Weekly Space Hangout – Mar 17, 2017: Stuart McNeill of the Intrepid Sea, Air & Space Museum

Host: Fraser Cain (@fcain)

Special Guest:
Stuart McNeill is the the Community Engagement specialist in charge of Family Programs and Demonstrations at the Intrepid Sea, Air & Space Museum. Check out their membership site here.

Guests:
Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )
Paul M. Sutter (pmsutter.com / @PaulMattSutter)

Their stories this week:

The original weird star: Przybylski’s Star may contain short-lived isotopes

Enceladus’ sub-surface ocean under thin(ner) ice

Star orbiting black hole at 1% c

We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

If you’d like to join Fraser and Paul Matt Sutter on their tour to Iceland in February, 2018, you can find the information at astrotouring.com.

If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site here and sign up!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page

Isotopes May One Day Aid In Planet Search

When we consider samples from the solar nebula, we think about comets and meteorites. These materials come from our solar system’s beginning, but the clues they give to formation don’t always mesh neatly. Thanks to a new study done by Carnegie’s Alan Boss, we’re now able to take a look at the Sun’s formation through a set of theoretical models. This work could not only help explain some of the differences we’ve discovered, but could also point to habitable exoplanets.

At the present time, a way to look back at the solar system’s early period is to theorize about tiny pockets of crystalline particles found in comets. These particles were forged at high temperatures. An alternate method of studying solar system formation is to analyze isotopes. These variants of elements carry the exact same number of protons, but contain a different number of neutrons. Unlike the crystalline particles, we can get our hands on samples of isotopes, because they are found in meteorites. As they decay, they turn into different elements. However, the initial number of isotopes can clue researchers as to their origin and how they might have journeyed across the neophyte solar system.

“Stars are surrounded by disks of rotating gas during the early stages of their lives.” says the Carnegie team. “Observations of young stars that still have these gas disks demonstrate that Sun-like stars undergo periodic bursts, lasting about 100 years each, during which mass is transferred from the disk to the young star.”

However, the study isn’t cut and dried just yet. The study of both particles and isotopes from comets and meteorites still present a somewhat confused look at early solar system formation. It would appear there’s more to the picture than just a single path of matter from the protoplanetary disk to the parent star. The crystalline grains found in comets are heat-formed and they signal that considerable mixing and outward flow occurred from materials close to the parent star and out to the perimeter of the system itself. Certain isotopes, such as aluminum, support this theory, but others, like oxygen, defy such a neat explanation.

According to the news release, Boss’ new model shows how a period of slight gravitational instability in the gas disk surrounding a proto-Sun about to go into an outburst phase, could account for these findings. What’s more, the models also predict this could happen with a wide variety of both mass and disk sizes. It shows that instability can “cause a relatively rapid transportation of matter between the star and the gas disk, where matter is moved both inward and outward. This accounts for the presence of heat-formed crystalline particles in comets from the solar system’s outer reaches.”

So what of aluminum? According to Boss’ model, the ratios of aluminum isotopes can be explained. It would appear the original isotope was imparted during a singular event – such as an exploding star sending a shock wave both inward and outward in the protoplanetary disk. As far as oxygen goes, it can be present in different pattern because it originated from sustained chemical reactions natural to the outer solar nebula and did not just happen as a singular event.

“These results not only teach us about the formation of our own solar system, but also could aid us in the search for other stars orbited by habitable planets,” Boss said. “Understanding the mixing and transport processes that occur around Sun-like stars could give us clues about which of their surrounding planets might have conditions similar to our own.”

Original Story Source: Carnegie Institution for Science Press Release

More Evidence That Mars Lost Its Atmosphere

Although today Mars’ atmosphere is sparse and thin — barely 1% the density of Earth’s at sea level — scientists don’t believe that was always the case. The Red Planet likely had a much denser atmosphere similar to ours, long, long ago. So… what happened to it?

NASA’s Curiosity rover has now found strong evidence that Mars lost much of its atmosphere to space — just as many scientists have suspected. The findings were announced today at the EGU 2013 General Assembly in Vienna.

Curiosity's SAM instrument (NASA/JPL-Caltech)
Curiosity’s SAM instrument (NASA/JPL-Caltech)

Curiosity’s microwave oven-sized Sample Analysis at Mars (SAM) instrument analyzed an atmosphere sample last week using a process that concentrates selected gases. The results provided the most precise measurements ever made of isotopes of argon in the Martian atmosphere.

Isotopes are variants of the same element with different atomic weights.

“We found arguably the clearest and most robust signature of atmospheric loss on Mars,” said Sushil Atreya, a SAM co-investigator at the University of Michigan.

SAM found that the Martian atmosphere has about four times as much of a lighter stable isotope (argon-36) compared to a heavier one (argon-38). This ratio is much lower than the Solar System’s original ratio, as estimated from measurements of the Sun and Jupiter.

The argon isotope fractionation provides clear evidence of the loss of atmosphere from Mars. (NASA/JPL)
The argon isotope fractionation provides clear evidence of the loss of atmosphere from Mars. (NASA/JPL)

This also removes previous uncertainty about the ratio in the Martian atmosphere in measurements from NASA’s Viking project in 1976, as well as from small volumes of argon extracted from Martian meteorites retrieved here on Earth.

