RASNZ_20_03_2019
Royal Astronomical Society of New Zealand
eNewsletter: No. 219, 20 March 2019 Affiliated Societies are welcome to reproduce any item in this email
newsletter or on the RASNZ website http://www.rasnz.org.nz/
in their own newsletters provided an acknowledgement of the source is
also included.
Contents
1. 2019 RASNZ Conference - New Plymouth
2. Call for Papers for 2019 RASNZ Conference
3. RASNZ Administrative Deadlines
4. The RASNZ Beatrice Hill-Tinsley Lecture Series
5. Space Weather Section Director Sought
6. Waharau Dark Sky Weekend 2019 -- April 5-7
7. International Dark Sky Week -- March 31 - April 7
8. The Solar System in April
9. Variable Stars South News
10. 2019 AAS Astrophotography Competition
11. 2020 Conference and RASNZ Centenary
12. Remembering Opportunity
13. Hubble & Gaia Weigh the Milky Way
14. Quotes
1. 2019 RASNZ Conference - New Plymouth
The annual RASNZ conference will be held in New Plymouth from Friday 17th until Sunday 19th May 2019.
You will find an announcement on RASNZ home page www.rasnz.org.nz - click on the "Read more" button to go to the conference information page. There you will find links to the on-line conference registration form, the online paper submission form, the conference brochure and a downloadable registration form (for those who want to fill out a form manually). Immediately following the conference in New Plymouth the 13th Trans-Tasman Symposium on Occultations will run from Monday to mid-day Tuesday.
For those who wish to take advantage of the special conference rate for accommodation at the venue (the Devon Hotel) the promo code is RASNZ2019. The conference brochure, available for download on the RASNZ's conference webpage has been updated with this information.
The RASNZ Conference webpage is updated with abstracts of papers as they are accepted so keep an eye on that page to see what will be on offer.
-- Glen Rowe, Chair, Standing Conference Committee.
2. Call for Papers for 2019 RASNZ Conference
It is a pleasure to announce that the next conference of the Royal Astronomical Society of New Zealand (RASNZ) will be held in at the Devon Hotel in New Plymouth over the weekend of 17th -19th May 2019. Our guest speaker will be Dr Lisa Kewley from the ANU in Canberra. This year there will be no Fellows’ Lecture, but this will be replaced by an address from RASNZ president Dr Nick Rattenbury. Titles and abstracts for these talks will be released when they are available.
The RASNZ standing conference committee (SCC) invites and encourages anyone interested in New Zealand Astronomy to submit oral or poster papers, with titles and abstracts due by 15th April 2019 or at such a time as the SCC deems the conference programme to be full. The link to the paper submission form can be found on the RASNZ Conference website www.rasnz.org.nz/Conference. Please note that you must be registered for the conference to give an oral presentation, and for your convenience a link has been provided if you wish to do this when you submit a paper.
Following the conference, the 13th Trans-Tasman Symposium on Occultations will be held, also at the Devon Hotel, starting on the morning of Monday 20th May and continuing until midday on Tuesday 21st May. You can register for the Symposium on the registration form for the RASNZ conference, and other information, including how to submit papers can be found at the RASNZ Occultation Section website www.occultations.org.nz. Note that this Symposium will be held only if there is sufficient interest, so please register as soon as you can.
We look forward to receiving your submissions and seeing you at the conference. Please feel free to forward this message to anyone who may find it of interest.
For further information on the RASNZ conference, registration details and associated events please visit the conference website at www.rasnz.org.nz/Conference
-- Warwick Kissling, RASNZ Standing Conference Committee
3. RASNZ Administrative Deadlines
Notices of motion to be submitted by April 5. Closing date no later than 6 weeks before the date of the meeting, Rule 71.
Kingdon-Tomlinson (K-T) applications: Applications for the next round of K-T applications must be with the secretary before the 1st May.
4. The RASNZ Beatrice Hill-Tinsley Lecture Series
The RASNZ Lecture Trust Inc. is pleased to announce that the 2019 Beatrice Hill Tinsley Lecturer is Babak A. Tafreshi. The lecture tour will take place in the second half of October. The Trust is now soliciting expressions of interest from Affiliated Societies in hosting Babak. Societies should send expressions of interest or any follow up questions to LectureTrust@rasnz.org.nz before April. See - https://www.rasnz.org.nz/rasnz/beatrice-hill-tinsley-lectures
-- copied from Keeping in Touch #31. 24th February 2019
5. Space Weather Section Director Sought
Dear Members,
Following his valuable term of service as Director of the Space Weather Section, Damien McNamara has chosen to step down from that position. Damien has become more involved with the challenges brought by increasing light pollution from new and additional sources. For and on behalf of the Council, I would like to thank Damien for his effort, energy and leadership.
Damien will formally step down as Director on 5 May 2019. At this time, Council is inviting any Member of the Society who wishes to be considered for the Directorship of the Space Weather Section to apply. Applications close at 5 p.m. 12 April 2019.
Applications are to be sent by post or email to the Secretary by the above deadline; secretary@rasnz.org.nz.
Applications are to include
1. a statement of interest which sets out the Member's interests in Space Weather, their past experience, their plans for leading the Section and any new initiatives for the Section's members, and
2. the names and contact details of two referees of whom Council can request further information about the applicant. Applications are to be no more than two sides of A4 in length, font size at least 12, font either Times New Roman or Ariel.
Yours,
Nicholas Rattenbury
RASNZ President
6. Waharau Dark Sky Weekend 2019 -- April 5-7
The Auckland Astronomical Society's (AAS) Waharau Dark Sky Weekend is from Friday 5th April to Sunday 7th April at Waharau Regional Park, 1748 E Coast Rd, Orere Point, Whakatiwai 2473 (about 1 hour's drive from central Auckland).
It will be a weekend of practical astronomy and dark sky observing. It is great opportunity to spend a weekend viewing the sky from a dark site on Moonless nights thought a range of different telescopes. Bring your telescope or binoculars, but if you don't have any there will be plenty there for you to look through.
