Bad Astronomy
The entire universe in blog form

June 22 2015 1:07 PM

A Ceres of Weird Events

Ceres keeps getting weirder.

Those white spots on the surface we’ve been seeing for months are still mystifying, and we can now add another bizarro surface feature to the list: A huge 5 kilometer tall mountain sitting in the middle of an otherwise relatively flat part of the asteroid.

Um. Why is that there?

On Earth, mountains can form for several reasons. Continents crash together, creating wrinkles in the surface. That’s what the Himalayas are. Of course, Ceres doesn’t have plate tectonics! That wouldn’t form a solitary mountain anyway.

Volcanoes? Well, we do see that happening on Earth. But we don't see any other features like this at all nearby, making it unlikely to be from a weak spot in the crust. Devil’s Tower in Wyoming is similar to this feature, though; that tower may have been created by upwelling magma seeping into prehistoric sedimentary layers. But clearly that’s not going to happen on an asteroid! Sedimentary rocks would be, I expect, rather difficult to produce. 

Mountains on airless bodies like asteroids (or our Moon) can be made in several ways as well. Giant impacts have mountain ranges around their rim, created by rocks lifted up at the edge of the crater. But this mountain on Ceres is alone.

Smaller craters can get central peaks, where the rock rebounds upward after the initial impact (similar to the drop that splashes up in the center of a glass when you pour milk). But there’s no obvious crater around this mountain. Maybe other forces filled it in, or subsequent impacts eroded it away. There's evidence of landslides on the surface as well, which could eventually erase the features of a crater. This seems most likely to me. We've seen other craters on Ceres with central peaks, but I don't think any yet this size. Given all the evidence, though, this is the way I'd lean.

But I’m simply guessing. We’re just now seeing this strange feature, and it’ll be a while, I suspect, before planetary scientists can get enough data to understand it better. Note that Dawn, the spacecraft now orbiting Ceres that took this picture, is still in a relatively high surveying orbit, 4,400 km above the surface. It’ll be dropping down to get much higher resolution images in the coming months.

Hopefully then we’ll get some definitive answers to these mysteries. Ceres is odd. We know there’s ice under the surface, and there’s evidence it also has geysers, eruptions of water, from its surface. That might explain the white spots, too, but there’s still a long way to go to figure all this out.

white spots on Ceres
Yes, the white spots are still there too. This image was taken on June 9, 2015.

Photo by NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Ceres is the largest asteroid in the asteroid belt (some call it a dwarf planet; I find the term not terribly useful). It’s unique in that sense, and big enough to have geological processes on it and in it we haven’t fully grasped yet. It’s not Earth, for sure, but it’s far more than a simple monolithic rock in space.

It’s a world. And with a surface area of nearly 3 million square kilometers, there’s a lot of it to explore.

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June 22 2015 7:15 AM

Are Volcanoes Still Erupting on Venus?

There are a handful of known currently tectonically active objects in the solar system: Earth, of course, plus Saturn’s moon Enceladus, Neptune’s moon Triton, Jupiter’s moon Io (the actual most active body known) and (most likely) Jupiter’s moon Europa.

And now we may be able to add Venus to that list. New evidence strongly suggests there are currently active volcanic vents on the surface of Earth’s sister planet.

I’m actually pretty chuffed about this. We’ve had tantalizing evidence for years that something is bubbling and brewing just beneath Venus’ surface. The top of the mountain Idunn Mons is clearly hotter than surrounding terrain, for example. Lava flows have been seen to be warm as well, and they are certainly less than 2.5 million years old, and possibly far less. Sulfur dioxide, a known volcanic gas, has been seen to spike in abundance then fade with time, which looks very much like a volcano outgassing (though it could simply be due to shifting winds).

But new results from an old mission provide what may be the most important evidence yet that Venus is still puffing away: The ESA Venus Express probe, which completed its eight-year mission last year, found several hot spots on the surface of the planet, and they were all located in rift zones; radial cracks around a volcano where, on Earth at least, magma is pushing up on the surface and flowing out.

Better yet, these hot spots flashed into existence and then faded away over the course of a few days. This is exactly the sort of behavior you’d expect from ongoing volcanism.

