October 2019

SOCIETY JOURNAL Society Meeting Monday 14th October at 8:00pm

Imaging the Invisible with Dr Willem van Straten

T he radio signals from pulsars travel to Earth along multiple ray paths owing to both diffractive and refractive effects of turbulent structure in the free electrons along the line of sight. By studying the twinkling of pulsars,

we can image and study otherwise invisible structures in the ionised interstellar medium. In principle, these maps can be used to mitigate a significant source of systematic error in Pulsar Timing Array experiments, which aim to detect the very low-frequency gravitational wave background produced by the host of supermassive binary black holes that merged in the distant past.

Dr Willem van Straten:

As an undergraduate in Canada, I was preparing for a job in the space industry when I learned about radio astrono-my and new ways to study the physical extremes of our Universe through pulsars. I completed my PhD on high-precision pulsar timing in Australia before undertaking post-doctoral and academic staff appointments at the Neth-erlands Foundation for Research in Astronomy (ASTRON), The Centre for Gravitational Wave Astronomy (The Uni-versity of Texas Rio Grande Valley), and the Centre for Astrophysics & Supercomputing (Swinburne University of Technology). In 2016, I joined AUT as a Senior Lecturer.

I’ve co-authored over 100 refereed journal articles, primarily related to the study of pulsars and fast radio bursts, including 4 in Science and 2 in Nature. I work closely with international collaborators on large, long-term projects such as the Parkes Pulsar Timing Array (PPTA), the International Pulsar Timing Array (IPTA), and the Survey for Pul-sars and Extragalactic Radio Bursts (SUPERB). In support of these projects, I’ve led the development of three scien-tific data analysis packages that are used by the international community of pulsar astronomers (psrdada, dspsr, and psrchive). I also led the design of the pulsar timing instrumentation for the Square Kilometre Array (SKA) as a member of the SKA Central Signal Processor consortium.

SOCIETY JOURNAL, October 2019 2

Programme and Notices

October 2019 Programme November 2019 Programme

Chris Benton will do a pictorial "Show and Tell" story of

three large professional telescopes he recently visited

to provide an insight into their operations and research.

These include the Keck Observatory in Mauna Kea, Ha-

waii; and the European Southern Observatory and Ata-

cama Large Millimeter Array in the Atacama Desert,

Chile.

More importantly, however, this topic provides an ideal

vehicle to discuss important principles of science and

observational astronomy. An easy to understand expla-

nation of the full spectrum of light followed by how the

atmosphere affects the various wavelengths, will clearly

illustrate why remote and elevated locations are best

for these and future telescopes.

Welcome to New Members

Astrophotography Group, October 21, 7:00pm

Where a viable location exists, a simple home observa-

tory can be a quick and surprisingly inexpensive project,

and greatly improve both results and ability to image

quickly when the sky allows.

Several members who have built or are building home

observatories for astro-photography will give presenta-

tions on their projects, and answer questions.

There will be a particular focus on achieving a good tel-

escope and computer setup for deep sky and planetary

Stevie Katavich-Barton (Ordinary)

Geny Leach (Family)

Tracy-Lee Pettifer. (Family)

Ricardo Bocanegra. (Ordinary)

Introduction to Astronomy, October 7, 8:00pm

Practical Astronomy, October 21, 8:00pm

This month, we will be heading outside with telescopes

to practice our observing skills and how to manually

find objects in the Spring night sky. It will also be a

good time to practice our skills of celestial navigation,

especially with the use of the pipehenge.

Bring your telescopes if you have them and plenty of

warm clothing!

3 WWW.ASTRONOMY.ORG.NZ

The World at Night - Beatrice Hill Tinsley 2019 Lecture

Bridging science, art and culture by connecting the Earth & sky in photography, Babak Tafreshi shares scenes of the night sky from all the continents, an adventurous journey to the world at night.

This talk introduces The World at Night (TWAN), an international program that involves many of the worlds best nightscape photographers documenting the last remaining starry skies on the planet to increase public awareness of the values of the natural night environment for all species.

TWAN is also a bridge between art, humanity, and science, with a unique message. The eternally peaceful sky looks the same above symbols of all nations and regions, attesting to the unified nature of Earth and humanity. One People, One Sky!

Babak A. Tafreshi is a photojournalist and science communicator. The National Geographic night sky photogra-pher, merging art and science, he is also the founder and director of The World At Night program, a board mem-ber of Astronomers Without Borders organization, a contributing photographer to Sky&Telescope magazine and the European Southern Observatory. Born in 1978 in Tehran, Babak lives in Boston, but he is often on the move and could be anywhere.

Large Chemistry Lecture Theatre, Building 301

23 Symonds St

Auckland, Auckland 101

Tickets are free. Please register via the link below.

https://www.eventbrite.co.nz/e/the-world-at-night-public-lecture-by-photojournalist-babak-a-tafreshi-tickets-

74043593381

Saturday 05 October is International Observe the Moon night. The Society is tentatively holding an event at the Viaduct Harbour. Location and time will be confirmed to the outreach volunteers once known.

If you're interested in attending, please contact Niven at events@astronomy.org.nz or on 021 935261.

Alternatively, why not hold an event in your neighbourhood. We'd love to hear about them and can help pro-mote them via our Facebook page.

SOCIETY JOURNAL, October 2019 4

) -

Valley of Stars. Credit: Mark Gee.

5 WWW.ASTRONOMY.ORG.NZ

2019 Burbidge Dinner Advance Notice

Early Bird Pricing Available to 31 October

For example, the most energetic particles ever detected by IceCube in Antarctica, and by telescopes in Namibia

and Argentina, are thought to have been created at the Galactic Centre. Our x-ray and infrared satellites pick up

flaring activity near the black hole each day. The speaker discovered that Sgr A* triggered a huge explosion about

2 million years ago, when cave people walked the Earth; this was recently confirmed by NASA’s Fermi gamma-ray

satellite.