During the day on Saturday there will be a full programme of practical astronomy – how to use equipment and various types of telescopes, new equipment demonstrations and an astrophotography workshop. Films will be shown in the early evening on Friday and Saturday.
Price:
AAS Member standard $30.00
Non-member standard $50.00
This price includes bunk bed type accommodation.
To book please email Gavin Logan: gavinlgn@gmail.com
giving the names of the people attending. Phone 021 144 1055.
Be quick, only limited spaces remain.
All people wishing to attend this event must book a place prior to the event.
-- Gavin Logan.
7. International Dark Sky Week -- March 31 - April 7
The International Dark Sky Association (IDA) is arranging International Dark Sky Week, March 31 - April 7. It is celebrate the work of our Dark Sky Places, spreading awareness about light pollution, and empowering new audiences to join the dark side! This year's theme is 'Open a Window to the Night'.
For ways to get involved with International Dark Sky Week (IDSW) the IDA have put together a few resources to use at your site and in your community, connect people with the night sky, and spread the word about the importance of dark skies. These include the 2019 IDSW Box folder for outreach materials https://darksky.box.com/s/4bcfkpzza7k6r0359wijp76j2vz43530
Containing:
2019 IDSW branded collateral for print or digital use. We teamed up with a local night sky artist to develop a postcard, poster, webpage header, and logo for your use. You may download and edit the files to add additional information (about an event for example), though we ask that you please keep the IDA logo as part of the design.
A sample 2019 IDSW Press Release. Help spread the word about IDSW near your Dark Sky Place by reaching out to local media contacts with information about light pollution and actions for participating in IDSW and protecting dark skies.
IDA Informational Brochures. Download and print IDA brochures to educate your audience about light pollution, its impacts, and tangible solutions. We have 5 different brochure topics available: wildlife, human health, energy waste, safety and security, and general.
Photos - Looking for night sky images? Check out these open source images https://darksky.app.box.com/s/ykxqyls3dul1gc7wk9qw4rl6radnc4d5
IDA Website - Check out our website for additional IDSW resources https://www.darksky.org/dsw-resources/
We’ll continue to add information to our webpage and social media about International Dark Sky Week.
Do you have plans for celebrating IDSW?
We want to spread the word about the important work your site is doing to protect dark skies, and encourage others to get involved. Share your plans and ideas with IDA and we’ll highlight them for our network.
Please take a moment to fill out this Google Form https://goo.gl/forms/ZW1ALhZwnkVupqtq2 with information about your event(s) so we can share with our network. We’ll use the information provided in our events calendar on darksky.org and encourage people to attend.
Are you promoting your event on Facebook? We’d love to collaborate with you! Please invite International Dark-Sky Association https://www.facebook.com/IDAdarksky/ to ‘co-host’ your event so we may easily share your event with our followers. Learn how to add a co-host at https://www.facebook.com/help/215235325174804?helpref=related
Not hosting an event? You can still participate! Perhaps you’re running a social media campaign or plan to contact a policy maker about light pollution. Let us know what you’re up to bring awareness to dark skies.
Keep us posted on the success of your event and/or activities! During and after IDSW, we plan to share the work of our IDSPlaces with our audience through our blog and social media channels https://www.darksky.org/get-involved/news/ .
Spread the word on social media! Join the fun online with hashtag #IDSW2019 .
-- Abridged email from Diana del Solar of the IDA, forwarded by Steve Butler.
8. The Solar System in April
Dates and times shown are NZDT (UT + 13 hours) up to Saturday 6 April and then NZST (UT + 12 hours). Rise and Set times are for Wellington. They will vary by a few minutes elsewhere in NZ. Data is adapted from that shown by GUIDE 9.
THE SUN and PLANETS in APRIL, Rise & Set, Mag. & Cons.
April 1 NZDT April 30 NZST
Mag Cons Rise Set Mag Cons Rise Set
SUN -26.7 Psc 7.33am 7.15pm -26.7 Ari 7.03am 5.31pm
Merc 0.8 Aqr 5.29am 6.17pm -0.3 Psc 5.16am 4.49pm
Venus -3.9 Aqr 4.38am 5.58pm -3.8 Psc 4.41am 4.27pm
Mars 1.5 Tau 11.50am 9.23pm .1.6 Tau 10.30am 7.37pm
Jup -2.2 Oph 10.45pm 1.47pm -2.4 Oph 7.49pm 10.51am
Sat 0.6 Sgr 12.41am 3.33pm 0.5 Sgr 9.50pm 12.41pm
Uran 5.9 Ari 9.17am 8.05pm 5.9 Ari 6.28am 5.11pm
Nep 8.0 Aqr 5.29am 6.20pm 7.9 Aqr 2.40am 3.28pm
Pluto 14.5 Sgr 12.54am 3.47pm 14.5 Sgr 10.00pm 12.54pm
April 1 NZDT April 30 NZST
Twilights morning evening morning evening
Civil: start 7.08am, end 7.41pm start 6.38am, end 5.58pm
Nautical: start 6.36am, end 8.13pm start 6.05am, end 6.31pm
Astro: start 6.04am, end 8.45pm start 5.33am, end 7.03pm
APRIL PHASES OF THE MOON, times NZDT/NZST (& UT)
New moon: April 5 at 9.50pm (08:50 UT)
First quarter: April 13 at 7.06am (Apr 12 19:06 UT)
Full Moon: April 19 at 11.12pm (11:12 UT)
Last quarter April 27 at 10.18am (Apr 26 22:18 UT)
PLANETS in April
Most planets are best observed as morning objects, although Jupiter will be well up in the later part of the evening by the end of April. Mars remains an early evening object.
MORNING SKY PLANETS
MERCURY makes its best morning appearance for the year during April rising two hours or more before the Sun all month. It reaches its greatest elongation, 28° west of the Sun, on the 12th. The planet, magnitude 0.3, will be 15° above the horizon an hour before sunrise, in a direction little to the north of east.
