Did you know…?

Pluto New Horizons

New Horizons has provided our closest ever look at this fortunately found dwarf planet.
Credit: NASA, Johns Hopkins Univ./APL, Southwest Research Inst.

The planet Pluto was discovered because of a mistake.

In 1821 Alexis Bouvard published a table detailing the orbit of Uranus. Other astronomers quickly noted that there were some irregularities, and hypothesised the existence of another planet pulling Uranus out of line. After several more refined predictions, an approximate placement of the 8th planet was found. In 1846  Johann Gottfried Galle at the Berlin Observatory discovered Neptune, just where it was predicted to be.

It wasn’t long before tables of Neptune’s orbit were published and these appeared to show that they were being pulled out of whack by a 9th planet, dubbed Planet X, though the effect was much smaller.

In 1930 when Clyde Tombaugh discovered Pluto it was quickly touted as the famed 9th planet. However, fame soon turned to infamy. The planet was far too small to disrupt the orbit of the massive Neptune (1186km in diameter according to New Horizons).

Though the apparent perturbations have since been shown to be observational error, there are still people who hunt for Planet X (some believing it to be the harbinger of doom, or about to crash into Earth and kill us all). However he WISE infrared survey discounted the presence of a large body out to a distance of one light year, so its not looking likely for any killer planets.

Why is Venus so hot?

Venus, the second planet from our Sun is a hellish place. Despite being further away than Mercury, the planet is several hundred degrees hotter. At 735K (that’s 462ºC or 863F in old money) the air is hot enough to melt lead and once you start looking at the planet a bit more closely, the reason becomes clear.

Venus's thick atmosphere

Venus’s thick atmosphere prevents astronomers from seeing the planet’s surface. Credit: NASA

Venus’s has one heck of an atmosphere. The surface pressure is around 92 times that found on Earth and it’s made out of some pretty nasty stuff: 96.5% carbon dioxide, 3.5 nitrogen, laced with sulfur dioxide,  sulphric acid and a few other trace elements.

It’s no great secret that carbon dioxide is a green house gas – it lets light and heat in, but not out again. Venus is an example of what can happen if you let carbon dioxide build up in your atmosphere to ridiculous levels.

But what I always wondered was why does Venus have such a thick atmosphere in the first place? In most respects the planet is much like Earth. It’s slightly smaller, with around 80% of Earth’s mass, meaning its gravity is pretty much the same. It’s at 0.7 AU, one AU being the distance between the Earth and the Sun, so it’s not that much closer and from most observations seems to be pretty similar to the Earth. At first glance its warmer atmosphere and lower gravitational pull should mean atmospheric molecules are more likely to escape. So what the hell happened?

The surface of Venus

Using radar, scientists have managed to get a good idea of what Venus’s surface looks like. Credit: Venus

The answer is all to do with that magical substance that has defined the hunt for life in the Galaxy: water. Venus doesn’t have any, or at least not much. It has trace amounts in the atmosphere, around 20 parts per million, but compared to the 40,000 parts per million of water found in our atmosphere it’s practically nothing.

But it used to. As I said, Venus is very similar to Earth and almost certainly formed in much the same way. The Earth has water, as did Mars in the beginning for that matter. It stands to reason that Venus had its fair share too, though we don’t currently have any evidence as no Venusian lander has lasted longer than two hours on the surface.

At some point though the temperature on the planet reached a tipping point and it began to lose its oceans. The Sun has been warming at a rate of a few percent every billion years. On Earth this hasn’t appeared to have effected us too much, but Venus receives twice the energy from the Sun. The change in temperature was too much, eventually the oceans began to evaporate and as that happened, things began to go oh so terribly wrong.

Water’s of Venus

The evaporating water saturated the atmosphere. In the high atmospheric levels the Sun’s radiation started to break apart the water into hydrogen and oxygen. The light hydrogen floated away into the deep dark depths of space while the heavier oxygen does what oxygen always does, and reacted with absa-bloody-everything, most notably any carbon hanging around to create carbon dioxide.

