Seasons: Astronomy vs. Australia

Something that really shocked me when I started to live in Australia ~7 years ago was to hear everywhere that seasons start at the beginning of the corresponding month. That is, as today is Sep 1st, everyone in the radio / advertisements / news is welcoming Spring. And this, being an astronomer, believe me, hurts. Why? Because astronomically we are still in winter. Seasons are defined by Astronomy in a very accurate and precise way. This year Spring starts on September 23rd, 11:29 AEST (02:29 Universal Time). That is when that the Autumn Equinox happens, and the real moment Spring starts in the Southern Hemisphere (and Autumn/Fall starts in the Northern Hemisphere).

The seasons are caused by the combination of three astronomical factors: the Earth’s is a (almost perfect) sphere, the Earth’s orbit around the Sun, and the Earth’s axial tilt. As a consequence of these the Earth’s atmosphere is unequally heated by the Sun around the year at a given position. Therefore, the seasons are marked by the movement of the Earth around the Sun and, hence, which way the Earth is tilted with respect to the Sun. When the South hemisphere is tilted towards the Sun, the Sun’s rays strike the Earth at a steeper angle compared to a similar latitude in the North hemisphere. As a result, the radiation is distributed over an area which is less in the South hemisphere than in the North hemisphere. This means that there is more radiation per area to be absorbed in the South hemisphere, and therefore it is winter in the North hemisphere and summer in the South hemisphere.

Illumination of Earth by Sun at the southern solstice. Credit: Wikipedia


By astronomical definition, the precise timing of the seasons is determined by the exact times of transit of the Sun over the tropics of Cancer and Capricorn for the solstices and the times of the Sun’s transit over the Equator for the equinoxes, as specified in this figure:

Movement of the Earth around the Sun following an orbital ellipse (with eccentricity exaggerated for effect) and seasons. Equinoxes (20 or 21st March and 22nd or 23rd September) happen when the tilt of Earth’s axis neither inclines away from nor towards the Sun (green dotted line), and hence two points a the same latitude but a different hemispheres receive the same amount of energy from the Sun. In an equinox, the Sun is found at the zenith at the midday at the Equator. A solstice (20th or 21st June and 21st or 22nd December) happens when the tilt of the Earth’s axis has maximum effect (23.44º, red dotted line). At the June solstice the Sun is found at the zenith at the midday (just over our head!) at latitude 23.44º North, defining the Tropic of Cancer. Similarly at the December solstice this happens at 23.44º South, known as the Tropic of Capricorn. The periapsis (perihelion) and the apoapsis (aphelion) mark the nearest and the farthest points from the Sun, respectively (blue dotted line). Credit: Wikipedia


Therefore, in the South hemisphere, Spring starts with the Autumn Equinox, Summer with the Winter Solstice, Autumn with the Spring Equinox and Winter with the Summer Solstice. Of course, the names were given as correct for the North hemisphere.

Well, at least all of this is what Astronomy says. However, Governments and societies quite often decide to use their own definitions. Just checking this webpage of the Australian Bureau of Meteorology:

In Australia, the seasons are defined by grouping the calendar months in the following way:

1. Spring – the three transition months September, October and November.
2. Summer – the three hottest months December, January and February.
3. Autumn – the transition months March, April and May.
4. Winter – the three coldest months June, July and August.

These definitions reflect the lag in heating and cooling as the sun appears to move southward and northward across the equator. They are also useful for compiling and presenting climate-based statistics on time scales such as months and seasons.

Following these assumptions, Australia indeed enters in Spring today, which is funny because the majority of the countries (if not all) of the North hemisphere are still in Summer. In any case, for me it is Winter, and it will be winter till next on September 23rd, 11:29 AEST, when Spring, according to Astronomy, really starts.

Sequence of the occultation of Saturn by the Moon

DP ENGLISH: This story belongs to the series “Double Post” which indicates posts that have been written both in English in The Lined Wolf and in Spanish in El Lobo Rayado.

DP ESPAÑOL: Esta historia entra en la categoría “Doble Post” donde indico artículos que han sido escritos tanto en español en El Lobo Rayado como en inglés en The Lined Wolf.

Today Sunday I’ve used some of my free time to process the images I took last Wednesday, when Saturn was occulted by an almost full Moon. These are my two final images showing how Saturn first disappears behind the Moon and it reappears an hour later.