Venus volcano map
NASA’s Magellan probe data was used to generate this perspective view of the volcano Ozza Mons (red, in the center) with the rift zones (purple) radiating away. Venus Express saw several hot spots in these valleys.

Photo by Ivanov/Head/Dickson/Brown University

Observing the surface of Venus is difficult because of its thick, opaque atmosphere (a product of a runaway greenhouse effect). The observations were at the limit of what the camera could do, but Venus was accommodating by providing really big temperature spikes: One may have reach more than 800° Celsius, 350° higher than the surface average.

The camera’s field of view is large, so the resolution is low, but it’s possible these hot spots may be as small as a square kilometer. All in all, these really sound like lava eruptions to me. I’m no expert, of course, but then the people who did the research are.

Studying Venus is important. In many ways it’s very much like Earth. It’s roughly the same size and mass, which means the same density, and that implies we have similar compositions. So why is Venus so blisteringly different? Compared with us, we can ask, “What went wrong?” Why is its crust so thick? Why did the greenhouse effect run away there, and not here? Why does Venus appear to have a surface that’s everywhere the same age, as if a globally catastrophic event repaved the entire planet?

Looking to other planets to understand our own is a critical part of planetary science, and given the current state of Earth’s atmosphere, it’s something we must do. Together with studying our own planet (something the current congressional majority is dead set against, for some odd reason) these are matters that are critical to our own survival.

That’s why these new results of an extant volcanic Venus are so exciting. That, plus the more purely scientific reason that it’s just plain cool. Venus gets closer to Earth than any other planet in the solar system, yet still hides many secrets. What more is there to learn about it?

I’ll leave you with this, my episode of Crash Course Astronomy about Venus. I wonder how many of the questions raised in it will be answered in the coming years?

June 21 2015 10:15 AM

To Pluto

Why is it so many of us are excited about the New Horizons mission to Pluto?

This. This is why.

That video was created by Erik Wernquist, the brilliant mind behind Wanderers, what I consider one of the best paeans to exploration ever made.

And like Wanderers, all the places in the New Horizons video are real. We see Venus; Mars (flying over Valles Marineris; a rift valley that dwarfs the Grand Canyon); volcanoes of sulfur erupting over the moon Io as Jupiter and its Red Spot hover into view; the two-faced ice moon Iapetus, stained with organic compounds, revealing the magnificence of Saturn as we slide by; Uranus, its atmosphere a teal green from the presence of methane; Neptune and its moon Triton, with its geyserlike eruptions of nitrogen blasting into its extremely tenuous atmosphere …

… and then Pluto. As I write this, just over three weeks before the New Horizon probe pierces the tiny world’s region of space, we still only have fuzzy pictures of Pluto, a mere dozen or so pixels across. Astronomers have many ideas on what we’ll see when the spacecraft sends back its images over the staggering vastness of 5 billion kilometers of solar system, but the bottom line is we don’t know exactly what we’ll find.

If we did, it wouldn’t be exploration.

You can follow along with this journey using the Pluto Safari app, and of course by keeping tabs on the New Horizons website.

This is more than just terra incognita. It’s spatium incognita. Whether you think Pluto is a planet or just the biggest of the Kuiper Belt Objects, it’s a marvelous step in our exploration of the solar system.

And we’ll be seeing it for the very first time in the history of all humanity, very, very soon.

June 20 2015 7:15 AM

Vulcan Is an Angry God. A Very, Very Angry God.

On April 22, 2015, the Chilean volcano Calbuco erupted, providing the most dramatic and awe-inspiring photographs I’ve ever seen of such an event.

On that day, photographer Martin Heck was right on the scene, by happenstance taking time-lapse footage on the neighboring Osorno volcano. When Calbuco went off, he hurriedly set up and shot video that is, no exaggeration, some of the best I have ever seen of any volcanic eruption ever. 

June 19 2015 7:00 AM

Crash Course Astronomy: Comets

When it comes to exciting solar system exploration right now, comets are right there at the top. With Rosetta orbiting the comet 67P for nearly a year now, and hearing once again from the nearly-lost Philae lander, it’s a great time to be an astronomer studying these icy worldlets.