Not only that but as the water evaporated the planet’s mantel began to dry out. Plate tectonics require liquid water to absorb minerals, act as a lubricant and so on. Without it, everything just seizes up, and that’s exactly what happened on Venus. Volcanic activity is another way that carbon dioxide gets sucked up and stored in rocks, being re-released when volcanoes do their thing.

All of this lead to rising carbon dioxide levels in the atmosphere, which caused the planet to begin heating causing the oceans to evapourate and eventually boil. To make matters even worse, water vapour is itself a green house gas, insulating a planet. Once the water began to be lost, Venus never stood a chance. On Earth the interaction between water, rock and carbon dioxide help to regulate our nice, temperate climate [1]. With this thrown out of kilter, everything went awry. The end result is a planet no one ever wants to go on holiday to.

Venus surface by Venera 13

The Russian Venera programme has sent several probes to Venus, including several landers. The missions were the first to land on another planet, but none lasted longer than two hours. However they did manage to send back several images of the planet surface, including this image taken by Venera 13. Credit: Roscosmos

[1] The Earth is pretty good at regulating its temperature. It does this through the interactions of volcanism, carbon dioxide and water. Volcanic activity is constantly catching and releasing carbon dioxide in the Earth’s crust. If the global temperature drops, water freezes, stopping it from absorbing carbon dioxide, which creates a green house effect, which heats the planet and melts the ice. Global temperatures get too high, the ice caps melt, the atmosphere becomes more humid and all that lovely liquid water sucks up the carbon dioxide and temperatures drop again. It should also be noted that while the planet is doing this, there are colossal civilisation ending, mass extinction educing storms and weather pattern shifts, which is why ‘global warming’ does not mean ‘a bit sunnier in the Summer’.

 

Did you know…

1994 Solar eclipse

The light of the corona is usually only visible on Earth during a total eclipse. It can be seen with specialist equipment though. Like a space telescope. Credit: Luc Viatour

The Sun’s corona, this aura of plasma that surrounds the main star, is many hundreds of times hotter than the photosphere, the surface that we see. While the temperature of the Sun’s surface is only 6,000K the corona can reach up to 1,000,000K.

All hail hypnothread. ALL HAIL.

Simulation of a cross section of a thread of solar material. All hail hypnothread. ALL HAIL.
Credits: NAOJ/Patrick Antolin

No one is 100% sure why this is, though the current leading theory is that it’s probably magnets… or rather that magnetic waves generated by the motions of matter inside the star. These oscillate through the Sun and cause the plasma in the corona to move in a turbulent motion (queue mesmerising gif to left) and the friction heats up the corona.

Exploring the Universe with the At-Bristol 3D Planetarium

Sitting under the dome of At-Bristol’s new 3D planetarium, I stared up at what looks like the night sky. There are a few stars I recognised but mostly there was familiar orange glow of light pollution circling the horizon. The presenter leading the show asked us all to close our eyes for a moment.

“Now,” she said. “Open your eyes.”

Credit: Tim Martin

Credit: Tim Martin

In front of my eyes was a sky covered in stars, the Milky Way streaking across the centre. For many people who lived in and around Bristol, this was the first true representation of a dark sky they had ever seen.

Credit: Tim Martin

Credit: Tim Martin

“There was one lady who came out of that show who was buying lots of astronomy books because she wanted to find out more,” said Lee Pullen, Planetarium Manager when I interviewed him later. “She confessed that she’d found the experience so emotional that she’d wept tears of joy in the show. Often people are just amazed. They had no idea there was so much out there to be able to find.”

The show in question was Summer Stargazing, a seasonal show highlighting the landmarks of the night sky at this time of year. We flew to distant stars, searched the sky for various asterisms like Cygnus and Lyra, though the highlight for me was taking a swooping journey through the rings of Saturn. The sight of ice particles jumping out of the screen all around me is something I won’t be forgetting.

An environmental perspective

The planetarium shows don’t just look up at the sky. Their environmental show, Blue Marvel, casts its gaze back downwards to our own fragile planet. Here the 3D really came into its own. The Earth became the canvas on which to paint humanities impact in a very tangible way. Deforestation was projected across the globe and oil consumption per capita jumped out from every country*. But perhaps the most striking moment was when the sea levels were made to rise 20m, flooding the world, including the place where I live.

