Monday, November 7, 2016

What is a Supermoon?

The astronomical news this month is all about the "Supermoon" happening on the night of 14th November 2016. But what is a Supermoon, and why is it different to any other Full Moon?

Let's start simple, with what it means to have a Full Moon. All this means is that the Moon is in the point of its orbit around the Earth which puts it directly opposite the Sun in the sky. As a result the side of the Moon we see is fully illuminated by the Sun, and the Moon rises at sunset (and sets at sunrise) making it visible all night.

Diagram illustrating how the phase of the Moon depends on its position in its orbit around the Earth relative to the location of the Sun. In this diagram the Sun is not shown, but it is to the right, directly above the point on the Earth labelled "Noon". Credit: Wikimedia, Thomas Splettstoesser.
 So obviously, the Full Moon happens once in every lunar orbit around the Earth (well technically slightly less, because meanwhile the Earth is also orbiting the Sun, but let's not worry about that). Now the orbit of the Moon isn't perfectly circular. It's very slightly oval shaped, with a point (which is called the "perigee") when the Moon is at its closest to the Earth, and a point (called "apogee") when it is at its furthest.

This difference is very small - much smaller than shown in the diagram above. If I drew an oval with the right proportions you couldn't tell it wasn't a circle! The mean distance to the Moon is 384,400 km, the closest approach is just 21,296 km closer than this. That might sound a lot, but it's just 5% closer than the average (an apogee is 5% more distant than average). 

A Supermoon is just the name we give for a Full Moon which happens when the Moon is at or close to perigee (i.e. it's closest point to the Earth). Being 5% closer than average makes the Moon look a barely noticeable 5% larger, however the impact on its brightness is more significant, making Supermoons the spectacle that gets attention. A Supermoon will be 30% brighter than a Full Moon at apogee. High and low tides will also be more extreme when the Moon is closer.

The Supermoon of 19th March 2011 (right) compared to an average full Moon (left). Credit: Wikimedia, Marco Langbroek.

Now how close the Supermoon is to the exact point of perigee determines the exact distance to the Full Moon and how super the Supermoon is. The upcoming Full Moon happens at 3pm GMT, Monday 14th November 2016, when the Moon is within 1.5 hours of passing through perigee, making it a "super Supermoon". 

 What's more, the distance of lunar perigee also varies slightly (caused by the gravity of other planets in the Solar System and various resonances). The November 14th perigee happens to be a  close one. This means that 14th November is really a super-dooper Supermoon; a lunar perigee hasn't happened so close to the Earth since January 26, 1948, and the next Full Moon which is so close will be November 25, 2034.

 While these are relatively rare events, the noticeable difference in the Moon is quite small. The Full Moon is well worth catching every month, even if the nights of 13th/14th November 2016 ti will be slightly brighter and larger than average.

xkcd comic explaining the Supermoon.

 And be aware that Supermoons are getting gradually less super. The Moon is very slowly moving away from the Earth. However as it's moving away at just 3.8cm each year, it'll be a while (a few billion years) before this makes any noticeable difference.

Tuesday, August 9, 2016

Once in a Blue Moon

  Last week was full of interesting Moon news. “Moon Express” has become the first commercial company approved to try to land on the Moon, on the same day that the Chinese Moon Rover, “Jade Rabbit”, said goodbye (tweeting “This time it really is goodnight/ There are still many questions I would like answers to, but I'm the rabbit that has seen the most stars."  on Weibo, the Chinese version of Twitter), after surviving for more than 18 months longer than its planned 3 month mission.

Blue Moon of December 2009. Credit: Codybird, Wikimedia

To date, just three nations have landed on the Moon. The Jade Rabbit rover, named after the pet rabbit (YuTu) of the Chinese Moon goddess, Change’e, joined over 80 different US and Russian probes on the surface, as well as the remnants of the Apollo missions which saw 10 American men walk on the Moon’s surface in the 1960s and 1970s.