The Moon occults Saturn I: Saturn disappears.
14 May 2014 from Sydney. Data obtained using Telescope Skywatcher Black Diamond D = 80 mm, f = 600 mm, 20 mm eyepiece + CANON EOS 600D. All times are given in Universal Time, add 10 hours to get the local time in Sydney (AEST) that date. Images of Saturn obtained combining many frames at 1/60 and 1600 ISO using Lynkeos software + Photoshop. Image of the Moon obtained combining 20 best frames using Photoshop. Credit: Á.R.L-S. (AAO/MQ)


The Moon occults Saturn I: Saturn disappears.
14 May 2014 from Sydney. Data obtained using Telescope Skywatcher Black Diamond D = 80 mm, f = 600 mm, 20 mm eyepiece + CANON EOS 600D. All times are given in Universal Time, add 10 hours to get the local time in Sydney (AEST) that date. Images of Saturn obtained combining many frames at 1/100 and 1600 ISO using Lynkeos software + Photoshop. Image of the Moon obtained combining 11 best frames using Photoshop. Credit: Á.R.L-S. (AAO/MQ)

Getting nice images of Saturn was much trickier than I expected: the setup I used the other night it is not the best to observe Saturn, as more magnification and a good tracking are needed. On the other hand, the Moon was very bright so I had to use short exposition times, and hence Saturn appeared very dim. At the end I manage to get a kind of “master Saturn” combining the best frames I took during the night and later combine it with the data of each position to get the final view of Saturn at each time. For the Moon it was much easier, although you’ll perhaps realize that the second image is somewhat better than the first. The reason is that some parts of the Moon were actually saturated with the 1/60 seconds exposures, and that is why I later used 1/100 seconds for getting Saturn reappearing. In any case, I hope you like them.

Occultation of Saturn by the Moon

Today, 14th May 2014, Saturn is occulted by the Moon, although this can only be seen from most Australia and New Zealand. I’ve set up my telescope in the backyard and now I’m taking some photos of the event. Although I’ll try to get better images later, let me show you what I’m obtaining now.

These three images show how Saturn is moving closer to the Moon:

Occultation of Saturn by the Moon, as observed from my backyard in Sydney. I used my Skywatcher Black Diamond Telescope D = 80 mm, f = 600 mm and my CANON EOS 600D, and a 20mm eyepiece projection, at 1600 ISO and speed 1/60. This is just a single frame obtained at 20:44 AEST (10:44 UT). I also used Photoshop to play with the levels/colours/saturation. Credit: Angel R. López-Sánchez.

Occultation of Saturn by the Moon, as observed from my backyard in Sydney. I used my Skywatcher Black Diamond Telescope D = 80 mm, f = 600 mm and my CANON EOS 600D, and a 20mm eyepiece projection, at 1600 ISO and speed 1/60. This is just a single frame obtained at 21:12 AEST (11:12 UT). I also used Photoshop to play with the levels/colours/saturation. Credit: Angel R. López-Sánchez.

Occultation of Saturn by the Moon, as observed from my backyard in Sydney. I used my Skywatcher Black Diamond Telescope D = 80 mm, f = 600 mm and my CANON EOS 600D, and a 20mm eyepiece projection, at 1600 ISO and speed 1/60. This is just a single frame obtained at 21:18 AEST (11:18 UT), the planet is “touching” the disc of the Moon. I also used Photoshop to play with the levels/colours/saturation. Credit: Angel R. López-Sánchez.

After that, I waited for 40 minutes to see Saturn reappears behind the Moon, as it is shown is the next three photos:

Occultation of Saturn by the Moon, as observed from my backyard in Sydney. I used my Skywatcher Black Diamond Telescope D = 80 mm, f = 600 mm and my CANON EOS 600D, and a 20mm eyepiece projection, at 1600 ISO and speed 1/100. This is just a single frame obtained at 21:59 AEST (11:59 UT). I also used Photoshop to play with the levels/colours/saturation. Credit: Angel R. López-Sánchez.

Occultation of Saturn by the Moon, as observed from my backyard in Sydney. I used my Skywatcher Black Diamond Telescope D = 80 mm, f = 600 mm and my CANON EOS 600D, and a 20mm eyepiece projection, at 1600 ISO and speed 1/100. This is just a single frame obtained at 22:05 AEST (12:05 UT). I also used Photoshop to play with the levels/colours/saturation. Credit: Angel R. López-Sánchez.

Occultation of Saturn by the Moon, as observed from my backyard in Sydney. I used my Skywatcher Black Diamond Telescope D = 80 mm, f = 600 mm and my CANON EOS 600D, and a 20mm eyepiece projection, at 1600 ISO and speed 1/100. This is just a single frame obtained at 22:15 AEST (12:15 UT). I also used Photoshop to play with the levels/colours/saturation. Credit: Angel R. López-Sánchez.

In the next few days I’ll prepare some few better (processed) images. Stay tuned!

