NASA’s DART Mission: Rest in Peace

Hello, friends!

As you probably know, NASA’s DART spacecraft deliberately rammed itself into an asteroid on Monday.  This was a test.  It was only a test.  The asteroid in question (named Dimorphos) was never a threat to us.  Someday, though, another asteroid may come along… an asteroid that does threaten us… an asteroid that could end life as we know it.  The DART Mission was intended to test out ability to defend ourselves, should a large and genuinely threatening asteroid ever show up on our doorstep.

I spent Monday night watching NASA TV’s livestream of the DART Mission.  Those final images from DART’s navigational camera were amazing!  I never really thought about what it would look like to crash into the surface of an asteroid.  Now I know exactly what that would look like.

Anyway, today I thought I’d share a few things that I learned—things that I did not know before—while watching NASA’s livestream, as well as the press conference that was held after the mission was over.

The Space Force: So I knew DART launched almost a year ago, but I didn’t know it had launched from Vandenberg Space Force Base (I also didn’t know Vandenberg Air Force Base had been renamed).  I still think the whole Space Force thing is cringy, but at least the Space Force did help do something to actually defend our planet.  So that’s cool!
DART’s Solar Panels: In addition to testing our planetary defense capabilities, the DART spacecraft also tested a few new space technologies.  Most notably, DART was using a new, experimental solar panel design.  DART launched with its solar panels rolled up into cylinders, then the solar panels unrolled once the spacecraft was in space.  The new design apparently weighs a lot less than traditional solar panels, and anything we can do to lower the weight of a spacecraft helps make spaceflight less expensive.
Dimorphos’s Shape: This one really surprised me.  Apparently nobody knew what Dimorphos looked like until those last few minutes before impact.  The most high-res images we had were still not high-res enough to reveal the asteroid’s shape or any useful details about its appearance.  As a result, DART had to be programmed with some sort of machine learning algorithm to help it figure out what it was supposed to be aiming for.

While the DART Mission was a success, it’ll still be a while before we know exactly how effective it was at moving the orbit of an asteroid.  Telescopes up in space and down here on the ground will continue monitoring Dimorphos as the dust settles (both figuratively and literally).  Still, as a citizen of Planet Earth, I do feel a little bit safer living on this planet.  I mean, we still have a lot of challenges we need to overcome, but that asteroid problem?  I think we’ve got that one covered now.

So did you watch NASA’s livestream on Monday?  Did you learn anything new, either from the livestream or from other news sources covering the DART Mission?

P.S.: If you missed the livestream, click here to watch it on YouTube.  Or you can click here to watch the press conference that was held afterward.

Sciency Words: The YORP Effect

Hello, friends!  Welcome to another episode of Sciency Words, a special series here on Planet Pailly where we talk about the definitions and etymologies of scientific terms.  In today’s episode, we’re talking about:

THE YORP EFFECT

Picture a windmill.  As the wind gets stronger or weaker, the windmill spins faster or slower, right?  Okay.  Now replace the windmill with an asteroid orbiting the Sun, and replace the wind with sunlight.  Over long periods of time, sunlight can make the asteroid spin faster or slower.  Sunlight can also change an asteroid’s axis of rotation.  This is known as the YORP Effect (not to be confused with the Yarkovsky Effect).

Definition of the YORP Effect: In astrophysics, the YORP effect is what happens when reflected and/or absorbed sunlight generates “thermal torque” on an asteroid.  Reflected sunlight exerts a very small (but non-zero) amount of force on the surface of an asteroid.  Absorbed sunlight radiates away from the surface of an asteroid as heat, exerting an additional small (but non-zero) amount of force.  Due to the irregular shapes and material consistencies of asteroids, it’s hard to predict exactly what this thermal torque will do, but over long enough periods of time it can dramatically change an asteroid’s rotation rate and axis of rotation.

Etymology of the YORP Effect: The term was coined in 1999 by American geophysicist David Rubincam.  The YORP Effect, as we currently know it, combines the previous research of Ivan Yarkovsky, John O’Keefe, Vladimir Radzievskii, and Stephen Paddack.  YORP is therefore an acronym of the names Yarkovsky, O’Keefe, Radzievskii, and Paddack.

