Space Telescope will reveal
in the future.
And here's an incredible tidbit about the Andromeda galaxy that's sure to blow your
mind: it's on a collision course with our very own Milky Way!
You heard that right, these two massive galaxies are destined to merge one day in the far-off
future, and the JWST will help us understand more about this cosmic spectacle.
Picture this: a stunning spectacle of light as Andromeda grows bigger and bigger in the
sky, hurtling towards us at 70 miles or 113 kilometers per second.
Although the two galaxies are still 2.5 million light-years apart, scientists have confirmed
that the merging of these two cosmic giants has already begun.
This fascinating discovery was made by Project Amiga, which uses the Hubble Space Telescope
to study Andromeda and its surroundings in deep space and was published in the Astrophysical
Journal in August 2020.
With all this in mind, it's incredible to think that we're witnessing a cosmic event
that has been millions of years in the making and will continue to unfold for billions more.
The cosmos is full of mysteries, and one of them involves the elusive galactic halo, which
shrouds galaxies in a veil of gas, dust, and wandering stars.
This cosmic sheath is notoriously hard to detect, but astronomers have made significant
progress by studying background quasars to measure the halo of the Andromeda galaxy.
What they found was astounding: the halo of Andromeda stretches far beyond its visible
borders, reaching half the distance to our Milky Way and beyond in some directions, up
to 2 million light-years.
So, what does this mean for the collision of the two galaxies?
Well, although we cannot directly measure the properties of the Milky Way's halo from
our vantage point inside the galaxy, scientists think that since the Milky Way and Andromeda
are so alike, the Milky Way's halo will be comparable.
The faint halos of the galaxies appear to have started to intersect, hinting that the
merger between the two galaxies may have already commenced.
The galactic halo is just one of the many fascinating aspects of the universe that we
have yet to fully understand, but with every discovery, we inch closer to unlocking its
secrets.
Now you must be wondering what will happen to our solar system when this merger happens?
Well, according to scientists, there's a 50-50 chance that in a merged galaxy, the solar
system will be pushed three times farther away from the galactic core than it is now.
But that's not all, there's also a chance that the solar system might get kicked out
of the newly formed galaxy during the collision.
Although, you can rest easy knowing that this event will take place in such a distant future
that humanity will no longer exist.
And even if it does happen, the solar system won't be negatively impacted, and the chances
of the Sun or planets getting disrupted are quite low.