Eight Minutes Old

After having hosted the Blog-Telescope recently, I will try to point you to the future ones, too. Today, you find it over at austroscepticus, where Christian takes you to space with the Blog-Teleskop. (Everything in German, though).

Tags: Blogteleskop, Astronomy, Blog Parade, Blog Specific, Science, Telescope

There it is finally. Our article about dwarf galaxies and dark matter has been published in the current issue of the German popular science magazine “Spektrum der Wissenschaft“, which is the German version of the Scientific American. The text  is about testing the current cosmological standard model using the satellite galaxies of the Milky Way. In it, my professor, Pavel Kroupa, and I not only describe how predictions of the Cold Dark Matter model can be compared to the Local Group of neighboring galaxies, but also how new doubts in the existence of dark matter arise from the failed tests. The article is even mentioned on the front page and in the editorial and got 10 full pages, which is a lot.

New food for your feed-reader!

While the article is in German, we also have to offer something to our English readers. Spektrum der Wissenschaft has convinced us to start a new blog on the topic to allow a direct discussion. We decided that this blog should be in Englisch. It got the title “The Dark Matter Crisis - The rise and fall of a cosmological hypothesis“ and can be found at the SciLogs. Besides Professor Kroupa and me, also Anton Ippendorf, a student in our research group also working on dwarf and satellite galaxies will write posts there. Currently I am preparing a blogpost for the Dark Matter Blog on the Bullet Cluster, one of the most often heard arguments against alternative gravity theories like MOND or MOG.

Article as free PDF

If you read German, you can buy the current version of Spektrum der Wissenschaft from today on, it costs 7.40 Euro in Germany and Austria. But if you are only interested in our article, you can also download it as a free PDF.

So, now I am waiting for the reactions. Have fun with the text and our new blog!

Tags: Blog, free online-article, magazine, MOG, MOND, Pavel Kroupa, Scientific American, Spektrum der Wissenschaft, Astronomers, Astronomy, Blog Specific, Cosmology, Dark Matter, Galaxies, Gravity, popular science, Satellite Galaxies, Science, Tidal Dwarf Galaxies

Florian Freistetter von Astrodicticum Simplex hat mich gefragt, ob ich nicht einmal das Blog-Teleskop verranstalten möchte. Na klar, die Ehre nehme ich gerne an, trotz unerträglicher Hitze, die bei manch einem Blog schon zum Hitzefrei geführt hat . Somit folgt jetzt eine subjektive und unvollständige Zusammenfassung interessanter Beiträge aus den letzten beiden Wochen der deutschen Astronomie-Blogwelt.

• Florian informiert über Geldmacherei mit der Sonnenfinsternis und zeigt, wie sich das Bild, dass Kinder sich von Wissenschaftlern machen, schnell vom Stereotyp in ein realistischeres wandelt, wenn sie nur mit echten Wissenschaftlern in Berührung kommen. Ob das auch mit Erwachsenen funktioniert?
• Für den einen oder anderen Beobachter sicher interessant: der (ausführliche) Sternhimmel im Juli auf “Astrofan80’s Blog”
• Gute Neuigeiten zum Thema Lichtverschmutzung gibt es bei “Clear Skies”: Viele Kommunen wollen im Bereich Straßenbeleuchtung sparen.
• “Astronomers do it at Night” berichtet vom Baufortschritt am Heidelberger Haus der Astronomie, dessen Architektur von Spiralgalaxien inspiriert wurde.
• Auf “Go For Launch” berichtet Michael Kahn über den Workshop “Nördlingen 2010″ zu den Themen Einschlagskrater und bemannte Erforschung des Alls.
• “Meine kleine Astrowelt” hat ein Video entdeckt, dass den Einstieg in die Himmelsbeobachtung erleuchtern sollte.
• Daniel Fischer gibt einen ziemlich umfassenden Überblick über die Auswirkungen ein halbes Jahr nach Ende des Internationalen Jahres der Astronomie 2009. Respekt, das muss viel Arbeit gewesen sein …
• Leonard Burtscher von “Promotion mit Interferenzen” fragt: Warum Berufsastronom? und gibt drei gute Antworten.
• Auf “Lichtecho” findet sich ein äußerst lesenswerter Text von Stefan Taube zum Thema Wasser auf der Venus. Warum auch immer nur vom Mars sprechen?
• Ludmilla von “Hinterm Mond gleich links” schreibt über den Anfang des Universums. Nein, nicht den Urknall, sondern darüber, dass auch wir hier auf der Erde ein Teil des Universums sind. Ein Update des Milchstrassenbildes gab es dann auch noch. Ist schon spannend, wie sich die Struktur unserer Galaxie durch neue Erkenntnisse “verändert”.
• Bei cimddwc kann man das LEGO Space Shuttle bestaunen.
• Und zum Schluss wird noch ein Stern ausgeknipst, drüben bei “Himmelslichter”: In der Nacht vom 8. zum 9. Juli wird ein Asteroid eine kurze … nenne wir es Sternfinsternis verursachen.