A 2dF night at the Anglo-Australian Telescope

One of the most complex astronomical instruments nowadays available is the Two Degree Field (2dF) system at the Anglo-Australian Telescope (AAT, Siding Spring Observatory, NSW, Australia). The main part of 2dF is a robot gantry which allows to position up to 400 optical fibers in any object anywhere within a “two degree field” of the sky.

The 2dF instrument attached to the primary focus of the AAT. Note that the mirror of the telescope is opened. This image was chosen to be part of the Stories from Siding Spring Observatory Photo Exhibition the AAO organized last year.
Credit: Á.R.L-S.

392 optical fibers are fed to the AAOmega spectrograph, which allows to obtain the full optical spectrum of every object targeted by an optical fiber. The remaining 8 optical fibers are actually fibre-bundles and are used to get an accurate tracking of the telescope while astronomers are observing that field, which may last up to 3 hours. 2dF possesses two field plates: one located at the primary focus of the telescope and another at the position of the robot gantry. While a field is being observed in one plate, 2dF configures the next field on the other plate. A tumbling mechanism is used to exchange the plates. 2dF was designed at the AAO in the late 90s and, since then, it has been used by a large number of international astrophysicists. In a clear night, 2dF can obtain high-quality optical spectroscopic data of more than 2,800 objects.

Indeed, this sophisticated instrument has conducted observations for hundreds of astronomical projects, including galaxy surveys such as the 2dF Galaxy Redshift Survey, the WiggleZ Dark Energy Survey, and the Galaxy And Mass Assembly (GAMA), survey which is still on going and in which I actively participate. The optical fibers of 2dF can be also fed the new HERMES spectrograph, which is now starting the ambitious Galactic Archaeology with HERMES (GALAH) survey at the AAT. GALAH aims to observe around 1 million galactic stars to measure elemental abundances and measure stellar kinematics.

Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. The 2dF robot gantry moving and positioning the optical fibers. Credit: Á.R.L-S.

How does 2dF move and position the optical fibers? A very nice way of explain it is using the time-lapse technique, that is, taking many images and then adding all to get a movie of the robot while moving and positioning the fibers. That is why in 2012 I decided to create the video, A 2dF night at the AAT, which assembles 14 time-lapse sequences taken at the AAT during September and November 2011 while I was working at the AAT as support astronomer of the 2dF instrument. Actually, this time-lapse video shows not only how 2dF works but also how the AAT and the dome move and the beauty of the Southern Sky in spring and summer. The time-lapse lasts for 2.9 minutes and combines more than 4000 frames obtained using a CANON EOS 600D provided with a 10-20mm wide-angle lens.

Time-lapse video “A 2dF night at the AAT”. I recommend to follow the link to YouTube and watch it at HD and full screen in a dark room. Credit: Á.R.L-S.

The video consists in three kinds of sequences created at 24 frames per second (fps). The first 3 sequences show how the 2dF robot gantry moves the optical fibers over a plate located at the primary focus of the telescope. Although in real life 2dF needs around 40-45 minutes to configure a full field with 400 fibers, the time-lapse technique allows to speed this process. The first 2 sequences have been assembled taking 1 exposure per second, therefore 1 second of the video corresponds to 24 seconds in real life. The third sequence considers an exposure each 3 seconds, and hence it shows the robot moving very quickly. The next four sequences show the movement of the telescope and the dome. All of them were obtained taking 2 images per second (a second in the movie corresponds to 12 seconds in real life). The long black tube located at the primary focus of the telescope is 2dF. The remaining sequences, all obtained during the night, were created taking exposures of 30 seconds, and hence each second in the video corresponds to 12 minutes in real life.

Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. The AAT telescope, with 2dF (the long, black tube) attached at its primary focus, is prepared to start observing. Credit: Á.R.L-S.

Astronomical time-lapse videos allow to see the movement of the Moon, planets and stars in a particular position in the Earth, something that conventional videos cannot achieve. In particular, dim stars and faint sky features, such as the Milky Way with its bright and dark clouds and the Magellanic Clouds, can be now easily recorded. As in my first time-lapse video, The Sky over the AAT, I set the camera up at the beginning of the night, let it run, and check on its progress occasionally. I used at focal of f5.6 and an ISO speed of 1600 ISO for the night sequences.

Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. The Magellanic Cloud rise while the Milky Way sets over the Anglo-Australian Telescope at Siding Spring Observatory on 3 Nov 2011. Some kangaroos can be seen in the ground. Credit: Á.R.L-S.

However, the procedure that took more time was processing the hundreds of individual photographies included in each sequence. In many cases, I needed more than 12 hours of computer time, including 3 or 4 iterations per sequence, to get a good combination of low noise and details of the sky, plus “cleaning” bad pixels or cosmic rays. In particular, for this video I tried hard to show the colours of the stars, a detail which is usually lost when increasing the contrast to reveal the faintest stars. In the last sequence of the video, Aldebaran and Betelgeuse appear clearly red, while the stars in the Pleiades and Rigel have a blue color.

Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. A dark night at The Anglo-Australian Telescope (23 Sep 2011). Orion constellation is seen over the AAT dome. The red colour of Alderaban and Betelgeuse and blue colours of Pleiades and Rigel are clearly distinguished. Credit: Á.R.L-S.

As I did for my previous time-lapse, here I also included a sequence which shows the trails created by the stars as they move in the sky as a consequence of the rotation of the Earth. This sequence shows the Celestial Equator and stars at the South (top) and North (bottom) Celestial Hemisphere. Note that star trails have indeed many different colours. Other details that appear in this time-lapse video are clouds moving over the AAT, satellites and airplanes crossing the sky, the nebular emission of the Orion and Carina nebulae, the moonlight entering in the AAT dome, and kangaroos “jumping” in the ground.

Frame of the time-lapse video “A 2dF night at the Anglo-Australian Telescope”. Startrails over the Anglo-Australian Telescope on 23 Sep 2011. The colours of the stars are clearly seen in this image, which stacks 1h 6min of observing time. Credit: Á.R.L-S.

Finally, I chose an energetic soundtrack which moves with both 2dF and the sky. It is the theme Blue Raider of the group Epic Soul Factory, by the composer Cesc Villà. Actually, all sequences were created to fit the changes in the music, something that also gave me some headaches. But I think the result was worth all the effort.

First “AAO Guerrilla Astronomy” event: partial solar eclipse on 29 April 2014 over Sydney Harbour

Last Tuesday 29th April the Earth, the Moon, and the Sun aligned to produce one of the most spectacular astronomical phenomena we can see: a solar eclipse. The 29th April solar eclipse was actually not a total eclipse (i.e., the disc of the Moon didn’t cover all the disc of the Sun) but an Annular eclipse. The annular phase could be only visible in Antarctica, but a partial solar eclipse was seen throughout Australia in the late afternoon. More information about this solar eclipse can be found in the NASA Eclipse Website managed by the astrophysicist Fred Espenak.

The Sun would be eclipsed by the Moon during the sunset, it was then a perfect opportunity to get some nice photos of the eclipsed Sun with some famous buildings such the Sydney Opera House or Sydney Harbour Bridge. With this excuse, but also with the idea of showing the wonders of Nature to the public, a group of astrophysicists working at Australian Astronomical Observatory (AAO) decided use this solar eclipse to organize our first “Guerrilla Astronomy” event (*). The aim of these activities is to set up amateur telescopes in a public area (a park or a shopping center) and explain to the public who is around what Astronomy is, what astronomers do, and what the “Australian Astronomical Observatory” is. More of these events are coming in the future, but this was our first “test” to see how we can organize and manage the activity.


Participants to the first AAO “Guerrilla Astronomy” Event. From right to left, Stuart Ryder (AAO/AusGO), Kyler Kuehn (AAO), Paola Oliva-Altamiro (Swinburne/AAO) and Ángel R. López-Sánchez (AAO/MQ). The laptop shows the only good image we could get of the eclipse using my telescope. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain, 29 Apr 2014.
Photo Credit: Stuart Ryder (AAO/AusGO).

Given the time and position of the Sun during the eclipse, we decided that a really nice spot to prepare our telescopes would be Mrs Macquarie Chair point, in the Domain, Sydney Botanic Gardens. From there a very dramatic view of the Sydney Opera House and the Sydney Harbour Bridge is seen. We first requested permission to do this to the authorities of the Domain, who were really nice and even allowed us to park by free. Actually, they also came along to see the eclipse and they liked our idea of organizing more “Guerrilla Astronomy” events there in the nearby future.


All set up for eclipse: two telescopes (Stuart’s at the right, mine at the left), the AAO banner, my laptop and camera to take photos through the telescope, the eclipse glasses and extra information about the eclipse to give to the visitors. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain, 29 Apr 2014.
Photo Credit: Ángel R. López-Sánchez (AAO/MQ).

It was four of us, Stuart Ryder (AAO/AusGO), Kyler Kuehn (AAO), Paola Oliva-Altamiro (Swinburne/AAO) and myself, who participated in this first “Guerrilla Astronomy” event. Just to have everything ready on time, we were setting up telescopes, AAO banner and laptop around an hour before the beginning of the eclipse. The weather seemed very clear in the morning, but in the afternoon, as we feared, some clouds started to arrive from the west. We already knew this would be a killer… but we had to try!