Mercury will be a few degrees below and to the right of Venus all month in the early dawn sky. The crescent moon will be 4° above and to the right of Mercury on the morning on April 3 when the planet will also be 23 arc-minutes from Neptune with the latter to the upper right of Mercury.
VENUS follows Mercury through the stars throughout April. It starts April about 10° above Mercury, closes in somewhat so that by mid month they will be about 4° apart, but then Mercury starts pulling ahead again so they end some 9° apart by the end of April.
The crescent moon will be a few degrees above Venus on the 2nd and below it on the 3rd.
JUPITER will be easily visible late evening by the end of April. The planet is stationary on April 11, so its position changes little during the month.
The gibbous moon is 2° from Jupiter as seen late evening on the 23rd.
SATURN rises close to 10pm at the end of April, so Saturn will be best observed as a morning object.
A lunar occultation of Saturn visible from New Zealand occurs on the morning of April 26. The planet will disappear behind the moon at the bright, sunlit limb. Saturn will reappear a little over an hour later from the dark, Earth shine lit, limb. The reappearance of the satellites Titan and Rhea will also be observable with a modest telescope.
A brief summary of NZST times and the offsets for Saturn limb contacts for a few centres are:
AUCKLAND Observatory Saturn
disappear 12:32:45.9am ±18.4s
reappear 01:41:50.9am ±20.8s
WELLINGTON Carter Obs
disappear 12:39:20.4am ±18.8s
reappear 01:47:18.5am ±20.8s
CHRISTCHURCH mid
disappear 12:42:58.6am ±19.2s
reappear 01:47:19.7am ±20.8s
DUNEDIN observatory
disappear 12:47:39.7am ±20.1s
reappear 01:46:59.2am ±21.8s
Intending observers need full details, including ring contact times, times for Titan and Rhea to reappear and position angles of events on the moon’s limb. The best way is to generate predictions using Dave Herald’s Occult program. If this is not available, contact Brian Loader, brian.loader@slingshot.co.nz, giving either the name of a nearby town or their site longitude and latitude.
The occultation is also visible from SE Australia where the moon will be very low, especially at the disappearance.
NEPTUNE is less than 1° from Mercury for the first four mornings of April and also just above and a little left of the 4.2 magnitude star phi Aqr. They should be visible in binoculars an hour or so before sunrise. The two planets are closest on the morning of April 3. That morning a very thin crescent moon will also be about 4° to the upper right of the planets. Neptune passes 5 arc-minutes from phi Sgr on the 10th.
PLUTO is just under 5° from Saturn on the 1st reducing to just over 3° by the 31st.
EVENING SKY PLANETS
MARS sets just over 2 hours after the Sun all month, so will be a low object to the west as the sky darkens. An hour after sunset it will be about 10° up and well round towards northwest. It will be 3° above the Pleiades on the 1st and passes some 6° below Aldebaran mid-month. The crescent moon will be 3° from Mars on the 9th.
URANUS is at conjunction with the Sun on April 23 NZST. It starts April as an evening object, following conjunction it moves into the morning sky
BRIGHTEST ASTEROIDS in APRIL, mag. const. time of transit
APRIL 1 NZDT APRIL 30 NZST
Mag Cons transit Mag Cons transit
(1) Ceres 8.2 Oph 5.36am 7.6 Oph 2.36am
(2) Pallas 7.9 Boo 2.45am 8.3 Boo 11.29pm
(4) Vesta 8.1 Psc 12.45pm 8.3 Cet 10.41am
(7) Iris 9.4 Crv 1.30am 9.9 Vir 10.14pm
CERES rises at 10.31 pm on the 1st and 7.29 pm on the 30th. The asteroid will be about 11.5° from Jupiter.
PALLAS is at opposition on the 9th at magnitude 7.9. The following night it will be very close to the magnitude 2.7 star, eta Boo..
VESTA rises an hour before the Sun on April 1 and nearly 2.5 hours before, at 4.37 am, on the 30th when it is about 3.5° from Venus. Vesta will also be just over 2° from Mercury on the morning of April 25.
IRIS is at opposition on the 4th. At magnitude 9.4 it will be a faint binocular object early in April.
-- Brian Loader
9. Variable Stars South News
Eta Carinae Project
Mark Blackford has advised that a new VSS Project called “Eta Carinae Photometric Campaign: 2019+2021” has been created and I strongly encourage anyone with the requisite equipment to participate. This arises from a recent request by Prof. Augusto Damineli (Instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo) requesting assistance from Variable Stars South with photometry of the bright southern variable eta Carinae.
The basic requirements are:
1) CCD images through V filter (and B filter if possible).
2) Image scale about 1 arcsec/pixel or more expanded.
3) Exposure times will be short so record 10 to 50 individual images to reduce effect of scintillation (you will probably need to use an aperture mask to reduce the flux enough to allow exposures of several seconds).
4) Calibrate each image then align and average stack the individual calibrated images.
5) Send the average stacked image to the project folder. Augusto can measure all images using IRAF to ensure homogeneous analysis
6) Image every available night.
Eta Carinae (star + Homunculus) has been brightening at a rate ΔV ~0.02 mag/yr since 2000. In 2010 the central star brightness overcame that of the reflection nebula, which remained almost constant (V~5.46). This is due to the fact that the central star is obscured by a natural coronagraph mask which is dissipating, a process that will end in 2032 (+/-4 yr).
The second major feature in Eta’s light-curve is the Orbital Modulation. It has an amplitude of ΔV~0.3 and is strictly periodic (P = 2023d or 5.538yr, the orbital period of the companion star). It is caused by the distorted shape of the primary’s stellar wind as it rotates. The distortion is shaped by the cavity produced by the wind-wind collision. Observing the system up to the next maximum of the Orbital Modulation (early 2021) is crucial to obtain data for a 3D model of such an interesting mechanism (Extract from VSS web-site)
More information on the campaign can be found via the link below, or contact Mark Blackford via the website.
https://www.variablestarssouth.org/eta-carinae-photometric-campaign-20192021/
-- Alan Baldwin
10. 2019 AAS Astrophotography Competition
Calling all Astrophotographers, it's that time of year again, time to get your entries in for the 2019 New Zealand Astrophotography competition.
