Featured Research

from universities, journals, and other organizations

Stream of stars in Andromeda satellite galaxy shows cosmic collision

Date:
February 23, 2014
Source:
University of Copenhagen - Niels Bohr Institute
Summary:
The Andromeda Galaxy is surrounded by a swarm of small satellite galaxies. Researchers have detected a stream of stars in one of the Andromeda Galaxy's outer satellite galaxies, a dwarf galaxy called Andromeda II. This galaxy is very small -- less than one percent of the Milky Way. The movement of the stars tells us that what we are observing is the remnant of a merger between two dwarf galaxies. Mergers between galaxies of such low mass has not been observed before.

The Andromeda Galaxy is a large spiral galaxy like our galaxy, the Milky Way. It is located about 2.3 million light years away and can be seen with the naked eye. The satellite galaxy Andromeda II is located in a distant orbit approximately 600,000 light years from the center of the great Andromeda Galaxy.
Credit: NASA

The Andromeda Galaxy is surrounded by a swarm of small satellite galaxies. Researchers from the Niels Bohr Institute, among others, have detected a stream of stars in one of the Andromeda Galaxy's outer satellite galaxies, a dwarf galaxy called Andromeda II. The movement of the stars tells us that what we are observing is the remnant of a merger between two dwarf galaxies. Mergers between galaxies of such low mass has not been observed before. The results are published in the scientific journal, Nature.

Related Articles


The galaxies in the early universe started off small and the theory of the astronomers is that the baby galaxies gradually grew larger and more massive by constantly colliding with neighbouring galaxies to form new, larger galaxies. Large, massive galaxies constantly attract smaller galaxies due to gravity and they eventually merge together and grow even larger.

But not all of the small galaxies are being 'eaten' by the large galaxies. Some of them remain in an orbit around the large galaxy. The largest galaxy in our cosmic neighborhood is the Andromeda Galaxy, which is about 2.3 million light years away. Like our own galaxy, the Milky Way, Andromeda is a large spiral galaxy.

Swarm of small galaxies

Andromeda is surrounded by a swarm of small galaxies -- astronomers have counted more than 20. They have names like Andromeda I, II, III, IV...etc. Researchers from the Dark Cosmology Centre at the Niels Bohr Institute, among others, have analysed measurements of the stars in the dwarf galaxy Andromeda II and made a surprising discovery.

"Stars in a dwarf galaxy often move around at random, but this is not exactly the case for Andromeda II. In particular we could see that a stream of stars is moving around differently than the rest in a very coherent way. These stars are situated in an almost complete ring and are rotating around the centre of the galaxy," explains astrophysicist Nicola C. Amorisco, Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen.

Cosmic collisions

The dwarf galaxy Andromeda II is very small -- less than one percent of the Milky Way. The rotating stream of stars in the galaxy is entirely made up of old stars and from their properties, researchers can draw conclusions about this dramatic cosmic event.

"What we are seeing is the remains of a collision between two dwarf galaxies, which had a dramatic effect on the dynamics of the remnant," says Nicola C. Amorisco.

He explains that mergers between such small galaxies are expected during the galaxy formation process, but are rare at present times and had hitherto not been seen. Andromeda II is the least massive known example of merging of galaxies so far and illustrates the scale-free character og the formation og galaxies down to the lowest galactic mass scales.


Story Source:

The above story is based on materials provided by University of Copenhagen - Niels Bohr Institute. Note: Materials may be edited for content and length.


Journal Reference:

  1. N. C. Amorisco, N. W. Evans, G. van de Ven. The remnant of a merger between two dwarf galaxies in Andromeda II. Nature, 2014; DOI: 10.1038/nature12995

Cite This Page:

University of Copenhagen - Niels Bohr Institute. "Stream of stars in Andromeda satellite galaxy shows cosmic collision." ScienceDaily. ScienceDaily, 23 February 2014. <www.sciencedaily.com/releases/2014/02/140223131709.htm>.
University of Copenhagen - Niels Bohr Institute. (2014, February 23). Stream of stars in Andromeda satellite galaxy shows cosmic collision. ScienceDaily. Retrieved January 30, 2015 from www.sciencedaily.com/releases/2014/02/140223131709.htm
University of Copenhagen - Niels Bohr Institute. "Stream of stars in Andromeda satellite galaxy shows cosmic collision." ScienceDaily. www.sciencedaily.com/releases/2014/02/140223131709.htm (accessed January 30, 2015).

Share This


More From ScienceDaily



More Space & Time News

Friday, January 30, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA Holds Memorial to Remember Astronauts

NASA Holds Memorial to Remember Astronauts

AP (Jan. 29, 2015) NASA is remembering 17 astronauts who were killed in the line of duty and dozens more who have died since the agency&apos;s beginning. A remembrance ceremony was held Thursday at NASA&apos;s Marshall Space Flight Center in Alabama. (Jan. 29) Video provided by AP
Powered by NewsLook.com
Asteroid's Moon Spotted During Earth Flyby

Asteroid's Moon Spotted During Earth Flyby

Rumble (Jan. 27, 2015) Scientists working with NASA&apos;s Deep Space Network antenna at Goldstone, California discovered an unexpected moon while observing asteroid 2004 BL86 during its recent flyby past Earth. Credit to &apos;NASA JPL&apos;. Video provided by Rumble
Powered by NewsLook.com
Water Fleas Prepare for Space Voyage

Water Fleas Prepare for Space Voyage

Reuters - Innovations Video Online (Jan. 26, 2015) Scientists are preparing a group of water fleas for a unique voyage into space. The aquatic crustaceans, known as Daphnia, can be used as a miniature model for biomedical research, and their reproductive and swimming behaviour will be tested for signs of stress while on board the International Space Station. Jim Drury went to meet the team. Video provided by Reuters
Powered by NewsLook.com
Mars Rover Opportunity Celebrates 11-Year Anniversary

Mars Rover Opportunity Celebrates 11-Year Anniversary

Rumble (Jan. 26, 2015) Eleven years ago NASA&apos;s Opportunity rover touched down on Mars for what was only supposed to be a 90-day mission. Since then it has traveled 25.9 miles (41.7 kilometers), further than any other off-Earth surface vehicle has ever driven. Credit to &apos;NASA&apos;. Video provided by Rumble
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins