During this week I’m curator of the @astrotweep, a Twitter account that each week features an astronomer or planetary scientist taking about their research, science and life. I’m having a lot of fun with it, although I have to recognize it is extra work.
I chose to do it this week because there are some few things happening. In particular, I’m supporting observations at the Anglo-Australian Telescope (Siding Spring Observatory, NSW, Australia) using the 2dF / HERMES instruments. I thought it would be nice to be tweeting life how observations are doing. And that is precisely what I’ve doing today.
On top of that, “this morning” I had an idea. As we always have some “free time” at the AAT after completing the “2dF first night setup” (1) I decided to observe a nice bright deep sky object and get a nice image with the AAT. I was starting to search for a suitable target, but then I though, why don’t I ask the public what do they want to observe?
After consulting with my supervisors and getting the OK to do this, I initiated a poll in both @astrotweeps and @AAOastro asking the public to vote for one of the four following astro objects:
But surprises didn’t end here. In the afternoon, when I was starting to prepare the instruments for the night (I’m conducting observations remotely from Sydney), I explained to astronomers and technicians at the AAT what we were doing. Rob Paterson, our afternoon technician, then told me “Do you know we already have the new CCD camera installed in 2dF and just waiting for testing it?”
Let me explain why I was so excited when I heard this. For years the 2dF instrument has had an auxiliary camera, the FPI camera, that we use for properly positioning 2dF in the requested field. Rarely it has been used for science, as it is just a 516×516 pixels camera without filters. Occasionally I have also used it for getting some images of deep sky objects. But, as it has no filters, I had to get the color of the images elsewhere, usually taking archive data taken with other telescopes. But the new CCD camera in 2dF does have filters!
Rob phoned Steve Lee, the head of the Night Assistants at the AAT, and with Bob Dean the three of them managed to prepare CACTI (that is the name of the new camera) to have it ready for us.
Although there is still a lot to be done and tests to be conducted, the very first images I got this evening are quite promising. Here is the final result:
Spiral galaxy NGC 4027 located at around 75 million light years in Corvus (The Crow). This barred spiral galaxy, also identified as Arp 22, is identified as a peculiar galaxy by the extended arm, thought to be the result of a collision with another galaxy millions of years ago. This image is the “First Light” of the new CACTI camera in 2dF @ 3.9m Anglo-Australian Telescope. Color image using B (4 x 120 s, blue) + V (6 x 60 s, green) + R (6 x 60 s, red) filters. The data were taken on 11 May 2016 as part of an “outreach exercise” via social media. Click here to get a higher resolution image. Credit: Ángel R. López-Sánchez (AAO/MQ) & Steve Lee, Robert Paterson & Robert Dean (AAO). Night assistant at the AAT: Andre Phillips (AAO).
Note that this image, that actually is the “first light” of the CACTI camera, only combines 6 minutes in V and R and 8 minutes in B, that is, it is not deep at all. Furthermore not extra calibrations were taken (some flatfield images would have been nice). The deep image obtained by the 3.6m NTT telescope (ESO La Silla Observatory, Chile) provides many more details and resolution… but of course they were using the EFOSC instrument, which was specifically designed for deep imaging in optical filters. And the image of NGC 4027 obtained by David Malin (AAO) using photographic plates at the AAT in 1982 is much more colorful.
But I still think it is a pretty result, particularly as this new image of NGC 4027 was obtained as a completely improvised “outreach exercise” using social media, in which 153 people voted for their favorite object to be observed at the 3.9m Anglo-Australian Telescope.
I really hope to repeat this exercise soon.
(1) A 2dF Plate must be configured with a scientific field, that is, allocating ~350 optical fibres to different objects in the sky. This takes ~ 20-30 minutes.
(2) Just to provide the details of the votes, see table below:
Nice image of the starburst spiral galaxy NGC 3310 in the Ursa Major obtained with the 8.2m Gemini North Telescope in Hawaii (U.S.A.). This image was obtained for the “Cosmic Poll” contest organized by the International Telescopes Support Office at the Australian Astronomical Observatory (AAO) and appeared as APOD on 1st March 2016. Colours codify the light received in blue (B, blue) and red (R, green) filters, plus the emission of the ionized gas (Hα filter) coded in red.AAO ITSO Office, Gemini Obs./AURA & T. A. Rector (U. Alaska Anchorage).
