Happy 25th Birthday, Hubble

This animation provides a 3D perspective on Hubble‘s 25th anniversary image of the nebula Gum 29 and the star cluster Westerlund 2 at its core. It begins fly past foreground stars and approaches the rim of the nebula. After passing through the wispy darker clouds on the near side, the simulation shows the bright gas illuminated by the intense radiation of the new stars forming in the Westerlund 2 cluster. The pillars of dark, dense gas are being sculpted by light and strong stellar winds from thousands of stars. This visualization is intended to be a scientifically reasonable interpretation, but distances within the model have been significantly compressed.

Video Credit: NASA, ESA, G. Bacon, L. Frattare, Z. Levay, and F. Summers (Viz3D Team, STScI), and J. Anderson (STScI)
Acknowledgment: The Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), the Westerlund 2 Science Team, and ESO


The crammed centre of Messier 22This is the center of the globular cluster Messier 22 as seen by the Hubble Space Telescope. Globular clusters are more-or-less spherical collections of densely packed stars; they are relics of the early years of the Universe with ages of in the range of 12 to 13 billion years. The Universe is only 13.8 billion years old.

M22 is one of about 150 globular clusters in the Milky Way, and it is also one of the closest to Earth, only about 10,000 light-years away. The cluster has a diameter of about 70 light-years and appears to take up a patch of sky the size of the full Moon. However, the light from the stars in the cluster is not very bright because it is dimmed by dust and gas between the solar system and the cluster.

M22 in particular has some fascinating features: six planet-sized objects that are not orbiting a star have been detected in the cluster, and it contains two black holes.

Image Credit: ESA/NASA

Cosmic Yardsticks

A cosmological measuring tapeThis is the spiral galaxy NGC 3021 which lies about 100 million light-years away in the constellation of Leo Minor (The Little Lion).

This galaxy contains several Cepheid variable stars which can be used work out the distance to the galaxy. These stars pulsate at a rate that is closely related to their intrinsic brightness. Measurements of their rate of pulsation and their observed brightness provide information used to calculate the distance to them and, thus, the galaxy itself.

NGC 3021’s Cepheids were also used to calibrate another even brighter distance marker that can be used over greater distances: a Type Ia supernovae. One of these bright explosions was observed in NGC 3021 in 1995.

Image Credit: ESA