The show was an excellent way to show the strain we humans are placing on the world, but also rather depressing. There was little indication of what we could do to prevent what seemed like the inevitable destiny of our civilisation.

Bristol is open to technology

But it is projects like this, beyond its main use as a planetarium, that the dome was upgraded for. The funding for the project came in part from the Bristol Is Open project.

“The Bristol Is Open Network is a high speed network that runs all around under Bristol,” says Seamus Foley, the planetarium’s media production officer. As part of this network the Planetarium goes by the moniker ‘the At-Bristol Data Dome’. “The idea is that in the future we might be able to stream 4K frames down the pipe in real time so you can have a supercomputer processing visualisations of molecular simulations, for example, and it turns up in the planetarium.”

The planetarium aims to be more than just a fancy screen for showing astronomy films, and the team are currently working at ways to make the dome earn its keep, including some intriguing ideas such as putting on music concerts and introducing interactivity.

At-Bristol Planetarium & Millennium Square

Credit: Tim Martin

“One of the experiments that we’ve done is dropping a buggy onto scans of the Tycho Crater and driving around it like a computer game,” says Foley. “We want to make it more than just a cinema experience. We want it to be an interactive and engaging, let people can take part and take control of the experience.”

Whatever comes next, I’m sure it will put the planetarium to its best use. I look forward to finding out what At-Bristol has in store.


* – Luxemburg was the real surprise here. It practically hit you in the head with it’s oil consumption the spike was so huge. Apparently it’s due to people nipping across the border to fill up on cheap petrol.

For those of you with a family At-Bristol is open most days between 10am-5pm on weekdays, and 10am – 6pm on weekends. They also regularly puts on After Hours and Planetarium Nights to allow adults to use the planetarium and have a look round.

 

From Russia with Rocks

On 15th February 2013 an explosion happened in the air above Chelyabinsk, Russia blowing out windows and doors for miles around. It was not, as many locals thought, a bomb going off but the shock wave created when a huge asteroid hit the earth’s atmosphere. News carriers around the world quickly picked up on the story, inviting experts to come and talk about the meteorite. Experts like me! I was contacted asking whether or not I’d like to go to Russia to film a documentary on the meteor. I, of course, said yes. After several manic days of trying to get visas and cold weather gear I was off.

It was great to be in the place where the meteor actually struck down.  It’s the first time something like this has happened and it’s been caught on camera. By looking at the footage scientists were quickly able to work out what direction the asteroid came from and how fast it was going. The best estimates put it somewhere around the 40,000mph mark.

Meteoroids are small particles of space rock, ranging from dust grains all the way up to kilometre sized asteroids. Meteoroids hit the Earth’s atmosphere all the time, around 50,000 tonnes of them a year. When this happens they, they become known as meteors. Most are small and burn up in the atmosphere, meaning they’re only dust when they reach the ground. By using stations across the globe designed to listen out for nuclear bombs, astronomers managed to work out how much energy the meteor created when it exploded, putting the size of the meteor at about 10,000 tonnes. Meteors of this size are thought to hit the planet once every 100 years or so. While it’s sad that so many people got hurt, it was really fortunate to have the event caught on so many cameras.

On the hunt

A quick explanation to camera before heading out into the snow fields to look for my rocks!

The day after we arrived we headed out into the countryside to ground zero: the spot directly underneath where the asteroid exploded. The fact that the area is covered in snow was actually a huge help to us meteorite hunters. I had to look for tiny holes in the snow, made by the meteorite as they showered from above. When you found a hole you had to dig around it, clearing a ring. Then I had to sift through the snow in the middle and hopefully find a meteorite. A lot of the holes were from mice or bits of tree but eventually me and the team got lucky and we found one! It was about the size of a jelly bean, covered in a black crust and felt really heavy.

Me and my Meteorite

Me with a 1kg meteorite found by the Urals Federal University.

We took the fragment to Urals Fedral University, where they were looking at the fragments already found. The discovered that the meteor was actually a rather average meteor, with about 7-10% iron, which was why the rock felt so heavy. I even got to look at a piece in a travelling electron microscope.