This all started with Ivan Yarkovsky and his Yarkovsky Effect, which we talked about in last week’s Sciency Words post.  The Yarkovsky Effect has to do with the way sunlight affects the orbital trajectory of an asteroid.  The Yarkovsky Effect was lost to science for a while, then it was reintroduced in 1951.  Shortly after that reintroduction, other scientists started wondering what other effects sunlight might have on an asteroid, which ultimately led to this idea of a thermal torque effect, which we now call the YORP Effect.

To be clear, the Yarkovsky Effect and the YORP Effect are two different effects—one related to an asteroid’s orbital trajectory, the other to an asteroid’s rotation rate and axis of rotation.  They’re caused by the same thing—sunlight—but they are two different effects.

In 2007, observations of an asteroid named 2000 PH5 helped confirm that the YORP Effect is real.  The asteroid had been monitored closely over the course of about four years, and astronomers found that its rotation rate was steadily increasing.  This increase could not be explained by gravitational interactions alone, nor by collisions with other asteroids or any other known effects.  Therefore, by process of elimination, only the YORP effect was left as a possible explanation.  Asteroid 2000 PH5 was subsequently renamed 54509 YORP to honor its help in confirming the YORP Effect.

And in 2013, an asteroid named P/2013 R3 literally YORP-ed itself apart.  The YORP Effect caused the asteroid to spin so fast that it started flinging chunks of itself away.  There may have been some previous collision or other catastrophic event that made P/2013 R3 more fragile; still, in the end, it was the YORP Effect that caused the final destruction of that asteroid.

So if you’re an asteroid flying around in space, be careful.  It may be fun YORP-ing and Yarkovsky-ing around the Solar System, but you don’t want to Yarkovsky yourself into hitting a planet, and you don’t want to YORP yourself into self-disintegration either.

WANT TO LEARN MORE?

P.S.: The DART Mission is scheduled to crash itself into an asteroid tonight at 7:14 p.m. East Coast time in the U.S. (also known as 23:14 GMT).  If you’re interested, NASA TV will be live streaming the collision on their YouTube Channel.  It would not surprise me if the Yarkovsky and YORP Effects are mentioned as part of NASA TV’s science commentary.

NASA’s DART Mission: Brace for Impact!!!

Hello, friends!

We are only a few days away from what is, in my opinion, the #1 most important space story of the year.  No, I’m not talking about the launch of Artemis 1.  And no, this has nothing to do with the Webb Telescope either.  I’m talking about NASA’s DART Mission.

For eons now, asteroids have been zipping and zooming past our planet.  Every once in a while, one of those asteroids will hit our planet, causing anywhere from minor to major to global mass extinction event levels of damage.  But on Monday, September 27, 2022, humanity will perform our first ever experiment to see if it’s possible to smack an incoming asteroid away.

The asteroid in question is named Dimorphos.  Dimorphos is not actually a threat to us, but if we’re going to perform an experiment like this, Dimorphos is a rather convenient target for target practice.  That’s because Dimorphos is not just an asteroid; it’s also a moon (or should I call it a moonlet?) orbiting a larger asteroid named Didymos.

When the DART spacecraft crashes into Dimorphos, the force of the impact will change Dimorphos’s orbit around Didymos.  It should be fairly easy for astronomers to measure this change, and thus it should be fairly easy to judge how effective DART was—and just how effective DART would have been against an asteroid that was actually threatening us.

Oh, and just in case anyone’s concerned that DART might accidentally knock Dimorphos out of its original orbit entirely and send it hurtling our way, thus ironically causing the very disaster this mission was meant to help prevent—don’t worry.  Didymos’s gravitational hold on Dimorphos is strong.  No matter what happens on this mission, Didymos is not going to let her little moonlet go (another reason why Dimorphos was selected as the target for this experiment).

So on Monday, September 27, 2022, there will be a head-on collision between an asteroid/moonlet and a NASA spacecraft.

An Italian-built spacecraft named LICIACube will be positioned nearby to observe the experiment.  A multitude of Earth-based telescopes will also be watching.  The European Space Agency also plans to send a follow-up mission (named Hera) in 2026, to check up on Dimorphos after its post-impact orbit has had some time to settle down.

