Why Is It Taking So Long To Figure Out Planet Nine?

We have the mass and orbital parameters of a large planet in the outer solar system. Astronomers don’t seem to care?

Originally posted on Forbes!

Nothing short of caring deeply can cause astronomers to publish such a burst of papers on an as-yet theoretical planet, too distant to have already been captured by our numerous telescope facilities. A recent paper counts twenty two new publications from planetary scientists in 2016, assessing the specific claims of a paper that came out almost exactly a year ago, on the 20th of January, 2016. Over twenty papers in a year is a pretty substantial achievement for any individual object - in fact, off the top of my head, the only other single object that reached those dizzy heights in 2016 is Boyajian’s Star (also known by its technical name KIC 8462852), which you may remember as the alien megastructures star (it was not alien megastructures).

So what did those twenty-two papers turn up? Well, as you say, they’ve narrowed down the mass and orbital parameters of the planet proposed by Batygin & Brown in 2016, which elaborated on an original suggestion by Trujillo & Sheppard in 2014. The 2016 suggestion was covered quite widely - it’s not every day you hear that there might be a mystery planet floating around the very edges of our solar system - but it was, fundamentally, only a suggestion. Batygin & Brown looked at the sample of data that they had, and concluded that one explanation would be a giant large planet, nudging tiny little icy worlds into very specific orbits.

This artists concept contrasts our familiar Earth with the exceptionally strange planet known as 55 Cancri e. While it is only about twice the size of the Earth, NASA's Spitzer Space Telescope has gathered surprising new details about this supersized and superheated world. New observations with Spitzer reveal 55 Cancri e to have a mass 7.8 times and a radius just over twice that of Earth. Those properties place 55 Cancri e in the "super-Earth" class of exoplanets, a few dozen of which have been found. Image credit: NASA/JPL-Caltech/R. Hurt (SSC)

This artists concept contrasts our familiar Earth with the exceptionally strange planet known as 55 Cancri e. While it is only about twice the size of the Earth, NASA's Spitzer Space Telescope has gathered surprising new details about this supersized and superheated world. New observations with Spitzer reveal 55 Cancri e to have a mass 7.8 times and a radius just over twice that of Earth. Those properties place 55 Cancri e in the "super-Earth" class of exoplanets, a few dozen of which have been found. Image credit: NASA/JPL-Caltech/R. Hurt (SSC)

What followed was a flurry of papers, as other planetary scientists who specialize in the outer solar system descended on the idea of this specific incarnation of a distant 9th planet. One team went hunting through a bunch of existing survey data, and found nothing, which meant if such a planet really is out there, it had to be fainter (either more distant or cooler) than the faintest objects captured in the survey. That result doesn't rule out the planet entirely, but it puts boundaries on it.

The papers have kept coming, and with each one, the range of options for this planet grow smaller and smaller. Simulations have been run to test how unlikely our observations of the solar system are. If a planet were there, would we expect to see this setup in our solar system? That particular simulation leans towards no - which should make you suspicious of whether we understand the data as well as we would like. More data is being taken to see if the planet’s signature in our view of the solar system is a bias in the way we hunt for these objects.

Scientists, and astronomers are no exception, are cautious creatures. What we are seeing at the moment is a live, highly publicized, discussion on the various merits and demerits of the idea of a ninth, very distant, planet. But each piece of the puzzle, as data is taken and analyzed, takes time to process, time to analyze, and time to figure out how it fits in with everyone else's work. It's a lengthy process, and everyone wants to get their part right. We won't have a final answer on this version of Planet Nine until it is directly discovered or its existence can be entirely ruled out - in either case it will be a few years of work.

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How Fast Are You Moving Through Space?