Kyler and visitor using the solar glasses. First AAO “Guerrilla Astronomy” Event: partial solar eclipse on 29 April 2014 over Sydney Harbour. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain.
Photo Credit: Paola Oliva-Altamiro (Swinburne/AAO).


Little girl using the eclipse glasses. First AAO “Guerrilla Astronomy” Event: partial solar eclipse on 29 April 2014 over Sydney Harbour. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain.
Photo Credit: Paola Oliva-Altamiro (Swinburne/AAO).


Visitors, but clouds please go away! First AAO “Guerrilla Astronomy” Event: partial solar eclipse on 29 April 2014 over Sydney Harbour. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain.
Photo Credit: Paola Oliva-Altamiro (Swinburne/AAO).

We actually were a bit lucky at the beginning, and hence we could see the Sun within thin clouds and follow the eclipse for 10 minutes. I even could take a nice image:


Partial Solar Eclipse from Sydney on 29 Apr 2014. Telescope Skywatcher Black Diamond D = 80 mm, f = 600 mm + CANON EOS 600D at primary focus + Solar filter. Just 1 frame at ISO 400, 1/8 s, colour processing using Photoshop. 29 April 2014 @ 16:20 AEST ( 06:20 UT ). First AAO “Guerrilla Astronomy” Event: partial solar eclipse on 29 April 2014 over Sydney Harbour. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain.
Photo Credit: Ángel R. López-Sánchez (AAO/MQ).

After that, thick clouds arrived and this happened:

5-seconds timelapse video obtained combining 25 images taken with Telescope Skywatcher Black Diamond D = 80 mm, f = 600 mm + CANON EOS 600D at primary focus + Solar filter, at ISO 400, 1/8 s, showing how the clouds completly cover the eclipsed sun. 29 April 2014 @ 16:20 AEST ( 06:20 UT ). The direct link to the YouTube video is here.
Credit: Ángel R. López-Sánchez (AAO/MQ).

Once the Sun was completely covered by thick clouds we just waited and hoped for a little gap, but unfortunately this never happened and we didn’t see the Sun again that day.


Stuart and his telescope, Kyler and visitors, all hoping the clouds go away. First AAO “Guerrilla Astronomy” Event: partial solar eclipse on 29 April 2014 over Sydney Harbour. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain.
Photo Credit: Paola Oliva-Altamiro (Swinburne/AAO).


The eclipsed sun is setting behind those think clouds. First AAO “Guerrilla Astronomy” Event: partial solar eclipse on 29 April 2014 over Sydney Harbour. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain.
Photo Credit: Ángel R. López-Sánchez (AAO/MQ).

Well, it would have been really nice to see the eclipsed sun setting over the Sydney Harbour Bridge and sinking later close to the Sydney Opera House, I’m sure the images and time-lapse video would have been quite spectacular, but the best I got was this image:


An eclipsed sun should be setting around there… Imagen taken using a Telescope Skywatcher Black Diamond D = 80 mm, f = 600 mm + CANON EOS 600D at primary focus. First AAO “Guerrilla Astronomy” Event: partial solar eclipse on 29 April 2014 over Sydney Harbour. Mrs Macquarie Chair, Sydney Botanic Gardens / Domain.
Photo Credit: Ángel R. López-Sánchez (AAO/MQ).

In any case, all four AAO participants were very happy about how the event was and, as I said, we are expecting to repeat these “Guerrilla Astronomy” activities in the nearby future.

Next solar eclipse to touch Australia will be on 9 March 2016, but it will also be a partial eclipse only visible on the northern and western parts of the continent. The next total eclipse to be seen from Australia will happen on 20 April 2023 and it will just touch the coast of Western Australia. We have to wait until 22 July 2028 to see a total solar eclipse in Sydney. Actually, Sydney is almost exactly in the center of the totality.

More photos of this event can be found in this Flickr Album.

(*) Note that the word “Guerrilla” comes from Spanish, however the name didn’t come from me but from an idea my colleague Amanda Bauer (AAO Outreach Officer) had some months ago. As a native Spanish speaker I have to confess it is really hard to hear the pronunciation of “Guerrilla” following English phonemes as “Guerrilla Astronomy” sounds almost identical toGorilla Astronomy“. I would encourage to try to pronounce “Guerrilla” as it is said in Spanish (geˈri.ʝa) to be released of this confusion, but of course that is only my modest suggestion than can be completely ignored…

