Podcaster: Morgan Rehnberg
Next Year: www.cosmicchatter.org
Constants of nature:
Description: We bid GRAIL farewell while Akatsuki tries for a new lease on life. One mystery is solved while another is averted.
Bio: Morgan Rehnberg is a graduate student at the University of Colorado – Boulder, where he studies the rings of Saturn under the direction of Dr. Larry Esposito. Morgan received his B.S. in Physics from Beloit College and is the developer of the PhAst software package for the viewing and manipulating of astronomical images
Today’s Sponsor: “This episode of 365 days of astronomy was sponsored by Cheap Astronomy”
Additional sponsor by Clear Skies Observing Guides, a Modern Day Celestial Handbook. www.clearskies.eu ..Clear skies observing guides, or CSOG, is a new concept in visual amateur astronomy. The observing guides contain thousands of objects to observe through amateur telescopes, with matching tours for GOTO telescopes and matching AstroPlanner plan-files. CSOG allows you to target deep-sky objects and carbon stars you never observed before, night after night. Wishing astronomers around the world: Clear skies..! ”
You’re listening to the final episode of the 365 Days of Astronomy podcast. I’m Morgan Rehnberg and this is the Monthly News Roundup for December 2012. This episode was recorded December 28th from York, Pennsylvania. The Monthly News Roundup will air in 2013 at www.cosmicchatter.org.
Let’s begin this month with the end of a successful mission. Last week, the twin spacecraft which comprised the GRAIL mission were deliberately crashed into the lunar surface by mission controllers. NASA leaders had decided that a controlled crash was preferable to one in which an Apollo landing site or other lunar artifact could be destroyed. In honor of the late astronaut, the crash site was formally named the Sally K. Ride Impact Site on December 18th.
The GRAIL mission, which stands for Gravity Recovery and Interior Laboratory, was designed to map the gravitational field generated by the Moon. It consisted of two spacecraft, named Ebb and Flow, which flew in formation with each other in orbit around the Moon. As they traveled around the Moon, each measured their distance from the other probe to an accuracy of one micron, or about half the width of a human hair. As the pair encountered changes in the gravitational field created by the Moon, their separation would change slightly, allowing very precise measurements of this change in gravity.
Once a gravitational map was created, scientists could use the law of gravity to transform it into a map of the interior of the Moon. Places with as higher density would contain more material which, in turn, would exert a stronger gravitational pull on the spacecraft.
Studying the internal structure of the Moon is important for both the understanding of the Moon’s origin and future exploration of it. If we are to begin building larger and more-complex infrastructure on and around the Moon, detailed information about its gravity will help refine the orbits of future satellites and other structures. Knowledge of how the Moon’s interior compares to that of the Earth will help us understand the processes that must have occurred during both the formation of the Moon and the Earth.
As one mission ends, another is getting a new lease on life. Barely two years after a mechanical breakdown caused the Akatsuki spacecraft to fail its orbital insertion around Venus, engineers suggest that another attempt at the maneuver may be possible in 2015. While crippled, the spacecraft whose name means ‘Dawn’ in Japanese, will hopefully be able to carry out some of its science goals.
Spacecraft travelling between planets do so while in orbit about the Sun. When they arrive at their destination, the probe must fire its main rocket to match speeds with the planet to be studied. This maneuver, called orbital insertion, generally requires a substantial change in velocity. When Akatsuki’s main engine malfunctioned, the proper speed was not attained and orbital insertion could not be completed.
With it’s main rocket now dead, the team must use smaller maneuvering thrusters in a series of controlled burns which will place the spacecraft on a trajectory to eventually meet up with Venus. The unprecedented maneuver, however, will take the probe dangerously close to the Sun, where critical components could overheat and further complicate a second try. Scientists, though, have nothing to lose and everything to gain from resurrecting an otherwise dead mission.
