SOCIETY JOURNAL - Auckland Astronomical Society › Documents › Journal › aas... · Center for Astrophysics (CfA). "With solar twins we can study the past, pre-sent, and future

August 2014

SOCIETY JOURNAL August Meeting: Monday August 11th at 8:00pm

A New Way to Access Space:

The Development of a Low-cost Launch Vehicle in New Zealand

I n 2013 Dr Sandy Tirtey became the vehicle team lead for Electron, responsible for the design of all

structural elements, aerodynamics, and deployment systems in the launch vehicle.

Sandy joined Rocket Lab from the University of Queensland (UQ, Brisbane) where he was the Technical

Lead and Project Manager of the Scramspace I Scramjet propulsion free-flight experiment. Sandy man-

aged the project’s flight-team who, in cooperation with DSTO and 12 others international partners, suc-

cessfully built and flew the Scramspace I vehicle in September 2013. Sandy holds a PhD in Hypersonics

from The von Karman Institute for Fluid Dynamics (VKI, Belgium) for his work on the ESA EXPERT hyper-

sonic re-entry vehicle.

In July 2014 RocketLab announced that the company is developing a rocket called Electron, a carbon com-

posite rocket with a payload to orbit of 110 kilograms and a projected cost of less than US$5 million per

launch. As of July 2014, the first test launch is planned for 2015. Dr Tirtey will talk about this programme

and the opportunities such technology potentially offers the future utilisation of space.

SOCIETY JOURNAL, AUGUST 2014 2

Calendar of Events for 2014

August 2014 Programme September 2014 Programme

Astrophotography Group

Monday August 4 at 7:00pm

Young Astronomers

Friday August 1st at 7:00pm & 8:00pm

Film Night

Monday August 25 at 8:00pm

Welcome to New Members Young Astronomers is the session for our younger mem-

bers, aged 6yrs upwards.

At 7pm Margaret Arthur leads an interactive session cov-

ering various current topics with plenty of questions and

answers.

At 8pm David Wardle will work with the older members

of the group who are working on a range of research pro-

jects.

Members are welcome come to either or both sessions.

How to do astrophotography from the comfort of your

own home - using robotic telescopes over the Internet.

Keith will demonstrate how he uses the Slooh robotic tel-

escopes to capture images of Deep Sky Objects and show

live views from the observatory in Chile.

Note: If any reason the observatory is unable to run, an

alternate program item will be decided on.

Rebecca Mursell (ordinary)

Khemani Chatly (youth)

Peter Lowe (ordinary)

Chelsea Johnson (family)

Brent Russell (ordinary)

Carly Orr (family)

Shaun Lafferty (ordinary)

The Cosmos, Newton and Halley

This is a documentary that examines the relationship be-

tween Isaac Newton and Edmond Halley and their contri-

bution to science. It also looks at some of their less well

known activities.

Desiree De Courcy (family)

Tim Dobson (ordinary)

Steve Crow (family)

Claire Ignatova (family)

Scott Davidson (ordinary)

David Rae (ordinary)

3 WWW.ASTRONOMY.ORG.NZ

Sun-like Stars Reveal Their Ages Source: Harvard-Smithsonian Center for Astrophysics

D efining what makes a star "Sun-

like" is as difficult as defining

what makes a planet "Earth-like." A so-

lar twin should have a temperature,

mass, and spectral type similar to our

Sun. We also would expect it to be

about 4.5 billion years old. However, it

is notoriously difficult to measure a

star's age, so astronomers usually ig-

nore age when deciding if a star counts

as "Sun-like."

A new technique for measuring the age

of a star using its spin - gyrochronology

- is coming into its own. Today astrono-

mers are presenting the gyrochrono-

logical ages of 22 Sun-like stars. Before

this, only two Sun-like stars had meas-

ured spins and ages.

"We have found stars with properties

that are close enough to those of the

Sun that we can call them 'solar twins,'"

says lead author Jose Dias do Nasci-

mento of the Harvard-Smithsonian

Center for Astrophysics (CfA). "With

solar twins we can study the past, pre-

sent, and future of stars like our Sun.

Consequently, we can predict how plan-

etary systems like our Solar System will

be affected by the evolution of their

central stars."

To measure a star's spin, astronomers

look for changes in its brightness

caused by dark spots known as

starspots crossing the star's surface. By

watching how long it takes for a spot to

rotate into view, across the star and out

of view again, we learn how fast the star

is spinning.

The change in a star's brightness due to

starspots is very small, typically a few

percent or less. NASA's Kepler space-

craft excels at such exacting brightness

measurements. Using Kepler, do Nasci-

mento and his colleagues found that

the Sun-like stars in their study spin

once every 21 days on average, com-

pared to the 25-day rotation period of

our Sun at its equator.

Younger stars spin faster than older

ones because stars slow down as they

age, much like humans. As a result, a

star's rotation can be used like a clock

to derive its age. Since most of the stars

the team studied spin slightly faster

than our Sun, they tend to be younger

too.

This work expands on previous research

done by CfA astronomer (and co-

author on the new study) Soren Mei-

bom. Meibom and his collaborators

measured the rotation rates for stars in

a 1-billion-year-old cluster called NGC

6811. Since the stars had a known age,

astronomers could use them to cali-

brate the gyrochronology "clock." The

new research led by do Nascimento

examines free-floating "field" stars that

are not members of a cluster.

Since stars and planets form together at

the same time, by learning a star's age

we learn the age of its planets. And

since it takes time for life to develop

and evolve, knowing the ages of planet-

hosting stars could help narrow down

the best targets to search for signs of

alien life. Although none of the 22 stars

in the new study are known to have

planets, this work represents an im-

portant step in the hunt for Sun-like

stars that could host Earth-like planets.

Artist's conception of a hypothetical exoplanet, orbiting a yellow, Sun-like star. Astron-

omers have measured the ages of 22 Sun-like stars using their spins, in a method

called gyrochronology. Before now, only two Sun-like stars had measured spins and

ages. Credit: David A. Aguilar (CfA)


Radio-burst Discovery

Deepens Astrophysics Mystery Source: McGill University

T he discovery of a split-second

burst of radio waves by scientists

using the Arecibo radio telescope in

Puerto Rico provides important new

evidence of mysterious pulses that ap-

pear to come from deep in outer space.

The finding by an international team of

astronomers, published July 10 in The

Astrophysical Journal, marks the first

time that a so-called "fast radio burst"

has been detected using an instrument

other than the Parkes radio telescope in

Australia. Scientists using the Parkes

Observatory have recorded a handful of

such events, but the lack of any similar

findings by other facilities had led to

speculation that the Australian instru-

ment might have been picking up sig-

nals originating from sources on or near

Earth.

