Happy New Year spacefans! I hope you’ve all recovered from you holiday hangovers and appreciating the delights of January weather and the return to work! We have some intruiging things to show you!
ORIGIN OF MYSTERIOUS FAST RADIO BURST DISCOVERED
So what is a Fast Radio Burst? (FRBs) They are short-lived, powerful pulses of radio waves from accross the cosmos. Their brevity, combined with the fact that it’s difficult to pinpoint their location, have ensured their origins remain mysterious. Outlining their work at a major conference, astronomers say they have now traced the source of one of these bursts to a distant galaxy. It’s an important step to finally solving the mystery, which has spawned a variety of different possible explanations, from black holes to extra-terrestrial intelligence. The first FRB was discovered in 2007, in archived data from the Parkes Radio Telescope in Australia. Astronomers were searching for new examples of magnetised neutron stars called pulsars, but found a new phenomenon – a radio burst from 2001. Since then, 18 FRBs – also referred to as “flashes” or “sizzles” – have been found in total.
“I don’t exaggerate when I say there are more theories for what these could be than there are observed bursts,” first author of the new study, Shami Chatterjee, from Cornell University in Ithaca, New York, along with collegues.Unlike all the others, this FRB – discovered in 2012 – has recurred several times.
“When we reported last year that one of these objects was repeating, that – in one go – knocked out about half of those models, because for this one source, at least, we knew it couldn’t be explosive. It had to be something where the engine that produced this survived for the next flash.”
In 83 hours of observing time over six months in 2016, the VLA detected nine bursts from FRB 121102.
“We now know that this particular burst comes from a dwarf galaxy more than three billion light-years from Earth,” said Dr Chatterjee. That’s a staggering distance from Earth, underlining just how energetic these flashes are. “That simple fact is a huge advance in our understanding of these events.”
Dr Shriharsh Tendulkar, a member of the team from McGill University in Montreal, Canada, said: “Before we knew the distance to any FRBs, several proposed explanations for their origins said they could be coming from within or near our own Milky Way galaxy. We now have ruled out those explanations, at least for this FRB.” Adding to the mystery, the FRB appeared to be accompanied by a stream of ongoing, persistent weaker radio emissions. These emission sources have proven not to be more than 100 light years apart, but could in fact be from the same object or related in some other fashion.
The host galaxy is tiny. “We’re barely able to distinguish it from a star,” said Dr Tendulkar. It has roughly one one-thousandth of the stars as the Milky Way and is less than one-tenth as wide. “That’s weird,” he said. “One favored explanation for fast radio bursts is that they come from neutron stars, the dense cores left behind after a massive star explodes. But if neutron stars are responsible, then astronomers expect to find bursts in places with lots of stars”
Tracing FRB 121102 back to a dwarf galaxy doesn’t rule out neutron stars as a source. The gas in dwarf galaxies is more pristine than in other locales such as the Milky Way — with relatively low amounts of elements heavier than helium. Such gas makes it easier for massive stars to form. More heavyweight stars lead to more neutron stars, which could lead to more radio bursts.
“Finding the host galaxy of this FRB, and its distance, is a big step forward, but we still have much more to do before we fully understand what these things are.” said Dr Shami Chatterjee.
Now we go to the Moon, a topic very close to my heart over the last few months.
SOLAR STORMS COULD ELECTRIFY MOON SOILS
The Moon as we know has no magnetosphere of its own to protect it from the vagaries of space weather. Powerful solar storms can charge up the soil in frigid, permanently shadowed regions near the lunar poles, and may possibly produce “sparks” that could vaporize and melt the soil, perhaps as much as meteoroid impacts. This alteration may become evident when analyzing future samples from these regions that could hold the key to understanding the history of the moon and solar system. The moon has almost no atmosphere, so its surface is exposed to the harsh space environment. Impacts from small meteoroids constantly churn or “garden” the top layer of the dust and rock, called regolith, on the moon. “About 10 percent of this gardened layer has been melted or vaporized by meteoroid impacts,” said Andrew Jordan of the University of New Hampshire, Durham. “We found that in the moon’s permanently shadowed regions, sparks from solar storms could melt or vaporize a similar percentage.” Jordan is lead author of a paper on this research published online in Icarus August 31, 2016.
In August 2014, however, Jordan’s team published simulation results predicting that strong solar storms would cause the regolith in the moon’s permanently shadowed regions (PSRs) to accumulate charge in these two layers until explosively released, like a miniature lightning strike. The PSRs are so frigid that regolith becomes an extremely poor conductor of electricity. Therefore, during intense solar storms, the regolith is expected to dissipate the build-up of charge too slowly to avoid the destructive effects of a sudden electric discharge, called dielectric breakdown. The research estimates the extent that this process can alter the regolith.
