On December 25, 2016, the great astronomer Vera Rubin passed away, surrounded by her family. Vera helped discover the still-mysterious presence of dark matter in the universe in the 1970s, when the largest telescope in the world was about 5m in diameter (now we are working to build telescopes five to six times that size). Her creativity and persistence and ingenuity advanced astronomy into a new age of exploration and trying to understand the history of everything. At the same time she demonstrated the amazing potential and the necessity of women participating in science. Vera was a vocal proponent of equity for women in science, for women's rights in larger society, and a mentor and inspiration to many, many women scientists at all career stages. You can read more about her life and her work here and here (both in her own words), here, here, here, and here.
Frustratingly and sadly, Vera has not and will not be awarded a Nobel Prize for her ground-breaking and trail-blazing work. But we should remember her for the awesome scientist and person she was, Nobel or not, and can honor her by continuing to share memories and stories of her life and work. We started an open document for those who knew Vera, who drew courage and strength from her resilience, who were deeply touched by her compassion and humanity can share their memories of her. This is also a window into the day-to-day difference she made, for those who did not have the privilege of knowing her.
Thank you, Vera.
Vera Rubin in 2010. (Linda Davidson/The Washington Post)
Every since I started observing at Las Campanas, I've talked to my mom about how amazing it is -- the views, the facilities, the people, the food. She loves hearing about my adventures and seeing pictures, and closely follows Yuri Beletsky (whose pictures surpass mine by far). She also has a deep appreciation for nature and how awesome the universe is. Thus it was my great pleasure to treat her to a trip to Las Campanas! I'm here for a two-night MIKE run to observe stars that host cool Jupiter exoplanets. I'm working with Jonathan Fortney and Daniel Thorngren to understand how the composition of these stars may be related to the heavy element mass locked up in their gas giant planets. You can read more about the project in Daniel's paper. What this post is mostly about is Las Campanas from my mom's perspective. Here is our mini interview:
1. What brings you to Las Campanas?
First and foremost, to spend time with my daughter, Johanna, watching her work. Secondly, to see the
night sky. I have seen pictures, but I wanted to see the night sky and stars with my own eyes. And the
empanadas. Cannot forget the empanadas!
2. How was your travel to the telescopes?
The travel was long! I traveled from Harrisburg, PA. Johanna and I had adventures flying from Miami to
La Serena, sleeping in little pods on the plane. But the drive up to the telescopes was amazing- the road
kept getting steeper and steeper until there was no more road. We reached the top of the earth! I kept
thinking about all of the amazing people who build these telescopes and how challenging their journey
must have been.
Johanna and Diane/mom in sleeping pods on the plane to Santiago.
3. What were you most looking forward to? Has that happened?
I was most looking forward to seeing the Milky Way. We saw it last night and it was amazing. Dizzying,
in fact! A lifetime event for me. And watching the sunset was unlike anything I have ever seen. Ribbons
of reds and oranges with no cloud interference. And SO MANY STARS! I will never forget that night sky.
Lastly, hearing about Johanna's adventures so far and her ideas about her future. She inspires me!
4. Has anything surprised you so far?
The temperature has surprised me -- I expected it to be cooler during the day, but it is actually quite
pleasant. Another thing that surprised me is how astronomers "share" data and "time" with each other.
Johanna is actually using some of her time tonight to "pay back" a colleague who got some observations for her earlier in the year. It is a concept that is not common across other sciences -- folks can be territorial about their data.
5. What have you done at the Observatory so far? We took a nice long walk this morning and I got to see all of the telescopes. I heard a bit about the
history behind each one, which I enjoyed. I also saw some new flora and fauna, which is always of
interest to me. I also have enjoyed the meals at Las Campanas and was happy to be here for Empanada
Sunday! I am looking forward to seeing Johanna in action tonight as she observes. But the night sky and time with my daughter are the highlights so far.
Clay Telescope, with Johanna for scale
6. How would you describe Las Campanas Observatory to other people? What does astronomical
observing look like (to someone who does not do it for a living)?
It is not what I thought it would be like. There is a lot of sitting at computers doing compter-y stuff. But
last night, I was witness to some exciting science happen. One of Johanna's colleagues found some
important stuff for his research, and while I was not clear on what it was, there was an excitement in
the room that was palpable. I also am now aware that the observing runs are just PART of the work.
