Archive for the ‘Astronomy blog’ Category

Daily cosmobite: Mars and Venus meet up in the west

Published by Andrew Jacob on February 20, 2015 No Comments

MarsNearVenusAndMoon.Feb21.2015From Feb 20-23, 2015 Mars and Venus will appear close in the evening sky. They are at their closest at 7-am on Feb 22 at just one Moon-width apart (or half a degree). The Moon itself, fresh into lunar new year,  is nearby on Feb 21 but not visible. Look for the Moon on Feb 22 when it is to the right and above the two planets. Venus looks white and much brighter than faint, orange-coloured Mars so a pair of binoculars may be helpful.


Look west on Feb 20,21,22 & 23 to see Mars and Venus close. Look about a fist width above the horizon at 8:15pm AEDT.


The twin peaks of lunar crater Pythagoras. Sketch and copyright Harry Roberts ©, all rights reserved.

Regular lunar observer Harry Roberts reports on his view of crater Pythagoras – a big crater seen in a small telescope.

            There’s much to be said for small ‘scopes: they sit on their tripods just waiting for something to happen!

In this case it was a good combination of lighting and libration on crater Pythagoras, in the Moon’s far northern latitudes – a spectacular glimpse of the crater’s interior and its complex of central peaks, with the terminator just 6 degrees west of the site! But heavy cloud loomed: no time for ‘big’ ‘scopes – the 100/1000 ‘Mak’ was pointed and sketching began a minute or two later.

This big crater, 130km wide, dates from the Eratosthenian period, 1.1 to 3.2 b.y ago. A wide time range: other epochs have ½ b.y or less, but Eratosthenian’s were formed over a two b.y. period. It looks younger rather than older, with bright central peaks and distinct collapse formations well preserved on its inner walls. Surprisingly, it seems there are ‘ponds’ of impact melt just beyond its NE rim: and even more surprising, it seems I logged one in the small ‘scope (Fig)!

What particularly caught my eye was the superb shadow, cast by the central peaks, which stretched 40km or so, to cast an ‘inky’ print on the lower slopes of the crater’s NW wall: a very pretty sight (Fig)!

The crater floor was dim and unevenly lit, due to unseen hummocks, low ridges, or both. And Orbiter images confirm shallow flooding in this crater, as it is so near the ‘far-side’ regions (where such flooding is rare). The bright central peaks seemed almost in contact, with a third hidden completely – and a bright ‘spur’ ran from the crater wall to the peaks on the N side (Fig), with a small secondary crater seen on the wall (arrow). While there is a scree of collapsed material from the wall on that side, it doesn’t reach the central peaks: perhaps I saw a floor ridge that also caught some rising sun. The Sun’s altitude at the site was just 7° at the time.

To the right the crater wall showed several scarps and terraces, looking a bit like Sydney’s coastline, each with a shadow between. Further right, distant rugged terrain was faintly seen: mangled regions where debris fields of huge craters have blended. It’s between that rough zone and the crater’s N wall that melt ‘ponds’ may be found (Fig, lower right). The inner walls on the left (W) side showed long bright scarps and some terraces cast thin shadows westward. The high (>4km) eastern walls (foreground) cast shadow across half the crater’s floor.

The terrain on Pythagoras’ east side (foreground, not drawn) is in fact the interior of ancient giant Babbage (broken line) – and ejecta from the younger crater is strewn over the latter’s floor in swirls.

Crater Pythagoras is co-temporal with well-known craters like Bullialdus, Eratosthenes and Theophilus (it’s bigger though) but shows what they might look like if seen from a low lunar orbit: it’s a revelation!

Pythagoras, the religious teacher and philosopher of 5thC BC Greece, was well known for his geometry, teaching that Nature expresses itself in ideal forms, which could be mathematically calculated (Wiki). This idea is pretty well accepted today, as is his theory that Earth was round and circled the Sun!  A most radical idea, however, even in the sixteenth century AD!

Keep the small ‘scopes ready: you can’t tell what might appear.