Da ich mich im Blog auch immmer gerne mit der Fotogrfie beschäftige gibt es zum Abschluss noch Hinweise auf eine Reihe spannender Bilder: Auf “Asterythms” spielten Geduld und die richtige Position zusammen, das Ergebnis ist ein Foto vom untergehenden Mond mit einem Windrad davor. Windparks scheinen übrigens einen guten Vordergrund abzugeben, so auch für das Bild Leuchtender Nachtwolken auf “Astrofan80’s Blog”. Beeindruckende Astrofotografien von Nebeln kann hingegen Jörg vom “Heuchelheimer Himmelsfähnchen” präsentieren. Eine Vielzahl von Aufnahmen mit Astronomiebezug präsentiert Daniel Fischer stets auf seinem Blog “Skyweek Zwei Punkt Null“, da will ich gar keinen speziellen Beitrag heraus greifen.

Das war es von meiner Seite. Wer mag kann gerne noch weitere interessante Beiträge in den Kommentaren ergänzen.

Two weeks ago my professor and me were interviewed by the Deutschlandfunk, which is a big German Radio Station. The topic, of course, was the new study concerning Dark Matter. The (German) broadcast can be found online as a Podcast and in text. This week we got another Interview request, now from NDR Info. As my professor and the other Co-Author from Bonn are at a conference in the US right now, I was the only one to be interview. You can imagine this made me a bit nervous, but it turned out to be fine.

The broadcast (again in German, sorry), will be aired today between 9 and 10 pm in the NDR Info show “Logo”. It will also be available as a podcast (starting at 39:30 into the file). I am curious what it will be like.

For Monday evening I was asked to talk about the Modified Newtonian Dynamics at our institute’s Astro Club. That’s a regular (voluntary) meeting for the younger physics students*, organized by several very committed tutors. They give easy to understand (and usually German) talks and, if the weather is fine, also observe with the institute’s telescope.

After that I hope to find more time for my work again. And for some posts on black and white infrared photography (film, of course), as I have already shown you two of my infrared photos in the post about faked UFO photos. As an introduction, here is another one. It shows the Sydney Harbor Bridge.

*: Of course older students are welcome, too.

Tags: Astroclub, deutschlandfunk, Harbour Bridge, MOND, podcast, Radio, Rollei Infrared, Sydney, Astronomers, Astronomy, Australia, Bonn, Canon EOS 50E, Dark Matter, EF 24mm f/2.8, Infared Photograpy, News, Science, Students, Study, University of Bonn

As a transition stage back to some photography blogging, I’d like to point you at a documentary: “The Eye 3D“. It was produced last year, as part of the International Year of Astronomy, and shows the “life and work at cerro paranal” in the Chilenian Acatama desert, where the Very Large Telescope is located.

On their website, you can find some 3D still pictures which you can enjoy if you have one of these red/blue glasses. The trailer below is in 2D, but I think it already gives an impression.

There is a special screening of the movie today at 5 pm in 25 cinemas all over Germany and Austria (unfortunately not in Bonn )

It seems to be press-release time at the institute. Michael Marks, a friend and colleague from the research group reports on his new results. No, it is not about MOND or Dark Matter this time, but the topic is very interesting, too.

Michael performed a kind of galactic archaeology. While ha did not dig in mud or had to get dirty for his work, he was looking at extremely old objects nevertheless. The more than 12 billion year old globular clusters still contain information about the time of their formation. From that, he has deduced new insights into the formation of the Milky Way.

