Skip to content
Vatican Observatory
  • About
    • Overview
    • Team
    • FAQ
  • Telescopes
    • Overview
    • Telescope Images
  • Tours
    • Castel Gandolfo
    • U.S.
  • 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
  • Shop
  • Calendar
    • View our Event Calendar
  • Donate
    • Donate Now
    • Smart Ways to Give
    • Sacred Space Astronomy
      • View Content
    • Bequests / Trusts
    • The Foundation
      • Newsletters
      • Annual Reports
  • Press
    • VO in the News
    • Press Kit
  • Specola Vaticana
  • Contact
    • Contact
  • About
    • Overview
    • Team
    • FAQ
  • Telescopes
    • Overview
    • Telescope Images
  • Tours
    • Castel Gandolfo
    • U.S.
  • 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
  • Shop
  • Calendar
    • View our Event Calendar
  • Donate
    • Donate Now
    • Smart Ways to Give
    • Sacred Space Astronomy
      • View Content
    • Bequests / Trusts
    • The Foundation
      • Newsletters
      • Annual Reports
  • Press
    • VO in the News
    • Press Kit
  • Specola Vaticana
  • Contact
    • Contact

Andromeda Galaxy – Sister to the Milky Way

By Dr. Brenda Frye  |  26 Apr 2015

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

One of the tasks I get to do only rarely these days is to show a student a picture of the Andromeda Galaxy. Andromeda is the closest galaxy to us as seen from the northern hemisphere.

Students have a tendency to skip over Andromeda and ask to see Saturn again, until it is pointed out that this small, unimpressive gray smudge on the sky which we also call Messier 31 shines with the glow of 100 billion stars, and that the light we see traveled 2.2 million light years to reach us.

Andromeda is the closest approximation to our own Milky Way that we will every have, and we will see this sister galaxy to the Milky Way only for a limited time.

Andromeda is a large spiral galaxy with spiral arms that is roughly the same size as the Milky Way. The stars are forming in both galaxies at a good pace – not too fast and not too slow. And like the Milky Way, we think the center of Andromeda also is primarily composed of a material we cannot see called dark matter.

Both Andromeda and the Milky Way are heavyweights situated in the neighborhood of a mid-sized town of other galaxies called the Local Group. They are massive and pulled to each other by the gravitational force. In fact they are on a direct collision course.

That’s right – in another 5 billion years there will be a large crash. To trace what happens in this galaxy-galaxy collision, one will want to follow the most massive components. In both galaxies the dark matter dominates the mass and forms their backbones, so to speak.

Interestingly, the dark matter may be relatively unaffected by a head-on collision, or at least the dark matter is not expected to produce gigantic explosions. This is because dark matter appears to interact only weakly with itself and with the ordinary matter that you and I are made of. It is as if two football players set on a direct hit instead pass straight through each other.

The most dramatic explosions will take place with the gas. Here enormous amounts of hydrogen gas will be shock-heated and probably induced to form stars (think of super giant blimps crashing into each other at ultra-high speeds)! The end state will be a single larger galaxy.

The collision will be mind-bogglingly big, that’s true, and fortunately for us Earth will be just a tiny speck of dust in this big picture that we may come out of the ‘merger’ entirely unaffected. We will in fact have more to fear from the fact that in a bit less than 5 billion years our Sun will run out of fuel and start to shut down!

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

Corkscrew Prom

By Deirdre Kelleghan  |  21 May 2025  |  Sacred Space Astronomy

From the Vatican Observatory Faith and Science pages (Younger Readers) — Gregor Mendel: The Friar Who Grew Peas

By Faith and Science  |  21 May 2025  |  Sacred Space Astronomy

Nuns Helped Map Close To Half A Million Stars In The Early 20th Century After The Vatican Recruited Them

Chip Chick  |  20 May 2025  |  Press

Visit of Br. Guy Consolmagno S.J.

Pluscarden Abbey  |  19 May 2025  |  Press

Archives

      • 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
      • 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
  • Tours
  • Latest
  • Podcast
  • Education
  • Shop
  • Calendar
  • Donate
  • Press
  • Specola Vaticana
  • Contact
Privacy Policy  |   Cookie Policy  |   Disclosure Statement  |   This website is supported by the Vatican Observatory Foundation

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