Despite the devastation that this meteor caused it was actually quite small, probably only 15m across, around the size of a house. The one that killed the dinosaurs was about 10km in size. Luckily those only happen every few million years and we’d probably see it coming. Projects like Pan-STARRS regularly scan the sky and can find nearly all asteroids that would risk wiping out all life on the planet. It hasn’t found any that are on a collision course with Earth, so there’s no need to worry. We’re not going the way of the dinosaurs anytime soon.

Meteor Strike: Fireball from Space is currently available on 4OD. If you haven’t seen it already, you might want to give it a look.

The Harvard Computers

The birth of the photographic plate was one of the most revolutionary moments in the history of astronomy. Before, an astronomer would have to spend long hours in the middle of the night, sitting in the cold at an often precariously placed eyepiece. Taking observations often took many hours and careful notation in less than ideal conditions.

The invention of the photograph had two different ramifications for astronomy. Firstly you could leave the plate there for hours, exposed to all the light of the night sky for as long as you could keep it steady. The human eye refreshes every 10 to 12 times a second, and so we can only see the light that falls on the eye in this time. With a plate you can leave it for 30 seconds, 5 minutes or all night if you can track what you’re looking at across the sky, gathering all the light falling on it in this time. This increase in light collection means that you can observe objects that are much dimmer than what can be seen with the human eye.

Secondly, once you have your photo taken and developed you can then take it away and look at it in the comfort of your office or study, in the middle of the day while sitting by the fire, which was much more cosy.

Williamina Fleming

Williamina Fleming

However there was a problem. The young male astronomers, usually PhD students and the like, didn’t think that sitting inside all day looking at photos was real astronomy. At Harvard College Observatory the men working under director Edward Charles Pickering moaned so much and did such a bad job that in 1881 he fired the lot of them, allegedly claiming that ‘his maid could do a better job’. True to his words, Prof. Pickering hired his maid, Williamina Fleming.

However, it transpired that Mrs Fleming was not just any ordinary maid. She was a highly intelligent and educated woman fallen on hard times after her husband abandoned her just when she was ready to give birth to their son. Initially she did simple tasks; clerical duties, copying and ‘computing’ i.e. maths [1]. However over time she began to take on more scientific and complicated tasks, such as looking at and analysing the spectrum produced by shining a star’s light through a prism.

Pickering quickly realised that not only was hiring women considerably cheaper than their male counterparts, they actually did a much better. For the price of one male astronomer Pickering could hire a dozen women, and they were soon known by the unflattering title of Pickering’s Harem, or the Harvard Computers. Together these women catalogued every single star observed in the sky, carefully measuring their colour, temperature, spectra and many other important properties. This was a feat that many thought impossible but after decades of hard work they completed the task. One of the group’s leaders, Annie Jump Cannon, cataloged and categorized over 350,000 stars in her lifetime, finding more stars in just four years than every male astronomer in history to the point put together [2].

The Harvard Computers

The Harvard Computers taken on 13th May 1913 . Back row, left to right: Margaret Harwood, Mollie O’Reilly, Prof. Pickering, Edith Gill, Annie Jump Cannon, Evelyn Leland, Florence Cushman, Marion Whyte, Grace Brooks. Front row: Arville Walker, Johanna Mackie, Alta Carpenter, Mabel Gill, Ida Woods. For more information look here.

The women were often paid less than the secretaries employed by the university and working in such a career was often seen as an admission of spinsterhood. All these women took this job for the love of astronomy and understanding. Many of these women went on to publish astronomical papers in their own right and many were the first women to be granted into the ranks of institutions such as the Royal Astronomical Society and the American Astronomical Society, and many are remembered on the moon having craters named after them. Henrietta Swan Leavitt, was even considered for a Nobel Prize in Physics for her work on Cephid variables that allowed astronomers to measure the enormous distances of the universe. Unfortunately she died before she could be officially nominated [3].

The work of the Harvard Computers was a huge leap forward not just in terms of astronomy but also for women in science. Though they themselves remain relatively unknown their work is still used by countless astronomers, both professionally and amateur, and will be for years to come.

