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Posted by Phil Plait

Oh, I love stories like this: “Citizen scientists” —people who are not necessarily trained scientists but are enthusiastic and eager to take part in scientific research— have discovered a brown dwarf near the Sun. They examined data taken by an orbiting observatory and found the little beastie right at the edge of the telescope’s detection capabilities.

OK, first: Simply put, a brown dwarf is an object that is in between the mass of a planet and a star. That’s really too simply put; we’re talking about a rich and diverse class of objects, every bit as varied and interesting as planets and stars themselves (for that reason, I think it’s unfair to call them “failed stars,” as some do; they are their own thing, and fascinating in their own right). You can find out a lot about them by watching my brown dwarf episode of Crash Course Astronomy:

Being warmish, brown dwarfs tend to emit most of their light in the infrared part of the spectrum, outside the color range our eyes can see. But we can build detectors that are sensitive to infrared, attach them to telescopes, launch them into space, and sweep the sky to see what’s out there.

Astronomers have done this, many times, including with the wonderful Wide-field Infrared Survey Explorer, or WISE, for several years starting in 2010. It looked in four different wavelengths (colors) of IR light, creating a vast catalog of objects in the sky — over three-quarters of a billion of them.

A lot of those objects were brown dwarfs. They were found in two ways: Either by their colors (they tend to emit light at a specific IR color, making them stand out in WISE images) or by their motion. Brown dwarfs are extremely faint, so we only see ones that are relatively nearby the Sun (like, out to 100 light-years away or so). Because they’re close, their motion in space as they orbit the galaxy means we can see them move over time … it’s just like nearby trees seem to whiz past you when you’re in a car, when more distant object appear to move more slowly. Finding moving brown dwarfs is hard; they’re faint and look little more than blips in the images. This makes automating the search difficult (computers are easy to fool). But the human eye is good at seeing such things! And such a task doesn’t need a lot of training, either.

star sizes to scale

Size comparison of a normal star like the Sun, a red dwarf, a brown dwarf, and Jupiter. Credit: NASA's Goddard Space Flight Center

That’s why the folks at Zooniverse decided to take this on. This is a group of astronomers and researchers who figured out that non-scientists can not only participate in scientific research but also give a meaningful contribution to it as well. They collect data in the public domain (quite a bit of astronomical data) and present them in such a way that people can analyze them through simple tasks. For example, Galaxy Zoo asks people to identify spiral galaxies and determine whether the arms open clockwise or counterclockwise. Simple, fun, and oddly addictive, in fact. I’ve identified hundreds of galaxies myself there, and they’ve published quite a few papers on the results.

They did a similar project with the WISE images. Called Back Yard Worlds, it blinks four images from WISE observations taken of the same part of the sky at different times. The images have been processed a bit, subtracting one from another, so that fixed objects like stars and galaxies are suppressed, hopefully leaving behind moving targets. Your task: Look for the things that change. It’s not easy; I just tried it and there are lots of things that can fool the eye. But if enough people look at enough images, things turn up.

brown dwarf animation

Animation showing the very subtle motion of WISEA J110125.95+540052.8 in the four WISE images. Credit: NASA / WISE

And something did: On February 1, 2017, less than a week after the launch of Back Yard Worlds, a user spotted what looked like a slowly moving object. It appears as a “dipole,” a shifting spot of black and white due to the way the images were subtracted from one another. Two days later, another user spotted it, then three more not too much after that.

Clearly, the object was real. At this point, professional astronomers used NASA’s Infrared Telescope Facility, a 3-meter telescope in Hawaii, to observe the object, and they quickly determined it was indeed a brown dwarf.

It has been dubbed WISEA J110125.95+540052.8 (after its coordinates in the sky), and it’s about 110 light-years away. Not much is known about it except that it has a spectral type of T5.5, meaning it’s an intermediate mass and cool brown dwarf (with a temperature of very roughly 650-1250°C, much cooler than the Sun).

Brown dwarf before and after

Two WISE observations (each composed of several images added together) taken five years apart show the motion of the brown dwarf. Credit: Kuchner et al.

This is exciting for many reasons. For one, finding a single brown dwarf in the data implies that there are more to be discovered; the researchers estimate that more than a hundred previously undiscovered brown dwarfs should be hiding in the WISE data, waiting to be found. A half dozen or so of them may be Y dwarfs, the very coolest kind seen: Some are no warmer than room temperature!

