Uffe Gråe Jørgensen

Personal data:

Name: Uffe Gråe Jørgensen
Title: associate professor (Danish "lektor")

Email: uffegj@nbi.dk
Office phone: (+45) 35 32 59 98
Cellular phone: (+45) 61 30 66 40
Secretary: (+45) 35 32 59 96
Fax: (+45) 35 32 59 89

The postal address of the institute is:
Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
For historical reasons, this building of the NBI is called the Rockefeller Complex (see map: "Rockefeller_Komplekset").
My office is room 037, at the ground floor of the building to the left after entering the main entrance.

I am head of the group Astrophysics & Planetary Science and area leader ("område leder") for astronomy at the Niels Bohr Institute.


I started my scientific work with studies of molecular opacities (with my master thesis being on the absorption coefficients of HCN and C2H2), went deeper into the quantum chemistry of molecular processes, and broadened my studies to the application to cool stellar atmospheres (with my PhD thesis being on AGB stars and stellar atmospheres). In 2002 I shifted my main research area to exoplanets, inspired by the encounter with Penny Sacket and her PLANET team. Today, I am involved into instrument development of the lucky imaging technique for improved microlensing detection of small exoplanets, being in charge of the operation of the the Danish 1.54m telescope at ESO's La Silla observatory and in charge of the exoplanet research with the SONG telescope network (see recent status). Throughout most of my life I have been fascinated with the unsolved questions in science. As a teenager I started a fast growing amateur astronomical association in the Copenhagen area, participated in forming the Scandinacian association of amateur astronomy, and in building a public observatory (a description of the development of our public observatory was recently summarized in a short interview) and a Danish amateur astronomy journal. In 2009 I had the great luck to be invited to be part of the creation of a Centre of Excellence, StarPlan, at Copenhagen University, with the main goal to understand whether our own solar system is normal or something unique. A list of most of my scientific papers can be found under U.G.Jorgensen at ADS, though a few have been misplaced under Graae-Jorgensen and similar, or have been published in more physics and/or chemistry oriented journals than covered by ADS.

My main areas of research are:

Exoplanets (planets around other stars):

Since 2002 I have been involved in the search for extrasolar planets by use of the microlensing technique; untill 2008 as part of the PLANET team, and since 2008 as part of the MiNDSTEp team, which I started and organizes together with Martin Dominik. Microlensing is complementaty to the other techniques for finding exoplanets, in the sense of being particular sensitive to planets in orbits similar to those in our own solar system, say from 1 AU to 10 AU. With the present set-up of telescopes and instrumentation the technique is sensitive down to approximately Earth-mass planets (the smallest, as of 2014, being a 1.6 Earth-mass planet in a Venus-like orbit), but with the development of the lucky imaging camera technology, microlensing should in principle be able to identify planets as small as Mars or even smaller. The theory of stellar microlensing was developed first by Einstein in 1936 (Science, vol.84, p.506-507), and later suggested to be able to reveal planets orbiting the lensing stars by Paczynski, Gould, and others. Several good descriptions about the theory of microlensing can be found on the web, eg. on the planet-legacy pages, the ARTEMiS pages, or just simply the Wiki- or Scholar-pedia pages. A short popular article in Danish, written by one of my former students Kennet Harpsøe, can be downloaded from the homepage of the journal Kvant.

In 1995 our team discovered, from the Danish telescope, what was then by far the most Earth-like exoplanet known. Although the planet is far from identical to the Earth (for one it is estimated to have a surface temperature of -200 Celcius degrees), it is Earth-like in the sense of having a mass (5.5 Earth-masses) and an orbit (2.6 AU) much more resembling the Earth than any other exoplanets that were known by then. The results were published in Nature, vol.439, p.437-440. together with Nature's comments to the discovery on page 400-401 in the same issue of the journal. ESO's press-release about the planet tells the story of the discovery, together with a short animation and an interview with me .

