Dátum: 1997. október 9., csütörtök (13:06 UT) |
Feladó: Valas Gyorgy |
Tárgy: Re: Pisztoly csillag |
>Kedves Csilla-tarsak!
>Ma reggel azt hallottam a radiobol, hogy amerikai csillagaszok a
>Hubble urteleszkoppal megtalaltak a valoszinuleg legnagyobb energiaju
>csillagot a vilagegyetemben. (tizmillioszor nagyobb energiaju a
>Napnal)
>Veres Jozsef
>Ma reggel 7 orakor a Kossuth Radio a hirek kozott azt is bemondta,
>hogy a Hubble
>teleszkop segitsegevel amerikai csillagaszok felfedeztek az
>vilagegyetem legnagyobb,
>legfenyesebb csillagat. Pisztolycsillagnak neveztek el a csillagot
>takaro revolver alaku kod miatt.
>Udv. Tibi
A mai (okt. 9.) lapban már pontosabb volt a hír: a Tejút eddig ismert
legnagyobb és legfényesebb csillaga, tőlünk kb. 25 000 fényévre, a
Sagittarius irányában.
Fontossága és az amerikai vonal zsúfoltsága miatt ide másolom a Space
Telescope Science Institute eredeti sajtójelentését
http://oposite.stsci.edu/pubinfo/PR/97/33/PR.html
-ről:
[ST ScI HST NEWS]
EMBARGOED UNTIL: 9:00 a.m. (EDT) October 8, 1997
CONTACT:
Tammy Jones
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-5566)
Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone: 410-338-4514)
Harlan Lebo
University of California at Los Angeles, Los Angeles, CA
(Phone: 310-206-0510)
(E-mail:
PRESS RELEASE NO.: STScI-PR97-33
Hubble Identifies What May Be the Most Luminous Star Known
Astronomers using NASA's Hubble Space Telescope have identified what may be
the most luminous star known -- a celestial mammoth which releases up to 10
million times the power of the Sun and is big enough to fill the diameter
of Earth's orbit. The star unleashes as much energy in six seconds as our
Sun does in one year.
The image, taken by a University of California, Los Angeles (UCLA)-led team
with the recently installed Near-Infrared Camera and Multi-Object
Spectrometer (NICMOS) aboard Hubble, also reveals a bright nebula, created
by extremely massive stellar eruptions. The nebula is so big (four
light-years) that it would nearly span the distance from the Sun to Alpha
Centauri, the nearest star to Earth's solar system.
The astronomers estimate that when the titanic star was formed one to three
million years ago, it may have weighed up to 200 times the mass of the Sun
before shedding much of its mass in violent eruptions.
"This star may have been more massive than any other star, and now it is
without question still among the most massive -- even at the low end of our
estimates," says Don F. Figer of UCLA. "Its formation and life stages will
provide important tests for new theories about star birth and evolution."
Violent Eruptions Produce Nebula
The UCLA astronomers estimate that the star, called the "Pistol Star" (for
the pistol shaped nebula surrounding it), is approximately 25,000
light-years from Earth near the center of our Milky Way galaxy. The Pistol
Star is not visible to the eye, but is located in the direction of the
constellation Sagittarius, hidden behind the great dust clouds along the
Milky Way.
The Pistol Star was first noted in the early 1990s, but its relationship to
the nebula was not realized until 1995, when Figer proposed in his Ph.D.
thesis that the "past eruptive stages of the star" might have created the
nebula. The Hubble spectrometer results confirm this conclusion.
The astronomers believe that the Pistol nebula was created by eruptions in
the outer layers of the star which ejected up to 10 solar masses of
material in giant outbursts about 4,000 and 6,000 years ago. The star will
continue to lose more material, eventually revealing its bare hot core,
sizzling at 100,000 degrees.
Burning at such a dramatic rate, the Pistol Star is destined for certain
death in a brilliant supernova in 1-3 million years. "Massive stars are
burning their candles at both ends; they are so luminous that they consume
their fuel at an outrageous rate, burning out quickly and often creating
dramatic events, such as exploding as supernovae," said Mark Morris, a UCLA
professor of astronomy and co-investigator. "As these stars evolve, they
can eject substantial portions of their atmospheres -- in the case of the
Pistol Star, producing the nebula and an extreme stellar wind (outflow of
charged particles) that is 10 billion times stronger than our Sun's." The
Pistol Star would be visible to the naked eye as a fourth magnitude star in
the sky (which is quite impressive given its distance of 25,000
light-years) if it were not for interstellar dust clouds of tiny particles
between the Earth and the center of the Milky Way that absorb the star's
light. The most powerful telescopes cannot see the Pistol Star in visible
wavelengths. However, ten percent of the infrared light leaving the Pistol
Star reaches Earth, putting it within reach of infrared telescopes, which
have seen rapid technological advances in recent years -- spurred by
projects such as NICMOS. The Pistol Star was so massive when it was born
that it brings into question current thinking about how stars are formed,
say the UCLA astronomers. In the current view, stars form within large dust
clouds which contract under their own gravity, eventually forming hot
clumps that ignite the hydrogen fusion process.
The star may radiate enough energy to halt the inward fall of material,
thus limiting its maximum mass. The initial mass of the Pistol Star may
have exceeded this theoretical upper limit. "It is perhaps no accident that
this extreme-mass star is found near the center of the Galaxy," says
Morris. "Current evidence leads us to believe that the star formation
process there may favor stars much more massive than our modest Sun."
Over the coming year, the team will be using the new near-infrared
spectrometer that Ian S. McLean's team is building at UCLA for the giant
10-meter Keck II telescope in Hawaii. The new instrument will be used to
measure the velocities of the expanding gas shells.
In addition to Figer, Morris, and McLean, the team also includes Caltech
physicist Gene Serabyn and Columbia University astronomer R. Michael Rich .
The Space Telescope Science Institute is operated by the Association of
Universities for Research in Astronomy, Inc. (AURA), for NASA, under
contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble
Space Telescope is a project of international cooperation between NASA and
the European Space Agency (ESA).
Jonathan Eisenhamer --
Zolt Levay --
Office of Public Outreach --
A magasabb web-szint, ahonnan a képek is elérhetők:
http://oposite.stsci.edu/pubinfo/PR/97/33.html
Válas György