Featured Research

from universities, journals, and other organizations

Pulsating Stars Enable New Precise Determination Of Rotation Of The Milky Way

Date:
September 21, 2008
Source:
ESO
Summary:
New, very precise measurements have shown that the rotation of the Milky Way is simpler than previously thought. A remarkable result from the most successful ESO instrument HARPS, shows that a much debated, apparent "fall" of neighborhood Cepheid stars towards our Sun stems from an intrinsic property of the Cepheids themselves.

Artist's impression of the local neighbourhood of the Sun and its setting within our galaxy, the Milky Way (see insert above). The figure shows the positions of some bright stars (in white) in the sky as well as the eight Cepheids used in the investigation (in blue). After the rotation of the Milky Way had been accounted for (red arrow), it seemed that the Cepheids were all 'falling' towards the Sun (blue arrows; these are not to scale: in reality the blue velocities are typically a factor one hundred smaller than the velocity around the Milky Way). New, very precise measurements with the HARPS instrument have shown that this apparent 'fall' is due to effects within the Cepheids themselves and is not related to the way the Milky Way rotates. The motion indicated by the blue arrows is thus an illusion. The scale of the image is given in light-years (ly).
Credit: ESO

New, very precise measurements have shown that the rotation of the Milky Way is simpler than previously thought. A remarkable result from the most successful ESO instrument HARPS, shows that a much debated, apparent 'fall' of neighbourhood Cepheid stars towards our Sun stems from an intrinsic property of the Cepheids themselves.

The result was obtained by a group of astrophysicists led by Nicolas Nardetto.

Since Henrietta Leavitt's discovery of their unique properties in 1912, the class of bright, pulsating stars known as Cepheids has been used as a distance indicator. Combined with velocity measurements, the properties of Cepheids are also an extremely valuable tool in investigations of how our galaxy, the Milky Way, rotates.

"The motion of Milky Way Cepheids is confusing and has led to disagreement among researchers," says Nardetto. "If the rotation of the Galaxy is taken into account, the Cepheids appear to 'fall' towards the Sun with a mean velocity of about 2 km/s."

A debate has raged for decades as to whether this phenomenon was truly related to the actual motion of the Cepheids and, consequently, to a complicated rotating pattern of our galaxy, or if it was the result of effects within the atmospheres of the Cepheids.

Nardetto and his colleagues observed eight Cepheids with the high precision HARPS spectrograph, attached to the 3.6-m ESO telescope at La Silla, 2400 m up in the mountains of the Chilean Atacama Desert. HARPS, or the High Accuracy Radial Velocity Planetary Searcher, is best known as a very successful planet hunter, but it can also be used to resolve other complicated cases, where its ability to determine radial velocities - the speed with which something is moving towards or away from us - with phenomenally high accuracy is invaluable. "Our observations show that this apparent motion towards us almost certainly stems from an intrinsic property of Cepheids," says Nardetto.

The astronomers found that the deviations in the measured velocity of Cepheids were linked to the chemical elements in the atmospheres of the Cepheids considered. "This result, if generalised to all Cepheids, implies that the rotation of the Milky Way is simpler than previously thought, and is certainly symmetrical about an axis," concludes Nardetto.


Story Source:

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


Journal Reference:

  1. Nardetto, N., Stoekl, A., Bersier, D. & Barnes, T. G. High resolution spectroscopy for Cepheids distance determination. III. A relation between %u03B3-velocities and %u03B3-asymmetries. Astronomy & Astrophysics, (in press)

Cite This Page:

ESO. "Pulsating Stars Enable New Precise Determination Of Rotation Of The Milky Way." ScienceDaily. ScienceDaily, 21 September 2008. <www.sciencedaily.com/releases/2008/09/080919142648.htm>.
ESO. (2008, September 21). Pulsating Stars Enable New Precise Determination Of Rotation Of The Milky Way. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2008/09/080919142648.htm
ESO. "Pulsating Stars Enable New Precise Determination Of Rotation Of The Milky Way." ScienceDaily. www.sciencedaily.com/releases/2008/09/080919142648.htm (accessed April 21, 2014).

Share This



More Space & Time News

Monday, April 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

SpaceX's Dragon Spacecraft Captured by International Space Station

SpaceX's Dragon Spacecraft Captured by International Space Station

Reuters - US Online Video (Apr. 20, 2014) SpaceX's unmanned Dragon spacecraft makes a scheduled Easter Sunday rendezvous with the International Space Station. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Raw: Easter Morning Delivery for Space Station

Raw: Easter Morning Delivery for Space Station

AP (Apr. 20, 2014) Space station astronauts got a special Easter treat: a cargo ship full of supplies. The SpaceX company's cargo ship, Dragon, spent two days chasing the International Space Station following its launch from Cape Canaveral. (April 20) Video provided by AP
Powered by NewsLook.com
Extremely Large Telescope Could Spot Alien Life

Extremely Large Telescope Could Spot Alien Life

Newsy (Apr. 20, 2014) Scientists are preparing to blow up a Chilean mountain to construct the Extremely Large Telescope, which will take detailed pictures of exoplanets. Video provided by Newsy
Powered by NewsLook.com
A Hoax? Cosmetics Company Wants To Brighten The Moon

A Hoax? Cosmetics Company Wants To Brighten The Moon

Newsy (Apr. 19, 2014) FOREO, a Swedish cosmetics company, says it wants to brighten the moon to lower electricity costs. Video provided by Newsy
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:
from the past week

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