Microlensing allows to observe exoplanets at very large distances, including neareby other galaxies (although no planet outside our own Milky Way have yet been ideentified). All of the microlensing planets discovered so far have been identified due to the change in light of stars toward the centre of our own Galaxy where the density is high enough for the phenomenon to have a reasonable likelihood of happening. Typically a lensing star in this direction will be in the conficuration that will allow the discovery of orbiting planets once per almost a million years. Lensing observations is therefore a team-work of many telescopes that notify each other semi-automatically whenever a lensing anomaly is seen, to make sure that more telescopes observe the lensing planet when it is visible. By 2014 the total data-set of lensing curves contain approximately 50 events that seems to be due to planets, of which approximately half have such a quality that the parameters of the system has been well analyzed and published, including OB12406Lb, OB07368Lb, OB05071Lb, OB08310Lb, OB09387Lb, OB10073Lb, OB110251Lb, OB09266Lb and OB09319Lb. Since microlensing covers a parameter space not easily obtainable with any other method, the most important result from the analysis is how the statistical distribution of planetary masses and orbital distances are in this parameter interval. As opposed to other methods, quite stringent statistical conclusions can be drawn based on relatively few identified planets. Two central statistical studies that our group has been part of, conclude that there are more planets than stars in our Galaxy, that there are many more small-mass planets than high-mass planets, and that Jupiter-Saturn like planets in Jupiter-Saturn like orbits are relatively rare. This conclusion is in agreement with the statistical conclusions that can be derived from the radial velocity and transit surveys of exoplanets. In other words, Earth-like planets are common throughout the Milky Way, while Jupiter-Saturn like planets are rare. From the philosophical point of view of the Fermi paradox, one could ask whether this means that Jupiter-Saturn like planets in Jupiter-Saturn like orbits are central for the development of life on Earth-like planets further inside in thr habitable zone in the system, as probably was the case in our own solar system.

Microlensing search for exoplanets requires a dense stellar field (such that the chance of two stars passing one another close enough in the sky is not negligble) and the search is therefore concentrated in the direction toward the centre of the Milky Way. The main activity (microlensing search for exoplanets) of our MiNDSTEp consortium is therefore focused on the time where the centre of the Milky Way is visible in the sky. The observations are therefore best done from lattitude around -30 degrees on the Earth, where the Milky Way centre passes zenith in the sky, and the best period of the year is from May to September, where the Milky Way is visible during the longest part of the night. This is why the Danish telescope at La Silla (at lattitude -29) and the period we have access to it (April to October) is optimal for our research. However, even from La Silla the centre of the Galaxy is not visible throughout the night, in particular not during "the wings" of our period, and MiNDSTEp therefore have a number of other projects which we carry out during the time when the centre of the Galaxy is not visible. These include:
* extended observations of transiting exoplanets, including: WASP-80, WASP-15/16, GJ1214, WASP-7, WASP-18, WASP-5, and several others,
* development of the lucky imaging camera technology (which is essential for pushing the microlensing exoplanet research toward detection of planets with masses as small as the mass of the Earth, Mars, and even the Moon), including test observations of NGC6981 and detailed studies of the accuracy of photometry with EMCCDs,
* observations of objects in our own solar system, e.g. the main-belt comet La Sagra, and including also our recent discovery of a ring around the centaur object Chariklo, by use of our newly developed lucky imaging camera technology at the danish telescope (see also the press releases from ESO and from NBI about this discovery)
* studies of globular clusters (among other things as a testbase for the development of our lucky imaging camera), including M30, NGC6981, M9,
* cosmological gravitational lensing (e.g. the quasars HE0435 and UM673 ), and several other projects that we decide upon on an annual basis.

Stellar atmospheres and late stages of stellar evolution:

