Special Guest: Astronaut Ron Garan (orbitalpersepctive.com / @Astro_Ron)
Ron will talk about his new book The Orbital Perspective: Lessons in Seeing the Big Picture from a Journey of 71 Million Miles.
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
You can join in the discussion between episodes over at our Weekly Space Hangout Crew group in G+, and suggest your ideas for stories we can discuss each week!
Almost all the planet hunting has been done from space. But there’s a new instrument installed on the European Southern Observatory’s 3.6 meter telescope called the High Accuracy Radial velocity Planet Searcher which has already turned up 130 planets. Is this the future? Searching for planets from the ground? Continue reading “Astronomy Cast Ep. 366: HARPS Spectrograph”
Whoa, here’s something to think about. Maybe the Universe isn’t expanding at all. Maybe everything is actually just shrinking, so it looks like it’s expanding. Turns out, scientists have thought of this.
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Video Transcript
It’s tinfoil hat day again at The Guide To Space. There’s some people who would have you believe the Universe is expanding. They’re peddling this idea it all started with a bang, and that expansion is continuing and accelerating. Yet, they can’t tell us what force is causing this acceleration. Just “dark energy”, or some other JK Rowling-esque sounding thing. Otherwise known as the acceleration that shall not be named, and it shall be taught in the class which follows potions in 3rd period.
I propose to you, faithful viewer, an alternative to this expansionist conspiracy. What if distances are staying the same, and everything is in fact, shrinking? Are we destined to compress all the way down to the Microverse? Is it only a matter of time before our galaxy starts drinking its coffee from a thimble or perhaps sealed in a pendant hanging on Orion’s belt? So, could we tell if that’s actually what’s going on?
Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.
Better get some scotch tape for the hats, kids. This one gets pretty rocky right out of the gate.
The first horrible and critical assumption here is that shrinking objects and an expanding universe would look exactly the same, which without magic or handwaving just isn’t the case. But you don’t have to take my word for it, we have science to punch holes in our Shrink-truther conspiracy.
Let’s start with distances. If we assumed the Earth and everything on it was getting smaller, we’d also be shrinking things like meter sticks. In the past they would have been larger. If everything was larger in the past, including the length of a meter, this means the speed of light would have appeared slower in the past. So was the speed of light slower in the past? I’m afraid it wasn’t, which really hobbles the shrinky-dink universe plot. But how do we know that?
The diagram shows the electromagnetic spectrum, the absorption of light by the Earth’s atmosphere and illustrates the astronomical assets that focus on specific wavelengths of light. ALMA at the Chilean site and with modern solid state electronics is able to overcome the limitations placed by the Earth’s atmosphere. (Credit: Wikimedia, T.Reyes)
You’ve probably seen spectral lines before or at least heard them referenced. Scientists use them to determine the chemical composition of materials. A changing speed of light would affect the spectral lines of distant objects, and because some people are just super smart and were able to do the math on this, we know that when we look at distant gas clouds we find the speed of light has changed no more than one part in a billion over the past 7 billion years.
Shrinking objects would also become more dense over time. This means that the universal constant of gravity should appear smaller in the past. Some have actually studied this, to determine whether it has changed over time, and they’ve also seen no change.
Artists illustration of the expansion of the Universe (Credit: NASA, Goddard Space Flight Center)
If objects in the Universe were shrinking, the Universe would actually be collapsing. If galaxies weren’t moving away from each other, their gravity would cause them to start falling toward each other. If they were shrinking, assuming their mass doesn’t change, their gravity would be just as strong, so shrinking wouldn’t stop their mutual attraction. A Universe of shrinking objects would look exactly opposite to what we observe.
So, good news. We’re pretty sure that objects, and us, and all other things in the Universe are not shrinking. We’re still not sure why anyone would name a thing Shrinky Dinks. Especially a craft toy marketed at children.
If Dr. Who has taught us anything, it’s that time is kind of crazy. And we’re not just talking about time travel here, we’re talking about regular old “now”. Well, what “now” means depends on where you are and how fast you’re moving.
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There are some topics that get a little frustrating in their pedantry, but can really draw attention to the grand scope and mechanics in our Universe. This is definitely one of them.
We know looking through a telescope is like looking into the past, both out from and towards our Earth. We know if alien ships were looking at the Earth right this moment from distant star systems they’d could well be watching dinosaurs chomping on each other’s adorable little faces.
So how do we know what’s actually going on right now in other parts of the Universe? No matter how close together, the real challenge of defining “now” simultaneously for two different spots in the Universe is that these points are always separated by a bit of distance. Since nothing can travel faster than light, it will always take a some time for an indicator that an event has “happened” to reach you.
