October 2017 Letter from the Director

The big news this month was the release of the many papers reporting detection of the merger of two neutron stars first detected as a gravity wave by LIGO. We congratulate our colleagues at Carnegie Observatories who were the first to detect the merger at optical wavelengths. The team used the Swope telescope, the oldest telescope at Carnegie's Las Campanas Observatory, with additional observations continuing with the much larger Magellan telescopes. DTM's role in this discovery was mostly our excitement in reading the publications that stimulated an "emergency" paper discussion meeting within our astronomy and cosmochemistry groups. We are very proud, however, that our former communications and outreach coordinator, Robin Dienel, was chosen to create the widely circulated artist's impression of the merger.
Artist's concept of the explosive collision of two neutron stars. Illustration by Robin Dienel courtesy of the Carnegie Institution for Science.

For the more "down to Earth" members of DTM, the observations of the merger are providing clues to the long-standing problem of the process that created many of the isotopes and elements making up our Solar System. One of the two main paths for creating elements heavier than iron is known as the s-process. It involves slow additions of neutrons that likely occur due to nuclear reactions deep in a type of star known as an Asymptotic Giant Branch (AGB) star. The second path, known as the r-process, involves much more rapid neutron addition that drives isotopes far to the neutron-rich side from the region of nuclear stability. These isotopes undergo repeated radioactive decay that turns the excess neutrons into protons, leading to new isotopes with stable nuclear combinations of neutrons and protons.

The r-process was originally thought to occur in exploding massive stars, or supernovae. Supernovae, however, occur relatively often in the galaxy, which should result in higher abundances of r-process isotopes than are observed in the elements that make up our Solar System. The relative dearth of r-process isotopes in our region of the galaxy led to the suspicion that the r-process occurs instead in more unusual and more energetic events, such as the merger of neutron stars. The spectroscopic observations of the recent neutron star merger indeed are consistent with the event producing substantial quantities of r-process isotopes. If you were wondering why the newspaper articles about the merger focused on platinum and gold, it is because both elements are dominantly produced by the r-process. Going very far back into the production process, you thus have neutron-star mergers to thank for your jewelry!
October marks the beginning of our annual Neighborhood Lecture series, now starting its eleventh season. The first lecture this year was a presentation by DTM's John Chambers on planet formation. After the presentation, the neighbors surrounded John and peppered him with questions for another half hour. The enthusiasm of the attendees at the neighborhood lectures is most impressive, as is the quality of their questions.

John talked about “The Mystery of Planet Formation” to a packed Greenewalt Auditorium on Thursday, October 26, 2017.

In thinking about the reasons these events are so popular, beyond just the interest in the cutting edge science going on at the BBR campus, I wonder if coverage of science in the conventional media has been so oversimplified that it no longer conveys the excitement of the work to those with an interest in science and experience in technical fields. Intellectual stimulation drives most of the research done at DTM, so we are extremely happy to be able to communicate and transfer this enthusiasm in understanding our natural world to the community through the neighborhood lectures.

Observances & Outreach

October marks the month when the newly arrived class of BBR postdoctoral fellows reaches a sufficiently critical mass for the campus to celebrate their arrival. Festivities this year includeda campus ping-pong tournament, where DTMers won both the men’s (Jesse Reimink) and the women’s (Jessica Donaldson) singles competitions.  DTM did, however, lose the tug-of-war at the Annual Fall Picnic to GL, although our ability to hold off the vastly larger GL crew greatly exceeded previous years, by at least several seconds.  Postdoc appreciation week in September was crowned by a group-painting lesson led by GL intern Lavontria Miché Aaron, but another example of the artistic skill of our postdocs was the selection of an image of the ice ring with implications for planet formation around the nearby star Fomalhaut as the NASA Astronomy Picture of the Day on October 3.  Our newly arrived NSF Postdoctoral Fellow, Meredith Macgregor created this image using the ALMA radiotelescope.


DTM Postdocs had fun taking their 2017 group picture before the BBR Annual Fall Picnic.
The other traditional event held every fall is the Mud Cup soccer tournament between DTM and GL.  Thanks to the direction of team captain Miki Nakajima, I am pleased to report that after a well-fought battle by our GL colleagues, the Mud Cup has returned to DTM on the basis of our 1-0 victory. 

The DTM Dynamos claimed the 2017 Mud Cup after a 1-0 victory over the GL Pistons.

Not everything between DTM and GL is a competition.  For example, I am pleased to report that DTM Staff Scientist, Peter van Keken, was recently awarded one of the Carnegie Venture Grants that encourage cross-department research.  In this case, Peter will be working with GL’s Alex Goncharov to measure the thermal conductivity of materials likely to be present in the interior of Mars in order to enable models of the thermal evolution of the Martian interior.  The goal of the work is to better understand why Mars cooled so fast and so early in Solar System history.

In preparing for next week’s Carnegie Board meeting, BBR’s librarian Shaun Hardy helped me compare the growth rate of DTM’s contribution to science by tallying the number of publications in two five year windows, 1985-1989 and 2012-2016.  The number of publications involving DTM scientists as authors or coauthors increased by a factor of 3.6 in the most recent window.  A curious statistic in these data is that the number of papers involving only DTM authors decreased by almost a factor of 3.  The reason is that DTM science, and science in general, is becoming more collaborative, and more international.  In the 1985-1989 time window, 114 of DTM’s papers were coauthored with colleagues from 80 different institutions.  In the more recent time window, 627 of DTM’s papers were coauthored with colleagues from 649 different institutions spanning all continents but Antarctica, although DTM does do research  there. For example, Staff Scientists Conel Alexander and Larry Nittler’s collection of extraterrestrial dust at the South Pole.

Likely the other factor playing a role here is that of the 106 postdocs that have worked at DTM over the last 17 years, 76 of them are now in jobs scattered between 19 different States, 17 are in Europe, 9 in Austral-Asia, and one each in South Africa and Chile.  DTM’s influence is thus wide ranging and increasingly international, which is also reflected in the fact that more than half of DTM’s current visiting investigators are from countries other than the United States.  Earth and planetary science knows no borders, and neither do DTM’s collaborations.


Richard Carlson, Director, DTM
Carnegie Institution for Science
October 2017 Newsletter

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