While standing in my back yard, how fast am I moving through space considering Earth’s rotation, Earth’s orbit around the Sun, the Sun’s orbit around the Galaxy, et cetera?
This image, taken by ESO Photo Ambassador Alexandre Santerne, is more than a little disorientating at first glance! Resembling an optical illusion or an abstract painting, the starry circles arc around the south celestial pole, seen overhead at ESO's La Silla Observatory in Chile. Each circular streak represents an individual star, imaged over a long period of time to capture the motion of the stars across the sky caused by the Earth’s rotation. La Silla is based in the outskirts of Chile’s Atacama Desert at some 2400 metres above sea level, and offers perfect observing conditions for long-exposure shots like this; the site experiences over 300 clear nights a year! The site is host to many of ESO’s telescopes and to national projects run by the ESO Member States. Some of these telescopes can be seen towards the bottom of the image. The ESO 3.6-metre telescope stands tall on the left peak, now home to the world's foremost extrasolar planet hunter: the High Accuracy Radial velocity Planet Searcher (HARPS). Other telescopes at La Silla include the New Technology Telescope, which partly masks the ESO 3.6-metre telescope, Swiss 1.2-metre Leonhard Euler Telescope, ESO 1-metre Schmidt, the silver-domed MPG/ESO 2.2-metre, Danish 1.54-metre, and ESO 1.52-metre telescopes, which are visible here. Taking all these facilities together, La Silla is one of the most scientifically productive ground-based facilities in the world after ESO’s Very Large Telescope (VLT) observatory. With almost 300 refereed publications attributable to the work of the observatory per year, La Silla remains at the forefront of astronomy. Image credit: ESA/ A. Santerne

This image, taken by ESO Photo Ambassador Alexandre Santerne, is more than a little disorientating at first glance! Resembling an optical illusion or an abstract painting, the starry circles arc around the south celestial pole, seen overhead at ESO's La Silla Observatory in Chile. Each circular streak represents an individual star, imaged over a long period of time to capture the motion of the stars across the sky caused by the Earth’s rotation. La Silla is based in the outskirts of Chile’s Atacama Desert at some 2400 metres above sea level, and offers perfect observing conditions for long-exposure shots like this; the site experiences over 300 clear nights a year! The site is host to many of ESO’s telescopes and to national projects run by the ESO Member States. Some of these telescopes can be seen towards the bottom of the image. The ESO 3.6-metre telescope stands tall on the left peak, now home to the world's foremost extrasolar planet hunter: the High Accuracy Radial velocity Planet Searcher (HARPS). Other telescopes at La Silla include the New Technology Telescope, which partly masks the ESO 3.6-metre telescope, Swiss 1.2-metre Leonhard Euler Telescope, ESO 1-metre Schmidt, the silver-domed MPG/ESO 2.2-metre, Danish 1.54-metre, and ESO 1.52-metre telescopes, which are visible here. Taking all these facilities together, La Silla is one of the most scientifically productive ground-based facilities in the world after ESO’s Very Large Telescope (VLT) observatory. With almost 300 refereed publications attributable to the work of the observatory per year, La Silla remains at the forefront of astronomy. Image credit: ESA/A. Santerne

Originally posted at Forbes!

We can certainly figure this one out, with the caveats presented in one of my last articles – all these speeds that we measure will be with respect to something specific, and also arbitrary. So we can find out how fast you’re moving on the Earth’s surface because the Earth is rotating, relative to standing at the North Pole, where you would spin in place. We can figure out how fast you’re moving because the Earth is orbiting the Sun, relative to standing at the Sun. And we can figure out how fast we’re moving around the galaxy, relative to standing at the very center of the galaxy, and spinning that way.

Fair warning: this is going to get complicated. All of the motions I’m telling you about will be constantly changing direction, since everything is on a circular path. For instance, if the sun is setting, your direction of motion is roughly “away from the sun”. If the sun is rising, you’re roughly pointed “towards the sun”, and at midnight and midday, you’re moving sideways, relative to the sun.

