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.

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.

Unpredictable Space Weather

It regularly fills the skies over the poles with bright light shows known as the aurora. It destroys satellites, possibly resulting in the failure of wireless communications, ATMs and television. It could leave large areas without power for months. But what is ‘it’? - Space Weather.

Photograph of Aurora taken from onboard the International Space Station by European astronaut André Kuipers. Image credit: ESA

Space weather is dangerous and a large event could have a massive impact on society. But what is ‘Space Weather’? What are the possible effects? What are the questions that still need answering?

‘Space Weather’ describes the happenings in the environment surrounding the Earth. This ‘weather’ is fuelled by the Sun’s unpredictable activities – more specifically solar flares, Coronal Mass Ejections (CMEs), coronal holes and solar prominences. We are completely dependent on the Sun, it can be our best friend or our worst enemy.

Celebrating 10 years of Mars Express

At the beginning of June, the European Space Agency (ESA) celebrated the 10 year anniversary of the Mars Express mission. The spacecraft, launched in 2003, has had ten successful years of operation and has resulted in the publication of over 600 scientific papers. To help mark this occasion, our intern Cait interviewed Olivier Witasse, the mission's Project Scientist, about some of the key discoveries the spacecraft has made and what the future of the mission looks like.

Mars Express has had ten very successful years in orbit around Mars. Image credit: ESA

One of the key themes of space exploration is the search for life. We base our search for past or current life on the presence of liquid water – it's vital for life like ours so it's one of the first conditions we look for. Direct evidence of past water on Mars is one of the key findings and surprises of the Mars Express mission:

"...from what we have been discussing with the scientists over the last year, there is one result which I think is really on top of the others - the discovery of the so called hydrated minerals."

Before the discovery of hydrated minerals, scientists at ESA were expecting to find carbonates on what may have once been a sea bed. Finding carbonates would imply that there were once large oceans on Mars. Carbonates can form in one of two ways - a purely chemical reaction where carbon dioxide in the atmosphere is dissolved by the surface water of an ocean or as a result of the shells of past marine creatures. If the oceans were absorbing atmospheric carbon dioxide then further reactions with minerals (i.e. magnesium, calcium) in the ocean would produce carbonates which would settle onto the ocean floor. The atmosphere on Mars is mostly carbon dioxide, so if there were once oceans on Mars we would expect the formation of these carbonates. The shells of some marine animals also contain carbonates, so when the creatures die, their shells sink to the bottom of the ocean to form carbonate deposits with the possible preservation of fossils. These carbonates would remain even when the ocean faded away.

Simulations, Svalbard and the Solar System

It's been a busy couple of weeks of inspiring science! I've had a couple of days wow-ing other people with talks and tours of the things we know and I've been working here and been amazed, inspired and slightly concerned about some of the things we don't.

Cait Percy in our London office.
Photo ©TWDK.

Most of the last week or two has been spent exploring dreams, parallel universes, how much life there really is in the oceans and the questions to which radio astronomy may soon provide the answers. I spent a lovely afternoon pondering the Universe and trying to decide if we were all just part of a very large computer simulation and whether we'd know if we were. Almost everyone I've chatted to this week has had some variation of the above brought up in conversation for discussion so I really feel I've been doing my bit to share my passion for science.

A year of unanswered questions (and that's a good thing)

We’ve been adding regular posts to this blog for exactly one year this month. Last June our very first intern, Jon started with us through our partnership with SEPnet, and a year on we have another two new interns with us for the summer through them. We still have our two chemistry students at the moment (Freya and Lucy), and last but not least we've been joined by a business and marketing intern via the Sheffield Business School.

The year in numbers:

• 40 blog posts
• 16 guest posts, including researchers from the UK, US, the Netherlands, Mexico, and Belgium
• over 24,000 visits to the blog
• almost 11,000 unique visitors
• our site is being read for 1 out of every 3 minutes
• interviewed by start something and GDI Impuls
• stage appearances in Germany, Austria, and Switzerland as part of the Freischwimmer arts festival and Aarau Democracy Days
• we've never paid to advertise our blog

Month by month, our audience has grown at an increasing rate