Oldies & goodies


The oldest planets ever discovered in our Milky Way have been around 11.2 billion years! Kepler 444 has identified five Venus-sized rocky bodies revolving around a star (smaller than our sun) around 117 light years away. Water on Vesta? Asteroid expected to be without water shows evidence of soil debris flow that is characteristic of water influence. Clap On, Clap Off! Quasar shuts down as astronomers watch. Shift seen in spectrum over 10 years – amazingly show.

February 2, 2015


[Dave Heller] Our planet has been orbiting our sun for some four and a half billion years, making it merely middle-aged compared to its brethren spread across the Milky Way galaxy. Let’s count the years with Derrick Pitts, chief astronomer at the Franklin Institute. Derrick, these are some senior citizens that qualify for cheap movie and Septa fare tickets.

[Derrick Pitts] And boy, are we talking about ancient. In this case we’re talking about a group of planets — five of them — that have been discovered orbiting around a star called Kepler4444. And these planets look as if they are the oldest planets that have every been identified in the Milky Way galaxy.

Just how old are they?

Well it’s looking like they’re around 11 billion years old. Their major difficulty though is that they orbit really close to their star. Although the star is not as large as our star is — it’s only 75% the size of our star — the problem is that these objects orbit way too close. They seem as if they are rocky planets; they are similar to Venus, let’s say, but because they’re so close, we know they’re very, very hot. So we aren’t expecting these to be places we might find any sort of life. But the really cool thing about this is that the Kepler space probe is the probe that keeps on giving. It finished its primary observations about a year or so ago, and as scientists dig through the data, they keep finding more and more remarkable information. So out of that data comes this information about these planets that seem to be so old.

Does a planet’s proximity to its star have anything to do with its lifespan?

Well, that’s a really great question because it depends on a lot of different factors that are going on in the solar system. What are the dynamics, what’s the star like, what are the orbital periods like, what other objects are in the solar system, what’s the age of the solar system itself? If we look at our solar system — very early in the history of our solar system — there’s lots of turbulent dynamics going on that jockeyed planets around in various positions and we finally end up where we are. But if the star is very, very old and the system is stable, perhaps the planets are stable also in their orbits and will remain there for quite some time, even though they are very close to the star.

Water, water everywhere on many planets, but on asteroids as well?

What a surprise this is. Goodness gracious, who would imagine that an asteroid — a small chunk of material that is classified by astronomers as a proto planet, if you will, leftover from the early history of the solar system — who would have imagined that one of these so far away from the sun and so unlike Earth might actually have liquid water? Well, this is a discovery that’s been made; the second largest asteroid of our solar system known as Vesta, observations have been made by the Dawn orbiting spacecraft have discovered what looks like of soil slump on a crater wall. Now the mechanism that’s typically able to allow this soil to slump this way is that water as a liquid allows the friction of the particles of dust and dirt to decrease enough that gravity will pull that soil down a slope.

  • Vesta – Credit: NASA

But what is the mechanism that allows water to exist as a liquid on an asteroid?

Earliest thinking is that water is somehow frozen beneath the surface of Vesta, and with impact of meteorites onto the surface, the shock heats the water just enough to allow it to make its way to the surface and allow for this slumping to occur. What the truth is about this is yet to be found out, but it’s a pretty strong theory that will have to withstand some more testing in order to determine if this is something that happens commonly. So with more information about Vesta, and now that the Dawn spacecraft is orbiting the largest asteroid Ceres, maybe we’ll see more evidence of this and we may be able to gather data points to help us to understand if water in these locations actually is part of the mechanism that helps this activity to happen on the surface.

Derrick, let’s pause briefly for this commercial endorsement. I understand there’s a new application for those clap-on, clap-off devices.

[Laughs] Sure, if only in astronomy this actually were the case! But what we’re applying this to is the action that we see happening at Quasar. Now I’m not talking about the television from the 1950’s, I’m actually talking about a chemical object that is actually known as a galactic nucleus. Supermassive galaxies way out at the most distant reaches of the universe have shown us that our cores are incredibly active. And these active galactic nuclei have revealed themselves, actually, to be gigantic — gigantic! — black holes at the cores of these galaxies. And they create a tremendous amount of energy that can be read over these incredible distances over these long periods of time. And that energy release comes from material crashing down onto the accretion disc of these supermassive black holes. So as we look around the universe, we’ve been able to assess great numbers of these active galactic nuclei. But they’re all in some stage of activity. And we’ve never seen a situation in which we actually have been able to observe one shutting off that energy generation. So astronomers over a ten year period have been observing one particular active galactic nucleus have been able to see exactly that process take place. Where in one observation, they see plenty of energy radiating from this object, and then at the next observation, very little radiation or a greatly reduced amount of radiation. Now of course the problem of continuing to watch to see what happens is not as if we’re watching sea monkeys in a glass and it takes place in just a few minutes. This is a process that takes thousands — hundreds of thousands — maybe even millions of years to occur. We either have to observe this particular object over many, many centuries going forward to the future, or we can simply look for more examples throughout the rest of the universe where we might be able to see little snapshots of the development of the life history of these objects that we arrange together in a string of photographs or observations that show us this stage of life at each point of life.

Like making one of those flip books.

Exactly, like making a flip book of the life cycle of an active galactic nucleus.

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