Skip to content
Vatican Observatory
  • About
    • Overview
    • Team
    • FAQ
  • Telescopes
    • Overview
    • Telescope Images
  • Latest
    • Overview
    • Resources
    • Press
    • Audio
    • Video
    • Research
    • Authors
      • FAQs
    • Newsletter
    • Tucson Meteor Cameras
  • Podcast
  • Education
    • Overview
    • Resource Center
    • Image Gallery
    • Summer School
    • Books
    • Software
    • Additional Resources
    • ACME
    • Ambassadors
  • Shop
  • Calendar
  • Support
    • Overview
    • Donate Now
    • Smart Ways to Give
    • Sacred Space Astronomy
      • View Content
    • Fr. Coyne Fundraiser
    • Bequests / Trusts
    • The Foundation
      • Newsletters
      • Annual Reports
  • Press
  • Specola Vaticana
  • Contact
    • Contact
  • About
    • Overview
    • Team
    • FAQ
  • Telescopes
    • Overview
    • Telescope Images
  • Latest
    • Overview
    • Resources
    • Press
    • Audio
    • Video
    • Research
    • Authors
      • FAQs
    • Newsletter
    • Tucson Meteor Cameras
  • Podcast
  • Education
    • Overview
    • Resource Center
    • Image Gallery
    • Summer School
    • Books
    • Software
    • Additional Resources
    • ACME
    • Ambassadors
  • Shop
  • Calendar
  • Support
    • Overview
    • Donate Now
    • Smart Ways to Give
    • Sacred Space Astronomy
      • View Content
    • Fr. Coyne Fundraiser
    • Bequests / Trusts
    • The Foundation
      • Newsletters
      • Annual Reports
  • Press
  • Specola Vaticana
  • Contact
    • Contact

The Humble Stuff between the Galaxies

By Dr. Brenda Frye  |  14 Aug 2016

Share:
  • Share on Facebook
  • Share on Twitter
  • Share on LinkedIn
  • Share via Email

We normally study galaxies by looking directly at them. We admire the brilliant arms in spiral galaxies like the Milky Way, the giant football-shaped elliptical galaxies, or even the powerful jets emanating from galaxies with supermassive black holes at their centers, the so-called Active Galactic Nuclei (AGN).

As dramatic as such images are, much can be gained also by looking at the impact of these spectacular light-producing objects on the material that sits between the galaxies. We know that hydrogen exists in large amounts in stars and in the galaxies that house the stars. Hydrogen also is the main material found in between the galaxies.

Hydrogen, which is made up of one proton and one electron, has a property that it is opaque to UV radiation. A UV photon of light incident on a hydrogen atom will be absorbed. An effect of this absorption is that the electron will be freed or ‘ionized.’ This ionization leaves a signature in the light we receive at our telescopes in the form of a dark band to mark the region from which the electron was removed.

When we look deep into space extending back to the first one billion years after the Big Bang, we see that the UV light from galaxies and AGN has ionized the intergalactic hydrogen. There are so many overlapping dark bands that it is obvious that hydrogen everywhere is being ionized. By contrast, when we look at galaxies near to us we see far less evidence for these dark bands, which in this case we take as an indication that this material, which should be opaque to UV light, is not doing its job because the atoms are already ionized.

Our best interpretation is that the first galaxies to form in the universe emitted sufficient amounts of UV radiation to escape their own galaxies and to ionize hydrogen atoms in intergalactic space. After a continual bombardment of this intergalactic hydrogen for hundreds of millions of years, all of the hydrogen between the stars eventually became ionized.

Upon reaching this time in cosmic history which we call the epoch of reionization, the regions between the stars remained completely ionized continuing on to this day. There are many uses for this humble approach to study galaxies. For example, we hope to use this technique to help us ‘age-date’ when the first stars actually did form, a primary goal of the upcoming James Webb Space Telescope satellite (launch in 2018).

Share:
  • Share on Facebook
  • Share on Twitter
  • Share on LinkedIn
  • Share via Email

Sacred Space Astronomy

The Vatican Observatory’s official digital community and online magazine.

Become a Member

Recent Posts

Science, Baptists and the Underground Railroad

By Mr. Christopher Graney  |  1 Apr 2023  |  Sacred Space Astronomy

Venus Has More Than 85,000 Individual Volcanic Landforms!

By Robert Trembley  |  30 Mar 2023  |  Sacred Space Astronomy

ⓜ Full Moon-th Meetup: 6 April, 2023

By Robert Trembley  |  29 Mar 2023  |  Sacred Space Astronomy

Centuries of Stargazing Leave Jesuit Names Written in the Heavens

New York Times  |  29 Mar 2023  |  Press

Archives

      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • August
      • June
      • March
      • January
      • November
      • October
      • December
      • November
      • April
      • May
      • January
      • December
      • September
      • May
      • March
      • December
      • November
      • February

More Posts by
Dr. Brenda Frye

A Gift to Us?

By Dr. Brenda Frye  |  22 Aug 2020

Getting to Know a Neutron Star: How Heavy Can They Be?

By Dr. Brenda Frye  |  9 Jul 2020

The Flying Cell Phone to Alpha Centauri: Part Two

By Dr. Brenda Frye  |  21 Jun 2020

The Flying Cell Phone to Alpha Centauri: Part One

By Dr. Brenda Frye  |  28 May 2020

No Wine Before Its Time

By Dr. Brenda Frye  |  3 Jul 2018

Counting Exercise

By Dr. Brenda Frye  |  26 Jun 2018

View More

Newsletter

Upcoming astronomical events, scientific breakthroughs, philosophical reflections… just a few reasons to subscribe to our newsletter!

Vatican Observatory
  • About
  • Telescopes
  • Latest
  • Podcast
  • Education
  • Shop
  • Calendar
  • Support
  • Press
  • Specola Vaticana
  • Contact
Privacy Policy  |   Cookie Policy  |   Disclosure Statement

Podcast:

  • Apple Podcasts Listen onApple Podcasts
  • Spotify Listen onSpotify
  • Google Podcasts Listen onGoogle Podcasts
  • Stitcher Listen onStitcher
  • Amazon Alexa Listen onAmazon Alexa
  • TuneIn Listen onTuneIn
Made by Longbeard