My early work on stellar atmospheres were on molecular opacities. When a molecule increase in size from 2 atoms to 3 or more atoms, the number of possible transitions increase substantially, because of the increase in modes and combinations between modes. While a typical diatomic molecule has a few thousand vibrational-rotational transitions of importance for the stellar spectrum and structure, the number of lines in just a tri-atomic molecule are counted in the millions. One of my first findings was that for polyatomic molecules, it is the veil of medium-strong lines that play the largest role for the atmospheric structure. In hindsight this is quite obvious; a figurative analogue could be the choice between sleeping covered in a thin blanket or a thick robe; the thinn veil of medium-weak lines block the radiation, creating a much larger backwarming effect on the atmosphere than the few strong lines would do, just as the blanket do to the heath of a sleeping body. When introducing the opacity of HCN to cool carbon star giants, the size of the model atmosphere expanded orders of magnitude, resulting in much better agreement with observed spectra, and for example solving the seeming paradox of atmospheric models showing carbon stars to be hydrogen poor, and it also quantified the huge effect logg (mass) had on the overall spectrum of giant stars. Over the coming years I improved my early order-of-magnitude estimates of the band-strengths (an early short conversation with Gerald Herzberg played an important role in getting these estimates more or less correct) to more detailed ab initio quantum chemical computations, in collaboration with Jan Almlöf, Per Siegbahn and Mats Larsson during my stay in Sweden. These and later studies include my work on opacities of HCN , C3 , water , methane, CIA (collision induced absorption processes), diamond dust, CH, CN, TiO, SiO, and other molecules which will (hopefully) all be available as line lists on this web page very soon again. Reviews of the molecular data were summarised at several occasions (including: 1, 2, 3). Unfortunately most of my line lists disappeared from my public ftp site a few years ago after a very unfortunate series of almost simultaneous disk and computer crashes together with a misunderstood agreement with the university about backups. I have also promised myself to re-establish my line list data base, hopefully very soon, making it again available from this web address.

In collaboration with Åke Nordlund, Bengt Gustafson, Kjell Erikson, Hollis Johnson, Aleksandra Borysow, Josef Hron, Susanne Höfner, and others, we investigated the effect on the stellar structure, with implication for the late stages of small- and medium-mass stars. These studies included reviews of the stellar atmosphere modelling, analysis of the effects of spherical geometry, hydrodynamics, frequency dependence, the sampling -methods and -optimisation, tests of the models against spaceborne observations of carbon- and M-type giants, as well as ground-based wide spectral range (e.g. 5000 AA to 2.5 mu_m) comparisons of synthetic observed spectra, and analysis of white dwarf atmospheres, and evolution.

I'm still working in this field occasionally. In 2008 we published an updated version of the MARCS code. It is the intention that this will be followed by a series of more detailed papers on various types of stellar atmospheres. In long term it is the hope to expand the MARCS code to be able also to analyse sub-stellar objects with cloud formation, and illuminated stars and hot (or cool) exoplanets.

The formation and evolution of the solar system.

A cornerstone in understanding how our solar system formed, is to understand what should have gone different in order that our solar system would have become as any of the many other exoplanetary system that has been identified in recent years. In 2009 I participated in creating a centre of excellence, StarPlan, which theme could be expressed as: "is our solar system unique -- and if so, is that then the reason that we are here?". The centre is based on 4 multidisiplinary entrances to the question: cosmochemical studies of the interstellar environment where our solar system formed (through measurements of early meteoritic material), numerical models of the disk formation phase, sub-mm observations of solar systems under formation, and the study of exoplanetary systems.

Although my main contribution to this study is in the field of exoplanets, I have also been working on the meteoritic aspects, with studies of interstellar grains in primitive meteorites, including a theory for the formation of extrasolar diamond and SiC grains, the absorption coefficient of the extracted extrasolar diamonds and silicon_carbide grains. By including these data in atmospheric modelling it is in principle possible to trace the stellar origin of the material that became the solar system.

I have also contributed to the solar system research with preditions and speculations about what will happen to the Sun and the Earth during the final phases of the evolution of the Sun.

