Archive for the ‘Astronomy blog’ Category

Daily cosmobite: watch for the crescent Moon

Published by Nick Lomb on July 28, 2014 No Comments

28_Crescent Moon_Nick LombThis month the first visibility of the crescent Moon after the astronomical instant of new Moon is of particular significance in the Islamic calendar. The Moon was new on Sunday at 8:42 am. After sunset this evening the Moon will have moved sufficiently away from the glare of the Sun to be briefly visible as a thin crescent in the western sky.

The crescent Moon. Photo Nick Lomb

Daily cosmobite: lunar flight anniversary

Published by Nick Lomb on July 26, 2014 No Comments

26_The Apollo 15 lunar rover on the Moon_NASAApollo 15 was launched towards the Moon on this date in 1971. Two astronauts, David Scott and James Irwin landed four days later next to the spectacular scenery of the Apennine Mountains. In a lunar first they travelled about 28 km in a Lunar Roving Vehicle.

The Apollo 15 lunar rover on the Moon. Courtesy NASA

Daily cosmobite: stars in the south

Published by Nick Lomb on July 25, 2014 No Comments

25_Scorpius_Nick LombFacing south in the early evening we see the reddish star Antares among the stars of Scorpius to our left or east. In front of us the Southern Cross with its bright stars stands vertically high in the sky while the two pointers are to its left and almost horizontal.

Antares and the stars of the constellation of Scorpius the Archer. Photo Nick Lomb

To help you learn about the southern night sky, Sydney Observatory provides an audio guide/podcast, transcript of that audio, and a sky map or chart each month. This month’s guide is presented by Melissa Hulbert, Sydney Observatory Astronomy Educator.

Mel suggests stars and constellations to look out for this month include Scorpius, with the red star at its heart, Antares; Sagittarius (which looks more like a teapot than a centaur); Crux – more commonly known as the Southern Cross; and Ophiuchus, the 13th sign of the zodiac! Mel also tells us the best times and dates to try to see the planets Venus, Saturn, Jupiter, Mars and Mercury.

For more, listen to the August 2014 night sky guide audio, or read the transcript below.

HEAR THE AUDIO
You can subscribe with iTunes or upload the (18 mins 40 secs) audio to your iPod or mp3 player, or listen to it on your computer.

SEE THE SKY CHART
We provide an embedded sky map (below) and an August 2014 night sky chart (PDF) which shows the stars, constellations and planets visible in the night sky from anywhere in Australia. To view PDF star charts you will need to download and install Adobe Acrobat Reader if it’s not on your computer already.

August 2014 night sky chart

BUY THE BOOK
Our annual book, ‘The 2014 Australasian sky guide’, by Dr Nick Lomb has more information and star maps for months from December 2013 until December 2014 inclusive (next year’s, likely to be available from November, will have months from December 2014 to December 2015), plus information about the Sun, twilight, the Moon and tides, and a host of other fascinating astronomical information. You can purchase it ($16.95) at Sydney Observatory and Powerhouse Museum shops or other good bookshops, or online through Powerhouse Publishing (additional packing/postage costs apply).

READ THE TRANSCRIPT (after the jump)

(more…)

Daily cosmobite: Venus and the Moon

Published by Nick Lomb on July 24, 2014 No Comments

24_Venus Mercury and the Moon_Nick LombEarly risers can see Venus each morning before dawn low in the north-east. Those who are not early birds will need to wait until November when Venus will switch to the evening sky. Tomorrow morning a thin crescent Moon is near Venus; it is above and to the right or east of the planet.

Venus, Mercury and the Moon on the morning of 25 July 2014. Chart Nick Lomb

Adler Planetarium entrance_Nick Lomb

The entrance of the Adler Planetarium. Note the large poster advertising the planetarium’s premier sky show, Destination Solar System, on the left, while on the right a poster advertises the popular exhibition for young children, Planet Explorers. Photo Nick Lomb

At the beginning of July 2014 I visited one of my favourite places in the world, the Adler Planetarium in Chicago. Like the Griffith Observatory in Los Angeles that I had visited two days earlier, it is spectacularly located though not on hills but on a small peninsula jutting into Lake Michigan with a wonderful view of the Chicago skyline.

