southern sentinel crossword society march 2008 edition … · fred is the author of "stargazer...

AAS Journal 32 March 2008

The solutions to the February crossword are on page 12

Southern Sentinel Crossword March 2008 Edition

Across

5 Proper name for double star Beta

Cygni (7)

6 Brightest Star in Auriga (7)

8 Moon of Saturn (5)

9 A Type K star is what colour? (6)

10 A dark blemish on the surface of the sun which is cooler than the surround-

ing regions (7)

12 Technique for observing faint objects by using the more sensitive rods on the

retina (7,6)

Down

1 The constellation 'The Serpent' (7)

2 The Great 1700's Comet Hunter (7,7)

3 Common name for Epsilon Carinae a

member of the False Cross (5)

4 A unit of angular measure equal to

1/3600th of a degree (3,6)

7 The instant at which the top of the set-

ting Sun's disk disappears below the

horizon (6)

11 The elliptical path of an object that is gravitationally bound to another object

(5)

1 2 3

4 5

6 7

8

9

10 11

12

Visit our web site: www.astronomy.org.nz

SOCIETY JOURNAL

March 2008

The Burbidge Dinner!


President: Henk Stolk 0274 878655

Vice President: John White 486-2398

Treasurer: Helen McRae 021 494418

Secretary: Jennie McCormick 576-9815

Curator of Instruments: Ivan Vazey 535-3987

Librarian: Olga Brochner 625-9444

Editor:

Councillor: Mark Cannell 520-1123

Councillor: Andrew Goodfellow 524-4369

Councillor/Webmaster: Nick Moore 537-1500

THE SOCIETY COUNCIL

JOURNAL OF THE

AUCKLAND ASTRONOMICAL SOCIETY

The aim of this publication is to promote and foster the science of astronomy, and to encourage the association of astronomical observers and other persons interested in astronomy.

11 issues per year.

Auckland Astronomical Society, Inc.,

P O Box 24-187 Royal Oak, Auckland 1345, New Zealand

Email : [email protected]

Internet : www.astronomy.org.nz

Contact Us :

March 2008 31 AAS Journal


Institute of Aerospace Medicine (Kon, Germany), Humboldt University of Berlin,

Heinrich-Heine University (Dusseldorf, Germany), Ernst-Mach Institute for Short-Term

Dynamics (Freiberg, Germany), Open University (Milton Keynes, U.K.), the German

Collection of Microorganism and Cell Cultures (Braunschweig, Germany), the Russian

Academy of Science (Moscow), and the Planetary Science Institute (Tucson, AZ).

"Given that impacts have occurred on planetary bodies throughout the history of our solar

system," says journal Editor, Sherry L. Cady, PhD, Associate Professor in the Depart-

ment of Geology at Portland State University, "the hypothesis that life in rock could have

been transferred between planets at different times during the past 3.5 billion years is

plausible. These experiments advance our understanding of the constraints on life's abil-

ity to survive the magnitude of impact that would accompany a meteoric trip from Mars

to Earth."

Large impacts by asteroids make possible the transfer of living organisms from one

planet to another—or the reseeding of Earth by much older organisms


2008 Burbidge Dinner MONDAY 10th MARCH 2008

6.30pm Bucklands Beach Yacht Club

Friends and visitors are welcome.

Fred is the author of "Stargazer - the life and times

of the telescope", and is a regular broadcaster on

ABC radio.

His new book "Why is Uranus upside down?" is

based on listener questions, and was published in

October 2007.

In 2003, Fred received the David Allen Prize for

communicating astronomy to the public, and in

2006 was the winner of the Australian Govern-

ment Eureka Prize for Promoting Understanding

of Science.

Fred has an asteroid named after him (5691 Fred-

watson), but says that if it hits the Earth it won't be

his fault…

“Astronomers Behaving Badly”

Special Guest Speaker

Fred Watson Anglo-Australian Observatory


Calendar of Society Events

March 2008 Fri 7 7.30pm Young Astronomers (Margaret Arthur)

Mon 10 6.30pm Burbidge Dinner (see pages 3 & 6)

Fri 14 7.30pm Night Eyes “Dancing with the Stars” (David Britten) - page 5

Mon 24 8.00pm Introduction to Astronomy (Henk Stolk) - see page 12

April 2008

Fri 4-6 Waharau Dark Sky Weekend

Sun 6 3.00am Daylight Savings ends

Mon 21 7.30pm Annual General Meeting (see page 7)

TEMPORARY RE-LOCATION The planetarium system at Stardome is being upgraded (see below).

While this is happening, there won't be any rooms available for Society

meetings, so we're moving down the road

.

Until further notice, all meetings will be held in the Epsom Methodist Church Hall, corner of Manukau Rd

and Pah Rd , Greenwoods Corner, Auckland.


and possibly even to survive the Sun's red giant phase.

"This sounds like science fiction," says Professor Smith. "But it seems that

the energy requirements are just about possible and the technology could be

developed over the next few centuries." However, it is a high-risk strategy

-- a slight miscalculation, and the asteroid could actually hit the Earth,

with catastrophic consequences. "A safer solution may be to build a fleet of

interplanetary 'life rafts' that could manoeuvre themselves always out of

reach of the Sun, but close enough to use its energy," he adds.

New Rochelle, February 26, 2008

I n the event that an asteroid or comet would impact Earth and send rock fragments

containing embedded microorganisms into space, at least some of those organisms

might survive and reseed on Earth or another planetary surface able to support life,

according to a study published in the Spring 2008 (Volume 8, Number 1) issue of Astro-

biology.

In the report entitled, "Microbial Rock Inhabitants Survive Hypervelocity Impacts on

Mars-like Host Planets: First Phase of Lithopanspermia Experimentally Tested", Gerda

Horneck and colleagues describe systematic shock recovery experiments designed to

simulate a scenario called lithopanspermia, in which microorganisms are transported be-

tween planets via meteorites. The first step of lithopanspermia would involve ejection of

the microorganism-containing rock from the host planet as a result of an impact event.

