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Tuesday 28 January 2014

TWDK past, present and future

At this time of year, it's customary for a company to reflect on what it has (or hasn't) achieved over the past year, and to plan out how it wants to move forward for the next twelve months. 2013 was indeed a special year for Things We Don't Know, as it was the first full year in which we existed! We're certainly very proud of everything we've achieved so far.

In 2012, our highest monthly visitor count to our articles was just under 2,500 (November). In October 2013, saw more than three times as many visitors. That's still a low number compared to what we want to achieve, but for a website that doesn't advertise anywhere (yet) we're rather happy with that.

Of course, our published articles are just the tip of the iceberg - we've been busy doing a lot more behind the scenes.
TWDK founder Ed Trollope on stage in Berlin
TWDK founder Ed Trollope, presenting his vision on stage in Berlin. Photograph by Gerhard F. Ludwig

Thursday 16 January 2014

The six-tailed comet, and other mysteries

Comets are one of the spectacles of the solar system and some only pass by in view of the Earth every few thousand years (Comet Hale-Bopp is only in view of Earth every 2,500 years). At the end of 2013, astronomers observed the marvels of both Comet ISON and a “pseudo” comet with six tails! On Monday, ESA's Rosetta mission will wake from hibernation to continue its mission to orbit and land on a comet. This week, TWDK's physics editor Cait has interviewed Nick Howes, the Pro-Am Programme Manager for the Faulkes Telescopes in Hawaii and Australia. Nick is also an active amateur astronomer, with a particular focus on comets and other solar system bodies.

The main tail of a comet that you see in the sky is caused by the ice of the comet subliming (turning straight from solid to gas) as the comet approaches the Sun. This sublimation of ice also lifts dust of the surface of the comet (this nucleus is generally only a few kilometres in size) which then streams away to form a dust tail that is millions to hundreds of millions of kilometres in length. Looking closer, astronomers also observe another ‘ion’ tail - a tail of ionised gas. It is thinner and has a slightly different colour. The dust tail often appears curved as it is a trail of dust left behind in the comet’s path whereas the ion tail is straight as the charged ions are pushed outwards in the solar wind. Both tails always face away from the Sun, so the tails can appear to proceed the comet when it is travelling out of the solar system.

C/2007 N3 (Lulin) imaged on January 31st (top) and February 4th of 2009.
With Comet Lulin here in 2009, we sometimes also see an “Anti-tail” which looks like it's facing towards the Sun, but this is an optical illusion caused by line-of-sight effects with the comet.  Then in some rare comets, we may also "see" a third main tail, which is a sodium tail. "See" being specialist filters on large telescopes. This was notable in Comet Hale-Bopp in the late 1990s. Image credit: Wikimedia commons
The majority of asteroids in our solar system orbit the Sun in a belt between the orbits of Mars and Jupiter known as the “main belt” and were once thought to be the leftover ingredients for a planet that failed to form, but have a combined mass much smaller than would be necessary for this to be the case. Exactly what asteroids are made of and how many are out there, are questions that scientists are still working on - but they’re mainly rocky or metallic bodies or piles of rubble, sometimes with an icy coating. Comets, on the other hand, are generally thought of as ‘dirty snowballs’, and are more ice than rock. Regular comets come from the outer solar system, in the Kuiper Belt/Trans Neptunian zone or from the Oort cloud, and in the latter case in long, looping orbits that take extremely long periods of time - hundreds or thousands of years, or even longer.