“This process isn’t completely new to space science — electrostatic discharges can occur in any poorly conducting (dielectric) material exposed to intense space radiation, and is actually the leading cause of spacecraft anomalies,” said Timothy Stubbs of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, a co-author of the paper. The team’s analysis was based on this experience. From spacecraft studies and analysis of samples from NASA’s Apollo lunar missions, the researchers knew how often large solar storms occur. From previous lunar research, they estimated that the top millimeter of regolith would be buried by meteoroid impacts after about a million years, so it would be too deep to be subject to electric charging during solar storms. Then they estimated the energy that would be deposited over a million years by both meteoroid impacts and dielectric breakdown driven by solar storms, and found that each process releases enough energy to alter the regolith by a similar amount.
“Lab experiments show that dielectric breakdown is an explosive process on a tiny scale,” said Jordan. “During breakdown, channels could be melted and vaporized through the grains of soil. Some of the grains may even be blown apart by the tiny explosion. The PSRs are important locations on the moon, because they contain clues to the moon’s history, such as the role that easily vaporized material like water has played. But to decipher that history, we need to know in what ways PSRs are not pristine; that is, how they have been weathered by the space environment, including solar storms and meteoroid impacts.”
As you watch the Moon over the course of a month, you’ll notice that different features are illuminated by the Sun at different times. However, there are some parts of the Moon that never see sunlight. These areas are called permanently shadowed regions, and they appear dark because unlike on the Earth, the axis of the Moon is nearly perpendicular to the direction of the sun’s light. The result is that the bottoms of certain craters are never pointed toward the Sun, with some remaining dark for over two billion years. However, thanks to new data from NASA’s Lunar Reconnaissance Orbiter, we can now see into these dark craters in incredible detail. Credits: NASA Goddard/LRO mission
The next step is to search for evidence of dielectric breakdown in PSRs and determine if it could happen in other areas on the moon. Observations from NASA’s Lunar Reconnaissance Orbiter spacecraft indicate that the soil in PSRs is more porous or “fluffy” than other areas, which might be expected if breakdown was blasting apart some of the soil grains there. However, experiments, some already underway, are needed to confirm that breakdown is responsible for this. Also, the lunar night is long — about two weeks — so it can become cold enough for breakdown to occur in other areas on the moon, according to the team. There may even be “sparked” material in the Apollo samples, but the difficulty would be determining if this material was altered by breakdown or a meteoroid impact. The team is working with scientists at the Johns Hopkins University Applied Physics Laboratory on experiments to see how breakdown affects the regolith and to look for any tell-tale signatures that could distinguish it from the effects of meteoroid impacts.
Asteroids are going to be a main focus of mine for the next few months, so this personally gets me excited!
MISSION TO STUDY JUPITER’S ASTEROIDS
NASA has selected a mission that will perform the first close up look of the Trojans, a population of asteroids dating to very early in the Solar system’s past, orbiting in tandem with Jupiter. The Lucy mission will launch in 2021 to study six of these exciting worlds.
“This is a unique opportunity,” said Dr. Harold F. Levison, Lucy principal investigator from Southwest Research Institute (SwRI) in Boulder, Colorado. “Because the Trojans are remnants of the primordial material that formed the outer planets, they hold vital clues to deciphering the history of the solar system. Lucy, like the human fossil for which it is named, will revolutionize the understanding of our origins.”
The Lucy spacecraft and a remote-sensing instrument suite will study the geology, surface composition, and bulk physical properties of these bodies at close range. The payload includes three complementary imaging and mapping instruments, including a color imaging and infrared mapping spectrometer from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, a high-resolution visible imager from the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, and a thermal infrared spectrometer from Arizona State University, Tempe. In addition, Lucy will perform radio science investigations using its telecommunications system to determine the masses and densities of the Trojan targets.
“Understanding the causes of the differences between the Trojans will provide unique and critical knowledge of planetary origins, the source of volatiles and organics on the terrestrial planets, and the evolution of the planetary system as a whole,” said Dr. Catherine Olkin, the mission’s deputy principal investigator from SwRI.
“The Lucy mission is one of those rare moments where a single mission can have a major impact on our understanding of such fundamental questions,” added Dr. Keith Noll, Lucy project scientist from Goddard. The mission will launch in October 2021 and fly by its targets between 2025 and 2033. In all, Lucy will study six Trojans and one main belt asteroid. Southwest Research Institute (SwRI) in Boulder, Colorado is the principal investigator institution and will lead the science investigation. NASA’s Goddard Space Flight Center, Greenbelt, Maryland will provide overall mission management, systems engineering, and safety and mission assurance. Lockheed Martin Space Systems in Denver, Colorado will build the spacecraft.
Discovery Program class missions like these are reasonably cheap, their development capped at about $450 million. They are managed for NASA’s Planetary Science Division by the Planetary Missions Program Office at Marshall Space Flight Center in Huntsville, Alabama. The missions are designed and led by a principal investigator, who assembles a team of scientists and engineers, to address key science questions about the solar system.
See you next time space fans!