The researchers sandwiched dry layers of three kinds of biological test systems, including

bacterial endospores, endolithic cyanobacteria, and epilithic lichens, between gabbro

discs, which are analogous to martian rocks. They then simulated the shock pressures

martian meteorites experienced when they were ejected from Mars and determined the

ability of the organisms to survive the harsh conditions.

The organisms selected represent "potential 'hitchhikers' within impact-ejected rocks,"

explain the authors, and are hardy examples of microbes that can withstand extreme envi-

ronmental stress conditions, write the authors.

The results support the potential for rocks ejected on asteroidal impact to carry microor-

ganisms capable of reseeding the Earth, according to Horneck and coworkers, from the

Life Forms Ejected on Asteroid Im-pact Could Survive to Reseed Earth


University of Sussex

21 February 2008

N ew calculations by University of Sussex astronomers predict that the Earth

will be swallowed up by the Sun in about 7.6 billion years unless the

Earth's orbit can be altered.

Dr Robert Smith, Emeritus Reader in Astronomy, said his team previously

calculated that the Earth would escape ultimate destruction, although be

battered and burnt to a cinder. But this did not take into account the

effect of the drag caused by the outer atmosphere of the dying Sun.

He says: "We showed previously that, as the Sun expanded, it would lose mass

in the form of a strong wind, much more powerful than the current solar

wind. This would reduce the gravitational pull of the Sun on the Earth,

allowing the Earth's orbit to move outwards, ahead of the expanding Sun.

"If that were the only effect the Earth would indeed escape final

destruction. However, the tenuous outer atmosphere of the Sun extends a long

way beyond its visible surface, and it turns out the Earth would actually be

orbiting within these very low density outer layers. The drag caused by this

low-density gas is enough to cause the Earth to drift inwards, and finally

to be captured and vaporised by the Sun."

The new paper was written in collaboration with Dr Klaus-Peter Schroeder,

previously at Sussex, who is now in the Astronomy Department of the

University of Guanajuato in Mexico.

Life on Earth will have disappeared long before 7.6 billion years, however.

Scientists have shown that the Sun's slow expansion will cause the

temperature at the surface of the Earth to rise. Oceans will evaporate, and

the atmosphere will become laden with water vapour, which (like carbon

dioxide) is a very effective greenhouse gas. Eventually, the oceans will

boil dry and the water vapour will escape into space. In a billion years

from now the Earth will be a very hot, dry and uninhabitable ball.

Can anything be done to prevent this fate? Professor Smith points to a

remarkable scheme proposed by a team at Santa Cruz University, who suggest

harnessing the gravitational effects of a close passage by a large asteroid

to "nudge" the Earth's orbit gradually outwards away from the encroaching

Sun. A suitable passage every 6000 years or so would be enough to keep the

Earth out of trouble and allow life to survive for at least 5 billion years,

The Sun will vaporise the Earth unless we can change our orbit


Waharau Dates for 2008 Here are the Waharau dark sky dates for your 2008 diary.

Friday April 4th

Friday July 4th

Friday September 26th

We hope to see you all there.

Society News

NIGHT EYES March Meeting

The March meeting of the Night Eyes junior group will be held at 7:30pm on Friday 14

March - one week early this year because of long Easter weekend.

As the Observatory Sun Room is not available due to the renovations, the March meeting

will be held in the Epsom Methodist Church Hall, 587 Manukau Rd, near Greenwood's

Corner. This is just up the road from the Observatory before you get to the lights, and

there is parking on Manukau Rd and on Pah Rd.

The main topic for the meeting will be:

" Dancing with the Stars "

Parents, friends and other Society members are also very welcome to attend. For further

information please contact David Britten at [email protected] (ph. 846-3657).

Library update

As you have gathered, the Stardome is having an overhaul, so at present we do not really

have the same ease of access to the Auckland Astronomical Society book collection.

However, fear not, If you have web access you can see the list of the Society’s books on

the AAS’s web page. Then if you want to borrow a book / magazine or return any, just

give me a call and we will arrange access with the help of the Society’s Vice President

John White.

My phone contact is: 09 6259 444. Also there are a few books that we have doubles of,

so these will be up for sale to Society members at club nights. So come along and see

what you can get.


Burbidge Dinner

Bucklands Beach Yacht Club Half Moon Bay Marina Ara Tai, Off Pigeon Mountain Road Half Moon Bay http://www.bbyc.org.nz Monday 10 March 2008 6.30pm Arrival and pre dinner drinks 7.30pm Seated for buffet dinner 9.00pm After dinner guest speaker $60 per person

The speaker at the Burbidge dinner will be Dr Fred Watson. Fred is As-

tronomer-in-Charge of the Anglo-Australian Observatory (AAO) at Sid-

ing Spring near Coonabarabran, NSW. He has worked extensively on the

programme of sky surveys at the AAO and has received a lot of recogni-

tion and awards for communicating astronomy to the public.

He is an exceptional speaker.

A cash bar will be available throughout the evening.

The following awards will be presented at the dinner:

• The 2008 Beaumont Prize for writing

• The 2008 Harry Williams Trophy for astrophotography

For more information contact:

Jennie McCormick, Phone: 09 576-9815; Cell: 021-1747532

Email: [email protected]

We would like to acknowledge Astronz for sponsoring this event

Astronomy New Zealand Limited, PO Box 39-496, Howick,

Auckland email [email protected]

www.astronomy.co.nz


Posted by Kelly Beatty, February 14, 2008

Sky & Telescope

T wo days ago the IAU's quaintly named Central Bureau for Astronomical Tele-

grams announced that astronomers have discovered a triple asteroid passing in

Earth's vicinity.

