Far from the Sun's protective embrace, the frontier of our Solar System appears to be
a cold, empty, and dark place. For a long time, the yawning space between
us and the nearest stars was supposed to be a terrifyingly enormous stretch of nothingness.
It was a place that humanity could only observe from a distance until lately. It received scant
attention from astronomers who preferred to direct their telescopes on the blazing masses
of our nearby galaxies, stars, and nebulae. However, two spacecraft built and launched
in the 1970s have been beaming back our first sights of this weird zone we call interstellar
space for the past few years. They are the first man-made objects to depart our Solar System and
are travelling billions of kilometers away from Earth. No other spacecraft has travelled that far.
Stay with us until the end as today we have something spooky and strange
discovered in the vastness of space. These two spacecrafts have revealed that
beyond the boundaries of our solar system lies an invisible region of chaotic, frothing activity.
"When you look at different parts of the electromagnetic spectrum, that area of
space is very different from the blackness we see with our eyes," says Michele Bannister,
an astronomer who studies the Solar System's farthest reaches at the University of Canterbury
in Christchurch, New Zealand. "Magnetic fields are fighting, pushing, and becoming entangled
with one another." "Imagine yourself in the plunge pool beneath Niagara Falls."
Instead of tumbling water, however, the turbulence is caused by the solar wind - a continual,
intense torrent of charged particles, or plasma, spewing out in all directions from
the Sun - colliding with a cocktail of gas, dust, and cosmic rays that sweeps between
star systems, known as the "interstellar medium." Observations using radio and X-ray telescopes have
helped scientists' piece together a picture of what the interstellar medium is made of throughout
the last century. They discovered that it is made up of extremely diffuse ionized hydrogen atoms,
dust, and cosmic rays intermingled with dense molecular clouds of gas,
which are assumed to be the genesis of new stars. However, its precise nature just outside our solar
system has remained largely unknown, owing to the fact that the Sun, all eight planets,
and a distant disc of debris known as the Kuiper Belt are all housed within a massive protective
bubble generated by the solar wind known as the heliosphere. As the Sun and its planets
hurtle across the galaxy, this bubble acts as an invisible shield against the interstellar medium,
keeping the majority of dangerous cosmic rays and other debris out.
However, its life-saving properties make studying what lies outside the bubble more
challenging. Even estimating its size and shape from within is challenging.
“It's like you're inside your home and you want to know what it looks like. You have to
go outside and take a look to really tell,” says Elena Provornikova, a postdoctoral researcher at
the Johns Hopkins University Applied Physics Laboratory. “The only way to get an idea is to
travel far away from the Sun, look back, and take an image from outside the heliosphere.”
This is no easy task. Our Solar System appears to be the size of a grain of rice floating in
the middle of the Pacific when compared to the entire Milky Way. Even so, the outer border of
the heliosphere is still so far away that it took the Voyager 1 and Voyager 2 spacecraft more than
40 years to reach it as they raced from Earth. Voyager 1, which took a straighter path through
the Solar System, entered interstellar space in 2012, followed by Voyager 2 in 2018. They are
currently 14 billion and 12 billion miles from Earth, respectively, and are presently drifting
out into space beyond our Solar System, sending back more data as they travel.
What these two ageing probes discovered about the heliosphere-interstellar medium boundary has
provided new insights into how our Solar System evolved and how life on Earth is even viable. The
extreme edge of our Solar System, far from being a defined boundary, churns with turbulent magnetic
fields, colliding stellar windstorms, storms of high energy particles, and whirling radiation.
The size and form of the heliosphere bubble change as we move through different regions of
the interstellar medium and as the Sun's output changes. When the solar wind rises or falls,
the outer pressure on the bubble changes. The Sun's activity spiked in 2014, causing
what amounted to a solar-wind hurricane to sweep out into space. At over 800 miles per second,
the blast swept over Mercury and Venus. After two days and 150 million km, it enveloped Earth.
Fortunately, our planet's magnetic field protected us from the harmful radiation.
A day later, the gust passed Mars and continued through the asteroid belt toward the distant gas
giants - Jupiter, Saturn, Uranus, and, after more than two months, Neptune, which orbits
the Sun almost 4.5 billion kilometers away. After more than six months, the wind eventually
reached the "termination shock," a position more than 13 billion kilometers from the Sun.
Here, The Sun's magnetic field, which propels the solar wind, weakens to the point where
interstellar medium can push against it. The solar wind gust exited through the
termination shock at less than half its prior speed, reducing the hurricane to a tropical storm.