"Our result is important because it elim-

inates any doubt that these radio bursts

are truly of cosmic origin," said Victoria

Kaspi, an astrophysics professor at

McGill University in Montreal and Prin-

cipal Investigator for the pulsar-survey

project that detected this fast radio

burst. "The radio waves show every sign

of having come from far outside our

galaxy - a really exciting prospect."

Exactly what may be causing such radio

bursts represents a major new enigma

for astrophysicists. Possibilities include

a range of exotic astrophysical objects,

such as evaporating black holes, mer-

gers of neutron stars, or flares from

magnetars - a type of neutron star with

extremely powerful magnetic fields.

"Another possibility is that they are

bursts much brighter than the giant

pulses seen from some pulsars," notes

James Cordes, a professor of astronomy

at Cornell University and co-author of

the new study.

The unusual pulse was detected on

Nov. 2, 2012, at the Arecibo Observato-

ry, a National Science Foundation-

sponsored facility that boasts the

world's largest and most sensitive radio

telescope, with a radio-mirror dish

spanning 305 metres and covering

about 20 acres.

While fast radio bursts last just a few

thousandths of a second and have rare-

ly been detected, the international team

of scientists reporting the Arecibo find-

ing confirm previous estimates that

these strange cosmic bursts occur

roughly 10,000 times a day over the

whole sky. This astonishingly large

number is inferred by calculating how

much sky was observed, and for how

long, in order to make the few detec-

tions that have so far been reported.

"The brightness and duration of this

event, and the inferred rate at which

these bursts occur, are all consistent

with the properties of the bursts previ-

ously detected by the Parkes telescope

in Australia," said Laura Spitler, lead

author of the new paper. Dr. Spitler,

now a postdoctoral researcher at the

Max Planck Institute for Radio Astrono-

my in Bonn, Germany, was a PhD stu-

dent at Cornell when the research work

began.

The bursts appear to be coming from

beyond the Milky Way galaxy based on

measurement of an effect known as

plasma dispersion. Pulses that travel

through the cosmos are distinguished

from man-made interference by the

effect of interstellar electrons, which

cause radio waves to travel more slowly

at lower radio frequencies. The burst

detected by the Arecibo telescope has

three times the maximum dispersion

measure that would be expected from a

source within the galaxy, the scientists

report.

The discovery was made as part of the

Pulsar Arecibo L-Band Feed Array

(PALFA) survey, which aims to find a

large sample of pulsars and to discover

rare objects useful for probing funda-

mental aspects of neutron star physics

and testing theories of gravitational

physics.

Efforts are now under way to detect

radio bursts using radio telescopes that

can observe broad swaths of the sky to

The Arecibo Observatory Credit: Photo courtesy of the NAIC - Arecibo Observatory, a

facility of the NSF


help identify them. Telescopes under

construction in Australia and South

Africa as well as the CHIME telescope in

Canada have the potential to detect fast

radio bursts; astronomers say these and

other new facilities could pave the way

for many more discoveries and a better

understanding of this mysterious cos-

mic phenomenon.

The research was supported by grants

from the European Research Council,

the National Science Foundation, the

Natural Sciences and Engineering Re-

search Council of Canada, the Fonds de

recherche du Québec - Nature et tech-

nologies, and the Canadian Institute for

Advanced Research, among others.

Prof. Kaspi is the R. Howard Webster

Foundation Fellow of CIFAR's Cosmolo-

gy & Gravity program; she also holds

the Lorne Trottier Chair in Astrophysics

and Cosmology as well as a Canada

Research Chair at McGill.

The Arecibo Observatory is operated by

SRI International in alliance with Ana G.

Méndez-Universidad Metropolitana and

the Universities Space Research Associ-

ation, under a cooperative agreement

with the National Science Foundation

(AST-1100968). The data were pro-

cessed on the ATLAS cluster of the Max

Planck Institute for Gravitational Physics

(Albert Einstein Institute), Hannover,

Germany.

Supermassive Black Hole Blows Molecular

Gas Out of a Galaxy at 1,000,000km/h Source: University of Sheffield

N ew research by academics at the

University of Sheffield has solved

a long-standing mystery surrounding

the evolution of galaxies, deepening

our understanding of the future of the

Milky Way.

The supermassive black holes in the

cores of some galaxies drive massive

outflows of molecular hydrogen gas. As

a result, most of the cold gas is expelled

from the galaxies. Since cold gas is re-

quired to form new stars, this directly

affects the galaxies' evolution.

The outflows are now a key ingredient

in theoretical models of the evolution

of galaxies, but it has long been a mys-

tery as to how they are accelerated.

A study led by researchers in the Uni-

versity's Department of Physics and

Astronomy, with partners from the

Netherlands Institute of Radio Astrono-

my and the Center for Astrophysics,

Harvard, provides the first direct evi-

dence that the molecular outflows are

accelerated by energetic jets of elec-

trons that are moving at close to the

speed of light. Such jets are propelled

by the central supermassive black holes.

Using the Very Large Telescope of the

European Southern Observatory in

Chile to observe the nearby galaxy

IC5063, researchers found that the mo-

lecular hydrogen gas is moving at ex-

traordinary speeds - 1 million kilome-

tres per hour - at the locations in the

galaxy where its jets are impacting re-

gions of dense gas.

These findings help us further under-

stand the eventual fate of our own gal-

axy, the Milky Way, which will collide

with neighbouring galaxy Andromeda

in about 5 billion years. As a result of

this collision, gas will become concen-

trated at the centre of the system, fuel-

ling its supermassive black hole, and

potentially leading to the formation of

jets that will then eject the remaining

gas from the galaxy - just as we already

observe in IC5063.

Professor Clive Tadhunter, from the

University's Department of Physics and

Astronomy, said: "Much of the gas in

the outflows is in the form of molecular

hydrogen, which is fragile in the sense

that it is destroyed at relatively low en-

ergies. It is extraordinary that the mo-

lecular gas can survive being accelerat-

ed by jets of electrons moving at close

to the speed of light."

The results of the study have been pub-

lished in the journal Nature.

A Hubble Space Telescope image of the central part of the galaxy IC5063. The brighter

part at the centre shows the region where the jets driven by the supermassive black

hole are blasting material out of the galaxy. Credit: Hubble Space Telescope image


Living on the Moon

By Gavin Logan

J uly's Film Night featured a futuris-

tic film about returning to the

Moon and establishing a base that later

developed into a settlement.

An excellent attendance of over 50 So-

ciety members watched this film, which

covered America's plans for returning

to the Moon by 2020 (these now ap-

pear to be on hold for financial reasons)

and how this would be done. The audi-

ence were shown NASA's plans for a

new type of landing craft and more

flexible spacesuits for the astronauts.

NASA's futuristic space cabin designs

and Moon habitats were covered, along

with improved rockets. Futuristic lunar

vehicles for travelling on the Moon's

surface were shown being tested in the

rugged terrain of the Arizona desert.