This isn't the first rock trio — out in the main asteroid belt, 87 Sylvia has two small

moons (Romulus and Remus) and so does 45 Eugenia (Petit-Prince and another desig-

nated S/2004 (45) 1). Multiple asteroids are no longer big news. Based on the terrestrial

cratering record, about one in six impacts with Earth involves a double object.

But this one is a rather different animal. First, it's in an Amor-type orbit, meaning that it

comes to within 96.4 million miles of the Sun but doesn't quite cross the orbit of Earth.

Second, its three components are rather similar in size. The main body is roughly 1½

miles (2 km) across, whereas the other two are closer to 1,000 feet (300 meters).

The threesome came to light because a team headed by Cornell astronomer Mike Nolan

used the Arecibo radio telescope in Puerto Rico to bounce radar pulses off a small aster-

oid passing within about 7 million miles of Earth. When three echoes came back on

Tuesday, Nolan knew they'd found something special. (see image opposite)

First seen in September 2001, this object has two official designations: 2001 SN263 (its ID

when discovered) and 153591 (assigned once its orbit was known well). But this alpha-

numeric jumble gets worse: according to IAU convention, for now the two little satellites

will be known as S/2008 (153591) 1 and S/2008 (153591) 2. Can't we just call them Moe,

Larry, and Curly and be done with it?

Nolan notes in a press release that not much is known about the trio. But more observa-

tions in the coming days might determine whether the moonlets are orbiting in the same

plane, the masses of all three objects, and whether the trio formed in the asteroid belt or

due to a close brush with Earth.

Because it's in a near-Earth orbit, breakup specialist Derek Richardson (University of

Maryland) thinks 2001 SN263 could have been ripped apart by Earth's gravity in the not-

too-distant past. "You need to get within 4 Earth radii or so [about 15,000 miles or 25,000

km] for anything interesting to happen."

He doesn't think the breakup occurred in the asteroid belt, citing the unlikelihood of the

threesome staying intact for the millions of years it would have taken to migrate inward.

Nor does he think subtle solar forces caused it to spin so rapidly that it flew apart.

A Triple Threat


The new study, which has been submitted to Meteoritics and Planetary Science, con-

cludes that up to 5% of this high-speed debris from Mercury reaches Earth — a third to a

half of the delivery rate of meteorites from Mars. Gladman notes that roughly a half

dozen samples of Mercury might already be sitting in meteorite collections worldwide.

But how would an interplanetary prospector recognize that a stone really is from the in-

nermost planet? Some planetary geologists think a rare class of meteorites called angrites

might be good candidates, though others disagree. Gladman cautions, "Until you have

some kind of ground truth, it's very difficult to make those claims." He says scientists

need more information about the composition of Mercury's surface to find matches with

suspicious meteorites.

Fortunately, the Messenger spacecraft has begun exploring the planet. Messenger flew

past Mercury in January and will go into orbit in 2011. It should provide the data that will

confirm or refute candidate meteorites from Mercury.

Ken Croswell is the author of Ten Worlds: Everything That Orbits the Sun (Boyds Mills

Press, 2006).

A visualization of the radar echoes acquired February 13, 2008, from asteroid 2001

SN263. Radar illumination is from the top. Echoes from the two satellites appear thinner

because they are rotating slowly and therefore don't produce as much Doppler shifting

(horizontal axis) as the main mass.

National Astronomy and Ionosphere Center


Annual General Meeting

Monday, 21 April 2008 at 7.30pm Auckland Stardome Observatory

One Tree Hill Domain

The 82nd Annual General Meeting of the Auckland Astronomical Society, Inc. will be

held on Monday 21 April, 2008.

We encourage our members to attend and support this meeting and if you have time to

spare, to think seriously about standing as a Councilor this year. All positions are open

for nomination.

We are looking for members interested in giving a few hours of their time each month to

be part of the team and help bring forward fresh approaches and new ideas to our ever-

growing Society.

To be elected to Council you must have been a financial member for one year prior to the

AGM. If you feel you may be interested, for further information please contact either

• Henk Stolk—President (0274) 878-655 or

• Jennie McCormick - Secretary (021) 174-7532

The agenda will include:

• presentation of reports

• election of officers and Council members

• general business

A nomination form for officers and Council members is included in this month's

distribution of the Journal.

Light refreshments will be available after the meeting.


The Night Sky for March

Brian Loader RASNZ

Diary of Solar System Events Date (NZDT)

———————————————————————————————————

March 3 25% Moon 5° from Jupiter. Moon also occults star Nunki, σ Sgr, magni-

tude 2.1 near dawn.

March 4 Mercury at greatest elongation 27° west of Sun.

March 6 4.5% lit crescent Moon 0.5° from Venus, 1.5° from Neptune and 2.6° from

Mercury in the morning sky.

March 7 Venus, less than 40' from Neptune, morning sky.

March 8 New Moon at 6:14 pm NZDT (Mar 7, 17:14 UT).

March 9 Uranus at conjunction.

March 9/10 Mercury just over 1° from Neptune, morning sky.

March 14 Moon at first quarter 11:46 pm NZDT (10:46 UT).

March 16 60% lit Moon 3.5° from Mars magnitude 0.5, evening sky.

March 19 94% lit Moon less than 3° from Saturn. Also Regulus, magnitude 1.4 is

occulted by the Moon, disappearing shortly before sunset, and reappearing

soon after.

March 20 Southern autumnal equinox at 6:48 pm NZDT as Sun crosses celestial

equator moving north.

March 22 Full Moon at 7:40 am NZDT (Mar 21, 18:40 UT).

March 23/24 97% lit Moon 3° from star Spica, magnitude 1.1, evening sky, closing in to

2° on early morning of 24th.

March 25 Venus and Mercury 1° apart, low in dawn sky.

March 27 Moon at apogee, its greatest distance from the Earth for the Lunar month,

405,095 km.

March 27 73% lit Moon less than 1° from star Antares, late evening sky. At Moon

rise Antares is occulted for places north of a line from New Plymouth to

Dannevirke.