The new ESO Gravity instrument tracks the motion of the closest stars to Sgr A* and detects movement every sin-

gle day! One star even reaches 32,000 km/s at closest approach, 12% of the speed of light. Other stars have es-

caped the Sgr A* region being ejected at speeds of 2000 km/s into the Galaxy. So what does the future hold and

what can we learn from these remarkable observations? We will explore these topics and some crazy ideas.

Joss Hawthorn is one of Australias leading astronomers with the rare distinction of having made important contri-

butions to both astrophysics and technology. He was born in Kent, educated at an Oxford boarding school before

going to university in Birmingham (BSc) and Sussex (PhD). In the period 1985-1993, Joss was an astrophysicist at

the Institute for Astronomy in Hawaii and a professor of physics at Rice University Texas. In 1993, he moved to the

Anglo-Australian Observatory, Sydney, eventually to become Head of the research and development team.

Today, he is the Laureate Fellow Professor of The University of Sydney’s School of Physics, and Director of the Syd-

ney Institute for Astronomy, co-Director of the Institute of Photonics and Optical Science, and Principal Investiga-

tor for the Sydney Astrophotonic Instrumentation Labs. He is a Fellow of the Australian Academy of Science and

the Optical Society of America, serves on the prestigious Annual Reviews of Astronomy & Astrophysics Board, has

published over 700 research papers in astronomy, physics, optics and photonics, and has been recognized with

many international awards (see below), most recently the Miller Professorship to Berkeley (2018).

Joss’ team are building advanced machines, some funded by NASA, that are being installed on the world’s largest

telescopes. In April 2017, one of his creations was launched on an Atlas-V rocket from Cape Canaveral on its way

to the International Space Station, the first Australian university to do so. Joss lives in Mosman by Sydney harbour

with his wife Susan and boys Christian and Luke. He is a jogger, a sculls rower at the North Shore Rowing Club and

plays soccer for Mosman O35. As well as our guest speaker there will be the prize giving for the Astrophotography

Competition including the Harry Williams Trophy for the supreme winner, and the Beaumont Writing Prize. A spec-

tacular venue, great meal, cash bar and ample free parking.

Date: Friday, 22nd November 2019

Venue: Ellerslie Events Centre, Pakuranga Hunt Room Start Time: 7:00pm (doors open at 6:30pm)

Tickets: $65 pp, earlybird price of $60.00 is available until 31st October. Includes a buffet dinner.

Tickets can be booked: - by email at events@astronomy.org.nz - by phone to Niven on 021 935 261 or Bill on 021 225 8175

Our guest speaker this year is: Professor Joss Bland-Hawthorn, (Director, Sydney in-

stitute of Astronomy, University of Sydney). His talk will be: “The Galactic Centre—A

Window into the Future”

The centre of our Galaxy harbours a massive black hole Sgr A* that is likely to be the

oldest component of the Galaxy along with the invisible dark matter around it. How

this amazing object came into existence and evolved over 13 billion years is intimate-

ly linked to the nature of the first stars, the chemical elements today and the evolu-

tion of dark matter and gas. Sgr A* is one of the fastest developing fields in astro-

physics where discoveries are made every year.

SOCIETY JOURNAL, October 2019 6

F or the first time, NASA’s plan-

et-hunting Transiting Exoplan-

et Survey Satellite (TESS) watched a

black hole tear apart a star in a cata-

clysmic phenomenon called a tidal

disruption event. Follow-up obser-

vations by NASA’s Neil Gehrels Swift

Observatory and other facilities

have produced the most detailed

look yet at the early moments of

one of these star-destroying occur-

rences.

“TESS data let us see exactly when

this destructive event, named

ASASSN-19bt, started to get bright-

er, which we’ve never been able to

do before,” said Thomas Holoien, a

Carnegie Fellow at the Carnegie Ob-

servatories in Pasadena, California.

“Because we identified the tidal

disruption quickly with the ground

-based All-Sky Automated Survey

for Supernovae (ASAS-SN), we

were able to trigger multiwave-

length follow-up observations in

the first few days. The early data

will be incredibly helpful for mod-

eling the physics of these out-

bursts.”

A paper describing the findings,

led by Holoien, was published in

the Sept. 27, 2019, issue of The

Astrophysical Journal.

ASAS-SN, a worldwide network of

20 robotic telescopes headquar-

tered at Ohio State University

(OSU) in Columbus, discovered the

event on Jan. 29. Holoien was

working at the Las Campanas Obser-

vatory in Chile when he received the

alert from the project’s South Africa

instrument. Holoien quickly trained

two Las Campanas telescopes on

ASASSN-19bt and then requested

follow-up observations by Swift,

ESA’s (European Space Agency’s)

XMM-Newton and ground-based 1-

meter telescopes in the global Las

Cumbres Observatory network.

TESS, however, didn’t need a call to

action because it was already look-

ing at the same area. The planet

hunter monitors large swaths of the

sky, called sectors, for 27 days at a

time. This lengthy view allows TESS

to observe transits, periodic dips in

a star’s brightness that may indicate

NASA’s TESS Mission Spots Its 1st Star-shredding

Black Hole

Source: NASA

This illustration shows a tidal disruption, which occurs when a passing star gets too close to a black hole and is torn

apart into a stream of gas. Some of the gas eventually settles into a structure around the black hole called an accre-

tion disk. Credit: NASA's Goddard Space Flight Center

7 WWW.ASTRONOMY.ORG.NZ

orbiting planets.

