Hubble Telescope: Solved and Unsolved Mysteries

Beyondsnapping extraordinary pictures of faraway nebulas, the revolutionary HubbleSpace Telescope has completely transformed our view of the universe since itwas launched in 1990. By capturing the clearest, deepest images of the cosmosever, Hubble has shed light on some long-standing mysteries perplexingscientists?while uncovering far deeper ones that have yet to be solved.

The push of dark energy

Theuniverse was born in the Big Bang, but before Hubble, its age was uncertain. Bymeasuring where distant galaxies are more accurately than ever before and howfast they are moving as the universe expands, the orbiting telescope resolvedthe cosmos is roughly 13.7 billion years old.

However,at the same time, Hubble and various ground telescopes unexpectedly discoveredthat the universe's expansion is accelerating, instead of slowing downas one might expect due to the pull of gravity from galaxies. The repulsiveforce driving this accelerating expansion, dubbed darkenergy, which makes up some 70 percent of the universe, remains "oneof the greatest mysteries in science," said Hubble senior project scientistDavid Leckrone.

Darkenergy has prompted new theories regarding the origin of the universe, such asone where clashingmembranes of reality trigger endless cycles of cosmic death and rebirth, aswell as the fate of the universe, raising the possibility that dark energy endsthe universe in a Big Rip.Future progress on understanding dark energy's nature will likely require adedicated dark energy space mission, "for sometime in the middle of thenext decade, perhaps," Leckrone said.

The pull of dark matter

Galaxiesdon't have enough normal matter to hold together the giant clusters of galaxiesthey are in, leading scientists to speculate on the existence of gravity fromunseen "darkmatter" pulling to keep galaxies together.

Althoughwhat dark matter actually is remains a mystery, Hubble did help show howmuch there is of it out there, by looking for how much dark matter's gravitywarps space-time and thus distorts light from distant galaxies. The spacetelescope helped reveal there is some five or six times more dark matter thannormal matter in the universe.

Hubblealso has, with other telescopes, developed the first3-D map of dark matter. "This helped show the clumpiness of darkmatter has apparently increased over time, showing it exhibits ordinarygravity, as opposed to something else," Leckrone said. Betterunderstanding how dark matter behaves could help scientists better understandwhat it actually is, he added. In the meantime, the 3-D dark matter map helpsexplain "how theuniverse acquired the large-scale 'web-like' structure that we observe in thepattern in which galaxies are distributed over the sky," he added.

Other mysteries solved and unsolved

The biggest explosions in the universe

Satellitesfirst discovered gammaray bursts, the biggest explosions in the universe, in the late 1960s, butscientists had little idea where they came from. Hubble helped discover theyoriginated for the most part come from hot, young, very massive stars indistant galaxies, "which we think catastrophically collapsed on themselvesto produce these gamma ray bursts," Leckrone said. "We believe theymust be going off all over the place out across the universe."

Photographing worlds

NeitherHubble nor any other telescope so far has directly imaged an exoplanet."There was one object that was claimed to be a planet, and it may well be,but it's a huge distance from its central star and is abnormally bright, so Idon't think it really is," Leckrone said.

Protoplanetary disks

Hubblewas the first to directly image the disks of gas and dust where planets areborn with great detail, pictures sharp enough to reveal the gaps in the disksthat nascent worlds carved out as they orbited their stars. "Thesefindings help shed light on how worlds form, although there's quite a ways togo with that research," Leckrone said.

Hubble's successors

TheJamesWebb Space Telescope is intended as a significant improvement over Hubble,an orbital infrared observatory capable of picturing substantially fainterobjects. It might even "have a fighting chance to directly image a planetaround another star," Leckrone said.

Aslight shed in earlier ages of the universe naturally shifts toward theinfrared, distorted as it is by the expansion of the universe, Leckrone addedthe James Webb Space Telescope should also help peer back to an era unseenuntil now, when the first galaxies formed back when the universe was only a fewhundred million years old. Investigating these early galaxies could shed lighton the poorly understood process of how galaxies like our own Milky Way formed.

Still, Hubble will continue toprove invaluable for imaging the universe at visible and ultravioletwavelengths, Leckrone added.

"Althoughthe James Webb Space Telescope can be viewed as a successor to Hubble, it is not areplacement for Hubble," Leckrone said. "Ultimately, a much larger ultraviolet-visibletelescope in space will be needed to carry on Hubble?s work."

• VOTE: Hubble's Best Images
• NASA's Next Big Telescope Passes Brain Test
• 'Lucky' Camera Rivals Hubble's Clarity