This giant spiral disk of stars, dust and gas is 170,000 light-years across, or nearly twice the diameter of our Milky Way galaxy. (Credit for Hubble Image: NASA, ESA, K. Kuntz (JHU), F. Bresolin (University of Hawaii), J. Trauger (Jet Propulsion Lab), J. Mould (NOAO), Y.-H. Chu (University of Illinois, Urbana), and STScI)

Galaxies are gravitationally bound collections of stars, planets, gas, dust, dark matter and other objects, including black holes. They represent the standard "building blocks" of large-scale structure in the universe. Galaxies group hierarchically into clusters of galaxies and superclusters. These groupings in turn comprise larger structures of long, luminous filaments and sheets of galaxies, separated by gaping voids containing few galaxies. In general, galaxies come in three broad shapes and sizes: giant ellipticals, spirals, and small dwarfs. Astrophysicists study phenomena such as the mergers of galaxies, star formation rates and the influences from supernovae and black holes to understand the development of these and other galactic types over cosmic history. Cosmologists, meanwhile, use the evolution of the large-scale structures composed of galaxies to probe how the universe has changed since the Big Bang 13.8 billion years ago. A topic of major interest is the distribution of dark matter, which corresponds to the location of superclusters and filaments. Another is the effect of dark energy, which is accelerating the universe's expansion as evidenced by the speed of distant galaxies receding from our own galaxy, the Milky Way.

Will a New Discovery Fast-track Our Understanding of the Origins of Galaxies and Gargantuan Black Holes?

Mar 07, 2017

The Kavli Foundation spoke with three astrophysicists—Roberto Maiolino, Linhua Jiang and Marta Volonteri—about how a record haul of new, ultra-distant quasars will transform what we know about the early universe.

Why Dead Galaxies ‘Rest in Peace,’ Never to Form Stars Again

Sep 15, 2016
Red geyser galaxy

Scientists are discovering how powerful eruptions from monster black holes ensure dead galaxies cannot resurrect and make new stars. In a roundtable discussion, astrophysicists Edmond Cheung, Kevin Bundy and Christy Tremonti explain.

Galactic 'Gold Mine' Explains the Origin of Nature's Heaviest Elements

May 10, 2016
Neutron star collision

Three astrophysicists—Anna Frebel, Alexander Ji and Enrico Ramirez-Ruiz—discuss the answer to a 60-year-old cosmic mystery: the origin of some of the most precious elements in the universe.

Crowdsourcing the Universe: How Citizen Scientists are Driving Discovery

Jan 13, 2016
Gravitational lenses

Legions of volunteer, 'citizen scientists' are training their eyes on the sky and sharing in the thrill of discovery. In this Kavli roundtable, Citizen science leader Chris Lintott joins Anupreeta More and Aprajita Verma of the Space Warps project to discuss the exciting endeavor.

Spotlight Live: Searching for Alien Life wth a "Super-Hubble" Space Telescope (Transcript)

Nov 05, 2015
Milky Way

On October 6, The Kavli Foundation hosted a Google+ Hangout to learn more about proposed High Definition Space Telescope, a kind of "Super Hubble" that could launch in the 2030s. We spoke with two of the proponents: Julianne Dalcanton of the University of Washington and Marc Postman of the Space Telescope Science Institute. This is a transcript of that discussion.

Spotlight Live: Searching for Alien Life with a "Super-Hubble" Space Telescope

Sep 17, 2015
Schematic of HDST

On October 6, The Kavli Foundation hosted a Google+ Hangout to learn more about proposed High Definition Space Telescope, a kind of "Super Hubble" that could launch in the 2030s. We spoke to Julianne Dalcanton of the University of Washington, who co-chaired the committee that put forward the proposal, as well as committee member Marc Postman of the Space Telescope Science Institute.

Dwarf Galaxies Loom Large in the Quest for Dark Matter

Jun 21, 2015
An artist's impression of the Fermi Gamma-Ray Space Telescope. (Credit: NASA/General Dynamics)

Three astrophysicists discuss the ongoing search for dark matter and how dwarf galaxies can help us understand the evolution of our universe.



Delving Into the 'Dark Universe' with the Large Synoptic Survey Telescope

May 27, 2015
An illustration of the Large Synoptic Survey Telescope (LSST)

Two astrophysicists and a theoretical physicist discuss how the Large Synoptic Survey Telescope will probe the nature of dark matter and dark energy by taking an unprecedentedly enormous scan of the sky.

Bubbles From the Center of Our Galaxy: A Key to Understanding Dark Matter and the Milky Way's Past?

Jan 26, 2015

Fresh from the January Rossi Prize Lecture, the scientists who discovered the “Fermi bubbles,” two of the largest structures in the Milky Way, say the bubbles can tell of our galaxy’s past – and even help find dark matter.

Building the Universe Pixel by Pixel

Aug 20, 2014

Three 'mapmakers' of the universe – Ralf Kaehler, Stuart Levy and Dylan Nelson – discuss how their dramatically intricate 3-D universes can tell important stories about the cosmos.


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