Light and Astrophysics: My post for the IYL15 blog

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.

Post originally published on 17th March 2015 in the International Year of Astronomy 2015 (IYL15) blog with the title Light and Astrophysics. The Spanish version of this article was published in Naukas.com.

Unlike the rest of sciences, Astrophysics is not based on carefully experiments designed in a laboratory but in the direct observation of the Universe. Astrophysicists get their data via the analysis of the light we receive from the Cosmos. For achieving this we use extremely sensitive instruments that collect the light emitted by planets, stars, nebulae and galaxies. Certainly, there are some alternative ways to study the Universe besides using the light, as analyzing meteorites or moon rocks, detecting energetic particles such as cosmic rays and neutrinos, or perhaps even using gravitational waves if they actually exist. But the main tool astrophysicists have today to investigate the Cosmos is the study of the radiation we receive from the outer space. Light is the key piece of the Astrophysics we make today.

As the aim is to observe the very faint light coming from objects located even billions of light years away, astronomical observatories are built in relatively isolated places, which are typically located high over the sea level. To observe the Universe, we astrophysicists need dark skies that are not affected by the nasty light pollution created by our society. The inadequate use of the artificial light emitted by streetlight of the cities induces an increasing of the brightness of the night sky. This happens as a consequence of the reflection and diffusion of the artificial light in the gases and particles of dust of the atmosphere. Besides the huge economic waste that it means, light pollution also has a very negative impact on the ecosystem, increases the amount of greenhouse gases in the atmosphere, and drastically diminishes the visibility of the celestial bodies. Unfortunately the light pollution is the reason that a large part of the mankind cannot enjoy a dark starry sky. How is the firmament when we observe it from a dark place? This time-lapse video shows as an example the sky over Siding Spring Observatory (Australia), where the Anglo-Australian Telescope (AAT), managed by the Australian Astronomical Observatory (AAO) and where I work, is located. The darkness of the sky in this observatory allows us to clearly see with our own eyes the Milky Way (the diffuse band of stars that crosses the sky) and many other celestial bodies such as the Magellanic Clouds, the Orion and Carina nebulae, or the Pleiades and Hyades star clusters.


Movie: Time-lapse video “The Sky over the Siding Spring Observatory”. More information about this video in this post in the blog. Credit: Ángel R. López-Sánchez (AAO/MQ).

On the other hand, after traveling during hundreds, millions, or billions of years throughout the deep space, the information codified in the light that reaches us is disrupted by the atmosphere of the Earth in the last millionth of a second of its trip. Hence professional telescopes are built on the top of the mountains, where the atmosphere is more stable than a sea level. Even though, many times this is not enough: our atmosphere distorts the light coming from space and prevents the identification of objects located very close in the sky. New techniques have been developed for compensating the effect of the atmosphere in the quality of the light we receive from the Cosmos. In particular, the adaptive optics technique induces in real time slight modifications to the shape of the primary mirror of the telescope, and therefore they counteract the distortion created by the atmosphere. In any case, astrophysicists need to direct the light received by the telescope to a detector, which transforms light energy into electric energy. This has been the purpose of the CCD (Charge-Couple Device) chips, firstly used by astronomers, and later popularized in smartphones and digital cameras. Very sophisticated optical systems are built to direct the light from the telescope to the detectors. Some of the systems created to manipulate our collection and processing of light are based on optical fibres. This new technology has created the branch of Astrophotonic. Indeed, the AAO, together with the University of Sydney and Macquarie University (Australia), are pioneers in the field of Astrophotonic. The next video shows how the light from the Cosmos is studied at the AAT. First it is collected using the primary mirror of the telescope, which has a diameter of 4 meters, and then it is sent using optical fibres to a dark room where the AAOmega spectrograph is located. This spectrograph, which is a series of special optics, separates the light into its rainbow spectrum, in a similar way a prism separates white light into a rainbow. The separated light is later focussed onto the CCD detector.


