Have you ever wondered what it’s like to visit one of the big research observatories, like Keck, Gemini, or the European Southern Observatory? What’s it like to use gear that powerful? What’s the facility like? What precautions do you need to take when observing at such a high altitude?
We record Astronomy Cast as a live Google+ Hangout on Air every Monday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
This question comes from Andrew Bumford and Steven Stormont.
In a previous episode I’ve talked about how the entire Solar System collapsed down from a cloud of hydrogen and helium left over from the Big Bang. And yet, we stand here on planet Earth, with all its water. So, how did that H20 get to our planet? The hydrogen came from the solar nebula, but where did the oxygen come from?
Here’s the amazing part.
The oxygen came from stars that lived and died before our Sun was even born. When those stars puffed out their final breaths of oxygen, carbon and other “metals”, they seeded new nebulae with the raw material for new worlds. We owe our very existence to the dead stars that came before.
When our Sun dies, it’ll give up some of its heavier elements to the next generation of stars. So, mix hydrogen together with this donated oxygen, and you’ll get H20. It doesn’t take any special process or encouragement, when those two elements come together, water is the result.
But how did it get from being spread across the early Solar System to concentrating here on Earth, and filling up our oceans, lakes and rivers? The exact mechanism is a mystery. Astronomers don’t know for sure, but there are a few theories:
Idea #1: impacts. Take a look at the craters on the Moon and you’ll see that the Solar System was a busy place, long ago. Approximately 3.8 to 4.1 billion years ago was the Late Heavy Bombardment period, when the entire inner Solar System was pummeled by asteroids. The surfaces of the planets and their moons were heated to molten slag because of the non-stop impacts. These impactors could have been comets or asteroids.
Comets are 80% water, and would deliver vast amounts of water to Earth, but they’re also volatile, and would have a difficult time surviving the harsh radiation of the young Sun. Asteroids have a lower ratio of water, but they could protect that water a little better, delivering less with each catastrophic impact.
A false-color, visible-light image of Comet ISON taken with Hubble’s Wide Field Camera 3. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Astronomers have also found many hybrid objects which contain large amounts of both rock and water. It’s hard to classify them either way.
Idea #2 is that large amounts of water just came directly from the solar nebula. As we orbited around the young Sun, it passed through the water-rich material in the nebula and scooped it up. Gravitational interactions between the planets would have transferred material around the Solar System, and it would have added to the Earth’s volume of water over hundreds of millions of years.
Of course, it’s entirely possible that the answer is “all of the above”. Asteroids and comets and the early solar nebula all delivered water to the Earth. Where did the Earth’s water come from? Astronomers don’t know for sure. But I’m sure glad the water is here; life here wouldn’t exist without it.
We’ve got a pretty bright Moon, but that just means we’ve got another target for the Virtual Star Party.
Tonight we had beautiful views of the Moon from David Dickinson and Cory Schmitz, and then some deep sky objects from Gary Gonella and Cory. We saw Andromeda Galaxy, Bubble Nebula, Swan Nebula, Lagoon Nebula, Dumbbell Nebula. And some viewers shared their photographs, including some amazing images of the International Space Station.
Host: Fraser Cain
Astronomers: Cory Schmitz, Gary Gonella, David Dickinson
We hold the Virtual Star Party every Sunday night as a live Google+ Hangout on Air. We begin the show when it gets dark on the West Coast. If you want to get a notification, make sure you circle the Virtual Star Party on Google+. You can watch on our YouTube channel or here on Universe Today.
After last week’s non-episode, the Weekly Space Hangout roared back to life. We had big news on the Government Shutdown, the Earth flyby from the Juno spacecraft, and a big update on Comet ISON.
We also had a special guest, author and journalist Lee Billings, who was here to talk about his newest book, Five Billion Years of Solitude. Lee talked about his work on the book, and the state of extrasolar planet research in general.