Another reason is that I love that the public gets a chance to get their feet wet with real data. This isn’t some simulation, or some overly simplified homework assignment. This is real science, with real data, that could have a real impact. And in this case, it did, and will continue to do so. It’s wonderful that non-scientists, laypeople, can have the chance to participate in that.

And finally, there’s the potential of this. There is a lot of data out there. Did you know that all Hubble data older than one year is available through an archive? It’s not like you can just grab it and discover strange, new worlds —unlike Zooniverse, CosmoQuest, and other citizen science projects, there’s a huge overhead and learning curve with Hubble data— but there are thousands upon thousands of images and spectra just waiting to be analyzed, far more than the scientists who took them could ever hope to process.

And that’s just Hubble. Cassini, the Mars rovers, Juno … there are dozens of observatories and spacecraft with data just sitting there. What treasures lie within? What discoveries patiently await us? What new kinds of objects, old objects behaving in new ways, new phenomena, have already been captured by these eyes on the sky … biding their time until human eyes gaze upon it?

This idea is thrilling. The whole Universe is out there, and you can be a part of unveiling it.

Tip o’ the dew shield to Astrobites.

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Posted by Phil Plait

Just over two years ago, the New Horizons spacecraft provided humanity with its first close-up photos of Pluto in history.

These images changed the way we see the icy world forever. What we learned was staggering. It has vast, smooth regions on its surface indicating they’re geologically young; mountains as tall as the Rockies but made entirely of water ice; strong implications of liquid water under its surface despite the bone-shattering cold temperatures on the surface.

The close encounter lasted only a few hours, because you have a choice: Get to Pluto in less than a lifetime, or spend more time there. Pluto is so far away that even New Horizons, barreling across the solar system at 14 kilometers every second, still took nearly a decade to get there. It was traveling so rapidly that the visit was short.

 

But, despite the rapid flyby, there’s an advantage to moving faster than a speeding bullet: There are other targets out there in the inky depths of the outer solar system, and if you plan things right, you might just get to see them, too.

Even before the Pluto encounter, astronomers started trolling that region of space to look for another suitable target. They found one: 2014 MU69, an icy chunk of debris likely at most 20-40 kilometers across. It orbits far, far past Neptune, 6.5 billion kilometers from the Sun. It’s part of the Kuiper Belt, a ragtag collection of material left over from the formation of the solar system itself. If you don’t count Pluto (and I do), the first Kuiper Belt Object seen was only in 1992, and we now know of thousands.

But they’re so far away and so small that it’s hard to know what they’re like in detail. And that’s why MU69 is so important. New Horizons will show it to us up close for the first time.

The plan is for the spacecraft to fly within 10,000 km of MU69 on January 1, 2019. Maybe closer. But, to do that, we need to know more about it. How big is it? What shape is it? Is there anything else around it that could interfere with the flyby, like moons, rings, or debris?

These things are difficult to determine, but astronomers got a big clue this week due to geometry. In this case, the stars literally aligned.

Well, the Earth, MU69, and a star aligned. On July 17, 2017, from certain points on Earth, MU69 appeared to pass directly in front of a faint star. Astronomers call this kind of event an occultation, and when it happens, the star’s light is blocked, and it seems to momentarily disappear! In a sense, in this case, we’re in the shadow of MU69.

The occultation provides critical information: Because we know how fast MU69 is moving across the sky, the length of time the star blinks out tells us the width of MU69.

But there’s more. If you observe the occultation from different locations, you see different parts of MU69 passing in front of the star. If it’s a perfect sphere, then some locations will see a shorter occultation because the star cuts a chord behind it, not the full diameter. In fact, the shape itself can be determined by how long the occultation lasts at different positions on Earth.

map of occultation

Map showing the path of the shadow of 2014 MU69 across the Earth. Credit: SwRI

So New Horizons scientists dispatched telescopes to South America, where the shadow of MU69 was determined to fall across the Earth. In all, a couple of dozen small (40 cm) ‘scopes were deployed, equipped with cameras to record the event.

