Overview

The pictures above are an artist's (Dr. Robert Hurt) visualization to scale of what we believe the Sun, a very-low-mass (M9 dwarf) star, an L-type brown dwarf, a T-type brown dwarf, and the planet Jupiter would look like if we could line them all up. It's odd but true that the smallest stars, the largest planets, and the brown dwarfs in between are all about the same size even though the star is eighty times more massive than Jupiter! My research is aimed at better understanding all these types of objects.

You can get an idea of what I'm working on now by checking out my Daily Research Blog.

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Stars

Most stars are much dimmer and less luminous than the Sun. "M dwarfs" are the most common type, and I have worked on discovering and characterizing them using a wide variety of space and ground-based telescopes.

Brown Dwarfs

Brown dwarfs are "failed" stars that don't become hot in their core to fuse hydrogen. Without a fusion energy source, they are doomed to fade and cool, and this makes them difficult to study. I am currently investigating the atmospheric properties of a nearby L brown dwarf using Kepler and searching for brown dwarfs with WISE.

Planets

If the Sun is just another star, it's easy to imagine that the stars are also suns, with their own planetary systems. Iam working on a search for wide, giant planets with Ray Jayawardhana's group. I have some other ideas on finding planets which I will investigate over the next year.

New neighbors

Image of Brown Dwarf WISEP J180026.60+013453.1

Many of the closest brown dwarfs are still unknown. I am searching for overlooked nearby stars and brown dwarfs using the NASA's WISE Mission. One such new neighbor is WISEP J180026.60+013453.1. This brown dwarf is 1400K and only about 29 lightyears from us. The image above shows the 2MASS near-infrared image taken in 2000. The two circles mark the position of the brown dwarf to where WISE saw it in 2010. The large motion is characteristic of objects near the Sun.

LSST

Design image of LSST telescope

The top-ranked ground-based project 2010 Astronomy Decadal Survey aims to repeatedly survey the sky with an 8-meter telescope. I am working on simulations of the astrometric properties of the LSST.

Kepler K2

Kepler K2 picture

NASA's Kepler K2 mission is surveying large regions of the sky at unprecedented photometric precision and time coverage. I have lead successful proposals to use this space telescope to study 'ultracool' L dwarfs. We hope to detect white light flares, 'weather' due to changing mineral clouds, and possibly even transits due to orbiting planets.

Magnetic Activity

A star (or even a brown dwarf) can generate magnetic fields through a dynamo process, which in turns heats the outer atmosphere, called the chrmosphere and corona. Currently I am working on a project with Edo Berger to study the coronae of M6-type dwarfs with Chandra. In another project with Jim MacDonald, I am studying active M dwarfs with Kepler.

M Subdwarf Stars

I developed the M subdwarf classification system and I remain interested in these very metal-poor halo stars. Because they have such long lifetimes they are a fossil record of the formation of the Galaxy.

Disks

Mid-Infrared space observatories like Spitzer, WISE,Herschel and AKARI allow cool material orbiting around stars to be studied directly. When the stars or brown dwarfs are very young, they have primordial disks that should often form planets. For example, my group showed the brown dwarf 2M1207 has a "T Tauri" type disk. Older stars may have debris disks that are formed by the collisions of asteroids and comets.