Megan's Blog

Seven billion elephants

In February last year I posted about sustainability and the growing global population as part of the month-long Global Population Speak Out initiative. In the year since I last posted on the topic, the Earth has gained another 80 million people. Can you imagine that many human beings? I certainly can't.

My last post on the subject was titled "The elephant in the room" following John Feeney's article in the BBC's Green Room - it's a topic of huge importance to the sustainability of our world, but one that is frequently ignored or glossed over. The human population currently grows by about 80 million annually, right now there are more than 6.7 billion of us on this one tiny planet. Can you imagine if there were 6.7 billion elephants? Mankind would probably call it an infestation and start a cull.

One common objection to the assertion that we're heading for overpopulation is that we need a growing population to sustain the economy. This is probably a more common argument since the financial crisis, but think about it for a moment. An economy such as we currently have does require a growing population because it's designed that way, but that doesn't mean it can go on forever. Infinite growth in a closed system just cannot happen. We live on a single planet with a finite amount of land and a limited set of resources. Those resources must sustain not only us, but the rest of the ecosystem on which we fundamentally depend.

Sitting in an air-conditioned office or a heated home, the modern western world can make us feel quite disconnected from the rest of the biosphere, but we are still a part of it. What we do affects the environment around us, the decisions we make affect more than just ourselves. Whether we like it or not, we are part of that ecosystem and it simply can not sustain infinite growth. Ecology tells us this. Physics tells us this. Continued economic growth is simply unsustainable. It cannot continue indefinitely on a finite planet.

February once again sees a global effort to bring the topic into open debate. Population has been a very political topic here in Australia for various reasons - there is a big push to increase the skills base by encouraging the immigration of skilled workers, but there is also an ongoing debate as to how much population growth is physically sustainable both in terms of the economy and general infrastructure. This year, Australian MP Kelvin Thomson has added his voice to the GPSO effort, giving a speech at a public meeting of Sustainable Population Australia in Canberra on February 10th. Last October, PM Kevin Rudd sounded his approval of population growth and his allegiance to a “big Australia.” The political backlash was significant. In the meantime, Thomson released a plan for stabilizing Australia’s population at 26 million by 2050, and a new political party is reportedly being formed by an entrepreneur from Sydney - specifically to address population concerns in Australia. It will be interesting to see how the debate progresses over the next twelve months.

It's a big subject. Check out the resources and contributions at the GPSO website and join the debate.

The aftermath

Update 10th Feb: The Darker Projects team have produced a rather excellent audio drama version of Silver Spiral that you can download here.

Well. What a strange week. I am honestly stunned by the reaction to the Doctor Who story, it's amazing how many people have read, commented on and linked to it. It's turned up in some odd places too - I find it quite astounding that the original Skymania article about the story was posted on the Scientific American website! It's been linked to by Gallifrey Base (currently it's the only post that shows up under their "science" tag), io9, Kasterborous, it was picked as an Editor's Selection by Dr SkySkull on Research Blogging, someone made an entry for it in the Doctor Who wiki (although I doubt it will stay there), and it even turned up in the Big Finish forum. Wow. Even the audio version seemed to go down well, although I'm very much looking forward hearing to the Darker Projects version of it with David Ault as the Doctor (the next best thing to having David Tennant and Freema Agyeman read it!).

Not all the feedback was positive, but it was at least mostly constructive. One comment was that the formatting made it hard to read, so apologies for that. Several people also pointed out that there had been sharks in the oceans for a while by 35 million years BC (what's a decimal point between friends?). Ooops, entirely my fault. I could say that I'm an astronomer, not a palaeontologist, but that's a cop out as I was trying to be at least slightly educational. There's no excuse. Sorry.

Several people objected to the lack of knowledge and the incredulous tone that I gave Martha. She sounds that way because I needed her to! It's intended as an early Martha story, before she's got used to the whole idea of being able to go any place and any time, so I think the tone is justified. As for her lack of physics knowledge, well, her character is clever (I'm not disputing that), but she's a medic not a physicist. I knew quite a few medics at uni, and a generally bright bunch they were, but they couldn't tell you the first thing about how the Sun worked. I couldn't name the bones of the hand without looking them up - I may be a Dr, but I'm not that sort of doctor.

