Monthly Archives: April 2010

Science Challenge 2010: What are the prospects of finding life on other planets?

This is an essay I wrote in response to the question “What are the prospects of finding life on other plantets?”. It was entered into the RCSU Science Challenge 2010, an essay competition hosted by Imperial College London, and was shortlisted for a prize.

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Since we stopped believing we were at the centre of the Universe, humans have looked up to the stars and wondered if they truly are alone. Some say it would be foolish, arrogant even, to say so, but we have no evidence to the contrary.

The Drake equation gives an estimate of the number of civilisations in the Universe with the ability to communicate with us. It starts with the rate of star formation and multiplies this by the fraction of stars that have planets, then the fraction of planets capable of supporting life and so on. Current estimates using this equation suggest that there should be at least a handful of other civilisations out there capable of communication. Not one has yet announced themselves. The contradiction between this high probability of intelligent life and our lack of contact with them is known as the Fermi Paradox. Over the years there have been numerous ways suggested to resolve this paradox, but none are as satisfying as we imagine contact with another civilisation would be.

So far, our attempts to communicate with other worlds have been in vain. Some say we’ve not been really been trying; mostly, we’ve been sitting tight and patiently waiting for someone to contact us. In fact, one solution to the Fermi paradox says that we have not made contact with other civilisations simply because everybody is listening for messages, but nobody is transmitting any. Even our attempts at active communication have been somewhat futile. For example, the Arecibo message, beamed to a star cluster known as M13 in 1974 will take 25,000 years to reach its destination. By this time M13 will be long gone. Maybe it’s time to put a bit more effort in.

Gliese 581d is an extrasolar planet orbiting a star in the constellation of Libra. It’s a super-Earth with a mass roughly eight times that of our planet, and it resides in the Goldilocks zone around its star; the zone which is not too hot or too cold, but just the right temperature for life. Scientists have studied this planet and found that it has an atmosphere just inside the parameters of being capable of supporting life. The Darwin Mission, deferred indefinitely in 2007, would have had the capacity to detect what mix of O3, H2O and CO2 is present in Gliese 581d’s atmosphere. If found in the correct proportions, these “biomarkers” would be the smoking gun of life; they would indicate that photosynthesis is occurring on the planet. If there was to be an interstellar mission, Gliese and its super-Earth would be first in line for exploration.

Let’s say that these biomarkers were found and an interstellar mission proposed. What next? Well, we’d need to work out a way to travel the 20.3 light years to the star system. While this is not a large distance on a cosmological scale, it would certainly pose us a serious challenge. Huge leaps forward in technology would be needed to reach speeds of only 10% of the speed of light. The method most likely to be capable of achieving these speeds in the future is nuclear pulse propulsion, i.e. using nuclear explosions to provide thrust. But even with this technology it would still take around 200 years to reach Gliese. Barring major medical advances in that time, the people who waved the rocket off on Earth would not even live to see it reach the halfway point! And let’s not forget the time delay in sending and receiving information from it.

So, 200 years. The best candidate for that sort of distance is a von Neumann probe, named after mathematician and physicist John von Neumann who studied self-replicating machines. The probe would use raw materials found along the way to make copies of itself, enabling it to travel vast distances to far away star systems without needing a vast payload.

The probe would also need a high level of artificial intelligence in order to look after itself, to monitor the world it encounters and to determine what actions to take as it goes along. For instance, if the culture found was deemed advanced enough to communicate with, the probe would need to make itself known and then speak on our behalf. If, however, communication was deemed dangerous, it would need to hide.

An interstellar mission is not yet a possibility for us, but it will be in the future. However, the Universe is a big place. Who’s to say that there isn’t another civilisation out there, who had a similar bright idea a good few years ago after monitoring the atmosphere of a promising looking planet orbiting a star quite a lot like our Sun? Maybe the prospects of finding life, or at least technology, from another world aren’t so dim after all…

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New images from NASA show the Sun in a whole new light

Last Wednesday, 21st April, NASA held a press conference to unveil the first images from its Solar Dynamics Observatory (SDO) mission. The mission is the first in NASA’s Living With a Star (LWS) Program, which is designed to investigate the variability of the Sun and how it can affect life on Earth. SDO’s specific goals are to find out more about the generation and structure of the Sun’s magnetic field, and how energy from this field is released into space as the solar wind and energetic particles.