Here was the team:
Host: Fraser Cain
Panel: Casey Dreier, Nancy Atkinson, Amy Shira Teitel, Jason Major, and David Dickinson
We broadcast the Weekly Space Hangout every Friday afternoon as a Google+ Hangout on Air. You can watch us live on Google+, or on YouTube, or right here on Universe Today. We start at 12:00 pm Pacific / 3:00 pm Eastern.
Almost every part of a rocket is destroyed during the launch and re-entry into the Earth’s atmosphere. This makes spaceflight really expensive. Rocket delivery of even a single kilogram into orbit costs tens of thousands of dollars. But what if we could just place our payloads directly into orbit, and didn’t need a rocket at all?
This is the idea of a space elevator, first envisioned by the Russian rocket scientist Konstantin Tsiolkovsky in 1895. Tsiolkovsky suggested building a tower all the way up to geostationary orbit, this is the point where a satellite appears to hang motionless in the sky above the Earth. If you could carry spacecraft all the way up to the top, and release them from that tower they’d be in orbit, without the expense of a discarded rocket. A fraction more energy and they’d be traveling away from the Earth to explore the Solar System.
The major flaw with this idea is that the entire weight of the tower would be compressing down on every part below. And there’s no material on Earth, or in the Universe, that can handle this kind of compressive force. But the idea still makes sense.
Newer thinking about space elevators propose using a cable, stretched out beyond geostationary orbit. Here the outward centripetal force counters the force of gravity, keeping the tether perfectly balanced. But now we’re dealing with the tensile strength of a cable tens of thousands of kilometers long.
Imagine the powerful forces trying to tear it apart. Until recently, there was no material strong enough to withstand those forces, but the development of carbon nanotubes has made the idea more possible.
How would you build a space elevator? The most reasonable idea would be to move an asteroid into geostationary orbit – this is your counterbalance. A cable would then be manufactured on the asteroid, and lowered down towards the Earth.
As the cable extends down, the asteroid is orbited further from the Earth, keeping everything in balance. Finally, the cable reaches the Earth’s surface and is attached to a ground station.
Artists concept of a space elevator. Credit: Caltech
Solar powered machines are attached to the space elevator and climb up from the surface of the Earth, all the way to geostationary orbit. Even traveling at a speed of 200 km/hour, it would take the climber almost 10 days to make the journey from the surface to an altitude of 36,000 kilometers. But the cost savings would be dramatic.
Currently, rockets cost about $25,000 per kilogram to send a payload to geostationary orbit. A space elevator could deliver the same payload for $200 per kilo.
Obviously there are risks associated with a megastructure like this. If the cable breaks, portions of it would fall to Earth, and humans traveling up in the elevator would be exposed to damaging radiation in the Earth’s Van Allen belts.
Building a space elevator from Earth is at the very limits of our technology. But there are places in the Solar System which might make much more useful places to build elevators.
The Moon, for example, has a fraction of the Earth’s gravity, so an elevator could operate there using commercially available materials. Mars might be another great place for a space elevator.
Whatever happens, the idea is intriguing. And if anyone does build a space elevator, they will open up the exploration of the Solar System in ways that we can’t even imagine.
I finally caught up with the rest of the space journalist community and watched the new Gravity movie last night.
I absolutely loved it. It was by far the best movie I’ve seen this year, and I think one of the best space movies ever made.
The attention to detail on so many aspects of spaceflight was heartening: the cramped conditions of the space station, the perspective of the Earth, the lack of sound, the realistic physics (mostly).
WARNING – Spoilers Ahead
I believe that good art benefits from constraints. And in this case, director Alfonso Cuarón gave himself the constraint of a realistic portrayal of space, and it paid off in so many ways.
Except when he didn’t. There are a pile of unscientific moments that happen in the movie, that I think could have been easily fixed in the script stage.
It would have been amazing to hear Phil Plait or Neil deGrasse Tyson scratching their heads, unable to find a single scientific flaw.
So let’s fix Gravity
I’ll go first.
Remember I said spoilers? Here come the spoilers.