The success of the Chinese rover is exciting enough, but the news from Moon Express could be a signal of the start of a new era of Moon exploration. Moon Express is just one of sixteen groups aiming for the Google Lunar X-Prize. This competition, launched in 2007, calls for a privately funded rover to land on the Moon drive at least 500m and transmit back HD video and images before the end of 2017. The first group to do this can claim a $20m prize, as well as a place in space history.

This week is significant as Moon Express has passed on of the big unknowns in the mission. The Outer Space Treaty, made in 1967, sets out the rules about what National space programmes can and cannot do in space, and also states that the activities of non-governmental entities in outer space, requires authorisation and supervision by one of the State Parties to the Treaty. This meant that, unlike the many companies who are now launching into low Earth orbit, governmental permission is needed for any commercially planned Moon landing. This is the first time that permission has been sought, and is would have been a complete unknown who among the various US bodies needed to give permission to the Californian based company.

 In the end a cabal of federal agencies were involved, from the Federal Aviation Authority, NASA of course, and even the White House, taking almost 4 months to assess the application. Permission has been granted for a single mission only, and Moon Express has a launch date scheduled towards the end of 2017 which if it manages to meet will not only win it the X-prize, but also make it the first commercial enterprise to make it into outer space.

 Meanwhile other nations are looking Moonward. Both South and North Korea have stated ambitions to land a robotic mission on the Moon within the next decade, and Russia, ESA, NASA and Japan currently have plans to send people to the Moon. The first of these missions could see Americans return to the Moon in preparation for Mars missions as soon as 2023; development and construction of the new Orion Spacecraft is ongoing at NASA, and the first planned test mission of this deep space vessel will see it go into lunar orbit.

 The Moon is seen as a safe stepping stone to longer missions. A place to learn about how to live and work long term in space just a few days away from Earth rather than the months it would take to get to Mars. Commercially the Moon provides a potential mining resource (especially for high value elements rarely found on Eart), and astronomers like myself are excited about the potential for Moon based observatories, perhaps radio telescopes on the far side of the Moon shielded from the human radio noise.

 After decades of inaction, it seems the time is ripe to return to the Moon.

If you want to see the Moon tonight look for the crescent Moon lingering after sunset in the evening skies; you can see the first full Moon of August (which rises as the Sun sets) on August 18th. The next Blue Moon (defined as a rare second full Moon in single month) will occur on 31st Jan 2018.

Friday, June 17, 2016

Women of the Future 2016 Nominations now open

The Women of the Future Awards are the platform for successful young women in Britain. These awards are aimed at unearthing and recognising the inspirational stars of tomorrow across diverse sectors. I was honoured to win the Science category of this award in 2014, and I am keen to encourage more engagement with the awards from women in STEM. Please feel free to contact me directly ( if you have any questions/concerns about what these awards are all about.

I personally view participation with this organisation as a great way to engage in outreach about STEM subjects with women in general. The low numbers of women in science means that we are often in a minority in a group of scientists, but also within a group of women. The young people who attend events organised via the Women of the Future: Ambassadors Programme (at which Award winners and shortlisted candidates are invited) are not seeking out discussion of STEM subjects as careers specifically, so this can be a great way to get outside the group of already engaged. And the Women of the Future Network provides the opportunity to network with successful professional women in the UK across all sectors (which is inspiring and interesting, as well as potentially useful). This has led to interesting opportunities - for example I was invited to discuss the issues of women in STEM at the House of Lords this year.

The Awards are open to all women aged 35 or under (candidates must be aged 35 or under on December 31, 2016) living or working in the United Kingdom (Mentor of the Year and Young Star Awards have different eligibility, see below).

Award Categories which I think would of Interest to Women in STEM:

This category recognises a group of truly remarkable young female scientists, forging new ground in research and scientific achievement. Within this category, WoF are also seeking nominees with a career in the sciences who can demonstrate a track record of academic excellence in the field of science; and are showing signs of success in pushing through scientific developments to commercial application.