ASAS-SN began spending more time

looking at TESS sectors when the

satellite started science operations

in July 2018. Astronomers anticipat-

ed TESS could catch the earliest

light from short-lived stellar out-

bursts, including supernovae and

tidal disruptions. TESS first saw

ASASSN-19bt on Jan. 21, over a

week before the event was bright

enough for ASAS-SN to detect it.

However, the satellite only trans-

mits data to Earth every two weeks,

and once received they must be

processed at NASA’s Ames Re-

search Center in Silicon Valley, Cali-

fornia. So the first TESS data on the

tidal disruption were not available

until March 13. This is why obtain-

ing early follow-up observations of

these events depends on coordina-

tion by ground-based surveys like

ASAS-SN.

Fortunately, the disruption also oc-

curred in TESS’s southern continu-

ous viewing zone, which was always

in sight of one of the satellite’s four

cameras. (TESS shifted to monitor-

ing the northern sky at the end of

July.) ASASSN-19bt’s location al-

lowed Holoien and his colleagues to

follow the event across several sec-

tors. If it had occurred outside this

zone, TESS might have missed the

beginning of the outburst.

“The early TESS data allow us to see

light very close to the black hole,

much closer than we’ve been able

to see before,” said Patrick Vallely,

a co-author and National Science

Foundation Graduate Research Fel-

low at OSU. “They also show us that

ASASSN-19bt’s rise in brightness

was very smooth, which helps us

tell that the event was a tidal dis-

ruption and not another type of

outburst, like from the center of a

galaxy or a supernova.”

Holoien’s team used UV data from

Swift — the earliest yet seen from

a tidal disruption — to determine

that the temperature dropped by

about 50%, from around 40,000 to

20,000 degrees Celsius, over a few

days. It’s the first time such an ear-

ly temperature decrease has been

seen in a tidal disruption before,

although a few theories have pre-

dicted it, Holoien said.

More typical for these kinds of

events was the low level of X-ray

emission seen by both Swift and

XMM-Newton. Scientists don’t

fully understand why tidal disrup-

tions produce so much UV emis-

sion and so few X-rays.

“People have suggested multiple

theories — perhaps the light

bounces through the newly creat-

ed debris and loses energy, or

maybe the disk forms further from

the black hole than we originally

thought and the light isn’t so

affected by the object’s extreme

gravity,” said S. Bradley Cenko,

Swift’s principal investigator at

NASA’s Goddard Space Flight Cen-

ter in Greenbelt, Maryland. “More

early-time observations of these

events may help us answer some

of these lingering questions.”

Astronomers think the supermas-

sive black hole that generated

ASASSN-19bt weighs around 6 mil-

lion times the Sun’s mass. It sits at

the center of a galaxy called

2MASX J07001137-6602251 locat-

ed around 375 million light-years

away in the constellation Volans.

The destroyed star may have been

similar in size to our Sun.

Tidal disruptions are incredibly

rare, occurring once every 10,000

to 100,000 years in a galaxy the

size of our own Milky Way. Super-

novae, by comparison, happen

every 100 years or so. In total, as-

tronomers have observed only

about 40 tidal disruptions so far,

and scientists predicted TESS would

see only one or two in its initial two

-year mission.

“For TESS to observe ASASSN-19bt

so early in its tenure, and in the

continuous viewing zone where we

could watch it for so long, is really

quite extraordinary,” said Padi

Boyd, the TESS project scientist at

Goddard. “Future collaborations

with observatories around the

world and in orbit will help us learn

even more about the different out-

bursts that light up the cosmos.”

TESS is a NASA Astrophysics Explor-

er mission led and operated by MIT

in Cambridge, Massachusetts, and

managed by NASA's Goddard Space

Flight Center. Additional partners

include Northrop Grumman, based

in Falls Church, Virginia; NASA’s

Ames Research Center in Califor-

nia’s Silicon Valley; the Harvard-

Smithsonian Center for Astrophys-

ics in Cambridge, Massachusetts;

MIT’s Lincoln Laboratory; and the

Space Telescope Science Institute in

Baltimore. More than a dozen uni-

versities, research institutes and

observatories worldwide are partic-

ipants in the mission.

NASA's Goddard Space Flight Cen-

ter manages the Swift mission in

collaboration with Penn State in

University Park, the Los Alamos Na-

tional Laboratory in New Mexico

and Northrop Grumman Innovation

Systems in Dulles, Virginia. Other

partners include the University of

Leicester and Mullard Space Sci-

ence Laboratory of the University

College London in the United King-

dom, Brera Observatory and ASI.

SOCIETY JOURNAL, October 2019 8

F or 400 years people have

tracked sunspots, the dark

patches that appear for weeks at a

time on the Sun's surface. They have

observed but been unable to explain

why the number of spots peaks eve-

ry 11 years.

A University of Washington study

published this month in the journal

Physics of Plasmas proposes a mod-

el of plasma motion that would ex-

plain the 11-year sunspot cycle and

several other previously mysterious

properties of the Sun.

"Our model is completely different

from a normal picture of the Sun,"

said first author Thomas Jarboe, a

UW professor of aeronautics and

astronautics. "I really think we're

the first people that are telling you

the nature and source of solar mag-

netic phenomena - how the Sun

works."

The authors created a model based

on their previous work with fusion

energy research. The model shows

that a thin layer beneath the Sun's

surface is key to many of the fea-

tures we see from Earth, like sun-

spots, magnetic reversals and solar

flow, and is backed up by compari-

sons with observations of the Sun.

