Archive for astronomy

Yesterday was nearly Easter

Posted in History, The Universe and Stuff with tags , , , on March 29, 2021 by telescoper

As as Astronomist I am often asked “How do they calculate the date of Easter?”, to which my answer is usually “Look it up on Wikipedia!“.

The simple answer is that Easter Sunday is on the first Sunday after the first full Moon on or after the Vernal equinox. The Vernal Equinox took place this year on March 20th and the more observant among you will have noticed that yesterday was (a) Sunday and (b) a Full Moon. Yesterday was not Easter Sunday because the rule says Easter is on the first Sunday after the first full Moon on or after the Vernal equinox, which does not include a Full Moon on the first Sunday on or after the vernal equinox. Accordingly Easter 2021 is next Sunday 4th April. If the Full Moon had happened on Saturday, yesterday would have been Easter Sunday.

That is just as well really because next weekend is when the holidays and sporting events have been arranged.

I say “simple” answer above because it isn’t quite how the date of Easter is reckoned for purposes of the liturgical calendar.

For a start the ecclesiastical calculation of the date for Easter – the computus – assumes that the Vernal Equinox is always on March 21st, while in reality it can be a day or two either side of that. This year it was on March 20th.

On top of that there’s the issue of what reference time and date to use. The equinox is a precisely timed astronomical event but it occurs at different times and possibly on different days in different time zones. Likewise the full Moon. In the ecclesiastical calculation the “full moon” does not currently correspond directly to any astronomical event, but is instead the 14th day of a lunar month, as determined from tables (see below). It may differ from the date of the actual full moon by up to two days.

There have been years (1974, for example) where the official date of Easter does not coincide with the date determined by the simple rule given above. The actual rule is a complicated business involving Golden Numbers and Metonic cycles and whatnot.

I’m grateful to Graham Pointer on Twitter for sending this excerpt from the Book of Common Prayer that sheweth how to determine the date of Easter for any year up to 2199:

I don’t care what happens after that as I’ll be retired by then. If you apply this method to 2021 you will find it is an 8C. Next year will be a 9B. Further calculations are left as an exercise to the reader.

R.I.P. Sir Arnold Wolfendale (1927-2020)

Posted in Biographical, The Universe and Stuff with tags , , , on January 4, 2021 by telescoper

I’ve just heard the sad news that former Astronomer Royal Sir Arnold Wolfendale passed away on December 21st 2020 at the age of 93. There’s a full tribute to him here from Durham University, where he spent most of his very distinguished career as a cosmic ray physicist and played such an important role in developing a worldwide centre of excellence in Astronomy.

I remember Arnold Wolfendale very well from many trips to Durham over the years, starting with the SERC School for new postgraduate students in Astronomy I attended in 1985. He was an avuncular and extremely friendly presence there who went to a lot of trouble to talk to studdents; you can see him in the front row of the now (in)famous group photograph taken there:

 

Rest in peace, Sir Arnold Wolfendale (1927-2020)

17 Postdoctoral Positions in Astronomy all at the same Institution!

Posted in The Universe and Stuff with tags , , on October 1, 2020 by telescoper

I know how difficult it is for budding astronomers to find postdoctoral positions, so when I saw that there are no fewer than 17 such positions have become available at the same time at the same institution – Instituto de Astrofísica de Canarias (IAC) on Tenerife (Spain) – I couldn’t resist sharing. Postdoc positions are a bit like buses: you can wait ages for one,  and then seventeen come along all at the same time!

Below you will find links these positions, most of which have deadlines at the end of October (except one with has 15th October, and one at the end of November). Applicants must have their PhD by the time of the application deadline.

The Galaxias 2020 post is in Johan Knapen’s group, and can be to work on deep imaging from LSST.

You will see that 12 of the 17 positions are for 4-year ‘Advanced Fellow’ positions, several of which are in the area of formation and evolution of galaxies. Other areas are Solar physics, exoplanets, stellar and interstellar physics, Milky Way and Local Group, and cosmology & astroparticles.

Other galaxies-related positions are the HARMONI and the ‘Estallidos’ ones; EUROCC is for supercomputing support.