Movie: Rainbow Fingerprints, showing how the light of distant galaxies in collected by the Anglo-Australian Telescope and directed to the AAOmega spectrograph using optical fibres. More information: at the AAO webpages. Credit: Australian Astronomical Observatory (AAO), Movie produced by Amanda Bauer (AAO).

Specifically, this video shows how astrophysicists analyse the light coming from distant galaxies to understand their nature and properties. In particular, the video reveals the final science quality spectra for two different types of galaxies, one spiral (top panel) and one elliptical (bottom panel), using actual data obtained with the AAT and the AAOmega spectrograph. The information codified in the rainbow fingerprint identifies each galaxy unambiguously: distance, star formation history, chemical composition, age, physical properties as the temperature or the density of the diffuse gas, and many more. All this information has been captured within a single ray of light that has travelled hundred of millions of years to reach us. Similarly, the properties of stars (luminosity, mass, temperature, chemical composition, kinematics, …), nebulae, and any other celestial body (planets, comets, asteroids, quasars, …) are analyzed through its light. And studying tiny changes in the amount of light we receive from nearby stars we are now finding thousands of exoplanets in the Milky Way.

The “rainbow fingerprints” video shown before includes only the observations of two galaxies, but actually the AAT is able to observe around 350 objects at the same time. This is achieved using the 2dF robot, which can configure 400 optical fibres within a circular field of view with a diameter of 4 full moons. The majority of the optical fibres are allocated to observe galaxies (or stars), but some few optical fibres are used to get an accurate guiding of the telescope or to obtain important calibration data. With this technology the AAT is a survey machine, and indeed it is a pioneer of galaxy surveys. Around 1/3 of all the galaxy distances known today have been obtained using the AAT. The most recent galaxy survey completed at the AAT is the “Galaxy And Mass Assembly” (GAMA) survey, that has collected the light of more than 300 thousand galaxies located in some particular areas of the sky. The next movie shows the 3D distribution of galaxies in one of the sky areas observed by GAMA. This simulated fly through shows the real positions and images of the galaxies that have been mapped by GAMA. Distances are to scale, but the galaxy images have been enlarged for a viewing pleasure.


Movie: “Fly through of the GAMA Galaxy Catalogue”, showing a detailed map of the Universe where galaxies are in 3D. More information in the Vimeo webpage of the video. Crédito: Made by Will Parr, Dr. Mark Swinbank and Dr. Peder Norberg (Durham University) using data from the SDSS (Sloan Digital Sky Survey) and the GAMA (Galaxy And Mass Assembly) surveys.

However, to really understand what happens in the Universe, astrophysicists use not only the light that our eyes can see (the optical range) but all the other “lights” that make up the electromagnetic spectrum, from the very energetic gamma rays to the radio waves. The light codified in the radio waves is studied using radiotelescopes, many of them located in the surface of the Earth. The study of the light in radio frequencies allows us to detect the diffuse, cold gas existing in and around galaxies, the coldest regions of the interstellar medium and where the stars are formed, and energetic phenomena associated to galaxy nuclei hosting an active super-massive black hole in its centre. Many technological achievements, including the invention of the Wi-Fi, come from Radioastronomy. The study of the infrared, ultraviolet, X ray and gamma ray lights must be done using space telescopes, as the atmosphere of the Earth completely blocks these kinds of radiation. As an example, the next image shows how the nearby spiral galaxy M 101 is seen when we use all the lights of the electromagnetic spectrum. Light in X rays traces the most violent phenomena in the galaxy, which are regions associated to supernova remnants and black holes. The ultraviolet (UV) light marks where the youngest stars (those born less than 100 million years ago) are located. Optical (R band) and near-infrared (H band) lights indicate where the sun-like and the old stars are found. The emission coming from ionized hydrogen (H-alpha) reveals the star-forming regions, that is, the nebulae, in M 101. Mid-infrared (MIR) light comes from the thermal emission of the dust, which has been heated up by the young stars. Finally, the image in radio light (neutral atomic hydrogen, HI, at 21 cm) maps the diffuse, cold, gas in the galaxy.