March 28 Venus, Mercury and Uranus all about 1.6° apart forming a triangle in

dawn sky, with Vesta close by.

March 30 Moon at last quarter 10:47 am NZDT (Mar 29, 21:47 UT).

March 31 42% lit Moon less than 3° from Jupiter in morning sky.

From Brian Loader's monthly solar system notes on the RASNZ web site. Bookmark

Brian’s excellent site www.rasnz.org.nz for more detail and many useful links


From Sky & Telescope, February 15, 2008

M eteorites from the Moon and Mars give earthbound scientists free rock samples

from other worlds. Now Brett Gladman and Jaime Coffey (University of Brit-

ish Columbia, Vancouver) say we should expect a few meteorites from Mer-

cury too.

Gladman and Coffey conducted computer simulations of what happens after asteroids

and comets slam into the innermost planet and kick debris into space. Past studies as-

sumed that rocks knocked off Mercury weren't getting away with much more than its

escape velocity of 4.2 km per second. That's too slow to climb away from the Sun and

make it out to Earth.

But some previous assumptions were wrong, says Gladman, because the collisional cir-

cumstances at Mercury are "very different than anywhere else." The Sun's innermost

planet speeds through space with a mean velocity of 48 km per second. Furthermore,

asteroids and comets crossing Mercury's orbit also travel fast. So impactors strike the

planet at speeds 5 to 15 times its escape velocity, and ejecta can rocket off the surface

travelling much faster than had been assumed.

Meteorites from Mercury? by Ken Croswell

Rocks from Mercury? These pieces of the meteorite known as Northwest Africa 2999

are angrites, a rare type that some specialists believe may represent samples of Mer-

cury's surface. The total weight of these is 392 grams (about 14 ounces); the small cube

is 1 cm on a side. Greg Hupé / The Hupé Collection


What makes tau Bootis even more interesting is that it harbours a giant planet orbiting

very close to the surface of the star. The planet is actually so close (only one twentieth the

distance between the Sun and Earth) and so massive (about 6.5 times the size of Jupiter)

that it succeeded in forcing the surface of the star to co-rotate with the planet's orbital

motion through tidal torques. This is the same effect that causes the moon to co-rotate

around Earth so that we see only one side of the moon.

Since the astronomers managed to catch tau Bootis in this state of magnetic flipping dur-

ing just 2 years of observations, it is likely that this event is much more frequent on tau

Bootis than it is on the Sun. It is possible that the giant planet that has already managed to

speed up the surface of tau Bootis is also spinning up the magnetic engine of its host star.

The astronomers will keep their telescopes focused on tau Bootis in coming years to

make sure they catch the star's next magnetic turnover. Their goal is a better understand-

ing of how magnetic engines work in stars, including our Sun.

Slightly hotter and 20 percent more massive than the Sun, tau Bootis is fairly bright and

visible with the naked eye and located only 51 light-years away from us. It is currently

rises about midnight and is visible for most of the night near the bright star Arcturus in

the constellation Bootis in the northeast part of the sky.

Taken by Messenger on January 14, 2008, from about 17,000 miles away, this view of a

gibbous Mercury shows about half of the area not photographed by Mariner 10 in 1974–

75. The heavily cratered landscape is reminiscent of other areas previously seen.

NASA / JHU-APL / Carnegie Inst. of Washington


MERCURY and Venus will be visible in the morning sky less than 3° apart,

and so within the same binocular field, throughout March. Mercury's magnitude

ranges from 0.2 on March 1 to -0.5 on March 31, considerably brighter than any

star near Venus. The March apparition of Mercury will be the best in the morn-

ing sky for the year for southern hemisphere viewers.

Mercury starts the month 1.5° to the upper left of Venus. Over the next few mornings it

moves another degree or so above Venus. Both planets will be moving to the east through

the stars and closing in on Neptune, magnitude 8.0 and visible in binoculars while the sky

is fairly dark. On the morning of March 6 (NZDT) the three planets will be joined by the

Moon which will be just left of Venus. Mercury and Neptune will be just over 4° apart

with Venus and the Moon between them.

During the early hours

the Moon will succes-

sively occult all three

planets but none of the

occultations is observable

from New Zealand.

Venus moves past Nep-

tune over the next couple

of mornings and then

Mercury is closest to and

1° to the left of Neptune

on the morning of 10

March. By then Mercury

will be almost 3° above

Venus. The two will re-

main about this distance

apart for the next week

but get a little lower in

the early twilight.

After mid March, Mer-

cury will start closing in

again on Venus, until on

the morning of March 26

the two will be almost

level with Mercury 1° to the right of Venus when the two will be about 3.5° above Ura-

nus, magnitude 5.9.

Mercury is closest to Uranus on the morning of March 28, when it will be 1.6° to the

right of, and slightly above Uranus. With Venus they will form a small triangle, see dia-

gram above. By the last morning of the month Mercury will be only about 6° up 45 min-

utes before sunrise, and just over 3° below and to the right of Venus. At magnitude -0.6 it

should be fairly easy to find, especially in binoculars. With the clocks still on NZDT it

should be visible until well after 7 am.


VENUS remains prominent in the morning sky during March. It rises over 2

hours before the Sun on March 1 and just over 90 minutes before it on the 31st.

As a result it will get a little lower in the morning twilight during the month.

As described above, Venus and Mercury will be no more than 3° apart throughout March.

Early in the month they will pass Neptune, with Venus and Neptune closest on the morn-

ing of March 7, when the two will be just under 40' from each other. Neptune will be to

the lower left of Venus.

Later in the month Venus and Mercury pass Uranus. On the morning of March 28, the

three will form a small triangle fairly low to the east, with sides about 1.6°, as shown in

the diagram. Uranus, magnitude 5.9, will be to the lower left of Venus. In addition, the

asteroid (4) Vesta, magnitude 8.0, will be 3° to the right of Venus and 2° from Mercury

so that Uranus, Mercury and Vesta form a straight line.