Life on Earth has never been able to defend itself from incoming asteroids before.  Life on Earth has never had the ability to even try, until now [citation needed].  Obviously asteroids are not the only threat to life on our planet.  Obviously this is not the only challenge we need to overcome.  But the DART Mission is a huge first step.  A true giant leap.  No, DART probably won’t get the same kind of love and attention as Webb or Artemis 1, but still I’d say this is the #1 most important space story of the year.  This may be one of the most important science experiments in all of Earth history.

WANT TO LEARN MORE?

P.S.: I said life on Earth has never before had the ability to defend itself from incoming asteroids.  Technically speaking, we cannot be 100% sure that’s true.  Click here to read my post on the Silurian Hypothesis.

Sciency Words: The Yarkovsky Effect

Hello, friends!  Welcome to another episode of Sciency Words, a special series here on Planet Pailly where we discuss the definitions and etymologies of scientific terms, in order to expand our scientific vocabularies together!  Today’s Sciency Word is:

THE YARKOVSKY EFFECT

Imagine an asteroid orbiting the Sun.  Every once in a while, this asteroid passes alarmingly close to Earth.  If you’re familiar with Kepler’s laws of planetary motion, you may expect that scientists could predict, with pinpoint accuracy, where that asteroid will be years, decades, or even centuries into the future.  However, there are certain physical forces acting on asteroids that are not accounted for in Kepler’s laws.  One of those physical forces is known as the Yarkovsky Effect.

Definition of the Yarkovsky Effect: In astrophysics, the Yarkovsky Effect is a thermal force that affects the orbit of asteroids.  Like most planets, asteroids rotate; therefore, you could say that asteroids have day-night cycles.  During daytime, the surface of an asteroid absorbs heat from the Sun.  At night, the asteroid’s surface cools off by radiating heat out into space.  This radiating heat generates a very, very, very small amount of thrust.  Over time, that small amount of thrust can dramatically change the orbital trajectory of an asteroid.

Etymology of the Yarkovsky Effect: The Yarkovsky Effect is named in honor of Polish/Russian civil engineer Ivan Yarkovsky, who first described a similar “heat engine” effect in 1888, and who later published a pamphlet on the topic in 1901.  Yarkovsky’s work would have been lost to history, except that Estonian physicist Ernst Öpik recalled reading Yarkovsky’s 1901 pamphlet and reintroduced the idea to the physics community in 1951.

Yarkovsky was more of a science hobbyist than a professional scientist.  He had a day job working on railroads.  In his free time, he read a lot about science, and he did a lot of thinking.  He performed his own experiments, occasionally, and he came up with some interesting ideas that sound like utter nonsense today, but which must have made sense in the context of late 19th Century science.  Even the Yarkovsky Effect, as Yarkovsky originally described it, was tied up with a now defunct scientific theory called ether theory.

Still, even if his starting assumptions were off track, Yarkovsky stumbled upon the truth at least one time.  Asteroids do have “heat engines,” as Yarkovsky described it.  Asteroids do have these naturally occurring thermal propulsion systems, powered by sunlight, which can mess with their orbits.  The challenge for astrophysicists today is that the Yarkovsky Effect is kind of random (or if it isn’t random, in the truest sense of the word, then it may as well be).

Asteroids are irregularly shaped.  Sometimes, they rotate on more than one axis (I once read a paper that called this multiple axis rotation “chaotic tumbling”).  And in terms of mineral composition, asteroids are made of all sorts of crazy stuff.  Different minerals can absorb and radiate heat in different ways.  So the Yarkovsky Effect pushes asteroids around, but because of all the variables I just mentioned, it’s hard to say which direction the Yarkovsky Effect will push at any given time.  It’s also hard to say how hard of a push the Yarkovsky Effect might give.

Which is why missions to study asteroids—missions like the recent ORISIR-REx Mission or the upcoming DART Mission—are so important.  We may never understand asteroids perfectly, but we do need to understand them better.  There are so many asteroids that fly alarmingly close to Earth.  It would be nice if astrophysicists could predict, with pinpoint accuracy or something near to it, where those asteroids will be years, decades or centuries into the future.

