About the Law Astronomy Group
We are experimental astrophysicists: we build new astronomical instruments, and use them to search for and understand new astronomical phenonema. My group’s research is currently focused on ongoing science programs with the Evryscopes, the first all-sky gigapixel-scale telescopes.
Argus Array
The Argus Array, being developed by our group at UNC Chapel Hill, is a large (5m-aperture-equivalent) telescope consisting of 800 moderate-aperture, off-the-shelf telescopes multiplexed into a common hemispherical dome.
The Evryscopes
The Evryscopes are array telescopes that cover the entire visible sky in each and every exposure. Based in the mountains of Chile and California, the systems together take a 1.3 Gigapixel image of the sky every two minutes.
Teaching
Depending on the semester, I teach ASTR101 (introductory astronomy), ASTR202 (general undergraduate astrophysics) or ASTR519/719 (upper-level astronomical data analysis). I have also developed and teach ASTR502, a research-based high-impact experience course which is part of UNC's CURE (Course-based Undergraduate Research Experiences) program.
Astrophysics
My group explores the dynamic sky recorded by our in-house instruments, while using large telescopes for around the world for follow-up and confirmation of our discoveries. Some recent results:
We recently detected the first optical superflare seen from Proxima Centauri (Howard et al. 2018), where the nearest star to our Sun (also the nearest potential habitable exoplanet host star) briefly got almost 100x brighter. Each Proxima superflare produces a tremendous amount of UV light that impacts the potential habvitability of planets exposed to it.
In Glazier et al. 2020 we explored the habitability of the planets of the TRAPPIST-1 system, based on the superflare rates contrained by Evryscope and other surveys. We found that TRAPPIST-1's low flare rates likely do not damage the atmosphere of its habitable planets, but are also potentially too low to allow the early synthesis of RNA, making Earth-like life difficult to start.
We are using the Evryscopes to explore the minute-timescale transient and moving-objects sky, from near-Earth objects to gamma ray bursts across the visible universe. With our collaborators around the world, we are using the Evryscopes' datasets to search for graviational wave counterparts, characterize galactic transients, and many other topics.
In a series of papers, we have been exploring the short- and long-term variability of hot subdwarfs (the exposed cores of giant stars) and white dwarfs. We recently found a white dwarf caught in the act of formation (other results out soon).
In a series of papers, we are measuring the incidence of exoplanet-habitability-affecting superflares across the sky seen by the Evryscopes. Our survey focuses on those where we have simultaneous TESS coverage, which provides complementary shorter-term, higher-precision observations of potential habitable exoplanet hosts.
Using Robo-AO, we led the largest search for stellar companions to Kepler planet hosts, finding 620 nearby stars around 3857 planetary candidates host stars. Each of those stars affects the planetary formation environment and even the . Carl Ziegler, previous group member, is now continuing this survey for TESS using SOAR Speckle.
Instruments
My group explores the dynamic sky recorded by instruments we have built and participated in, while using large telescopes for around the world for follow-up and confirmation of our discoveries. Some of the main systems we have worked on are:
The Evryscopes, designed, built and operated by our group, are first gigapixel-scale all-sky telescopes, and are based in Chile and California. They cover ~16,000 square degrees in each exposure, monitoring most of the accessible sky every two minutes. The detailed instrument design can be found in this paper, and the project news and updates are on the main Evryscope website.
Robo-AO is the first robotic laser-guide-star adaptive optics system. Built at Caltech, and operating at Palomar Observatory, Kitt Peak, and soon Mauna Kea, the system achieves Hubble-Space-Telescope resolution in the visible from the ground. The system has produced over 40 refereed scientific publications, along with many technical development papers.
Our group, especially including Carl Ziegler (now a Dunlap Postdoctoral Fellow at U. Toronto), and our collaborator Andrei Tokovinin, has been exploring low-cost ways of achiving diffraction-limited visible-light adaptive optics on 4m-class telescopes like SOAR.
The Arctic Wide-field Cameras were experimental systems operating near the North Pole, in the Canadian High Arctic. Using the continuous winter darkness, the systems survived -40C temperatures and hurricane-force winds over two Arctic winters, taking 40TB of data (which will shortly be available via the Evryscope data distribution systems).
The Palomar Transient Factory (PTF; Project Scientist N. Law, PI Shri Kulkarni) was a fully-automated, wide-field survey aimed at a systematic exploration of the optical transient sky. The transient survey was performed using a new 8.1 square degree camera installed on the 48-inch Samuel Oschin telescope at Palomar Observatory; colors and light curves for detected transients are obtained with the automated Palomar 60-inch telescope.T he Palomar Transient Factory found thousands of supernovae and produced over 100 scientific papers.
LuckyCam was the first faint-object-capable lucky imaging system. The first astronomical use of single-photon-capable electron-multiplying CCDs, the University-of-Cambridge developed (PI: Craig Mackay) system demonstrated diffraction-limited performance in the visible on 2m-aperture telescopes at very low cost (my PhD thesis on Luckycam is here). Our follow-on system, LAMP, held the record for highest-resolution visible-light imaging for many years.
Nick Law's CV and Publication List