The film also discussed how resources

might be shipped to the Moon and how

what is on the Moon could be used.

The term "ROxygen" was coined as the

name for the technologies for extract-

ing oxygen from Moon dust.

The dangers from the hazards of radia-

tion, solar flares and extreme tempera-

tures on the Moon were discussed and

how these were different for future long

-term stays compared to those faced by

the short-term visitors of the 1960s and

70s. Because of the length of the

Moon's days and nights (14 Earth days )

and the extreme difference in tempera-

tures caused by the lack of an atmos-

phere, the selection of a site for the

base is critical. The edge of a crater on

the South Pole called Shackleton was

considered the most likely, because its

rims are exposed to almost continual

sunlight. The importance of recycling

resources so that "yesterday's coffee

was today's soup" was highlighted

along with the need to use resources

with extreme efficiency.

The final part of the film discussed the

commercial potential of the Moon and

what resources of value could be taken

from the Moon. The film looked ahead

to an era of beyond the year 2050 to

see how a Moon base of similar dimen-

sions to the orbiting space station

could develop into a commercial settle-

ment.

After the main film a shorter Sky at

Night presentation on "How Gravity

Shapes the Universe" was shown.

Augusts' Film Night is on Monday 25th

at 8 p.m. at Stardome and features a

film from the Cosmos series on Newton

and Halley. This documentary examines

the relationship between Isaac Newton

and Edmond Halley and their contribu-

tion to science. It also looks at some of

their less well known activities.

Futuristic lunar vehicles for travelling on the Moon's surface being

tested by NASA in the Arizona desert.

Attendees at July Film Night watching a NASA rocket launch

Help Keep the Society Current: Join the AV Club!

Do you know how to use a camera or editing software, or want to learn? The AAS AV club needs you! We are looking for

helpful people who are either proficient with camera and editing equipment or very enthusiastic, to help us record and

prepare our guest lectures for all members to enjoy. The AV club will be responsible for:

Filming guest lectures

Copying files to the library PC

Synching audio, adding titles

Outputting edited lectures to DVD

So, if you want to learn, or just to participate, please let us know! You can contact Paul on 09 6341409 or email in-

[email protected]


Hubble Spots Spiral Bridge of Young Stars Linking Two Ancient Galaxies Source: Space Telescope Science Institute (STScI)

A SA's Hubble Space Telescope has

photographed an unusual struc-

ture 100,000 light-years long, which

resembles a corkscrew-shaped string of

pearls and winds around the cores of

two colliding galaxies.

The unique structure of the star spiral

may yield new insights into the for-

mation of stellar superclusters that re-

sult from merging galaxies and gas

dynamics in this rarely seen process.

"We were surprised to find this stun-

ning morphology. We've long known

that the 'beads on a string' phenome-

non is seen in the arms of spiral galax-

ies and in tidal bridges between inter-

acting galaxies. However, this particular

supercluster arrangement has never

been seen before in giant merging el-

liptical galaxies," said Grant Tremblay of

the European Southern Observatory in

Garching, Germany.

Young, blue super star clusters are

evenly spaced along the chain through

the galaxies at separations of 3,000

light-years. The pair of elliptical galaxies

is embedded deep inside the dense

galaxy cluster known as SDSS

J1531+3414. The cluster's powerful

gravity warps the images of back-

ground galaxies into blue streaks and

arcs that give the illusion of being in-

side the cluster, an effect known as

gravitational lensing.

Observing astronomers first hypothe-

sized that the "string of pearls" was

actually a lensed image from one of

these background galaxies, but their

recent follow-up observations with the

Nordic Optical Telescope in Santa Cruz

de Tenerife, Spain, ruled out this hy-

pothesis.

The galaxy cluster is part of a Hubble

program to observe 23 massive clusters

that create powerful gravitational

lensing effects on the sky. The clusters

were first catalogued in the Sloan Digi-

tal Sky Survey (SDSS), a project to cre-

ate the most detailed three-

dimensional maps ever made of the

Universe. Tremblay's team discovered

the bizarre string of stellar superclusters

by chance, while reviewing images as

they came in from Hubble. Researchers

were stunned by what they saw in SDSS

J1531+3414, and the unique nature of

the source spurred the team to do fol-

low-up observations with both ground-

and space-based telescopes.

The underlying physical processes that

give rise to the "string of pearls" struc-

ture are related to the Jeans instability,

a physics phenomenon that occurs

when the internal pressure of an inter-

stellar gas cloud is not strong enough

to prevent gravitational collapse of a

region filled with matter, resulting in

star formation. This process is analo-

gous to that which causes a column of

water falling from a rain cloud to dis-

rupt, and rain to fall in drops rather

than in continuous streams.

Scientists currently are working on a

better understanding of the star chain's

origin. One possibility is that the cold

molecular gas fuelling the burst of star

formation may have been native to the

two merging galaxies. Another possibil-

ity is a so-called "cooling flow" scenario,

where gas cools from the ultra-hot (10

million degree) atmosphere of plasma

that surrounds the galaxies, forming

pools of cold molecular gas that starts

to form stars. The third possibility is

that the cold gas fuelling the chain of

star formation originates from a high-

temperature shock wave created when

the two giant elliptical galaxies crash

together. This collision compresses the

gas and creates a sheet of dense cool-

ing plasma.

"Whatever the origin for this star-

forming gas is, the result is awesome.

It's very exciting. You can't find a mun-

dane explanation for this," Tremblay

said.

NASA's Hubble Space Telescope has photographed an unusual structure 100,000 light-

years long, which resembles a corkscrew-shaped string of pearls and winds around the

cores of two colliding galaxies. Credit: NASA, ESA, and G. Tremblay (ESO)


Astronomers Discover Seven Dwarf Galaxies with New Telescope Source: Yale University

Y ale University astronomers, using

a new type of telescope made by

stitching together telephoto lenses,

recently discovered seven celestial sur-

prises while probing a nearby spiral

galaxy. The previously unseen galaxies

may yield important insights into dark

matter and galaxy evolution, while pos-

sibly signalling the discovery of a new

class of objects in space.

For now, scientists know they have

found a septuplet of new galaxies that

were previously overlooked because of

their diffuse nature: The ghostly galax-

ies emerged from the night sky as the

team obtained the first observations

from the "homemade" telescope.

The discovery came quickly, in a rela-

tively small section of sky. "We got an

exciting result in our first images," said

Allison Merritt, a Yale graduate student

and lead author of a paper about the

discovery in The Astrophysical Journal

Letters. "It was very exciting. It speaks

to the quality of the telescope."

Pieter van Dokkum, chair of Yale's as-

tronomy department, designed the

robotic telescope with University of

Toronto astronomer Roberto Abraham.

Their Dragonfly Telephoto Array uses

eight telephoto lenses with special

coatings that suppress internally scat-

tered light. This makes the telescope

uniquely adept at detecting the very

diffuse, low surface brightness of the

newly discovered galaxies.