– 12 contratos PS-2020-040 Advanced -Fellows SO 2020 (deadline: 31/10/20)
https://www.iac.es/en/employment/doce-contratos-postdoctorales-advanced-fellows-so-2020twelve-postdoctoral-contracts-advanced-fellows-so-2020-ps

– 1 contrato PS-2020-041 Galaxias 2020 (deadline: 31/10/20)
https://www.iac.es/en/employment/un-contrato-postdoctoral-galaxias-2020one-postdoctoral-contract-galaxias-2020-ps-2020-041

– 1 contrato PS-2020-043 HARMONI 2020 (deadline: 31/10/20)
https://www.iac.es/en/employment/un-contrato-postdoctoral-harmoni-2020one-postdoctoral-contract-harmoni-2020-ps-2020-043

– 1 contrato PS-2020-044 Astroparticulas-MAGIC 2020 (deadline 30/11/20)
https://www.iac.es/en/employment/un-contrato-postdoctoral-astroparticulas-magicone-postdoctoral-contract-astroparticulas-magic-2020-ps-2020-044

– 1 contrato PS-2020-045) EUROCC 2020 (deadline: 31/10/20)
https://www.iac.es/en/employment/un-contrato-postdoctoral-eurocc-2020one-postdoctoral-contract-eurocc-2020-ps-2020-045

– 1 contrato PS-2020-049 Estallidos 2020 (deadline: 15/10/20)
https://www.iac.es/en/employment/un-contrato-postdoctoral-estallidos-2020one-postdoctoral-contract-estallidos-2020-ps-2020-049

 

Astronomy Photograph of the Year 2020

Posted in Art, The Universe and Stuff with tags , , , , on September 24, 2020 by telescoper

Very busy today so I only have time to share a this stunning picture, the overall winner of the 2020 Astronomy Photographer of the Year, Andromeda Galaxy at Arm’s Length? by Nicolas Lefaudeux (France).

 

Photo credit: Nicolas Lefaudeux/2020 astronomy photographer of the year

Watch “Why the Universe is quite disappointing, really – Episode 4” on YouTube

Posted in The Universe and Stuff, YouTube with tags , , , , on May 19, 2020 by telescoper

Episode 4, in which I show that spiral galaxies are very grubby – they contain huge amounts of dust. And not only galaxies – astronomical dust is everywhere we look. The Universe may be big, but it sure is dirty..

Appeal by Astronomers

Posted in Uncategorized with tags , , on January 27, 2020 by telescoper

I apologize for being a bit late onto this but this is a very important initiative that tries to safeguard the sky from the plethora of satellite fleets that threaten to cause untold damage to major astronomical projects, especially surveys. I’ve signed the document and I hope you will also consider doing so.

Many of the readers of this blog will be aware of the fast-moving issue of satellite constellations, which is the launching of the first of potentially tens of thousands of communications satellites. The SpaceX Starlink cluster is one of these, but there will be others such as Amazon’s project Kuiper and Facebook Athena.
These satellite constellations will be detrimental to both optical and radio ground-based astronomy, from their reflected light and broadcasted emissions. Mitigating the effects of these satellites needs to be done quickly before services such as 5G internet from them are established in the coming months. Beyond that point, it will be harder to regulate them.
Organisations which represent our discipline such as the AAS, IAU, EAS and RAS are attempting to engage directly with SpaceX and others on this issue.
Please consider promptly adding your name to the appeal linked to in the post below.

Astronomers' Appeal

Safeguarding the Astronomical Sky (IT)

Download EN_PDFDownload IT_PDF

THIS APPEAL HAS BEEN SIGNED BY

901+ ASTRONOMERS

VIEW SIGNATURES

(the refresh rate of the counter may slow down).

To sign/subscribefollow this link.

This is an international appeal by professional astronomers open for subscription to ask for an intervention from institutions and governments.

Astronomical observations from the ground can be greatly harmed by the ongoing deployment of large satellite fleets in preparation for the next generation of telecommunications.

For centuries the astronomical observations from the ground have led to exceptional progress in our scientific understanding of the Laws of Nature. Currently, the capability of astronomical instrumentation from the ground is endangered by the deployment of satellites fleets.

Through this international appeal and following the same concerns expressed by the International Astronomical Union, IAU [1] and other institutions, we raise a formal request for greater…

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A Problem of Dimensions

Posted in Cute Problems, Maynooth, The Universe and Stuff with tags , , , on August 21, 2019 by telescoper

We’ve more-or-less sorted out who will be teaching what next term in the Department of Theoretical Physics at Maynooth University next term (starting a month from now) and I’ll be taking over the Mathematical Physics module MP110, which is basically about Mechanics with a bit of of special relativity thrown in for fun. Being in the first semester of the first year, these is the first module in Theoretical Physics students get to take here at Maynooth so it’s quite a responsibility but I’m very much looking forward to it.