"The observational data are key to

confirming our picture of how the

Sun functions," Jarboe said.

In the new model, a thin layer of

magnetic flux and plasma, or free-

floating electrons, moves at differ-

ent speeds on different parts of the

Sun. The difference in speed be-

tween the flows creates twists of

magnetism, known as magnetic

helicity, that are similar to what

happens in some fusion reactor

concepts.

"Every 11 years, the Sun grows this

layer until it's too big to be stable,

and then it sloughs off," Jarboe

said. Its departure exposes the low-

er layer of plasma moving in the

opposite direction with a flipped

magnetic field.

When the circuits in both hemi-

spheres are moving at the same

speed, more sunspots appear.

When the circuits are different

speeds, there is less sunspot activi-

ty. That mismatch, Jarboe says,

may have happened during the

decades of little sunspot activity

known as the "Maunder Mini-

mum."

"If the two hemispheres rotate at

different speeds, then the sunspots

near the equator won't match up,

and the whole thing will die," Jar-

boe said.

"Scientists had thought that a sun-

spot was generated down at 30

percent of the depth of the Sun,

and then came up in a twisted rope

of plasma that pops out," Jarboe

said. Instead, his model shows that

the sunspots are in the

"supergranules" that form within

the thin, subsurface layer of plas-

ma that the study calculates to be

roughly 150 to 450 kilometres

thick, or a fraction of the Sun's

692000-kilometre radius.

"The sunspot is an amazing thing.

There's nothing there, and then all

of a sudden, you see it in a flash,"

Jarboe said.

The group's previous research has

focused on fusion power reactors,

which use very high temperatures

similar to those inside the Sun to

separate hydrogen nuclei from their

electrons. In both the Sun and in

fusion reactors the nuclei of two

hydrogen atoms fuse together, re-

leasing huge amounts of energy.

The type of reactor Jarboe has fo-

cused on, a spheromak, contains the

electron plasma within a sphere that

causes it to self-organize into certain

patterns. When Jarboe began to

consider the Sun, he saw similari-

ties, and created a model for what

might be happening in the celestial

body.

"For 100 years people have been

researching this," Jarboe said.

"Many of the features we're seeing

are below the resolution of the

models, so we can only find them in

calculations."

Other properties explained by the

theory, he said, include flow inside

the Sun, the twisting action that

leads to sunspots and the total mag-

netic structure of the Sun. The pa-

per is likely to provoke intense dis-

cussion, Jarboe said.

"My hope is that scientists will look

Plasma Flow Near Sun’s Surface Explains Sunspots

and Other Solar Phenomena

Source: University of Washington

9 WWW.ASTRONOMY.ORG.NZ

at their data in a new light, and

the researchers who worked their

whole lives to gather that data will

have a new tool to understand

what it all means," he said.

The research was funded by the

U.S. Department of Energy. Co-

authors are UW graduate students

Thomas Benedett, Christopher

Everson, Christopher Hansen,

Derek Sutherland, James Penna,

UW postdoctoral researchers Aa-

ron Hossack and John Benjamin

O'Bryan, UW affiliate faculty mem-

ber Brian Nelson, and Kyle Morgan,

a former UW graduate student

now at CTFusion in Seattle.

Solar Maximum on 19.10.2014 with an X1 flare and active Sun with sunspots, filaments and prominences .

Credit: Otto Gruebl, AAS member

SOCIETY JOURNAL, October 2019 10

S aturn is so beautiful that as-

tronomers cannot resist using

the Hubble Space Telescope to

take yearly snapshots of the ringed

world when it is at its closest dis-

tance to Earth.

These images, however, are more

than just beauty shots. They reveal

a planet with a turbulent, dynamic

atmosphere. This year's Hubble

offering, for example, shows that a

large storm visible in the 2018

Hubble image in the north polar

region has vanished. Smaller

storms pop into view like popcorn

kernels popping in a microwave

oven before disappearing just as

quickly. Even the planet's banded

structure reveals subtle changes in

colour.

But the latest image shows plenty

that hasn't changed. The mysteri-

ous six-sided pattern, called the

"hexagon," still exists on the north

pole. Caused by a high-speed jet

stream, the hexagon was first dis-

covered in 1981 by NASA's Voyager

1 spacecraft.

Saturn's signature rings are still as

stunning as ever. The image re-

veals that the ring system is tilted

toward Earth, giving viewers a

magnificent look at the bright, icy

structure. Hubble resolves numer-

ous ringlets and the fainter inner

rings.

This image reveals an unprecedent-

ed clarity only seen previously in

snapshots taken by NASA space-

craft visiting the distant planet.

Astronomers will continue their

yearly monitoring of the planet to

track shifting weather patterns

and identify other changes. The

second in the yearly series, this

image is part of the Outer Planets

Atmospheres Legacy (OPAL) pro-

ject. OPAL is helping scientists un-

derstand the atmospheric dynam-

ics and evolution of our solar sys-

tem's gas giant planets.