WANT TO LEARN MORE?

I used the following sources to write this blog post.  The one at the bottom is kind of a long read, but it tells the fascinating story of Ivan Yarkovsky, a man who was nearly forgotten by history.  For those of you who are interested in the history of science, it is well worth a read.

Touring Proxima Centauri’s Asteroid Belts

Hello, friends!

As you know, sometimes things don’t go according to plan.  For today’s post, I was planning to draw a really pretty picture of a really planet—a planet that astronomers may (or may not) have found in the Proxima Centauri system.  But as I did my research about this possible planet, I realized I needed to draw something else for you first.

As reported in this 2017 paper, temperature readings indicate that Proxima Centauri may have at least one and as many as three asteroid belts.  Based on what I’ve read, it sounds like the presence of these belts has not been definitively proven yet.  But no one seems to be able to definitively disprove them either.

So here is a map of everything we currently know or suspect exists in the Proxima Centauri system.

As you can see, the planet Proxima b is in an extremely tight orbit around its star.  But since Proxima Centauri is much smaller and cooler than our Sun, Proxima b is technically in the star’s habitable zone.  Click here for my post on whether or not Proxima b could actually support life.

Beyond the orbit of Proxima b, we find our first possible asteroid belt.  In that 2017 paper I cited above, this innermost belt is described as the warm dust belt.  It appears to be located approximately 0.4 AU away from its star (roughly equivalent to the orbit of Mercury in our Solar System).

A little farther out, we find a second possible asteroid belt, which the authors of that 2017 paper describe as the cold dust belt.  Remember: we suspect these dust belts exist because of temperature measurements, hence the names.  The cold dust belt appears to be spread out between 1 AU and 4 AU (roughly equivalent to the space between the orbits of Earth and Jupiter in our Solar System).

And then farther out still, there appears to be a third belt, referred to as the outer dust belt (in my opinion, it should have been named the colder dust belt).  The outer dust belt appears to be located approximately 30 AU away from its star (roughly equivalent to the orbit of Neptune).

I want to emphasize again: as far as I can tell from my own research, no one has definitively proven or disproven these dust belts exist.  All we have are some temperature measurements that suggest something might possibly be there.

But if all those dust belts do exist, that tells us there should be planets orbiting in the gaps between the belts.  It would take a planet’s gravity to keep those gaps empty.  And now that you know that, I think we’re ready to take a closer look at Proxima c.

Except tomorrow is Insecure Writer’s Support Group day, so our trip to Proxima c will have to wait.  But I promise the wait will be worth it.  Science predicts that if Proxima c really exists, it must be the most gorgeous planet you’ve ever seen!

Next time on Planet Pailly, the unexpected benefits of having your manuscript edited.

Sciency Words: The Yarkovsky Effect

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about those weird and wonderful words scientists use.  Today on Sciency Words, we’re talking about:

THE YARKOVSKY EFFECT

Have you ever tried to count all the stars in the night sky?  Well, that might be an easier job than finding and tracking all the asteroids that keep whizzing by our planet.  Part of the problem is due to something called the Yarkovsky Effect.

Ivan Yarkovsky was a Polish engineer working in Russia.  He was also a huge science enthusiast.  If Yarkovsky were alive today, I imagine he’d be writing a blog about all the cool sciency research he was doing in his free time.

But it was the late 19th/early 20th Century.  Blogging wasn’t an option, so instead Yarkovsky wrote pamphlets about science, which he circulated among his science enthusiast friends. And almost fifty years after Yarkovsky’s death, an Estonian astronomer by the name of Ernst Öpik would remember reading one of those pamphlets.

Imagine an asteroid orbiting the Sun.  Sunlight causes this asteroid’s surface to get hot.  Then, as the asteroid rotates, that heat energy radiates off into space.  Would this radiating heat produce any thrust?  Would there be enough thrust to push an asteroid off its orbital trajectory?

Öpik thought so, and in 1951 he wrote this paper introducing the idea to the broader scientific community.  Today’s Sciency Words post would probably have been about the “Öpik Effect,” except Ernst Öpik was kind enough to give credit to the obscure blogger pamphlet writer who originally came up with the concept.  Thus we have the Yarkovsky Effect.

