Trunkneck’s Blog

In commemoration of NASA’s Hubble Space Telescope completing its 100,000th orbit in its 18th year of exploration and discovery, scientists at the Space Telescope Science Institute in Baltimore, Md., have aimed Hubble to take a snapshot of a dazzling region of celestial birth and renewal.

This representative color image of the Large Magellanic Cloud cluster NGC 2074 was taken on August 10, 2008, with Hubble’s Wide Field Planetary Camera 2. Red shows emission from sulfur atoms, green from glowing hydrogen, and blue from glowing oxygen.

Hubble peered into a small portion of the nebula near the star cluster NGC 2074 (upper, left). The region is a firestorm of raw stellar creation, perhaps triggered by a nearby supernova explosion. It lies about 170,000 light-years away near the Tarantula nebula, one of the most active star-forming regions in our Local Group of galaxies.

The three-dimensional-looking image reveals dramatic ridges and valleys of dust, serpent-head “pillars of creation,” and gaseous filaments glowing fiercely under torrential ultraviolet radiation. The region is on the edge of a dark molecular cloud that is an incubator for the birth of new stars.

Hubble’s Location at 100,000th Orbit Milestone (Artist’s Illustration) NASA’s Hubble Space Telescope reached a milestone of 100,000 orbits at 7:42 a.m. EDT on Monday, August 11, 2008. At that time the telescope was flying above the midway point of the Pacific Ocean and directly over the equator, heading northward. Hubble completes an orbit around Earth approximately once every 90 minutes.

The high-energy radiation blazing out from clusters of hot young stars already born in NGC 2074 is sculpting the wall of the nebula by slowly eroding it away. Another young cluster may be hidden beneath a circle of brilliant blue gas at center, bottom.

In this approximately 100-light-year-wide fantasy-like landscape, dark towers of dust rise above a glowing wall of gases on the surface of the molecular cloud. The seahorse-shaped pillar at lower, right is approximately 20 light-years long, roughly four times the distance between our Sun and the nearest star, Alpha Centauri.

The region is in the Large Magellanic Cloud (LMC), a satellite of our Milky Way galaxy. It is a fascinating laboratory for observing star-formation regions and their evolution. Dwarf galaxies like the LMC are considered to be the primitive building blocks of larger galaxies.

This representative color image was taken on August 10, 2008, with Hubble’s Wide Field Planetary Camera 2. Red shows emission from sulfur atoms, green from glowing hydrogen, and blue from glowing oxygen.

Credit: NASA, STScI, and M. Livio (STScI)

Globular star clusters, dense bunches of hundreds of thousands of stars, have some of the oldest surviving stars in the universe. A new study of globular clusters outside our Milky Way Galaxy has found evidence that these hardy pioneers are more likely to form in dense areas, where star birth occurs at a rapid rate, instead of uniformly from galaxy to galaxy.

These images taken by NASA’s Hubble Space Telescope show four members of the Virgo cluster of galaxies, the nearest large galaxy cluster to Earth. +They are part of a survey of globular star clusters in 100 of Virgo’s galaxies. %0AGlobular clusters, dense bunches of hundreds of thousands of stars, have some of the oldest surviving stars in the universe. Most of the star clusters in the Virgo survey are older than 5 billion years. +The Hubble study found evidence that these hardy pioneers are more likely to %0Aform in dense areas, where star birth occurs at a rapid rate, instead of uniformly from galaxy to galaxy. Hubble’s “eye” is so sharp that it was able to pick out the fuzzy globular clusters, %0Awhich, at that distance, look like individual stars bunched up around the galaxies, instead of groupings of stars. Comprised of over 2,000 galaxies, the Virgo cluster is located about 54 million light-years away. +Astronomers made these composite images from the advanced camera’s full field-of-view observations. They also used modeling data to fill in a narrow gap %0Abetween the camera’s detectors. The images were taken from December 2002 to December 2003.

Astronomers used NASA’s Hubble Space Telescope to identify over 11,000 globular clusters in the Virgo cluster of galaxies. Most are older than 5 billion years. The sharp vision of Hubble’s Advanced Camera for Surveys resolved the star clusters in 100 galaxies of various sizes, shapes, and brightnesses, even in faint, dwarf galaxies. Comprised of over 2,000 galaxies, the Virgo cluster is the nearest large galaxy cluster to Earth, located about 54 million light-years away.

Astronomers have long known that the giant elliptical galaxy at the cluster’s center, M87, hosts a larger than predicted population of globular star clusters. The origin of so many globulars has been a long-standing mystery.

“Our study shows that the efficiency of star cluster formation depends on the environment,” said Patrick Cote of the Herzberg Institute of Astrophysics in Victoria, British Columbia. “Dwarf galaxies closest to Virgo’s crowded center contained more globular clusters than those farther away.”

The team found a bounty of globular clusters in most dwarf galaxies within 3 million light-years of the cluster’s center, where the giant elliptical galaxy M87 resides. The number of globulars in these dwarfs ranged from a few dozen to several dozen, but these numbers were surprisingly high for the low masses of the galaxies they inhabited. By contrast, dwarfs in the outskirts of the cluster had fewer globulars. Many of M87’s star clusters may have been snatched from smaller galaxies that ventured too close to it.

“We found few or no globular clusters in galaxies within 130,000 light-years from M87, suggesting the giant galaxy stripped the smaller ones of their star clusters,” explained Eric Peng of Peking University in Beijing, China, and lead author of the Hubble study. “These smaller galaxies are contributing to the buildup of M87.”

Hubble’s “eye” is so sharp that it was able to pick out the fuzzy globular clusters from stars in our galaxy and from faraway galaxies in the background. “It’s hard to distinguish globular clusters from stars and galaxies using ground-based telescopes,” Peng said.

“With Hubble we were able to identify and study about 90 percent of the globular clusters in all our observed fields. This was crucial for dwarf galaxies that have only a handful of star clusters.”

Evidence of M87’s galactic cannibalism comes from an analysis of the globular clusters’ composition. “In M87 there are three times as many globulars deficient in heavy elements, such as iron, than globulars rich in those elements,” Peng said. “This suggests that many of these ‘metal-poor’ star clusters may have been stolen from nearby dwarf galaxies, which also contain globulars deficient in heavy elements.”

Studying globular star clusters is critical to understanding the early, intense star-forming episodes that mark galaxy formation. They are known to reside in all but the faintest of galaxies.

“Star formation near the core of Virgo is very intense and occurs in a small volume over a short amount of time,” Peng noted. “It may be more rapid and more efficient than star formation in the outskirts. The high star-formation rate may be driven by the gravitational collapse of dark matter, an invisible form of matter, which is denser and collapses sooner near the cluster’s center. M87 sits at the center of a large concentration of dark matter, and all of these globulars near the center probably formed early in the history of the Virgo cluster.”

The fewer number of globular clusters in dwarf galaxies farther away from the center may be due to the masses of the star clusters that formed, Peng said. “Star formation farther away from the central region was not as robust, which may have produced only less massive star clusters that dissipated over time,” he explained.