Howdy stargazers and welcome to this episode of Star Trails.
I'm Drew and I'll be your guide to the night sky for the week starting March the 2nd through
the 8th.
This week Mercury makes its presence known on the western horizon.
We check in with the Blaze Star and with recent talk of a potential asteroid collision with
Earth, spoiler alert, it's not going to hit us.
We'll take a detailed look at space rocks, their dangers, and what can be done about them.
So grab a comfortable spot under the night sky and let's get started.
We begin the week with a beautiful crescent moon in the western sky, just three days past
new, glowing at about 10% illumination on the evening of March 2nd.
By March 7th the moon reaches its first quarter phase making it a perfect target for binoculars
or a small telescope as its craters and mountain ranges cast dramatic shadows along the terminator line.
Planets are putting on a show this week too.
Venus now in retrograde will shine brilliantly in the western evening sky after sunset and on March
the 2nd it will form a stunning pairing with the crescent moon.
So be sure to step outside and catch that celestial duo.
Meanwhile, Mercury is making a rare and fleeting appearance, reaching its greatest eastern elongation
on March 8th, meaning it will be at its best visibility for this period.
Look low on the western horizon shortly after sunset and you just might spot this elusive inner planet.
We still have our eyes on T Corona Borealis, a star system that could erupt into a rare nova
at any moment.
This binary star located in the constellation Corona Borealis goes nova roughly once every 80 years,
meaning it might become visible to the naked eye for the first time since 1946.
Known as the blaze star, T Corona Borealis is expected to brighten from a dim magnitude of 10
which isn't visible to the naked eye to magnitude 2 which is as bright as Polaris.
Today we're talking about space rocks, asteroids, comets, meteors, and everything in between.
You might have heard the recent buzz about asteroid 2024 YR-4,
which briefly made headlines when early observations suggested a slim chance it could hit Earth in 2032.
Of course, more recent calculations ruled that out, reducing the risk to almost zero.
But it got me thinking, what else is out there, flying through space, occasionally paying our planet a visit?
From the massive asteroid that wiped out the dinosaurs to the Tunguska explosion that flattened a forest in Siberia,
these space rocks have shaped Earth's history.
And speaking of dramatic impacts, we can't forget Comet Shoemaker-Levy-9, which slammed into Jupiter in 1994,
giving us front-row seats to a cosmic collision of epic proportions.
So let's break it all down. What are these objects? Where do they come from? And should we be worried about them?
First up, asteroids.
Asteroids are rocky leftovers from the early solar system, basically the building blocks that never quite became planets.
Most of them orbit in the asteroid belt, a vast region between Mars and Jupiter that's home to millions of these space rocks.
Ranging from tiny pebbles to giant bodies hundreds of miles wide.
Some famous asteroids include Ceres and Vesta, which NASA's Dawn spacecraft studied up close.
Ceres is particularly interesting because it's large enough to be classified as a dwarf planet.
And scientists suspect it may have a subsurface ocean, hinting at the possibility of past or present life.
To learn more about Ceres, go back and check out Episode 46.
While most asteroids stay put in the asteroid belt, some venture closer to Earth.
These are called Near-Earth Objects, or NEOs.
This includes asteroids like Apophis, which once sparked fears of a collision in 2029,
though we now know it will safely pass by.
That brings us back to 2024, why are for?
When it was first discovered, its orbit was uncertain and there was a slim chance it could impact Earth.
But thanks to follow-up observations, astronomers refined its trajectory and ruled out any danger for now.
That's exactly why space agencies like NASA and the European Space Agency tracked thousands of NEOs.
Ready to sound the alarm if one gets too close.
Space rocks hit Earth's atmosphere every day, but most of the time they burn up as meteors, what we call shooting stars.
But sometimes they're big enough to cause real damage.
The most famous example is the Tunguska event of 1908, when a meteor, probably 60 to 100 meters wide,
entered Earth's atmosphere over Siberia and exploded 3 to 6 miles above the ground.
The blast flattened 800 square miles of forest with an energy release similar to a nuclear bomb.
For years, this event was a mystery.
No impact crater was ever found because the object exploded in mid-air.
A phenomenon called an air burst.
If this had happened over a major city, the destruction would have been unimaginable.
Now, fast forward to 2013, when something eerily similar happened over Chelyabinsk, Russia.
A 20 meter wide meteor entered the atmosphere at more than 40,000 miles per hour.
Creating a brilliant fireball that was briefly brighter than the sun.
Almost 30 kilometers above the city, it exploded with the force of 30 atomic bombs,
shattering windows and damaging buildings across six Russian cities.
Unlike Tunguska, this event was caught on thousands of dash cams,
giving us an unprecedented look at a real-life meteor explosion.
The shock wave injured 1,500 people, mostly from shattered glass,
serving as a stark reminder that even small space rocks can pack a serious punch.
The most infamous asteroid impact in history that we know of was the one that made the dinosaurs extinct.
66 million years ago, an asteroid roughly 6 miles wide slammed into what is now the year of the 19th century.
The impact created a crater, an enormous scar over 90 miles across.