Below is one of the first images revealed from the mission. It is a full disk, multiwavelength image taken by the SDO Atmospheric Imaging Assembly (AIA). The AIA looks at the lower atmosphere of the Sun in the extreme ultraviolet region of the electromagnetic spectrum, enabling it to see hot plasma moving along magnetic field lines. False colours show variations in temperature, with reds indicating temperatures of “only” 60,000 Kelvin, with blues and greens reaching higher than one million Kelvin.

Credit: NASA/Goddard/SDO AIA Team

 The yellowish ring shaped object in the top left hand corner of the picture above is known as a solar prominence. Another prominence spotted by SDO on 30th March can be seen below (and, if you like, you can watch a video of one here):

Credit: NASA/Goddard/SDO AIA Team

These prominences are large arches of dense gas that are attached to the Sun at the photosphere (where the light we receive on Earth originates from), and extend out into the corona (the Sun’s atmosphere). They appear to be very bright when viewed against the backdrop of space, but when seen on the disk of the Sun they appear dark and are known as filaments. This difference occurs because they are much cooler than the Sun’s surface, but when compared to the rest of space they are very, very hot.

Other interesting features can also be seen in pictures released last Wednesday. The picture below was taken by the Helioseismic and Magnetic Imager (HMI), and is a continuum image made up of pictures from several filters so that it closely resembles an optical image. A sunspot can be seen just above the centre of the image:

Credit: NASA/Goddard/SDO HMI Team

The magnetic field in a sunspot is very strong, and suppresses the transport of heat from the interior of the Sun to the surface, resulting in a cooler region that ends up looking dark as it is surrounded by much hotter material. Below is a picture taken at exactly the same time as the one above, but instead showing the Sun’s magnetic field:

Credit: NASA/Goddard/SDO HMI Team

The white areas in this picture have a positive magnetic field, black areas have a negative field and grey areas have zero magnetic field. It’s easy to see that the black and white region in this image corresponds to the sunspot in the previous image.

The mission was launched on 11th February this year, and is now fully operational, producing  high quality images that are ten times more clear than HD television. These images will give us invaluable information about solar variations that affect life and telecommunications here on Earth, as well as the astronauts and satellites orbiting us, and will hopefully eventually enable us to better forecast the “space weather” and provide early warnings when necessary.

For more information (and lots more pretty pictures!) see the SDO website: http://sdo.gsfc.nasa.gov/firstlight/

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One tiny push for some Beryllium ions, one big leap forward for Physics…

  

Researchers at the National Institute of Standards and Technology in Boulder, Colorado, have measured the smallest force ever – a few yoctonewtons. 

That’s 10-24N, a mind blowingly tiny number by anyone’s standards. It’s also several orders of magnitude smaller than the previous record, which stood at a comparatively huge attonewton (10-18N). This sizeable difference between the previous lowest measurement and the new one is due to the different materials used: old methods involved small wires and paddles, but this time researchers used something much, much smaller. 

The group were able to measure such a small force using a cluster of just 60 Beryllium ions. The ions weighed in at around 0.1 yoctokilograms themselves, and their size was key to being able to make such a tiny measurement. During the experiment the ions were held in a Penning trap, a device that holds charged particles in place using a combination of magnetic and electric fields. These traps are well suited to making precision measurements on groups of ions, in fact many of the highest precision mass measurements, including the mass of an electron and proton, come from Penning traps. They’re also good at storing other charged particles. Indeed, antiprotons at CERN are stored in Penning traps. 

Penning Trap

A Penning Trap: The electric field is shown in blue, and the magnetic field in red. An ion is shown, trapped in a vacuum at the centre of the trap.

 

An electric field was used to nudge the ions, as they remained held in the trap. The force on the ions during the push was measured indirectly, by shining a laser on the ions and looking at the change in the light when it was reflected back. 

The group think that by decreasing the number of ions they use, it would be possible to measure even smaller forces in the future. Small measurements using this method could be used to get some very precise measurements of fundamental forces, such as gravity, as well as imaging materials’ surfaces in greater detail than ever before. 

Paper available as a preprint at: arxiv.org/abs/1004.0780v2 

Image Credit: Arian Kriesch Akriesch

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