And … they caught it! At least five telescopes saw the star blink out. That, too, is very useful: If a ‘scope didn’t see it, then that provides an upper limit to the size of MU69 as well. The entire occultation lasted less than two seconds, too, so timing and location were everything here.

animation of occultation

Animation of the star blinking out as MU69 passed in front of it. This is actual data from the event; the time between frames is 0.2 seconds. Credit: NASA / JHUAPL / SwRI / Emily Lakdawalla

 

The data are still being processed, and we should have some numbers soon. I’ll note that there were two predicted occultations of two different stars before July 17, but nothing was seen. That means MU69 is probably smaller than previously thought, which, in turn, means it might be more reflective — if we know the distance and how bright it is, then its size depends on how shiny it is. A darker object would have to be bigger to look brighter, so even this non-detection tells us more about it.

My friend and super-solar-system-science communicator Emily Lakdawalla has more about the efforts to record this event. She also wrote a nice piece on what we knew about MU69 from a couple of years back, too.

I can’t stress enough just how difficult this sort of event is to plan! MU69 was only discovered in 2014 using Hubble images. It has a visual magnitude of 27 — that means the faintest star you can see with your unaided eye is 250 million times brighter! Then, using those images, the team had to calculate an orbit for it, and do so with such precision that they could extrapolate where it would be over the next year or two and see if it would pass in front of any stars. Then they had to plan the logistics of all that travel, coordinating the mission and making sure the data were recorded. Yet, as difficult as all that was, they were able to do it so well and with such accurate timing that several of the telescopes did in fact see the star blink out.

Mind you, MU69 is far, far too faint to even see with the telescopes used. So the astronomers had to keep taking data and hope.

And it paid off. Now, armed with more data, they’ll be able to plan the upcoming encounter with a little more confidence. As for what we’ll actually see when New Horizons gets to MU69, well, no one really knows.

If we did, it wouldn’t be exploration now, would it? But in less than 17 months, we’ll find out.

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Posted by Phil Plait

The European Space Agency’s current ExoMars mission has had a bumpy ride from the third to the fourth planet from the Sun, but right now things are looking good.

Launched in 2016, the mission had two parts: The Trace Gas Orbiter (or TGO), which was designed to orbit Mars and investigate the planet’s atmosphere, and the Schiaparelli lander, which was mostly a technology testbed to better understand how to land robotic explorers on Mars. NASA has done the latter many times — not always successfully —  but ESA hasn’t done so yet.

TGO is doing fine. It was initially on a long, elliptical orbit around Mars (the easiest kind to establish upon arrival) but has been executing a series of short engine burns that drop the low point in its orbit (called periareion, for “near to Mars”) into the upper parts of the atmosphere. That causes drag with the thinly distributed molecules there, taking energy away from the spacecraft’s orbit, lowering and circularizing it. Called aerobraking, this maneuver will eventually put TGO into a circular orbit at a height of about 400 km above the surface. The spacecraft will then orbit the planet once every two hours or so.

That will happen in 2018. Right now, it’s still in the elliptical orbit that stretches from about 200 km above the surface to 33,000 km out. That’s still a useful path! For example, it passed about 7700 km from the Martian moon Phobos, and dusty, battered space potato of a satellite, and took this pretty nifty image in October of 2016:

Phobos

Phobos, one of the two small moons of Mars. It’s about 27 km across through its long axis. Credit: ESA/Roscosmos/CaSSIS

It also has been observing the thin air of Mars, detecting carbon dioxide (the major component) as well as small amounts of water vapor. Eventually it will look for traces of methane, which has been positively detected in the Martian atmosphere but is poorly understood. On Earth, the major source of methane is biological activity, including livestock (by, um, outgassing) and human activity, including production and use of coal. It’s a greenhouse gas, but methane molecules are fragile and tend to react easily when oxygen is present. In Earth’s air the amount of methane is more or less stable, with the destruction of the molecules balancing their creation. That’s good, because methane is a very strong greenhouse gas, stronger than CO2.

Its presence on Mars is more difficult to explain. It’s due to some sort of geological process, but just what isn’t well known. TGO will map its concentration and location, hopefully providing needed clues to the gas’s origin.

Mellish crater

TGO mosaic of part of Mellish Crater, a 100 km wide crater near the Martian south pole. It was assembled from 40 images taken on March 5, 2017. Credit: ESA/Roscosmos/CaSSIS

Things, however, are not so good for the Schiaparelli lander. In fact, that part of the mission, in some sense, ended before it really began: It crashed into the planet on October 19, 2016, instead of softly touching down.