All four will be within the field of view of binoculars and should be visible in eg an 8x50


Provided by the University of Hawaii

February 13, 2008

A n international group of astronomers that includes the University of Hawaii's

Evgenya Shkolnik reported today that they have discovered that the Sun-like star

tau Bootis flipped its magnetic field from north to south sometime during the last

year.

It has been known for many years that the Sun's magnetic field changes its direction

every 11 years, but this is this is the first time that such a change has been observed in

another star. The team of astronomers, who made use of Canada-France-Hawaii Tele-

scope atop Mauna Kea, are now closely monitoring tau Bootis to see how long it will be

before the magnetic

field reverses again.

Magnetic field reversals

on the Sun are closely

linked to the varying

number of sunspots seen

on the Sun's surface.

The last "solar mini-

mum," the time when

number of sunspots was

the lowest and the mag-

netic flip occurred, was

in 2007. The first sun-

spot of the new cycle

appeared just last

month.

The magnetic cycle of

the Sun impacts the

Earth's climate and is

believed to have caused

the little ice age in the

seventeen century. The

Earth's magnetic field also flips, although much less frequently and more erratically.

The international team led by Jean-Francois Donati and Claire Moutou of France caught

tau Bootis in the process of flipping its magnetic field while they were mapping the mag-

netic fields of stars.

Sun-like star flips its magnetic field The first time astronomers have observed this in a

star other than our Sun.

The magnetic field of the Sun-like star tau Bootis has flipped

its north and south poles. The shortened cycle of this event may

be due to interactions with its nearby massive planet.

Credit: Karen Teramura/UH IfA


Investigator, spectra of several thousands of galaxies in a 4-square-degree field (or 20

times the size of the full Moon) at epochs corresponding to about half the current age of

the Universe (about 7 billion years ago) were obtained and analysed.

"This is the largest field ever covered homogeneously by means of spectroscopy to this

depth," declares Le Fevre. "We have now collected more than 13,000 spectra in this field

and the total volume sampled by the survey is more than 25 million cubic light-years."

The astronomers compared their result with that of the 2dFGRS survey that probed the

local Universe, i.e. measures the distortion at the present time.

Within current uncertainties, the measurement of this effect provides an independent indi-

cation of the need for an unknown extra energy ingredient in the 'cosmic soup', support-

ing the simplest form of dark energy, the so-called cosmological constant, introduced

originally by Albert Einstein. The large uncertainties do not yet exclude the other scenar-

ios, though.

"We have also shown that by extending our measurements over volumes about ten times

larger than the VVDS, this technique should be able to tell us whether cosmic accelera-

tion originates from a dark energy component of exotic origin or requires a modification

of the laws of gravity," explains Guzzo.

"VIMOS on the VLT would certainly be a wonderful tool to perform this future survey

and help us answer this fundamental question. This strongly encourages scientists to pro-

ceed with even more ambitious surveys of the distant Universe," concludes Le Fevre.

More Information

"A test of the nature of cosmic acceleration using galaxy redshift distortions", by L.

Guzzo et al., Nature, 31 January 2008.

Notes

• The VLT VIsible Multi-Object Spectrograph (VIMOS) can observe spectra of about

1,000 galaxies in one single exposure. This cosmology science machine is installed at

the 8.2-m MELIPAL telescope, the third unit telescope of the Very Large Telescope

(VLT) at the ESO Paranal Observatory.

• The VIMOS VLT Deep Survey (VVDS) is a breakthrough spectroscopic survey aim-

ing at providing a complete picture of galaxy and structure formation over a large

fraction of the Universe's history, covering sixteen square degrees of the sky in four

separate fields.

Copyright ESO Education & Public Relations Department Karl-Schwarzschild-Strasse 2,

D-85748 Garching, Germany


pair while the sky is still reasonably dark. The four bodies should be sufficiently close

to one another to all be in a binocular field of view from the 26th to 30th of March.

Venus and Uranus are closest on the morning March 29, with the two 45' apart. On the

following morning Venus will be lower than Uranus and a little further to the right,

just over a degree away. Mercury will be on the opposite side of Venus to Uranus,

twice as far away. On March 31 the three planets will form a diagonal line to the east.

Venus will then be mid-way between the other two planets.

MARS will be in the evening sky all month. The orange planet is highest

and due north in March shortly after sunset with an altitude of about 28° as

seen from Northland but 10° lower from the extreme south of New Zea-

land.

On March 1, Mars sets at about 1 am NZDT on March 1, making it visible all evening.

It will then have a magnitude 0.2. By March 31 it will have faded a little to magnitude

0.8 and set an hour earlier, so will be getting low by 11 pm. The planet starts March in

Taurus, but moves into Gemini on the evening of March 5.

On the evening of March 15, the 60% lit Moon will be about 3.5° from Mars. Towards

the end of the month the planet passes the 3rd magnitude star ε Gem, the two being

only 15' (half the diameter of the full Moon) apart on March 30.

JUPITER remains a morning object throughout March. An hour before

sunrise it will be fairly high, to the east at the beginning month and half

way round to the northeast by the end of the month. Jupiter will be in Sagit-

tarius a few degrees from the "Teapot's Handle".

The Moon passes Jupiter twice during March. On the morning of the 3rd the 25% lit

Moon will be about 5° from Jupiter: the Moon will occult the star Nunki, σ Sgr, mag-

nitude 2.1 just before sunrise. On the last morning of the month, the 42% lit Moon will

be less than 3° from the planet.

SATURN is visible all evening throughout March, although it will be

rather low early evening at the beginning of the month. By the end of the

month, Saturn will transit, and so be due north and at its highest, soon after

11 pm NZDT.

Saturn remains in Leo during March, 5° from the constellation's brightest star, Regulus

magnitude 1.4 on the 1st and 3° from the star on the 31st. On March 19 the nearly full

Moon, 94% lit, will be 3° from Saturn early evening, dropping to 2° late evening. The

two are closest in about 3am the following morning, some 1.7° apart. Close to sunset

on the 19th the Moon will occult Regulus.