NGC 3310 lies at a distance of around 50 million years from us, within stars of the Northern constellation of the Ursa Mayor (meaning we cannot see it here from Australia, well, it has a maximum elevation of ~5 degrees from Siding Spring Observatory). The spiral structure in NGC 3310 looks like what we expect for our own Milky Way galaxy, with plenty of star-forming regions (in red-pink colours tracing the Hα emission). However in the case of NGC 3310, the star-formation activity seems to be more extreme.
It seems that NGC 3310 started experiencing an interaction with a dwarf galaxy around 100 million years ago. This interaction has triggered a very strong star-formation event (that is why NGC 3310 is defined as a starburst galaxy), and has “broken” the external areas of the galaxy as consequence of the intense tidal forces. In the image, all regions showing red-pink colours (tracing Hα emission) are nebulae. These regions are found almost everywhere within NGC 3310, sometimes even forming some peculiar alignments of red-pink-ish regions as that “ray” that goes from the centre of the galaxy till the upper left corner. It is interesting to note that, although the interaction with the dwarf galaxy happened ~100 million years ago, the fact of finding this large amount of Hα emission informs that the star-formation activity is still important today. The colliding dwarf galaxy was probably engulfed by NGC 3310, its remaining debris could be that diffuse arc-like structure we observed in the outskirts of the galaxy in the upper part of the image.
These are the kind of objects (starburst galaxies) and the kind of features (enhanced Hα activity, tidal distortions of the stellar component of the galaxy, tails, rays…) I studied in a sample of dwarf galaxies for my PhD Thesis (I still have to tell all of that here…).
Beside tracing the nebular (Hα) emission, the image also allows to distinguish that the majority of the stars in NGC 3310 have blue colours, even in its external areas. Again, this fact informs that the dominant stellar populations in this galaxy are relatively young, as only young stars emit a lot of light in blue and ultraviolet colours.
Although it was not said in the APOD I would like to remark that the idea of observing this galaxy in the 8.2m Gemini North Telescope came from the International Telescopes Support Office at the Australian Astronomical Observatory (AAO). In particular, mi colleagues Elaina Hyde, Richard McDermid, Caroline Foster-Guanzon and Stuart Ryder (AAO) organized a very interesting outreach initiative, the Cosmic Poll, asking the people to emit a vote for which kind of object would they like to be observed at the 8.2m Gemini Telescope. The winning entry was “an individual galaxy”, and later they decided to observe NGC 3310. Furthermore they organised an on-line event,a live-stream with the Gemini North Telescope (is available on YouTube) explaining how the telescope works and giving details of the observatory. The Gemini Observatory website also included this in its blog. After processing and cleaning the images, the final result is that you see in APOD.
I couldn’t help myself, though, and decided to play a bit with the colours, levels, contrast and lights of the image to try to get an enhanced image of this very nice object. In my opinion, the central part of the galaxy is a bit too bright (it should be, of course, the real difference in brightness between the central part of NGC 3310 and the diffuse stellar streams in its outskirts is several orders of magnitude, but for illustration purposes I have found that it is a good idea to minimize that) and the outskirts of the galaxy are not that easy to see. So here it goes my enhanced image of NGC 3310 with Gemini North:
Comparison between the image of the starburst spiral galaxy NGC 3310 obtained by the 8.2m Gemini North Telescope and published in APOD on 1st March 2016 (left) and the same image enhanced by myself (right). Credit: AAO ITSO Office, Gemini Obs./AURA & T. A. Rector (U. Alaska Anchorage), Enhancement: Ángel R. López-Sánchez (AAO/MQ)
Last November some friends of the new Sydney on-line magazine A-star, Ryan Wittingslow and Harry Simpson, visited Siding Spring Observatory (Coonabarabran, NSW) to prepare a documentary about Astronomy and the telescopes at site. This is the nice video they have released, entitled Space is just totally big and amazing:
As it happened while I was supporting astronomical observations at the Anglo-Australian Telescope (AAT), I was interviewed as part of the video. Although I talked about some few things (my research, my job at the AAO and my times as a young amateur astronomer in Spain), they only used my comments about astrophotography. Indeed, they asked me to include some scenes of my astronomical time-lapses on the documentary, and I think the result is great. I really love to see my astro photos and videos so well used. Thanks Ryan and Harry for this report!
DPENGLISH: 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.
DPESPAÑOL: 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.
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.
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.
A/Prof. Ángel R. López-Sánchez 