On the left; a top down diagram of the Earth, showing the different directions your instantaneous motion would point, depending on your position on the surface. On the right; a side view, showing Earth’s rotational tilt, and the directions your motion points, where horizontal is direction of motion relative to the orbit around the sun. Image credit: Jillian Scudder

On the left; a top down diagram of the Earth, showing the different directions your instantaneous motion would point, depending on your position on the surface. On the right; a side view, showing Earth’s rotational tilt, and the directions your motion points, where horizontal is direction of motion relative to the orbit around the sun. Image credit: Jillian Scudder

So let’s start small. You are standing on a spherical planet (more or less) which rotates once every 24 hours. This is a 360 degree rotation in 24 hours, which works out to 15 degrees of rotation every hour. Cool, but you asked for your motion, which means we need to convert from angles to a velocity. If you draw a circle at a fixed rate (say you can draw an inch every second), the length of time you’re going to take to draw that circle depends on how big a circle you’re drawing. With the rotation of the Earth, you have almost the exact opposite problem. We know how much time it takes to draw the circle, but we don’t know how big the circle is, because it depends on where you are on the planet. If your backyard happens to be 3 feet away from the North Pole, then your circle is only 6 feet across, and you have 24 hours to make it around. Unsurprisingly, your speed here is really slow. You’re only going 10 inches per hour.

If your backyard is on the equator, your circle is much bigger – it’s the whole Earth across. The Earth is just over 7900 miles from surface to surface, if you tunnel through the middle, which means you have a lot farther to go in the same 24 hours. Your speed clocks in around 1,036 miles per hour, relative to the “motionless” North Pole.

We can do this again, scaled up for the Earth’s motion around the sun – it’s a little bit simpler because we know how big the circle drawn by the earth is – 1 astronomical unit, or just under 93 million miles lie between us and the Sun, which means we have a 584 million mile journey to make it through before the year is out. You’ll note that 584 million miles is a larger number of million miles than there are days in the year – and indeed this works out to needing to travel 1.6 million miles per day along our circular path. If we break this into units of miles per hour again, we get 66,658 mph.

To combine your motion around the Earth with your motion around the sun, you should add the two together, taking into consideration the relative directions. If you motion around the Earth happens to be pointed in the direction of the Earth’s motion around the sun, you need to add the two motions together. If you happen to be pointed away from the direction we’re moving as a planet, then you need to subtract the two. If you’re at the North Pole, or very close to it, this addition and subtraction makes no real difference to our 66,600 mph motion along our orbit, since you’re going almost 0 mph in the first place.

Description of relations between Axial tilt (or Obliquity), rotation axis, plane of orbit, celestial equator and ecliptic. Earth is shown as viewed from the Sun; the orbit direction is counter-clockwise (to the left). Image credit: Dennis Nilsson CC BY 3.0

Description of relations between Axial tilt (or Obliquity), rotation axis, plane of orbit, celestial equator and ecliptic. Earth is shown as viewed from the Sun; the orbit direction is counter-clockwise (to the left). Image credit: Dennis Nilsson CC BY 3.0

There’s one more complication in adding these two things together! The direction of your motion because the Earth is spinning (90 degrees from our axis of rotation) is not lined up with the direction of the motion of the Earth around the Sun. Our rotation is tipped sideways by 23 degrees. In that case, even if you’re pointed mostly toward the direction we’re moving around the sun, you’re also pointed up a little (or down a little). It’s like walking in a diagonal line, forward and to the right, but then realising you only cared about moving right. The forward motion you made doesn’t really help with moving to the right.

We can work out how much of our motion was “to the right” in the direction of the motion around the sun, and sum just those two segments together, but we can’t forget about our “up/down” motion either. If you figure out the geometry, our 1,036 mph of motion at the equator is equivalent to going 954 mph to the side, along our direction of motion. Or against our direction of motion – remember that as the planet rotates, our direction of motion is also changing, so depending on the time of day, our rotation around the planet will add an extra 954 mph at most, subtract 954 mph at most, and at the least consequence, make no change whatsoever, all relative to our hypothetical viewer in the Sun who can see us no matter what side of the planet we’re on. So your motion will appear to be somewhere between 65,700 mph and 67,600 mph in the direction of the planet’s motion, plus an up-or-down component somewhere between 0 mph and 400 mph depending on season and time of day.

