Tag Archives: gaia

Streams, streams, streams


For my presentation at the Gaia Challenge in Heidelberg, I made a quick ADS search for publications on tidal stream observations since their first discovery in 1995 by Carl Grillmair. Although tidal streams had been theoretically predicted before 1995, Grillmair showed for the first time that some star clusters have significant amounts of stars outside their tidal radii. At about the same time, the Sagittarius (Sgr) dwarf galaxy was discovered by Rodrigo Ibata, and people started finding patches of stars that belong to the stream emanating from this galactic satellite everywhere in the halo of the Milky Way. It took 6 more years until Michael Odenkirchen showed with commissioning data of the Sloan Digital Sky Survey that the globular cluster Palomar 5 has a coherent stream emanating from its Lagrange points out into the tidal field of the Milky Way. This publication also marked the onset of survey since in astronomy. Since 2000/2001 the rate of papers presenting new observational results on streams in the Galactic halo or around other galaxies grows exponentially. While this growth was initially driven by studies on the Sgr stream (red cumulative curve above), the focus is now shifting towards fainter streams like Palomar 5, NGC 5466 or GD-1 (blue curve). It’s a really exciting time to work in this field!


Gaia Challenge 2014


End of October, I was in Heidelberg to attend the Gaia Challenge workshop at the Max Planck Institute for Astronomy (MPIA). This workshop series was initiated last year by Justin Read, Mark Gieles and Daisuke Kawata at the University of Surrey (Guilford, south of London). This year we came together again, but this time the meeting was organized by Glenn van de Ven, who is a research-group leader at the MPIA. Glenn booked the Haus der Astronomie (house of astronomy) for us, which is a public outreach building on the premises of MPIA. The cool thing about it is that it’s shaped like a spiral galaxy (see photo above). The bulge of the Haus der Astronomie is a large auditorium and the spiral arms consist of seminar rooms and a child day care center. It’s quite a unique place!  Continue reading Gaia Challenge 2014

University of Surrey


After my weekend in London, I spent a couple of days in Guildford, which is like 30 min south of London. I was visiting Mark Gieles and Justin Read, who both recently took up their professorships at the University of Surrey. The two are the initiators of the Gaia Challenge workshop, which happened last August in Guildford. This year, there will be a second edition of the workshop in Heidelberg, where I’m very much looking forward to as I will be leading the stream group together with Andreea Font. In preparation for that, and as a recapitulation of the first Gaia Challenge, we started writing a collaborative paper with our stream group. The paper is going to be written publicly on Authorea, which is – like the workshop – very experimental and novel in its design and approach. On my last night in Guildford, the Surrey people took me and visiting astronomer Andrea Maccìo out for dinner to one of Jaime Oliver’s Italian restaurants. A delicious last night with British lamb, fresh mint, and great wine. As you can see in the picture, the astronomy group of Surrey University is a young and  fun mix of people. They gave me good reason to come back!