Saturn’s Rings Shine in Hubble’s Latest Portrait

Source: NASA / Goddard Space Flight Center

The latest view of Saturn from NASA's Hubble Space Telescope captures

exquisite details of the ring system -- which looks like a phonograph record

with grooves that represent detailed structure within the rings - and atmos-

pheric details that once could only be captured by spacecraft visiting the

distant world. Hubble's Wide Field Camera 3 observed Saturn on June 20,

2019, as the planet made its closest approach to Earth, at about 1360 mil-

lion kilometres away. This image is the second in a yearly series of snap-

shots taken as part of the Outer Planets Atmospheres Legacy (OPAL) pro-

ject. OPAL is helping scientists understand the atmospheric dynamics and

evolution of our solar system's gas giant planets. In Saturn's case, astrono-

mers will be able to track shifting weather patterns and other changes to

identify trends. Credit: NASA, ESA, A. Simon (GSFC), M.H. Wong (University

of California, Berkeley) and the OPAL Team

Meeting Broadcasts

The Society is now broadcasting many of its meetings online through our YouTube channel. You can watch the

meetings live or at a later time. Perfect if you are unable to make it to the meeting or would just like to see the

talk again. You can subscribe to our YouTube channel at:

https://www.youtube.com/channel/UC4W5_RJtWZBceOteC-8PTIA

11 WWW.ASTRONOMY.ORG.NZ

reach its closest point, or periheli-

on, on Dec. 8, 2019, at a distance

of about 300 million kilometres.

"The comet's current velocity is

about 150,000 kph, which is well

above the typical velocities of ob-

jects orbiting the Sun at that dis-

tance," said Farnocchia. "The high

velocity indicates not only that the

object likely originated from out-

side our solar system, but also that

it will leave and head back to inter-

stellar space."

Currently on an inbound trajectory,

comet C/2019 Q4 is heading to-

ward the inner solar system and

will enter it on Oct. 26 from above

at roughly a 40-degree angle rela-

tive to the ecliptic plane. That's the

plane in which the Earth and plan-

ets orbit the Sun.

C/2019 Q4 was established as be-

ing cometary due to its fuzzy ap-

pearance, which indicates that the

object has a central icy body that is

producing a surrounding cloud of

dust and particles as it approaches

the Sun and heats up. Its location

in the sky (as seen from Earth) plac-

es it near the Sun, an area of sky

not usually scanned by the large

ground-based asteroid surveys or

NASA's asteroid-hunting NEOWISE

spacecraft.

C/2019 Q4 can be seen with profes-

sional telescopes for months to

come. "The object will peak in

brightness in mid-December and

continue to be observable with

moderate-size telescopes until April

2020," said Farnocchia. "After that,

it will only be observable with larg-

er professional telescopes through

October 2020."

Observations completed by Karen

Meech and her team at the Univer-

sity of Hawaii indicate the comet

nucleus is somewhere between 2

and 16 kilometres in diameter. As-

tronomers will continue collect ob-

servations to further characterize

the comet's physical properties

(size, rotation, etc.) and also contin-

ue to better identify its trajectory.

Newly Discovered Comet is Likely Interstellar Visitor

Source: NASA / JPL

A newly discovered comet has

excited the astronomical com-

munity because it appears to have

originated from outside the solar

system. The object, designated

C/2019 Q4 (Borisov), was discov-

ered on Aug. 30, 2019, by Gennady

Borisov at the MARGO observatory

in Nauchnij, Crimea. The official con-

firmation that comet C/2019 Q4 is

an interstellar comet has not yet

been made, but if it is interstellar, it

would be only the second such ob-

ject detected. The first,

'Oumuamua, was observed and con-

firmed in October 2017.

The new comet, C/2019 Q4, is still

inbound toward the Sun, but it will

remain farther than the orbit of

Mars and will approach no closer to

Earth than about 300 million kilome-

tres.

After the initial detections of the

comet, Scout system, which is locat-

ed at NASA's Jet Propulsion Labora-

tory in Pasadena, California, auto-

matically flagged the object as possi-

bly being interstellar. Davide Far-

nocchia of NASA's Center for Near-

Earth Object Studies at JPL worked

with astronomers and the European

Space Agency's Near-Earth Object

Coordination Center in Frascati, Ita-

ly, to obtain additional observations.

He then worked with the NASA-

sponsored Minor Planet Center in

Cambridge, Massachusetts, to esti-

mate the comet's precise trajectory

and determine whether it originated

within our solar system or came

from elsewhere in the galaxy.

The comet is currently 420 million

kilometres from the Sun and will

Comet C/2019 Q4 as imaged on Hawaii's Big Island on Sept. 10, 2019.

Credit: Canada-France-Hawaii Telescope

SOCIETY JOURNAL, October 2019 12

Artificial Intelligence Probes Dark Matter in the

Universe

Source: Eidgenössische Technische Hochschule (ETH) Zürich

U nderstanding the how our

universe came to be what it

is today and what will be its final

destiny is one of the biggest chal-

lenges in science. The awe-inspiring

display of countless stars on a clear

night gives us some idea of the

magnitude of the problem, and yet

that is only part of the story. The

deeper riddle lies in what we cannot

see, at least not directly: dark

matter and dark energy. With dark

matter pulling the universe together

and dark energy causing it to ex-

pand faster, cosmologists need to

know exactly how much of those

two is out there in order to refine

their models.

At ETH Zurich, scientists from the

Department of Physics and the De-

partment of Computer Science have

now joined forces to improve on

standard methods for estimating

the dark matter content of the uni-

verse through artificial intelligence.

They used cutting-edge machine

learning algorithms for cosmological

data analysis that have a lot in com-

mon with those used for facial

recognition by Facebook and other

social media. Their results have re-

cently been published in the scien-

tific journal Physical Review D.

Facial recognition for cosmology

While there are no faces to be rec-

ognized in pictures taken of the

night sky, cosmologists still look for

something rather similar, as Tomasz

Kacprzak, a researcher in the group

of Alexandre Refregier at the Insti-

tute of Particle Physics and Astro-

physics, explains: "Facebook uses

its algorithms to find eyes, mouths

or ears in images; we use ours to

look for the tell-tale signs of dark

matter and dark energy." As dark

matter cannot be seen directly in

telescope images, physicists rely

on the fact that all matter -- includ-

ing the dark variety -- slightly

bends the path of light rays arriv-

ing at the Earth from distant galax-

ies. This effect, known as "weak

gravitational lensing," distorts the

images of those galaxies very sub-

tly, much like far-away objects ap-

pear blurred on a hot day as light

passes through layers of air at

different temperatures.