This detailed annotated artist’s impression shows the structure of the Milky Way, including the location of the spiral arms and other components such as the bulge. This version of the image has been updated to include the most recent mapping of the shape of the central bulge deduced from survey data from ESO’s VISTA telescope at the Paranal Observatory. Image credit: NASA/JPL-Caltech/ESO/R. Hurt

This detailed annotated artist’s impression shows the structure of the Milky Way, including the location of the spiral arms and other components such as the bulge. This version of the image has been updated to include the most recent mapping of the shape of the central bulge deduced from survey data from ESO’s VISTA telescope at the Paranal Observatory. Image credit: NASA/JPL-Caltech/ESO/R. Hurt

It’s the same verse again for calculating the speed of the solar system around the Galaxy’s center, but with an extra round of calculating angles. Our solar system is about 8,300 parsecs from the center of the galaxy – where one parsec is 19,170,000,000,000 miles. (This sort of enormous number gets inconvenient, so for any kind of science, I would prefer to calculate things in parsecs rather than in miles.) With our best measurements of our own speed around the center of the galaxy, we’ve estimated our speed to sit somewhere around 220 kilometers every second, or 492,126 miles per hour. Our last set of numbers once again does not add easily, as the solar system sits at a 60 degree angle relative to the Milky Way galaxy – so if you do the math again, you can work out that we can at most add or subtract 34,156 mph to our sideways speed, getting us to somewhere between 526,282 mph and 457,970 mph. You’ll only hit those extremes once a year, at the right time of day, and it will only last an instant – most of the time we’ll be sitting somewhere much closer to the 492,126 mph average.

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Is time dilation real?

 

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What's the best way to clean up all that space junk?

What’s the best way to clean up all the junk we’ve left in space?
All human-made space objects result from the near-5000 launches since the start of the space age. About 65% of the catalogued objects, however, originate from break-ups in orbit – more than 240 explosions – as well as fewer than 10 known collisions. Scientists estimate the total number of space debris objects in orbit to be around 29 000 for sizes larger than 10 cm, 670 000 larger than 1 cm, and more than 170 million larger than 1 mm. Image credit: ESA

All human-made space objects result from the near-5000 launches since the start of the space age. About 65% of the catalogued objects, however, originate from break-ups in orbit – more than 240 explosions – as well as fewer than 10 known collisions. Scientists estimate the total number of space debris objects in orbit to be around 29 000 for sizes larger than 10 cm, 670 000 larger than 1 cm, and more than 170 million larger than 1 mm. Image credit: ESA

Originally posted at Forbes!

This is a big problem that many people are still trying to figure out, because there is a lot of junk out in space, and it is incredibly dangerous.

As of September 2012, we are currently monitoring 21,000 individual pieces of stuff orbiting the planet which are larger than about 2 inches. Anything this size which is going fast enough to stay in orbit poses a significant threat to satellites, spacecraft, and space stations. The ISS will regularly maneuver out of the way of space junk if we see it coming soon enough. If there isn’t enough time to move the whole ISS, then the crew members of the ISS have to take shelter in one of the Soyuz capsules which are attached to the ISS in case an emergency evacuation is needed.