Again like Griffith Observatory, it has been extended relatively recently. Instead of digging underneath the original heritage building the Adler Planetarium was extended with a glass Sky Pavilion that opened in 1999 and provided extra space with great views for exhibitions and a cafeteria.

Panorama Adler Planetarium and Chicago skyline_Nick Lomb

A panorama of the Adler Planetarium and the Chicago skyline visible from there. Click on the image for a larger view (same with the other images in this post). Photo Nick Lomb

There have been more recent developments as well. Soon after my last visit in 2011 the new Grainger Sky Theatre opened; this 300-seat sky theatre is believed to be the most sophisticated in the world. Its 20 projectors are controlled by two supercomputers, 46 servers and 42 Nvidia Quadro GPUs (graphic processor units) and provide a screen image of 8000 by 8000 pixels or 64 megapixels. This image, which is refreshed 30 times a second, is sharper than the resolution of the human eye.

To experience the Grainger Sky Theatre I booked our little group into seeing the Adler’s premier show, Destination Solar System. It was not cheap, as to see it is necessary to purchase Anytime All Access passes at $34.95 adults and $29.95 for children. Still it is worth the cost for the 30-minute show plus the pass allows viewing all other shows at the planetarium together with all the exhibits.

Adler Planetarium from Willis Tower_Nick Lomb

The Adler Planetarium can be seen (circled) in this view from the Chicago Skydeck, on the 103rd floor of the Willis (formerly Sears) Tower, which is the second tallest building in the United States. Photo Nick Lomb

To my pleasant surprise the show was very much designed with young children in mind and perfectly suited the three 8 to 11 year olds in our group. The fun began in the entrance foyer as we waited to be allowed into theatre. We were told that it is the year 2096 and we were about to undertake a tour of the highlights of our solar system. Inside, after the theatre filled the show began with the blast off into space. There was a live guide Jesse who wandered among the audience telling us about what we were seeing, all the while bantering with both members of the audience and the spaceship’s computer Max.

The images were truly impressive with sights ranging from the surface of the Moon to activity on the Sun’s visible surface together with visits to Titan, Mars and the asteroid belt. Certainly all the highlights in the solar system were visited. At one stage there was a serious problem with our spaceship and Jesse heroically had to make an emergency repair (I do not want to give too much away). No surprise that the three children in our group loved the show.

I wondered about Jesse as he seemed far too good an actor to be a usual planetarium presenter. A little subsequent research told me that there are six Jesses, or possibly three Jesses and three Jessies as three are male and three female. They are all actors with experience in improvisation and were given some astronomical training by the Adler staff.

We did see another of a number of shows on offer at the Adler Planetarium, but Destination Solar System is highly recommended, especially for those with children in tow. Presented in a state-of-the-art sky theatre, the show is fun and in a refreshingly new style.

Daily cosmobite: Centaurus A

Published by Nick Lomb on No Comments

23_Centaurus A_ESOThe southern galaxy Centaurus A is relatively nearby at a distance of only 12 million light years from us. From a dark place away from city lights, it is easily visible through a small telescope. At its centre there is a massive black hole with a mass 55 million times that of our Sun.

Centaurus A. Courtesy ESO

Harry watches the gentle giant sunspot AR12109

Published by Nick Lomb on July 22, 2014 No Comments

ar12109captioned2

Changes in sunspot group AR12109 plotted on four separate days. Sketch and copyright Harry Roberts ©, all rights reserved

The first week of 2014 July saw the Sun’s south-eastern hemisphere ‘peppered’ with large and complex sunspots – some reached (suitably protected) ‘naked-eye’ size! A wondrous sight in white light (WL): they were somewhat disappointing in H-alpha, with few dark filaments and modest plages. Let’s consider one of the biggest: NOAA AR12109.