Cosmologists can use that distor-

tion to work backwards and create

mass maps of the sky showing

where dark matter is located. Next,

they compare those dark matter

maps to theoretical predictions in

order to find which cosmological

model most closely matches the

data. Traditionally, this is done us-

ing human-designed statistics such

as so-called correlation functions

that describe how different parts

of the maps are related to each

other. Such statistics, however, are

limited as to how well they can

find complex patterns in the

matter maps.

Neural networks teach them-

selves

"In our recent work, we have used

a completely new methodology,"

says Alexandre Refregier. "Instead

of inventing the appropriate statis-

tical analysis ourselves, we let com-

puters do the job." This is where

Aurelien Lucchi and his colleagues

from the Data Analytics Lab at the

Department of Computer Science

come in. Together with Janis Fluri, a

PhD student in Refregier's group

and lead author of the study, they

used machine learning algorithms

called deep artificial neural net-

works and taught them to extract

the largest possible amount of in-

formation from the dark matter

maps.

In a first step, the scientists trained

the neural networks by feeding

them computer-generated data that

simulates the universe. That way,

they knew what the correct answer

for a given cosmological parameter

-- for instance, the ratio between

the total amount of dark matter and

dark energy -- should be for each

simulated dark matter map. By re-

peatedly analysing the dark matter

maps, the neural network taught

itself to look for the right kind of

features in them and to extract

more and more of the desired infor-

mation. In the Facebook analogy, it

got better at distinguishing random

oval shapes from eyes or mouths.

More accurate than human-made

analysis

The results of that training were

encouraging: the neural networks

came up with values that were 30%

more accurate than those obtained

by traditional methods based on

human-made statistical analysis. For

cosmologists, that is a huge im-

13 WWW.ASTRONOMY.ORG.NZ

and is found in the habitable zone

of the star it orbits. This M-type

star is smaller and cooler than our

Sun, but due to K2-18b's close

proximity to its star, the planet

receives almost the same total

amount of energy from its star as

our Earth receives from the Sun.

The similarities between the ex-

oplanet K2-18b and the Earth sug-

gest to astronomers that the ex-

oplanet may potentially have a

water cycle possibly allowing water

to condense into clouds and liquid

water rain to fall. This detection

was made possible by combining

eight transit observations -- the

moment when an exoplanet passes

in front of its star -- taken by the

Hubble Space Telescope.

The Université de Montréal is no

stranger to the K2-18 system locat-

ed 111 light years away. The exist-

ence of K2-18b was first confirmed

by Prof. Benneke and his team in a

2016 paper using data from the

Spitzer Space Telescope. The mass

and radius of the planet were then

determined by former Université

de Montréal and University of To-

ronto PhD student Ryan Cloutier.

These promising initial results en-

couraged the iREx team to collect

follow-up observations of the intri-

guing world."

Scientists currently believe that the

thick gaseous envelope of K2-18b

likely prevents life as we know it

from existing on the planet's sur-

face. However, the study shows that

even these planets of relatively low

mass which are therefore more

difficult to study can be explored

using astronomical instruments de-

veloped in recent years. By studying

these planets which are in the habit-

able zone of their star and have the

right conditions for liquid water,

astronomers are one step closer to

directly detecting signs of life be-

yond our Solar System.

"This represents the biggest step yet

taken towards our ultimate goal of

finding life on other planets, of

proving that we are not alone.

Thanks to our observations and our

climate model of this planet, we

have shown that its water vapour

can condense into liquid water. This

is a first," says Björn Benneke.

provement as reaching the same

accuracy by increasing the number

of telescope images would require

twice as much observation time --

which is expensive.

Finally, the scientists used their fully

trained neural network to analyse

actual dark matter maps from the

KiDS-450 dataset. "This is the first

time such machine learning tools

have been used in this context,"

says Fluri, "and we found that the

deep artificial neural network ena-

bles us to extract more information

from the data than previous ap-

proaches. We believe that this us-

age of machine learning in cosmol-

ogy will have many future applica-

tions."

As a next step, he and his colleagues

are planning to apply their method

to bigger image sets such as the

Dark Energy Survey. Also, more cos-

mological parameters and refine-

ments such as details about the na-

ture of dark energy will be fed to

the neural networks.

Water Detected on an Exoplanet Located in its

Star’s Habitable Zone

Source: Université de Montréal

Ever since the discovery of the first

exoplanet in the 1990s, astrono-

mers have made steady progress

towards finding and probing plan-

ets located in the habitable zone of

their stars, where conditions can

lead to the formation of liquid wa-

ter and the proliferation of life.

Results from the Kepler satellite

mission, which discovered nearly

2/3 of all known exoplanets to

date, indicate that 5 to 20% of

Earths and super-Earths are located

in the habitable zone of their stars.

However, despite this abundance,

probing the conditions and atmos-

pheric properties on any of these

habitable zone planets is extremely

difficult and has remained elusive...

until now.