ESA space debris studies: hypervelocity impact sample. The metal sheet is 18 cm in thickness, and the ball bearing 1.2 cm across, hitting at 6.8 km/s. Image Credit: ESA

ESA space debris studies: hypervelocity impact sample. The metal sheet is 18 cm in thickness, and the ball bearing 1.2 cm across, hitting at 6.8 km/s. Image Credit: ESA

The two inch limit on tracking isn’t an indication that there aren’t any pieces smaller than that, or that we don’t have to worry about the little ones; we simply can’t spot them from the ground. We fully expect there to be around 100 million more objects out there in the < 0.5 inch category. Even paint chips at orbital speeds can cause significant damage to a spacecraft. A few of the space shuttle missions had paint flakes impact the windshield of the craft, which is an unsettling sight to say the least.

Window pit from orbital debris on STS-007. Image credit NASA.

Window pit from orbital debris on STS-007. Image credit NASA.

I can tell you the worst way to clean up a dead satellite, which unfortunately happened in 2007; the Chinese military decided to test their anti-satellite technology on one of their dead weather satellites. This test successfully exploded the dead satellite, and created over two thousand new pieces of space debris, which, at the time, increased our space junk tally by 25%. (We had another spike in the space debris population after a dead, but intact, Russian spacecraft managed to collide with a not-dead privately owned satellite – that produced another 2000+ large pieces of debris.)

Known orbit planes of Fengyun-1C debris one month after its disintegration by a Chinese interceptor. The white orbit represents the International Space Station. Image Credit: NASA

Known orbit planes of Fengyun-1C debris one month after its disintegration by a Chinese interceptor. The white orbit represents the International Space Station. Image Credit: NASA

There have been a few suggestions on how to get the stuff that’s already up there down; some options are more passive than others; the space station Mir ran an experiment in 1996 where they attached pieces of gel onto the outside of the space station to see what kinds of microscopic space junk they could catch. (As an entertaining side note, this was part of the Mir Environmental Effects Package, or MEEP. This is definitely funnier now than it was in 1996.) They found a lot of liquid droplets, soap, and tiny paint fragments, along with pieces of broken spacecraft, and tiny electronic fragments. This was instructive, but not particularly effective for cleaning out the reservoir of stuff surrounding our planet.

The best method to date to keep the skies clear is to make sure that when you put a spacecraft up in space, it comes with a way to come down again. Usually this means that the craft should have a way to intentionally slow itself down enough to re-enter the atmosphere, which will allow most of the small pieces to burn away in the atmosphere due to the heat of re-entry. Large pieces may make it down to the surface, which is why the ‘intentional’ part of slowing down is important. Generally we like to dump the large pieces in the Pacific Ocean, since there aren’t any dense population centers in the middle of the ocean. If a spacecraft falls back to earth after it is 100% dead and unable to be controlled, then there’s no way to modify where it winds up falling, and it might come down on your favorite city. The standard way to slow yourself down is with a rocket, but there have been proposals to do this with a solar sail type contraption; at the end of the craft’s life, it could unroll the sail, which would then help to slow down the craft so it could fall back to Earth more quickly.

Scientists flying aboard NASA's DC-8 airborne laboratory captured this image of the Japan Aerospace Exploration Agency's Hayabusa spacecraft June 13, 2010 as it re-entered the Earth's atmosphere and began breaking up over the Woomera Test Range in southern Australia. The small object below and ahead of the main portion of the spacecraft was the sample return capsule, which was recovered intact after parachuting to a safe landing. JAXA scientists hope to recover samples of the asteroid Itokawa that Hayabusa visited in 2005 from the return container to help them understand the asteroid's composition. Image Credit: NASA

Scientists flying aboard NASA's DC-8 airborne laboratory captured this image of the Japan Aerospace Exploration Agency's Hayabusa spacecraft June 13, 2010 as it re-entered the Earth's atmosphere and began breaking up over the Woomera Test Range in southern Australia. The small object below and ahead of the main portion of the spacecraft was the sample return capsule, which was recovered intact after parachuting to a safe landing. JAXA scientists hope to recover samples of the asteroid Itokawa that Hayabusa visited in 2005 from the return container to help them understand the asteroid's composition. Image Credit: NASA

But those are only options for spacecraft which haven’t yet been launched, or have thought ahead more than most, and it doesn’t help get rid of the dead satellites we can’t communicate with, or any of the broken pieces of satellite shrapnel. For those, the only option is to send up some kind of clean-up satellite which can help slow down all the miscellaneous pieces. Again, there have been many proposals; the most plausible involve grabbing onto dead spacecraft somehow (perhaps with a net), and then de-orbiting as a pair (like e.Deorbit).