He looked at the correlation between age and mass of the globular clusters. While the clusters are more than 12 billion years old, their ages differ by a few hundred million years at most. But the younger ones have lost more stars than the older. From simulations, Michael knows that forces from the outside (similar to the tides on earth, but way stronger) can make a cluster loose stars. The difference in this loosing of stars between older and younger clusters thus means, that the outside forces became stronger between the times of their formation. The Milky Way grew more rapidly than previously thought. The smooth gas clod, which was going to form the galaxy, clumped within only a few million years, and these clumps then influenced the forming globular clusters.

You can get more information on the topic from the press release, or directly from the paper: “Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way“.

Tags: Astronomers, Astronomy, Galaxies, Galaxy Formation, Globular Clusters, Milky Way, Press Release, University of Bonn

Finally I can tell you why I did not have much time to blog in the past month. Besides my own paper (have no news on this yet)  I wrote a popular science article together with my professor. That article will be published in the August Edition of Spektrum der Wissenschaft, which is the German version of the Scientific American.

Furthermore, I participated in another, very important research project resulting in a probably controversial, but scientificaly very important paper. Today it got the first place of the astrophysics preprintserver listing ArXiv: “Local Group Tests of Concordance Cosmology: Towards a new paradigm for structure formation?“. The study is about a test of the predictions of the cosmological standard-model including the dark-matter hypothesis on cosmologically small scales: In the range of the Milky Way satellite galaxies. The clear result is, that the standard cosmological model fails to agree with the observations. In total, the study lists five problems, ranging from the fact that satellite galaxies with different dark matter masses unexpectedly have the same luminosity in their center, to the phase-space distribution of the Milky Way satellite galaxies.  Each one is a serious problem for a scientific theory, but taken together the situation looks catastrophic. But, I think, it is good for science in general, because that’s the way science works: A theory makes predictions, which we use to test it. If the theory fails it is falsified and we need another, better description of the world. So it looks like we need an alternative to Dark Matter, which is great because we can expect some new fascinating results from this field of research in the next years.

First author of this study is my Professor (Pavel Kroupa) from the University of Bonn in Germany. Scientists from Germany, Austria, France, Italy and Australia collaborated for this research. And I am one of them. The part of work I did was about the disc of Milky Way Satellite Galaxies, and was large enough to give me place number five in the author list. I already mentioned the disc of satellites in my post about Tidal Dwarf Galaxies, but plan to present my new results in a post soon. So stay tuned.

UPDATE: The article is published in the August issue of Spektrum der Wissenschaft, and is available as a free pdf for download, too. You can find more information on this in this post.

Tags: Scientific American, Spektrum der Wissenschaft, Test, Astronomy, Cosmology, Dark Matter, Galaxies, Galaxy Formation, Milky Way, Paper, Physics, Press Release, Research Paper, Satellite Galaxies, Science, Scientific Method, Scientific Paper, Study, Tidal Dwarf Galaxies, University of Bonn

A good friend of mine (Tobias, he occasionally comments here, too) was in Chile for several weeks, observing at the APEX telescope. It is located at an altitude of 5100 meters above sea-level. The astronomers running observations at that height have to take special care, as the air pressure is already very low. This is one reason why their Base Camp, where they sleep and live, is far away, at a much lower altitude.

Tobias shows the effect of increasing air pressure with a simple experiment: by taking a half-filled bottle down from the telescope site to the base camp (which still is at an altitude of about 2500 meters). At 5000 meters, the bottle is filled half with water and with air. The air pressure outside and inside are the same, everything looks normal:

At 4000 meters, the air pressure is higher, but the pressure inside the bottle is still the one from 5000 meters. The bottle starts deforming:

At 3000 meters, the air pressure squeezes the bottle even more …:

… until it is fully deformed at the base-camp height:

A similar effect can be observed without changing your altitude. Especially in winter, when you take an empty bottle (which, of course, has to be easily deformable) from your warm home out into the freezing air. The warm air in the bottle cools down, reducing the pressure inside. That way the bottle gets squeezed. When opening it, air streams in and equalizes the pressure, the bottle can get its shape back.