The crash investigation recently ended, and they found that a confused measurement device on board Schiaparelli instigated the impact. The lander deployed from the orbiter cleanly on the way to Mars. As the lander entered the upper atmosphere, the parachute also deployed as designed. However, it caused the lander to vibrate, or oscillate, for a few moments. A device called an inertial measurement unit confused that motion for a rotation of the spacecraft and got a reading far higher than it was designed for. It saturated, basically pegging the needle.

This only lasted for about a second, but that was enough. The odd reading was interpreted by the lander as its being upside-down, and the software wasn’t designed to handle that. When it did the math, it incorrectly calculated that it had a negative altitude, and so it interpreted this as being on the surface. It ejected the parachute and fired its landing thruster, but it was far too early and for too short a time.

This happened while it was still 3.7 kilometers (over two miles) above the surface. It free-fell the rest of the way, impacting Mars at a speed of 370 km/hour — nearly four times faster than a car on the highway. It didn’t survive. The impact scar and debris have been spotted by other orbiters.

Schiaparelli crash site

The Schiaparelli crash site, imaged by the Mars Reconnaissance Orbiter in November 2016. The surface disturbance is obvious, and the brighter dots around it may be debris from the spacecraft. The image is about 234 meters on a side. Credit: NASA / JPL / UA / Emily Lakdawalla

The good news is that the engineers learned a lot from the event, and won’t make those same mistakes a second time. In fact, they’ve said that some of the errors leading to the crash wouldn’t have been detected if the lander had made it down safely, and that could have led to disaster on a future mission. Since Schiaparelli was designed to test the hard- and software, in one way, this was fortunate. Better Schiaparelli than a far more sophisticated and expensive science lander.

Not that this crash was a good thing, but when it comes to space travel, every mistake is a chance to learn. At least, in this case, the loss was minimized.

Mars and the Sun
In mid-July 2017 Mars and the Sun are very close together in the sky. Credit: Sky Safari

Right now, Mars is nearly on the opposite side of the Sun as seen from Earth. Our orbit is closer to the Sun, and faster. Once every 26 months or so, we pass between the Sun and Mars, and then, roughly 13 months later, the Earth is on the opposite side of its orbit from Mars (remember, Mars moves, too, so it takes a while for us to pull ahead); this means that, from Earth, Mars and the Sun are very close together in the sky (called solar conjunction). That means it’s more difficult to communicate with spacecraft there — the Sun is the brightest radio source in the sky — so TGO has been commanded to sit tight in its current orbit for now. In a few weeks, it’ll start dipping its orbit again, hopefully on its way to a nice, stable circular science orbit.

It joins a veritable fleet of other robotic craft there, including some from the U.S., one from India and another by the ESA. It may be quite some time before humans go to the Red Planet, but our uncrewed proxies are still working apace. Mars is dry and cold and probably lifeless, but that doesn’t mean it’s not a dynamic and interesting world. I’m glad humans all over our planet are still interested in exploring it.

[Top image: ESA/ATG medialab]

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Posted by deb

Like clockwork every summer, I decide that the only thing I want to eat, maybe forever because when it’s warm out I completely forget winter is coming (I’m sorry, I had to), are variations on tomato-cucumber salad. We did a world tour of these last year and it might take me another decade of Smitten Kitchen-ing but I will get to them all. Left to our own devices, my husband and I probably would probably eat do exactly this for dinner at least a couple nights a week but when feeding kids, I always feel the need — I mean, what are they, growing rapidly and we’re supposed to fuel them with balanced meals or something? — to provide a little more than a bowl of cucumbers and tomatoes for dinner. You know, protein and stuff.

swirl of hummus with olive oil, za'atar

In the U.S., we generally think of hummus (which simply means “chickpea” in Arabic) as a cold snack, a dip you buy in the fridge case to help distract you from, say, cool ranch potato chip dip or something. But throughout the Middle East, there are hummusiots/hummsias, places that serve hummus warm and freshly made, often a little softer than what we get here, usually heaped with other things. Yes, as a meal; a heavenly one. Toppings might include additional tahini or chickpeas, cooked fava beans (ful), sautéed mushrooms, roasted beets, hard-boiled eggs, falafel, spicy ground beef, chopped tomato-onion-cucumber salads, pickles, and/or green olives plus always a stack of freshly baked puffy pitas. In some areas, hummus is a breakfast food, accompanied with labneh and mint. And it is from daydreaming about all of this — with a reminder from this oh-so-tempting Ina Garten photo from last week — that I realized that the easiest way to turn my tomato-cucumber salad obsession in to a meal was to serve it hummusiot-style.