For example, I am spending the afternoon with my daughter as she "calibrates" the instrument she will
be using tonight. Then she does the observations, then the analysis, then the writing of the paper. I am
learning that astronomical observing is just part of a larger process.
7. Any tips for first-timers?
Ask lots of questions, drink lots of water, rest after walking uphill, take lots of pictures. And look up at
the night sky every chance you get. The excitement starts after sun down!
Viscacha at sunset!
Sunset on our first night. Can you spot Venus?
8. Anything else you'd like to share?
My gratitude for the staff and scientists who allowed me to come and be a part of this awesome
experience.
This trip had a lot of first for me: first time going observing at a major observatory, first time in the Southern Hemisphere, first time taking infrared spectra and images, and last but not least first time doing it on my own after only two days of training. I was so excited when I first got to Chile. There was so much to see and especially when I got to Las Campanas all I wanted to do was look around. When I arrived I was under the impression that we were going to start observing that night, but to my surprise we didn’t start until the next day, which was great for me since I was exhausted after the long flight.
On day one of observing, after lunch I went up to Baade to meet my advisor, Jackie Faherty, to start calibrations for FIRE and Fourstar. Learning about calibrations was simple enough, especially since all of the information could be found in previous nights logs. After calibrations I had some free time to explore before dinner.
On the way up I saw this guy. We had a stare down, until he walked away.
After taking calibrations I found some of these creatures.
The first I observed using FIRE on the Baade telescope. When I saw the telescope for the first time my first thought was “This is SOOO big. I feel so tiny!”. You can see me to scale with the mirror, no joke this telescope is enormous and I can’t even fathom how crazy it will be to look at the GMT.
The night wasn’t too intense, but it was a lot to take in knowing that in two days I would be on my own. At first I made a few mistakes, mostly incorrect filenames, but as the night went on I started to feel more comfortable with the instrument. Also, having a ton of notes on the processes helped to ease my nervousness about the upcoming night alone. The conditions were’t the best but we managed to get a fair amount of targets done.
On the second night I used both FIRE and FourStar. FourStar was much simpler to use, which made me less worried about the next night, since I would be using both instruments. The conditions were great, so I got lots more experience using FIRE and I managed to make very few errors over the night. I was quite proud about that! At the end of the night Jackie and I discussed the plan for the next night. At that point I felt fairly comfortable to be left on my own with my game plan in hand, I headed off for bed.
This brings us up to tonight where I am alone. Eek! Calibrations made me a bit nervous, since the first question I got from the telescope operator was about what to do with the mirror cover. He hadn’t asked us previously so I felt unsure about what to do, but I once I thought about it the answer was clear and my fears of messing up calibrations went away. At dinner I met the person who was going to be on Baade after me. He was very curious to see how FourStar works, so he decided to join me for part of the night. The conditions needed up being perfect and the night was smooth sailing! Now I just need to get all of this data transferred and then off for a nap!
Hello Las Campanas Belles! While I spend most of my time in Chile at LCO, this week I was in Chile observing on a telescope a couple hundred kilometers to the south: the Gemini South telescope at Cerro Pachon. I blogged about it at Cosmic Diary/ Gemini Planet Imager, but I wanted to post a little about it here!
I had never been on an all-women observing run before, and neither had any of the 5 of us! Myself, MagAO users Kate Follette, Kim Ward-Duong, and Jenny Patience, and student Sarah Blunt were at Gemini to look for planets using the Gemini Planet Imager (GPI). It's winter in Chile and we had some cloudy weather as well as a bit of snow, but we squeezed in observations whenever we could. Check out the link above to read more about it!
And here is a picture of the women GPIES observers:
Here is the Gemini dome with some beautiful but not-good-for-observing clouds:
And they have some of the same animals at Gemini, like this cute little zorro near the dorms!
The purpose of the summit was to bring together fifty or so
astronomy outreach professionals, teachers and administrators to work on
revising the draft of the Roadmap to the
Stars (not available online yet - still a draft). This document, written at the first Summit in 2015, outlines the
current state and the future of astronomy outreach in Chile. The summit was
also a great opportunity to network, to share ideas and to make connections
with our counterparts.
I was there representing the Giant Magellan Telescope Organization, which meant I had the good fortune to spend
the week with my colleague, Dr. Miguel Roth, former Director of Las Campanas
Observatory (LCO), and current Chile Representative for the GMT.
The first day of the summit was a fieldtrip to LCO. On the
bus I got to know Pablo Álvarez, who is working on a project called Astroturismo Chile,
which is assessing the quality and competitiveness of astrotourism in Chile.
