The Pleiades star cluster

Transcription

1 The Pleiades star cluster

2 Background Modern- day astronomy sees the Pleiades quite differently. Astronomers say this cluster of several hundred stars condensed out of a cloud of gas and dust some 100 million years ago. The Pleiades stars lie nearly 400 light- years away. In ancient Greek stories, two of Pleiades were the parents and the rest were their children now all teenage sisters. When you look up at the Pleiades, you may only see five or six stars. Binoculars reveal over a hundred more. Large telescopes have found over 3,000 stars in the Pleiades family. Born while the dinosaurs were roaming the Earth, the Pleiades family has been together about 100 million years. v This cluster is young and just starting out in the Galaxy Scientists call groups of stars like the Pleiades an open star cluster. v v v v v {

3 Distance: 440 light- years Consists of about 3,000 stars Visual Magnitude: 1.6 Apparent dimension: 110 arcminutes (about the width of 2 fingers held at arm s length) Actual dimension: About 13 light- years across To view: binoculars or small telescope lustration via Alexandra Angelich, NRAO/AUI/ NSF.

4 How to find it The Pleiades or Seven Sisters form a beautiful star cluster near the constellation Taurus. 1. From the Northern Hemisphere: Look for the Pleiades in autumn and winter. In the Northern Hemisphere, the Pleiades star cluster becomes visible to evening observers in October and disappears in April. November is the best time to look for the Pleiades, when they are visible from dusk to dawn and reach their highest point in the sky.[ 2. Face the southern sky. The Pleiades rise in the southeast after dusk and travel west during the night. During their peak in November, they climb high in the sky and disappear in the northwest before dawn. hep:// the- Pleiades- Star- Cluster

5 The Pleiades is not the Liele Dipper Many think the Pleiades cluster looks like a liele dipper. But to see the group of stars we call The Liele Dipper you need to face north. While The Pleiades face the southern sky.

6 Why is the Pleiades star cluster called the seven sisters? In Greek mythology, the Pleiades represent the seven daughters of the titan Atlas and the sea- nymph Pleione. The sisters were Maia, Electra, Alcyone, Taygete, Asterope, Celaeno and Merope. They were said to be half- sisters of the seven Hyades. In ancient Greek stories, two of Pleiades were the parents and rest were their children now all teenage sisters. So why are the Pleiades called the Seven Sisters, when only six stars can be seen with the eye? In fact, the number of stars you can see within the Pleiades cluster, using just your eye, varies depending on your own eyesight, local atmospheric transparency and light pollution levels.

7 The seven Pleiades cluster stars Taygeta Taygeta A, is a blue-white B-type subgiant with an apparent magnitude of It is a spectroscopy binary, whose component stars have magnitudes of +4.6 and Electra It is the third brightest star in the Pleiades open star cluster (M45). Electra belongs to the spectral class B6 and is approximately 400 light years from the Sun. The Pleiades cluster is thought to be 444 light years away. Asterope Is the traditional name of a double star, whose components are designated 21 Tauri and 22 Tauri, in the constellation of Taurus. Celaeno Also designated 16 Tauri, is a star in the constellation of Taurus and a member of the Pleiades open star cluster (M45) of stars. 16 Tauri is a blue-white B-type subgiant with an apparent magnitude of It is approximately 430 light years from the Sun. Pleione Is a binary star and the seventh-brightest star in the Pleiades star cluster (Messier 45). It is located approximately 120 parsecs (390 light-years) from the Sun, appearing in the constellation of Taurus. Alcyone Is the brightest star in the Pleiades open cluster. Approximately 440 light years from the Sun.

8 Scientist find that the stars in the Pleiades are variable Scientist use the Kepler Space Telescope to discover and study variability in the Pleiades brightest stars. A new technique called halo photometry which is able to spot relative brightness changes in stars. The algorithm looks at pixels on the camera detector next to, rather than those that fall directly on, the brightest part of stars. Most of the stars are slowly pulsating B- type stars. These massive, bright stars change brightness every one to five days.

9 K2 MISSION u To enhance observations from the Kepler Space Telescope in its K2 Mission, scientists developed a new and novel algorithm to perform the most detailed study yet of variable stars in the Pleiades star cluster. u Halo photometry - stars pulsating B type stars u The Pleiades exhibits one of the finest and nearest examples of a reflection nebula associated with a cluster of young stars.

10 Maia Maia exhibits regular changes every 10 days. Curious the scientist observed the star with the Herjsprung SONG Telescope. By looking at spectra, which identify the chemical components of the star, they determined that the brightness changes Kepler saw co- occur with changes in the element manganese in the star s atmosphere. Credits picture: PicQuery

11 Herjsprung SONG Telescope data Image credit: Aarhus University / T. White

12 Other Observations This picture is not the product of a fertile imagination. This is a photograph of an interstellar cloud in the process of disintegration by intense radiation from an adjacent hot star The cloud IC 349 or Barnard'ʹs Merope Nebula is illuminated by Merope in the Pleiades star Cluster. The cloud, which is part of Tempel'ʹs Nebula Image credit:pleiadesassociate or NGC 1432, is drifting through the Pleiades star cluster. As a result of its close proximity of the cloud and the star in astronomical terms of about 0.06 light- years (say 550 billion kilometers) the cloud has been extensively deformed. It selectively decelerates the particles: less massive dust particles are subject to greater deceleration than larger particles. The radiation pressure thus acts as a sieve, sifting the particles by size. The clearly formed linear structures directed toward the star are streams of larger particles, whereas the smaller and thus more decelerated particles are, for the moment, retained within the main body of the cloud.

13 Kepler s forte is studying brightness changes in stars associated with the transit of orbiting planets. The satellite s ability to accurately measure fluctuations in starlight also makes it an ideal tool to identify and study any cause of brightness changes from a star, such as pulsations or starspots. Kepler is now in its K2 mission, Kepler did not identify any transiting exoplanets during this study; however, the team says their new algorithm will allow Kepler and other planet- hunting telescopes to beeer search for planets around bright stars. They have also released the halo photometry algorithm as free open- source software for the community to use. Images credit: Earthsky

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15 Citations: Writer, H.W. (n.d.). NASA s Planet- Hunting Kepler Tackles Mysteries of the Pleiades Seven Sisters. Retrieved October 01, 2017, from heps:// Kepler Not quite the Liele Dipper: Space blog says heads up this week for stunning star phenomenon.2017/mlive.com How to Find the Pleiades Star Cluster/ WikiHow. hep:// the- Pleiades- Star- Cluster NROA astronomers pin down distance to Pleiades stars EarthSky.org T.R. White et al Beyond the Kepler/K2 bright limit: variability in the seven brightest members of the Pleiades Atlas (star). En.wikipedia.org Why is the Pleiades star cluster called the Seven Sisters? EarthSky.org Pleiade Associates The Pleiades in reality... Pleiades star cluster. Pleiade.org News The University of Sydney. Sydney.edu.au Scientists find that the stars in the Pleiades are variable. Astronomy.com Universe discovery guide. NASA/ Pleiades star cluster