And in 2003, radar observations of the asteroid 6489 Golevka confirmed that the Yarkovsky Effect is real!  The asteroid had wandered 15 km away from its original course!

Around the same time, a copy of Ivan Yarkovsky’s original pamphlet was found in Poland.  As described in this article, it seems Yarkovsky was working on the basis of some faulty premises and a few rather unscientific assumptions.  He more or less stumbled upon the right idea by accident (but let’s not dwell on that part of the story).

Next time on Planet Pailly, no one’s going to name a scientific theory after me, but maybe there’s another sciency honor I can aspire to.

Sciency Words: The Torino Scale

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:

THE TORINO SCALE

Are you worried about an asteroid or comet smashing into Earth and annihilating human civilization?  Well, you should be worried about that a little bit.  But only a little bit.  Let me tell you about the Torino Scale, and while that won’t put all your fears to rest, it may help put things in perspective.

In the late 1990’s, M.I.T. Professor Richard Binzel came up with a system which he initially called the Near Earth Object Hazard Index.  In 1999, Binzel presented his system to a conference on Near Earth Objects (N.E.O.s) in Torino, Italy.

People at that conference loved Binzel’s idea and voted that the system should be adopted by the scientific community at large. They also voted to rename Binzel’s system the Torino Scale.

The Torino Scale asks two questions about any given N.E.O.: how likely is it to hit us, and how much destructive energy would be released if it did?  Taking those two factors into consideration, the Torino Scale then produces a score between zero and ten.  Zero means we have nothing to worry about.  Ten means “WE’RE ALL GONNA DIE!!!  AAAHHHHHH!!!” as the experts would say.

According to Wikipedia, the comet that caused the Tunguska Event would have probably scored an eight, and the asteroid that caused the K-T Event (the event widely believed to have killed off the dinosaurs) would have scored a ten.  Wikipedia also tells me that the 2013 Chelyabinsk meteor would have scored a zero, because while that particular N.E.O. was definitely on a collision course with Earth, it’s destructive energy was relatively low (I wonder if the residents of Chelyabinsk, Russia, agree with that assessment).

As of this writing, there are no known N.E.O.s that score higher than zero on the Torino Scale, as least not according to this website from NASA’s Jet Propulsion Laboratory.  It is possible for an N.E.O.’s threat level to change as we learn more about it.  As explained in this article from NASA:

The change will result from improved measurements of the object’s orbit showing, most likely in all cases, that the object will indeed miss the Earth. Thus, the most likely outcome for a newly discovered object is that it will ultimately be re-assigned to category zero.

Sooner or later, another eight, nine, or ten on the Torino Scale will come along.  Fives, sixes, and sevens could also be bad news for us.  But for now, at least within the next one hundred years, it sounds like we probably don’t have too much to worry about.

Probably.

Didymos, Didymoon, and Didy-me

I’m a huge space enthusiast and science enthusiast, but I am not an actual scientist.  I’m an outsider looking in, drooling a little as I watch all those real scientists doing all that real science.  But even as an outsider, I still sometimes get the chance to contribute in my own small way to the cause of science and space exploration.

Coming up in June of 2018, the Didymos Observer Workshop will be held in Prague, Czeck Republic.  For those of you who don’t recognize the name, Didymos is a large asteroid with an orbit that sometimes brings it alarmingly close to Earth.  It’s also one of those asteroids that has its own tiny moon, a moon which is informally known as “Didymoon.”

The Didymos Observer Workshop will be discussing the upcoming AIDA mission, a joint venture between NASA and ESA.  According to the workshop’s website, “AIDA will be the first space experiment to demonstrate asteroid impact hazard mitigation by using a kinetic impactor to deflect an asteroid.”  In other words, we’re going to whack Didymoon really hard to see how much we can change its orbit around Didymos.

Honestly, I feel a little bad for Didymoon, but the results of this experiment will help us prepare for the day when we need to smack an incoming asteroid off of a collision course with Earth. This is important for science, and someday it may save a whole lot of lives.

And I am really, really proud to say that one of my drawings is being used (with permission, of course) in the Didymos Observer Workshop’s promotional material.  Click here to check it out!

Sciency Words: Triangular Trade

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today I’m really stretching my conception of science-related terms so we can talk about:

TRIANGULAR TRADE

When I was a kid, I had an extensive collection of cards from Star Wars: The Customizable Card Game. At one point, I was trying to trade with a friend to get his Millennium Falcon card, but I didn’t have anything my friend wanted. So we got a third person involved and set up a three-way trade. My extra Princess Leia card went to this third person, who then gave a rare star destroyer to my friend, who then gave me the Millennium Falcon I needed to complete my rebel fleet.

This was sort of like what happens in triangular trade. Like nerdy kids trading Star Wars cards (or non-nerdy kids trading, I don’t know, baseball cards or something), cities or regions or countries set up three-way trade arrangements for their exports. This kind of arrangement served as the basis for much of the world economy in the 18th and 19th Centuries, during the Age of Colonialism.

The most commonly cited example (unfortunately) is the slave trade, where the trade routes between Europe, Africa, and the Americas actually traced out a big triangle across the Atlantic Ocean. European nations exported manufactured goods to their African colonies, which then exported slaves to the American colonies, which then exported things like sugar, cotton, tobacco, etc to Europe.

Obviously triangular trade is more of a historical term than a sciency thing, but much like the word thalassocracy, I feel like this old, history-related term might become applicable again in a far-out, Sci-Fi future where humanity is spreading across the Solar System. And the reason I think that is because Robert Zubrin, one of the foremost Mars colonization advocates in the U.S., wrote about triangular trade in his book The Case for Mars and also in this paper titled “The Economic Viability of Mars Colonization.”

To quote Zubrin from his “Economic Viability” paper:

There will be a “triangle trade,” with Earth supplying high technology manufactured goods to Mars, Mars supplying low technology manufactured goods and food staples to the asteroid belt and possibly the Moon as well, and the asteroids and the Moon sending metals and possibly helium-3 to Earth.

So everybody wins! The people of Earth win, the colonists on Mars win, and all the prospectors and mine workers in the asteroid belt win! Even our moonbase wins (this part might seem counterintuitive, but the delta-v to reach Earth’s Moon from Mars is actually lower than the delta-v to reach the Moon from Earth). And this time, slavery isn’t involved!

Unless the high technology being exported from Earth includes robot slaves who then… hold on, I have to go write down some story ideas.

Sciency Words: Frost Line (An A to Z Challenge Post)

Today’s post is a special A to Z Challenge edition of Sciency Words, an ongoing series here on Planet Pailly where we take a look at some interesting science or science related term so we can all expand our scientific vocabularies together. In today’s post, F is for:

FROST LINE

They say it’s cold in space. That’s not quite true. First off, how do you define what temperature means in a vacuum? That’s a much harder question that you might think.

But secondly—and more importantly for today’s post—a lot depends on where you are in space, because if you happen to be anywhere near a star, I guarantee you will feel the heat.

If you read enough scientific literature about space, you’ll eventually encounter the term “frost line,” and you’ll probably be able to guess from context what it means. Objects on one side of the line are close enough to the Sun for ice to melt (or more likely, sublimate), while objects on the other side are far enough away that ice remains frozen.

In our Solar System, the frost line is usually placed somewhere in the middle of the asteroid belt.

But there’s a lot of disagreement about where specifically the frost line is, in large part because there’s a lot of disagreement about how, specifically, the term should be defined.

Some astrophysicists define the frost line based on temperature conditions in the Solar System today. Others define it based on conditions from back when the Solar System was still forming. Also, there can be different frost lines for different chemicals, because the freezing point of water is different than that of methane or nitrogen or carbon dioxide.

This is a case of how some scientific terms are more clearly and precisely defined than others. And yet despite all the ambiguity about the frost line (or lines), it is still an incredibly useful term to help describe the layout of the Solar System. Which is why, if you read enough scientific literature about space, you are bound to come across this term eventually.

Next time on Sciency Words: A to Z Challenge, where did the word gravity come from?