As we reached the turn-off from the Pan American Highway, I
immediately recognized the landscape in the distance. Looking from left to
right we could see the du Pont, the Magellans, and the GMT site. The driver
stopped the bus, and we all got off to check it out. Mark Philips, current LCO
Director, explained what we were seeing.
Mark Phillips (L) and Pablo Álvarez (R) look towards Las Campanas.
Then we began the somewhat tedious, bumpy and dusty journey to the summit. As we got closer, the two instrument towers on the GMT summit became more visible, and soon we reached the turn off to the site. We couldn’t pay it a visit due to construction work, but I was excited to be there again. (Last time I was there, it was the GMT Groundbreaking Ceremony in November 2015.)
The instrument towers visible on the GMT site.
We continued to the far end of LCO to the du Pont Telescope. Commissioned in the mid-1970s, it was used for wide-field photography on photographic plates. It is now being used for a new project, APOGEE, a fiber-fed spectrograph designed to do a southern sky survey of the Milky Way.
Mark Phillips tells the group about the du Pont Telescope.
From our vantage point at du Pont we could see all of LCO’s telescopes. In the middle distance was the Swope, named after Henrietta Swope, a famous astronomer who was also a philanthropist and gave $250,000 to Carnegie to build the telescope.
We could also see three site testing telescopes that are used to measure the site’s seeing. Also in the middle was the Ogle, a 1.3m telescope operated by the University of Warsaw for gravitational lensing observations.
Las Campanas Observatory.
Magellans to the left, Swope and Ogle in the middle, and the GMT site far right.
All of this information was coming at us via a bilingual comedy double act between Mark and Miguel. Mark was doing the English, and Miguel was doing the Spanish, except when they forgot which was their native language and switched. The explanations became a competition as each of them relayed ever more outlandish stories.
Mark Phillips and Miguel Roth keep the crowd entertained.
Soon it was lunchtime, and we sat on long benches in the dining room getting to know our colleagues. I chatted with Valentina Rodríguez and Laura Ventura from ESO, feeling quite inadequate at my lack of Spanish.
After lunch we were taken to see the Magellans, and we headed up the stairs into the control room of the Baade telescope. Mark and Miguel continued their comedy routine before we were taken inside the dome to stand face to face with the 6.5 meter mirror.
Miguel Roth tells another elaborate story inside the Baade control room.
The explanations and descriptions of the telescope and its mirror came thick and fast from Miguel and Mark but everyone seemed more excited about getting their photo taken with the mirror. We were also lucky enough to have time to visit the coating chamber in between the two telescopes. Each year one of the mirrors is stripped and realuminized in this room (video here).
Miguel Roth and me with the Baade mirror.
Suitably telescoped-out we rejoined our bus and headed a little way down the hill for a group shot with the GMT site in the background. Then we hit the road for the two hour drive back to La Serena.
Group photo - GMT site in the background.
This outing was the first of many highlights of the Summit. I won’t forget the experience of revising the Roadmap document, huddled around a translator who was doing an amazing job of keeping us non-Spanish-speakers in the loop. I was appreciative of the opportunity to meet and get to know the many enthusiastic astronomy outreach professionals who attended (especially Suzanne Jacoby from LSST and Sandi Preston from McDonald Observatory). What I learned was that there are more great ideas for engaging the public with astronomythan I could have imagined, and that an enormous amount of work is being done in Chile already.The country hosts a large fraction of the world's astronomical light gathering capability, and the hope is that one day the world will come to knowChile forits astronomy.
I’m very grateful to the Summit organizers for such a productive and well-run event, and for inviting me to attend.
===
Read more about the Summit on its Facebook page! Find out more about
what’s going on at GMTO from our latest newsletter published in March.
This is post is mostly by Liang, with a little bit by Johanna at the end.
Johanna said to include a picture of me "doing science". For most astronomers,
most of the time, this is what "doing science" looks like!
My name is Liang Yu and I'm a second-year graduate student at MIT. I started working on the K2 mission about five months ago. Since it began in 2013, the mission has yielded about 300 transiting exoplanet candidates. I'd like to share with you some of these exciting results and a behind-the-scenes sneak peek of how we extract signals from planet candidates from large quantities of K2 data. Thank you Johanna for starting this wonderful blog!