The explosion released as much energy as 10 billion Hiroshima bombs.
It triggered tsunamis, wildfires and a global dust cloud that blocked out the sun, causing temperatures to plummet.
In the aftermath, nearly 75% of the earth's surface was destroyed.
In the aftermath, nearly 75% of all life on earth, including the dinosaurs, went extinct.
This single event reshaped evolution, clearing the way for mammals and eventually us to take over.
And here's the wild part.
Impacts of this magnitude aren't just ancient history. They could happen again.
Scientists estimate that asteroids large enough to cause global devastation hit earth every few million years.
Through the years, NASA has studied ways to alter the course of asteroids.
The most successful test of this has been the DART mission.
DART stands for Double Asteroid Redirection Test.
And in 2022, it became the first ever attempt to intentionally alter the trajectory of an asteroid.
The target was a small asteroid called Dimorphos, which orbits a larger asteroid named Dytamos.
Neither of these were a threat to earth, but they made the perfect test case for an asteroid deflection experiment.
NASA launched the DART spacecraft, a small probe about the size of a refrigerator,
and sent it crashing into Dimorphos at more than 14,000 miles per hour.
The idea was simple. If we could hit the asteroid hard enough, we could change its orbit just slightly.
And it worked.
Before impact, Dimorphos took 11 hours and 55 minutes to orbit Dytamos.
After the collision, that orbit shortened by 32 minutes, a much bigger change than scientists expected.
So how do we actually move an asteroid?
It comes down to momentum transfer, essentially a cosmic game of billiards.
When DART hit Dimorphos, it transferred its momentum into the asteroid.
But that's not all. What really made a difference was the ejecta.
The impact sent thousands of tons of rock and dust flying off into space,
creating a kind of recoil effect that amplified the push on the asteroid.
This was a huge breakthrough because it proved that if we ever find a real asteroid on a collision course with Earth,
we might be able to nudge it away given enough time.
DART was just the beginning.
Future missions like ESA's HERA probe will return to Dimorphos in 2026 to study the aftermath and help us redefine asteroid deflection techniques.
Another way to potentially move an asteroid is using a so-called gravity tractor.
This sounds like science fiction, a Star Wars tractor beam, maybe.
But it's actually based on the physics of gravity and how the mass of two objects affect one another.
Instead of slamming an asteroid at high speed, a gravity tractor spacecraft would hover near the asteroid and slowly pull it off course.
Here's how that works.
We send a heavy spacecraft to a threatening asteroid, big enough that its gravitational pull can have an effect.
The spacecraft parks near the asteroid, but instead of touching it, it hovers at a close distance.
Even though the spacecraft is small compared to the asteroid, it still has mass,
and its gravitational pull subtly tugs on the asteroid over time.
Over years or even decades, this tiny but constant force slowly nudges the asteroid off its collision course with Earth.
Of course, this method only works if we detect an asteroid threat decades in advance because the gravitational pull is very small and takes a long time to make a difference.
It also requires a spacecraft with significant mass, which means launching a heavy probe into deep space, something that would take a lot of planning and resources.
While Hollywood loves the idea of blowing up asteroids with nukes, Armageddon style, in reality, a gentle nudge decades in advance is a much safer and reliable way to protect our planet.
If asteroids are the rocky leftovers of the solar system, comets are the icy wanderers.
Comets are made of frozen gases, dust, and rock. They come from the Oort cloud and the Kuiper Belt, regions far beyond Neptune, where billions of these icy bodies orbit.
When a comet gets close to the sun, the heat causes its icy surface to sublimate, turning directly from solid to gas.
This creates the beautiful glowing coma and dust detail we see from Earth.
Unlike asteroids, comets don't usually pose a threat to Earth, but every once in a while, a rogue one might swing too close for comfort.
One of the most dramatic cometary events ever witnessed was the Shoemaker-Levy 9 impact on Jupiter in 1994.
This comet had been torn apart by Jupiter's gravity and over six days its fragments slammed into the gas giant, creating massive explosions larger than Earth itself.
The scars seen in Jupiter's atmosphere lasted for months.
This was the first time humans had ever witnessed an impact between two solar system objects in real time, and it showed how Jupiter acts as sort of a cosmic vacuum cleaner,
sucking in potential threats before they reach us.
Before we wrap up, let's talk about Earth's second moon. Well, sort of.
Recently, astronomers discovered 2024 PT-5, a small asteroid that's been caught in Earth's gravity, temporarily making it a mini-moon.
Unlike our actual moon, it won't be here long. It'll likely drift away within a few months.
Earth has had several of these temporary moons over the years. They're tiny, often no bigger than a car, and eventually slip away.
Perhaps one day they could be targets for future space missions.
I mentioned these mini-moons in more detail back in episode 38, in a discussion of orbital resonances in our solar system, so if you missed it, go back and give it a listen.
If you found this episode helpful, let me know and feel free to send in your questions and observations.
The easiest way to do that is by visiting our website, startrails.show.
This is also a great way to share the show with friends. Until next time, keep looking up and exploring the night sky.
Clear skies, everyone!