These findings point to a process that favored loss of the lighter isotope over the heavier one, likely through gas escaping from the top of the atmosphere. This appears to be in line with a previously-suggested process called sputtering, by which atoms are knocked out of the upper atmosphere by energetic particles in the solar wind.

The solar wind may have helped strip Mars of its atmosphere over the course of many hundreds of millions of years (NASA)
The solar wind may have helped strip Mars of its atmosphere over the course of many hundreds of millions of years (NASA)

Lacking a strong magnetic field, Mars’ atmosphere would have been extremely susceptible to atmospheric erosion by sputtering billions of years ago, when the solar wind was an estimated 300 times the density it is today.

These findings by Curiosity and SAM will undoubtedly support those made by NASA’s upcoming MAVEN mission, which will determine how much of the Martian atmosphere has been lost over time by measuring the current rate of escape to space. Scheduled to launch in November, MAVEN will be the first mission devoted to understanding Mars’ upper atmosphere.

Find out more about MAVEN and how Mars may have lost its atmosphere in the video below, and follow the most recent discoveries of the MSL mission here.

Source: NASA/JPL

Did A Supernova Shape Our Solar System?

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Away in space some 4.57 billion years ago, in a galaxy yet to be called the Milky Way, a hydrogen molecular cloud collapsed. From it was born a G-type main sequence star and around it swirled a solar nebula which eventually gelled into a solar system. But just what caused the collapse of the molecular cloud? Astronomers have theorized it may have been triggered by a nearby supernova event… And now new computer modeling confirms that our Solar System was born from the ashes a dead star.

While this may seem like a cold case file, there are still some very active clues – one of which is the study of isoptopes contained within the structure of meteorites. As we are well aware, many meteorites could very well be bits of our primordial solar nebula, left virtually untouched since they formed. This means their isotopic signature could spell out the conditions that existed within the molecular cloud at the time of its collapse. One strong factor in this composition is the amount of aluminium-26 – an element with a radioactive half-life of 700,000 years. In effect, this means it only takes a relatively minor period of time for the ratio between Al-26 and Al-24 to change.

“The time-scale for the formation events of our Solar System can be derived from the decay products of radioactive elements found in meteorites. Short lived radionuclides (SLRs) such as 26Al , 41Ca, 53Mn and 60Fe can be employed as high-precision and high-resolution chronometers due to their short half-lives.” says M. Gritschneder (et al). “These SLRs are found in a wide variety of Solar System materials, including calcium-aluminium-rich inclusions (CAIs) in primitive chondrites.”

However, it would seem that a class of carbonaceous chondrite meteorites known CV-chondrites, have a bit more than their fair share of Al-26 in their structure. Is it the smoking gun of an event which may have enriched the cloud that formed it? Isotope measurements are also indicative of time – and here we have two examples of meteorites which formed within 20,000 years of each other – yet are significantly different. What could have caused the abundance of Al-26 and caused fast formation?

“The general picture we adopt here is that a certain amount of Al-26 is injected in the nascent solar nebula and then gets incorporated into the earliest formed CAIs as soon as the temperature drops below the condensation temperature of CAI minerals. Therefore, the CAIs found in chondrites represent the first known solid objects that crystalized within our Solar System and can be used as an anchor point to determine the formation time-scale of our Solar System.” explains Gritschneder. “The extremely small time-span together with the highly homogeneous mixing of isotopes poses a severe challenge for theoretical models on the formation of our Solar System. Various theoretical scenarios for the formation of the Solar System have been discussed. Shortly after the discovery of SLRs, it was proposed that they were injected by a nearby massive star. This can happen either via a supernova explosion or by the strong winds of a Wolf-Rayet star.”

While these two theories are great, only one problem remains… Distinguishing the difference between the two events. So Matthias Gritschneder of Peking University in Beijing and his colleagues set to work designing a computer simulation. Biased towards the supernova event, the model demonstrates what happens when a shockwave encounters a molecular cloud. The results are an appropriate proportion of Al-26 – and a resultant solar system formation.

“After discussing various scenarios including X-winds, AGB stars and Wolf-Rayet stars, we come to the conclusion that triggering the collapse of a cold cloud core by a nearby supernova is the most promising scenario. We then narrow down the vast parameter space by considering the pre-explosion survivability of such a clump as well as the cross-section necessary for sufficient enrichment.” says Gritschneder. “We employ numerical simulations to address the mixing of the radioactively enriched SN gas with the pre-existing gas and the forced collapse within 20 kyr. We show that a cold clump at a distance of 5 pc can be sufficiently enriched in Al-26 and triggered into collapse fast enough – within 18 kyr after encountering the supernova shock – for a range of different metallicities and progenitor masses, even if the enriched material is assumed to be distributed homogeneously in the entire supernova bubble. In summary, we show that the triggered collapse and formation of the Solar System as well as the required enrichment with radioactive 26Al are possible in this scenario.”

While there are still other isotope ratios yet to be explained and further modeling done, it’s a step toward the future understanding of how solar systems form.

Original Story Source: MIT Technology Review News Release. For Further Reading: The Supernova Triggered Formation And Enrichment Of Our Solar System.