Imagen: Mosaic showing six different views of the galaxy M 101, each one using a different wavelength. Images credit: X ray data (Chandra): NASA/CXC/JHU/K.Kuntz et al,; UV data(GALEX): Gil de Paz et al. 2007, ApJS, 173, 185; R and Hα data (KPNO): Hoopes et al. 2001, ApJ, 559, 878; Near-Infrared data (2MASS): Jarrett et al. 2003, AJ, 125, 525, 8 microns data (Spitzer): Dale et al. 2009, ApJ, 703, 517; 21cm HI data (VLA): Walter et al. 2008, AJ, 136, 2563, ”The H I Nearby Galaxy Survey”. Credit of the composition: Ángel R. López-Sánchez (AAO/MQ).

In any case, today Astrophysics does not only use observations of the light we collect from the Cosmos, but also includes a prominent theoretical framework. “Experiments” in Astrophysics are somewhat performed using computer simulations, where the laws of Physics, together with some initial conditions, are taken into account. When the computer runs, the simulated system evolves and from there general or particular trends are obtained. These predictions must be later compared with the real data obtained using telescopes. Just to name some few cases, stellar interiors, supernova explosions, and galaxy evolution are modeled through careful and sometimes expensive computer simulations. As an example, the next movie shows a cosmological simulation that follows the development of a spiral galaxy similar to the Milky Way from shortly after the Big Bang to the present time. This computer simulation, that required about 1 million CPU hours to be completed, assumes that the Universe is dominated by dark energy and dark matter. The simulation distinguishes old stars (red colour), young stars (blue colour) and the diffuse gas available to form new stars (pale blue), which is the gas we observe using radiotelescopes. This kind of cosmological simulations are later compared with observations obtained using professional telescopes to progress in our understanding of the Cosmos.

Movie: Computer simulation showing the evolution of a spiral galaxy over about 13.5 billion years, from shortly after the Big Bang to the present time. Colors indicate old stars (red), young stars (white and bright blue) and the distribution of gas density (pale blue); the view is 300,000 light-years across. The simulation ran on the Pleiades supercomputer at NASA’s Ames Research Center in Moffett Field, Calif., and required about 1 million CPU hours. It assumes a universe dominated by dark energy and dark matter. More information about this animation in this NASA website. Credit: F. Governato and T. Quinn (Univ. of Washington), A. Brooks (Univ. of Wisconsin, Madison), and J. Wadsley (McMaster Univ.).

In summary, thanks to the analysis of the light we know where stars, galaxies, and all the other celestial bodies are, what are they made of, how do the move, and more. Actually, much of the research that we astrophysicists do today combines observing and analyzing light coming from very different spectral ranges, X rays, ultraviolet, optical, infrared and radio waves. In many cases, we are using techniques that have been known for only few decades and that are still waiting to be fully exploited. The detailed study of the light coming from the Cosmos will provide new important astronomical discoveries in the nearby future and, at the same time, will impulse new technologies; many of them will be applied in medicine and communications. The light techniques we are developing for Astrophysics will have a direct application to our everyday life and will improve the welfare state of our society, besides deepens the understanding of the vast Universe we all live in.

Aluminising the Anglo-Australian Telescope

My colleague Andy Green has just finished this really nice short film (12 minutes) showing how the re-aluminising of the 4-metre mirror of the Anglo-Australian Telescope. This procedure consists on first carefully cleaning the surface of the mirror and strip off the old reflective coating, then prepare and polish the glass surface, and finally secure the mirror inside the large vacuum chamber metal tank for aluminising. The glass surface is then covered with a really thin layer of aluminium, which only has 100 atoms thick. Of course, the mirror has to be removed from the telescope first, and has to be put back at the end. Staff at the AAT need around 1 week (5 days) to complete the process.

Film “Aluminising the Anglo-Australian Telescope”, that is available in the AAO YouTube Channel. Credit: Andy Green (AAO), Narrated by: Fred Watson (AAO), Additional video by Pete Poulus, Fred Kamphues and Ángel R. López-Sánchez (AAO/MQ).