A particular puzzling and interesting problem, in my oppinion, is how water originated on the Earth. It was too hot in the solar nebula for water to condense out of the nebula at the distance where the Earth assembled material for its formation. Therefore water must have come to Earth later. This problem is further supported by the fact that asteroids in the inner main belt are de-hydrated, while only asteroids (and meteorites) from the outer part of the belt contain water, indicating that there is a relatively sharp boundary at around 2.7 AU inside which water was not part of the originally assembled planets. Some years ago I had the great pleasure of being invited by Peter Apple to join his team of geologists on an expedition to the Isua region in Greenland . Isua is the only part of the Earth's sedimentary crust which is old enough to be contemporary with the late heavy bombardment -- the latest large scale assembly of cosmic material on Earth. During the Isua formation period 3.8 billion years ago, 2000 tons of cosmic material fel on each square meter of the Earth's surface. The samples we brought home from the expedition indicate that the bombarding objects were mainly comets, and if this conclusion is correct, they will have brought with them the same amount of water that is today present in the Earth's oceans. During the latest couple of years I have been working together with Hans Rickman to try to understand what consequences different scenarios of the late heavy bombardment would have for not only Earth and Moon, but for the other terrestrial planets too, in particular Mars. We will hopefully be able to publish these ideas soon in a regular scientific paper, but untill then a summary of a presentation I gave about these ideas at an international conference in Gdynia in 2014 is avbailable here.

The SCAN molecular data base:

This page is under re-construction. Due to a very unfortunate crash of the disks on two independent computers together with a misunderstanding about the university's back up agreement, the data dissappeared. Fortunately I have recovered most of the line lists now from various collaborators that had downloaded a copy of the lists. The papers behind the computations are described above, and the line lists will soon be available here again. The instructions that describe the lists are available here for CH, C2, TiO, H2O, and I try to add the description of the other molecules mentioned above together with the lists as soon as I can.



During recent years I have been teaching 3 graduate courses:
astrobiology, (in block 1 group A each second year; 2013, 2015, ...)
planetary physics (in block 3 group A each year)
spectroscopy (in block 2 group B each second year; 2014, 2016, ...)
and a bachelor course:
the solar system (in block 3 each year).

Thesis supervision:

I am presently supervisor for 3 PhD students:
Andrius Popovas on energy transport in protoplanetary disks (co-supervising with Åke Nordlund, NBI)
Diana Juncher on cloud formation in cool stars, brown dwarfs and exoplanetary atmospheres
Jesper Skorfelt on lucky imaging camera technology for exoplanet detection

Previous PhD students:
Kennet Harpsøe on the lucky imaging technique and microlensing
Christian Vinter on the search for exoplanets by use of the microlensing technique,
Juliana daSilva (co-advised with Luiz Vaz, Bel Horizonte, Brazil) on external illumination in stellar and exoplanetary atmospherers,
Stefan Wolf (co-advised with Poul Hjort, DTU) on Near-Earth asteroids; planning detection with the Gaia satellite.
Anja Andersen on dustformation in stars
Raul Jimenez on stellar evolution and the age of the Universe

Previous Master students:
Andrius Popovas on partition functions and opacity sampling methods,
Mads Sørensen, on the supernova rate in the solar neighbourhood (co-adviced with Henrik Svendsmark, DTU Space),
Sanne Hardis, The transiting exoplanet GJ1214b,
Joris Vos, on eclipsing binary stars (co-supervising with Jens Viggo Clausen, NBI),
Mikkel Mathiasen, Photometry on microlensing events
Kristian Woller on stellar abundance analysis,
Maha Jasim on the formation of the solar system,
Sitte Larsson on the formation of the solar system and dust formation in the collapsing disk,
Tobias Hinse on orbital computation (resonances, migration, etc) of exoplanets.
Claus Nielsen on comets and the Earth's atmosphere,
Christian Vinter on the search for exoplanets by use of the microlensing technique,
Dorte E. Rasmussen on cool white dwarfs,
Steen E. Jørgensen on laser communication with satellite (co-supervising with Flemming Hansen, DSRI)
Jens Falkesgaard on chemical equilibrium computations,
Søren Rasmussen on stellar atmospheres,
Peter Pedersen on the initial stellar mass function,
Christiane Helling on molecular opacities (co-supervising with Erwin Sedlmayr in Berlin),
Anja Andersen on pre-solar dust grains in meteorites,


A popular description of some of our science results include:
A description of our discovery of a ring around the small Centaur asteroide Chariklo, from NBI's, and from ESO's home pages.
The discovery of the Earth-like exoplanet OB05390, from ESO's text press release and in the format of a video animation and interview with me.
A sumary of our measurements of iridium abundances in samples collected at the 3.8 billion years old Isua region in Greenland, indicating that the Earth and the Moon was bombarded with 2000 tons of cometary material per square meter while Isua formed (in English and in Danish ).