SN2014J in M82 observed at the William Herschel Telescope

A week ago, on January 21st, the English astrophysicist Steve Fossey gave a telescope workshop for a group of undergraduate students (Ben Cooke, Tom Wright, Matthew Wilde and Guy Pollack) belonging to the University College of London (UCL). As usually happens in the British capital, the sky was practically covered by clouds. However, Fossey and his students used the automatic 35 cm telescope of the University of London Observatory to spot the famous starburst galaxy M 82. Located at 12 million light-years away in the constellation of Ursa Major (The Big Dipper), the galaxy M 82 hosts an intense star-formation burst, being its light dominated by young, hot, massive, blue stars. As consequence of this frenetic activity, M 82 possesses long jets of hot gas that has been expelled from the center of the galaxy. Therefore, it is not casual that the students chose this galaxy as a target for their assignment. While Fossey was centering the galaxy in the field of the telescope he realized that there was a bright star which should not be there. They checked that this new star was real using another telescope of the Observatory. As clouds were approaching, they quickly took some few images in different filters. The first analysis was doubtless: they had just discovered a supernova in the galaxy M 82.


Discovery image of type Ia SN2014J in the starburst galaxy M82 (below) compared with an older image of the galaxy before the supernova exploded (top). The discovery image was obtained at 19:20 UT, 21st January 2014 using the automatic 35 cm telescope of the University of London Observatory.
Credit: UCL/University of London Observatory/Steve Fossey/Ben Cooke/Guy Pollack/Matthew Wilde/Thomas Wright

In just one day, amateur astronomers and professional astrophysicists used their telescopes to study M 82. These observations soon confirmed the discovery made by Fossey and his students. Actually, some astronomers even found that they had taken data of the galaxy and the supernova a week before the official discovery, but the new exploding stars was unnoticed by them. A couple of days after the discovery, a group of astrophysicists led by Yi Cao (Caltech) got the first optical spectrum of the supernova using the 3.5m ARC Telescope at Apache Point Observatory (New Mexico, USA). The analysis of this spectrum showed that the progenitor of the supernova was a white dwarf, and hence the explosion was classified as a type Ia supernova. The official name of this exploding star is SN 2014J. It has not reached its maximum brightness yet: when Fossey and his students discovered the supernova, it was 2 weeks before when we expect this happens. Right now it is so bright (around 10th magnitude) it is very easy to spot using a small amateur telescope. Perhaps even it can be seen using binoculars when the supernova reaches its maximum brightness in a week or so!

Hence, it is not difficult to understand that SN 2014J and M 82 have been the main astronomical news in the last week. Using the 4.2m William Herschel Telescope (WHT), which is part of the Isaac Newton Group, located at the Roque de los Muchachos Observatory in the beautiful island of La Palma (Canary Islands, Spain), the astrophysicists Manuel Moreno-Raya (CIEMAT, Spain) and Lluís Galbany (DAS/UC, Chile) have observed with great detail both the supernova and the galaxy. Between Thursday 23rd and Sunday 26th January they used the ISIS spectrograph, as well as the ACAM instrument (Auxiliary-Port Camera), of the WHT to get images and spectra of the supernova. I was continuously in touch with them as I’m part of their research team (actually, I’m co-supervising the PhD thesis which is conducted by Manu). I originally planned to travel to La Palma to be helping on these observations, however this was colliding with my support activities at the Anglo-Australian Telescope (Siding Spring Observatory, NSW, Australia). Manu and Lluís sent me the data as they were coming from the WHT, and I was reducing, combining, and getting the preliminary images and spectra of this object!

The image below shows the supernova SN 2014J and the galaxy M 82 using the data obtained with ACAM. I tried to get all the important details of this puzzling object: the dust lanes crossing the disc (dark-yellow), the strong star-formating bursts (blue) and even the filamentary structure of the super-galactic wind that M 82 possesses (in red). This feature is hot, ionized gas which has been expelled from the center of the galaxy and here it is seems perpendicular to the galactic disc. SN 2014J very brightly shines at the west (right) of M 82 galactic center.