This year we are super lucky to have the "Bad Astronomer" Phil Plait as judge for the competition. Phil is an American astronomer, sceptic, writer and popular science blogger. Phil is best known for debunking misconceptions in Astronomy but is also a well-known Astrophotography enthusiast. For more on Phil see the Auckland Astronomical Society's website.
Australian Sky & Telescope are sponsoring both the Deep Sky category and the Nightscape / Artistic category. The winners of these categories will receive a one year subscription to the magazine as well as having their images printed in it.
Astronz are sponsoring the Solar System category with a $300 Astronz gift voucher. The Auckland Astronomical Society will also provide a cash prize for each category winner.
Auckland's Stardome Observatory and Planetarium will print a selection of the entrants images for an astrophotography exhibition that will be displayed at Stardome after the competition awards are announced. The exhibition will then tour around New Zealand at various events and galleries.
The competition cut-off date is the September 30 and the competition awards will be announced at the Auckland Astronomical Society's annual Burbidge dinner. Keep an eye on the AAS website for details.
The competition rules and entry forms can be found on the homepage of the Auckland Astronomical Society website
https://www.astronomy.org.nz/new/public/default.aspx
-- Adapted from a note to the nzastronomers group by Jonathan Green.
11. 2020 Conference and RASNZ Centenary
The 2020 Conference will be held 8-10 May at Wellington with the Wharewaka Function Centre the venue (near the Michael Fowler Centre) in downtown Wellington. The Wellington Astronomical Society is hosting this conference.
2020 marks a significant milestone in the life of the Society as it was founded in November 1920 with 75 members.
The SCC invites ideas from members how the Society might commemorate its centenary at next year’s conference. Please send your suggestions to the SCC at conference@rasnz.org.nz.
-- Glen Rowe, Chair, Standing Conference Committee
12. Remembering Opportunity
It travelled more than 500m kilometres simply as a passenger, sleeping dreamless, vacuum-packed. The five-and-a-half-month voyage was devoid of all interest until the very end, when the spacecraft lost 20,000kph of its velocity in just over six minutes as it plunged through an alien sky to the desert below. Parachutes spread and airbags deployed. The package bounced, rolled and came to rest.
Four hours after landing on January 25th 2004, it opened its eyes. Its makers, back on Earth, looked through them at a landing site as perfect as they could have wished for. Opportunity’s landing on Meridiani Planum, a little south of the Martian equator, had not been a particularly precise affair — it could have come down anywhere in an ellipse some 100km long and 18km wide. But by chance the spot where it had ended up, about 25km from the centre of the target, was inside a small crater dug out by a meteorite impact. On the side of that crater the scientists saw straight away the distinctive strata of sedimentary rock. Nothing of the sort had ever before been seen beyond the Earth. It was exactly the type of thing the robot had been sent to find.
Opportunity was officially MER-B, the second of the two rovers of the Mars Exploration Rover programme; MER-A, Spirit, had landed a few weeks earlier in the great Gusev Crater, almost half the planet away. Unofficially, it was Oppy, and often a she. The two rovers’ missions were due to last 90 sols — a sol being the 24 hours and 40 minutes it takes Mars to turn on its axis. Faced with that time limit, Opportunity’s minders were thrilled not to have to spend any of those precious sols just looking for interesting rocks.
For the first 56 sols, Opportunity never strayed more than ten metres from that propitious landing site. It took pictures with its various cameras, ground holes with its little rasping drill, dug a trench by spinning one wheel while it kept the others locked, measured the spectra of various minerals. The scientists concluded that the sediments they saw had been laid down in a salty dying sea. If that had been all Opportunity had ever told them, the mission would have been counted a great success.
But on Sol 57, it ventured out into the wider world.
Guided by pictures from satellites above, Opportunity headed for a deeper crater, Endurance, a kilometre or so away. It drove down into it and looked around further, poking and prodding for the rest of the year. A human geologist might have accomplished as much or more by way of assessment in a leisurely afternoon. But the nearest human geologists were on another planet, and likely to remain there for some decades to come.
After climbing back out of Endurance — no one had known whether it would be able to — Opportunity was sent off to inspect the jettisoned heat-shield that had protected it as it burned down through the Martian atmosphere, now a glinting monument on the pockmarked plain. It was not the only thing that had fallen from the sky. As it rolled on, Opportunity came across a meteorite, its lithology distinctively un-Martian. Later it took a little video of Phobos, the larger of Mars’s small moons, passing as a shadow across the face of the Sun.
On Sol 946, in September 2006, Opportunity reached Victoria Crater, seven kilometres from its landing site, 800 metres across. Its makers knew that the 90-sol lifetime they had promised for Opportunity and Spirit was conservative, a low bar to ensure some kudos for “mission accomplished”. But none had expected it to be surpassed by a factor of ten.
That said, it had not all been plain rolling. Opportunity had spent a few harrowing sols stuck in sand at Purgatory Ripple; later, one of its steering motors failed. While it was exploring Victoria it was caught in a global dust-storm that cut it off from Earth and covered its solar panels with dirt. Happily, though, the same winds that drove the storms also blew the panels clean, or cleaner, after their passing. A joint in the shoulder of its robot arm, dicky since the mission started, finally seized up.