Recent winners:
2015: Dr. Tessa Baker, Postdoctoral Fellow at All Souls, University of Oxford
2014: Dr. Karen Masters, Senior Lecturer in Astronomy, Institute of Cosmology and Gravitation, University of Portsmouth
2013: Dr Janice Turner, technical project manager, Roke Manor Research

Technology and Digital
This category recognises talented, ground-breaking young women from the worlds of digital and technology.

Recent winners:
2015: Dr. Laura Toogood, Managing Director of Private Clients, Digitalis Reputation
2014: Brie Rogers Lowery, UK Director,
2013: Kathryn Parsons, founder, Decoded

Mentor of the Year
This award, recognises active mentors behind the success of younger women in British life. Many successful women pay tribute to role models and supporters who have enabled them to flourish in business, professional life, science or whatever their chosen field. This award pays tribute to some of the most influential and unsung heroes and heroines in British life.
The award is open to men and women of all ages.

Recent winners:
2015: Alex Peace-Gadsby, Director, Musto Limited
2014: Dr Vanessa Ogden, Head Teacher, Mulberry School
2013: Helen Milford, south regional director, Asda

Young Star
This award acknowledges high achievers aged 16-21. It is for teenage girls showing exceptional promise within their industry, university or school.

Recent winners:
2015: Phoebe Gormley, Managing Director, Gormley & Gamble
2014: Suzanne Birney, Apprentice CAD Technologist, Doosan Babcock
2013: Eliza Rebeiro, founder, Lives not Knives

Entry deadline: September 12th 2016
Judging Day (central London): October 14th 2016
Awards Night (London Hilton on Park Lane - shortlisted candidates get a complimentary ticket): 16th November 2016

There are two ways to nominate (self nominations are welcome):
1. Complete the application form ( - self nominations are welcomed.
2. Email candidate suggestions to (they will then be contacted and invited to fill in the application form).

For more details:, or contact me at

Please pass this message on to any Women in STEM groups you are part of.

Friday, March 4, 2016

My Advice for PhD Applicants

So you want to do a PhD in astronomy/astrophysics/cosmology? Here is some random advice from me (note these are my personal opinions, and not representative of any official policy anywhere I have worked, or currently work).

Preparatory work: 
  • Try to do one or more summer research projects to demonstrate your interests/abilities in research.
  • If you are on a 1 year taught Masters 
    • get to know your lecturer immediately so they can write a good reference. 
    • start your project early. If the course structure has the project late do a summer project, or start your project early (even if they say not to).

Application materials:
  • Write a cover letter, or a description of why you want to do a PhD, and what your subject interests are. This is your chance to show passion for your subject. Do some research on what is available at the department you are applying to first (e.g. don't write about how much you love exoplanets, if no-one in that department studies them....).
  • If you can remain somewhat open to the details of a project/supervisor (you'll be easier to place). Not all faculty will be recruiting PhD students every year, but you can still potentially work with them as a co-supervisor. 
  • Don't leave gaps in your CV. If you are currently working and want to come back to study do not hide it. This is often viewed positively - use your experience to hi-light the skills you have gained in the workplace which should place you above undergraduates still at University. 
  • Be very clear about your nationality - especially if you are British applying for PhDs in Britain. This shouldn't matter, but it seems to.

  • Dress up for the interview (at least a bit - you offend no-one by being over dressed, if you show up in tracksuit bottoms you may send a message that you don't care to some).
  • Show an interest in the department. Stay for lunch if invited. It's not really optional (even if presented as such). Ask the current graduate students if there are any evening plans you can tag along to.
  • Ask questions about the training, help given to find jobs etc. 
  • Talk to everyone - especially current students. If you think you're getting a sales pitch press harder for the real story.
  • Make extra sure you talk to current students of any faculty you think you might want to work with. Ask about their working style. Are they too hands off - are they too pushy - do they take credit for student's work - do they promote their students outside the University. 
  • Be careful you don't assume women you meet are admin staff - assume everyone you meet is a scientist and potentially a future supervisor. Do not address anyone as Miss or Ms or Mr (just in case). 
  • Be polite to everyone you meet. The interview panel might seek input from anyone in the department (including the admin staff).
There's loads of other good advice online about this already, so don't just read this. Astrobetter has a fantastic set of resources (sometimes with an American angle, but many things apply to any PhD programme).