The footage for this film was shot on location at the Anglo-Australian Telescope using a Canon 5D Mark III and a Canon 6D by Andy Green. The aerial footage of the Anglo-Australian Telescope building was filmed by Peter Poulos of iTelescope. Some additional archive footage of the telescope filmed by Fred Kamphues. The night sky sequences were obtained by me as part of my astronomical timelapses at the Siding Spring Observatory. The music was performed by the Czech National Symphony Orchestra. The pieces are “Peer Gynt Suite No. 1, Op. 46 – IV. In the Hall Of The Mountain King” composed by Edvard Grieg and “In The Steppes of Central Asia” composed by Alexander Borodin. All music is public domain, courtesy of Musopen.

More information: AAO webpages

New AAO video: Rainbow Fingerprints

Have you ever wondered how telescopes collect the light of the stars to be later analyzed by the astronomers? This new AAO video, entitled Rainbow Fingerprints shows how this is done at the Anglo-Australian Telescope (AAT). The video was produced by AAO Astronomer and Outreach Officer Amanda Bauer, and I have collaborated providing not only the sequences of the AAT outside and inside the dome (which were extracted from my timelapse A 2dF night at the AAT) but also providing comments during the production process.

Video “Rainbow Fingerprints” showing how the light of distant galaxies in collected by the Anglo-Australian Telescope and directed to the AAOmega spectrograph using optical fibres. More information in the AAO webpage Rainbow Fingerprints. Credit: AAO, movie produced by Amanda Bauer (AAO).

The light coming from distant galaxies is first collected using the primary mirror of the telescope, which has a diameter of 4 meters, and then it is sent using optical fibres (the 2dF system) to a dark room where the AAOmega spectrograph is located. This spectrograph, which is a series of special optics, separates the light into its rainbow spectrum, in a similar way a prism separates white light into a rainbow. The separated light is later focussed onto the CCD detector. Finally the video reveals the science quality spectra for two different types of galaxies, one spiral (top panel) and one elliptical (bottom panel), using actual data obtained with the AAT and the AAOmega spectrograph. The information codified in the rainbow fingerprint identifies each galaxy unambiguously: distance, star formation history, chemical composition, age, physical properties as the temperature or the density of the diffuse gas, and many more.

I hope you enjoy it!

The Anglo-Australian Telescope turns 40

On 16th October 1974, His Royal Highness the Prince of Wales formally opened the 3.9m Anglo-Australian Telescope (AAT, Siding Spring Observatory, NSW, Australia) for scientific operations. Hence the AAT (the telescope where I work) turned 40 last Thursday. We actually had some celebrations and events at the Australian Astronomical Observatory that day, including the release of this wonderful 8 min movie: Steve and the Stars,


The star of the show is Head Telescope Operator, Steve Lee, who has worked at the AAT for almost its entire 40 years of operation. Steve guides this video tour of working with the AAT, exploring how observational techniques have changed from the 1970s to today’s digital age, and the AAT’s exciting future pursuing more world-class discoveries. Famous astrophotographer David Malin co-stars the show. Some material taken from my astronomical time-lapses has been also used for this film.

After the public event for the “AAT 40th Anniversary Celebration” I couldn’t help myself and took this photo with all of us:

Photo taken at the end of the public event for the “AAT 40th Anniversary Celebration”, Thursday 16th Oct 2014. From left to right: Warrick Couch (AAO Director), Steve Lee (Head AAT Operators), Amanda Bauer (AAO Outreach Officer), David Malin (AAO famous astrophotographer) and Andrew Hopkins (Head of AAT Astro Science). Ah, yes, it is also me smiling as a little kid. Credit: Á.R.L.-S.

Happy 40th Birthday, AAT!

Visions of a Total Lunar Eclipse within clouds

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.