On March 30th 2011, Sol 2,155 of its mission to Gusev, Spirit failed to check in with Earth by radio as scheduled; it was never heard from again. Opportunity continued its long trek to Endeavour crater, 1,000 times larger than the crater in which it had started off. The point where it reached the rim was named Spirit Point, in memoriam. On August 6th 2012 a newer, bigger rover, Curiosity, landed at the foot of Aeolis Mons, thousands of kilometres away. Opportunity looked after itself for nine days to allow the scientists and engineers to make a fuss of the newcomer, then set out to study the intriguing smectite clays that a European orbiter had detected on Cape York, a peak further along Endeavour’s rim.
As the unexpected years went by, Opportunity continued along the hilly rim of Endeavour until it came to Perseverance Valley, which cuts through towards the crater floor. It was heading down the valley when, on June 10th 2018 — Sol 5,111, well over seven Martian years of service — another dust storm cut it off from Sun and Earth. When, after months, the global storm subsided, the rover’s minders, now family, waited for its solar panels to be blown clean. It appears they were not. After over 1,000 messages attempting to restore contact, Opportunity was declared lost on February 12th.
If more than a handful of people ever get to explore Mars in person, surely one day someone will follow its tracks down Perseverance, looking for the mast on which its cameras are mounted — separated for stereoscopy, easily anthropomorphised — to honour a pioneer who travelled far and provided insight after insight into the history of Mars. Until then, imagine her as she was photographed by the orbiting HiRise camera after first reaching the scalloped rim of Victoria, looking down onto its rolling dunes: a tiny speck perched on a promontory peak, a new planet swimming before her eagle eyes, watched in silence from the skies.
-- This article appeared in the Obituary section of the print edition of The Economist, February 21, 2019, p.82, under the headline "Remembering a robot".
13. Hubble & Gaia Weigh the Milky Way
The mass of the Milky Way is one of the most fundamental measurements astronomers can make about our galactic home. However, despite decades of intense effort, even the best available estimates of the Milky Way’s mass disagree wildly. Now, by combining new data from the European Space Agency (ESA) Gaia mission with observations made with the NASA/ESA Hubble Space Telescope (HST), astronomers have found that the Milky Way weighs in at about 1.5 trillion solar masses within a radius of 129 000 light-years from the galactic centre.
Previous estimates of the mass of the Milky Way ranged from 500 billion to 3 trillion times the mass of the Sun. This huge uncertainty arose primarily from the different methods used for measuring the distribution of dark matter — which makes up about 90% of the mass of the galaxy.
To weigh the Milky Way the team measured the velocities of globular clusters — dense star clusters that orbit the spiral disc of the galaxy at great distances. The more massive a galaxy, the faster its clusters move under the pull of its gravity. Most previous measurements have used the speed at which a cluster is approaching or receding from Earth, the velocity along our line of sight. Measurements from the HST and Gaia allowed the sideways movement of the clusters to be also determined, giving their space motion in 3D. From that the galactic mass could be calculated.
The group used Gaia’s second data release as a basis for their study. Gaia was designed to create a precise three-dimensional map of astronomical objects throughout the Milky Way and to track their motions. Its second data release includes measurements of globular clusters as far as 65 000 light-years from Earth.
The team combined this data with Hubble’s unparalleled sensitivity and observational legacy. Observations from Hubble allowed faint and distant globular clusters, as far as 130 000 light-years from Earth, to be added to the study. As Hubble has been observing some of these objects for a decade, it was possible to accurately track the velocities of these clusters as well.
By combining Gaia’s measurements of 34 globular clusters with measurements of 12 more distant clusters from Hubble the team was able to compute the Milky Way’s mass in a way that would be impossible without the two space telescopes.
Until now, not knowing the precise mass of the Milky Way has presented a problem for attempts to answer a lot of cosmological questions. The dark matter content of a galaxy and its distribution are intrinsically linked to the formation and growth of structures in the Universe. Accurately determining the mass for the Milky Way gives us a clearer understanding of where our galaxy sits in a cosmological context.
See the original item at https://www.spacetelescope.org/news/heic1905/
-- Abridged from the above item forwarded by Karen Pollard.
14. Quotes
“For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.” -- Richard Feynman.
“To do real good physics work, you do need absolute solid lengths of time … it needs a lot of concentration … if you have a job administrating anything, you don’t have the time. So I have invented another myth for myself: that I’m irresponsible. I’m actively irresponsible. I tell everyone I don’t do anything. If anyone asks me to be on a committee …‘no’ I tell them: I’m irresponsible.”
-- Richard Feynman, who explained his method in a 1981 television interview. Quoted in
https://www.chronicle.com/interactives/is-email-making-professors-stupid
Alan Gilmore Phone: 03 680 6817
P.O. Box 57 alan.gilmore@canterbury.ac.nz
Lake Tekapo 7945
New Zealand
eNewsletter: No. 219, 20 March 2019 Affiliated Societies are welcome to reproduce any item in this email
newsletter or on the RASNZ website http://www.rasnz.org.nz/
in their own newsletters provided an acknowledgement of the source is
also included.
Contents
1. 2019 RASNZ Conference - New Plymouth
2. Call for Papers for 2019 RASNZ Conference
3. RASNZ Administrative Deadlines
4. The RASNZ Beatrice Hill-Tinsley Lecture Series
5. Space Weather Section Director Sought
6. Waharau Dark Sky Weekend 2019 -- April 5-7
7. International Dark Sky Week -- March 31 - April 7
8. The Solar System in April
9. Variable Stars South News
10. 2019 AAS Astrophotography Competition
11. 2020 Conference and RASNZ Centenary
12. Remembering Opportunity
13. Hubble & Gaia Weigh the Milky Way
14. Quotes
1. 2019 RASNZ Conference - New Plymouth
The annual RASNZ conference will be held in New Plymouth from Friday 17th until Sunday 19th May 2019.
You will find an announcement on RASNZ home page www.rasnz.org.nz - click on the "Read more" button to go to the conference information page. There you will find links to the on-line conference registration form, the online paper submission form, the conference brochure and a downloadable registration form (for those who want to fill out a form manually). Immediately following the conference in New Plymouth the 13th Trans-Tasman Symposium on Occultations will run from Monday to mid-day Tuesday.
For those who wish to take advantage of the special conference rate for accommodation at the venue (the Devon Hotel) the promo code is RASNZ2019. The conference brochure, available for download on the RASNZ's conference webpage has been updated with this information.
The RASNZ Conference webpage is updated with abstracts of papers as they are accepted so keep an eye on that page to see what will be on offer.
-- Glen Rowe, Chair, Standing Conference Committee.
2. Call for Papers for 2019 RASNZ Conference
It is a pleasure to announce that the next conference of the Royal Astronomical Society of New Zealand (RASNZ) will be held in at the Devon Hotel in New Plymouth over the weekend of 17th -19th May 2019. Our guest speaker will be Dr Lisa Kewley from the ANU in Canberra. This year there will be no Fellows’ Lecture, but this will be replaced by an address from RASNZ president Dr Nick Rattenbury. Titles and abstracts for these talks will be released when they are available.
The RASNZ standing conference committee (SCC) invites and encourages anyone interested in New Zealand Astronomy to submit oral or poster papers, with titles and abstracts due by 15th April 2019 or at such a time as the SCC deems the conference programme to be full. The link to the paper submission form can be found on the RASNZ Conference website www.rasnz.org.nz/Conference. Please note that you must be registered for the conference to give an oral presentation, and for your convenience a link has been provided if you wish to do this when you submit a paper.
Following the conference, the 13th Trans-Tasman Symposium on Occultations will be held, also at the Devon Hotel, starting on the morning of Monday 20th May and continuing until midday on Tuesday 21st May. You can register for the Symposium on the registration form for the RASNZ conference, and other information, including how to submit papers can be found at the RASNZ Occultation Section website www.occultations.org.nz. Note that this Symposium will be held only if there is sufficient interest, so please register as soon as you can.
We look forward to receiving your submissions and seeing you at the conference. Please feel free to forward this message to anyone who may find it of interest.
For further information on the RASNZ conference, registration details and associated events please visit the conference website at www.rasnz.org.nz/Conference
-- Warwick Kissling, RASNZ Standing Conference Committee
3. RASNZ Administrative Deadlines
Notices of motion to be submitted by April 5. Closing date no later than 6 weeks before the date of the meeting, Rule 71.
Kingdon-Tomlinson (K-T) applications: Applications for the next round of K-T applications must be with the secretary before the 1st May.
4. The RASNZ Beatrice Hill-Tinsley Lecture Series
The RASNZ Lecture Trust Inc. is pleased to announce that the 2019 Beatrice Hill Tinsley Lecturer is Babak A. Tafreshi. The lecture tour will take place in the second half of October. The Trust is now soliciting expressions of interest from Affiliated Societies in hosting Babak. Societies should send expressions of interest or any follow up questions to LectureTrust@rasnz.org.nz before April. See - https://www.rasnz.org.nz/rasnz/beatrice-hill-tinsley-lectures
-- copied from Keeping in Touch #31. 24th February 2019
5. Space Weather Section Director Sought
Dear Members,
Following his valuable term of service as Director of the Space Weather Section, Damien McNamara has chosen to step down from that position. Damien has become more involved with the challenges brought by increasing light pollution from new and additional sources. For and on behalf of the Council, I would like to thank Damien for his effort, energy and leadership.
Damien will formally step down as Director on 5 May 2019. At this time, Council is inviting any Member of the Society who wishes to be considered for the Directorship of the Space Weather Section to apply. Applications close at 5 p.m. 12 April 2019.
Applications are to be sent by post or email to the Secretary by the above deadline; secretary@rasnz.org.nz.
Applications are to include
1. a statement of interest which sets out the Member's interests in Space Weather, their past experience, their plans for leading the Section and any new initiatives for the Section's members, and
2. the names and contact details of two referees of whom Council can request further information about the applicant. Applications are to be no more than two sides of A4 in length, font size at least 12, font either Times New Roman or Ariel.
Yours,
Nicholas Rattenbury
RASNZ President
6. Waharau Dark Sky Weekend 2019 -- April 5-7
The Auckland Astronomical Society's (AAS) Waharau Dark Sky Weekend is from Friday 5th April to Sunday 7th April at Waharau Regional Park, 1748 E Coast Rd, Orere Point, Whakatiwai 2473 (about 1 hour's drive from central Auckland).
It will be a weekend of practical astronomy and dark sky observing. It is great opportunity to spend a weekend viewing the sky from a dark site on Moonless nights thought a range of different telescopes. Bring your telescope or binoculars, but if you don't have any there will be plenty there for you to look through.
During the day on Saturday there will be a full programme of practical astronomy – how to use equipment and various types of telescopes, new equipment demonstrations and an astrophotography workshop. Films will be shown in the early evening on Friday and Saturday.
Price:
AAS Member standard $30.00
Non-member standard $50.00
This price includes bunk bed type accommodation.
To book please email Gavin Logan: gavinlgn@gmail.com
giving the names of the people attending. Phone 021 144 1055.
Be quick, only limited spaces remain.
All people wishing to attend this event must book a place prior to the event.
-- Gavin Logan.
7. International Dark Sky Week -- March 31 - April 7
The International Dark Sky Association (IDA) is arranging International Dark Sky Week, March 31 - April 7. It is celebrate the work of our Dark Sky Places, spreading awareness about light pollution, and empowering new audiences to join the dark side! This year's theme is 'Open a Window to the Night'.
For ways to get involved with International Dark Sky Week (IDSW) the IDA have put together a few resources to use at your site and in your community, connect people with the night sky, and spread the word about the importance of dark skies. These include the 2019 IDSW Box folder for outreach materials https://darksky.box.com/s/4bcfkpzza7k6r0359wijp76j2vz43530
Containing:
2019 IDSW branded collateral for print or digital use. We teamed up with a local night sky artist to develop a postcard, poster, webpage header, and logo for your use. You may download and edit the files to add additional information (about an event for example), though we ask that you please keep the IDA logo as part of the design.