I’ve loved comets for a long time; I’ve seen ones bright enough to spot naked eye, too faint to be seen without a telescope, and one that was near the Sun and so bright it was visible in broad daylight! They used to be considered omens, but when you cast aside superstition what you find are endlessly amazing and fascinating examples of nature at its best.

I could go on and on, but instead … I’ll let me go on and on, in this week’s episode of Crash Course Astronomy.

Mea culpa: I mispronounced Bayeux. Dangit. It's BYE-you, not BAY-you. I blame Scott Baio.*

If you want to know more about the Rosetta mission—and you do—I’ve written about it a lot. I’ve also written quite a few articles about comets both generally and in specifics. It’s somewhat amazing how little we knew about them until recently, and how much staggering information we’ve been able to find about them in just the past few years.

And after all that, if you think you know everything about comets, then perhaps you’d like to take a look at this article, “10 Thing You Don’t Know About Comets.” How many did you know before watching Crash Course?

*Correction, June 19, 2015: This post originally misspelled actor Scott Baio’s last name.

June 18 2015 11:30 AM

The Jets at Night Are Big and Bright (Clap Clap Clap Clap) Deep in the Heart of Comets

While all eyes are on Philae, the little comet lander that could, the Rosetta orbiter is still observing 67P/Churyumov-Gerasimenko, and still making discoveries about how a comet behaves. Its newest is actually very cool … or actually warm: Jets of material are now being seen blowing out from the comet even after the direct sunlight is gone. This means the comet is getting more active.

I wrote all about it for my twice-monthly column at Sen. It’s subscription only, but you’ll find lots of great stuff there, including tons of news and images you can see for free.

June 18 2015 7:00 AM

For the First Time, a Mars-Sized Exoplanet Reveals All

The more I think about this, the more it rates a “Holy Haleakala!”: For the first time, astronomers have found not only the size but also the mass of an exoplanet smaller than Earth.

So: Holy Haleakala!

The planet orbits the star Kepler-138 (also called 2MASS J19213157+4317347, if you’re particular about such things). It’s a red dwarf star, meaning it’s less massive and cooler than the Sun. It’s about 200 light-years away.

There are three exoplanets orbiting Kepler-138, which are given the designations Kepler-138b, c, and d. All three were discovered in observations made by the Kepler observatory using the transit method; we see the planet’s orbits edge-on, so as they orbit their star they periodically block a little bit of its light. That dip is small, but measurable.

The length of time it takes for the planet to cross the star’s face tells us the size and shape of the orbit. The amount of light blocked tells us the size of the planet, since a bigger planet blocks more light. The inner planet has a diameter of about 0.52 times Earth’s, or about 6,600 kilometers—almost exactly the same size as Mars! The other two are both about 1.2 times the diameter of Earth, or about 15,000 km.

In general it’s much tougher to find the planets’ masses. But in this case we have a leg up: The planets orbit very close in to their star on very tight orbits, so the spacing between their orbits is small. When an inner planet passes an outer one, they tug on each other gravitationally, speeding up the inner one and slowing down the outer one as they approach, then they reverse as they pull apart.

This has a subtle but measurable affect on the timing of the transits. By carefully measuring the exact times of the transits of the planets, their gravitational affects on each other can be found, and from that their masses can be worked out.

The planets’ masses were found to be 0.066, 2, and 0.65 times Earth’s mass. Why is this important? Because if we know a planet’s size and mass, we can calculate the density, and that gives us a hint of what the planet’s made of!

The inner planet has a density of about 2.6 grams per cubic centimeter. That means it’s probably rocky, and doesn’t have a lot of heavy metals like iron or nickel like Earth does (our density is about 5.5 g/cc, and for comparison water has a density of 1 g/cc). So, while it’s roughly the same size as Mars, it has roughly 60 percent the mass. The second planet out has a density of 6.2 g/cc—similar to though a bit higher than Earth's—and the outer planet is 2.1 g/cc.

Mind you, all three orbit the star very closely. The inner planet is only 11 million kilometers away! Even though it’s a red dwarf star, that means the inner planet is still pretty hot. Even the outer of the three is closer to the star than Mercury is to the Sun. All of them would be pretty unpleasant places to visit (if I’ve done my math right, even the outer planet would likely be hotter than the boiling point of water).

