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Penn Astrophysicists Zero In on Gravity Theory

In 1998, astrophysicists made an observation that turned gravity on its ear: the universe’s rate of expansion is speeding up. If gravity acts the same everywhere, stars and galaxies propelled outward by the Big Bang should continuously slow down, like objects thrown from an explosion do here on Earth.

This observation used distant supernovae to show that the expansion of the universe was speeding up rather than slowing down. This indicated that something was missing from physicists’ understanding of how the universe responds to gravity, which is described by Einstein’s theory of general relativity. Two branches of theories have sprung up, each trying to fill its gaps in a different way.

One branch — dark energy — suggests that the vacuum of space has an energy associated with it and that energy causes the observed acceleration. The other falls under the umbrella of “scalar-tensor” gravity theories, which effectively posits a fifth force (beyond gravity, electromagnetism and the strong and weak nuclear forces) that alters gravity on cosmologically large scales.

“These two possibilities are both radical in their own way,” Jain said. “One is saying that general relativity is correct, but we have this strange new form of energy. The other is saying we don’t have a new form of energy, but gravity is not described by general relativity everywhere.”

Astronomers are scanning the heavens for flashes of light that may signal the formation of a black hole, empowered by a new theory that indicates a dying star will generate a distinct flash of light that will allow man to witness the birth of a new black hole for the first time. (Photo : Credit: Alain Riazuelo, IAP/UPMC/CNRS)

(via Black Hole Birth Can Be Observed For First Time, Study Says : Space : Nature World News)

(via Astronomers Discover New Neighbor Galaxy to the Milky Way: Scientific American)

Leo P is one of just a few dozen local galaxies that does not swarm around the Milky Way or its massive sibling Andromeda, each of which has been extensively scanned for companion galaxies in recent years. “There has been a massive increase in the number of these nearby galaxies” around the Milky Way and Andromeda, says astronomer Alan McConnachie of the National Research Council Canada’s Herzberg Institute of Astrophysics, who did not contribute to the new research. “There have really been very, very few discoveries of dwarfs that are sort of sitting out in the middle of nowhere.” Those lonely dwarf galaxies, such as Leo P, are hard to spot because they are faint, distant, and could be found anywhere on the sky.

First Tunguska Meteorite Fragments Discovered

Nobody knows what exploded over Siberia in 1908, but the discovery of the first fragments could finally solve the mystery.

TMT’s primary segmented mirror will be made up of 492 smaller mirrors and measure thirty meters across—three times the diameter and nine times the collecting area of the giant Keck Telescope. Once considered inferior to space-based telescopes like Hubble, ground-based optical telescopes are rapidly overtaking their space-based brethren. TMT will deliver images 12 times sharper than those taken by Hubble.

How’s that possible? The first ground-based strategy is to locate in a remote place to minimize pollution (light and air) and high up to minimize cloud cover. Hawaii’s Mauna Kea is an ideal spot, and its slopes are already dotted with observatories.

But the atmosphere itself, no matter how clear or free of pollution, deforms light waves. Computer-powered adaptive optics correct that distortion by studying a laser-projected artificial “guide star” near the point of observation in the upper reaches of Earth’s atmosphere. The telescope’s computer notes how the layers of air distort the guide star’s light and uses actuators to shift segments of the primary mirror, correcting the observed wave pattern.

(via Giant Next-Generation Thirty Meter Telescope Gets Permit From Hawaii to Build on Mauna Kea

When a massive power outage struck southern California in the 1990s, Los Angeles residents reportedly called 911 to express alarm about strange clouds hovering overhead; they were seeing the Milky Way for the first time.

Seeing in the Dark . Astronomy Topics . Light Pollution

waning gibbeous on Flickr.

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(via The Cosmic Speed Limit – Starts With A Bang)

After all, a proton is a relatively heavy particle, some 1,836 times heavier than it’s orbiting friend, the electron! Even though we’ve created protons that are at higher energies than electrons, it only takes one-1,836^th the energy (or 0.054%) to get the electron up to the same speed. Which means that LEP — the Large Electron-Positron Collider (and the LHC’s predecessor) — where they got electrons up to 104.5 GeV of energy (compared to the 6,500 GeV expected for the LHC after the upgrade), still holds the record for particle accelerator record speed.

What is that speed? 299,792,457.9964 meters per second, or a whopping 99.9999999988% the speed of light, just 3.6 millimeters-per-second slower than light in a vacuum!

But that’s just here on Earth, with our lame superconducting electromagnet accelerators, powered by puny chemical energy sources. Compared to what comes out of the Universe, our terrestrial sources don’t stand a chance.

(via Moon Landing Hoax Believers Follow Party Lines: Report | Space.com)

Dissipating turbulence
Modeling the sun has been a sticky problem for decades. The first attempts in the 1980s captured only a rough approximation of the turbulence inside of the sun.

Turbulence, when it occurs, happens at both large and small scales. The large scales are easy to simulate, but in the sun, a small feature only about tens of miles across is just as important in understanding how fluid propagates.

When energy from turbulence dissipates, the turbulence flows into smaller and smaller whirlpool shapes, called vortices. You can see this for yourself, Charbonneau said, when swirling your hand in a full bathtub. The movement will produce a vortex in the water that will gradually break up into tinier ones that dissipate the energy.

On the sun, dissipation takes place at a scale of tens of yards. That’s extremely minute, compared with the size of the sun, which is 1 million times larger than Earth. “There’s no way we can capture that in a simulation,” Charbonneau told Space.com.

To approximate this process, scientists typically limit the resolution to about 6.2 miles (10 kilometers). This, however, creates an energy buildup in the simulation that will “blow up” the model before it can run for very long, Charbonneau said.

(via Sun’s magnetic ‘heartbeat’ is discovered - Science)