For the first time ever, astronomers have captured a direct image of a newly forming
planet orbiting around a newly forming star.
It’s a stunning photograph, not only for the science and what was observed, but what
it means the future of exoplanetary astronomy.
For the longest time, astronomers puzzled over how the planets in the Solar System formed.
Did they form in place with the Sun, or were they somehow captured later on?
There was no easy way to know because we’re here, 4.5 billion years after the event took
place.
The leading theory was the idea that the entire Solar System formed at once from a giant cloud
of hydrogen and helium left over from the Big Bang, as well as heavier elements seeded
by nearby supernova explosions.
Some event caused this cloud to collapse in on itself.
As it collapsed, it got hotter and denser.
At the very core of this collapsing cloud was the region that would eventually become
our Sun.
The combined motion of all the molecules in the cloud set it rotating, and as it sped
up, it flattened out like a spinning pizza.
This was the Solar System’s protoplanetary disk.
Material in this disk clumped together into larger and larger grains, eventually forming
asteroids, and even planets.
It was a pretty hectic and dangerous time as objects smashed together merging into larger
objects.
Then, as the newly forming Sun turned on, it blasted out powerful radiation that cleared
out the intervening gas and dust, revealing the new solar system to the Universe.
Or at least, that’s what astronomers thought happened.
But the problem is that finding evidence for this has been difficult.
We can see these protoplanetary nebula across the Milky Way, but they’re shrouded in gas
and and dust the obscures visible light.
As astronomers demonstrated last week, though, new technologies and techniques are pulling
back that cloak, and have showed us, for the first time, that planetary formation matches
the theories.
Astronomers used the European Southern Observatory’s Very Large Telescope to observe the newly
forming planetary system PDS 70.
This is a 10-million-year-old dwarf star, with just a little less mass than the Sun.
It’s located about 370 light-years from Earth with a very wide protoplanetary disk
that made it an ideal candidate for further study.
In 2012, astronomers used the near-infrared instruments with the VLT to peer through the
gas and dust that obscures visible light observations.
They found a significant gap in the disk of PDS 70, but the problem was that they couldn’t
tell if features in the disk were actually planets.
This made it the perfect candidate to study with a brand new instrument attached to the
Very Large Telescope called SPHERE, which saw its first light in 2014.
SPHERE was used in 2015 to show an aging star giving birth to a planetary nebula - what
our Sun will probably do billions of years from now.
It revealed incredibly detailed structures within a dusty disk around a nearby star,
but it didn’t actually resolve planets.
And it mapped out the protoplanetary disks around other stars, showing how their planets
carve out gaps in the disk.
Again, no planets.
SPHERE stands for Spectro-Polarimetric High-contrast Exoplanet REsearch instrument, another backronym.
And how it works is pretty clever.
The instrument is equipped with a coronograph, a region that blocks the light from the central
star, revealing the fainter protoplanetary disk and planet around it.
When stars give off light, it’s unpolarized, which means that there’s no orientation
to the photons going out into space.
When those photons strike the atmosphere of a planet, some of them are partially polarized,
similar to how polarized sunglasses will let some sunlight through.
Or 3D glasses will let different views of the same movie into your separate eyeballs.
SPHERE is designed to pick up this polarized light.
Astronomers then took many exposures over many hours on two separate observing days.
By aligning all the images together, they were able to remove anything that wasn’t
moving.
What remained was the faint signal of a newly forming planet: PDS 70b.
The planet, has a few times the mass of Jupiter, and orbits its star at a distance of about
3 billion kilometers.
That’s about the same distance as the Sun to Uranus, and it takes about 120 years to
complete an orbit around the Sun.
Even at that distance, it’s hot, measuring about 1000-degrees Celsius, or 1,200 Kelvin.
Amazingly, astronomers were even able to detect that the planet has a cloudy atmosphere.
The planet is moving within a large gap within the protoplanetary disk, which means that
it’s probably still accumulating material, and will until the star’s stellar winds
finally kick in and starve it of any more.
This is a stunning accomplishment.
It shows how a ground based observatory like the Very Large Telescope is able to directly
observe extrasolar planets.
It harnesses the most powerful telescopes in the world, using the right techniques and
technology to do something that was thought only possible for a space telescope.
Just imagine what will be possible in the next few years when the next generation of
supertelescopes are completed.
The 24.5-Meter Giant Magellan Telescope, 30-Meter Telescope, and the 40-Meter Extremely Large
Telescope.
This is just the beginning.
I can’t wait to see what happens next.
What do you think?
Let me know your thoughts in the comments.
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