The Galactic Core

galactic coreWhen we look inward toward the center of the Milky Way, the galactic core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust. This composite false-color infrared image of the center of our galaxy reveals a new population of massive stars and new details in complex structures in the hot ionized gas swirling around the central 300 light-years.It combines the sharp imaging of the Hubble Space Telescope‘s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with color imagery from a previous Spitzer Space Telescope survey done with its Infrared Astronomy Camera (IRAC).

In this data astronomers see that the massive stars are not confined to one of the three known clusters of massive stars in the Galactic Center, known as the Central cluster, the Arches cluster, and the Quintuplet cluster. These three clusters are easily seen as tight concentrations of bright, massive stars in the image. The unattached stars may have formed in isolation, or they may have originated in clusters that have been disrupted by strong gravitational tidal forces.

The winds and radiation from these stars form the complex structures seen in the core, and in some cases, they may be triggering new generations of stars. IN the upper left large arcs of ionized gas form linear filaments suggesting the influence of locally strong magnetic fields.

The lower left region shows pillars of gas sculpted by winds from hot massive stars in the Quintuplet cluster.

Near the center of the image ionized gas surrounding the supermassive black hole at the center of the galaxy is confined to a bright spiral embedded in a circum-nuclear dusty donut-shaped torus.

Image Credit: NASA / ESA

A Spiral on Edge

From our point of view we see galaxy NGC 3432, directly edge-on. The galaxy’s spiral arms and bright core are mostly hidden, and we instead see the thin strip of its outer stars. The dark bands of cosmic dust, patches of varying brightness and pink regions of star formation help with making out the true shape of NGC 3432—which we can do because we see spiral galaxies at every kind of orientation, and experience allows us to identify spirals on edge.

Image Credit: NASA / ESA

A Star and a Nebula

A cosmic coupleThat’s the star Hen 2-427 (aka WR 124) at the center of this picture. It’s surrounded by the nebula M1-67. They’re found in the constellation of Sagittarius about 15,000 light-years away. The star shines brightly at the very center of these hot clumps of surrounding gas that it’s ejecting into space at over 150,000 km per hour.

Hen 2-427 is a Wolf–Rayet star. Named after the astronomers Charles Wolf and Georges Rayet, Wolf–Rayet stars are super-hot and characterized by a fierce ejection of mass. In this case, that results in the nebula M1-67 which is estimated to be less than 10,000 years old, a newbie in astronomical terms,

Image Credit: ESA

NGC 2022

NGC 2022 is a planetary nebula in the constellation Orion. In early telescopes (and in today’s medium-sized amateur telescopes) such nebulae look like small grayish patches of light. Since they don’t look like stars, but a bit like the gas giant planets, early astronomers tagged them as “planetary nebula,” and the name has stuck.

When stars like the Sun grow old, they expand into red giants. They then begin to lose their outer layers into space, forming a shell of gas. As the evolving star’s core shrinks and grows hotter, it emits ultraviolet light that causes the expelled gases to glow.

Image Credit: NASA / ESA

Messier 69

This is an image of the core fo the globular star cluster Messier 69. It is made up of visible light and infrared data taken by the Hubble Space Telescope. The cluster was discovered by Charles Messier in 1780. It’s located 29,700 light-years from Earth in the constellation Sagittarius. It’s too dim to be seen with the naked eye, but it can be viewed with a pair of binoculars, especially during August.

The stars in M69 have over ten times more iron than stars in other globular clusters of the same age. Iron is the heaviest element created by fusion in a star unless it explodes as a supernova.

Image Credit: NASA / ESA