The Space Show this week – Mar.23.15

March 23, 2015 TopSpacer

Guests and topics of discussion on The Space Show this week:

1. Monday, March 23, 2015: 2-3:30 PM PDT (5-6:30 PM EDT; 4-5:30 PM CDT): We welcome DR. ARMIN ELLIS to the program to discuss the upcoming Exploration Institute 2015 Summit. The Summit will be held at Cal Tech in Pasadena, CA April 14-15, 2015. Dr. Ellis, formerly with JPL, will also discuss the Exploration Institute. See exploration.institute for more information.

2. Tuesday, March 24,, 2015:,7-8:30 PM PDT (10-11:30 PM EST, 9-10:30 PM CDT): We welcome back BOB ZIMMERMAN. Bob will update us on space happenings, news, events, and more. Check out his website, www.behindtheblack.com.

3. Friday, March 27, 2015; 9:30 -11 AM PDT (12:30-2 PM EDT; 11:30-1 PM CDT): We welcome to the show DR. PAMELA RAI MENGES of Aerospace Research Systems and The Space Power Laboratory. She will discuss their design of the first modular horizontal take off and horizontal landing (HTHL) commercial orbital spaceplane and more. Visit her company website for more information, www.arsispace.com.

4. Sunday, March 29, 2015: 12-1:30 PM PDT (3-4:30 PM EDT, 2-3:30 PM CDT): Welcome to OPEN LINES. First time callers welcome, all space and STEM calls welcome.

See also:
/– The Space Show on Vimeo – webinar videos
/– The Space Show’s Blog – summaries of interviews.
/– The Space Show Classroom Blog – tutorial programs

The Space Show is a project of the One Giant Leap Foundation.

Astronomy

Odd nova of 1670 now explained as collision of two stars

March 23, 2015 TopSpacer

A new report from the European Southern Observatory (ESO):

Colliding Stars Explain Enigmatic Seventeenth Century Explosion
APEX observations help unravel mystery of Nova Vulpeculae 1670

New observations made with APEX and other telescopes reveal that the star that European astronomers saw appear in the sky in 1670 was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later. The results appear online in the journal Nature on 23 March 2015.

The nova of 1670 recorded by Hevelius

Some of seventeenth century’s greatest astronomers, including Hevelius — the father of lunar cartography — and Cassini, carefully documented the appearance of a new star in the skies in 1670. Hevelius described it as nova sub capite Cygni — a new star below the head of the Swan — but astronomers now know it by the name Nova Vulpeculae 1670 [1]. Historical accounts of novae are rare and of great interest to modern astronomers. Nova Vul 1670 is claimed to be both the oldest recorded nova and the faintest nova when later recovered.

The lead author of the new study, Tomasz Kamiński (ESO and the Max Planck Institute for Radio Astronomy, Bonn, Germany) explains: “For many years this object was thought to be a nova, but the more it was studied the less it looked like an ordinary nova — or indeed any other kind of exploding star.”

When it first appeared, Nova Vul 1670 was easily visible with the naked eye and varied in brightness over the course of two years. It then disappeared and reappeared twice before vanishing for good. Although well documented for its time, the intrepid astronomers of the day lacked the equipment needed to solve the riddle of the apparent nova’s peculiar performance.

The remnant of the nova of 1670 seen with modern instruments

During the twentieth century, astronomers came to understand that most novae could be explained by the runaway explosive behaviour of close binary stars. But Nova Vul 1670 did not fit this model well at all and remained a mystery.

Even with ever-increasing telescopic power, the event was believed for a long time to have left no trace, and it was not until the 1980s that a team of astronomers detected a faint nebula surrounding the suspected location of what was left of the star. While these observations offered a tantalising link to the sighting of 1670, they failed to shed any new light on the true nature of the event witnessed over the skies of Europe over three hundred years ago.

Tomasz Kamiński continues the story: “We have now probed the area with submillimetre and radio wavelengths. We have found that the surroundings of the remnant are bathed in a cool gas rich in molecules, with a very unusual chemical composition.”

As well as APEX, the team also used the Submillimeter Array (SMA) and the Effelsberg radio telescope to discover the chemical composition and measure the ratios of different isotopes in the gas. Together, this created an extremely detailed account of the makeup of the area, which allowed an evaluation of where this material might have come from.

This wide-field view shows the sky around the location of the historical
exploding star Nova Vul 1670. The remains of the nova are only very
faintly visible at the centre of this picture.

What the team discovered was that the mass of the cool material was too great to be the product of a nova explosion, and in addition the isotope ratios the team measured around Nova Vul 1670 were different to those expected from a nova. But if it wasn’t a nova, then what was it?

The answer is a spectacular collision between two stars, more brilliant than a nova, but less so than a supernova, which produces something called a red transient. These are a very rare events in which stars explode due to a merger with another star, spewing material from the stellar interiors into space, eventually leaving behind only a faint remnant embedded in a cool environment, rich in molecules and dust. This newly recognised class of eruptive stars fits the profile of Nova Vul 1670 almost exactly.

Co-author Karl Menten (Max Planck Institute for Radio Astronomy, Bonn, Germany) concludes: “This kind of discovery is the most fun: something that is completely unexpected!”

