Celebrating Hubble’s 25th Anniversary

In April, Hubble will celebrate a quarter-century in space. The telescope, launched into orbit in 1990, has become one of NASA’s most beloved and successful missions, its images changing our understanding of the universe and taking root in our cultural landscape. Hubble pictures have not only expanded our scientific knowledge, they have altered the way we imagine the cosmos to appear.

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Hubble took its iconic “Pillars of Creation” image of these star-forming clouds of gas and dust in the Eagle Nebula in 1995. Credit: NASA, ESA, STScI, J. Hester and P. Scowen (Arizona State University)

Hubble’s prolonged success has been a testament to its innovative design, which allowed it to be periodically updated by astronauts with new equipment and improved cameras. Hubble  has been able, to an extent, to keep up with technological changes over the past 25 years. The benefits are evident when comparing the images of the past and present.

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This new image of the Eagle Nebula’s “Pillars of Creation” was taken in 2014 to launch Hubble’s year-long celebration of its 25th anniversary. The image was captured with Wide Field Camera 3, an instrument installed on the telescope in 2009. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Hubble’s new instruments — specifically, the near-infrared capabilities of Wide Field Camera 3 — are what makes the Frontier Fields project possible. The faint infrared light of the most distant, gravitationally lensed galaxies sought in the Frontier Fields project would be beyond the reach of Hubble’s earlier cameras. Frontier Fields highlights Hubble’s continuing quest to blaze new trails in astronomy — and pave the path for the upcoming Webb Space Telescope — so it makes sense that its imagery is included in a collection of 25 of Hubble’s significant images, specially selected for the anniversary year.

The immense gravity in this foreground galaxy cluster, Abell 2744, warps space to brighten and magnify images of far-more-distant background galaxies as they looked over 12 billion years ago, not long after the big bang.  This is the first of the Frontier Fields to be imaged.

Abell 2744, the first of the Frontier Fields to be imaged, is part of Hubble’s 25th anniversary collection of top images. The immense gravity of the foreground galaxy cluster warps space to brighten and magnify images of far-more-distant background galaxies. Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)


The 25th birthday is a significant milestone, so Hubble is throwing a year-long celebration, with events happening in communities and online throughout 2015. Last week, Tony Darnell hosted a discussion of the beauty and scientific relevance of the Hubble 25th anniversary images, one of the many anniversary-themed Hubble Hangouts he’ll be doing as the months go on. To keep an eye on upcoming events, see the images, and learn about the science, visit our special 25th anniversary website, Hubble25th.org.

Cosmic Archeology

Today’s guest post is by Dr. Mario Livio, Hubble astrophysicist and author of the blog “A Curious Mind.” A version of this post appeared previously on Dr. Livio’s blog.

During the Christmas season of 1995, the Hubble Space Telescope was pointed for 10 consecutive days at an area in the sky not larger than the one you would see through a drinking straw. The region of sky, in the Ursa Major constellation, was selected so as to be as “boring” as possible — empty of stars in both our own Milky Way galaxy and in relatively nearby galaxies. The idea was for Hubble to take as deep an image of the distant universe as possible. The resulting image was astounding.  With very few exceptions, every point of light in this image is an entire galaxy, with something like 100 billion stars like the Sun.


The original Hubble Deep Field image.

Detailed analysis revealed that the very remote galaxies were physically smaller in size than today’s galaxies, and that their morphologies were more disturbed. Unlike the grand-design spirals or smooth elliptical shapes that we see in relatively close galaxies, the distant objects look like train wrecks. Both of these observations fit nicely into the idea that galaxies evolve largely by “mergers and acquisitions.” Small building blocks merge together to form larger ones, or cold flows of dark matter along dense filaments fuel the growth. What we see in the distant past are those interacting—and hence smaller and less regular in shape—building blocks.

Since then, Hubble observed even deeper, producing the “Hubble Ultra Deep Field” in 2004, and then in 2009 an image that included infrared observations taken with the new Wide Field Camera 3. This observation allowed astronomers to glimpse the universe at its infancy, when it was less than 500 million years old (the universe today is 13.8 billion years old). The Deep Field observations have also enabled researchers to reconstruct the history of global cosmic star formation. We now know that about 8 billion years ago the universe reached its peak in terms of the new star-birth rate, and that rate has been declining ever since — our universe is past its prime.


This tiny object in the Hubble Ultra Deep Field is a compact galaxy of blue stars that existed 480 million years after the Big Bang. Its light traveled 13.2 billion years to reach Hubble.

The Chandra X-ray Observatory has created its own Deep Field observations, discovering hundreds of low-luminosity active galactic nuclei, where disks feed mass onto central black holes, and emit copious x-ray radiation.

Infrared observations with the Spitzer Space Telescope completed the picture of the deepest images of the cosmos to date. Together, Hubble, Chandra, and Spitzer have created a detailed tapestry of a dynamic, evolving universe in which some two hundred billion galaxies are within the reach of our present telescopes.

Currently, Hubble is engaged in observing six new deep fields, each one centering on a galaxy cluster whose gravity can deflect, multiply, and magnify the light from more distant objects (the effect is known as “gravitational lensing”). In parallel, Hubble will also observe six deep “blank” fields. The goal is to use those so-called “Frontier Fields” to reveal populations of fainter galaxies, and to characterize the morphologies of distant star-forming galaxies.

The first of these super-deep views of the universe has already revealed almost 3000 of previously unseen, distant galaxies.

To see the very first galaxies that formed in our universe, we will have to await the James Webb Space Telescope, on schedule for launch in 2018. From a cosmic perspective, new discoveries are just around the corner!