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Starts With A Bang

What we’ve learned after 32 years of NASA’s Hubble

When the Hubble Space Telescope first launched in 1990, there was so much we didn't know. Here's how far we've come.
every square degree
Every time we look out at the night sky, we're seeing a specific field-of-view, which means we're probing a certain amount of area on the sky. Objects that are nearby, at intermediate distances, and even at very great distances can all appear in the same image, and just how faint and far back we see is limited only by the quality of our observations.
(Credit: NASA/ESA/A. Feild (STScI))
Key Takeaways
  • When the Hubble Space Telescope launched on April 24, 1990, there was so much we still didn't know about the Universe.
  • We had never seen baby galaxies, exoplanets, didn't know about dark energy, and had a 100% uncertainty in how fast the Universe was expanding.
  • Over the past 32 years, we've uncovered and discovered so much. Excitingly, in many ways, the journey to the beginning of the Universe is only getting started.

On April 24, 1990, NASA launched the Hubble Space Telescope into Earth’s orbit.

This photo shows the Hubble Space telescope being deployed, on April 25, 1990, one day after its launch. It was taken by the IMAX Cargo Bay Camera (ICBC) mounted aboard the space shuttle Discovery. It has been operational for 32 years, and has not been serviced since 2009. With a 2.4-meter diameter mirror, it gathers as much light in 1 minute as a 160-mm (6.3″) telescope would require 3 hours and 45 minutes to gather.
(Credit: NASA/Smithsonian Institution/Lockheed Corporation)

Originally, a flaw in the optics led to disappointingly blurry images.

The before-and-after difference between Hubble’s original view (left) with the mirror flaws, and the corrected images (right) after the proper optics were applied. The first servicing mission, in 1993, brought the true power of Hubble to the forefront of astronomy, where it’s remained ever since.
(Credit: NASA/STScI)

But subsequent servicing missions transformed Hubble into the epic observatory we all know.

Pluto, shown as imaged with Hubble in a composite mosaic, along with its five moons. Charon, its largest, must be imaged with Pluto in an entirely different filter due to their brightnesses. The four smaller moons orbit this binary system with a factor of 1,000 greater exposure time in order to bring them out. Nix and Hydra were discovered in 2005, with Kerberos discovered in 2011 and Styx in 2012.
(Credit: NASA, ESA, and M. Showalter (SETI Institute))

As it has shown us the Universe, we’ve answered many of our deepest questions.

This deep-field region of the GOODS-South field contains 18 galaxies forming stars so quickly that the number of stars inside will double in just 10 million years: just 0.1% the lifetime of the Universe. The deepest views of the Universe, as revealed by Hubble, take us back into the early history of the Universe, where star formation was much greater, and to times where most of the Universe’s stars hadn’t even formed.
(Credit: NASA, ESA, A. van der Wel (Max Planck Institute for Astronomy), H. Ferguson and A. Koekemoer (Space Telescope Science Institute), and the CANDELS team)

We didn’t know what was out there in the deepest depths of space.

unreachable
The Hubble eXtreme Deep Field (XDF) may have observed a region of sky just 1/32,000,000th of the total, but was able to uncover a whopping 5,500 galaxies within it: an estimated 10% of the total number of galaxies actually contained in this pencil-beam-style slice. The remaining 90% of galaxies are either too faint or too red or too obscured for Hubble to reveal, but when we extrapolate over the entire observable Universe, we expect to obtain a total of ~2 trillion galaxies.
(Credit: HUDF09 and HUDF12 teams; Processing: E. Siegel)

We had never seen an infant galaxy before.

James Webb Hubble
Only because this distant galaxy, GN-z11, is located in a region where the intergalactic medium is mostly reionized, can Hubble reveal it to us at the present time. To see further, we require a better observatory, optimized for these kinds of detection, than Hubble. Although the galaxy appears very red, that’s only due to the redshifting effect of the expanding Universe. Intrinsically, the galaxy itself is very blue.
(Credit: NASA, ESA, P. Oesch and B. Robertson (University of California, Santa Cruz), and A. Feild (STScI))

We had no known instances of planets orbiting around stars other than the Sun.