Then, in late 2015, while still inside our Solar System, the solar wind surge approached Voyager 2,
which is about the size of a compact car. Voyager's 40-year-old sensing technology,
powered by a slowly failing plutonium battery, detected the plasma surge.
The probe sent data back to Earth, which took 18 hours to reach us even at the speed of light.
Astronomers could only receive Voyager data thanks to a gigantic array of 70-meter satellite dishes
and advanced technology that could not have been envisioned, let alone invented,
when the probe left Earth in 1977. After a little more than a year,
the dying wind reached Voyager 1, which had entered into interstellar space in 2012.
The data revealed that the turbulent boundary is millions of kilometers thick. It covers billions
of square kilometers around the surface of the heliosphere. But many questions remain unanswered,
including those around exactly how typical our protective solar-wind bubble might be.
Well, the solar wind was one type of energy the voyagers caught but then a group of scientists
discovered "something unexpected" while mapping out the universe - an unknown object emitting
bursts of energy every 18 minutes. This mysterious object in space is
pulsing in a way astronomers have never seen before. It may be a strange neutron
star – the remnant of a massive star that has exploded. Examining celestial objects like it
could help us grasp the dying days of stars. When a big star runs out of fuel and collapses,
neutron stars arise. The very center of the star, known as the core, collapses, compressing every
proton and electron into a neutron. If the core of the collapsing star is between 1 and 3 solar
masses, the newly generated neutrons can arrest the collapse, leaving behind a neutron star.
(Stars with higher masses will continue to collapse into stellar-mass black holes.)
This collapse leaves behind the densest object known – an object with the mass
of a sun squished down to the size of a city. These stellar remnants are around 20 kilometers
across. On Earth, one sugar cube of neutron star material would weigh nearly 1 trillion
kilograms - roughly the weight of a mountain. Natasha Hurley-Walker of Curtin University in
Perth, Australia, and her colleagues discovered this object with the Murchison Widefield Array
(MWA), an Australian radio telescope. After noticing a barrage of radio waves that appeared
and then vanished, scientists went through archival data collected by the MWA in early
2018 and discovered 71 further pulses. The object, known as GLEAM-X and located
approximately 4000 light years away, discharged massive amounts of energy with each pulse.
In a press conference, Hurley-Walker observed, "The brightness here is just crazy - really,
really, really extreme." “We did not expect to find anything so bright.”
It had a consistent rhythmic pulse, brightening once every 18.18 minutes for 30 to 60 seconds.
Nothing like this has ever been discovered; the majority of flashing radio objects in the sky
pulse at a much faster rate, brightening and dissipating in a matter of seconds. “No one
really thought of looking for objects on this timescale because we couldn’t
think of any mechanisms that produce them, and yet they exist,” said Hurley-Walker.
Other observations of the object's light suggest that it must have a strong magnetic field,
and the pulses suggest that the object is likely spinning. This led the researchers to
think it might be a magnetar, a kind of neutron star with an especially potent magnetic field,
although it's unclear how a magnetar could rotate so slowly and glow so brightly.
“I was concerned that it was aliens, but… it is across a very wide range of frequencies, and that
means it must be a natural process – this is not an artificial signal,” said Hurley-Walker. She and
her colleagues are now looking for more objects like this so we can figure out what they are.
Due to the fact that they are often the remnants of a massive star that has died,
astronomers have previously discovered objects in space that periodically switch on and off.
These light bursts are referred to as transients, according to co-author and
Curtin astrophysicist Gemma Anderson. But what makes this object unusual is
that it doesn't behave like a transient. Energy bursts would erupt over the course of a few days
in a slow transient before going away for several months at a time. One flash lasting up to a minute
would be unusual because fast transients often flash on and off within milliseconds or seconds.
Though they do have some educated suggestions, the team is still unsure of what it might be.
Hurley-Walker speculates that it might be a "ultra-long period magnetar," a particular
kind of slowly rotating neutron star with a powerful magnetic field. But it was regarded
as something that only existed in theory. "Nobody expected to directly detect one
like this because we didn’t expect them to be so bright," Hurley-Walker said. "Somehow it’s
converting magnetic energy to radio waves much more effectively than anything we’ve seen before."
The mystery object is similar to a lighthouse, according to Seth Shostak,
senior astronomer at the SETI Institute who was not part in the research. He believes that most
astronomers agree with Hurley-Walker that it is most likely a dead star.
Shostak mentioned that once the Square Kilometer Array telescope is finished,
it will be the largest radio telescope ever designed and built. This will allow astronomers
to examine space even more, which could lead to the discovery of additional objects similar
to this in the future, as well as a more precise understanding of what they are.
What do you believe this object is? Is it a dead star or something alien? Tell us in the comments.