ESA title
Galaxy forming stars
Science & Exploration

Herschel paints new story of galaxy evolution

13/09/2011 4383 views 7 likes
ESA / Science & Exploration / Space Science / Herschel

ESA's Herschel infrared space observatory has discovered that galaxies do not need to collide with each other to drive vigorous star birth. The finding overturns this long-held assumption and paints a more stately picture of how galaxies evolve.

The conclusion is based on Herschel's observations of two patches of sky, each about a third of the size of the full Moon.

It's like looking through a keyhole across the Universe – Herschel has seen more than a thousand galaxies at a variety of distances from the Earth, spanning 80% of the age of the cosmos.

These observations are unique because Herschel can study a wide range of infrared light and reveal a more complete picture of star birth than ever seen before.

It has been known for some years that the rate of star formation peaked in the early Universe, about 10 billion years ago. Back then, some galaxies were forming stars ten or even a hundred times more vigorously than is happening in our Galaxy today.

Herschel's view of GOODS-North
Herschel's view of GOODS-North

In the nearby, present-day Universe, such high birth rates are very rare and always seem to be triggered by galaxies colliding with each other. So, astronomers had assumed that this was true throughout history.

Herschel now shows that this is not the case by looking at galaxies that are very far away and thus seen as they were billions of years ago.

David Elbaz, CEA Saclay, France, and collaborators have analysed the Herschel data and find that galaxy collisions played only a minor role in triggering star births in the past, even though some young galaxies were creating stars at furious rates.

By comparing the amount of infrared light released at different wavelengths by these galaxies, the team has shown that the star birth rate depends on the quantity of gas they contain, not whether they are colliding.

Gas is the raw building material for stars and this work reveals a simple link: the more gas a galaxy contains, the more stars are born.

Herschel's view of GOODS-South
Herschel's view of GOODS-South

"It's only in those galaxies that do not already have a lot of gas that collisions are needed to provide the gas and trigger high rates of star formation", says Dr Elbaz.

This applies to today's galaxies because, after forming stars for more than 10 billion years, they have used up most of their gaseous raw material.

The research paints a much more stately picture of star births than before, with most galaxies sitting in space, growing slowly and naturally from the gas they attract from their surroundings.

"Herschel was conceived to study the history of star formation across cosmic time", says Göran Pilbratt, ESA Herschel Project Scientist.

"These new observations now change our perception of the history of the Universe."

Contact for further information

Related Links

Science & Exploration

Notes to editors

06/05/2010 1025 views 0 likes
Read
Science & Exploration

Other Herschel First Science Stories

01/01/1970 1564 views
Open item
Fomalhaut and dust disc
Science & Exploration

Herschel spots comet massacre around nearby star

11/04/2012 4449 views 6 likes
Read
Baby stars in Orion Nebula
Science & Exploration

Fledgling stars flicker in the heart of Orion

29/02/2012 3990 views 4 likes
Read
Stunning new Herschel and XMM-Newton image of the Eagle Nebula
Science & Exploration

A New View of an Icon

17/01/2012 14226 views 11 likes
Read
The Herschel and Planck AAAF Grand Prix 2010 award ceremony
Science & Exploration

Herschel and Planck win the French Grand Prix

10/06/2010 1719 views 2 likes
Read
NGC 1999: Truly a hole in space.
Science & Exploration

Herschel finds a hole in space

11/05/2010 10657 views 32 likes
Read
The Galactic bubble RCW 120
Science & Exploration

Herschel reveals the hidden side of star birth

06/05/2010 4696 views 6 likes
Read
The CB244 dark globule
Science & Exploration

Herschel takes the temperature of an interstellar cloud

06/05/2010 3525 views 2 likes
Read
Herschel and Rosette Nebula
Science & Exploration

Tracing the Milky Way’s hidden reservoirs of gas

06/05/2010 1666 views 4 likes
Read
Previously unseen galaxies revealed to ESA's Herschel
Science & Exploration

Herschel resolves the cosmic infrared fog

06/05/2010 1952 views 0 likes
Read
The Rosette molecular cloud, seen by Herschel
Science & Exploration

Baby stars in the Rosette cloud

12/04/2010 7086 views 14 likes
Read
Inside the dark heart of the Eagle
Science & Exploration

Inside the dark heart of the Eagle

16/12/2009 4204 views 3 likes
Read
Reservoir of cold gas in the constellation of the Southern Cross
Science & Exploration

Herschel views deep-space pearls on a cosmic string

02/10/2009 3951 views 5 likes
Read
Herschel and Planck
Science & Exploration

Herschel and Planck pass in-orbit 'exam'

24/07/2009 1620 views 1 likes
Read
Science & Exploration

Herschel images promise bright future

10/07/2009 3315 views 0 likes
Read
Herschel's test view of M51
Science & Exploration

Herschel’s daring test: a glimpse of things to come

19/06/2009 5283 views 8 likes
Read
Artist concept of the Herschel spacecraft
Science & Exploration

Herschel cryocover is open

15/06/2009 1735 views 1 likes
Read
ISO: Infrared Space Observatory
Agency

Observations: Seeing in infrared wavelengths

6396 views 19 likes
Read
Cold comfort for newborn stars - ISO unmasks the icy veil around the Eagle's fiery heart
Science & Exploration

Why infrared astronomy is a hot topic

11/09/2003 10645 views 35 likes
Read
Location of Lagrangian point (L2)
Science & Exploration

L2, the second Lagrangian Point

196236 views 1504 likes
Read