"These are the same kind of lenses that

are used in sporting events like the

World Cup. We decided to point them

upward instead," van Dokkum said. He

and Abraham built the compact, oven-

sized telescope in 2012 at New Mexico

Skies, an observatory in Mayhill, N.M.

The telescope was named Dragonfly

because the lenses resemble the com-

pound eye of an insect.

"We knew there was a whole set of sci-

ence questions that could be answered

if we could see diffuse objects in the

sky," van Dokkum said. In addition to

discovering new galaxies, the team is

looking for debris from long-ago galaxy

collisions.

"It's a new domain. We're exploring a

region of parameter space that had not

been explored before," van Dokkum

said.

The Yale scientists will tackle a key

question next: Are these seven newly

found objects dwarf galaxies orbiting

around the M101 spiral galaxy, or are

they located much closer or farther

away, and just by chance are visible in

the same direction as M101?

If it's the latter, Merritt said, these ob-

jects represent something entirely dif-

ferent. "There are predictions from gal-

axy formation theory about the need

for a population of very diffuse, isolated

galaxies in the Universe," Merritt said.

"It may be that these seven galaxies are

the tip of the iceberg, and there are

thousands of them in the sky that we

haven't detected yet."

Merritt stressed that until they collect

more data and determine the distances

to the objects, researchers won't know

their true nature. But the possibilities

are intriguing enough that the team has

been granted the opportunity to use

the Hubble Space Telescope for further

study.

"I'm confident that some of them will

turn out to be a new class of objects,"

van Dokkum said. "I'd be surprised if all

seven of them are satellites of M101."

Meanwhile, there is also more work to

be done with the new telescope. "We

are collecting new data with the Drag-

onfly telescope every clear night. We're

all curious to see what other surprises

the night sky has in store for us," Mer-

ritt said.

This image shows the field of view from the Dragonfly Telephoto Array, cantered on

M101. Inset images highlight the seven newly discovered galaxies. Credit: Image cour-

tesy of Yale University


Giant Planet Ejected from the Solar System?

Source: Southwest Research Institute

J ust as an expert chess player sacri-

fices a piece to protect the queen,

the Solar System may have given up a

giant planet and spared Earth, accord-

ing to an article recently published in

The Astrophysical Journal Letters.

"We have all sorts of clues about the

early evolution of the Solar System,"

says author Dr. David Nesvorny of the

Southwest Research Institute. "They

come from the analysis of the trans-

Neptunian population of small bodies

known as the Kuiper Belt, and from the

lunar cratering record."

These clues suggest that the orbits of

giant planets were affected by a dy-

namical instability when the Solar Sys-

tem was only about 600 million years

old. As a result, the giant planets and

smaller bodies scattered away from

each other.

Some small bodies moved into the Kui-

per Belt and others travelled inward,

producing impacts on the terrestrial

planets and the Moon. The giant plan-

ets moved as well. Jupiter, for example,

scattered most small bodies outward

and moved inward.

This scenario presents a problem, how-

ever. Slow changes in Jupiter's orbit,

such as the ones expected from interac-

tion with small bodies, would have con-

veyed too much momentum to the

orbits of the terrestrial planets. Stirring

up or disrupting the inner Solar System

and possibly causing Earth to collide

with Mars or Venus.

"Colleagues suggested a clever way

around this problem," says Nesvorny.

"They proposed that Jupiter's orbit

quickly changed when Jupiter scattered

off of Uranus or Neptune during the

dynamical instability in the outer Solar

System." The "jumping-Jupiter" theory,

as it is known, is less harmful to the

inner Solar System, because the orbital

coupling between the terrestrial planets

and Jupiter is weak if Jupiter jumps.

Nesvorny conducted thousands of

computer simulations of the early Solar

System to test the jumping-Jupiter the-

ory. He found that, as hoped for, Jupiter

did in fact jump by scattering from Ura-

nus or Neptune. When it jumped, how-

ever, Uranus or Neptune was knocked

out of the Solar System. "Something

was clearly wrong," he says.

Motivated by these results, Nesvorny

wondered whether the early Solar Sys-

tem could have had five giant planets

instead of four. By running the simula-

tions with an additional giant planet

with mass similar to that of Uranus or

Neptune, things suddenly fell in place.

One planet was ejected from the Solar

System by Jupiter, leaving four giant

planets behind, and Jupiter jumped,

leaving the terrestrial planets undis-

turbed.

"The possibility that the Solar System

had more than four giant planets initial-

ly, and ejected some, appears to be

conceivable in view of the recent dis-

covery of a large number of free-

floating planets in interstellar space,

indicating the planet ejection process

could be a common occurrence," says

Nesvorny.

This research was funded by the Na-

tional Lunar Science Institute and the

National Science Foundation.

The paper, "Young Solar System's Fifth

Giant Planet?" by Dr. David Nesvorny

was published online by The Astrophysi-

cal Journal Letters.

Artist's impression of a planet ejected from the early Solar System. Credit: Image cour-

tesy of Southwest Research Institute


Friction from Tides Could Help Distant Earth-sized Planets Survive, and Thrive Source: NASA

A s anybody who has started a

campfire by rubbing sticks

knows, friction generates heat. Now,

computer modelling by NASA scientists

shows that friction could be the key to

survival for some distant Earth-sized

planets travelling in dangerous orbits.

The findings are consistent with obser-

vations that Earth-sized planets appear

to be very common in other star sys-

tems. Although heat can be a destruc-

tive force for some planets, the right

amount of friction, and therefore heat,

can be helpful and perhaps create con-

ditions for habitability.

"We found some unexpected good

news for planets in vulnerable orbits,"

said Wade Henning, a University of

Maryland scientist working at NASA's

Goddard Space Flight Center in Green-

belt, Maryland, and lead author of the

new study. "It turns out these planets

will often experience just enough fric-

tion to move them out of harm's way

and into safer, more-circular orbits

more quickly than previously predict-

ed."

Simulations of young planetary systems

indicate that giant planets often upset

the orbits of smaller inner worlds. Even

if those interactions aren't immediately

catastrophic, they can leave a planet in

a treacherous eccentric orbit - a very

elliptical course that raises the odds of

crossing paths with another body, be-

ing absorbed by the host star, or get-

ting ejected from the system.

Another potential peril of a highly ec-

centric orbit is the amount of tidal

stress a planet may undergo as it draws

very close to its star and then retreats

away. Near the star, the gravitational

force is powerful enough to deform the

planet, while in more distant reaches of

the orbit, the planet can ease back into

shape. This flexing action produces fric-

tion, which generates heat. In extreme

cases, tidal stress can produce enough

heat to liquefy the planet.

