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The Hubble Space Telescope is one of the most productive scientific instruments ever built. The observatory launched in 1990 as a joint project between NASA and the European Space Agency (ESA). Since then it has been supplying scientists with invaluable data and images of stars, planets and galaxies. The latest findings from Hubble, released last week, go 2.5 billion years further back in cosmic time than before, providing the most comprehensive view of the universe yet.
Astronomers now are able to see the shapes, sizes and colors of galaxies over the last 80% of the universe's history, thanks to newly obtained observations from Hubble's Cosmic Assembly Near-infrared Extragalactic Legacy Survey (CANDELS). The latest study found that the Hubble Sequence, a method used to categorize galaxies into a variety of different forms, can be applied as far back as 11 billion years ago. According to the ESA, larger samples of panchromatic images from CANDELS confirm that even the oldest galaxies fit into the different classifications of the sequence.
The long-term, space-based Hubble observatory collects data, or spectra, and takes pictures as it circles the Earth at 17,500 miles an hour. From its vantage point, it can observe near-infrared and ultraviolet light, which puts ground-based telescopes at a disadvantage. Also, unlike ground-based telescopes, Hubble's primary mirror measures seven feet, allowing it to gaze deep into space with clarity. Astronomers achieved their latest discovery by using Hubble's Wide Field Camera 3 (WFC3) to look in the infrared part of the spectrum to analyze a larger number of these galaxies.
"The huge CANDELS data set was a great resource for us to use in order to consistently study ancient galaxies in the early universe," said BoMee Lee of the University of Massachusetts, who is the lead author of a new paper exploring the sequence. "And the resolution and sensitivity of Hubble's WFC3 is second to none in the infrared wavelengths needed to carry out this study. The Hubble Sequence underpins a lot of what we know about how galaxies form and evolve -- finding it to be in place this far back is a significant discovery."
During its 20 years in space, the Hubble Space Telescope has made more than 930,000 observations and captured over 570,000 images of 30,000 celestial objects. These observations have produced more than 45 TB of data. On average, the 24,500-pound, 43.5-foot-long telescope generates more than 360 GB of data each month. The data has been used as a basis for more than 8,700 scientific papers, making Hubble an extremely valuable scientific tool.
Keep reading for Hubble's detailed images that teach us about galaxies 11 billion years ago.
Photos credit: NASA, ESA
Galaxies, the building blocks of the universe, range from simple to very complex in structure. In 1926, American astronomer Edwin Hubble developed a classification scheme of galaxies, more commonly known as the Hubble tuning fork. The basic ideas still hold today in helping astronomers understand the theory of galaxy evolution. The diagram pictured is split into two parts: elliptical galaxies, or ellipticals, and spiral galaxies, or spirals. Hubble assigned ellipticals numbers from zero to seven, while spirals were given letters. It is now believed that galaxy evolution is much more complicated than Hubble's classification scheme.
Displayed in this Hubble tuning fork diagram is a sliver of the universe today. The diagram separates the universe into spiral, elliptical and lenticular galaxies. The ellipticals are illustrated on the left, the spirals are on the right, and the lenticulars are in the middle. "Our local universe displays big, fully formed and intricate galaxy shapes," said ESA. Present-day galaxies vary in form and are classified via a system called the Hubble Sequence, which categorizes galaxies according to their morphology and star-forming activity.
Like the previous image, this Hubble tuning fork diagram splits galaxies according to their morphology into spiral, elliptical and lenticular galaxies. But unlike today's galaxies, these are small and still not fully formed. They do, however, have distinct color and structure. "This is a key question: when and over what timescale did the Hubble Sequence form? To do this you need to peer at distant galaxies and compare them to their closer relatives, to see if they too can be described in the same way," said author Lee.
Astronomers used the Hubble Space Telescope to look back in time at a very young universe, in hopes of understanding the anatomy of distant galaxies. This piece of the universe is approximately 11 billion years old. At these distances, the galaxies are small and still forming. Astronomers were surprised to discover that the galaxies look a lot more mature than previously predicted by galaxy formation models.
This image compiles different times in the history of the universe: present day, 4 billion years ago and 11 billion years ago. The side-by-side comparison shows astonishing differences between the galaxies. The image of the universe today shows big, fully formed and elaborate galaxy shapes. Going back in time, the galaxies become smaller and less mature, as they're in the process of forming. The galaxies at earlier times are split between blue star-forming galaxies with a more intricate structure -- such as discs and bulges -- and colossal red galaxies that are no longer forming stars.