Last night half of the world (Eastern Asia, Australasia, Pacific and the Americas) enjoyed a total lunar eclipse. Again clouds were moving around over Sydney during all the day, I actually see the moon rising in the evening and in just few minutes moving into the clouds. The sky was almost completely covered when the eclipse started, at around 20:15 local time. I was fearing that, as it happened with the partial solar eclipse visible in Sydney last 29th April, I would not be able to get any useful image of the eclipse.

In any case, as I did for the occultation of Saturn by the Moon last May, I set up my telescope in the backyard and prepared everything for taking some photos of the event. Although I followed the eclipse almost completely, the clouds only allowed me to get good images in three occasions. These are the results:

Visions of a Total Lunar Eclipse within clouds.
8 October 2014 from Sydney. Data obtained using Telescope Skywatcher Black Diamond D = 80 mm, f = 600 mm, with a CANON EOS 600D at primary focus. The Red Moon compiles 40 frames taken at 1/3 s & ISO 800. Stacking using Lynkeos software, final processing with Photoshop. Credit: Á.R.L-S. (AAO/MQ)


It is not too much but I hope you like it. I will wait for the next total lunar eclipse to try to get the time-lapse sequence of all the event.

Dissecting galaxies of the Local Universe with the CALIFA survey

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.

The Calar Alto Legacy Integral Field spectroscopy Area (CALIFA) survey is a project that aims to obtain data of around 600 nearby galaxies using the PMAS (Potsdam Multi Aperture Spectrophotometer) instrument of the 3.5m Telescope at the Calar Alto Observatory (Almería, Spain). The CALIFA survey combines the advantages of two observational techniques: imaging (that provides detailed information on galactic structure) and spectroscopy (that reveals the physical properties of galaxies, such as their kinematics, mass, chemical composition or age). The CALIFA survey makes use of the Integral Field Spectroscopy (IFS) technique, that allows obtaining at the same time around a thousand of spectra per galaxy, hence getting simultaneously imaging and spectra of astronomical objects.

A galaxy is “dissected” in thousands small regions, each one having its particular spectrum (wavelength) when using Integral Field Spectroscopy (IFS) techniques. The result is getting a datacube: two axes (x and y) possess the spatial information (the image of the galaxy, which can also be separated in several colours) and the third axis (wavelength) keep the spectroscopic information. Credit: Marc White (RSAA-ANU).

The CALIFA Project allows not only to inspect the galaxies in detail, but it also provides with data on the evolution of each particular galaxy with time: how much gas and when was it converted into stars along each phase of the galaxy’s life, and how did each region of the galaxies evolve along the more than ten thousand million years of cosmic evolution

Thanks to these data, astronomers of the CALIFA team have been able to deduce the history of the mass, luminosity and chemical evolution of the CALIFA sample of galaxies, and thus they have found that more massive galaxies grow faster than less massive ones, and that they form their central regions before the external ones (inside-out mass assembly). CALIFA has also shed light on how chemical elements needed for file are produced within the galaxies or on the physical processes involved on galactic collisions, and it has even observed the last generation of stars still in their birth cocoon.

CALIFA “panoramic view” (also CALIFA’s “Mandala”) representation, consisting of the basic physical properties (all of them derived from the CALIFA datacubes) of a subsample of 169 galaxies extracted randomly from the 2nd Data Release. It shows 1) broad band images (top center), 2) stellar mass surface densities (upper right), 3) ages (lower right), 4) narrow band images (bottom center; emission lines: Hα [N II] 6584 Å, and [O III] 5007 Å), 5) Hα emission (lower left) and 6) Hα kinematics (upper left). The CALIFA logo is placed at the central hexagon. Credit: R. García-Benito, F. Rosales-Ortega, E. Pérez, C.J. Walcher, S. F. Sánchez & the CALIFA team.

Today, Oct 1st, the CALIFA Team (and I’m part of it) has released 400 IFS datacubes for 200 nearby galaxies, the 2nd Data Release (DR2). The data are publically available and can now be used by astronomers around the world. The second CALIFA Data Release provides the fully reduced and quality control tested datacubes of 200 objects in two different spectral configurations. Each datacube contains ~1000 independent spectra, thus in total the CALIFA DR2 comprises ~400,000 independent spectra (~1.5 millon after cube reconstruction). The scientific details of the data included in the CALIFA DR2 are described in this scientific paper lead by the Spanish astronomer Rubén García-Benito.