Unfortunately, we can’t just go up and push every dead satellite down to Earth; not only is this impractical in the extreme, all of the privately owned satellites are still privately owned regardless of whether or not they still work, and burning them up in the atmosphere would be burning someone else’s property, even if it doesn’t work anymore. For now, until some of these cleaner satellites can get up there and start pulling down some of the pieces, our main goal with space debris is simply to not produce any more than we already have.

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What could be low in the sky and flashing many colors?

I live on the east coast of the US (NJ). I noticed in August about 10pm looking ESE a star that was pulsing bright colors. It looked like an LED toy light flashing red, green, blue, red, white and yellow in very rapid succession. It was low in the sky and it is there every night I look. Please explain.
This image of a star field demonstrated that the framing cameras on board NASA's Dawn spacecraft were functioning flawlessly. They were obtained on March 16, 2011.  Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This image of a star field demonstrated that the framing cameras on board NASA's Dawn spacecraft were functioning flawlessly. They were obtained on March 16, 2011. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Originally posted at Forbes!

This is a great question, because you’ve given me pretty much all the information I need to figure out what you were looking at! Generally, if someone spots something in the sky that looks like it’s flashing, the first question we ask is “is it moving”, because if it’s moving, it’s probably a plane or helicopter, or a drone – something along those lines.

But your mystery object is not moving, and it’s not moving over the course of many nights. That eliminates another possibility, a nearby planet low in the horizon; planets are often extremely bright in the sky, but if you were looking for it every night, Mars or Venus would be shifting relative to things on your horizon, so you probably would have noticed. More distant planets like Jupiter or Saturn move much more slowly in our night sky, so they’re still possible culprits, but the other option is a very bright star. So we’re already narrowed down to a star or distant planet which appears low to the horizon for your mystery object.

The last piece of critical information you’ve given is that the object is low in the sky – this is what seals the picture. Very few astrophysical objects have intrinsic rapid flashes of color or brightness, which is to say that if we were observing them from the Space Station, from space, nothing out in the dark sky would appear to be flashing any colors. However, you are observing from the east coast of the US, not space, and the atmosphere is in your way.

The atmosphere is a major problem for astronomy. Most people typically assume that the atmosphere is generally transparent, and that light doesn’t interact with it in any major way. This is obviously false, if you think about it a bit more, given the fact that sunsets are due to light interacting with our atmosphere, but when the night is clear, and the stars are shining down, it’s easy to forget about our thin shell of air. Air bends light, and hot air bends light in a different way than cold air; it’s like having a series of lenses suspended above us, twisting and distorting the light on its way through. If the air is calm, these lenses made up of pockets of air don’t do much distorting. If the object is above you, the light from that star also has fewer air pockets to go through, so the light mostly makes it through intact.

However, if the light has to go through the atmosphere at a very shallow angle, as it does when the object appears low on the horizon, it must pass through a large number of these lenses. Because the atmosphere is only accidentally a lens, it doesn’t have to do a particularly good job of focusing of light, and it can produce a chromatic aberration. You may have heard this term from dealing with eyeballs or from dealing with fancy cameras; effectively it means that different colors of light are bent differently as they pass through a lens, and so certain colors wind up focusing in different places.

The atmosphere’s series of lenses are constantly changing, so the terrible focusing job that the air pockets are doing is also constantly changing. This results in exactly what you describe; a flickering effect, where the color of the bright object is changing, flicking between all of the possible rainbow of colors.

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