Stone can’t hold on to Kowalski and he’s forced to detach himself – As it was portrayed in the movie, and noted by Phil, he had no force pulling him away from Stone, so she should have been able to easily tug him back. But if the station was rotating quickly enough, there would be outward centripetal force.
People have speculated on the internet that it was rotating, and the background stars are shifting. But if that was the case, loose ropes and cables would be extending out from the station. And things wouldn’t have been floating so freely inside the station.
Solution:
As the astronauts are approaching the ISS, they noticed that the first Soyuz had already been used to abandon the station – what if they gave the station a kick as they departed in a rush? So maybe Kowalski could have noticed that the station was spinning. And the mess of parachute lines would have been taut, reflecting that.
That would have made hanging onto the lines more difficult, and would have been enough force to tear Kowalski away.
Your turn. What was a problem in the story, and how could it have been fixed without seriously ruining the movie?
I posted this topic over on Google+ and got some great suggestions for topics:
How could you get a debris cascade going so quickly?
Shouldn’t airlocks open inward?
Why did a fire start at the exact moment Stone gets on board ISS?
How could you get from Hubble to ISS to Tiangong? They’re on different orbital trajectories?
Why would communications satellites get taken out? They’re at a much higher altitude.
Why wasn’t Stone wearing traditional astronaut undergarments and, uh, a diaper?
Why didn’t Stone’s hair float in microgravity?
What scientific inconsistencies did you see, and how would you fix them?
Ask anyone, “what color is the Sun”? and they’ll tell you the obvious answer: it’s yellow.
But is it really?
Please don’t go check, it’s not safe to look directly at the Sun with your unprotected eyes.
From our perspective it does look a little yellow, especially after sunrise or shortly before sunset,
But don’t be fooled.
If you could travel into space and look at the Sun without going blind, you’d find that it’s actually white, and not yellow.
Using a prism, you can see how sunlight can be broken up into the spectrum of its colors: red, orange, yellow, green, blue, indigo and violet. When you mix all those colors together, you get white.
Here’s the strange part.
If look at all the photons coming in, our star is actually sending the most photons in the green portion of the spectrum,
Our Sun appears yellow to us because of the atmosphere.
Photons in the higher end of the spectrum – blue, indigo and violet – are more likely to be scattered away, while the lower end of the spectrum – red, orange and yellow – are less easily scattered.
Credit: Niki GaidaWhen the Sun is close to the horizon, you’re seeing it distorted by more of the Earth’s atmosphere, scattering away the bluer photons and making it appear red.
When there’s smoke and pollution in the air, it enhances the effect and it will look even redder.
If the Sun is high in the sky, where it has the least amount of atmospheric interference, it will appear more blue.
The Sun. Credit and copyright: César Cantú.We’re so familiar with the Sun being yellowish-orange, that astronomers will artificially change the color of their images to look more yellowy.
But really, the Sun looks like a pure white ball – especially when you’re out in space.
Interestingly, the color of the Sun is very important to astronomers. They use a technique called spectroscopy to stretch out the spectrum of light coming from a star. Dark lines in this spectrum tell you exactly what it’s made of.
You can see which stars have high amounts of metals, or which are mostly hydrogen and helium, leftover from the Big Bang.
This color also tells you the temperature of the star. Cooler stars are actually redder. Betelgeuse is only 3500 Kelvin. Hotter stars, like Rigel, can get above 10000 Kelvin, and they look blue.
Our own Sun has a temperature of almost 5800 Kelvin, and when viewed outside of our atmosphere, appears white. in colour.
Sometimes you can do science by watching patiently, and sometimes you’ve just got to get your hands dirty with an experiment or two. These two methods have their advantages and disadvantages for revealing Nature’s secrets. Let’s talk about how and why scientists choose which path to go down.
We record Astronomy Cast as a live Google+ Hangout on Air every Monday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
Another wonderful Virtual Star Party, this time with 6 astronomers broadcasting their view of the night sky live. We had amazing views of Saturn, the Ring Nebula, M27, and M17 the Swan Nebula (also known as the Lobster or Horseshoe Nebula). We also caught great views of NGC-896, NGC-869, and the M56 Cluster. Then we got some beautiful views of the Veil Nebula and discussed the benefits of image-stabilized binoculars.