Colour image of starburst galaxy M 82 with the type Ia supernova SN 2014J. M 82 lies at 12 million light years from us, in the Ursa Major constellation. The supernova is marked with two white lines. The data needed to get this image were taken using the ACAM instrument located at the Cassegrain focus of the 4.2m William Herschel Telescope (WHT) (Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain). We got data in u, g, i, r, and Hα filters. Data coming from the u filter (2 x 200 seconds exposures) are colour-coded in blue; data in the g filter (3 x 100 seconds exposures) are colour-coded in cyan; data in the i filter (3 x 100 seconds exposures) are colour-coded in green; data in r filter (3 x 300 seconds exposures) are colour-coded in red. The majority of the data were obtained last 24th January, at 04:40 UT. Data in r and u filter were taken on 25th January, at around 06:00 UT. The Hα data (4 x 300 seconds exposures), which are colour-coded in red, were taken on 26th January at 06:30 UT. Data coming from the Hα filter clearly reveals the super-galactic wind of M 82. All data were reduced and combined using standard IRAF routines. The colour composition was obtained using Photoshop. The field of view is 8 arcminutes and the resolution 0.25 arcsec/pixels. However, the seeing was not too good, between 2 and 5 arcsec.
Credit: Observers: Manuel E. Moreno-Raya (CIEMAT, Spain) & Lluís Galbany (DAS / UC, Chile). Data processing and color image composition: Ángel R. López-Sánchez (AAO / MQ, Australia). Support astronomer: Chris Benn (ING, UK), Telescope Operator: José Norberto González (ING, UK). Research Team: Manuel E. Moreno-Raya (CIEMAT, Spain), Mercedes Mollá (CIEMAT, Spain), Ángel R. López-Sánchez (AAO / MQ, Australia), Lluís Galbany (DAS / UC, Chile),Aurelio Carnero (ON, Brazil), Inma Domínguez (UGR, Spain), & Pepe Vílchez (CSIC / IAA, Spain).

In addition, we have already analyzed the low-resolution spectrum of the SN 2014J obtained using ACAM. This spectrum gets all the optical range, between 3500 and 9500 Angstroms, and clearly identifies the object as a type Ia supernova. The main features are absorption bands of iron (Fe II and Fe III), magnesium (Mg II) and silicon (Si II) between 4000 and 5000 A. These bands actually are blends of absorptions due to these metallic elements. Indeed, astrophysicists expect the intensity of these bands will be changing as the supernova evolves, as the chemical abundances and ionization of each species vary as some elements are converted into others and more material coming from the center of the dead star is observed. Even so, it is a surprise to find these absorption bands almost 10 days before the supernova reaches its maximum brightness. The spectrum also shows absorptions of sulfur (S II) at 5240 and 5450 A, a strong absorption by silicon (Si II) at 6150 A, and absorptions of calcium (Ca II), sodium (Na I) and oxygen (O I). Some features are actually created in the Earth atmosphere and hence they do not belong to the supernova, these are labelled as “Tel” (from “Teluric lines”). However, the feature which interested us most was the carbon absorption (C II) at 6580. This line indicates that the progenitor of the supernova was a white dwarf composed by carbon and oxygen (as it happens in the majority of the white dwarf). However, it is uncommon to observe this line in type Ia spectra. This suggests that the surface of the white dwarf has not been completely burnt during the explosion. All absorption lines are found “blue-shifted”, that is, at shorter wavelengths that those expected. That is a consequence of the high speed at which the material is moving, expanding fast away from the dead star. The measurement of the C II and S II lines observed in our ACAM optical spectrum indicates that this material is moving at around 15 000 km/s!


Low-resolution optical spectrum of the type Ia supernova SN 2014J discovered in the galaxy M 82 obtained using the ACAM instrument at the Cassegrain focus of the 4.2m William Herschel Telescope (WHT) (Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain). The intensity or relative flux (“Arbitrary Flux”, vertical axis) is plotted versus wavelength (“colour”, horizontal axis). The main features, which includes absorption lines of iron, magnesium, silicon, sodium, calcium, oxygen and carbon, are labelled. The spectrum combines two expositions of 200 seconds each using the ACAM V400 grism. The data were obtained last 25th January at 7:10 UT, which approximately corresponds to Epoch -11 days. It is expected the supernova reaches its maximum brightness in that time. The reduction of the data and the wavelength calibration was performed using standard IRAF routines.
Credit: Observers: Manuel E. Moreno-Raya (CIEMAT, Spain) & Lluís Galbany (DAS / UC, Chile). Data processing and color image composition: Ángel R. López-Sánchez (AAO / MQ, Australia). Support astronomer: Chris Benn (ING, UK), Telescope Operator: José Norberto González (ING, UK). Research Team: Manuel E. Moreno-Raya (CIEMAT, Spain), Mercedes Mollá (CIEMAT, Spain), Ángel R. López-Sánchez (AAO / MQ, Australia), Lluís Galbany (DAS / UC, Chile),Aurelio Carnero (ON, Brazil), Inma Domínguez (UGR, Spain), & Pepe Vílchez (CSIC / IAA, Spain).

Interestingly, the project that Manuel Moreno-Raya (CIEMAT, Spain) and his research team, composed by Mercedes Mollá (CIEMAT, Spain), Lluís Galbany (DAS / UC, Chile), Aurelio Carnero (ON, Brazil), Inma Domínguez (UGR, Spain), Pepe Vílchez (CSIC / IAA, Spain) and myself, was observing at the WHT was focused in obtaining deep, high-quality data of galaxies hosting type-Ia supernova. The idea is to quantify the physical and chemical properties of these host galaxies with the final aim of getting a better understanding of the parameters which control the brightness of these supernovae and apply these new measurements to improve the accuracy to very distant galaxies. This research is the main part of the PhD thesis project that Manu is conducting. Besides the observations of M 82 and the SN 2014J, we also got deep intermediate-resolution optical spectroscopy data of around 20 galaxies. These data still have to be analyzed in detail, something that will take months.