Monday, January 25, 2016

Thoughts on the 9th Planet

The internet was abuzz last week with news of a possible 9th planet in our Solar System, as well as an opportunity to view all five planets visible to the naked eye in the sky at the same time for the first time in more than a decade. Coming on the heels of the BBC StargazingLIVE show, and ongoing coverage of Tim Peake's mission oboard the International Space Station) it feels like space and astronomy has never been more at the front of the UK public’s consciousness.

The possibility of the discovery of a new planet so close to us might seem to make a mockery of how much we claim to know about the vast expanse of space. You might ask how we can claim we understand the structure of galaxies in the distant Universe when we have potentially missed an entire planet in our own solar system for so long. But this planet, if it turns out to be real, will be very dark indeed. The predictions suggest it orbits the Sun, 20 times further out that Neptune (which in turn is 30 times further out than the Earth). At this distance the planet would take 10,000-20,000 years to orbit the Sun, moving incredibly slowly against the background stars. And the illumination from the Sun would be over 300,000 times less than it is here at Earth, making it both a very cold and dark place, as well as an incredibly hard thing to spot with a telescope. Astronomers all over the world will now be searching for this tiny speck of light, in an interesting parallel of several previous searches which have happened following earlier predictions of missing planets (these earlier searches led to the discover of Neptune, as well as Ceres and Pluto – two objects we now consider dwarf planets, but which we initially called planets). 

Of course the last time the number of planets in our Solar System was in the news we all had to come to terms with losing a planet. Pluto is still exactly where it always was, but in 2006 was reclassified as a dwarf planet following the discovery of potentially hundreds of Pluto like objects in the outer solar system. As an astronomer it never fails to surprise me how much this reclassification, which you might dismiss as an obscure technical discussion, captures the public imagination. This has recently been back in the news following the amazing pictures of Pluto sent back by the New Horizons Mission. While I’m often surprised at the interest this generates, I’m also pleased for the opportunity it gives to remind us all that science isn’t a fixed and static thing. We reclassify planets on the basis of new information, and we can still have the opportunity to discover massive new planets in our own backyard. 

The already iconic view of Pluto from the NASA New Horizon's Mission.

If you want to see all six planets visible to the naked eye at once (Mercury, Venus, Earth, Mars, Jupiter and Saturn) you can get up early on any clear morning over the next month or so. Venus and Jupiter will be the two brightest points of light you can find in the sky – Jupiter is to the West, and Venus to the East. In a rough line between them will be the noticeably orange tinged Saturn and Mars. Mercury is a challenge as it’ll be a small point of light fading into the dawn light as the Sun rises – of course Earth you can see all the time (just look down). 

A screenshot from the free planetarium software Stellarium showing all 5 visible planets together in the sky at 6.50am on Tue 26th Jan 2016
To see the International Space Station and wave at Tim Peake as he passes by, you can look for notifications of the next visible ISS passesonline. The next ones visible from where I live (in the UK) are Feb 2nd and 3rd in the evening. The ISS looks like a steadily moving constant point of light to the naked eye, and you see the reflected sunlight off its solar panels.

A real picture of Stargazer Lottie in Space

This weekend Tim Peake posted this actual picture of his Stargazer Lottie doll on board the ISS!

Now don't get me wrong, I've been loving the #lottieinspace illustrations created by ESA and explaining what life is like in space, but they were also obviously faked, and I've had to explain several times already that that doesn't mean Lottie isn't up there, just that those images are faked. Now we have an actual real picture, that explanation got a whole lot easier. :)

If there's any kids in your life, they can Ask Lottie all their space questions. She's waiting by her computer!