In this new study, available online in the

July 1, 2014, issue of the Astrophysical

Planets in eccentric orbits can experience powerful tidal forces. A planet covered by a very thick ice shell (left) is springy enough to

flex a great deal, generating a lot of internal friction and heat. Some terrestrial planets (right) also will flex, especially with partially

molten inner layers. Credit: NASA's Goddard Space Flight Center


Journal, Henning and his colleague Ter-

ry Hurford, a planetary scientist at God-

dard, explored the effects of tidal

stresses on planets that have multiple

layers, such as rocky crust, mantle or

iron core.

One conclusion of the study is that

some planets could move into a safer

orbit about 10 to 100 times faster than

previously expected - in as a little as a

few hundred thousand years, instead of

the more typical rate of several million

years. Such planets would be driven

close to the point of melting or, at least,

would have a nearly melted layer, simi-

lar to the one right below Earth's crust.

Their interior temperatures could range

from moderately warmer than our plan-

et is today up to the point of having

modest-sized magma oceans.

The transition to a circular orbit would

be speedy because an almost-melted

layer would flex easily, generating a lot

of friction-induced heat. As the planet

threw off that heat, it would lose energy

at a fast rate and relax quickly into a

circular orbit. (Later, tidal heating would

turn off, and the planet's surface could

become safe to walk on.)

In contrast, a world that had completely

melted would be so fluid that it would

produce little friction. Before this study,

that is what researchers expected to

happen to planets undergoing strong

tidal stresses.

Cold, stiff planets tend to resist the tidal

stress and release energy very slowly. In

fact, Henning and Hurford found that

many of them actually generate less

friction than previously thought. This

may be especially true for planets far-

ther from their stars. If these worlds are

not crowded by other bodies, they may

be stable in their eccentric orbits for a

long time.

"In this case, the longer, non-circular

orbits could increase the 'habitable

zone,' because the tidal stress will re-

main an energy source for longer peri-

ods of time," said Hurford. "This is great

for dim stars or ice worlds with subsur-

face oceans."

Surprisingly, another way for a terrestri-

al planet to achieve high amounts of

heating is to be covered in a very thick

ice shell, similar to an extreme

"snowball Earth." Although a sheet of

ice is a slippery, low-friction surface, an

ice layer thousands of kilometres thick

would be very springy. A shell like this

would have just the right properties to

respond strongly to tidal stress, gener-

ating a lot of heat. (The high pressures

inside these planets could prevent all

but the topmost layers from turning

into liquid water.)

The researchers found that the very

responsive layers of ice or almost-

melted material could be relatively thin,

just a few hundred kilometres deep in

some cases, yet still dominate the glob-

al behaviour.

The team modelled planets that are the

size of Earth and up to two-and-a-half

times larger. Henning added that su-

perEarths - planets at the high end of

this size range - likely would experience

stronger tidal stresses and potentially

could benefit more from the resulting

friction and heating.

Now that the researchers have shown

the importance of the contributions of

different layers of a planet, the next

step is to investigate how layers of

melted material flow and change over

time.

Auckland Astronomical Society Inc,

PO Box 24-187, Royal Oak, Auckland 1345, New Zealand

Email [email protected]

Journal [email protected]

Website www.astronomy.org.nz facebook.com/AuckAstroSoc

Membership inquiries contact Andrew Buckingham at [email protected] or by phone on (09) 473 5877 or (027) 246 2446.

Society Contacts

President Bill Thomas (021) 024 04992

Vice-President Grant Christie (09) 478 4874

Treasurer & Andrew Buckingham (09) 473 5877 Membership

Secretary Gavin Logan (022) 691 2055

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The 2014 Council


Stretching Forces Shaped Jupiter Moon's Surface, Laboratory Model Suggests Source: Southwest Research Institute

P rocesses that shaped the ridges

and troughs on the surface of

Jupiter's icy moon Ganymede are likely

similar to tectonic processes seen on

Earth, according to a team of research-

ers led by Southwest Research Institute

(SwRI). To arrive at this conclusion, the

team subjected physical models made

of clay to stretching forces that simulate

tectonic action. The results were pub-

lished in Geophysical Research Letters.

Physical analogue models simulate ge-

ologic structures in laboratory settings

so that the developmental sequence of

various phenomena can be studied as

they occur. The team - including re-

searchers from SwRI, Wheaton College,

NASA's Jet Propulsion Laboratory and

NuStar Energy LP - created complex

patterns of faults in their models, simi-

lar to the ridge and trough features

seen in some regions of Ganymede. The

models consisted of a "wet clay cake"

material possessing brittle characteris-

tics to simulate how the icy moon's

lithosphere, the outermost solid shell,

responds to stresses by cracking.

The laboratory models suggest that

characteristic patterns of ridges and

troughs, called grooved terrain on Gan-

ymede, result from its surface being

stretched. "The physical models showed

a marked similarity to the surface fea-

tures observed on Ganymede," said co-

author Dr. Danielle Wyrick, a senior

research scientist in the SwRI Space

Science and Engineering Division.

"From the experiments, it appears that a

process in which the crust breaks into

separate blocks by large amounts of

extension is the primary mechanism for

creating these distinct features."

"Physical analogue modelling allows us

to simulate the formation of complex

three-dimensional geologic structures

on Ganymede, without actually going to

Ganymede," said co-author Dr. David

Ferrill, director of the Earth, Material

and Planetary Sciences Department in

the SwRI Geosciences and Engineering

Division. "These scaled models are able

to reproduce the fine geometric details

of geologic processes, such as faulting,

and to develop and test hypotheses for

landscape evolution on planetary bod-

ies."

SwRI researchers previously have used

physical analogue models to examine

the process by which pit crater chains -

a series of linear pits, or depressions -

develop on Mars, and how magma in

the Martian subsurface deforms the

surface of the Red Planet.

An image of a tabletop-size analogue model (left) shows details of fault systems created by extension that visually match an image

by spacecraft Galileo of faulted terrain on Ganymede (right). Credit: Image courtesy of Southwest Research Institute


Something is Amiss in the Universe: Cosmic Accounting Reveals Missing Light Crisis Source: Carnegie Institution

S omething is amiss in the Universe.

There appears to be an enormous

deficit of ultraviolet light in the cosmic

budget.

The vast reaches of empty space be-

tween galaxies are bridged by tendrils

of hydrogen and helium, which can be

used as a precise "light meter." In a

recent study published in The Astro-

physical Journal Letters, a team of scien-

tists finds that the light from known

populations of galaxies and quasars is

not nearly enough to explain observa-

tions of intergalactic hydrogen. The

difference is a stunning 400 percent.

"It's as if you're in a big, brightly-lit

room, but you look around and see

only a few 40-watt light bulbs," noted

Carnegie's Juna Kollmeier, lead author

of the study. "Where is all that light

coming from? It's missing from our

census."

