Una visión diferente para disfrutar de la magia del Universo
Astronomía - Cosmología - Astrofotografía - Astrofísica - Exploración Espacial

💫Nuevo!! Universo Mágico muestra los catálogos astronómicos más populares. Búscalos en la barra superior de navegación y lateral.

💫Los aficionados ya pueden escribir sobre astronomía. Date de alta como Autor en Universo Mágico Público.

 ðŸ’«Si eres Autor prueba la opción Nueva Entrada

💫Grupos en Facebook: Astroimaging - Stars in the Sky - Astronomy Plus - Astrophotographers

💫Hint of planet-sized drifters bewilders Hubble scientists

Communities & Groups:     (New)  Space World Google+        Big Bang Facebook

Microlensing occurs when a background star brightens momentarily as a foreground object drifts by. The unusual objects thought to cause these events are far too dim to be seen directly, but instead were detected by the way their gravitational field amplifies light from a distant background star in the huge central bulge of our Galaxy. Microlensing has been used before to search for low-mass objects in the disc and halo of our Galaxy, but Hubble's sharp vision is essential to probe the interiors of globular clusters further. From 22 February to 15 June, 1999, Sahu and colleagues monitored 83,000 stars, detecting one clear microlensing event caused by a normal dwarf star in the cluster (about one-tenth the mass of our Sun). As a result of gravitational lensing, the background star appeared to grow 10 times brighter and then returned to its normal brightness over a period of 18 days. In addition to the microlensing event caused by the dwarf star, Sahu and his team recorded six even more interesting, unexpectedly brief events where a background star jumped in brightness by as much as a factor of two for less than 20 hours before dropping back to normal brightness. This means that the microlensing object must have been much smaller than a normal star. These microlensing events were unusually brief, indicating that the mass of the intervening object could be as little as 80 times that of Earth. So what are they? Theoretically they might be planets that were gravitationally torn away from parent stars in the cluster.

However, they are estimated to make up as much as 10 percent of the cluster's mass - too numerous to be wandering, 'orphaned' planets. The results are so surprising the astronomers caution that these preliminary observations must be confirmed by follow-up Hubble observations. If verified, these dark denizens could yield new insights about how stars and planets formed in the early Universe. 'Hubble's excellent sharpness allowed us to make this remarkable new type of observation, successfully demonstrating our ability to see very small objects,' says Sahu. 'This holds tremendous potential for further searches for dark, low-mass objects.' 'Since we know that globular clusters like M22 are very old, this result opens new and exciting opportunities for the discovery and study of planet-like objects that formed in the early Universe', adds co-investigator Nino Panagia (European Space Agency and Space Telescope Science Institute). 'This initial observation shows that our microlensing method works beautifully,' states co-investigator Mario Livio (Space Telescope Science Institute). As microlensing events are brief, unpredictable and rare, astronomers improve their chances of observing one by looking at many stars at once - much like a person buying several lottery tickets together. Most microlensing searches have been aimed at the central bulge of our Galaxy or out towards the Magellanic Clouds - the densest observable regions of stars in the sky.

In general these surveys cover areas of sky larger than the full Moon and look for foreground objects lying somewhere between us and the background population of stars. Sahu and his team took advantage of Hubble's superb resolution and narrow field of view to aim the telescope directly through the centre of a globular star cluster lying between Earth and the Galactic bulge. This gave the team a very dense stellar region to probe for drifting low-mass foreground objects and a very rich background field of stars to be lensed. Only Hubble's resolution is sharp enough to actually peer through the crowded centre of the cluster and see the far more distant stars in the galactic bulge. As the lensing objects were part of the cluster, the astronomers also had an accurate distance (8,500 light years) and velocity for these objects. In a normal lensing event, a background star brightens and dims for a length of time depending on the mass of the lensing body. The short, 'spurious' events seen by the team are shorter than the interval between the Hubble observations, leading to (only) an upper estimate for the mass of an object of one quarter of Jupiter's mass. To confirm these extraordinary, but tentative results, Sahu and colleagues next plan to monitor the centre of the globular cluster continuously over a seven-day interval. They expect to detect 10 to 25 short-duration microlensing events, which will be well-sampled enough to yield direct measurements of the true masses of the small bodies.