AR12109 rounded the east limb on July 2nd (Fig1), looking like a typical large single spot (McI: Hsx) but for some faint patches of following (f) penumbra that may have held small attendant spots. A day earlier there had been strong signs of a large group approaching, with a spiky ‘crown’ of small but bright surges sited at –10,219. As surges occur only around sunspot penumbrae, a cluster of ‘spikes’ at the limb suggested a big spot just behind it. When first seen on the 2nd the (p) spot was already 16º from the limb, i.e. in good ‘seeing’ it might have been detectable on the 1st.

By the 3rd (Fig2) it was clear that 2109 was a complex spot group with the large (p) spot and its conspicuous light bridge attended by dozens of small spots, many in chains, suggesting complex magnetic mixes. The (p) spot was sited at –8,222 and the most remote follower (f) at –6,214: it was a new sunspot group. Mt. Wilson polarities showed red 2200G (R22) in the (p) spot and violet 1300G (V13) in the follower (f). Helio freeware © Peter Meadows gave the group an area of 650 units: a large group given this weak solar cycle.

The 5th saw the group larger than 700 units (Fig3) with the previously ‘roundish’ (p) spot now changing shape while the followers developed larger irregular penumbrae. There were now some conspicuous surges or filaments emanating from the (p) spot with one looping out of the (p) and returning to the middle of the group after an excursion some 7º northwards.

Flare. A flare erupted along what was likely the polarity boundary between red and violet spots, beginning as a sub-flare at 00:21 and reaching GOES C4 at 00:25: a minor but ‘pretty’ event.

The preceding spot now had an umbral field of R24 while the (f) spots remained at low values. Mt Wilson workers who detected mixed fields in it assigned Hale DELTA configuration to the group on the 8th. I had no detailed log of it on that day – but on the 10th (Fig4) it was also Beta-Gamma-Delta with R2600G in the (p) spot. The tiny V13 (arrowed) was deemed a DELTA mix by Mt. Wilson, while I saw that spot as separated from its red siblings by a small penumbral gap. Much earlier NOAA had deemed the group Delta class based, it seems, on disc magnetograms rather than the ‘original’ Hale definition of ‘mixed fields within the one penumbra’.

This was a most impressive sunspot group – Earth is shown dotted in Fig4; large in area with complex Delta class fields, yet its flare activity never exceed GOES C-class during its disc transit. What was missing?

One key ingredient of flaring is helicity: the degree of ‘twist’ in umbral fields. Perhaps the solar dynamo is generating fields with less helicity and that, combined with low power fields, results in lesser flares? It is noted that the vast coronal canopies formed above active regions by the sunspot fields (SDO daily logs), currently seem rather modest when compared to earlier records (e.g. year 2011). Is this effect real?

Perhaps time and more research will tell. Meanwhile, AR12109 was a great sunspot to follow as it rapidly evolved during its stately transit of the solar disc; will it reappear around August 1st? Keep a watch for clusters of small bright surges at the southeastern limb.

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

22_Neptune ring_PIA02224_NASAEach of the gas giants in the outer solar system are circled by rings. The rings of the outermost planet Neptune were first discovered as arcs on this day in 1984. Five years later the Voyager 2 spacecraft imaged five rings as it passed the planet. One of these rings, the Adams ring, has five arcs some of which had been the ones discovered earlier.

Voyager 2 image of the rings of Neptune. Courtesy NASA/JPL

Daily cosmobite: a constellation of astronomers

Published by Nick Lomb on July 21, 2014 No Comments

21_ASA_ASA & macquarie UniversityAustralia’s research astronomers have gathered at Macquarie University for the annual scientific meeting of the Astronomical Society of Australia. They are discussing the latest studies of the origin of the Universe and the formation of galaxies as well the development of new instruments.

Part of conference logo. Courtesy ASA and Macquarie University

Search

About

The 'Observations' blog is run by the staff of Sydney Observatory which is located at Observatory Hill, The Rocks, in Sydney, Australia.

This site is for discussion purposes only and does not represent the official views of Sydney Observatory. Any views expressed on this website are those of the individual post author only. Sydney Observatory accepts no liability for the content of this site.

Please direct any correspondence about the content of the blog to:
observatory [at] phm.gov.au
and about web matters to:
web [at] phm.gov.au.