Hubble Frontier Field Abell 2744
Image credits: Hubble/NASA/STScI
Image credits: Hubble/NASA/STScI
NSN Members joined us for a special telecon celebrating 25 years of the Hubble Space Telescope and the incredible contributions it has made to our understanding of our Universe, with a focus on its famous "Deep Field" images.
Slides, audio, and transcript are now available on our resource page .
Post-Talk Q&A Bonus with Dr. Lawton!
Q: Will the field-of-view of the JWST deep-fields be comparable to the Hubble deep-field field-of-views?
A: JWST will investigate the Deep Universe with two instruments - the Near Infrared Camera (NIRCam) and the Near-Infrared Imager and Slitless Spectrograph (NIRISS). The first instrument will take deep imaging, while the second instrument will acquire spectra of galaxies to help confirm their distances and make detailed measurements of galaxy chemical evolution. The field-of-view of NIRCam, which is getting the imaging of the deep fields, is nearly identical to the field-of-view of Hubble's WFC3 images (in the talk, this matches the field-of-view of the Hubble Ultra Deep Fields from 2009-2012 and the eXtreme Deep Field).
More info on NIRCam is here:
More info on NIRISS is here:
More general info on JWST are here:
Q: Is it really that all galaxies formed in the early universe, or are there galaxies still forming today?
A: I am not sure I was clear on the answer to this - and it is a complicated picture. All galaxies have been undergoing some evolution since the early universe, but some galaxies have been undergoing more changes than others. Galaxies that live in dense galaxy clusters exhibit extreme changes due to severe gravitational interactions with other galaxies and the gas that exists in the intercluster medium. Spiral galaxies that fall into massive galaxy clusters tend to merge with other galaxies after some time - their stars, gas, and dust either are thrown out of the galaxies all-together or exist in the new larger merged galaxy. We think all of the large elliptical galaxies we see in the present-day universe exist due to these mergers - spirals cannot keep their shapes after undergoing major mergers.
However, Spirals like the Milky Way that are not in densely populated regions of the universe can build up over time by accreting gas and small galaxies, in what are called minor mergers. We have direct evidence that the Milky Way is currently gobbling up several small (dwarf) galaxies. These smaller dwarf galaxies are typically irregular in shape (due to the gravitational interactions with other galaxies) and have lower metallicities.
The variety of galaxies we see in the present-day universe is a consequence of the histories of those galaxies. We see many more spirals and large ellipticals in the present-day universe than in the past. This is due to galaxies building up over time and accumulating more matter in minor or major mergers. We see that most galaxies in the early universe appear irregular and small. We do see some irregular and small galaxies in the present-day universe, but these are expected to be a bit different than the first galaxies in the universe. The present-day dwarf galaxies have not just been sitting there for 13 billion years doing nothing. Some have experienced a small amount of star formation - making them slightly more chemically evolved. They also can accrete gas from the intergalactic medium that originated from larger galaxies and are chemically enriched.
It is this story of galaxy evolution we are trying to track. How did the large spirals and ellipticals come do dominate the present-day universe? How have the dwarf galaxies in the present-day universe evolved?
I left this out, but one of the biggest mysteries of galaxy evolution is what roles did the supermassive black holes in galaxy centers play in galaxy evolution? We do know that supermassive black holes can regulate star formation in galaxies - when they feast on gas and dust they "turn on" and emit large bipolar jets that push material out of a galaxy and quench star formation. We find supermassive black holes in the centers of nearly every galaxy. How did they get so massive? Were they the seeds around which galaxies formed, or did galaxy formation cause supermassive black hole formation? These are all questions the James Webb Space Telescope is primed to answer.
Hubble’s Views of the Deep Universe
For nearly two decades, the Hubble Space Telescope has pioneered the exploration of the distant universe with images known as the deep fields. The deep fields have given astronomers unprecedented access to understanding how galaxies form and evolve over the cosmic history of our universe, from shortly after the Big Bang to today. For this Hubble 25th anniversary talk, I will offer a retrospective view of Hubble’s contributions to the exploration of the deep universe, and offer some fresh glimpses of what Hubble is currently doing to further our understanding of the distant universe. I will also highlight some of Hubble’s iconic imagery released this anniversary year. I will end with information on how to learn more and resources for the Night Sky Network community.
About our Speaker
Brandon Lawton is an astronomer in the Office of Public Outreach at the Space Telescope Science Institute (STScI) – the science operations center for the Hubble Space Telescope and the future James Webb Space Telescope. He got his PhD in astronomy at New Mexico State University in 2008, followed by a postdoctoral position at STScI where he used Spitzer Space Telescope data to explore star formation in our neighboring galaxies, the Magellanic Clouds. Dr. Lawton has been a member of the Office of Public Outreach since 2011 where he works with the Hubble and Webb education and outreach teams, as well as with the broader NASA education and public outreach community, to deliver accurate cutting-edge science content to students, educators, and the general public.
The NASA Night Sky Network is managed by the Astronomical Society of the Pacific.
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