Strangely, this mismatch only appears

in the nearby, relatively well-studied

cosmos. When telescopes focus on gal-

axies billions of light years away (and

therefore are viewing the Universe bil-

lions of years in its past), everything

seems to add up. The fact that this ac-

counting works in the early Universe

but falls apart locally has scientists puz-

zled.

The light in question consists of highly

energetic ultraviolet photons that are

able to convert electrically neutral hy-

drogen atoms into electrically charged

ions. The two known sources for such

ionizing photons are quasars - powered

by hot gas falling onto supermassive

black holes over a million times the

mass of the Sun - and the hottest

young stars.

Observations indicate that the ionizing

photons from young stars are almost

always absorbed by gas in their host

galaxy, so they never escape to affect

intergalactic hydrogen. But the number

of known quasars is far lower than

needed to produce the required light.

"Either our accounting of the light from

galaxies and quasars is very far off, or

there's some other major source of

ionizing photons that we've never rec-

ognized," Kollmeier said. "We are call-

ing this missing light the photon under-

production crisis. But it's the astrono-

mers who are in crisis - somehow or

other, the Universe is getting along just

fine."

The mismatch emerged from compar-

ing supercomputer simulations of inter-

galactic gas to the most recent analysis

of observations from Hubble Space

Telescope's Cosmic Origins Spectro-

graph. "The simulations fit the data

beautifully in the early Universe, and

they fit the local data beautifully if we're

allowed to assume that this extra light

is really there," explained Ben Oppen-

heimer a co-author from the University

of Colorado. "It's possible the simula-

tions do not reflect reality, which by

itself would be a surprise, because in-

tergalactic hydrogen is the component

of the Universe that we think we under-

stand the best."

"The most exciting possibility is that the

missing photons are coming from some

exotic new source, not galaxies or qua-

sars at all," said Neal Katz a co-author

from the University of Massachusetts at

Amherst.

For example, the mysterious dark mat-

ter, which holds galaxies together but

has never been seen directly, could

itself decay and ultimately be responsi-

ble for this extra light.

"You know it's a crisis when you start

seriously talking about decaying dark

matter!" Katz remarked.

"The great thing about a 400% discrep-

ancy is that you know something is

really wrong," commented co-author

David Weinberg of The Ohio State Uni-

versity. "We still don't know for sure

what it is, but at least one thing we

thought we knew about the present day

Universe isn't true."

Whether the explanation is exotic or

not, astronomers will be working hard

to shed light on the mystery.

Other co-authors on the study are Fran-

cesco Haardt of the Università dell'In-

subria, Romeel Davé of the University of

the Western Cape, Mark Fardal of Uni-

versity of Massachusetts Amherst, Piero

Madau of University of California Santa

Cruz, Charles Danforth of the University

of Colorado, Amanda Ford of University

of Arizona, Molly Peeples of the Space

Telescope Science Institute, and Joseph

McEwen of The Ohio State University.

Computer simulations of intergalactic hydrogen in a "dimly lit "Universe (left) and a

"brightly lit" Universe (right) that has five times more of the energetic photons that

destroy neutral hydrogen atoms. Hubble Space Telescope observations of hydrogen

absorption match the picture on the right, but using only the known astronomical

sources of ultraviolet light produces the much thicker structures on the left, and a se-

vere mismatch with the observations. Credit: Ben Oppenheimer and Juna Kollmeier


Newly Spotted Frozen World Orbits in a Binary Star System Source: Ohio State University

A newly discovered planet in a

binary star system located 3,000

light-years from Earth is expanding

astronomers' notions of where Earth-

like - and even potentially habitable -

planets can form, and how to find them.

At twice the mass of Earth, the planet

orbits one of the stars in the binary

system at almost exactly the same dis-

tance from which Earth orbits the Sun.

However, because the planet's host star

is much dimmer than the Sun, the plan-

et is much colder than Earth - a little

colder, in fact, than Jupiter's icy moon

Europa.

Four international research teams, led

by Professor Andrew Gould of The Ohio

State University, published their discov-

ery in the July 4 issue of the journal

Science.

The study provides the first evidence

that terrestrial planets can form in or-

bits similar to Earth's, even in a binary

star system where the stars are not very

far apart. Although this planet itself is

too cold to be habitable, the same

planet orbiting a Sun-like star in such a

binary system would be in the so-called

"habitable zone" - the region where

conditions might be right for life.

"This greatly expands the potential lo-

cations to discover habitable planets in

the future," said Scott Gaudi, professor

of astronomy at Ohio State. "Half the

stars in the galaxy are in binary systems.

We had no idea if Earth-like planets in

Earth-like orbits could even form in

these systems. "

Very rarely, the gravity of a star focuses

the light from a more distant star and

magnifies it like a lens. Even more rare-

ly, the signature of a planet appears

within that magnified light signal. The

technique astronomers use to find such

planets is called gravitational micro-

lensing, and computer modelling of

these events is complicated enough

when only one star and its planet are

acting as the lens, much less two stars.

Searching for planets within binary sys-

tems is tricky for most techniques, be-

cause the light from the second star

complicates the interpretation of the

data. "But in gravitational micro-

lensing," Gould explained, "we don't

even look at the light from the star-

planet system. We just observe how its

gravity affects light from a more distant,

unrelated, star. This gives us a new tool

to search for planets in binary star sys-

tems."

When the astronomers succeeded in

detecting this new planet, they were

able to document that it produced two

separate signatures - the primary one,

which they typically use to detect plan-

ets, and a secondary one that had pre-

viously been only hypothesized to exist.

The first was a brief dimming of light, as

the planet's gravity disrupted one of the

magnified images of the source star.

But the second effect was an overall

distortion of the light signal.

"Even if we hadn't seen the initial signa-

ture of the planet, we could still have

detected it from the distortion alone,"

Gould said, pointing to a graph of the

light signal. "The effect is not obvious.

You can't see it by eye, but the signal is

unmistakable in the computer model-

ling."

Gaudi explained the implications.

"Now we know that with gravitational

microlensing, it's actually possible to

infer the existence of a planet - and to

know its mass, and its distance from a

star - without directly detecting the

dimming due to the planet," he said.

"We thought we could do that in princi-

ple, but now that we have empirical

evidence, we can use this method to

This artist's rendering shows a newly discovered planet (far right) orbiting one star (right) of a binary star system. The discovery, made

by a collaboration of international research teams and led by researchers at The Ohio State University, expands astronomers' notions

of where to look for planets in our galaxy. Credit: Image by Cheongho Han, Chungbuk National University, Republic of Korea


find planets in the future."

The nature of these distortions is still

somewhat of a mystery, he admitted.

"We don't have an intuitive understand-

ing of why it works. We have some idea,

but at this point, I think it would be fair

to say that it's at the frontier of our

theoretical work."

