Featured Research

from universities, journals, and other organizations

Serious blow to dark matter theories? New study finds mysterious lack of dark matter in Sun's neighborhood

Date:
April 18, 2012
Source:
European Southern Observatory - ESO
Summary:
The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighborhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

This annotated artist’s impression shows the Milky Way galaxy. The blue halo of material surrounding the galaxy indicates the expected distribution of the mysterious dark matter. New measurements based on the movements of stars show that the amount of dark matter in this region around the Sun is far smaller than predicted and have indicated that there is no significant dark matter at all in our neighbourhood. The blue sphere centred on the Sun’s position shows the approximate size of the newly surveyed volume, but not its precise shape.
Credit: ESO/L. Calçada

The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

A team using the MPG/ESO 2.2-metre telescope at the European Southern Observatory's La Silla Observatory, along with other telescopes, has mapped the motions of more than 400 stars up to 13,000 light-years from the Sun. From this new data they have calculated the mass of material in the vicinity of the Sun, in a volume four times larger than ever considered before.

"The amount of mass that we derive matches very well with what we see -- stars, dust and gas -- in the region around the Sun," says team leader Christian Moni Bidin (Departamento de Astronomía, Universidad de Concepción, Chile). "But this leaves no room for the extra material -- dark matter -- that we were expecting. Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!"

Dark matter is a mysterious substance that cannot be seen, but shows itself by its gravitational attraction for the material around it. This extra ingredient in the cosmos was originally suggested to explain why the outer parts of galaxies, including our own Milky Way, rotated so quickly, but dark matter now also forms an essential component of theories of how galaxies formed and evolved.

Today it is widely accepted that this dark component constitutes about the 80% of the mass in the Universe [1], despite the fact that it has resisted all attempts to clarify its nature, which remains obscure. All attempts so far to detect dark matter in laboratories on Earth have failed.

By very carefully measuring the motions of many stars, particularly those away from the plane of the Milky Way, the team could work backwards to deduce how much matter is present [2]. The motions are a result of the mutual gravitational attraction of all the material, whether normal matter such as stars, or dark matter.

Astronomers' existing models of how galaxies form and rotate suggest that the Milky Way is surrounded by a halo of dark matter. They are not able to precisely predict what shape this halo takes, but they do expect to find significant amounts in the region around the Sun. But only very unlikely shapes for the dark matter halo -- such as a highly elongated form -- can explain the lack of dark matter uncovered in the new study [3].

The new results also mean that attempts to detect dark matter on Earth by trying to spot the rare interactions between dark matter particles and "normal" matter are unlikely to be successful.

"Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for. So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found. Our results contradict the currently accepted models. The mystery of dark matter has just become even more mysterious. Future surveys, such as the ESA Gaia mission, will be crucial to move beyond this point." concludes Christian Moni Bidin.

Notes

[1] According to current theories dark matter is estimated to constitute 83% of the matter in the Universe with the remaining 17% in the form of normal matter. A much larger amount of dark energy also seems present in the Universe, but is not expected to affect the motions of the stars within the Milky Way.

[2] The observations were made using the FEROS spectrograph on the MPG/ESO 2.2-metre telescope, the Coralie instrument on the Swiss 1.2-metre Leonhard Euler Telescope, the MIKE instrument on the Magellan II Telescope and the Echelle Spectrograph on the Irene du Pont Telescope. The first two telescopes are located at ESO's La Silla Observatory and the latter two telescopes are located at the Las Campanas Observatory, both in Chile. A total of more than 400 red giant stars at widely differing heights above the plane of the galaxy in the direction towards the south galactic pole were included in this work.

[3] Theories predict that the average amount of dark matter in the Sun's part of the galaxy should be in the range 0.4-1.0 kilograms of dark matter in a volume the size of Earth. The new measurements find 0.00±0.07 kilograms of dark matter in a volume the size of Earth.

More information

This research was presented in a paper, "Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood," by Moni-Bidin et al. to appear in The Astrophysical Journal.

The team is composed of C. Moni Bidin (Departamento de Astronomía, Universidad de Concepción, Chile), G. Carraro (European Southern Observatory, Santiago, Chile), R. A. Méndez (Departamento de Astronomía, Universidad de Chile, Santiago, Chile) and R. Smith (Departamento de Astronomía, Universidad de Concepción, Chile).


Story Source:

The above story is based on materials provided by European Southern Observatory - ESO. Note: Materials may be edited for content and length.


Cite This Page:

European Southern Observatory - ESO. "Serious blow to dark matter theories? New study finds mysterious lack of dark matter in Sun's neighborhood." ScienceDaily. ScienceDaily, 18 April 2012. <www.sciencedaily.com/releases/2012/04/120418111923.htm>.
European Southern Observatory - ESO. (2012, April 18). Serious blow to dark matter theories? New study finds mysterious lack of dark matter in Sun's neighborhood. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2012/04/120418111923.htm
European Southern Observatory - ESO. "Serious blow to dark matter theories? New study finds mysterious lack of dark matter in Sun's neighborhood." ScienceDaily. www.sciencedaily.com/releases/2012/04/120418111923.htm (accessed October 22, 2014).

Share This



More Space & Time News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Russian Cosmonauts Kick Off Final Spacewalk of 2014

Russian Cosmonauts Kick Off Final Spacewalk of 2014

Reuters - US Online Video (Oct. 22, 2014) — Russian cosmonauts Maxim Suraev and Alexander Samokutyaev step outside the International Space Station to perform work on the exterior of the station's Russian module. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
Comet Siding Spring Grazes Mars' Atmosphere

Comet Siding Spring Grazes Mars' Atmosphere

Newsy (Oct. 19, 2014) — A comet from the farthest reaches of the solar system passed extremely close to Mars this weekend, giving astronomers a rare opportunity to study it. Video provided by Newsy
Powered by NewsLook.com
Latin America Launches Communications Satellite

Latin America Launches Communications Satellite

AFP (Oct. 17, 2014) — Argentina launches a home-built satellite, a first for Latin America. It will ride a French-made Ariane 5 rocket into orbit, and will provide cell phone, digital TV, Internet and data services to the lower half of South America. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
This Week @ NASA, October 17, 2014

This Week @ NASA, October 17, 2014

NASA (Oct. 17, 2014) — Power spacewalk, MAVEN’s “First Light”, Hubble finds extremely distant galaxy and more... Video provided by NASA
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