Beginner's Guide to the Night Sky

March 24 at 8.00pm

Epsom Methodist Church Hall, 587 Manukau Rd, near Greenwood's Corner

Beginners Guide to Astronomy

Astrophotography A high level introduction to Astrophotography

Presented by Henk Stolk

We will explore topics around equipment and software to be

used. What is possible? Which skills come in handy?

Where to do it and how much money, etc.

The event will end with a survey to see if we can set up a one

year astrophotography class.

These informal meetings are designed for people with little or no observing experience and those who wish to learn their way around the night sky. The sessions are interactive, so feel free to ask questions and generally join in.

SOLUTION TO THE FEBRUARY CROSSWORD

Across: 2 Mimosa, 4 Very Large Array, 7 Deimos, 10 Lord Rosse, 11 Shepard, 12 Epoch.

Down: 1 Gacrux, 3 Sunrise, 5 Armstrong, 6 Melbourne, 8 Cepheid, 9 Seeing.


ESO Science Release 04/08

A stronomers have used ESO's Very Large Telescope to measure the distribution

and motions of thousands of galaxies in the distant Universe. This opens fasci-

nating perspectives to better understand what drives the acceleration of the

cosmic expansion and sheds new light on the mysterious dark energy that is thought to

permeate the Universe.

"Explaining why the expansion of the Universe is currently accelerating is certainly the

most fascinating question in modern cosmology," says Luigi Guzzo, lead author of a

paper in this week's issue of Nature, in which the new results are presented. "We have

been able to show that large surveys that measure the positions and velocities of distant

galaxies provide us with a new powerful way to solve this mystery."

Ten years ago, astronomers made the stunning discovery that the Universe is expand-

ing at a faster pace today than it did in the past.

"This implies that one of two very different possibilities must hold true," explains Enzo

Branchini, member of the team. "Either the Universe is filled with a mysterious dark

energy which produces a repulsive force that fights the gravitational brake from all the

matter present in the Universe, or, our current theory of gravitation is not correct and

needs to be modified, for example by adding extra dimensions to space."

Current observations of the expansion rate of the Universe cannot distinguish between

these two options, but the international team of 51 scientists from 24 institutions found

a way that could help in tackling this problem. The technique is based on a well-known

phenomenon, namely the fact that the apparent motion of distant galaxies results from

two effects: the global expansion of the Universe that pushes the galaxies away from

each other and the gravitational attraction of matter present in the galaxies' neighbour-

hood that pulls them together, creating the cosmic web of large-scale structures.

"By measuring the apparent velocities of large samples of galaxies over the last thirty

years, astronomers have been able to reconstruct a three-dimensional map of the distri-

bution of galaxies over large volumes of the Universe. This map revealed large-scale

structures such as clusters of galaxies and filamentary superclusters," says Olivier Le

Fevre, member of the team. "But the measured velocities also contain information

about the local motions of galaxies; these introduce small but significant distortions in

the reconstructed maps of the Universe. We have shown that measuring this distortion

at different epochs of the Universe's history is a way to test the nature of dark energy."

Guzzo and his collaborators have been able to measure this effect by using the VIMOS

spectrograph on Melipal, one of the four 8.2-m telescopes that is part of ESO's VLT.

As part of the VIMOS-VLT Deep Survey (VVDS), of which Le Fevre is the Principal

New Light on Dark Energy Probing the cosmic Web of the Universe


subtracting light from just the star from the combined light, you are left with light from

the planet," said Deming, who is leading the search for exosolar worlds with Deep Im-

pact. "We can analyze this light to discover what the atmospheres of these planets are

like."

Deep Impact will also look back to observe Earth in visible and infrared wavelengths,

allowing comparisons with future discoveries of Earth-like planets around other stars.

For information about Epoxi, visit http://www.nasa.gov/mission_pages/epoxi/ .

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages Epoxi for NASA's Science

Mission Directorate, Washington. The University of Maryland is the Principal Investiga-

tor institution. NASA Goddard leads the mission's exosolar planet observations. The

spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo-

rado.

This is an artist's rendition of the Deep Impact flyby spacecraft releasing its impactor, 24

hours before the impact event in July 2005. Pictured from left to right are comet Tempel

1, the impactor, and the flyby spacecraft. The fly spacecraft is about 3.2 metres long, 1.7

metres wide, and 2.3 metres high. The launch payload has a mass of 1020 kg..

The flyby spacecraft is being re-christened as EPOXI. Credit: NASA/JPL


Ulysses mission coming to a natural end

ESA News , 22 February 2008

U lysses, the mission to study the Sun's poles and the influence of our star on sur-

rounding space is coming to an end. After more than 17 years in space -- almost

four times its expected lifetime -- the mission is finally succumbing to its harsh

environment and is likely to finish sometime in the next month or two.

Ulysses is a joint mission between ESA and NASA. It was launched in 1990 from a space

shuttle and was the first mission to study the environment of space above and below the

poles of the Sun. The reams of data Ulysses has returned have forever changed the way

scientists view the Sun and its effect on the space surrounding it.

Ulysses is in a six-year orbit around the Sun. Its long path through space carries it out to

Jupiter's orbit and back again. The further it ventures from the Sun, the colder the space-

craft becomes. If it drops to 2ºC, the spacecraft's hydrazine fuel will freeze.

"We expect certain parts of the spacecraft to reach 2ºC pretty soon," says Richard Mars-

den, ESA's Ulysses Project Scientist and Mission Manager. This will block the fuel pipes,

making the spacecraft impossible to manoeuvre.

In an attempt to solve this problem, the ESA-NASA project team approved a plan to tem-

porarily shut off the main spacecraft transmitter. Unfortunately, during the first test of

this method in January, the power supply to the radio transmitter failed to turn back on.

After many attempts, the Ulysses project team now consider it highly unlikely that the X-

band transmitter will be recovered. So, the spacecraft has lost its ability to send large

quantities of scientific data back to Earth and is facing the gradual freezing of its fuel

lines. This spells the end of this highly successful mission. "Ulysses is a terrific old work-

horse. It has produced great science and lasted much longer than we ever thought it

would," says Marsden. "This was going to happen in the next year or two, it has just

taken place a little sooner than we hoped."

The team plan to continue operating the spacecraft in its reduced capacity for as long as

they can over the next few weeks. "We will squeeze the very last drops of science out of

it," says Marsden.

Astronomical News


SOCIETY MEMBERS PLAY A BIG ROLE IN DISCOVERY OF A NEW

SOLAR SYSTEM

The closest match yet found to our solar system

T wo members of the Auckland Astronomical Society made observations that

proved crucial to the discovery of a new solar system some 5,000 light years

away.

Grant Christie used the 0.35m Nustrini Telescope at Stardome Observatory while Jennie

McCormick used her 0.25m Meade LX200 at Farm Cove Observatory in Pakuranga.

Both telescopes have since been replaced and upgraded.

The results are reported in the February 15 issue of the prestigious journal Science. Since

2004, Grant and Jennie have been very active members of the MicroFUN collaboration

and both are lead authors on the paper.

Relative to the parent star, these two planets bear a striking resemblance to Jupiter and

Saturn. The similarity extends to their relative sizes, the spacing of their orbits and their

temperatures.

This makes the new solar system look like a half-sized model of our one which is also

dominated by two gas giant planets. It is the closest match yet found to our solar system

and supports current theories of how it formed.

Theorists have wondered whether gas giants in other solar systems would form in the

same way as ours did. This discovery seems to suggest they do, said Dr Scott Gaudi, as-

sistant professor of astronomy at Ohio State University, who led the analysis team and

was the lead author.

The find also suggests that our galaxy hosts many planetary systems arranged like our

own.

The two planets were revealed when the star they orbit crossed almost exactly in front of

a more distant star as seen from Earth. For a two-week period from late March through

early April of 2006, the nearer star magnified the light shining from the farther star.

This natural magnifying effect is called gravitational microlensing, and this was a par-

ticularly dramatic example: the light from the more distant star was magnified 500 times

making the event especially sensitive to planet detection.


February 7, 2008

N ASA's Deep Impact spacecraft is aiming its largest telescope at five stars in a

search for alien (exosolar) planets as it enters its extended mission, called Ep-

oxi.

Deep Impact made history when the mission team directed an impactor from the space-

craft into comet Tempel 1 on July 4, 2005. NASA recently extended the mission, redi-

recting the spacecraft for a flyby of comet Hartley 2 on Oct. 11, 2010.

As it cruises toward the comet, Deep Impact will observe five nearby stars with

"transiting exosolar planets," so named because the planet transits, or passes in front of,

its star. The Epoxi team, led by University of Maryland astronomer Michael A'Hearn,

directed the spacecraft to begin these observations Jan. 22. The planets were discovered

earlier and are giant planets with massive atmospheres, like Jupiter in our solar system.

They orbit their stars much closer than Earth does the sun, so they are hot and belong to

the class of exosolar planets nicknamed "Hot Jupiters."

However, these giant planets may not be alone. If there are other worlds around these

stars, they might also transit the star and be discovered by the spacecraft. Deep Impact

can even find planets that don't transit, using a timing technique. Gravity from the un-

seen planets will pull on the transiting planets, altering their orbits and the timing of

their transits.

"We're on the hunt for planets down to the size of Earth, orbiting some of our closest

neighboring stars," said Epoxi Deputy Principal Investigator Drake Deming of NASA's

Goddard Space Flight Center in Greenbelt, Md. Epoxi is a combination of the names

for the two extended mission components: the exosolar planet observations, called Ex-

trasolar Planet Observations and Characterization (Epoch), and the flyby of comet

Hartley 2, called the Deep Impact Extended Investigation (Dixi). Goddard leads the

Epoch component.

More than 200 exosolar planets have been discovered to date. Most of these are de-

tected indirectly, by the gravitational pull they exert on their parent star. Directly ob-

serving exosolar planets by detecting the light reflected from them is very difficult,

because a star's brilliance obscures light coming from any planets orbiting it.

However, sometimes the orbit of an exosolar world is aligned so that it eclipses its star

as seen from Earth. In these rare cases, called transits, light from that planet can be seen

directly.

"When the planet appears next to its star, your telescope captures their combined light.

When the planet passes behind its star, your telescope only sees light from the star. By

NASA's Deep Impact Begins Hunt for Alien Worlds


cooling and lighting. Dozens of Titan's lakes individually have the equivalent of at least

this much energy in the form of methane and ethane.

"This global estimate is based mostly on views of the lakes in the northern polar regions.

We have assumed the south might be similar, but we really don't yet know how much

liquid is there," said Lorenz. Cassini's radar has observed the south polar region only

once, and only two small lakes were visible. Future observations of that area are planned

during Cassini's proposed extended mission.

Scientists estimated Titan's lake depth by making some general assumptions based on

lakes on Earth. They took the average area and depth of lakes on Earth, taking into ac-

count the nearby surroundings, like mountains. On Earth, the lake depth is often 10 times

less than the height of nearby terrain.

"We also know that some lakes are more than 10 meters or so deep because they appear

literally pitch-black to the radar. If they were shallow we'd see the bottom, and we don't,"

said Lorenz.

The question of how much liquid

is on the surface is an important

one because methane is a strong

greenhouse gas on Titan as well as

on Earth, but there is much more

of it on Titan. If all the observed

liquid on Titan is methane, it

would only last a few million

years, because as methane escapes

into Titan's atmosphere, it breaks

down and escapes into space. If the

methane were to run out, Titan

could become much colder. Scien-

tists believe that methane might be

supplied to the atmosphere by

venting from the interior in cryo-

volcanic eruptions. If so, the

amount of methane, and the temperature on Titan, may have fluctuated dramatically in

Titan's past.