General popular talks on the web include my short 2013 presentation in TV2 (Danskernes Akademi) about the chances of finding life on other planets, presented in an English version, and a Danish version, my 1/2 hour presentation for teachers in 2010 at NBI about the origin of water on the Earth, and a general and longer presentation that I am particularly happy with from the "Science and Coctails" arangement at Christiania in 2012.

Since 1995 I have had a fruitful collaboration with Bent Raymond Jørgensen on several series of public lectures, starting with our series of 25 TV broadcastings about natural science, history of science, philosophy, and its relation to religion. The series was first filmed at NBI and broadcated in DR1 in 1995, and later we made a technically better version in the television studios which was broadcasted in 1996/97 (a total of 25 broadcastings).
The series of lectures was issued in the form of a book with the titel "Videnskaben_eller_Gud?" ("Science or God?") in 1996, with a revised second edition in 1998 and revised and enlarged third edition in 2005. Bent has an overview of this and two later books at his homepage.

I regularly publish popular articles in various journals, for example:
U.G.Jørgensen, Aktuel Naturvidenskab (nr 12, 2012, p.16-20) about habitable exoplanets ("10 milliarder planeter som Jorden -- hvor er beboerne?).
U.G.Jørgensen, Berlingske. 22nd December 2012, about doomsday, hvornår går Jorden så under?.
U.G.Jørgensen, Weekend Avisen, 13.January 2012, about our calculated statistics of habitable exoplanets, hvor bliver de andre af?.
U.G.Jørgensen, Universitetets Almanak 2006 about exoplanets (2006).
U.G.Jørgensen, Naturens Verden about Tycho Brahe (NV, vol.84, nr.10, p26-31)
U.G.Jørgensen, Naturens Verden about the origin or the Earth's oceans (NV, vol.85, nr.2, p2-13),
U.G.Jørgensen, "Where does the elements come from?", Geologisk Museums udstillingskatalog, 2006.
Haack, H., Jørgensen, U. G., Andersen, A., Bizzarro, M., Buchwald, V. F. (2006). Solsystemet - fra altings oprindelse til livets opståen. Geoviden, (3), 2-19.
Haack, H, Jørgensen, UG, Andersen, A, Bizzarro, M, Buchwald, VF 2006, 'Solsystemets opståen.' Geologisk Nyt, no. 5, pp. 10-18.
U.G.Jørgensen, Kvant about the Deep Impact collision with Comet Tempel (vol.16 nr.3, 2005, p.11,12,36),
U.G.Jørgensen, Aktuel Astronomi about exoplanets (AA, 2004 nr 2, p.16-19) "Exoplanetjagten,
U.G.Jørgensen, Kvant about the formation of solar systems (vol.15 nr.3, 2004, p.8-14), "Er Solsystemet almindeligt blandt solsystemer?"

Science administrative involvement:

I am for the moment head of the astronomy area ("områdeleder" in Danish) of the Niels Bohr Institute, and I'm head of our group for Astrophysics and Planetary Science (in Danish: Astrofysik og Planetforskning ).

I'm in charge of the operation of the Danish 1.54m telescope at ESO's La Silla observatory in Chile, I lead the exoplanet part of the international SONG network of small robotic telescopes, and I organize the MiNDSTEp microlensing search for exoplanets, and I participated in the formation of the Nordic Astrobiology Network.

I participated in the creation of the Centre of Excelence, StarPlan (Centre for Star and Planet Formation), with the aim of better understanding the role of our own solar system relative to other planetary systems in our Galaxy.

I was a member of ESO's OPC for a number of years during the late 1990'ies, and later member of ESO's user's committee. Since 2011 I have been the Danish scientific member of the ESO Council. Two of the most interesting issues we are discussing in Council during these years is ESO's conscruction of the world's largest optical telescope, the almost 40 meter mirror European ELT telescope, and the transformation of ESO from a European to a global organisation for astronomy.

Latest updated September 2014 by uffegj@nbi.dk.