A new study by Professor Björn

Benneke of the Institute for Re-

search on Exoplanets at the Univer-

sité de Montréal, his doctoral stu-

dent Caroline Piaulet and several of

their collaborators reports the de-

tection of water vapour and per-

haps even liquid water clouds in

the atmosphere of the planet K2-

18b. This exoplanet is about nine

times more massive than our Earth

SOCIETY JOURNAL, October 2019 14

pernova – are the densest

“normal” objects in the known uni-

verse. (Black holes are technically

denser, but far from normal.) Just a

single sugar-cube worth of neutron

-star material would weigh 100

million tons here on Earth, or

about the same as the entire hu-

man population. Though astrono-

mers and physicists have studied

and marveled at these objects for

decades, many mysteries remain

about the nature of their interiors:

Do crushed neutrons become

“superfluid” and flow freely? Do

they breakdown into a soup of sub-

atomic quarks or other exotic parti-

cles? What is the tipping point

when gravity wins out over matter

and forms a black hole?

A team of astronomers using the

Robert C. Byrd Green Bank Tele-

Most Massive Neutron Star Ever Detected, Almost

too Massive to Exist

Source: Green Bank Observatory

A stronomers using the GBT

have discovered the most

massive neutron star to date, a rap-

idly spinning pulsar approximately

4,600 light-years from Earth. This

record-breaking object is teetering

on the edge of existence, approach-

ing the theoretical maximum mass

possible for a neutron star.

Neutron stars – the compressed

remains of massive stars gone su-

Artist impression of the pulse from a massive neutron star being delayed by the passage of a white dwarf star be-

tween the neutron star and Earth. Credit: BSaxton, NRAO/AUI/NSF

15 WWW.ASTRONOMY.ORG.NZ

scope (GBT) has brought us closer to

finding the answers.

The researchers, members of the

NANOGrav Physics Frontiers Center,

discovered that a rapidly rotating

millisecond pulsar, called

J0740+6620, is the most massive

neutron star ever measured, pack-

ing 2.17 times the mass of our Sun

into a sphere only 30 kilometers

across. This measurement ap-

proaches the limits of how massive

and compact a single object can be-

come without crushing itself down

into a black hole. Recent work in-

volving gravitational waves ob-

served from colliding neutron stars

by LIGO suggests that 2.17 solar

masses might be very near that lim-

it.

“Neutron stars are as mysterious as

they are fascinating,” said Thankful

Cromartie, a graduate student at

the University of Virginia and Grote

Reber pre-doctoral fellow at the

NSF’s National Radio Astronomy

Observatory in Charlottesville, Vir-

ginia. “These city-sized objects are

essentially ginormous atomic nuclei.

They are so massive that their interi-

ors take on weird properties. Find-

ing the maximum mass that physics

and nature will allow can teach us a

great deal about this otherwise inac-

cessible realm in astrophysics.”

Pulsars get their name because of

the twin beams of radio waves they

emit from their magnetic poles.

These beams sweep across space in

a lighthouse-like fashion. Some ro-

tate hundreds of times each second.

Since pulsars spin with such phe-

nomenal speed and regularity, as-

tronomers can use them as the cos-

mic equivalent of atomic clocks.

Such precise timekeeping helps as-

tronomers study the nature of

spacetime, measure the masses of

stellar objects, and improve their

understanding of general relativity.

In the case of this binary system,

which is nearly edge-on in relation

to Earth, this cosmic precision pro-

vided a pathway for astronomers

to calculate the mass of the two

stars.

As the ticking pulsar passes behind

its white dwarf companion, there is

a subtle (on the order of 10 mil-

lionths of a second) delay in the

arrival time of the signals. This

phenomenon is known as “Shapiro

Delay.” In essence, gravity from the

white dwarf star slightly warps the

space surrounding it, in accordance

with Einstein’s general theory of

relativity. This warping means the

pulses from the rotating neutron

star have to travel just a little bit

farther as they wend their way

around the distortions of

spacetime caused by the white

dwarf.

Astronomers can use the amount

of that delay to calculate the mass

of the white dwarf. Once the mass

of one of the co-orbiting bodies is

known, it is a relatively straightfor-

ward process to accurately deter-

mine the mass of the other.

Cromartie is the principal author

on a paper accepted for publica-

tion in Nature Astronomy. The GBT

observations were research related

to her doctoral thesis, which pro-

posed observing this system at two

special points in their mutual orbits

to accurately calculate the mass of

the neutron star.

“The orientation of this binary star

system created a fantastic cosmic

laboratory,” said Scott Ransom, an

astronomer at NRAO and coauthor

on the paper. “Neutron stars have

this tipping point where their interior

densities get so extreme that the

force of gravity overwhelms even the

ability of neutrons to resist further

collapse. Each “most massive” neu-

tron star we find brings us closer to

identifying that tipping point and

helping us to understand the physics

of matter at these mindboggling den-

sities.”

These observation were also part of

a larger observing campaign known

as NANOGrav, short for the North

American Nanohertz Observatory for

Gravitational Waves, which is a Phys-

ics Frontiers Center funded by the

NSF.

The National Radio Astronomy Ob-

servatory is a facility of the National

Science Foundation, operated under

cooperative agreement by Associat-

ed Universities, Inc.

The Green Bank Observatory is sup-

ported by the National Science Foun-

dation, and is operated under coop-

erative agreement by Associated

Universities, Inc. Any opinions, find-

ings and conclusions or recommen-

dations expressed in this material do

not necessarily reflect the views of

the National Science Foundation.

SOCIETY JOURNAL, October 2019 16

The society has a wide variety of equipment available to rent to members. The range of scopes go from the beginner Dobsonian telescopes through to the advanced computerised GOTO systems. All rental equipment is of high quality and regularly maintained.

Rental periods are typically 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 ad-vice if equipment is suitable for your needs, or experience level.