So, on the small scale. If your friend 3 meters away from you says “Enterprise was a terrible show” right “now”, it will still take about 10 nanoseconds for the light of your friend to reach you. It will take about 8 milliseconds for the sound of your friend’s voice to reach you. Shortly thereafter you’ll decide to slap your friend, because seriously who needs that kind of negativity. You might say that is close enough to be the same “now”. As in “I slapped my friend just now, because he said something stupid”.
Betelgeuse, as seen by the Hubble Space Telescope.
For how our brains perceive time, and the relative length of our lifespans, you probably can get away with it, because sure, that’s “now”. We can consider a moment to occupy a span to encompass all these events. Although, you shouldn’t slap your friends. Even if they say mean things, and really didn’t give it a chance. You’re lucky your friend won’t have to wait too long to hear an apology from you as milliseconds after you say you’re sorry, they’ll hear you. Which, for our purposes, would be “right now”.
Over larger distances this doesn’t quite work as well. If you looked up in the sky and saw Betelgeuse become a supernova, would you argue that it is happening now? Some people might say yes. Until you know about an event, you can’t say it is happening. So, “Hey look, that star is going supernova right now” is what your brain might think. You received an indicator the event is beginning to happen, which for our purposes indicates it just started “now”.
Except, as one of our viewers, you’re way too smart for that. You would argue that since Betelgeuse is 640 light years away, the supernova actually happened 640 years ago, and it’s just taken that long for the light to reach us. We’re all good so far, as soon as I started talking about light years, you knew what was going on. It looks like it just happened now, but we’re aware that’s not the case. It happened before, we’re only aware it’s happening now.
Galaxy z8_GND_5296 (seen in the inset) is the earliest galaxy that astronomers have measured the distance to accurately. It formed approximately 700 million years after the Big Bang, and is forming stars at an incredibly rapid rate. [Credit: V. Tilvi (Texas A&M), S. Finkelstein (UT Austin), the CANDELS team, and HST/NASA]
Here is where it gets weird. The most distant galaxy yet discovered is z8 GND 5296. It’s 3.4 billion light years away. If we happened to observe a supernova in that distant galaxy, when would we say it happened? Obviously it’s not “just now”.
When the light we currently observe left that galaxy, it was about 3.4 billion light years away. So should we say it happened 3.4 billion years ago?Sure sounds reasonable based on our Betegeuse example. However, since our Universe has been expanding, it actually took the light 13.1 billion years to reach us. So we could say it happened 13.1 billion years ago.
Which one do we use? The real catch is that there is no cosmic definition of “now” in the Universe. Because of special relativity, the rate at which time flows for a particular object depends upon your point of view and your velocity. For a rocket travelling near the speed of light, a journey to Alpha Centauri might take a week. For us it would seem like 4 years. As a result of relativity, even the meaning of “simultaneous” is relative to your point of view.
The answer to what is happening now, is “it depends”. It depends on your frame of reference, and how flexible your attitudes about “now” are, what constitutes a moment, and quite probably how long lived your species is. I’m sure Jack Harkness and the nigh eternal Face Of Boe would give very different answers, well at least, depending on when you asked them.
The European Gaia spacecraft launched about a year ago with the ambitious goal of mapping one billion years in the Milky Way. That’s 1% of all the stars in our entire galaxy, which it will monitor about 70 times over its 5-year mission. If all goes well, we’ll learn an enormous amount about the structure, movements and evolution of the stars in our galaxy. It’ll even find half a million quasars. Continue reading “Astronomy Cast Ep. 365: Gaia”
Some times planets just head off into the mysterious Universe all on their own, without a star to orbit. How and why do planets go rogue like this?
We’re accustomed to thinking about solar systems as places of order. All the planets orbit their parent star, everything is neatly arranged in ellipses and rings. Even the asteroid belt has division lines of dry and icy. Planets do what they’re told: orbit that star until the end of time. No Pluto, you may not go outside and play with the other planets. You’ll spend your lunch hour in detention with Haumea until we decide what we’re going to do with you for not cleaning up your play area.
Some planets just can’t be held down. They’re the Jimmy Deans, the greasers, the Marlon Brandos, the Cool Hand Lukes. They break all the laws and play by their own set of rules. They’re a rolling stone, baby. To ask them to settle down would just be to deny their nature. So instead of orbiting a star, they go rogue and fly off into the Milky Way, possibly seeking fame, fortune and adventure, but keeping to the beat of their own drummer.
A rogue planet is any planet that doesn’t orbit a star. Instead of being a member of a solar system, it orbits the Milky Way on its own. Or in the case of really deviant planets, it’s been ejected out of the Milky Way entirely. Make no mistake, this is not a small condition affecting a few planets. It’s estimated that there are billions of rogue planets out there in the Milky Way.
