Tag: astronomy

One astronomer has found that the habitable zone around some smaller stars is smaller than first calculated because of tidal heating.

9:45 am

One astronomer has found that the inner edge of the habitable zone around some dwarf stars is smaller than first calculated because tidal forces overheat planets close to the star.

Then again, this heating might expand the habitable zone in other directions. Stars might overheat when close to the star, but get a boost of needed heat when they would normally be too far away.

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Astronomers now believe that Type 1a supernovae — used to discover dark energy — can be produced in two different ways.

9:52 am

The uncertainty of science: Astronomers now believe that Type 1a supernovae — used to discover dark energy — can be produced in two different ways.

Type Ia supernovae are known to originate from white dwarfs – the dense cores of dead stars. White dwarfs are also called degenerate stars because they’re supported by quantum degeneracy pressure. In the single-degenerate model for a supernova, a white dwarf gathers material from a companion star until it reaches a tipping point where a runaway nuclear reaction begins and the star explodes. In the double-degenerate model, two white dwarfs merge and explode. Single-degenerate systems should have gas from the companion star around the supernova, while the double-degenerate systems will lack that gas.

For astronomers, this possibility raises several conflicting questions. If two different causes produce Type 1a supernovae, could their measurement of dark energy be suspect? And if not, why is it that these two different causes produce supernovae explosions that look so much alike?

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Scientists have discovered that the half life of one of their key isotopes for dating the solar system is 30% shorter than previously believed.

6:38 pm

The uncertainty of science: Scientists have discovered that the half life of one of their key isotopes for dating the age of the solar system is 30% shorter than previously believed.

The main result of the work of the international scientists, detailed in a recent article in Science, is a new determination of the half-life of 146Sm, previously adopted as 103 million years, to a much shorter value of 68 million years. The shorter half-life value, like a clock ticking faster, has the effect of shrinking the assessed chronology of events in the early solar system and in planetary differentiation into a shorter time span.

The new time scale, interestingly, is now consistent with a recent and precise dating made on a lunar rock and is in better agreement with the dating obtained with other chronometers. The measurement of the half-life of 146Sm, performed over several years by the collaborators, involved the use of the ATLAS particle accelerator at Argonne National Laboratory in Illinois.

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The Department of Energy has approved the start of detailed engineering for the Large Synoptic Survey Telescope.

5:36 pm

Ground-based astronomy moves forward: The Department of Energy has approved the start of detailed engineering for the camera on the Large Synoptic Survey Telescope.

I have to admit, I am puzzled why the Department of Energy is involved in this. Government funding for ground-based telescopes normally comes from the National Science Foundation.

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Europe has decided to build a probe, dubbed JUICE, to study Ganymede, Callisto and Europa, Jupiter’s big icy moons.

5:31 pm

Europe has decided to build a probe to study Ganymede, Callisto and Europa, Jupiter’s big icy moons.

Known as JUICE, the Jupiter Icy Moons Explorer, the probe will enter orbit around the gas giant planet in 2030 for a series of flybys of Ganymede, Callisto and Europa. JUICE will brake into orbit around Ganymede, Jupiter’s largest moon, in 2032 for at least one year of close-up research.

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More problems for Dark Matter

9:29 am

Vast Polar Structure

A new study by astronomers has found a vast structure of satellite galaxies and star clusters aligned perpendicular to the Milky Way and extending outward above and below the galaxy’s nucleus by as much as a million light years.

In their effort to understand exactly what surrounds our Galaxy, the scientists used a range of sources from twentieth century photographic plates to images from the robotic telescope of the Sloan Deep Sky Survey. Using all these data they assembled a picture that includes bright ‘classical’ satellite galaxies, more recently detected fainter satellites and the younger globular clusters.

“Once we had completed our analysis, a new picture of our cosmic neighbourhood emerged”, says Pawlowski. The astronomers found that all the different objects are distributed in a plane at right angles to the galactic disk. The newly-discovered structure is huge, extending from as close as 33,000 light years to as far away as one million light years from the centre of the Galaxy.

An animation illustrating this galactic distribution is posted below the fold. You can read the actual preprint paper here.

The problem with this polar alignment with the Milky Way’s core is that the theories for explaining the distribution of dark matter do not predict it.
» Read more

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New data from a neutrino telescope in Antarctica had found that cosmic rays don’t come from gamma ray bursts, as had been believed by astronomers.

9:43 pm

The uncertainty of science: New data from a neutrino telescope in Antarctica has found that cosmic rays don’t come from gamma ray bursts, as had been believed by astronomers. You can read the paper here. [pdf]

Which means that astronomers at this moment have no idea what produces these high energy cosmic rays.

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Dark matter disappears

9:15 am

The uncertainty of science: A new study has found no evidence of dark matter within 13,000 light years of the Sun, something that had not been expected.