Harry Roberts is a Sun and Moon observer, a regular contributor to the Sydney Observatory blog and a member of the Sydney City Skywatchers.

MarsPlume.Nature.2015A mysterious plume appeared on Mars in 2012. A recent analysis investigated two explanations: high-altitude water or carbon-dioxide ice or a Martian aurora. However, both explanations conflict with our current understanding of Mars’ atmosphere.



Mysterious plume on Mars. Image from The Conservation and Nature.





Daily cosmobite: Pluto was discovered 85 years ago

Published by Andrew Jacob on February 18, 2015 No Comments

NewHorizons.PlutoCharonOrbitClyde Tombaugh discovered Pluto 85 years ago on February 18 1930. He found it on a pair of photographs taken a few weeks earlier. Its moon Charon was discovered in 1978.


The latest from New Horizons spacecraft. Charon and Pluto orbit about a common centre – their “barycentre”, January 25-31. NASA/APL/Southwest Research Institute. Click image to see animated gif.





Daily cosmobite: Dark observing locations in Perth

Published by Andrew Jacob on February 17, 2015 No Comments

Perth.ISS026-E-5249Light pollution is the bane of city-based astronomers. This series of night time images was taken from the International Space Station. They help identify dark sites from which to best view the sky. This week we look at Perth.

Perth at night as seen from the International Space Station, 26 Nov 2010. Image, ISS026-E-5249, courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center.

20 Feb 2015, 7-10pm

This is an astronomical evening of exploration into the world of one of Australia’s leading scientists as you enjoy the stars with a drink in hand and nibbling on solar system inspired canapés specially designed by renowned chef Claire de Lune. Claire is the executive chef at Claire’s Kitchen at Le Salon and has appeared on both TV and radio in programs for the ABC, SBS and Channels 9 and 10.

Hear from leading astrophysicist Dr Lisa Harvey Smith; researcher, author and Project Scientist for Australia’s largest radio telescope. Dr Harvey Smith is an inspirational speaker, and you will have an opportunity to ask her about some of the big cosmological questions these large telescope arrays are being designed to explore. The Q&A session will be hosted by Claire de Lune.

You can also explore our Solar System and galaxy with astronomers, who will guide you to view through telescopes, and in the planetarium which creates an amazing virtual night sky.  This event is held in fascinating Sydney Observatory and is part of the Sydney Gay and Lesbian Mardi Gras program. It is open to all.

For adults 18+ only.
Cost: $55, Concession and members $50
(includes all activities, wines and other drinks, food)
Call: 9921 3485 or Book On-line

SydObs.Muntz.SouthDome.detailThe south dome of Sydney Observatory is made from Muntz metal, a copper-zinc (brass) alloy.



A stamp on the south dome showing this Muntz metal weighs 26 ounces per square foot. Photo by Toner Stevenson ©MAAS.




A Sunday cosmobite: Galileo’s birthday

Published by Andrew Jacob on February 15, 2015 No Comments

Justus_Sustermans_-_Portrait_of_Galileo_Galilei,_1636Galileo was born on this day, February 15, in 1564.


Happy Birthday Galileo!





Daily cosmobite: The Moon’s motion across the sky

Published by Andrew Jacob on February 13, 2015 No Comments

MoonBySydObs.1930The Moon orbits Earth in 27.3 days. From the point of view of an observer on the ground it appears to move a little over 13-degrees eastward through the sky each night. This means it rises, on average, about 50-minutes later each night.


Earth’s Moon – there one night, gone the next! Photo by Sydney Observatory astronomers 1930.




Daily cosmobite: A breakout of solar filaments

Published by Andrew Jacob on February 12, 2015 No Comments

SunandFilament.2015FEB07Several filaments, dark snake-like streaks, appear on the Sun today. These long streams of hot gas ‘float in the magnetic field above the Sun’s surface. APOD for 2015 Feb 10 claims one is amongst the longest ever recorded and it has been there for a week already.

Photographing the Sun with an iPhone is hard. Better views are had during our public solar viewing tours. Photo Andrew Jacob, Sat Feb 07, 2015 © MAAS, Sydney.







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