This was also the first time were joined by Scott Ferguson, who delighted us with his dark sky views from the west coast of Florida. His views of the Pelican Nebula (NGC-6996) were gorgeous and unique. Continue reading “Virtual Star Party – October 6, 2013”
Everyone knows that the Moon goes through phases, but let’s talk about why it does. It comes down to illumination, which in this case, all originates from our nearby star.
Our Moon orbits around our planet, and this Earth-Moon system orbits around the Sun.
Even though we only see light on part of the Moon, from the perspective of the Sun, half of it is always illuminated.
Stuck here on Earth, we see the Moon in various phases of illumination as it completes a 27.3 day orbit around the Earth.
As The Moon travels around us we see it pass through its phases. It goes from New Moon, to Full Moon and back to new Moon again.
Crescent Moons are when it’s less than half illuminated, and gibbous when it’s more than half.
“Waxing” means that the Moon becomes more illuminated night-by-night, and the term “waning” means that it’s getting less illuminated each night.
New Moon – When the illuminated side of the Moon is away from the Earth. The Moon and the Sun are lined up on the same side of the Earth, so we can only see the shadowed side. This is also the time that you can experience solar eclipses, when the Moon passes directly in front of the Sun and casts a shadow onto the surface of the Earth. During a new moon, we can also see the reflected light from the Earth, since no sunlight is falling on the Moon – this is known as earthshine.
Crescent – The crescent moon is the first sliver of the Moon that we can see. From the northern hemisphere, the crescent moon has the illuminated edge of the Moon on the right. This situation is reversed for the southern hemisphere.
First Quarter – Although it’s called a quarter moon, we actually see this phase when the Moon is half illuminated. This means that the Sun and the Moon make a 90-degree angle compared to the Earth.
Waxing Gibbous – This phase of the Moon occurs when the Moon is more illuminated that half, but it’s not yet a full Moon.
Full Moon – This is the phase when the Moon is brightest in the sky. From our perspective here on Earth, the Moon is fully illuminated by the light of the Sun. This is also the time of the lunar month when you can see lunar eclipses – these occur when the Moon passes through the shadow of the Earth.
Waning Gibbous – In this lunar phase, the Moon is less than fully illuminated, but more than half.
Last Quarter – At this point of the lunar cycle, the Moon has reached half illumination. Now it’s the left-hand side of the Moon that’s illuminated, and the right-hand side in darkness (from a northern hemisphere perspective).
Crescent – This is the final sliver of illuminated moon we can see before the Moon goes into darkness again.
If you ever get the chance to travel to the other hemisphere, you’ll immediately notice how unfamiliar the Moon behaves – it’s upside down.
If you live in the Northern Hemisphere, after a New Moon the crescent begins on the right-side. But if you’re in the Southern Hemisphere, it’s reversed, with the illumination starting on the left side.
Weird.
The alignment of the Sun, Earth and Moon can lead to some fantastic astronomical events.
When the Moon is new, it can pass in between the Earth and the Sun, casting its shadow down on our planet. As you know, a solar eclipse.
Solar Eclipse as seen by Hinode SatelliteYou’d think we would see a solar and lunar eclipse every month, but we don’t because the Moon’s orbit is inclined relative to the Sun.
Most months, the Moon is either above or below the Sun in the sky, so they just don’t line up perfectly.
Phases of Venus. Image credit: ESOOne more thing, you might not know that Venus also goes through phases. When the planet is on the other side of the Sun from us, we see it as a nearly complete disk. But when Venus is on our side, just about to pass into the glow of the Sun, it’s a thin crescent, just like how we see the Moon.
I hope this gives you a better understanding of why the Moon goes through its phases every month, and the interesting relationship between the Earth, the Sun, and the Moon.