According to widely accepted theories, the solar neighborhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

These findings will be as controversial as the now abandoned faster-than-light neutrino results last fall. Here, however, the new data is likely going to be more robust, which will cause the entire astrophysical community some real conniptions.
» Read more

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Astronomers have identified two of the oldest known stars, about 12 billion years old, both only a hundred light years away.

4:19 pm

Astronomers have identified two of the oldest known stars, about 12 billion years old, both only a hundred light years away.

What is intriguing about this discovery is that these two white dwarfs had to have formed very soon after the Big Bang, long before the Milky Way galaxy existed as we know it today. How they ended up here is an interesting puzzle.

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The Giant Magellan Telescope project has decided it will not participate in a funding competition offered by the National Science Foundation.

8:49 am

The 24.5 meter Giant Magellan Telescope project (GMT) has decided it is not interested in competing for funds offered by the National Science Foundation (NSF).

With just US$1.25 million available to the winner, the NSF competition was less about money and more about prestige. The NSF has been adamant that it has no significant money to support either project until the early part of next decade. But the Thirty Meter Telescope, which will still respond to the NSF’s solicitation, believed that a competition would at least demonstrate the NSF’s intention to eventually support one project — and that the winner would have an easier time attracting international partners.

But the GMT says it can go it alone, at least for now. On 23 March, the group began blasting at its mountaintop site in Chile. And they say they are nearly halfway towards raising the $700 million they need to complete construction.

If the GMT has already raised almost $350 million without NSF support, it makes perfect sense for them to thumb their noses at this piddling funding from the NSF, especially since the bureaucratic cost of getting that money will probably be far more than $1.25 million.

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NASA management yesterday extended funding for almost all of its on-going astrophysics missions, including Hubble, Kepler, Chandra, and Fermi.

8:37 am

NASA management yesterday extended funding for all but one of its on-going astrophysics missions, including Hubble, Kepler, Chandra, and Fermi.

According to a statement from NASA headquarters, all missions will continue in fiscal years 2013 and 2014. The guest observer programme for the Chandra X-ray Observatory would even be augmented. Only Spitzer, an infrared telescope, would be phased out earlier than the mission wanted, in 2015.

There is some justification for ending Spitzer’s funding early, as the spacecraft’s cameras have lost their ability to stay as cold as designed to do their full range of infrared observations.

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If there is water ice on the Moon, scientists have found that the bombardment from interstellar cosmic rays has likely caused chemical reactions that “can create complex carbon chains similar to those that help form the foundations of biological structures.”

9:11 am

Life stranger than science fiction: If there is water ice on the Moon, scientists have found that the bombardment from interstellar cosmic rays has likely caused chemical reactions that “can create complex carbon chains similar to those that help form the foundations of biological structures.”

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The orbit of a 150 foot wide asteroid that zipped past the Earth in February, has an orbit so much like the Earth’s that astronomer’s expect it back next year.

7:42 pm

Duck! The orbit of a 150 foot wide asteroid that zipped past the Earth in February, has an orbit that will bring it past the Earth again on February 15, 2013 by less than 15,000 miles.

The team use several automated telescopes to scan the sky, and the discovery came somewhat serendipitously after they decided to search areas of the sky where asteroids are not usually seen. “A preliminary orbit calculation shows that 2012 DA14 has a very Earth-like orbit with a period of 366.24 days, just one more day than our terrestrial year, and it ‘jumps’ inside and outside of the path of Earth two times per year,” says Jaime.

While an impact with Earth has been ruled out on the asteroid’s next visit, astronomers will use that close approach for more studies and calculate the Earth and Moon’s gravitational effects on it.

Because this newly discovered asteroid passes so close and frequently to both the Earth and Moon, astronomers will need a lot more data before they can pin down its orbit precisely, and thus predict the chances of a collision in the near future.

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The blistering hot exoplanet where it snows

4:13 pm

The blistering hot exoplanet where it snows.

These results have led to a suggestion that [HD 189733b] could continually experience silicate snow. In the lower atmosphere of [the exoplanet], magnesium silicate sublimates, that is, it passes directly from a solid into a gas. But we know there are small silicate particulates in the upper atmosphere. Formation of these particulates requires that the temperature be lowered, and so must have been formed at a temperature inversion in the atmosphere. The generally windy conditions would help some of the tiny particulates grow into respectable snow crystals.

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smaller planets are preferentially found in low-eccentricity orbits.

9:24 am

More Kepler results: From the abstract of a preprint paper published today on the Los Alamos astro-ph website:

The mean eccentricity of the Kepler candidates decreases with decreasing planet size indicating that smaller planets are preferentially found in low-eccentricity orbits.

In other words, the smaller a planet is, the more likely its orbit will be circular like the Earth’s. This result is encouraging news for the search for life on other worlds. Before Kepler, astronomers had found that the orbits of most exoplanets were far more eccentric than the orbits of the planets in our solar system, a condition that scientists thought was unfriendly for the development of life. These new results counter that conclusion. The orbits of the planets in our solar system might not be as unusual as first thought.

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