* Astronomy

Members Login
Post Info TOPIC: Mira AB


L

Posts: 130044
Date:
Omicron Ceti
Permalink  
 


Most of the stars in our sky shine with a steady, unchanging light, save for the rapid twinkling that occurs because of turbulence in the Earths atmosphere. Its rather surprising to learn that some stars can vary their light output by a factor of hundreds or even thousands in only a few days, weeks or months. These variable stars offer us the opportunity to witness rapid evolutionary changes in the lives of the stars.
One of the most remarkable of the variable stars is Omicron Ceti, also known as Mira. Mira has been noticed off and on by astronomers throughout the centuries, all the way back to the Greek astronomer Hipparchus in 134 B.C. But it was an amateur astronomer, David Fabricius, who, in 1596, realised that this star was a variable star. The great astronomer Johann Hevelius coined the name Mira for this star in 1662, a name that means "Wonderful."

Read more


__________________


L

Posts: 130044
Date:
Mira
Permalink  
 


Mira, in the constellation Cetus, is a strange pulsating variable star that fades in and out of view every 11 months. The name Mira means wonderful; this star exhibits the largest change in brightness except for novae and supernovae. If you're keen, you can make your own observations of Mira and contribute to astronomical research.

Read more

__________________


L

Posts: 130044
Date:
RE: Mira AB
Permalink  
 


Title: Discovery of an HI Counterpart to the Extended Tail of Mira
Authors: L. D. Matthews (CfA), Y. Libert (Observatoire de Paris), E. Gerard (Observatoire de Paris), T. Le Bertre (Observatoire de Paris), M. J. Reid (CfA)

We report the detection of an HI counterpart to the extended, far-ultraviolet-emitting tail associated with the asymptotic giant branch star Mira (o Ceti). Using the Nancay Radio Telescope (NRT), we have detected emission as far as 88' north of the star, confirming that the tail contains a significant atomic component (M_HI ~ 4x10e-3 M_sun). The NRT spectra reveal a deceleration of the tail gas caused by interaction with the local interstellar medium. We estimate an age for the tail of ~1.2x10e5 years, suggesting that the mass-loss history of Mira has been more prolonged than previous observational estimates. Using the Very Large Array (VLA) we have also imaged the HI tail out to ~12' (0.4 pc) from the star. The detected emission shows a "head-tail" morphology, but with complex substructure. Regions with detected HI emission correlate with far-ultraviolet-luminous regions on large scales, but the two tracers are not closely correlated on smaller scales (<1'). We propose that detectable tails of HI are likely to be a common feature of red giants undergoing mass-loss.

Read more (606kb, PDF)

__________________


L

Posts: 130044
Date:
Permalink  
 

Title: It's a wonderful tail: the mass loss history of Mira
Authors: C. J. Wareing (Univ. of Leeds, UK), A. A. Zijlstra (Univ. of Manchester, UK), T. J. O'Brien (Univ. of Manchester, UK), M. Seibert (Observatories of the Carnegie Institution of Washington)

Recent observations of the Mira AB binary system have revealed a surrounding arc-like structure and a stream of material stretching 2 degrees away in opposition to the arc. The alignment of the proper motion vector and the arc-like structure shows the structures to be a bow shock and accompanying tail. We have successfully hydrodynamically modelled the bow shock and tail as the interaction between the asymptotic giant branch (AGB) wind launched from Mira A and the surrounding interstellar medium. Our simulations show that the wake behind the bow shock is turbulent: this forms periodic density variations in the tail similar to those observed. We investigate the possibility of mass-loss variations, but find that these have limited effect on the tail structure. The tail is estimated to be approximately 450,000 years old, and is moving with a velocity close to that of Mira itself. We suggest that the duration of the high mass-loss phase on the AGB may have been underestimated. Finally, both the tail curvature and the rebrightening at large distance can be qualitatively understood if Mira recently entered the Local Bubble. This is estimated to have occurred 17 pc downstream from its current location.

Read more  (714kb, PDF)

__________________


L

Posts: 130044
Date:
Permalink  
 

Astronomers  have recorded stunning images of a galactic phenomenon previously unknown - a distant star with a comet-like tail powerful enough to form planets. The trail of carbon, oxygen and other cosmic matter behind the giant red star Mira (Latin for wonderful) is 13 light years long - about 20,000 times the distance from Pluto to the Sun.

Read more

__________________


L

Posts: 130044
Date:
Permalink  
 

This artist's animation illustrates a star flying through our galaxy at supersonic speeds, leaving a 13-light-year-long trail of glowing material in its wake. The star, named Mira (pronounced my-rah) after the Latin word for "wonderful," sheds material that will be recycled into new stars, planets and possibly even life. NASA's Galaxy Evolution Explorer discovered the long trail of material behind Mira during its survey of the entire sky in ultraviolet light.



Credit: NASA/JPL



__________________


L

Posts: 130044
Date:
RE: Mira A
Permalink  
 


A glowing, comet-like tail has been discovered trailing behind a double star called Mira, a phenomenon never seen before. It may contain clues about the star's activity over the past 30,000 years.

miraA_e1
Expand (73kb, 560 x 312)
GALEX images reveal a long tail left by a red giant star as it ploughs through the galaxy. The star and its white dwarf companion are in the darkest part of the trail on the right
Credit: C. Martin et al./GALEX


Watch an animation of Mira creating the tail (QuickTime, 6 MB).

Read more

__________________


L

Posts: 130044
Date:
Permalink  
 

Galex image of Mira
The tail measures a massive 13 light years in length

A distant star that hurtles through space at extraordinary speeds has a huge, comet-like tail trailing in its wake, astronomers say.

The appendage, which measures a colossal 13 light years in length, was spotted by Nasa's Galaxy Evolution Explorer (Galex) space telescope.

The researchers said that nothing like it had ever been spotted around a star.

Read more 

__________________


L

Posts: 130044
Date:
RE: Mira AB
Permalink  
 


Like other stars in the advanced red giant phase of life, Mira A is sloughing off large amounts of gas and dust - about one Earth mass every seven years. The new observations have revealed that some of this material has been captured into a disc that orbits its companion at about the distance of Saturn from the Sun.
The disc is the sort of structure where planets are thought to form. And if planets do exist there, they appear to be endowed with some of the raw materials necessary for life - including carbon, in the form of carbon monoxide.

Read more

__________________


L

Posts: 130044
Date:
Permalink  
 

Astronomers generally assume that the dusty disks where planets form are found around young stars in stellar nurseries. Now, for the first time, a protoplanetary disk has been found in the environment of a dying star.
A team of astronomers is reporting today at the winter meeting of the American Astronomical Society that material from the dying star Mira A is being captured into a disk around Mira B, its companion. Michael Ireland of the California Institute of Technology and his coauthors, John Monnier from the University of Michigan, Peter Tuthill from the University of Sydney, and Richard Cohen from the W.M. Keck Observatory, say that the finding implies that there should be many similar undiscovered systems in the solar neighbourhood, providing a myriad of new places to look for young extrasolar planets.
Located 350 light years away in the constellation of Cetus, Mira (christened the “Miracle star”) first shook the foundations of the astronomy world 400 years ago with its changing brightness: visible to the naked eye for about 1 month at a time, becoming 1,000 times fainter and disappearing from view, only to re-appear again on an 11 month cycle.

Read more

Mira
Expand (12kb, 560 x 386)
Credit: Michael Ireland, Caltech

__________________
«First  <  1 2 3 4  >  Last»  | Page of 4  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard