Search Publications
Discovery of a supernova explosion at half the age of the Universe
Panagia, N.; Lidman, C.; Aldering, G. +19 more
The ultimate fate of the Universe, infinite expansion or a big crunch, can be determined by using the redshifts and distances of very distant supernovae to monitor changes in the expansion rate. We can now find large numbers of these distant supernovae, and measure their redshifts and apparent brightnesses; moreover, recent studies of nearby type …
Detection of intergalactic red-giant-branch stars in the Virgo cluster
Ferguson, Henry C.; von Hippel, Ted; Tanvir, Nial R.
It has been suspected for nearly 50 years that galaxy clusters contain a population of intergalactic stars ripped from the galaxies during cluster formation, or when the galactic orbits pass through the cluster centre. Observational support for theexistence of such a stellar population is provided both by measurements of the diffuse light in clust…
Birth and early evolution of a planetary nebula
Bobrowsky, Matthew; Sahu, Kailash C.; Parthasarathy, M. +1 more
The final expulsion of gas by a star as it forms a planetary nebula - the ionized shell of gas often observed surrounding a young white dwarf - is one of the most poorly understood stages of stellar evolution,. Such nebulae form extremely rapidly (about 100 years for the ionization) and so the formation process is inherently difficult to observe. …
Global warming on Triton
Olkin, C. B.; Franz, O. G.; Buie, M. W. +11 more
Triton, Neptune's largest moon, has been predicted to undergo significant seasonal changes that would reveal themselves as changes in its mean frost temperature. But whether this temperature should at the present time be increasing, decreasing or constant depends on a number of parameters (such as the thermal properties of the surface, and frost m…
A Cepheid distance to the Fornax cluster and the local expansion rate of the Universe
Illingworth, Garth D.; Madore, Barry F.; Freedman, Wendy L. +13 more
Both galaxy distances and velocities are required for the determination of the expansion rate of the Universe, as described by the Hubble constant H0. The radial velocities of galaxies arise not just from this expansion but also from random components and large-scale flows. To reach out to distances dominated by the overall cosmic expan…
Constraints on the Hubble constant from observations of the brightest red-giant stars in a Virgo-cluster galaxy
Harris, William E.; Durrell, Patrick R.; Pierce, Michael J. +1 more
The nearest large groups of elliptical galaxies, in the Virgo and Fornax clusters, play a central role in determinations of the Hubble constant, H0, and hence the cosmological rate of expansion. Because the relative distances between these two clusters and more remote clusters are well known, absolute distance determinations to Virgo an…
Star formation triggered by galaxy collisions
Lutz, Dieter; Genzel, Reinhard; Tacconi, Linda
It is becoming increasingly clear that collisions between galaxies play an important role in galaxy evolution. The ultraluminous infrared galaxies are predominantly powered by enormous star-formation events that are triggered in the last phases of such collisions. These bursts occur just before the galaxies merge to form single elliptical galaxies.
The optical counterparts of γ-ray bursts
Harrison, Thomas E.; McNamara, Bernard J.
The origin of γ-ray bursts-which are among the most energetic events in the Universe-has puzzled astronomers for 25 years. Since 1991, new events have been discovered at a rate of about one per day, but because their positions were poorly determined, the objects responsible for these outbursts could not be identified. Now, following the launch of …