"We are carbon-based life, and understanding how far along the chain of complexity to-

wards life that chemistry can go in an environment like Titan will be important in under-

standing the origins of life throughout the universe," added Lorenz.

Cassini's last radar flyby of Titan was on Feb. 22, when the radar instrument observed the

Huygens probe landing site.

For images and more information visit:

http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Radar Shows Evidence of Seas Image Credit: NASA/JPL


The Optical Gravitational Lensing Experiment (OGLE), led by Professor Andrzej Udal-

ski first detected the event, dubbed OGLE-2006-BLG-109, on March 28, 2006 from the

Warsaw University Observatory in Chile. The Microlensing Follow Up Network

(MicroFUN), led by Professor Andrew Gould at Ohio State University, then joined with

OGLE to organize astronomers worldwide to gather observations of it.

Grant responded the next night. “The skies were mostly clear and this allowed us to get

30 hours of data over seven nights, two of those coinciding with crucial phases of the

event”, he explained.

Jennie McCormick obtained 10 hours of observations over three nights at crucial times

from her observatory in Farm Cove, Pakuranga. “For an amateur with a small 0.25m

telescope, being able to work alongside the professionals on a really exciting and impor-

tant event like this is just mind-blowing,” she said.

The early phases of the event were observed by Paul Tristram using the NZ/Japan MOA

Relative to the parent star, the two new planets bear a striking resemblance to Jupiter

and Saturn. The similarity extends to their relative sizes, the spacing of their orbits and

their temperatures. Image Credit: KASI


1.8 metre telescope at Mt John Observatory in Canterbury but cloud prevented observa-

tions while it was at maximum brightness.

The current discovery relied on 11 different ground-based telescopes in countries around

the world, including New Zealand, Tasmania, Israel, Chile, the Canary Islands, and the

United States. In total 69 scientists from 11 countries contributed.

Dr Gaudi took the lead in analysing the data as they came in. As he studied the light sig-

nal, he saw a distortion that he thought was caused by a Saturn-mass planet. Then, less

than a day later, came an additional distortion he wasn't expecting: a "blip" in the signal

that appeared to be caused by a second, larger planet orbiting the same star.

“It was exciting to see the picture evolving even while the event was still taking place”,

Christie recalled. “The theorists guessed early on we were detecting a new planetary

system”.

Over the next few months, Gaudi demonstrated that this two-planet interpretation was

correct. Then David Bennett at the University of Notre Dame near Chicago refined

Gaudi's preliminary model using sophisticated software, and revealed additional details

about the system.

This is the third time a Jupiter-mass planet was found by microlensing, Gaudi explained.

In the previous two cases, additional planets would have been very difficult to detect, had

they been there. The fact that astronomers found the planets during the first event that

allowed such a detection suggests that these scaled-down versions of our solar system are

very common, he added.

The newly-discovered planets appear to be gas planets like Jupiter and Saturn - only

about 80 percent as big - and they orbit a red dwarf star about half the mass of the sun.

The star is dim and cooler than ours, issuing only five percent as much light.

Although the star is much dimmer than our sun, temperatures at both planets are likely to

be similar to that of Jupiter and Saturn, because they are orbiting closer to their star.

“The temperatures are important because these dictate the amount of material that is

available for planet formation,” Gaudi said. “Most theorists think that the biggest planet

in our solar system formed at Jupiter's location because that is the closest to the sun that

ice can form. Saturn is the next biggest because it is in the next location further away,

where there is less primordial material available to form planets.”

Gaudi described this microlensing event as the most complicated one ever studied. The

astronomers carefully modelled their data on computers, and explored all possible expla-

nations for the light signal. It took a year and a half of intensive analysis before they

were confident that they had found the two planets.

While it is possible there may be small rocky planets in the new planetary system, they

were not detected.

-From Stardome, Farm Cove Observatory and Ohio State University press releases.


Titan's Surface Organics Surpass Oil Reserves on Earth

Jet Propulsion Laboratory, Pasadena, Calif.

Feb. 13, 2008

S aturn's orange moon Titan has hundreds of times more liquid hydrocarbons than all

the known oil and natural gas reserves on Earth, according to new data from

NASA's Cassini spacecraft. The hydrocarbons rain from the sky, collecting in vast

deposits that form lakes and dunes.

The new findings from the study led by Ralph Lorenz, Cassini radar team member from

the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., are reported in

the Jan. 29 issue of the Geo-

physical Research Letters.

"Titan is just covered in carbon-

bearing material—it's a giant

factory of organic chemicals,"

said Lorenz. "This vast carbon

inventory is an important win-

dow into the geology and cli-

mate history of Titan."

At a balmy -179ºC, Titan is a far

cry from Earth. Instead of water,

liquid hydrocarbons in the form

of methane and ethane are pre-

sent on the moon's surface, and

tholins probably make up its

dunes. The term "tholins" was

coined by Carl Sagan in 1979 to

describe the complex organic

molecules at the heart of pre-

biotic chemistry.

Cassini has mapped about 20

percent of Titan's surface with radar. Several hundred lakes and seas have been observed,

with each of several dozen estimated to contain more hydrocarbon liquid than Earth's oil

and gas reserves. The dark dunes that run along the equator contain a volume of organics

several hundred times larger than Earth's coal reserves.

Proven reserves of natural gas on Earth total 130 billion tons, enough to provide 300

times the amount of energy the entire United States uses annually for residential heating,

Pools on Titan: An artist's imagination of hydrocar-

bon pools, icy and rocky terrain on the surface of Sat-

urn's largest moon Titan.

Image by Steven Hobbs (Brisbane, Queensland, Aus-

tralia).

southern sentinel crossword society march 2008 edition … · fred is the author of "stargazer...

Documents