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[ intro ]
Space is enormous.
And that means even light takes a really long time to get from one galaxy to another.
So, when we see the light from galaxies that are really far away, we’re actually seeing
what they used to look like.
The more distant the galaxy, the further back in time we can travel.
And this week in Nature Astronomy, a team announced that they’d found more evidence
for the most distant galaxy to date —
one that’s so far, we’re seeing it as it looked when the universe
was only about 420 million years old.
The Hubble Space Telescope identified this galaxy in 2014.
And it’s dubbed GN-z11.
Back then, the Hubble found this thing by pushing its instruments to their limits.
So in this new paper, astronomers checked those results
by making follow-up observations with another telescope —
the Keck I telescope in Hawai’i.
Now, to figure out how far a galaxy is, you need to know more than just how dim it looks.
You also need to figure out how much its light has been stretched out.
Since the universe is expanding, galaxies like GN-z11 are flying away from Earth.
The more distant galaxies are zooming off faster than the closer ones.
And as they all go, their light gets redshifted.
In other words, every wavelength gets stretched out, and becomes a little longer and redder.
So, to figure out how far a galaxy is,
you have to observe what color it looks from a distance, figure out what color it really
is up close,
and then use those results to calculate how much it’s been redshifted.
When the researchers did that with GN-z11,
they concluded that this place has the largest redshift we’ve ever calculated for a galaxy
—
a value of 10.957.
That’s really close to what Hubble found!
And this makes it the most distant galaxy known to date.
That said, most of us don’t talk about distance in terms of redshift.
We use light-years or, when we’re talking about much, much closer things, kilometers.
But converting between the two isn’t straightforward.
For one, to translate redshift into a physical distance,
astronomers have to make a few assumptions, including how fast galaxies are flying away
from one another.
And they’re not actually sure about that.
If you use the standard parameters accepted by most astronomers, this redshift corresponds
to a distance of about 13.4 billion light-years.
But also… that’s how far away this galaxy was when it emitted the light we’re just
now seeing.
Since the universe has continued to expand since then,
this place is really a lot farther away —
anywhere from 32 to more than 380 billion light-years, depending on how you define distance.
Which is a whole can of space worms.
Still, what’s more important here is actually the age of the light.
We’re seeing what this galaxy was like when the universe
was only about 420 million years old, or about 3% its current age.
That’s back when some of the first galaxies were still forming.
So more measurements of places like this,
with more sophisticated telescopes, have the potential to teach us a lot.
Like, it’s still a debate if the first galaxies formed when big gas and dust clouds collapsed,
or if they formed from smaller blobs of matter coming together.
So as we learn more, studies like this could finally allow us to confirm what happened.
Next, a little closer to home, the Hubble has also tracked an exoplanet that may help
us figure out how many planets our solar system has.
In 2016, two astronomers proposed the existence of a ninth planet in our solar system.
It’s a hypothetical world in-between the mass of Earth and Neptune,
and it’s so far, it would take over 10,000 years to orbit the Sun.
To support this idea, the astronomers pointed to the Kuiper Belt,
the debris ring that Pluto calls home.
Out there, a bunch of small, rocky bodies have orbits that are all askew.
And according to models, those wonky orbits could be explained by a large planet gravitationally
messing things up.
Still, this is highly hypothetical.
And this planet would have to be pretty unusual.
It would have to have a really elliptical orbit,
that’s also really tilted compared to the rest of the planets’.
But that’s where this new research comes in.
This paper was published last week in The Astronomical Journal.
In it, another team of astronomers have helped show
that a Planet Nine could be possible.
And they did it by using the Hubble to study a world some 336 light-years away.
It’s called HD 106906 b.
It’s an exoplanet about 11 times the mass of Jupiter.
And it’s super far from the two stars it likely orbits —
currently 737 times farther than the Earth orbits the Sun.
We actually found this planet in 2013, and there have been a few papers on it since then.
Like, in a 2015 paper, Hubble picked up this system’s equivalent of a Kuiper Belt,
which appears much larger on one side than another.
The researchers proposed that this might be caused by the exoplanet’s gravity,
but it was hard to say that for sure without knowing the planet’s orbit.
Now, though, we’ve figured that out!
In this new paper, the team combined over 14 years of observations of the planet’s
stars.
And they concluded that this exoplanet also has an extremely distant,
highly elliptical orbit that doesn’t align with everything else in its neighborhood.
So while this doesn’t help us find Planet Nine, it does confirm such a planet could
exist.
As for how this exoplanet got into its weird orbit...
the team thinks it may have formed closer to its stars, but eventually, gravitational
interactions threw it almost entirely out of the system.
And then, another passing star stabilized its orbit into what we see today.
So, maybe Planet Nine could have experienced a similar journey.
We’ll need more research to say for sure, though.
Because sometimes, even really cool discoveries like this just give you even more questions
to explore.
We’re big fans of storytelling around here, and if you are, too,
you might be interested in an audiobook I’ve been listening to on Audible.
Scishow host Rose Bear Don’t Walk recently recommended Braiding Sweetgrass to me and
it’s written and narrated by Robin Wall Kimmerer, an indigenous scientist.
I’m really enjoying it because Robin Wall Kimmerer is an incredible writer who weaves
together her own personal stories with her academic science background
With indigenous narratives that help us understand the world more completely
And its just a really great listen and I highly recommend it
Even though I’m not finished yet but it’s really really good s
So it’s braiding sweetgrass if you want to check that out
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If you’re interested,
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Thanks
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