8” Astronz Dobsonian Telescope $10/week

Celestron Nexstar 5 127mm SCT Alt/Az Goto Telescope $12.5/week

iOptron Minitower Alt/Az with Celestron C5 OTA $12.50/week

iOptron ZEQ25 GOTO Equatorial Mount with Celestron C8 $15/week

Meade LX-10 200mm Schmidt Cassegrain $10/week

Coronado PST 40mm Hydrogen-Alpha Solar Telescope $10/week

iOptron Skytracker $10/week

20x80 Binocular $7.50/week

We are often adding items to our rental equipment, and we are really keen to hear what other items may be useful to members. Any ideas of for any information regarding availability or how to rent equipment, please contact:

Curator of Instruments -Steve Hennerley on 027 2456441 or Darren Woodley on 021 776481

rental@astronomy.org.nz

17 WWW.ASTRONOMY.ORG.NZ

The Evening Sky in October 2019

By Alan Gilmore

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

www.canterbury.ac.nz

Four planets light up the western evening sky. The brightest is Venus, appearing low in the west soon after sunset. It sets an hour after the Sun at the beginning of the month, nearly two hours after the Sun at the end.

Above Venus is Mercury. It is much fainter than Venus but still a bright 'star'. It falls level with Venus at the end of the month. Midway down the western sky is golden Jupiter, the brightest 'star' after Venus. Jupiter sets in the southwest around midnight. Well above Jupiter is cream-coloured Saturn, fainter then Jupiter but still the brightest 'star' in its part of the sky.

Mercury and Venus are small in a telescope. Venus is on the far side of the Sun, 240 million km away mid-month. Mercury appears as a tiny disk at first. It will become a little bigger and crescent-shaped as it moves to our side of the Sun. The thin crescent Moon will pass by Mercury and Venus on the 29th and 30th.

Jupiter and Saturn are much more interesting in telescopes. Even a small telescope shows Jupiter's disk. Larger 'scopes will show the parallel bands across Jupiter caused by temperature differences in its clouds. Jupiter's four big moons are lined up on either side of the planet, swapping positions from night to night. Jupiter is 850 million km from us mid-month and Saturn 1510 million km away. The Moon will be near Jupiter on the 3rd and 4th and near Saturn on the 5th and 6th.

Antares marks the body of the Scorpion. The Scorpion's tail loops up the sky in the evening, making a back-to-front question mark with Antares being the dot. The curved tail is 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. Red giants are dying stars, wringing the last of the thermo-nuclear energy from their cores. Above and 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. Saturn is near the teapot's handle.

Canopus is low in the southeast at dusk often twinkling colourfully. It swings up into the eastern sky during the night. Canopus is 13 000 times the Sun's brightness and 300 light years away. On the north skyline is Vega, setting in the early evening. It is 50 times brighter than the Sun, 25 light years away and the 5th brightest star in the sky.

In the southwest are 'The Pointers ', Beta and Alpha Centauri, making a vertical pair. They point down to Crux the Southern Cross. Alpha Centauri, the top Pointer, is the closest naked eye star at 4.3 light years away. Beta Centauri is a blue-giant star, very hot and very luminous, hundreds of light years away.

The Milky Way is brightest and broadest in Scorpius and Sagittarius. In a dark sky it can be traced down to the south. In the north it meets the skyline right of Vega. From northern New Zealand the star Deneb can be seen near the north skyline in the Milky Way. It is the brightest star in Cygnus the Swan. 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, with a black hole four million times the Sun's mass, is hidden by dust clouds in space. Its direction is a little outside the Teapot's spout. The nearer 'interstellar' clouds appear as gaps and slots in the Milky Way. The dust and gas has come from old stars that have thrown much of their material back into space as they faded or blew up. New stars eventually condense from this stuff. A scan along the Milky Way with binoculars shows many clusters of new stars and some glowing clouds of left-over gas. There are many in Scorpius and Sagittarius and in the Carina region.

The Large and Small Clouds of Magellan, LMC and SMC, look like two misty patches of light in the southeast sky. They are easily seen by eye on a dark moonless night. They are galaxies like our Milky Way but much smaller. The Large Cloud is about 5% the mass of our Galaxy and the small one 3%. That is still many billions of stars in each. The LMC is around 160 000 light years away; the SMC around 200 000 l.y.

On moonless evenings in a dark rural sky the Zodiacal Light is visible in the west. It looks like late twilight: a faint broad column of light around Venus and Mercury, fading out at the Milky Way. It is sunlight reflecting off meteoric dust in the plane of the solar system. The dust may have come from a big comet, centuries ago.

*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 to reach the nearest star, Alpha Centauri.

SOCIETY JOURNAL, October 2019 18

The Night Sky for October 2019

19 WWW.ASTRONOMY.ORG.NZ

Solar System Events for October 2019

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

October 2 Pluto stationary

October 3 Jupiter 1.8° south of the Moon

October 3 Venus 2.9° north of Spica

October 5 Moon first quarter

October 5 Moon southern most declination (-22.8°)

October 5 Saturn 0.3° north of the Moon Occn

October 6 Pluto 0.1° north of the Moon Occn

October 10 Moon at apogee

October 11 Neptune 3.4° north of the Moon

October 13 Moon full

October 15 Uranus 4.1° north of the Moon

October 17 Aldebaran 2.8° south of the Moon

October 19 Mercury greatest elong E(25)

October 20 Moon northern most declination (22.9°)

October 21 Pollux 5.6° north of the Moon

October 21 Moon last quarter

October 23 Regulus 3.3° south of the Moon

October 26 Moon at perigee

October 26 Mars 4.1° south of the Moon

October 28 Moon new

October 28 Uranus at opposition

October 29 Venus 3.7° south of the Moon

October 30 Mercury 2.6° south of Venus

October 31 Jupiter 1.3° south of the Moon

October 31 Mercury stationary

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