SIM Key Project at Dartmouth

Anchoring the Population II Distance Scale: Accurate Ages for Globular Clusters and Field Halo Stars

Globular Cluster Picture
SIM is a telescope scheduled for launch in 2008 by NASA which will measure the positions and distances to stars several hundred times more accurately than the current capability. This mission is designed to answer such questions as: How old is the universe? How big is it? Are there other planets like the Earth around nearby stars? To answer these questions, NASA has selected a number of key projects, which will be given a substantial fraction of the observing time on SIM. One of these key projects is headquarted at Dartmouth, and is designed to determine the distances and ages of the oldest stars in the galaxy. This project will determine an accurate estimate for the minimum age of the universe, help calibrate the zero point of the extragalactic distance scale and will further our knowledge of the how the Milky Way was formed.

To the left is a picture of the globular cluster 47 Tucanae. This is a collection of ancient stars in orbit about the Milky Way. Our key project will determine the distance to this cluster to an accuracy of 2%, allowing us to determine its age to an accuracy of 6%. Further details of the project are given below.

A summary of the key project

A copy of the proposal submittted to NASA (PDF, 923Kb)

Personnel involved in the key project

Team Web Site (restricted access)

[Department of Physics & Astronomy] [Dartmouth College]