Credit: NASA, ESA & K. Sahu STScI

Communities & Groups:     (New)  Space World Google+        Big Bang Facebook

Publicar un comentario

Cada imagen expuesta en Universo Mágico tiene derechos de autor, para utilizar estas imágenes en otros sitios web debe pedir permiso al autor de la imagen, enlazado en éste sitio.
Para visualizar correctamente este sitio web utiliza un navegador basado en Chromium, o Fire Fox. Si te gusta la privacidad se recomienda utilizar Tor Browser.
Para la correcta visualización de la página de Husos Horarios utiliza Internet Explorer.
Universo Mágico hace uso de la base de datos astronómicos SIMBAD operado desde CDS, Estrasburgo, Francia

universo cosmos espacio astonomía cosmología exploración espacial astrofotografía astrofotógrafo astrónomo cosmólogo nebulosa galaxia nube oscura brillante estrella estrellas cúmulo estelar abierto globular planeta sol mercurio venus tierra marte júpiter saturno urano neptuno plutón ceres fobos deimos luna titán encelado europa calisto ganímedes ío caronte hydra nix cometa asteroide cinturón grupo galáctico supercúmulo planetaria emisión reflexión absorción polvo gas atmósfera rayos X gamma cuásar púlsar herbig-haro constelación asterismo fugaces meteoros meteoritossatélite iss estación cohetetelescopio hubble chandra spitzer nustar xmm-newton most very vlt vla vst vista herschel soar ssro sloan rosetta rosat philae osiris subaru campanas kitt keck wilson observatorio palomar calar horizons voyager mpg mycron merlin maven express mariner magellan juno grand canarias gemini hawk galileo galex gaia fuse digited dawn clementine cassini apolo apex alma agujero agujeros polo norte sur sistema solar vacío local big bang oculta coronalunar solar cráter superluna sangre eclipse total parcial ocultación luminiscencia refracción destello anular tránsito protuberancia filamento mancha manchas solares andrómeda messier enana física físico ngc ic trío arp melotte doradus barnard pilares trompa burbuja nuro cabeza cisne cygnus sh2 shapley mz rho sagittarius tarántula magallanes gran pequeña triángulo pickering torre variable binaria espectroscópica bennu thule carinae cygnicom coma virgo cuarteto quinteto cadena energía color markarian tritón molecular supernova nova remanente explosión frente choque einstein caldwell darwin huygens ptolomeo halley piggot gillett hale riccioli gentil newton bode kepler dreyer harding copérnico lacaille loys pierre hawking ciencia científicos cielo arcoiris lenticular espiral elíptica barrada brazo brazos región regiones vdb rcw año luz parsec grado grados celsius farenheit kelvin minuto minutos arco arcominutos oculta llena oscura partículas átomo átomos temperatura millones miles luz espectro universe cosmos space astonomy cosmology space exploration astrophotography astrophotographer astronomer cosmologist nebula galaxy cloud dark shining star stars star cluster open globular planet sun mercury venus earth mars jupiter saturn uranus neptune pluto ceres fobos deimos moon titan waxed europe calist ganymede charontera hydra nix comet aste group hydra nix comet aste group hydra nix comet band galactic planetary supercluster emission reflection absorption dust gas atmosphere x-ray gamma quasar pulsar herbig-haro constellation asterism fleeting meteor meteorite satellite iss station rockettelescope hubble chandra spitzer nustar xmm-newton most very vlt vla vst view herschel soar ssro sloan rosetta rostar ketar keckar ketar ketar ketar subtle rosat ketar roster ketsar keta subar kitty wilson observatory pigeon jello horizons voyager mpg mycron merlin maven express mariner magellan juno grand canarias gemini hawk galileo galex gaia fuse digited dawn clementine cassini apollo apex soul hole aguj eros north pole south solar system empty local big bang hidden coronalunar solar crater supermoon blood eclipse total partial concealment luminescence refraction ring flash transit protuberance filament spot sunspots andromeda messier dwarf physical physics ngc ic trio arp melotte doradus barnard pillars trunk nuro head swan cygnus sh2 shapley mz rho sagittarius tarantula magallanes large small triangle pickering variable tower binary spectroscopic bennu thule carinae cygnicom coma virgo quartet quintet chain energy color markarian molecular triton supernova nova remnant explosion front shock shock einstein caldwell darwin huygens ptolomeo halley piggot gyerton keplentil dd gillett harder keterton gilton kepleton dilton graveyard copernicus lacaille loys pierre hawking science scientists sky rainbow lenticular spiral elliptic barred arm arms region regions vdb rcw year light parsec degree degrees celsius farenheit kelvin minute minutes arc minute arch hidden full dark particles atom atoms temperature millions thousand light spectrum