How does this happen? How can we get rogue planets? Is it the way they were raised? Something that happened in the way they were born? Some rogue planets started out as part of a solar system, and then something happened. Some event “kicked” them out into deep space. You could get a collision or near miss with another star, or even a black hole. As two stars pass one another, their gravitational interactions can cause all kinds of mayhem to a nice orderly orbital system. Planets can be kicked into higher or lower orbits, smashed into stars or flung out with an escape velocity that means they’ll never orbit their star again.
Planets can also escape when their star disappears. Sounds impossible? Sometimes stars go out for cigarettes and just never come back. When a massive star detonates as a supernova, the force of the explosion can eject planets at tremendous velocities away from the former star, flinging those billiard balls all over the hall. But the vast majority of rogue planets probably formed early on in their solar systems. Things were rough and chaotic back then, with planets smashing into each other with all kinds of near misses. These interactions could bully out smaller neighbors with not so much as a nod. Jupiter, I’m looking at you.
This artist’s conception illustrates what a “hot jupiter” might look like.
It’s also possible that planets could form as orphans, within a solar nebula, away from a star entirely. If a pocket of hydrogen collects together into a sphere, but it doesn’t have enough mass to actually ignite as a star, it’s another type of rogue planet. We’ll just pretend these ones were raised by Nuns.
What would it be like for these planets? Without the light from a star, these would be incredibly cold places. This isn’t just sad metaphor. The outer layers, exposed to space would be as cold as interstellar space, just a handful of degrees above absolute zero.But deep down below the surface, there would still be leftover heat from their formation, so it’s possible that life could survive down there, kept alive within a warm cocoon.
And who knows, maybe after billions of years, a rogue planet could get captured by a star again, and thawed out. It might get a second chance, or it could all end tragically, racing for pinks along the Devil’s elbow out past the Pillars of Creation. There are many ways that planets can go rogue, in fact, it’s possible that there are more starless planets in the Milky Way than there are stars.
So what do you think? Should we set sail from the Sun, and seek out adventure in the Milky Way?
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I don’t want to freak you out, but you should be aware that there’s a gigantic galaxy with twice our mass headed right for us. Naw, I’m just kidding. I totally want to freak you out. The Andromeda galaxy is going to slam head first into the Milky Way like it doesn’t even have its eyes on the road.
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Transcript
I don’t want to freak you out, but you should be aware that there’s a gigantic galaxy with twice our mass headed right for us. Naw, I’m just kidding. I totally want to freak you out. The Andromeda galaxy is going to slam head first into the Milky Way like it doesn’t even have its eyes on the road.
This collision will tear the structure of our galaxy apart. The two galaxies will coalesce into a new, larger elliptical galaxy, and nothing will ever be the same again, including your insurance premiums. There’s absolutely nothing we can do about it. It’s like those “don’t text and drive commercials” where they stop time and people get out and have a conversation about their babies and make it clear that selfish murderous teenagers are really ruining everything for all of us all the time.
The Andromeda Galaxy will collide with the Milky Way in the future. Credit: Adam Evans
And now that we know disaster is inbound, all we can do is ask WHY? Why this is even happening? Isn’t the Universe expanding, with galaxies speeding away from us in all directions? Shouldn’t Andromeda be getting further away, and not closer? What the hay, man!
Here’s the thing, the vast majority of galaxies are travelling away from us at tremendous speed. This was the big discovery by Edwin Hubble in 1929. The further away a galaxy is, the faster it’s moving away from us. The most recent calculation by NASA in 2013 put this amount at 70.4 kilometers per second per megaparsec. At a billion light-years away, the expansion of the Universe is carrying galaxies away from us at 22,000 km/s, or about 7% of the speed of light. At 100 million light-years away, that speed is only 2,200 km/s.
Which actually doesn’t seem like all that much. Is that like Millenium Falcon fast or starship Enterprise Warp 10 fast? Andromeda is only 2.5 million light-years away. Which means that the expansion of the Universe is carrying it away at only 60 kilometers per second. This is clearly not fast enough for our purposes of not getting our living room stirred into the backyard pool. As the strength of gravity between the Milky Way and Andromeda is strong enough to overcome this expansive force. It’s like there’s an invisible gravity rope connecting the two galaxies together. Dragging us to our doom. Curse you, gravity doom rope!
The Hubble Space Telescope’s extreme close-up of M31, the Andromeda Galaxy. Picture released in January 2015. Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler
Andromeda is speeding towards us at 110 kilometers per second. Without the expansion of the Universe, I’m sure it would be faster and even more horrifying! It’s the same reason why the Solar System doesn’t get torn apart. The expansion rate of the Universe is infinitesimally small at a local level. It’s only when you reach hundreds of millions of light-years does the expansion take over from gravity.