SN 2014J is the type-Ia supernova closest to the Earth since that Johannes Kepler observed in 1604. The Kepler’s Supernova actually exploded in our Galaxy, at just 20 thousands light-years from us, and it was so bright it was seen with the naked eye, being the brightest object in the sky after the Sun and the Moon. The type Ia supernova SN 1972e was also very close to us, as it exploded in the dwarf galaxy NGC 5253 (*). NGC 5253, which lies at a distance of 13 million light years, is in some way a similar object to M 82, as it also hosts a very powerful star-formation event. SN 1972e became the prototype object for the development of theoretical understanding of Type Ia supernovae, but this position may change with all the data that are coming from SN 2014J. What surprises will provide this new supernova? Can the new data be used to get a better understanding of the type Ia supernovae as a cosmological distance estimators and help to discover the nature of the mysterious dark energy which induces the expansion of the Universe? This research has just started.

UPDATE: Part of the information included in this post was used to prepare a telegram for ATel, The Astronomer’s Telegram, number 5827, Broad and narrow band imaging and spectroscopic follow up of SN2014J in M82, published on 28 Jan 2014; 18:30 UT.

(*) I should tell you many more things about the dwarf galaxy NGC 5253… It was my nightmare for some few years and after performing a very complete and detailed multi-wavelength analysis of this weird object I’m still not sure what is happening in there!

Feeding, Feedback and Fireworks in galaxies

During this week (23 – 28 June 2013), I’m participating in the international astrophysics conference “Feeding, Feedback, and Fireworks: Celebrating Our Cosmic Landscape”, which is hosted in the tropical paradise of Hamilton Island, one of the most important islands of the Whitsundays (Queensland, Australia). The conference is jointly supported by the Australian Astronomical Observatory (AAO) and the CSIRO Astronomy and Space Science (CASS) and it is the 6th of the Southern Cross Conference Series.

Poster of the “Feeding, Feedback, and Fireworks: Celebrating Our Cosmic Landscape”, jointly supported by the Australian Astronomical Observatory (AAO) and the CSIRO Astronomy and Space Science (CASS), being the 6th of the Southern Cross Conference Series. The Heart Reef near Hamilton Island appears in the foreground, while the Hubble Ultra-Deep Field image is the background image.
Credit: Heart Reef Photo and Fireworks: Ángel R. López-Sánchez (Australian Astronomical Observatory / Macquarie University); Hubble Ultra-Deep Field: NASA, ESA and R. Thompson (Univ. Arizona).

It has been a very intense and fruitful conference, with almost 100 participants (the majority coming from Australia, but many others from America, Europe, Asia and Africa), and we are discussing hot topics about how the diffuse gas is moved inside the galaxies (Feeding), how stars form in galaxies (Fireworks) and how these newborn stars alter the properties of their host galaxies and their surroundings (Feedback). We are also investigating the role of the Active Galactic Nuclei (AGN) in galaxy evolution: how are they triggered (Feeding) and how they affect their host galaxies and even the galaxy cluster their host galaxies reside (Feedback). All in the context of the cosmological evolution of the Universe, constraining theoretical models using observations, and trying to put all the pieces together to understand the evolution of the galaxies.

In my case I presented part of my multi-wavelength work in Blue Compact Dwarf Galaxies, which are small galaxies (smaller than 1/100 times the size and mass of the Milky Way) which are experiencing a very intense star-formation event. Hence, it seems all the dwarf galaxy is a giant nebula! I’ll describe these interesting objects in a future post.

I’m part of the “LOC”, the Local Organizing Committee, which is chaired by Amanda Bauer (AAO), aka @astropixie, and hence in the last months I have actively participate to get the conference smoothly running (conference booklet, schedule of the talks, helping in registration and photos). One of my tasks during this week was to get the “Conference Photo” which, as Amanda suggested, includes not only the beach and palm trees of the beautiful beach at Hamilton Island but also a nice night-sky photo showing the Southern Cross. The result is this:

Conference Photo of the “Feeding, Feedback, and Fireworks: Celebrating Our Cosmic Landscape” conference.
Photo Credit and composition: Ángel R. López-Sánchez (Australian Astronomical Observatory / Macquarie University).

The talks and more information about this exciting conference will be posted in the conference webpage soon.