A sample 2019 IDSW Press Release. Help spread the word about IDSW near your Dark Sky Place by reaching out to local media contacts with information about light pollution and actions for participating in IDSW and protecting dark skies.
IDA Informational Brochures. Download and print IDA brochures to educate your audience about light pollution, its impacts, and tangible solutions. We have 5 different brochure topics available: wildlife, human health, energy waste, safety and security, and general.
Photos - Looking for night sky images? Check out these open source images https://darksky.app.box.com/s/ykxqyls3dul1gc7wk9qw4rl6radnc4d5
IDA Website - Check out our website for additional IDSW resources https://www.darksky.org/dsw-resources/
We’ll continue to add information to our webpage and social media about International Dark Sky Week.
Do you have plans for celebrating IDSW?
We want to spread the word about the important work your site is doing to protect dark skies, and encourage others to get involved. Share your plans and ideas with IDA and we’ll highlight them for our network.
Please take a moment to fill out this Google Form https://goo.gl/forms/ZW1ALhZwnkVupqtq2 with information about your event(s) so we can share with our network. We’ll use the information provided in our events calendar on darksky.org and encourage people to attend.
Are you promoting your event on Facebook? We’d love to collaborate with you! Please invite International Dark-Sky Association https://www.facebook.com/IDAdarksky/ to ‘co-host’ your event so we may easily share your event with our followers. Learn how to add a co-host at https://www.facebook.com/help/215235325174804?helpref=related
Not hosting an event? You can still participate! Perhaps you’re running a social media campaign or plan to contact a policy maker about light pollution. Let us know what you’re up to bring awareness to dark skies.
Keep us posted on the success of your event and/or activities! During and after IDSW, we plan to share the work of our IDSPlaces with our audience through our blog and social media channels https://www.darksky.org/get-involved/news/ .
Spread the word on social media! Join the fun online with hashtag #IDSW2019 .
-- Abridged email from Diana del Solar of the IDA, forwarded by Steve Butler.
8. The Solar System in April
Dates and times shown are NZDT (UT + 13 hours) up to Saturday 6 April and then NZST (UT + 12 hours). Rise and Set times are for Wellington. They will vary by a few minutes elsewhere in NZ. Data is adapted from that shown by GUIDE 9.
THE SUN and PLANETS in APRIL, Rise & Set, Mag. & Cons.
April 1 NZDT April 30 NZST
Mag Cons Rise Set Mag Cons Rise Set
SUN -26.7 Psc 7.33am 7.15pm -26.7 Ari 7.03am 5.31pm
Merc 0.8 Aqr 5.29am 6.17pm -0.3 Psc 5.16am 4.49pm
Venus -3.9 Aqr 4.38am 5.58pm -3.8 Psc 4.41am 4.27pm
Mars 1.5 Tau 11.50am 9.23pm .1.6 Tau 10.30am 7.37pm
Jup -2.2 Oph 10.45pm 1.47pm -2.4 Oph 7.49pm 10.51am
Sat 0.6 Sgr 12.41am 3.33pm 0.5 Sgr 9.50pm 12.41pm
Uran 5.9 Ari 9.17am 8.05pm 5.9 Ari 6.28am 5.11pm
Nep 8.0 Aqr 5.29am 6.20pm 7.9 Aqr 2.40am 3.28pm
Pluto 14.5 Sgr 12.54am 3.47pm 14.5 Sgr 10.00pm 12.54pm
April 1 NZDT April 30 NZST
Twilights morning evening morning evening
Civil: start 7.08am, end 7.41pm start 6.38am, end 5.58pm
Nautical: start 6.36am, end 8.13pm start 6.05am, end 6.31pm
Astro: start 6.04am, end 8.45pm start 5.33am, end 7.03pm
APRIL PHASES OF THE MOON, times NZDT/NZST (& UT)
New moon: April 5 at 9.50pm (08:50 UT)
First quarter: April 13 at 7.06am (Apr 12 19:06 UT)
Full Moon: April 19 at 11.12pm (11:12 UT)
Last quarter April 27 at 10.18am (Apr 26 22:18 UT)
PLANETS in April
Most planets are best observed as morning objects, although Jupiter will be well up in the later part of the evening by the end of April. Mars remains an early evening object.
MORNING SKY PLANETS
MERCURY makes its best morning appearance for the year during April rising two hours or more before the Sun all month. It reaches its greatest elongation, 28° west of the Sun, on the 12th. The planet, magnitude 0.3, will be 15° above the horizon an hour before sunrise, in a direction little to the north of east.
Mercury will be a few degrees below and to the right of Venus all month in the early dawn sky. The crescent moon will be 4° above and to the right of Mercury on the morning on April 3 when the planet will also be 23 arc-minutes from Neptune with the latter to the upper right of Mercury.
VENUS follows Mercury through the stars throughout April. It starts April about 10° above Mercury, closes in somewhat so that by mid month they will be about 4° apart, but then Mercury starts pulling ahead again so they end some 9° apart by the end of April.
The crescent moon will be a few degrees above Venus on the 2nd and below it on the 3rd.
JUPITER will be easily visible late evening by the end of April. The planet is stationary on April 11, so its position changes little during the month.
The gibbous moon is 2° from Jupiter as seen late evening on the 23rd.
SATURN rises close to 10pm at the end of April, so Saturn will be best observed as a morning object.
A lunar occultation of Saturn visible from New Zealand occurs on the morning of April 26. The planet will disappear behind the moon at the bright, sunlit limb. Saturn will reappear a little over an hour later from the dark, Earth shine lit, limb. The reappearance of the satellites Titan and Rhea will also be observable with a modest telescope.