K2 is the "successor" of NASA's highly successful Kepler mission, which has discovered thousands of transiting exoplanet candidates. By staring at stars in one patch of sky and watching for them to change brightness, Kepler could detect when a planet passed in front of a star and blocked out a tiny fraction of its light. (If you want to try detecting Kepler planets yourself, try out this simulation or this Citizen Science project!) By May 2013, two of the spacecraft's four reaction wheels had failed, leaving Kepler unable to point precisely at its original field (in the Cygnus constellation). Luckily, the spacecraft is still able to balance itself against solar radiation pressure and continue taking data, and the mission has since been renamed "K2". K2 is different in that it does not point at one patch of sky continuously, but observes different fields of stars for 80 days each. This means it has a shorter baseline for catching stellar brightness changes due to planets (so, it cannot detect longer period planets), but also that we now get to search for transiting planets all across the sky. Another different and cool thing about K2 is that it is almost totally community-driven -- scientists propose for what targets they want observed in each field, and the data are public immediately, so anyone with a computer can analyze them.
K2 delivers images of each field from which we can produce a time series of each star's brightness level (called a light curve). But astronomers quickly discovered that the reduced pointing precision of K2 introduced significant levels of systematic noise into the light curves. Without any special processing, most transit signals would be hidden by the noise.
This is what a raw image of a star looks like, straight from K2. The star can sometimes look elongated due to the spacecraft's motion.
There is a fix for this problem, however. Systematic fluctuations in the light curves are strongly correlated with the camera's motion. The spacecraft slowly drifts and is straightened by thruster fires every 6 hours, leading to sudden jumps in the light curves. After several rounds of cleaning that corrects for systematic noise as a function of the spacecraft's motion, and removing the low-frequency variability caused by stellar activity, we get much higher quality data that can reveal transits shallower (smaller) than the level of systematic noise. That translates to smaller planets!
Top: The uncorrected light curve from K2. Bottom: The same light curve after removing noise correlated to
the spacecraft motion and stellar activity. Now we can clearly see the little dips that may correspond
to a planet passing in front of the star at regular intervals.
After running this procedure on tens of thousands of target stars in each K2 field (which usually takes at least a few hours), we then run a procedure called Box-Least-Squares on all the cleaned light curves to find the ones with periodic dips that look like exoplanets eclipsing their host stars. Folding each light curve so that the dips overlap, we get these (sometimes) beautiful plots of exoplanet transits. The shapes and sizes of these dips can reveal a wealth of information about the planets causing the transits.
A cleaned and folded light curve, fitted with a theoretical model of a transit (red curve).
First of all, the depth of the transit tells us the size of the planet candidate relative to its host star. The deeper the transit, the larger the planet compared to the star. Combining this information with the absolute size of the star, which we can estimate from images taken at different wavelengths, we can derive the absolute radius of the planet. Previous work has uncovered an empirical relation between planetary radius and mass, which works well at least for small planets. Thus we can plug our estimate of the planets' radius into this relation to get a first guess for their masses. However, to get a more reliable estimate, we must turn to ground-based follow-up observations.
That's where the Planet Finder Spectrograph (PFS) at Magellan II comes in! I've written about PFS before, but not much about the science it actually accomplishes. PFS detects planets via the "Doppler wobble" or radial velocity technique -- we observe stars and spread out their light through a grating, like sunlight through a prism, into the different components or wavelengths of the light. As light escapes a star's interior through it's atmosphere, the atmosphere absorbs a bit of the light in specific patterns, depending on what the atmosphere is made of. This is observable in lines "missing" from the star's spectrum. In addition to the composition of the atmosphere, the motion of the star (moving towards or away from us) also controls the positioning of the absorption lines.
In a simplistic picture, we can think of stars as stable, non-moving objects. In reality, they have their own orbits and motions around the Galaxy, are sometimes interacting with each other, and our Sun is moving relative to them. But if we just observe one star and compare it to itself at some reference point, the motion should be pretty small. And yet, we see evidence of stars moving more than expected in the shifting positions of the absorption lines in their spectra. It appears that they are moving towards and away from us in a small but measurable and very periodic way. What could be causing this motion?
PLANETS!
This is a video from ESO (L. Calçada), showing how a star's motion towards and away from us is 1) reflected in the lines of its spectrum and 2) caused by a planet orbiting the star and causing the motion. We are a little competitive with ESO (their precision radial velocity spectrograph is called HARPS), but they make a mean movie so I couldn't help myself.
