Lowell Observatory

An image of M33 (the Triangulum Galaxy), obtained by Lowell astronomer Phil Massey and his colleagues as part of their Local Group Survey.

The Masses of Bright Stars

Healthy, stable stars like the Sun obey a well-known property: the more massive they are, the brighter they are. Mass is the Rosetta Stone of understanding a star, the one quantity that we would most like to know, and the one that is hardest to determine. So it sounds simple: measure a star's brightness, and you know the mass.

For a variety of reasons, it's not that simple, and one of those reasons is that the so-called mass-luminosity relationship is not well determined for the most massive stars -- the bright O and B type stars. Competing methods of stellar spectral analysis give different expected masses for stars of a given type.

Why? Which model is right, and which is wrong? Lowell's Phil Massey will attack the problem by studying some of the very few stars for which we can obtain good masses: eclipsing binaries. He will do both imaging and spectroscopy of these stars in nearby galaxies in the Local Group. With solid data for both mass and brightness, Phil will be able to determine which of the M-L theories is correct, and nail down one of the most fundamental properties of massive main-sequence stars.