Skip navigation

Monthly Archives: January 2014

Our Solar System seems like a neat and orderly place, with small, rocky worlds near the Sun and big, gaseous worlds farther out, all eight planets following orbital paths unchanged since they formed. However, the true history of the Solar System is far more riotous. Giant planets migrated in and out, tossing interplanetary flotsam and jetsam far and wide.

New clues to this tumultuous past come from the asteroid belt. Millions of asteroids circle the Sun between the orbits of Mars and Jupiter, in a region known as the main asteroid belt. Traditionally, they were viewed as the pieces of a failed planet that was prevented from forming by the influence of Jupiter’s powerful gravity. Their compositions seemed to vary methodically from drier to wetter, due to the drop in temperature as you move away from the Sun.

base

Credit: David A. Aguilar (CfA)

This traditional view has changed, as astronomers have recognized that the current residents of the main asteroid belt weren’t all there from the start. In the early history of the Solar System the giant planets ran amok, migrating inward and outward substantially. Jupiter may have moved as close to the Sun as Mars is now. In the process, it swept the asteroid belt nearly clean, leaving only a tenth of one percent of its original population. As the planets migrated, they stirred the contents of the Solar System. Objects from as close to the Sun as Mercury, and as far out as Neptune, all collected in the main asteroid belt.

Using data from the Sloan Digital Sky Survey, astronomers have examined the compositions of thousands of asteroids within the main belt. They found that the asteroid belt is more diverse than previously realized, especially when you look at the smaller asteroids. This finding has interesting implications for the history of Earth. Astronomers have theorized that long-ago asteroid impacts delivered much of the water now filling Earth’s oceans. If true, the stirring provided by migrating planets may have been essential to bringing those asteroids.

This raises the question of whether an Earth-like exoplanet would also require a rain of asteroids to bring water and make it habitable. If so, then Earth-like worlds might be rarer than we thought.  The paper describing these findings appears in the January 30, 2014 issue of Nature.

Links: Harvard-Smithsonian Center for Astrophysics press release; Nature article.

An exceptionally close supernova (a stellar explosion, see Section 13.2, p. 337) discovered on January 21, 2014, has become the focus of observatories around the globe, as well as a suite of orbiting spacecraft. The blast, designated SN 2014J, occurred in the bright galaxy M82 and lies about 12 million light-years away. This makes it the nearest optical supernova in two decades and potentially the closest type Ia supernova to occur during the life of currently operating space missions.

Credit and copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona.

SN 2014J was first spotted as an unfamiliar source in the otherwise familiar galaxy by teaching fellow Steve Fossey and astronomy workshop students Ben Cooke, Tom Wright, Matthew Wilde, and Guy Pollack at the University College London Observatory on the evening of January 21.

To capitalize on this unusual event, astronomers have planned observations with the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Gamma-ray Space Telescope, and Swift missions.

Links: Further information from the NASA press release; hi-res image from APOD January 24, 2014.

Stream or listen to the podcast of the most recent Planetary Radio show from The Planetary Society to hear authors Jay M. Pasachoff and Alex Filippenko talk about “The Cosmos”, Fourth Edition, among other topics.

index

Links: Planetary Radio show, January 21, 2014.

This spring, NASA officials will conduct a review of the spacecraft that have outlived their original missions. For the 2015 fiscal year, which begins October 1, the agency faces particularly tough choices, in order to balance their books.

A decade after swinging into orbit around Saturn, the venerable Cassini spacecraft is still working, well beyond the four years of science the space agency had hoped to get. But the spacecraft is running low on maneuvering fuel, and its managers want to end with a scientific bang – an ambitious agenda that includes 22 orbits through a gap between the planet and its innermost ring before sending the craft on a death plunge into Saturn in 2017. For several months, however, scientists have worried that NASA, financially squeezed like the rest of the federal government, could terminate the mission sooner.

Credit: NASA/JPL/Space Science Institute

The Mars rover Curiosity, which will cost $68 million this year to operate, will complete its two-year primary mission in June 2014, so money for continued roving will come out of funds dedicated to “extended missions.” For this year, that amount is $140 million, which includes $58 million for Cassini. Other extended missions include the Messenger spacecraft at Mercury, the Mars rover Opportunity, and the Mars Reconnaissance Orbiter.

No one expects NASA to turn off Curiosity, which will not even arrive at its primary science destination until later this year, raising concerns that Cassini may be on the chopping block. More recently, NASA planetary science director James Green told scientists that the perception of Cassini versus Curiosity was inaccurate and that officials could instead scale back the cost and scope of the extended missions. The agency could also juggle other money to pay for both Cassini and Curiosity, but that could have consequences like delaying future missions, which themselves are under pressure to deliver the maximum scientific benefits for a smaller cost.

Links and source: NY Times op-ed by Kenneth Chang.

