What you are seeing is a stellar nursery a complex of hydrogen gas surrounding a
population of newly formed stars. These new stars are massive and blow fierce
stellar winds which blow a giant bubble in the gas. But toward the southern end
of this region is a massive newly forming star twelve times the mass of
our Sun. And it is here that astronomers are catching a rare glimpse into the
creation of a stellar giant. Welcome back to Launch Pad, I'm Christian Ready, your
friendly neighborhood astronomer. Stars are huge spheres of hydrogen gas that
shine due to the energy released from hydrogen fusing into helium in their
cores. But that hydrogen gas has to come from somewhere, and that somewhere are
giant molecular clouds found all throughout our galaxy. These clouds are
in constant motion and collide with other clouds or sometimes get buffeted
by the shockwaves from nearby supernova explosions. When these
events happen the clouds will start to collapse. As they do so, a center of mass
is formed and material from the cloud begins to spiral in on top of it. This
central object starts to heat up and it's called a protostar for this reason.
This is star formation in a nutshell, or rather in a molecular cloud. But because
protostars are hidden deep inside the centers of these clouds, there's
still much about the process of star formation that is hidden from our view.
But by careful observation and by developing sophisticated computer models,
astronomers overtime built up a pretty good understanding of what's
going on as a star forms. As the rotating cloud collapses, it flattens into a disk
surrounding the protostar. Matter falls from this disk onto the protostar in a
process called accretion. That's a pretty simple model of how stars form, but
astronomers quickly understood that there were some problems with this idea.
As the rotating star acquires mass, it rotates faster and faster. If something
isn't done, the star would eventually rotate so fast that it would literally
rip itself apart before it was ever born. But as astronomers studied these newly
forming stars, they noticed patches of turbulent nebulosity
associated with them. It turns out that these blobs are formed by jets of highly
collimated material that's being expelled from the protostar in a bipolar
outflow. The Jets then slam into the interstellar medium, exciting and
ionizing in a process, causing them to glow. These objects were first studied in
detail by George Herbig and Giuliano Haro, and so we call these objects
Herbig-Haro objects in their honor. The jets are always bipolar, though sometimes
we can only see just one of the two jets because the other is hidden behind a
wall of gas and dust. By expelling mass in a jet, a protostar effectively dumps
angular momentum, keeping it from spinning up too rapidly and thus able to
continue to form. The actual specifics of how these jets are formed and launched
is still not yet well understood. It has something to do with matter falling from
the accretion disk and interacting with the rapidly rotating star's strong
magnetic field. It seems that the rotating star and magnetic field act as
a kind of giant turbine producing the jets in the process. But the specifics
are still a little bit fuzzy; after all these objects are still hidden deep
inside their stellar cocoons. The jets are long, stretching from several hundred
astronomical units to several light-years. And we can even watch these
jets evolve over time using the Hubble Space Telescope. For example, some
Herbig-Haro objects were studied over a couple of decades, and we can see these
jets moving out away from their stars. But as we look at these jets, it quickly
becomes clear that they're clumpy. This tells us that star formation is not a
smooth and continuous process, but is fitful and episodic, alternating between
periods of accretion and jet formation. Most of what we know about how stars
form come from studying low-mass stars like our Sun undergoing formation.
This is for two reasons: first, low mass stars take a lot longer to form than
high mass stars. A star roughly the mass of our Sun can take up to 10 million
years or so to form, whereas a star that is maybe ten times
the mass of our Sun can take as little as a hundred thousand years to form.
Now, even a hundred thousand years is a long time, but understand that that means that
for any given star that we see there's less chance that we would have caught a
high-mass star forming. Another problem is that high mass stars are far less
common than low mass stars. So if you happen to catch a star in the act of
forming, chances are it's going to be a low mass star. But low mass stars are
generally fainter than high mass stars, which means that we are limited to
studying stars that are relatively close by in our galaxy. Our galaxy is rich
in dust and also rich in heavy elements, or metals. So not only do we have limited
knowledge of how high mass stars form, but we also have models that are based
on stars forming in metal-rich environments and galaxies. However, some
recent work by Dr. Anna McLeod and her team is now shedding some light on the
formation of high mass stars. McLeod used the European Southern Observatory's Very
Large Telescope to examine the star forming region in the Large Magellanic
Cloud, or LMC. This region is called LHA 120-N 180B, or N180B for short.
This is a complex of ionized hydrogen that is energized by the more than 50 massive
stars that have recently formed within. These stars weigh anywhere from 10 to
15 times the mass of our Sun. Their powerful winds blow a giant bubble more
than 130 light-years in diameter. At 160,000 light years distant, it's
certainly farther away from us than most nearby star forming regions, but not so
far that we cannot resolve it with our largest telescopes. Not only that, but the
galaxy is really low in dust. That means that there's far less junk to
obscure our view of star formation. Even better, the LMC is relatively low in
metals. That makes N180B a natural laboratory for studying high mass stars
and how they may have formed in the early universe. In the southern part of
N180B is a massive star undergoing formation that is just ripe for
study. We're gonna find out what's been learned about the star so far, but first
I want to thank my Patreon supporters for their generous support: Patti
Brassard, Neil from crypto cruising, Eric from modern-day tech, John Cannon,
Gorothbalion, Erynn Wilson, Jennifer Brozeck and I want to welcome my two new patrons,
Neils Christensen and Jo A Walters/ Thank you so much for your generous
support! In the southern part of N180B lies a massive newly forming star some
12 times the mass of our Sun. It's nestled at the top of a pillar of dense
molecular hydrogen. Surrounding the protostar is its protostellar accretion
disk, but perpendicular to this disk are blobs of material - the jet from this
forming protostar. To characterize the jets, McLeod and her team analyzed
the spectra of the central star and the lobes of material that were flowing
outward along the jet. They found that the lobes in the top of the image where
Doppler shifted toward bluer wavelengths while the lobes in the bottom part of
the image where Doppler shifted toward redder wavelengths. This tells us the
orientation of the jet with the top part of the jet moving toward us and the
bottom jet moving away. Both jets are moving between 300 and 400 kilometers
per second. Or if you prefer, 671,000 to 895,000 miles per hour. Pretty fast.
The top lobe is about 11 light-years in length while the bottom is about 21
light-years long. They're also very highly collimated, less than a light year
in diameter. Given their lengths and their velocities, it seems that these
Jets have been blasting for about 33,000 years/
The star accretes about one 1/100,000 the mass of the Sun each year,
while the Jets expel about three millionths of a solar mass per year. The
rates at which this protostar is accreting and losing mass are relatively high.
However, these rates decrease as the star
ages. That tells us that this protostar is still relatively young. But perhaps
the most remarkable thing about the study is that its findings are
remarkably...unremarkable. The time involved in the formation and
launching of these Jets is about 10,000 years, and that's the same
length of time as required for jets in low mass stars. So this tells us that
although the overall duration of high mass star formation is much shorter than
for low mass stars, the length of time for jets seems to be remain fixed at
10,000 years. That is a really interesting finding; it tells us that
star formation for high mass stars is accelerated, but it is fundamentally the
same physical process as in low mass star formation. With studies like these,
we can learn a lot more about how stars formed, and indeed how we came to be in
the process. Now if you'd like to see more star formation in nearby galaxies,
check out this recent video about a new high-resolution image made by the Hubble
Space Telescope of the Triangulum galaxy. And if you would like to join me on this
journey through this amazing universe of ours, well please make sure to subscribe
and ring that notification bell so that you don't miss out on any new videos.
Until next time, stay curious my friends.