Hubble Finds More Interesting Stuff

New data from the Spitzer and Hubble space telescopes show that in particular wavelengths of infrared light, some of the first galaxies to form in the Universe (less than 1 billion years after the Big Bang) were considerably brighter than astronomers anticipated.

No one yet knows for sure when the first stars in our Universe burst to life. Evidence suggests that between 100 million and 200 million years after the Big Bang, the Universe was filled mostly with neutral hydrogen gas that had perhaps just begun to coalesce into stars, which then began to form the first galaxies.

By about 1 billion years after the Big Bang, the Universe had become a sparkling firmament. Something else had changed, too: electrons of the omnipresent neutral hydrogen gas had been stripped away in a process known as ionization.

The Epoch of Reionization, the changeover from the Universe full of neutral hydrogen to one filled with ionized hydrogen, is well documented.

Before this Universe-wide transformation, long-wavelength forms of light, such as radio waves and visible light, traversed the Universe more or less unencumbered. But shorter wavelengths, including ultraviolet light, X-rays and gamma rays, were stopped short by neutral hydrogen atoms. These collisions would strip the neutral hydrogen atoms of their electrons, ionizing them.

But what could have produced enough ionizing radiation to affect all the hydrogen in the Universe? Was it individual stars? Giant galaxies?

If either were the culprit, those early cosmic colonizers would have been different than most modern stars and galaxies, which typically don’t release high amounts of ionizing radiation. Then again, perhaps something else entirely caused the event, such as quasars.

Researchers found that early galaxies were particularly bright in two specific wavelengths of infrared light produced by ionizing radiation interacting with hydrogen and oxygen gases within the galaxies. This implies that the galaxies were dominated by young, massive stars composed mostly of hydrogen and helium. They contain very small amounts of heavy elements, like nitrogen, carbon and oxygen, compared to stars found in modern galaxies.

These stars were not the first stars to form in the Universe (those would have been composed of hydrogen and helium only) but were still members of very early generations of stars.

The Epoch of Reionization wasn’t an instantaneous event, so while the new results are not enough to close the book on this cosmic event, they do provide new details about how the Universe evolved during this time and how the transition played out.

The findings are published in the Monthly Notices of the Royal Astronomical Society.

Sometimes the Abyss Stares Back

Astronomers have produced the largest, most comprehensive ‘history book’ of galaxies in the Universe, using 16 years’ worth of observations from the NASA/ESA Hubble Space Telescope. The endeavor is called the Hubble Legacy Field. The image, a combination of nearly 7,500 separate Hubble exposures, contains roughly 265,000 galaxies and stretch back through 13.3 billion years of time to just 500 million years after the Universe’s birth in the Big Bang.


The Hubble Legacy Field combines observations taken by several Hubble deep-field surveys. In 1995, the Hubble Deep Field captured several thousand previously unseen galaxies. The subsequent Hubble Ultra Deep Field from 2004 revealed nearly 10,000 galaxies in a single image. The 2012 Hubble eXtreme Deep Field was assembled by combining ten years of Hubble observations taken of a patch of sky within the original Hubble Ultra Deep Field.

The new set of Hubble images, created from nearly 7,500 individual exposures, is the first in a series of Hubble Legacy Field images.

Happy Birthday Hubble

In celebration of the 29th anniversary of the launch of the NASA/ESA Hubble Space Telescope, astronomers captured this colorful look at the hourglass-shaped Southern Crab Nebula.

On April 24, 1990, Hubble was launched on the space shuttle Discovery. It has since revolutionized how astronomers and the general public see the Universe. The images it provides are spectacular from both a scientific and a purely aesthetic point of view.

Each year the telescope dedicates a small portion of its precious observing time to take a special anniversary image, focused on capturing particularly beautiful and meaningful objects. This year’s image is the Southern Crab Nebula, and it is no exception.

This incredible image of the Southern Crab Nebula was taken to mark Hubble’s 29th anniversary in space. Image credit: NASA / ESA / STScI.

The Southern Crab Nebula resides in the southern constellation Centaurus, approximately 7,000 light-years from Earth. It is so named to distinguish it from the better-known Crab Nebula, a supernova remnant visible in the constellation of Taurus.

The object appears to have two nested hourglass-shaped structures that were sculpted by a whirling pair of stars in a binary system. The duo consists of an aging red giant star and a white dwarf. The red giant is shedding its outer layers. Some of this ejected material is attracted by the gravity of the companion white dwarf.

The Southern Crab Nebula was assumed to be an ordinary star until 1989, when it was observed using telescopes at ESO’s La Silla Observatory.

The resulting image showed a roughly crab-shaped extended nebula, formed by symmetrical bubbles of gas and dust. Those observations only showed the outer hourglass emanating from a bright central region that could not be resolved.

It seems fitting that Hubble has returned to this object twenty years after its first observation. The new image adds to the story of an active and evolving object and contributes to the story of Hubble’s role in our evolving understanding of the Universe.