More information about the CALIFA survey and its DR2:

– Calar Alto Observatory Press Release: http://www.caha.es/an-unprecedented-view-of-two-hundred-galaxies-of-the-local-universe.html

– Scientific paper about CALIFA DR2: García-Benito et al. (2014): http://arxiv.org/abs/1409.8302

– CALIFA webpage: http://www.caha.es/CALIFA/public_html

– CALIFA DR2 webpage: http://califa.caha.es/DR2

Time-lapse: The Sky over Siding Spring Observatory

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.

I’ve been waiting year and a half to finally see this happening. One of the displays I prepared for the Stories from Siding Spring Observatory Photo Exhibition (that was organized by staff of the Australian Astronomical Observatory (AAO) and originally released on 17th April 2013 at the Sydney Observatory), was a new time-lapse video compiling scenes showing all the telescopes at the Siding Spring Observatory (Coonabarabran, NSW, Australia) before the terrible bushfires that destroyed the Warrumbungle National Park and seriously affected the very same Observatory on 13th January 2013. However I couldn’t do this time-lapse video public until today, as it is the very first video to be included in the AAO Youtube channel. So here it is the time-lapse video “The Sky over Siding Spring Observatory:

Video time-lapse The Sky over Siding Spring Observatory. To enjoy it as its best, I strongly recommend you to see it at its highest resolution (FullHD) and full screen in a dark room. Credit: Video Credit: Ángel R. López-Sanchez (AAO/MQ), Music: Point of no return (Rogert Subirana).

I think this is the best time-lapse video I have created so far. It last 4:30 minutes and it compiles the best time-lapse sequences I obtained at Siding Spring Observatory between August 2011 and March 2013, during my support astronomer duties for the 4-metre Anglo-Australian Telescope (AAT). Telescopes at Siding Spring Observatory featured include the Uppsala Near Earth Object Survey Telescope, the UNSW Automated Patrol Telescope, the 2.3m ANU Telescope, 1.2m Skymapper ANU, the 1.2m UK Schmidt Telescope (AAO) and the very own Anglo-Australian Telescope (AAT).

Throughout the video, watch for several astronomical objects: our Milky Way Galaxy, the Large and Small Magellanic Clouds, the Moon rising and setting, the planets Venus, Mars, Jupiter and Saturn, Zodiacal Light, Earth-orbiting satellites, airplanes crossing the sky, the Pleiades and Hyades star clusters, the Coalsack and the Carina nebulae, and famous constellations like the Southern Cross, Taurus, Orion, and Scorpio.

The time-lapse technique consists of taking many images and then adding all to get a movie with a very high resolution. In particular, the camera CANON EOS 600D and two lenses (a 10-20 mm wide-angle lens and a standard 35-80 mm lens) were used to get the frames of this time-lapse video. Except for those frames taken during the sunset in the first scene, frames usually have a 30 seconds exposure time, with a ISO speed of 1600. Some few scenes were shot using 15 or 20 seconds exposure time. All sequences were created at 24 fps (frames per second), and hence a second in the movie corresponds to 12 minutes in real time for the majority of the scenes. In total, the video combines around 5800 individual frames. Processing each 10 – 20 seconds sequence took between five and six hours of computer time. Care was taken to remove artifacts and hot pixels from individual frames, minimize background noise, and get an appropriate colour/contrast balance.

I hope you like it. Comments and posting about it in social media are very welcome.

More information and previous time-lapses

-Video in the AAO YouTube Channel.

AAO Webpage: Timelapse Video: The Sky Over Siding Spring Observatory (25th Sep 2014)

Timelapse video: The Sky over the Anglo-Australian Telescope (3rd May 2013).

Timelapse video: A 2dF night at the Anglo-Australian Telescope (7th May 2014).