The planet, called OGLE-2013-BLG-

0341LBb, first appeared as a "dip" in the

line tracing the brightness data taken

by the OGLE (Optical Gravitational

Lensing Experiment) telescope on April

11, 2013. The planet briefly disrupted

one of the images formed by the star it

orbits as the system crossed in front of

a much more distant star 20,000 light-

years away in the constellation Sagitta-

rius.

"Before the dip, this was just another

microlensing event," Gould said. It was

one of approximately 2,000 discovered

every year by OGLE, with its new large-

format camera that monitors 100 mil-

lion stars many times per night search-

ing for such events.

"It's really the new OGLE-IV survey that

made this discovery possible," he add-

ed. "They got half a dozen measure-

ments of that dip and really nailed it."

From the form of the dip, whose

"wings" were traced out in MOA

(Microlensing Observations in Astro-

physics) data, they could see that the

source was headed directly toward the

central star.

Then, for two weeks, astronomers

watched the magnified light continue

to brighten from telescopes in Chile,

New Zealand, Israel and Australia. The

teams included OGLE, MOA, MicroFUN

(the Microlensing Follow Up Network),

and the Wise Observatory.

Even then, they still didn't know that

the planet's host star had another com-

panion - a second star locked into orbit

with it. But because they were already

paying close attention to the signal, the

astronomers noticed when the binary

companion unexpectedly caused a

huge eruption of light called a caustic

crossing.

By the time they realized that the lens

was not one star, but two, they had

captured a considerable amount of data

- and made a surprising discovery: the

distortion.

Weeks after all signs of the planet had

faded, the light from the binary-lens

caustic crossing became distorted, as if

there were a kind of echo of the origi-

nal planet signal.

Intensive computer analysis by Profes-

sor Cheongho Han at Chungbuk Na-

tional University in Korea revealed that

the distortion contained information

about the planet - its mass, separation

from its star, and orientation - and that

information matched perfectly with

what astronomers saw during their di-

rect observation of the dip due to the

planet. So the same information can be

captured from the distortion alone.

This detailed analysis showed that the

planet is twice the mass of Earth, and

orbits its star from an Earth-like dis-

tance, around 145 million kilometres.

But its star is 400 times dimmer than

our Sun, so the planet is very cold -

around 60 Kelvin (-213°C), which makes

it a little colder than Jupiter's moon

Europa. The second star in the star sys-

tem is only as far from the first star as

Saturn is from our Sun. But this binary

companion, too, is very dim.

Still, binary star systems composed of

dim stars like these are the most com-

mon type of star system in our galaxy,

the astronomers said. So this discovery

suggests that there may be many more

terrestrial planets out there - some pos-

sibly warmer, and possibly harbouring

life.

Three other planets have been discov-

ered in binary systems that have similar

separations, but using a different tech-

nique. This is the first one close to Earth

-like size that follows an Earth-like orbit,

and its discovery within a binary system

by gravitational microlensing was by

chance.

"Normally, once we see that we have a

binary, we stop observing. The only

reason we took such intensive observa-

tions of this binary is that we already

knew there was a planet," Gould said.

"In the future we'll change our strate-

gy."

In particular, Gould singled out the

work of amateur astronomer and fre-

quent collaborator Ian Porritt of Palm-

erston North, New Zealand, who

watched for gaps in the clouds on the

night of April 24 to get the first few

critical measurements of the jump in

the light signal that revealed that the

planet was in a binary system. Six other

amateurs from New Zealand and Aus-

tralia contributed as well.

Other project collaborators hailed from

Ohio State, Warsaw University Observa-

tory, Chungbuk National University,

Harvard-Smithsonian Center for Astro-

physics, University of Cambridge, Uni-

versidad de Concepción, Auckland Ob-

servatory, Auckland University of Tech-

nology, University of Canterbury, Texas

A&M University, Korea Astronomy and

Space Science Institute, Solar-Terrestrial

Environment Laboratory, University of

Notre Dame, Massey University, Univer-

sity of Auckland, National Astronomical

Observatory of Japan, Osaka University,

Nagano National College of Technolo-

gy, Tokyo Metropolitan College of Aer-

onautics, Victoria University, Mt. John

University Observatory, Kyoto Sangyo

University, Tel-Aviv University and the

University of British Columbia.

Funding came from the National Sci-

ence Foundation, NASA (including a

NASA Sagan Fellowship), European

Research Council, Polish Ministry of

Science and Higher Education, National

Research Foundation of Korea, U.S.-

Israel Binational Science Foundation,

Japan Society for the Promotion of Sci-

ence, Marsden Fund from the Royal

Society of New Zealand and the Israeli

Centers of Research Excellence.


Society Astronomical Equipment for Rent

The Society has a wide variety of equipment available for rental to

members, from beginner friendly Dobsonian telescopes, through to

more advanced computerised GOTO systems. All rental equipment is

of high quality and regularly maintained.

Rental periods are normally in 4 week blocks, but other arrangements

may be available if you have a specific requirement. Full training and

support is given for all equipment, including advice if equipment is

suitable for your needs, or experience level.

Current rental equipment includes:

* 200mm Astronz Dobsonian Telescopes ($10/week)

* Celestron Nexstar 5 127mm Schmidt Cassegrain Alt/Az GOTO Telescope ($12.50/week)

* iOptron Minitower multipupose Alt/Az Mount with Celestron C5 127mm OTA ($15/week)

* Meade 90mm Achromatic Refractor ($7.50/week)

Also, newly added to the rental stock

* Coronado PST 40mm Hydrogen-Alpha Solar Telescope ($12.50/week)

* iOptron ZEQ25 Computerised Equatorial Mount (Coming Soon!)

We are often adding items to our rental equipment, and we're really keen to hear what other items

may be useful to members - any ideas, or for any information regarding availability or how to rent

equipment, please contact Steve Hennerley at [email protected] or on 027 245 6441

New Technology Illuminates Colder Objects in Deep Space Source: Northwestern University

T oo cool and faint, many objects in

the Universe are impossible to

detect with visible light. Now a McCor-

mick team has refined a new technolo-

gy that could make these colder objects

more visible, paving the way for en-

hanced exploration of deep space.

"High performance infrared cameras are

crucial for space exploration missions,"

said Manijeh Razeghi, the Walter P.

Murphy Professor of Electrical Engi-

neering and Computer Science in the

McCormick School of Engineering and

Applied Science. "By studying the infra-

red waves emitted by cool stars and

planets, scientists are beginning to un-

lock the mysteries of these cooler ob-

jects."

Researchers have long looked to infra-

red waves to probe the depths of space.

Infrared has a longer wavelength than

visible light, so it can penetrate dense

regions of gas and dust with less scat-

tering and absorption. Current infrared

detectors are typically built with mercu-

ry cadmium telluride, which works well

with mid- and long-infrared wave-

lengths. However, this well-established

technology demonstrates low uniformi-

ty and instability for infrared waves with

very long wavelengths.