So Earthlike they ain’t. In fact, all three seem to me to be pretty different from each other, which is interesting. In our solar system the inner three planets (Mercury, Venus, and Earth) have similar densities. In fact, Venus and Earth have similar compositions as well, though Venus is, um, somewhat different than us in detail. I’d guess our inner solar system and the Kepler-138’s formed differently somehow.

These observations are a fantastic achievement! Think about this: Just by staring at a star for a long time, and measuring its light carefully, we can figure that it has planets, how many it has (or a minimum, at least; it might have more we don’t see), what their orbits are, how big the planets are, what their masses and densities are, and even take a stab at what they’re made of.

And all this, from a distance of over 2 quadrillion kilometers! That’s amazing.

Science! I love this stuff. 

June 17 2015 7:15 AM

Supernova Ozymandias

More than 6,000 light-years from Earth, a massive star was dying.

Its core was hot chaos. The star had been fusing hydrogen into helium for millions of years before running out of fuel. Then it started fusing helium into carbon, but then ran out of this fuel in just a million years. Carbon fusion initiated, churning it into neon for a millennium, then neon into magnesium for a single year. It fused the resulting oxygen into silicon, running out in just a few months. Just the day before—a single day, after all those eons!—it began fusing silicon into iron.

And it was doomed. Iron fusion is unsustainable. In a single instant the core collapsed, unleashing a fury of energy and subatomic particles that slammed into the material above.

The star exploded.

June 16 2015 12:00 PM

The Dart of Harkness

If you don’t follow me on Twitter, then you miss out on experiencing my transcendent humor.

Oh: If you’re not a Doctor Who fan—specifically, of the David Tennant tenure—then this will make zero sense to you.

You’re welcome.

June 16 2015 7:15 AM

Watch Venus and Jupiter Kiss in the Night 

The sky is gearing up for a very cool event: On June 30 and July 1, Venus and Jupiter will pass extremely close together in the sky, less than a third of a degree apart!

That’s close. The full Moon is a half degree across, so this will be very pretty. And it plays out over several days, so you’ll have plenty of chances to see it.

The planets orbit the Sun more or less in the same plane. We’re in that plane, too, so we see the solar system from the inside, and edge-on. That means that as the planets move around the Sun we see them moving along the same line in the sky, which we call the ecliptic.

In reality the planets’ orbits are all tilted slightly with respect to one another, so they don’t follow the exact same line. This means that, from Earth, we see them pass by each other in the sky, sometimes closer than other times. Usually they miss each other by a few degrees—and remember, this is just a perspective effect. In reality the planets are hundreds of millions of kilometers apart.

Venus orbits the Sun closer than Earth does, and Jupiter well outside. Right now, Venus is “rounding the corner” of its orbit, on the near side of the Sun and starting to overtake us. Jupiter is headed for superior conjunction, when it’s on the other side of the Sun from us. All these motions combined means Venus and Jupiter are approaching each other in the sky, getting closer every night.

If you go outside just after sunset (even before the sky is totally dark) and look to the west, you won’t miss them; Venus and Jupiter are the third and fourth brightest natural objects in the sky. It’s been pretty rainy where I am, but the other night we had clear skies and I saw them about 10° apart. They’re already making a striking pair.

Venus and Jupiter
The view through a telescope around 03:30 UTC July 1 will look like this, except Venus will show a crescent, and Jupiter more detail. You can see why this is so cool!

Screengrab from Sky Safari software

They get closest together around 03:00 UTC on July 1 (which is in the evening in the U.S. on June 30). At that point they’ll be about 17 arcminutes apart (there are 60 arcminutes to a degree, so the Moon is 30 arcminutes in size). Through a telescope they’ll be amazing. They should both fit easily under low power. Jupiter’s disk will show stripes, the moons will be visible, and Venus will shine in a waning crescent phase.

This is the closest the pair have been for a while … but just wait until next year. They’ll get an incredible 4 arcminutes apart on Aug. 27! That’s during the day here in the U.S., but should be visible with binoculars or a telescope. So think of this month as a warmup.

In the meantime, get out and watch! It’s fun to go out every night and see them get closer. If the weather holds up, you can bet I’ll be outside, and looking through my own ‘scope, too.

For more info, and more events like this, check out the article on Universe Today.

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