But, most of the comments were very positive, and a very big thank you to everyone who gave me feedback (good or bad). I wrote it for a bit of fun, with the hope that it might be slightly educational, and it seems to have done what I hoped it would and reached a far larger audience than I ever expected. I'd really love to see a bit more actual science in Doctor Who since, as has also been noted by several of those who commented, the original concept for the show was to have an educational aspect to it. I doubt anyone from the Beeb will ever read this but, just in case: come on guys, it's not hard! That child-like excitement you see in the character when there's something new or unusual: that's exactly what it feels like to be a scientist!

It's years since I wrote anything fictional, but I think I will try doing it more often after the reaction this one had. There's plenty more science to go at, and there will be a more substantial story behind it next time...

In the news this month: trees on Mars?

And finally: The HiRISE instrument on board the Mars Reconnaissance Orbiter has been taking spectacular images since the probe entered orbit around the planet in 2006. One particular image, posted to Astronomy Picture of the Day on January 19th, caused something of a stir.

The image shows a series of pinkish-coloured sand dunes covered with a light frost, located near the North pole of Mars, taken on the 7th of April 2008 during the Martian spring. As the Sun started to melt the carbon dioxide ice, the sand started to shift, cascading down the dunes in dark streaks which look uncannily like trees in the image taken by the HiRISE instrument on board the orbiter. The image covers an area of roughly one square kilometre and resolves objects as small as 25 cm. The colour variations in the ice around the streaks are thought to be caused by dust kicked up as the material shifts and settles on the surface.

In the news this month: the coolest brown dwarf yet

An international team, led by astronomers at the University of Hertfordshire have discovered what may be the coolest sub-stellar body ever found outside our own solar system. Using the United Kingdom Infrared Telescope (UKIRT) in Hawaii, the astronomers have discovered a type of object known as a brown dwarf, smaller than other stars but larger than gas giant planets such as Jupiter. The object, known as SDSS1416+13B, is only visible in infra-red light and is in a wide orbit around a somewhat brighter and warmer brown dwarf known as SDSS1416+13A. This discovery is "the fourth time in three years that UKIRT has made a record breaking discovery of the coolest known brown dwarf, with an estimated temperature not far above 200 degrees Celsius," said the University of Hertfordshire's Dr Philip Lucas.

The light detected from the star is rather unusual, it appears far bluer at near infra-red wavelengths than any other brown dwarf detected so far. A near infrared spectrum, taken with the Japanese Subaru Telescope in Hawaii, showed that it belongs to a class of objects known as T dwarfs, and that is has a lot of methane in its atmosphere but with peculiar features including a big gap at certain wavelengths. Using the Spitzer space telescope to measure its colour at mid-infrared wavelengths,the researchers found that it is also the reddest known brown dwarf at these wavelengths by some margin. A comparison with theoretical models of brown dwarf atmospheres results in a temperature estimate of just 500 Kelvin or 227 degrees Celsius. In comparison, our own Sun has a surface temperature of approximately 6000 Kelvin. Both stars are also lacking in heavy elements, an indication that they may be very old which fits in with the low temperature of the fainter star - fainter stars use up their fuel much slower and can last for many billions of years.

The research has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.

---

Ben Burningham, S. K. Leggett, P. W. Lucas, D. J. Pinfield, R. L. Smart, A. C. Day-Jones, H. R. A. Jones, D. Murray, E. Nickson, M. Tamura, Z. Zhang, N. Lodieu, C. G. Tinney, & M. R. Zapatero Osorio (2010). The discovery of a very cool binary system MNRAS arXiv: 1001.4393v1

In the news this month: coronal loops imaged around another star

Most of our knowledge of the processes and morphology of stellar coronae comes from observing our nearest star, the Sun. Coronal loops are associated with sunspot groups which affect the streams of charged particles leaving the Sun as the solar wind, so an understanding of the processes in these loops has implications for space weather predictions which can impact on satellite operations and the safety of astronauts.Studying the same processes in other stars is difficult due to the distances involved and the high resolution required to see any detail. Some of the highest resolution observations possible in astronomy are made using arrays of radio telescopes linked together in a process known as very long baseline interferometry; the more widely separated the telescopes in the array, the higher the resolution of the final images.Using this technique, a team led by William Peterson, a graduate student at the University of Iowa, have detected a large coronal loop on another star.