Published in the June 23 issue of Ap-

plied Physics Letters, Razeghi and her

collaborators describe a new technolo-

gy, which uses a novel type II superlat-

tice material called indium arsenide/

indium arsenide antimonide (InAs/

InAsSb). The technology shows a stable

optical response in regards to very long

wavelength infrared light.

By engineering the quantum properties

of the type II superlattice material, the

team demonstrated the world's first

InAs/InAsSb very long wavelength infra-

red photodiodes with high perfor-

mance. The new detector can be used

as an inexpensive and robust alternative

to current infrared technologies.

"This material has emerged as the plat-

form for the new generation of infrared

detection and imaging," said Razeghi

who leads McCormick's Center for

Quantum Devices. "It has proved to

have longer carrier lifetimes and prom-

ises a better controllability in epitaxial

growth and simpler manufacturability."

Razeghi presented this work in a key-

note talk at the International Society for

Optical and Photonics Defense, Securi-

ty, and Sensing conference in Baltimore

in April and at the Microelectronics

Workshop in Istanbul, Turkey last

month.


The Evening Sky in August 2014

By Alan Gilmore

High up the northwest sky are reddish Mars and cream-coloured Saturn, with bluish Spica below them. Low in the

northwest, below Mars and Saturn, is the bright orange star Arcturus. It sets around 10 pm, twinkling red and green

as it goes. Low in the north is Vega, making a brief appearance in our sky. Exactly opposite Vega, low in the south, is

Canopus twinkling colourfully. In the southwest are 'The Pointers', Beta and Alpha Centauri with Crux, the South-

ern Cross, below them. Nearly overhead is Antares.

Mars and Saturn make a close pair during August. Saturn and the background stars slip down the evening sky night

to night but Mars keeps much the same elevation. The two planets will be close together around the 25th. Their

closeness is a line-of-sight effect. Mars is 200 million km away. Saturn is 1520 million km away. A small telescope

shows Saturn's ring system and biggest moon Titan looking like a star about four ring-diameters from the planet. The

moon will be very close to Saturn at midnight on August 4/5. Mars is very small in a telescope as it is half the size of

earth and far away.

Mercury begins its best evening sky appearance of the year. By the end of the month it will be setting due west 1½

hours after the Sun. It is the only bright 'star' in that region. Mercury is 1/3rd the diameter of Earth, so always tiny in a

telescope. The crescent Moon will be near Mercury on the 27th.

Just north of overhead the orange star Antares marks the heart of the Scorpion. The Scorpion's tail hooks around the

zenith like a back-to-front question mark. Antares and the tail make the 'fish-hook of Maui' in Maori star lore. Antares

is a red giant star: 600 light years* away and 19 000 times brighter than the Sun. It is a relatively cool 3000°C, hence

its red-hot colour. Below or right of the Scorpion's tail is 'the teapot' made by the brightest stars of Sagittarius. It is

upside down in our southern hemisphere view.

Midway down the southwest sky are 'The Pointers ', Beta and Alpha Centauri. They point down and rightward to

Crux the Southern Cross. Alpha Centauri is the third brightest star and the closest of the naked eye stars, 4.3 light

years away. Beta Centauri, like most of the stars in Crux, is a blue-giant star hundreds of light years away and thou-

sands of times brighter than the Sun.

Canopus, the second brightest star, is near the south skyline at dusk. It swings upward into the southeast sky

through the morning hours. Canopus is truly bright: 13,000 times brighter than the Sun and 310 light years away. On

the opposite horizon is Vega, one of the brightest northern stars. It is due north in mid-evening and sets around

midnight. Vega is 52 times brighter than the Sun and 25 light years away.

The Milky Way is brightest and broadest overhead in Scorpius and Sagittarius. In a dark sky it can be traced down

past the Pointers and Crux into the southwest. To the northeast it passes Altair, meeting the skyline right of Vega.

The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars of which the Sun is just one. The

thick hub of the galaxy, 30 000 light years away, is in Sagittarius. The actual centre is hidden by dust clouds in space.

At the very centre is a black hole four million times the Sun's mass. Dust clouds near us appear as gaps and slots in

the Milky Way. Binoculars show many clusters of stars and some glowing gas clouds in the Milky Way.

The Large and Small Clouds of Magellan LMC and SMC look like two misty patches of light low in the south, easily

seen by eye on a dark moonless night. They are galaxies like our Milky Way but much smaller. The LMC is about 160

000 light years away; the SMC about 200 000 light years away.

Brilliant Venus sinks into the dawn twilight in August. It rises in the northeast around 6:30 am all month but twilight

gets steadily earlier. Jupiter begins its morning sky appearance in August and moves up toward Venus. On the 18th

the two bright planets will be less than a full Moon's diameter apart. Venus is the brighter one. Again, the closeness

is a line-of-sight effect. Venus is 240 million km away. Jupiter is 930 million km away. Venus is leaving us behind as

it moves to the far side of the Sun from us. We are catching up on Jupiter as we move toward its side of the Sun.

*A light year (l.y.) is the distance that light travels in one year: nearly 10 million million km or 1013

km. Sunlight takes

eight minutes to get here; moonlight about one second. Sunlight reaches Neptune, the outermost major planet, in

four hours. It takes four years for sunlight to reach the nearest star, Alpha Centauri.

Notes by Alan Gilmore, University of Canterbury's Mt John Observatory, P.O. Box 56, Lake Tekapo 7945, New Zealand.

www.canterbury.ac.nz


The Night Sky for August 2014


Solar System Events August 2014 From the RASNZ Website

apogee: Furthest point in the orbit of a body orbiting the Earth

conjunction: Two astronomical objects are 'lined up' (have the same right ascension) when viewed from Earth

declination: 'Latitude' for celestial objects. The distance in degrees above (north) or below (south) the celestial equator.

perigee: Nearest point in the orbit of a body orbiting the Earth

August 2 Spica 2.2° south of the Moon

August 3 Mars 2.1° south of the Moon

August 4 Moon first quarter

August 7 Moon southern most declination (-18.8°)

August 8 Pluto 2.4° south of the Moon

August 10 Moon full Moon at perigee

August 11 Neptune 4.3° south of the Moon

August 14 Uranus 1.2° south of the Moon Occn

August 15 Mercury 1.2° north of Regulus

August 17 Moon last quarter

August 18 Venus 0.2° north of Jupiter

August 19 Moon northern most declination (18.7°)

August 23 Jupiter 5.3° north of the Moon

August 24 Venus 5.5° north of the Moon

August 25

Regulus 4.4° north of the Moon

Moon new

Mars 3.4° south of Saturn

August 27 Mercury 3.3° north of the Moon

August 29 Neptune at opposition Spica 2.4° south of the Moon

August 31 Saturn 0.3° south of the Moon Occn

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August 2014