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Posted by Phil Plait

Today, some bittersweet spacecraft news: The LISA Pathfinder mission is shutting down. That’s always a bit sad, but in this case, in sum, it’s actually good news: That’s because it accomplished all its goals. And even better, it means that a bigger, beefier mission will take its place! That mission, called LISA, was recently approved by the European Space Agency to continue its planning phase, aiming for a launch in 2034.

Why am I happy about this? Because LISA is the Laser Interferometer Space Antenna, and it will use what is essentially Star Trek technology to detect merging black holes all across the Universe.

So, yeah. How awesome is that? And, for a while, I feared it would never get off the ground. It hasn’t yet, but the odds are looking much better now.

OK, you probably want a modicum of background here. I’ll be glad to help.

Maybe you’ve read reports about LIGO, the Laser Interferometer Gravitational-Wave Observatory, which recently detected black holes merging for the third time. I wrote about that event and gave a lot of background a couple of years ago when LIGO bagged its first black hole coalescence.

In a nutshell, one of the predictions of Einstein’s Theory of Relativity is that when matter is accelerated it creates ripples in the fabric of spacetime, much as shaking a bedsheet up and down causes ripples in the fabric. These ripples are stronger if the objects are very massive, very dense and accelerated very rapidly.

You don’t get more massive, more dense and more accelerated things in this Universe than two black holes at the very moment they eat each other.

 

There are a few ways this can happen. Probably the most common is from black holes that form when massive stars explode. If those stars are orbiting each other in a binary system, then, eventually, after both stars blow up, you get two black holes orbiting each other. As they emit gravitational waves — those Einsteinian spacetime ripples — they spiral in toward one another. Over a long time (usually billions of years), as the distance between them closes, they orbit faster and faster. Then, finally, accelerating each other to very nearly the speed of light, they merge into a single bigger black hole, emitting a fierce, sharp blast of gravitational waves.

These ripples in spacetime then move across the Universe at the speed of light. When they wash over our planet, they physically compress and expand space itself. The effect is incredibly tiny by the time these waves reach us: A typical ruler would only shrink or expand by a tiny fraction of the size of a proton! But these effects can be measured because we are very clever apes, we humans.

LIGO was built to find these ripples, and after decades of trying, it works! It can now feel the Universe shake as black holes collide.

Merging black holes art

 

But LIGO, as amazing as it is, isn’t nearly as sensitive as what’s possible. Enter LISA.

LISA is similar to LIGO, but it’ll be in space. There are lots of advantages to this. For example, LIGO is so sensitive it has to worry about individual oxygen atoms hitting its mirrors, distorting the signal. In space there’s no air, so that’s an improvement.

Also, this stretching of spacetime is easier to measure if you have a longer baseline. If your detector is short it only stretches and contracts a little bit, but if it’s 10 times longer the effect is 10 times bigger. LIGO has mirrors spaced a few kilometers apart, making it highly sensitive. Because LISA is in space, its detectors can be much farther apart. In fact, the plan right now is for the components to be separated by about 2.5 million kilometers!

If you want to think of it as sound (which it isn’t, but the analogy isn’t bad), LIGO can hear the loudest black hole mergers. LISA will hear the whispers. In fact, it should also be able to detect mergers between neutron stars and even white dwarfs, which are far “quieter” than their denser black hole brethren.

So, how does it work? LISA is actually three disc-shaped spacecraft, launched together on one rocket. They each have an onboard propulsion system that will move them to their final separation of several million kilometers, forming an equilateral triangle in roughly the same orbit as Earth, but 20 or so million kilometers away from us.