I am planning to start the lectures with some things about units and dimensional analysis. Thinking about this reminded me that I posted a dimensional analysis problem (too hard for first-year students) on here a while ago which seemed to pose a challenge so I thought I would post another here for your amusement.

 

The period P for an elliptical orbit of semi-major axis a of  a moon of mass m around a planet of mass M, depends only on the quantities  a, m, M and G (Newton’s Gravitational Constant).

(a). Using dimensional analysis only, determine as completely as possible the relationship between P and these four quantities.

(b). How would the period P compare with the period P′ of a system consisting of a moon of mass 2m orbiting a planet of mass 2M in an ellipse with the same semi-major axis a?

Please submit your efforts through the comments box below.

 

Walter’s Leaving Do

Posted in Cardiff, Science Politics, The Universe and Stuff with tags , , , on May 18, 2019 by telescoper

As I had little window of opportunity before the start of exam marking season and other goings-on in Maynooth I decided to make a quick trip back to Wales back in Cardiff for the weekend.

I flew back on Thursday evening. It had been a busy day and I’d only had a sandwich for lunch so I went into the bar in Dublin Airport to get a beer and a burger. Who did I bump into there but Professor Walter Gear…

Walter was Head of the School of Physics and Astronomy at Cardiff University when I joined it in 2007, so and was he persuaded me to leave Nottingham. He was a very good Head of School and, in particular, he helped a lot when I had mental health problems seven years ago.

Anyway after twenty years in Cardiff during which he built up the School and particularly the world-leading Astronomy Instrumentation Group there, Walter has left for a new position as Dean for Science and Engineering at NUI Galway, in Ireland.

He was in Dublin Airport because he was travelling back to his leaving do in Cardiff, which I turned up for on Friday. There were drinks and speeches and presents and it was nice to see some old friends there and in the Flute and Tankard afterwards. It was a good send-off.

I’m sure that Walter (who was born in Ireland) enjoy his new role in the Emerald Isle very much indeed. Galway is quite a distance from Maynooth (almost 200 km) but I hope we will be in regular contact.

Anyway I should mention that there are advertisements out for a Research Associate in Sub-mm Astronomy and and a Lecturer in Astronomy (with an emphasis on the same) in Galway. I’m sure these will prove very attractive to many applicants!

Spring Equinox in the Ancient Irish Calendar | 20 March 2019

Posted in Uncategorized with tags , , , on March 20, 2019 by telescoper

I’m sharing this interesting post with a quick reminder that the Vernal Equinox in the Northern Hemisphere occurs today, 20th March 2019, at 21:58 GMT.

Stair na hÉireann | History of Ireland

Equinox is the date (or moment) some astronomical alignments in Ireland mark as being auspicious. Not many, mind you, but some, like the cairn on Loughcrew or the two passages of Knowth, a sort of super-alignment with quadruple significance. Though the actual alignment of Knowth is disputed, it might be a lunar alignment or not an alignment at all.
 
The equinox is far less obvious an astronomical event than the two solstices, celebrated in Ireland and also the subject of astronomical alignments. It is like the equinox, which occurs in-between the winter solstice and the summer solstice, and vice versa, twice a year. However, it is just one event, as the spring and autumn equinox happens at different dates, but are for all intents and purposes identical events.
 
Taking place around 20th March and 22nd September, the equinox is the moment when the plane of the Earth’s equator passes…

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Banging the drum for ESO

Posted in Maynooth, The Universe and Stuff with tags , , , on February 6, 2019 by telescoper

It was a pleasure to welcome Rob Ivison, Director of Science at the European Southern Observatory (ESO) , to Maynooth this afternoon for a colloquium.

I was on my best behaviour introducing his talk and even refrained from pointing out that his native Lancashire is actually in the Midlands.

Ireland became a full member of ESO earlier this year and Rob has been touring Ireland giving talks to encourage Irish astronomers to make the most of the many opportunities membership presents. Having already visited Cork and Galway he passed through Maynooth today before ending up in Dublin tomorrow.

It was an enjoyable and impressive talk and very nice to chat with Rob afterwards over dinner.

Bon voyage to Rob and thanks for the visit!