Tags: APEX, Chile, Air Pressure, Astronomy, Bottle, Physics, Simple Experiment, Telescope

I am exhausted. For several days an ugly cold plagues me, working is impossible and my personal pleasures like editing photos are so even more. It is getting better by now, slowly.
In addition I spend quite some of thoughts on the earthquake in Chile. The country might seem far away, but the world is small and Chile feels like having one of the highest astronomer densities in the world. So inevitably I think of some friends in Chile, hoping they are all right. Of some I already got news and they are well, but others have not replied yet, including a Chilenian PHD student from Conception. That city still seems to be more or less cut off from the world in terms of communications and websites are inaccessible.
Astronomers love Chile because the country offers excellent places for observations. Regions that are very high and dry are perfect places for telescopes: The thin atmosphere and no water vapour give good visibility conditions. The observatories, at least those of the European Southern Observatory ESO, remained undamaged, in part because they are far from the earthquake site. But astronomical observation plans will probably get disturbed severely, especially because of difficulties in travelling. Good that I am a theoretician, not an observer …

Tags: ALMA, APEX, Blog, Chile, Conception, ESO, Paranal, Santiago, Astronomers, Astronomy, Earthquake, Telescope

Here I am again, from Australia. I didn’t post earlier because of two reasons. First: I was overwhelmed by the palace here. The landscape around Canberra is magnificent. Especially the view from the Mount Stromlo Observatory. Due to the huge bushfire in 2003, the forest on the mountain was lost. This gives a wonderful view of the surrounding hills and of the city of Canberra. The second reason was work: I am not here as a tourist, but had to concentrate on the talk I was to give. (And squeezed in some sight-seeing, which I found more important than sitting around with my laptop in some spot where I could find free WiFi to blog, sorry. The apartment unfortunately didn’t have internet.)

Now, where shall I start? Well, I gave my talk last Friday, which was well received, with lot’s of interested questions and discussions. The discussions here have been fruitful, I had the chance to learn more about the ‘Stromlo Missing Satellites Survey’ and right now several new ideas for my future research are developing. And I gained experience in giving talks to people that don’t know me nor my work. Interestingly, there are several German-speaking scientists here, like my host who is from Switzerland originally and one of his post-docs is from Germany.

The city of Canberra, even though it is the Australian Capital, is a bit, well, sleepy. Shops close at 5 pm, the city has only a few buildings with more than one story and the streets are wide. The whole city stretches over a big area, over 800 square kilometres, while the population is only short of 350 000. Compare this to Singapore, where I have been before: It covers an area of only 700 square kilometres but has a population of about 5 million! That’s what I call a city.

One benefit of being on the opposite side of the globe, on the southern hemisphere, is the weather. We mainly have a bright blue sky, temperatures between 25 and 35 degrees and light from 6 am to 8 pm at least. Much better than the winter in Bonn, for which the weather forecast predicts freezing temperatures. Seeing Christmas decoration here, on the other hand, is a bit strange (but the Christmas tree balls are much more shiny in the direct sunlight ). And it does not feel like Christmas time. I don’t worry much about this, I usually feel annoyed by all the holiday preparations in Germany. But seeing a TV advert with the slogan “Barbeque better this Christmas” simply sounds ridiculous to me :-).

Well, enough writing for the moment. I’ve got some pictures for you:

The lanscape surrounding Canberra as seen from the Mount Stromlo.

For some signs, the heat of direct sunlight seems to be too intense …

Some of the Telescope domes on the Mount Stromlo. The right building is completly burned inside, the telescope was completely destroyed. But it is cheaper to leave the domes standing (after a new paint-job), than to remove them.

I think this is the ruin of the directors house on the Mount Stromlo. You can see the signs of the fire everywhere, even though it happened over six years ago.

A band playing christmas songs at the ‘Old Bus Depot Market’, a regular market in Canberra that is turned into the local christmasmarket in December.

The decoration for the Observatory’s Christmas party is shining in the sun.

Tags: Australian National University, Canberra, Mount Stromlo, Mount Stromlo Observatory, Australia, Bonn, Bushfire, Christmas, Observatory, Satellite Galaxies, Science, Singapore, Sky, Sun, Talk, Telescope, Travel, Southern Hemisphere