While in most cases stars are much(x3) more massive than planets, they still obey the laws of gravity, so that the star effectively feels a tiny gravitational pull from the planet and the planet effectively feels a much larger gravitational pull from the star. From afar, it seems like the planet is just orbiting the star, but in reality (as is shown in an exaggerated way in the video), the star and planet are both orbiting a common center of mass. With PFS, we distinguish tiny shifts in the star's absorption lines, caused by tiny tugs from planets, by comparing how these lines move relative to an actually-stable reference spectrum, typically of iodine. We superimpose the iodine spectrum on top of the star's lines, and thus have "zero point" around which we can measure how the star's lines change.
Carnegie DTM's Paul Butler helped pioneer this iodine-cell radial velocity (RV) technique to detect some of the first exoplanets ever. In fact, the 20th anniversary of the first exoplanet detected this way around a solar-like star, 51 Peg b, was this year. For a long time, RV was the most productive way to detect exoplanets; it really wasn't until Kepler was launched that the RV planet detection rate was surpassed.
The beautiful thing is, both RV and transit techniques are really needed to learn about planets, since the first only measures a mass and the second only measures a radius. If we want to understand what planets are made of -- and we very much do! -- we need both techniques. This has led to a growing partnership between Kepler and K2 planet-finders and ground-based RV observers, one of which is now K2+PFS. We also partner with the HAT-South transiting planet survey, and have already helped confirm and better characterize ~10 transiting exoplanets (that is in addition to the ~10 RV-only planets PFS has detected or help confirm). One of my favorite transiting planet follow-ups so far is WASP-97, an unusual system because it hosts a small, probably-rocky planet inside the orbit of a giant, hot Jupiter planet; the smaller planet goes around the star every ~19 hours. PFS measured or helped confirm the masses and orbits of all of the planets in this system.
As an astronomer, I had to learn to "let it go" when it comes to the weather. It is completely out of my control, and sometimes I am lucky, and sometimes I am not. I had a discussion at dinner a few nights ago with the observer on the other telescope (Baade), Dan Milisavljevic, about the risks and rewards of ground-based observing. He commented on how curious it must be to non-observers that we spend so much time and money and energy on an activity with such inherent, known risk. Las Campanas is one of the best sites to observe in the world, but there are still nights lost to weather -- last August I lost two nights, and friends of mine have lost more. But my comment was, that's part of what makes observing exciting, especially classical observing (where the observer themselves goes to the telescope, versus queue observing, when someone else does your observations for you). There is an unpredictable aspect to it, and you have to be ready to think on your feet to adapt to whatever the weather brings. When the weather is bad, it is really disappointing, and certainly projects and science suffers. But when the weather is good, it is like magic.
As I post this, I'm in the middle of a 13-night PFS (Planet Finding Spectrograph) run with StevenShectman. Observing at Magellan with Steve is a special treat, because he designed and built the telescopes (with the help of many others). Steve knows all the ins and outs of the structure, the site, the mirrors, the telescope computers and software, the staff, and most of the instruments. He was and is an invaluable resource to Las Campanas, and really to our community overall. It is a privilege to know and work with him. It's also really fun.
So, it is like a sundae with a cherry on top when I get to observe with Steve and we have good weather. And this run, so far, we've had the longest stretch of good weather I have ever experienced at LCO. Minus a few clouds last night that moved in and out quickly, we have had clear, calm skies with remarkably good seeing (very little turbulence in the atmosphere, so the starlight is better concentrated into our narrow slit). I've written about good seeing before, but that was only over two nights. We're on our sixth night of near-pristine or pristine seeing; for calibration, 0.5'' seeing is considering very good, and rare at most other observatories. A few nights ago (New Year's Eve, actually), I took this screen shot at the end of the night...and added some embellishment:
This shows the seeing as a function of time, increasing to the right. The telescope we're using is in red. At the end of the night, we had several bouts of < 0.5'' seeing. Epic! (Also note that we, in red, won the seeing battle with Baade that night. I think so far we are winning 4 nights to 1; we'll see how tonight shakes out.)
But tonight, tonight is really magic. Take a look at the same plot from tonight so far:
See how much we are below the 0.5'' line?! I swear I saw 0.39'' on the seeing monitor, and we've had consistently 0.4-0.45'' seeing for over an hour. This means that we are more easily able to observe very faint stars, which will make our colleagues working on HAT-South and K2 transiting planet follow-up very happy. More about that soon.