Using a very sensitive array of radio telescopes which included the ten antennas of the Very Long Baseline Array in the US, the 100-m Green Bank Telescope in West Virginia, the Very Large Array in New Mexico and the 100-m Effelsberg telescope in Germany, the astronomers imaged the variable star Algol in Perseus. Algol is an eclipsing binary system consisting of a large main sequence B-class star and a cooler K-class sub-giant in orbit around each other. The two stars are very close, just 6% of the distance between the Earth and our own Sun, and orbit each other every 2.86 days. The results show a gigantic coronal loop stretching out from the surface of Algol B, the K-class sub-giant star, towards its companion Algol A, with the two ends of the loop located at the magnetic poles of the sub-giant star. Throughout the orbit, this loop continues to point towards Algol A.

The researchers say that Algol B's coronal loop is similar to those seen on the Sun, but is much larger, and the magnetic field at Algol is about 1,000 times more powerful. The size of the coronal loop is larger than predicted by stellar models, and the suggestion is that this is probably due to the tidal effects of the companion star distorting the loop and stretching it.

The results, the first time a coronal loop has been imaged on another star, were published in the journal Nature on February 14th.

---

Peterson, W., Mutel, R., Güdel, M., & Goss, W. (2010). A large coronal loop in the Algol system Nature, 463 (7278), 207-209 DOI: 10.1038/nature08643

In the news this month: Chandra tells tails of extragalactic star formation

Star formation is usually thought of as occurring mainly in the spiral arms of galaxies. In close encounters or collisions between galaxies, the orbits of these stars around the galactic disk can be disrupted, resulting in some stars being thrown out into intergalactic space. But new results from the Chandra X-ray Observatory suggest that, at least in some cases, stars can form outside the normal boundaries of galactic disks.

A team led by Ming Sun at the University of Virginia used the orbiting Chandra telescope to observe galaxies in a nearby rich cluster known as Abell 3627. What they found were several enormous tails of X-ray emission, trailing behind galaxies located in the cluster. Tails like these are made up of X-ray emitting gas which is stripped from a galaxy as it moves through the cluster. One of these galaxies, ESO 137-001, was already known to have one X-ray tail which extends approximately 260 thousand light years from the galaxy itself, but in these observations the team found a second tail apparently associated with the same galaxy. This new tail is of a similar length to the first, but is both fainter and narrower. Both the widths and temperatures of the tails remain surprisingly constant over their entire lengths, and these properties present challenges to current models and simulations of such systems. A similar tail of about half the length was also detected behind ESO 137-002, another similar galaxy in the same cluster.

Together with observations using telescopes operating in other parts of the electromagnetic spectrum, the research also shows the first unambiguous evidence of star formation in the material stripped from a galaxy. Rather than forming in the galactic disk as normal, these stars are forming in the gas stripped from the disk as the galaxy moves through the tenuous gas in the cluster.

X-ray tails are rare, and double-tails are extremely rare, so one question is, why should there be two bright X-ray tails visible in the same cluster? In their paper, published in the Astrophysical Journal, the researchers suggest that (aside from coincidence) the high ambient pressure in this particular cluster could play a role, making the X-ray tails denser and more luminous. If this is the case, the high pressure environment would also be helping the process of extra-galactic star formation.

---

Sun, M., Donahue, M., Roediger, E., Nulsen, P., Voit, G., Sarazin, C., Forman, W., & Jones, C. (2010). SPECTACULAR X-RAY TAILS, INTRACLUSTER STAR FORMATION, AND ULXs IN A3627 The Astrophysical Journal, 708 (2), 946-964 DOI: 10.1088/0004-637X/708/2/946