Plaetje:Messier22.jpg

Globular cluster Messier 22

Besjrieving

From NASA Press Release June 27, 2001 02:00 PM (EDT) News Release Number: STScI-2001-20 Hint of Planet-Sized Drifters Bewilders Hubble Scientists

Piercing the heart of a glittering swarm of stars, NASA's sharp-eyed Hubble Space Telescope unveils the central region of the globular cluster M22, a 12- to 14-billion-year-old grouping of stars in the constellation Sagittarius. The telescope's view of the cluster's core measures 3.3 light-years across.

The stars near the cluster's core are 100,000 times more numerous than those in the Sun's neighborhood. Buried in the glow of starlight are about six "mystery objects," which astronomers estimate are no larger than one quarter the mass of the giant planet Jupiter, the solar system's heftiest planet.

The mystery objects are too far and dim for Hubble to see directly. Instead, the orbiting observatory detected these unseen celestial bodies by looking for their gravitational effects on the light from far distant stars. In this case, the stars are far beyond the cluster in the galactic bulge, about 30,000 light-years from Earth at the center of the Milky Way Galaxy. M22 is 8,500 light-years away. The invisible objects betrayed their presence by bending the starlight gravitationally and amplifying it, a phenomenon known as microlensing.

From February 22 to June 15, 1999, Hubble's Wide Field and Planetary Camera 2 looked through this central region and monitored 83,000 stars. During that time the orbiting observatory recorded six unexpectedly brief microlensing events. In each case a background star jumped in brightness for less than 20 hours before dropping back to normal. These transitory spikes in brightness mean that the object passing in front of the star must have been much smaller than a normal star. Hubble also detected one clear microlensing event. In that observation a star appeared about 10 times brighter over an 18-day span before returning to normal. Astronomers traced the leap in brightness to a dwarf star in the cluster floating in front of the background star.

The inset photo shows the entire globular cluster of about 10 million stars. M22 is about 60 light-years wide. The image was taken in June 1995 by the Burrell Schmidt telescope at the Case Western Reserve University's Warner and Swasey Observatory on Kitt Peak in Arizona.

Object Name: M22

Image Type: Astronomical

Credits for the Hubble image: NASA, Kailash Sahu, Stefano Casertano, Mario Livio, Ron Gilliland (Space Telescope Science Institute), Nino Panagia (European Space Agency/Space Telescope Science Institute), Michael Albrow and Mike Potter (Space Telescope Science Institute)

Credits for ground-based image: Nigel A.Sharp, REU program/AURA/NOAO/NSF

Licentie:

	Dit bestand bevindt zich in het publiek domein, omdat het gemaakt is door de NASA. In de reproductierichtlijnen van de NASA staat dat "NASA-materiaal niet beschermd wordt door auteursrecht, tenzij anders vermeld". (NASA copyright policy page of JPL Image Use Policy).
	Waarschuwingen: Het gebruik van logo's, insignes en emblemen van de NASA wordt beperkt door de Amerikaanse wet 14 CFR 1221. Op de website van de NASA staat een groot aantal afbeeldingen van het Sovjet-/Russisch ruimteagentschap en andere niet-Amerikaanse ruimteagentschappen. Deze afbeeldingen bevinden zich niet noodzakelijk in het publieke domein. Materiaal dat gebaseerd is op gegevens van de ruimtetelescoop Hubble wordt mogelijk beschermd door auteursrecht als dit niet expliciet vervaardigd is door het STScI [1]. Zie tevens {{PD-Hubble}} en {{Cc-Hubble}} of {{Spacetelescope.org}}. Het gemeenschappelijk project van ESA en NASA betreffende de ruimtesonde SOHO suggereert dat al het materiaal dat gemaakt is door zijn ruimtesonde beschermd wordt door auteursrecht en dat toestemming vereist is voor commercieel niet-educatief gebruik. [2] Afbeeldingen op de Astronomy Picture of the Day-website (APOD) worden mogelijk beschermd door auteursrecht. [3]