You can imagine some sweet spot, where a galaxy is falling towards us exactly as fast as it’s being carried away by the expansion of the Universe. It would remain at roughly the same distance and then we can just be friends, and they don’t have to get all up in our biz. If Andromeda starts complaining about being friend-zoned, we’ll give them what-for and begin to re-evaluate our friendship with them, because seriously, no one has time for that.
The discovery of dark energy in 1998 has made this even more complicated. Not only is the Universe expanding, but the speed of expansion is accelerating. Eventually distant galaxies will be moving faster away from us than the speed of light. Only the local galaxies, tied together by gravity will remain visible in the sky, eventually all merging together. Everything else will fall over the cosmic horizon and be lost to us forever.
This annotated artist’s conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA
All things in the Universe are speeding away from us, it’s just that gravity is a much stronger force at local levels. This is why the Solar System holds together, and why Andromeda is moving towards us and in about 4 billion years or so, the Andromeda galaxy is going to slam into the Milky Way.
So, if by chance you only watched the first part of this video, freaked out, sold your possessions and joined some crazy silver jumpsuit doomsday cult, and are now, years later watching the conclusion… you may feel a bit foolish. However, I hope that you at least made some lifelong friendships and got to keep the jumpsuit.
Really, there’s nothing to worry about. Stars are spread so far apart that individual stars won’t actually collide with each other. Even if humanity is still around in another 4 billion years or so, which is when this will all go down. This definitely isn’t something we’ll be concerned with. It’s just like climate change. Best of luck future generations!
What do you think, will humans still be around in 4 billion years to enjoy watching the spectacle of the Milky Way and Andromeda collide?
You’ve probably heard the trope about how aliens have been watching old episodes of “I Love Lucy” and might think these are our “historical documents”. How far have our signals reached?
Television transmissions expand outward from the Earth at the speed of light, and there’s a trope in science fiction that aliens have learned everything about humans by watching our television shows. If you’re 4 light-years away, you’re see the light from the Earth as it looked 4 years ago, and some of that light includes television transmissions, as radio waves are just another form of electromagnetism – it’s all just light.
Humans began serious television service in the 1930s, and by the modern era, there were thousands of powerful transmitters pumping out electromagnetic radiation for all to see. So are aliens watching “I Love Lucy” or footage from World War II and believing it all to be part of our “Historical Documents”?
The first radio broadcasts started in the early 1900s. At the time I’m recording this video, it’s late 2014, so those transmissions have escaped into space 114 years ago. This means our transmissions have reached a sphere of stars with a radius of 114 light-years.
Are there other stars in that volume of space? Absolutely. It’s estimated that there are more than 14,000 stars within 100 light years of Earth. Most of those are tiny red dwarf stars, but there would be hundreds of sunlike stars.
As we’re discovering, almost all of those stars will have planets, many of which will be Earthlike. It’s almost certain some of those stars will have planets in the habitable zone, and could have evolved life forms, technology and television sets and were able to learn of the Stealth Haze and the Mak’Tar chant of strength.
Will the signals be powerful enough to stretch across the vast distances of space and reach another world so that many generations of aliens can hang their hopes that James Tiberius Kirk never visits their planet with his loose morals, questionably applied prime directive, irresistible charms and pants aflame with who knows what kinds of interstellar STIs?
Here’s the problem. Broadcast towers transmit their signals outward in a sphere, which falls under the inverse square law. The strength of the signal decreases massively over distance. By the time you’ve gone a few light years, the signal is almost non-existent.
The Square Kilometer Array
Aliens could build a huge receiver, like the square kilometer array being built right now, but the signals they could receive from Earth would be a billion billion billion times weaker. Very hard to pick out from the background radiation. And by Grabthar’s hammer, I assure you it’s only by focusing our transmissions and beaming them straight at another star do we stand a chance of alerting aliens of our presence. Which, like it or not, is something we’ve done. So there’s that.
We’ve really been broadcasting our existence for hundreds of millions of years. The very presence of oxygen in the atmosphere of the Earth would tell any alien with a good enough telescope that there’s life here. Aliens could tell when we invented fire, when we developed steam technology, and what kinds of cars we like to drive, just by looking at our atmosphere. So don’t worry about our transmissions, the jig is up.
What do you think? Is it a good idea to alert aliens to our presence? Should we get rid of all that oxygen in our atmosphere and keep a low profile?
![Galaxy z8_GND_5296 (seen in the inset) is the earliest galaxy that astronomers have measured the distance to accurately. It formed approximately 700 million years after the Big Bang, and is forming stars at an incredibly rapid rate. [Credit: V. Tilvi (Texas A&M), S. Finkelstein (UT Austin), the CANDELS team, and HST/NASA]](https://www.universetoday.com/wp-content/uploads/2013/10/high-z_galaxy.jpg)