Like LIGO, LISA will use lasers. Each spacecraft will have onboard two lasers, each of which will fire at one of the other two spacecraft. Using a technique called interferometry, the distances between the spacecraft can be measured with utter precision:

 

But there’s a problem with this. The spacecraft need to be able to measure their relative positions with incredible accuracy, so that the teeny tiny effects of a passing gravitational wave can be measured. But there are lots of forces in space that would totally wash that out. Tides from the Earth, Moon, and Sun, cosmic rays, solar wind and more would all be far stronger, moving the spacecraft around and ruining the measurements.

To overcome this, inside each laser assembly is a small, exquisitely crafted cube made of gold and platinum (yes, seriously; they’re very stable and that makes them useful). Each cube, called a test mass, is about 4.5 or so centimeters on a side and has a mass of about 2 kilograms. They are totally disconnected from the LISA spacecraft, untouched by it in any way, allowed to float completely freely. The tolerance is extreme: No force on the cube is allowed more than about that exerted by the weight of a bacterium.

See what I mean by Star Trek technology?

LISA spacecraft

Artwork showing one of three LISA spacecraft “connected” to the other two (one above and to the left, the other off screen to the left; both 2.5 million km away) via lasers. Credit: AEI/Milde Marketing/Exoze

 

In this way, the cubes are freely floating in orbits around the Sun, and the spacecraft keep position around them. Using extremely sensitive sensors, each spacecraft keeps itself precisely aligned with the cube inside it, measuring their exact location at all times. 

The cubes act as benchmarks for the spacecraft around them. As long as the cubes are allowed to move freely, then a gravitational wave passing through them would change their relative separation, allowing it to be detected. The spacecraft act like shields, preventing outside forces from affecting them … really, these forces affect the spacecraft, which then use incredibly low-thrust engines to maintain their strictly controlled positions. If there’s a force on the spacecraft, say the solar wind, then the thrusters counteract that to make sure the spacecraft stays perfectly centered around the cubes. And I do mean weak: It would take a thousand of these thrusters to generate the same weight as a piece of paper in your hand!

LISA test mass

The LISA Pathfinder test mass, very similar to the ones that will be used on LISA. It's a cube of gold and platnium with a mass of about two kilos. Credit: RUAG Space, Switzerland

 

I like to think of all this using an odd analogy: curling. That’s a sport played on an ice lane where a player throws a heavy mass (called a stone) and tries to place it in a target area downrange. Other players, called sweepers, have brooms and they rapidly sweep the ice ahead of the stone, decreasing the friction and making sure the stone’s trajectory is true.

For LISA, the test masses are the stone, and the sweepers are the spacecraft. They never touch the stone, but they make sure its path is true.

Now, if a gravitational wave passes through the LISA spacecraft, the pattern of light created by the laser changes, and this can be measured with ridiculous accuracy. Even though they will be separated from each other by a distance several times greater than the distance of the Moon from Earth, they will measure their relative positions to an accuracy of a few trillionths of a meter. Yes, trillionths. For those who love words as much as I do, a trillionth of a meter is a picometer. Feel free to work that into your next conversation.

And, again, this exemplifies the idea of how astonishingly advanced this tech is.

This brings us back to LISA Pathfinder. We know all this technology needed for LISA will work because the European Space Agency successfully tested it using Pathfinder. It launched in late 2015 and was equipped with lasers, cubes and other bits of tech LISA will utilize to measure the whisper from colliding hyperdense cosmic objects. It was amazingly successful and completed its mission on June 30. Today it will be shut down, having paved the way for LISA to continue.

I’m glad this is happening. Many years ago, NASA was partnered with the European Space Agency to help build LISA. I actually worked a bit on the Education and Public Outreach for the mission, writing up descriptions of how it worked and what it would do. But shortsighted budgetary decisions meant NASA had to pull out of the development, which upset me greatly at the time.

However, over time and with a lot of cajoling by scientists, the U.S. has rejoined the mission as a senior partner, with the ESA leading the way. I’m very glad to see this. Now that LIGO has shown we can detect gravitational waves, and LISA Pathfinder has shown the advanced technology is possible, LISA itself will open the floodgates of data. It took a huge effort for LIGO to allow us to dip our toes in the water. Hopefully LISA will let us dive in.

My thanks to NASA LISA Study Scientist Dr. Ira Thorpe for talking to me about how the spacecraft measure their distances and clearing up a misconception I had about the test masses!

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I am prepared to fight about this, Internet. Come at me.

New comic!
Today's News:

Last full day to support the latest launch. Thanks, geeks!

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