'Standard candles' illuminate the far side of the Milky Way

May 14, 2014
This artist's impression of the Milky Way Galaxy seen from outside shows the Sun (large yellow circle) and some of the well studied nearby Cepheids (pale blue circles). The pink region depicts the hydrogen gas in the flared outer parts of the Milky Way together with the new Cepheids discussed by Feast and colleagues (dark blue circle). Credit: : R. M. Catchpole (IoA Cambridge) and NASA/JPL-Caltech

South African astronomers have discovered the very first known stars in the flared disk of our Milky Way Galaxy. These stars are situated on the far side of our Galaxy, 80 thousand light years from the Earth and beyond the Galactic Centre.

The discovery is important because stars like these will allow astronomers to test theoretical ideas about how , like the Milky Way in which we live, formed. In particular these stars, which are close to the effective edge of the Milky Way, will help astronomers trace the distribution of the very mysterious . Dark matter is known to be an important component of all galaxies, but its nature and distribution remain elusive.

The five stars involved in this discovery are very special ones, known as Cepheid variables, whose brightness changes regularly on a cycle time of a few days. These Cepheid variables have characteristics that allow their distances to be measured accurately. A team of astronomers led by Prof. Michael Feast used observations made with the Southern African Large Telescope (SALT) and the Infrared Survey Facility (IRSF), both at the South African Astronomical Observatory's (SAAO) site at Sutherland in the Northern Cape, to determine the distances of these stars and hence their locations within our Galaxy.

The majority of stars in our Galaxy, including our own sun, are distributed in a flat disk (see illustration). Early in the 21st century radio astronomers discovered that hydrogen gas, of which the Galaxy contains a great deal, flared away from the disk at large distances from the Galactic centre, but until now no one knew that stars did the same thing.

An infrared image (left) of the Cepheid named OGLE-BLG-CEP-32 and the stars which surround it, together with its SALT spectrum (insert right). These were used to show that the Cepheid was in the flare of the Galactic disk. Credit: Whitelock et al

The team who made the discovery are from South Africa and Japan: Prof Michael Feast (University of Cape Town – UCT, SAAO), Dr John Menzies (SAAO), Dr Noriyuki Matsunaga (the University of Tokyo, Japan) and Prof Patricia Whitelock (SAAO, UCT).

These results will be published in detail on 15 May, in the international journal Nature.

Explore further: Can super-fast stars unveil dark matter's secrets?

More information: Paper: dx.doi.org/10.1038/nature13246

Journal reference: Nature search and more info website

Provided by South African Astronomical Observatory

4.2 /5 (13 votes)
add to favorites email to friend print save as pdf

Related Stories

Can super-fast stars unveil dark matter's secrets?

May 13, 2014

Zoom! A star was recently spotted speeding at 1.4 million miles an hour (2.2 million km/hr), which happened to be the closest and second-brightest of the so-called "hypervelocity" stars found so far. ...

Image: Hubble looks into Terzan 7

Feb 17, 2014

Named after its discoverer, the French-Armenian astronomer Agop Terzan, this is the globular cluster Terzan 7—a densely packed ball of stars bound together by gravity. It lies just over 75,000 light-years ...

Video: Guide to our Galaxy

Nov 22, 2013

This virtual journey shows the different components that make up our home galaxy, the Milky Way, which contains about a hundred billion stars.

Massive stars mark out Milky Way's 'missing' arms

Dec 17, 2013

A 12-year study of massive stars has reaffirmed that our Galaxy has four spiral arms, following years of debate sparked by images taken by NASA's Spitzer Space Telescope that only showed two arms.

Recommended for you

Is the universe finite or infinite?

Mar 27, 2015

Two possiblities exist: either the Universe is finite and has a size, or it's infinite and goes on forever. Both possibilities have mind-bending implications.

'Teapot' nova begins to wane

Mar 27, 2015

A star, or nova, has appeared in the constellation of Sagittarius and, even though it is now waning, it is still bright enough to be visible in the sky over Perth through binoculars or a telescope.

Dark matter is darker than once thought

Mar 27, 2015

This panel of images represents a study of 72 colliding galaxy clusters conducted by a team of astronomers using NASA's Chandra X-ray Observatory and Hubble Space Telescope. The research sets new limits on ...

Galaxy clusters collide—dark matter still a mystery

Mar 26, 2015

When galaxy clusters collide, their dark matters pass through each other, with very little interaction. Deepening the mystery, a study by scientists at EPFL and the University of Edinburgh challenges the ...

Using 19th century technology to time travel to the stars

Mar 26, 2015

In the late 19th century, astronomers developed the technique of capturing telescopic images of stars and galaxies on glass photographic plates. This allowed them to study the night sky in detail. Over 500,000 ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

May 16, 2014
This comment has been removed by a moderator.
5 / 5 (5) May 16, 2014
It sorta violates the existing cosmological model, in which the oldest stars should exist at the center of clusters and galaxies instead

No. It's been long known that older population II stars exist on the outskirts of galaxies. This is because there hasn't been much star formation in that region in a long time leaving only older stars. This is seen in galaxy formation models, it does not violate standard cosmology.
May 16, 2014
This comment has been removed by a moderator.
5 / 5 (5) May 17, 2014
So why everyone gets so surprised, when such stars are found?

Because your article is about clusters Not galaxies. No science is not some grand conspiracy to extract grant money, you just don't read things properly. How stars form in clusters is not based on cosmological models.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.