Astronomers have discovered a distant quasar illuminating a vast nebula of diffuse gas, revealing for the first time part of the network of filaments thought to connect galaxies in a cosmic ‘web’. Researchers at the University of California, Santa Cruz, led the study, published January 19 in the journal, Nature. Using the 10-meter Keck I telescope in Hawaii, the researchers detected a very large, luminous nebula of gas extending about 2 million light-years across intergalactic space.

_72397147_72395239

Credit: S. Cantalupo (UCSC); Joel Primack (UCSC); Anatoly Klypin (NMSU)

The standard cosmological model of structure formation in the Universe predicts that galaxies are embedded in a cosmic web of matter, most of which (about 84 percent) is invisible dark matter. This web is seen in the results from computer simulations of the evolution of structure in the Universe, which show the distribution of dark matter on large scales, including the dark matter halos in which galaxies form and the cosmic web of filaments that connect them. Gravity causes ordinary matter to follow the distribution of dark matter, so filaments of diffuse, ionized gas are expected to trace a pattern similar to that seen in dark matter simulations.

Until now, these filaments have never been seen. Intergalactic gas has been detected by its absorption of light from bright background sources, but those results don’t reveal how the gas is distributed. In this study, the researchers detected the fluorescent glow of hydrogen gas resulting from its illumination by intense radiation from the quasar.

The hydrogen gas illuminated by the quasar emits ultraviolet light known as Lyman alpha radiation. The distance to the quasar is so great (about 10 billion light-years) that the emitted light is “stretched” by the expansion of the Universe from an invisible ultraviolet wavelength to a visible shade of violet by the time it reaches the Keck telescope and the spectrometer used for this discovery. Knowing the distance to the quasar, the researchers calculated the wavelength for Lyman alpha radiation from that distance and built a special filter to get an image at that wavelength.

Links: further images and information via the full Keck Observatory press release.

The Sloan Digital Sky Survey (SDSS) is one of the most ambitious and influential surveys in the history of astronomy. Over eight years of operations it has obtained deep, multi-color images covering more than a quarter of the sky and created 3-dimensional maps containing more than 930,000 galaxies and more than 120,000 quasars.

Credit: Sloan Digital Sky Survey

The education team at SDSS have prepared a variety of astronomical resources, interactive tools, and science projects, for teachers and educators to use. They aim to show us the beauty of the Universe, and share with us their excitement as they build the largest map in the history of the world!

SkyServer‘s tools allow you to access all publicly available data from the Sloan Digital Sky Survey. It offers access to many different types of data, but most users will usually focus on four types: images, spectra, photometric data, and spectroscopic data. See their ‘Getting Started‘ page for more details.

Their projects pages come in both Basic (suitable for high-school and Astronomy 101-level students) and Advanced (for students with a deeper understanding of astronomy) levels.  There are also ideas for extended independent research projects.

Instructor guides are also available.

On p. 25, Figure It Out 2.3, the last paragraph (about Joseph Fraunhofer) belongs at the end of the caption of Figure 2-4 on p. 26.
The paragraph says: “Note that Fraunhofer labelled lines with letters from A through H and then used I for the end of the spectrum.  Though most scientists don’t realize it, the K line of ionized calcium so often referred to in astronomy as a Fraunhofer line wasn’t given its notation until the mid-nineteenth century.”

The innermost moon of Mars, Phobos, is seen in a new 40-second movie in full 360-degree glory. The images were taken by the High Resolution Stereo Camera (HRSC) on ESA’s Mars Express orbiter at various times throughout the mission’s 10 years.

Credit: ESA/DLR/FU Berlin (G. Neukum)

The moon’s parallel sets of grooves are perhaps the most striking feature, along with the giant 9 km-wide Stickney impact crater that dominates one face of the 27 x 22 x 18 km moon. The origin of the moon’s grooves is a subject of much debate. One idea assumes that the crater chains are associated with impact events on the moon itself. Another idea suggests they result from Phobos moving through streams of debris thrown up from impacts 6000 km away on the surface of Mars, with each ‘family’ of grooves corresponding to a different impact event.

Mars Express has imaged Phobos from a wide range of distances, but made its closest flyby yet on December 29, 2013, at just 45 km above the moon. Although this is too close to take images, gravity experiments will give insight into the interior structure of Phobos.

Links: ESA movie; Phobos overview and gallery from NASA.

297755main

Credit: Bill Anders/NASA

To commemorate the 45th anniversary of Apollo 8, the first manned mission to orbit the Moon, a new computer-generated visualization has been released to tell the story of one of space’s most famous images. The movie uses high-precision data from NASA’s Lunar Reconnaissance Orbiter, LRO, to accurately recreate the event.

Links: NPR article and interview with the movie’s narrator Andrew Chaikin; NASA press release.