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You’d think that after all these years of studying the
other planets in the Solar System, we’d have a pretty good handle on all the basics.
But last week, a new paper in Nature Astronomy outlined
the latest findings about some of the most fundamental properties of Venus:
its tilt, the length of its day, and the size of its core.
As simple as those measurements sound,
it turns out pinpointing them has been super tricky.
Many research teams have tried to estimate the length of a day on Venus before,
but weirdly, all of their estimates were pretty different.
And no one seemed to be able to nail down exactly why.
So over the last fifteen years, scientists have been repeatedly bouncing radio waves
off Venus from the Goldstone antenna in the Mojave Desert.
These waves bounced off of Venus’s atmosphere,
and were picked up by observatories at two locations here on Earth.
The delay between the two stations allowed the researchers to make comparisons
and get an estimate of the speed at which Venus was spinning, as well as its tilt.
And from there, they could get a better sense of the size of its core.
After analyzing the data, the team concluded that Venus is tilted by, get ready,
2.6392 degrees, plus or minus eight ten-thousandths of a degree.
Ten thousandths of a degree.
That’s relative to the flat, disk-shaped route it takes around the sun.
Their measurements also showed that one day on Venus lasts a
whopping 243.0226 Earth days - around two-thirds of a year here on Earth.
And if that’s not a big enough flex,
the length of a day on Venus also changes pretty rapidly.
To make their calculations, the researchers working on this project estimated
the length of a day on Venus from each measurement they took individually.
When they compared the predicted day lengths,
they observed differences in estimates by as much as twenty whole minutes.
That might not sound like much on paper,
but imagine if your day was just randomly twenty minutes longer or shorter.
That’s like a whole episode of Brooklyn Nine-Nine!
That’s so much time!
This explains previous weirdness in research,
where estimates vary pretty widely, and left scientists a little puzzled.
It turns out that the variations in these estimates,
both within the study and in previous research, can be linked to Venus’s atmosphere.
Since Venus’s atmosphere is so dense,
it moves sort of like a liquid around the planet itself, sloshing back and forth.
In fact, it’s so dense that it exchanges some of that momentum with the ground,
pushing and pulling it around, and in the process, altering the speed of rotation.
And by measuring the planet’s inertia,
a measure of how hard it is to change its speed,
they were also able to roughly estimate the size of its core.
Turns out it’s around 3500km across, which is actually pretty close to Earth’s core!
With this data, we’re able to figure out so much more about our sister planet.
The variations in Venus’s orientation and spin can give us
insight into what the core of the planet might look like.
We can also get clues on how it formed, its volcanic history,
and how the surface of the planet might have shifted over time.
Plus, having precise estimates of Venus’s tilt and rotation also means
that future attempts at landing on Venus, or entering its atmosphere,
are less likely to end up straying off course.
Now that we better understand how Venus moves, in the future,
we’ll be able to navigate our way to designated spots more easily by predicting…
like, where they’re actually going to be when we get there.
This week we also got news from NASA’s Goddard Space Flight Centre that
Hubble is giving us a rare look at how giant planets grow.
The planet that scientists are observing, called PDS 70b, orbits PDS 70,
an orange dwarf star in a system located
three hundred and seventy light-years from Earth, in the constellation Centaurus.
PDS 70b is the youngest planet Hubble has ever imaged - just five million years old!
That’s a real spring chicken, in planetary terms.
And, thanks to Hubble’s ability to sense ultraviolet light,
we can take a look at the radiation from the super-hot gas falling from
the material surrounding PDS 70 onto the planet.
From there, we can get an estimate of how quickly it is gaining mass.
In order to grow up big and strong, PDS 70b is feeding from a whole bunch of
primordial gas-and-dust in the PDS 70 system.
The planet itself has it’s very own gas-and-dust ring,
which researchers think may flow in columns toward the planet.
That kind of flow would create hotspots on the surface,
which could be at least ten times hotter than the rest of the planet
and have really intense UV glow.
Over its 5 million year lifespan, it’s managed to accumulate
about five times the mass of Jupiter.
But right now, the researchers estimate that the rate
at which PDS 70b gains mass has slowed dramatically.
In the next million years, it’ll probably only accumulate
about one hundredth of Jupiter’s mass,
suggesting it might be almost at the end of the formation process.
That said, since these measurements essentially came from
just one snapshot of the planet’s life cycle,
it’s also possible that the rate of mass accumulation is variable
and might speed up again later.
We need more data to know for sure.
Still, observations like this can give us a better understanding of how
our own loveable gas giants formed around four point six billion years ago.
Jupiter might have gobbled up gas and dust in a similar way,
and it’s possible that its moons are evidence of that process,
formed out of the leftovers.
So while we may never visit PDS 70b in person,
observing its formation is unlocking secrets much closer to home.
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