Skip to Content
Uncategorized

Bars in Spiral Galaxies May Disappear and Reform in Ongoing Cycle

A new study of normal and barred spiral galaxies suggests they may be the same objects in different stages of a repeating cycle.

The way galaxies form and evolve is largely a mystery to astronomers. A particular focus of much head scratching is the bar that appears in many spiral galaxies. How does this form and why only in some spiral galaxies?

One thing that astronomers have studied in great detail is the colour of galaxies. In 1936, Edwin Hubble suggested that galaxies may evolve from elliptical galaxies to spiral ones. Astronomers have since found that galaxies further down this sequence tend to be bluer.

But astronomers also think that the bars at the centre of galaxies must influence colour too, since stars should form in the gas that these bars redistribute in the galaxy which in turn influences the colour of the galaxy.

So a reasonable question to ask is this: what is the difference in colour between spiral galaxies in the same Hubble stage that do and don’t have bars?

Today, Sidney van den Bergh at the Herzberg Institute of Astrophysics in Australia says that nobody has bothered to ask this question, strange though it may seem. So he sets out to do it himself.

He studied 532 barred and spiral galaxies from a database called A Revised Shapley-Ames Catalog of Bright Galaxies published in 1981.

His results indicate that “normal and barred galaxies have indistinguishable colour distributions”. So spiral galaxies at the same Hubble stage are the same colour regardless of whether they have bars or not. In fact their colour is also independent of whether they have other ring-like features, says van den Bergh.

That leads him to a startling conclusion. “Perhaps the apparent independence of the intrinsic colours of spirals from the presence (or absence) of bars hints at the possibility that some bars could be ephemeral structures,” he says, pointing out that it may well be easy for a bar to reform after it has faded away.

So the picture he’s driving at is that in some spiral galaxies, bars form, decay and reform in a cycle. Which means that many of the galaxies that don’t have a bar now may have had one in the recent past and will have one again in the near future. That includes our own galaxy.

That’s an interesting idea but one that will be hard to check. Simulating the shape and evolution of galaxies is notoriously hard because of the complex chemical, magnetic and gravitational interactions that go on.

That’s not to say it isn’t worth a try. If you happen to have a little computing power to spare, why not give it a shot.

Ref: arxiv.org/abs/1104.0698: How Different Are Normal And Barred Spirals?

You can now follow The Physics arXiv Blog on Twitter

Deep Dive

Uncategorized

Five poems about the mind

DREAM VENDING MACHINE I feed it coins and watch the spring coil back,the clunk of a vacuum-packed, foil-wrappeddream dropping into the tray. It dispenses all kinds of dreams—bad dreams, good dreams,short nightmares to stave off worse ones, recurring dreams with a teacake marshmallow center.Hardboiled caramel dreams to tuck in your cheek,a bag of orange dreams…

Work reinvented: Tech will drive the office evolution

As organizations navigate a new world of hybrid work, tech innovation will be crucial for employee connection and collaboration.

lucid dreaming concept
lucid dreaming concept

I taught myself to lucid dream. You can too.

We still don’t know much about the experience of being aware that you’re dreaming—but a few researchers think it could help us find out more about how the brain works.

panpsychism concept
panpsychism concept

Is everything in the world a little bit conscious?

The idea that consciousness is widespread is attractive to many for intellectual and, perhaps, also emotional
reasons. But can it be tested? Surprisingly, perhaps it can.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.