[1] – Women of Science: Righting the Record by Gabriele Kass-Simon

[2] – Ladies of the Laboratory 2 by Lewis D. Eigen

[3] – Miss Leavitt’s Stars: The Untold Story of the Woman Who Discovered How To Measure The Universe by George Johnson

Did you know…?

The Square Kilometer Array (SKA), a radio telescope being built in both Australia and South Africa and expected to actually cover 5 square kilometres of ground, will produce enough raw data to fill 15 million 64GB iPods a day. That’s equivalent to every piece of information sent and received over the entire internet. Twice.

SKA antenna

An artists impression of what the SKA antenna will look like. Thousands of these 12m diameter dishes, split between the two sites, will cover the square kilometre.

But it’s alright. You don’t have to rush out and panic buy iPods. Most of that information doesn’t tell us anything and gets thrown out straight away. Working out what to lose and what to keep, however, is one of the most challenging aspects of any project as big as the SKA.

The Truth About Dust

When we astronomers talk about dust we don’t mean the type that you spend your life endlessly hoovering up (that’s mostly good old fashioned dirt). We mean cosmic dust, the stuff that is made in the space between stars and covers whole galaxies in huge clouds. It’s the stuff that gives birth to stars and planets. Every thing you ever touched or tasted or loved was once part of a massive cloud of dust floating out in space.

But what actually is this dust? I’ll be honest. We are not 100% sure but we’ve got a pretty good idea. The problem is we can’t just go out into space and grab a handful to look at in the lab. Voyager 1, the furthest man made object from the Earth, is only just leaving our solar system and it took 35 years to get there and won’t be coming back. Going on a jolly to pick up some dust isn’t looking likely. We can try and look at the dust that is in the solar system, and spacecraft like Ulysses and Cassini are doing just that, but it’s still not the same as going out and looking at all the lovely dust inbetween stars.

Sometimes we get lucky and we get hit by a meteorite. If you crack open a meteorite you might just get some stardust (and that is the technical term). It’s quite tricky to get out without destroying it, but we’ve managed to find that cosmic dust is mostly made up of stuff like graphite, silica carbide, aluminium oxide and other such fun things. When a star dies, either by going supernova or just wasting away to a white dwarf, it throws all the elements it made in its life out into the universe. All these atoms form something called the interstellar medium (astronomers call it the ISM, because we love our acronyms!). In the ISM the atoms come together to form dust grains, fractions of a millimeter long. How exactly they come together is still something we’re trying to work out.

These grains all hang out together in huge clouds that go right the way across entire galaxies. The problem is these clouds aren’t transparent, and this can cause a lot of issues if you’re an astronomer. Plonk a big cloud of dust in front of a star and it will soak up all the light from that star and block it from view. However, as it soaks up all that light the dust cloud is also soaking up all of the heat. Everything that has a temperature emits thermal radiation and you can see these clouds if you use giant, very fancy, very expensive heat cameras. With these cameras we can reclaim a lot of lost information as nearly half of all the light that shines from stars gets soaked up by dust clouds. If we didn’t look at the heat images of these clouds, all that information would be lost.

Andromeda Galaxy

The Andromeda galaxy is the closest galaxy that resembles the Milky Way and so has long fascinated astronomers. The top image shows the visible image, so if your eyes were giant telescopes this is what you would see. Throughout you can see dark bands, where dust lanes are blocking out the star light. The lower images is in the infrared, so shows the heat pattern, with the bands of dust glowing brightly. If you look carefully you can see that the dark patches in the optical match up with the bright lanes in the infrared. (Visible: Kitt Peak National Observatory, Infrared: Spitzer, Image: HubbleSite)

This dust isn’t just acting like a giant rain cloud blocking out the starlight. It’s really important to the growth and life cycle of stars and galaxies. Dust is made from dead stars but it’s in these huge clouds, or nebula, that new stars get born. Our own sun was born from the remains of other stars that died millions of years before, as were all the planets including the Earth and everything on it. As Carl Sagan said ‘we are all made of star stuff’. The next time you’re doing the hoovering spare a thought for the dust, because once that dust was cosmic and lived in the space between the stars.