If Akatsuki does manage to gain Venusian orbit, it will study the planet’s surface using a suite of six instruments, including five cameras. Imagers in the visible spectrum will look to capture evidence of lightning in the dense clouds which obscure the surface of Venus, while instruments in the infrared and ultraviolet will study the distribution of elements in the planet’s atmosphere. Unfortunately, the use of maneuvering thrusters to save the spacecraft may severely limit it’s capabilities upon arrival. Despite this, Akatsuki is poised to expand our understanding of the second planet.
From the planets, let’s move to the Sun. In a paper published this month in the journal Nature, a group of physicists claim to have solved a long-standing problem in solar observation. They suggest that what has seemed like an error in modern observations of the Sun may, in fact, be a flaw in the underlying physics.
In its simplest form, the Sun can be thought of as a huge ball of hydrogen, the simplest element. Hydrogen is burned at the center of all stars through the process of nuclear fusion. Fusion combines hydrogen into helium, which is then combined in various ways to produce all the common elements: carbon, oxygen, nitrogen, etc. At each step along the way energy is released, which eventually becomes the light we see during the day. This element combination continues until iron is formed. Iron no longer releases more energy than it takes to form, so the process more or less stops, and iron accumulates at the center of the Sun. This iron, like all other elements, releases light at specific wavelengths, called lines.
One of those lines, in the x-ray part of the spectrum, is predicted to be far brighter than is actually observed. Stars are quite dense, so the general assumption was that these particular bits of light were being absorbed by something else before they could reach the surface. The theoretical predictions which underlie this have been difficult to test, however, because conditions inside the Sun are challenging to recreate in the laboratory. This most-recent work has made major strides in re-creating these conditions and the scientists find that the expected x-rays are still missing.
In the laboratory, there is nothing to absorb them, so the iron must simply not be emitting the expected light. This suggests that in the extreme conditions inside of stars, our understanding of quantum mechanics – the theory which describes atoms – must be incomplete. Hopefully further work in this area will begin to account for the surprising case of the missing photons.
Finally this month, some good news from the field of cosmology. One of the fundamental assumptions of all science is that the laws of nature act the same everywhere and have done so for all time. Vital to this are the constants of nature: quantities such as the fundamental amount of electric charge, the smallest unit is energy, or the speed of light. Recent observations of the galaxy PKS 1830-211 have shown that another such constant – the ratio of the masses of protons and electrons – is also fixed.
The ratio between the mass of a proton and the much-smaller electron has been measured here on Earth to be approximately 1836. That is, a proton is nearly two thousand times larger than the electron which orbits it. This fact may seem unremarkable, but many fundamental quantities in physics, such as energy and momentum, are dependant on mass. A small deviation in this ratio would mean a dramatic alteration of the physical properties of the atom, the building block of macroscopic matter. If such a change had, in fact, occurred, it would mean that we could not apply our knowledge of physics today to understand what must have happened in the early universe.
Fortunately, measurements of this galaxy seven-billion lightyears away have shown that the proton-to-electron mass ratio has deviated by no more than one part in ten million, which corresponds to the error of the experiment. To determine this, astronomers observed light emitted by the methanol molecule, better known here on Earth as a constituent of alcohol. Astronomers measured the differences between certain spectral lines, or patterns of emitted light, to determine if they mirrored those created by methanol in the laboratory. Changes in the fine-scale structure of the molecule would have resulted in a different pattern of photons, but this was not observed.
Although virtually all physicists would have predicted this outcome from the experiment, such confirmation is vital to the scientific process. If, instead, it turned out that a change *had* occurred and we had not looked for it, many years of research could have been rendered incorrect.
Thanks for listening to this episode of the Monthly News Roundup. Since the 365 Days of Astronomy podcast is shutting down, the Monthly News Roundup will continue to air at www.cosmicchatter.org. You can find Cosmic Chatter on iTunes or follow @cosmic_chatter on Twitter for more information. As always, I welcome your comments and corrections. You can email me at firstname.lastname@example.org. Happy New Year!
End of podcast:
365 Days of Astronomy
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