The combination of Subaru data (red image) and Hubble data (blue image) reveals the presence of an exoplanet at a distance of 93 Astronomical Units (where 1 A.U. is the Earth-Sun distance) from its parent star. The luminosity of the massive object indicates reflected stellar emission rather than unimpeded direct emission, while the lack of a polarization signal is highly suggestive of a formation scenario other than core accretion. This is one of more than 5000 exoplanets presently known.
(Credit: T. Currie et al., Nature Astronomy, 2022)

We didn’t know whether the Universe was 10 billion or 16 billion years old.

unreachable
The light from any galaxy that was emitted after the start of the hot Big Bang, 13.8 billion years ago, would have reached us by today so long as it’s within about 46.1 billion light-years at present. But the light from the earliest, most distant galaxies will be blocked by intervening matter and redshifted by the expanding Universe. Both represent severe challenges to detection, and pose cautionary tales against us drawing definitive conclusions about their distance without the proper, necessary data.
(Credit: F. Summers, A. Pagan, L. Hustak, G. Bacon, Z. Levay, and L. Frattere (STScI))

We didn’t know whether space was expanding at 50 or 100 km/s/Mpc.

Pantheon+
Although there are many aspects of our cosmos that all data sets agree on, the rate at which the Universe is expanding is not one of them. Based on supernovae data alone, we can infer an expansion rate of ~73 km/s/Mpc, but supernovae do not probe the first ~3 billion years of our cosmic history. If we include data from the cosmic microwave background, itself emitted very close to the Big Bang, there are irreconcilable differences at this moment in time, but only at the <10% level!
(Credit: D. Brout et al./Pantheon+, ApJ submitted, 2022)

We didn’t know whether dark matter was hot, warm, or cold, or how much there was.

The X-ray (pink) and overall matter (blue) maps of various colliding galaxy clusters show a clear separation between normal matter and gravitational effects, some of the strongest evidence for dark matter. The X-rays come in two varieties, soft (lower-energy) and hard (higher-energy), where galaxy collisions can create temperatures exceeding several hundreds of thousands of degrees.
(Credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland; University of Edinburgh, UK), R. Massey (Durham University, UK), T. Kitching (University College London, UK), and A. Taylor and E. Tittley (University of Edinburgh, UK))

We didn’t know about the existence of dark energy or what the Universe’s fate would be.

The impressively huge galaxy cluster MACS J1149.5+223, whose light took over 5 billion years to reach us, is among the largest bound structures in all the Universe. On larger scales, nearby galaxies, groups, and clusters may appear to be associated with it, but are being driven apart from this cluster due to dark energy; superclusters are only apparent structures, and Hubble’s view of the distant Universe helped reveal this property.
(Credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI))

We didn’t even know whether or not black holes were real.

quasar-galaxy hybrid
This tiny sliver of the GOODS-N deep field, imaged with many observatories including Hubble, Spitzer, Chandra, XMM-Newton, Herschel, the VLT and more, contains a seemingly unremarkable red dot. That object, a quasar-galaxy hybrid from just 730 million years after the Big Bang, may be key to unlocking the mystery of galaxy-black hole evolution. Once speculative, the evidence for the physical existence and ubiquity of black holes is now overwhelming.
(Credit: NASA, ESA, G. Illingworth (UCSC), P. Oesch (UCSC, Yale), R. Bouwens (LEI), I. Labbe (LEI), Cosmic Dawn Center/Niels Bohr Institute/University of Copenhagen, Denmark)

After 32 years of Hubble, these questions and more have all been definitively answered.

The visible/near-IR photos from Hubble show a massive star, about 25 times the mass of the Sun, that has winked out of existence, with no supernova or other explanation. Direct collapse is the only reasonable candidate explanation, and is one known way, in addition to supernovae or neutron star mergers, to form a black hole for the first time.
(Credit: NASA/ESA/C. Kochanek (OSU))

The frontiers have been pushed back, and now we seek to answer the follow-up questions.

In this comparison view, the Hubble data is shown in violet, while ALMA data, revealing dust and cold gas (which themselves indicate star-formation potential), is overlaid in orange. Clearly, ALMA is revealing not only features and details that Hubble cannot, but sometimes, it shows the presence of objects that Hubble cannot see at all.
(Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble)

Thank you, Hubble, and may ALMA, the JWST, and more continuously advance our neverending quest for knowledge.

james webb spikes
The very first finely-phased image ever released by NASA’s James Webb Space Telescope shows a single image of a star, complete with six prominent diffraction spikes (and two less-prominent ones), with background stars and galaxies revealed behind it. As remarkable as this image is, it’s likely to be the worst James Webb Space Telescope image you’ll ever see from hereon out.
(Credit: NASA/STScI)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

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