Zooming in on the location of Nova Vul 1670 in the constellation of Vulpecula

Exoplanets, Space Systems

TESS will hunt for exoplanets starting in 2017

March 22, 2015 TopSpacer

The Kepler space observatory proved the effectiveness of the transit technique in finding exoplanets. After losing one reaction wheel too many, it was assumed that Kepler was an ex-exoplanet finder. However, the clever Kepler scientists and engineers found a way to use solar radiation pressure to keep the telescope steady in its viewing of distant stars. Now renamed the Kepler K2 mission, the observatory continues its planet spotting, albeit less efficiently than before.

So Kepler keeps adding to the list of exoplanets for now but a whole new improved exoplanet hunter is expected to go to space in August 2017. TESS (Transiting Exoplanet Survey Satellite) will monitor more stars than Kepler and it should also do better at finding small planets, i.e. earth-sized ones, orbiting around them. TESS will monitor

the brightnesses of more than 500,000 stars during a two year mission, searching for temporary drops in brightness caused by planetary transits. Transits occur when a planet’s orbit carries it directly in front of its parent star as viewed from Earth. TESS is expected to catalog more than 3000 transiting exoplanet candidates, including a sample of ∼500 Earth-sized and ‘Super Earth’ planets, with radii less than twice that of the Earth. TESS will detect small rock-and-ice planets orbiting a diverse range of stellar types and covering a wide span of orbital periods, including rocky worlds in the habitable zones of their host stars.

Here’s a video overview of the project:

We can also hope it has much better and more numerous reaction wheels…

Living in Space, Space Settlement, The Moon

Estimating the safety of Moon tunnels + The in-space colony concept

March 21, 2015 TopSpacer

A group at Purdue University has released an interesting study of lava tubes on the Moon in which they examined the possibility that there are ones big enough and stable enough to hold cities:

This diagram illustrates a lava tube protecting a city the size
of Philadelphia. Purdue University/courtesy of David Blair

Lava tubes are

tunnels formed from the lava flow of volcanic eruptions. The edges of the lava cool as it flows to form a pipe-like crust around the flowing river of lava. When the eruption ends and the lava flow stops, the pipe drains leave behind a hollow tunnel, said Jay Melosh, a Purdue University distinguished professor of earth, atmospheric and planetary sciences who is involved in the research.

There is indirect evidence that lava tubes exist on the Moon. A number of large holes, for example, have been seen on the Moon and it is speculated that these could be where the roofs of lava tubes have collapsed. See Lunar and Martian Lava Tube: Exploration as Part of an Overall Scientific Survey, Daga et al. (pdf).

The Purdue study considered the case of really large tubes:

David Blair, a graduate student in Purdue’s Department of Earth, Atmospheric and Planetary Sciences, led the study that examined whether empty lava tubes more than 1 kilometer wide could remain structurally stable on the moon.

“We found that if lunar lava tubes existed with a strong arched shape like those on Earth, they would be stable at sizes up to 5,000 meters, or several miles wide, on the moon,” Blair said. “This wouldn’t be possible on Earth, but gravity is much lower on the moon and lunar rock doesn’t have to withstand the same weathering and erosion. In theory, huge lava tubes – big enough to easily house a city – could be structurally sound on the moon.”

Blair worked with Antonio Bobet, a Purdue professor of civil engineering, and applied known information about lunar rock and the moon’s environment to civil engineering technology used to design tunnels on Earth.

The team found that a lava tube’s stability depended on the width, roof thickness and the stress state of the cooled lava, and the team modeled a range of these variables. The researchers also modeled lava tubes with walls created by lava placed in one thick layer and with lava placed in many thin layers, Blair said.

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Personally, rather than on the Moon I would prefer to live in a large, island-sized, in-space habitat like that promoted by the late Princeton physics professor Gerard K. O’Neill . Rotation could provide a full 1 g of spin-gravity, no lunar dust to hassle with and breath, sunlight all around, and there would be a greater sense of freedom of movement. That is, why work so hard to get out of earth’s gravity well just to jump down another one?

Every so often, someone on the web discovers the great space colony artwork from the workshops that studied such structures: How we’ll live in space, according to people in the 1970s – mashable

[]
Interior including human powered flight. Art work: Rick Guidice.
Image via NASA Ames Research Center.

At the time, such ambitions were believed justified by the big drop in space transportation costs that would come when the Space Shuttle began to fly. The Moon would still be useful – as a source of the materials to build such huge structures. It’s low gravity would allow building materials literally to be thrown into space by mass drivers, i.e. electromagnetic catapults.

Unfortunately, the hyper-complex and fragile Shuttles failed to lower space transport costs at all. The original fully reusable design for the Shuttles was down-graded by budget cuts and the Shuttles became only partially refurbish-able, requiring a standing army of thousands to work for months to return one to flight.

Today we finally are seeing new approaches to reusable space vehicles that intend to achieve full reusability and fast turnaround. We could see the cost of getting to space drop by factors of 100 in the coming decade.

Low cost spaceflight combined with new technologies like 3D printing and advanced robotics will make it affordable to build large scale structures in space. Today’s space pessimism towards concepts like in-space colonies will give way to taking them granted just as we take granted the giant structures on earth that once would have been considered fantasies.