Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all
NASA’s 28-year-old workhorse is still lighting up our knowledge and imagination of the Universe.
A generation ago, Hubble opened its eyes on the great cosmic abyss: viewing the depths of empty space.
If you look farther and farther away, you also look farther and farther into the past. The farthest we can see back in time is 13.8 billion years: our estimate for the age of the Universe. As we go farther back, we see the Universe as it was when it was younger, denser, less-evolved, and richer in new stars. (NASA / STSCI / A. FELID)
It wasn’t empty after all, but filled with thousands of faint, distant, galaxies across billions of light years.
The original Hubble deep field image, shown here, was taken by stacking dozens of images of an empty region of space and seeing what showed up. The answer was thousands of galaxies, revealing what our distant Universe looks like for the very first time. While for many of us, it feels like yesterday, this image is now nearly 25 years old. (R. WILLIAMS (STSCI), THE HUBBLE DEEP FIELD TEAM AND NASA)
As time and technology improved, we added infrared, X-ray, and other wavelengths to the picture.
A map of the 7 million second exposure of the Chandra Deep Field-South. This region shows hundreds of supermassive black holes, each one in a galaxy far beyond our own. The GOODS-South field was chosen to be centered on this original image. (NASA/CXC/B. LUO ET AL., 2017, APJS, 228, 2)
We discovered supermassive black holes, how galaxies formed and merged, and how the Universe grew up.
One of the most massive, distant galaxy clusters of all, MACS J0717.5+3745, was revealed by the Hubble Frontier Fields program. Behind these galaxy clusters, background galaxies are stretched, magnified, and brought into view by the gravitational lensing influence of the intervening matter. (NASA / STSCI / HUBBLE FRONTIER FIELDS)
Today, two trillion galaxies should exist within our observable Universe.
This is a portion of a deep sky Hubble Space Telescope survey called GOODS North, which includes four unusually red objects that appear as they existed just 500 million years after the Big Bang. This view was based on visible and infrared light. (NASA, ESA, G. ILLINGWORTH (UNIVERSITY OF CALIFORNIA, SANTA CRUZ), P. OESCH (UNIVERSITY OF CALIFORNIA, SANTA CRUZ; YALE UNIVERSITY), R. BOUWENS AND I. LABBÉ (LEIDEN UNIVERSITY), AND THE SCIENCE TEAM)
Most recently, Hubble released two new images of the ultra-deep, distant Universe.
The GOODS-North field, as seen in ultraviolet light, reveals some of the most distant star-forming galaxies ever seen by humanity. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
These are the GOODS-North and GOODS-South fields, as viewed in ultraviolet light.
A scaled-down-resolution view of the GOODS-South Field, which reveals thousands upon thousands of distant galaxies. This ultraviolet view helps showcase the brightest and most spectacular examples of star-formation in the nearby and distant Universe. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
Ultraviolet light is special, because it shows us where the newest, youngest stars are right now.
An enormous star-forming region in the dwarf galaxy UGCA 281, as imaged by Hubble in the visible and the ultraviolet, as part of the LEGUS survey. The blue light is starlight from hot, young stars reflected off of the background, neutral gas, while the brightest patches indicate the greatest emission of UV light. (NASA, ESA AND THE LEGUS TEAM)
When galaxies merge, interact, or collect infalling matter, a burst of new star formation ensues.
An impressive, relatively nearby grand design spiral as seen in the GOODS-North field. Star formation litters the spiral arms, as viewed in UV light, where it’s very clear that the outer arms of the galaxy are being tidally disrupted by an unseen source. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
These galaxies shine brightest in ultraviolet light, teaching us when stars form.
Galaxies that are currently undergoing gravitational interactions or mergers are almost always also forming new, bright, blue stars. Their irregular or perturbed shapes are a key signature that this is what’s occurring. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
Even at great cosmic distances, ultraviolet light — even if redshifted — reveals the presence of new stars.
The variety of colors, brightnesses, shapes, and distances that galaxies appear to have are indicative of the natural variations that the Universe exhibits. A huge amount of this can be seen in just a small portion of the GOODS-South ultraviolet image. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
Galaxy clusters, which bend the fabric of space, can magnify and stretch otherwise unseeable background galaxies.
The GOODS-North field contains a massive galaxy cluster within it, as shown by the reddish galaxies, which stretch and magnify the light from the more-distant galaxies seen faintly in the background. This phenomenon of gravitational lensing serves as the Universe’s most powerful natural telescope. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
It now appears star formation peaked when the Universe was just 3 billion years old.
At a wide variety of distances, new stars form, emitting a tremendous amount of energy in the ultraviolet part of the spectrum. Faint, redder galaxies seen here can also be part of the star-forming population, as the expansion of the Universe affects the starlight on its journey to our eyes. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
But new stars are born, slowly, even today.
Two nearby galaxies as seen in the ultraviolet view of the GOODS-South field, one of which is actively forming new stars (blue) and the other which is just a normal galaxy. In the background, distant galaxies can be seen with their stellar populations as well. Even though they’re rarer, there are still late-time galaxies actively forming massive amounts of new stars. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
Mostly Mute Monday tells the astronomical story of an object, phenomenon, or view of the Universe in visuals, images, and no more than 200 words. Talk less; smile more.