A brief summary of NZST times and the offsets for Saturn limb contacts for a few centres are:
AUCKLAND Observatory Saturn
disappear 12:32:45.9am ±18.4s
reappear 01:41:50.9am ±20.8s
WELLINGTON Carter Obs
disappear 12:39:20.4am ±18.8s
reappear 01:47:18.5am ±20.8s
CHRISTCHURCH mid
disappear 12:42:58.6am ±19.2s
reappear 01:47:19.7am ±20.8s
DUNEDIN observatory
disappear 12:47:39.7am ±20.1s
reappear 01:46:59.2am ±21.8s
Intending observers need full details, including ring contact times, times for Titan and Rhea to reappear and position angles of events on the moon’s limb. The best way is to generate predictions using Dave Herald’s Occult program. If this is not available, contact Brian Loader, brian.loader@slingshot.co.nz, giving either the name of a nearby town or their site longitude and latitude.
The occultation is also visible from SE Australia where the moon will be very low, especially at the disappearance.
NEPTUNE is less than 1° from Mercury for the first four mornings of April and also just above and a little left of the 4.2 magnitude star phi Aqr. They should be visible in binoculars an hour or so before sunrise. The two planets are closest on the morning of April 3. That morning a very thin crescent moon will also be about 4° to the upper right of the planets. Neptune passes 5 arc-minutes from phi Sgr on the 10th.
PLUTO is just under 5° from Saturn on the 1st reducing to just over 3° by the 31st.
EVENING SKY PLANETS
MARS sets just over 2 hours after the Sun all month, so will be a low object to the west as the sky darkens. An hour after sunset it will be about 10° up and well round towards northwest. It will be 3° above the Pleiades on the 1st and passes some 6° below Aldebaran mid-month. The crescent moon will be 3° from Mars on the 9th.
URANUS is at conjunction with the Sun on April 23 NZST. It starts April as an evening object, following conjunction it moves into the morning sky
BRIGHTEST ASTEROIDS in APRIL, mag. const. time of transit
APRIL 1 NZDT APRIL 30 NZST
Mag Cons transit Mag Cons transit
(1) Ceres 8.2 Oph 5.36am 7.6 Oph 2.36am
(2) Pallas 7.9 Boo 2.45am 8.3 Boo 11.29pm
(4) Vesta 8.1 Psc 12.45pm 8.3 Cet 10.41am
(7) Iris 9.4 Crv 1.30am 9.9 Vir 10.14pm
CERES rises at 10.31 pm on the 1st and 7.29 pm on the 30th. The asteroid will be about 11.5° from Jupiter.
PALLAS is at opposition on the 9th at magnitude 7.9. The following night it will be very close to the magnitude 2.7 star, eta Boo..
VESTA rises an hour before the Sun on April 1 and nearly 2.5 hours before, at 4.37 am, on the 30th when it is about 3.5° from Venus. Vesta will also be just over 2° from Mercury on the morning of April 25.
IRIS is at opposition on the 4th. At magnitude 9.4 it will be a faint binocular object early in April.
-- Brian Loader
9. Variable Stars South News
Eta Carinae Project
Mark Blackford has advised that a new VSS Project called “Eta Carinae Photometric Campaign: 2019+2021” has been created and I strongly encourage anyone with the requisite equipment to participate. This arises from a recent request by Prof. Augusto Damineli (Instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo) requesting assistance from Variable Stars South with photometry of the bright southern variable eta Carinae.
The basic requirements are:
1) CCD images through V filter (and B filter if possible).
2) Image scale about 1 arcsec/pixel or more expanded.
3) Exposure times will be short so record 10 to 50 individual images to reduce effect of scintillation (you will probably need to use an aperture mask to reduce the flux enough to allow exposures of several seconds).
4) Calibrate each image then align and average stack the individual calibrated images.
5) Send the average stacked image to the project folder. Augusto can measure all images using IRAF to ensure homogeneous analysis
6) Image every available night.
Eta Carinae (star + Homunculus) has been brightening at a rate ΔV ~0.02 mag/yr since 2000. In 2010 the central star brightness overcame that of the reflection nebula, which remained almost constant (V~5.46). This is due to the fact that the central star is obscured by a natural coronagraph mask which is dissipating, a process that will end in 2032 (+/-4 yr).
The second major feature in Eta’s light-curve is the Orbital Modulation. It has an amplitude of ΔV~0.3 and is strictly periodic (P = 2023d or 5.538yr, the orbital period of the companion star). It is caused by the distorted shape of the primary’s stellar wind as it rotates. The distortion is shaped by the cavity produced by the wind-wind collision. Observing the system up to the next maximum of the Orbital Modulation (early 2021) is crucial to obtain data for a 3D model of such an interesting mechanism (Extract from VSS web-site)
More information on the campaign can be found via the link below, or contact Mark Blackford via the website.
https://www.variablestarssouth.org/eta-carinae-photometric-campaign-20192021/
-- Alan Baldwin
10. 2019 AAS Astrophotography Competition
Calling all Astrophotographers, it's that time of year again, time to get your entries in for the 2019 New Zealand Astrophotography competition.
This year we are super lucky to have the "Bad Astronomer" Phil Plait as judge for the competition. Phil is an American astronomer, sceptic, writer and popular science blogger. Phil is best known for debunking misconceptions in Astronomy but is also a well-known Astrophotography enthusiast. For more on Phil see the Auckland Astronomical Society's website.
Australian Sky & Telescope are sponsoring both the Deep Sky category and the Nightscape / Artistic category. The winners of these categories will receive a one year subscription to the magazine as well as having their images printed in it.
Astronz are sponsoring the Solar System category with a $300 Astronz gift voucher. The Auckland Astronomical Society will also provide a cash prize for each category winner.
Auckland's Stardome Observatory and Planetarium will print a selection of the entrants images for an astrophotography exhibition that will be displayed at Stardome after the competition awards are announced. The exhibition will then tour around New Zealand at various events and galleries.
The competition cut-off date is the September 30 and the competition awards will be announced at the Auckland Astronomical Society's annual Burbidge dinner. Keep an eye on the AAS website for details.
The competition rules and entry forms can be found on the homepage of the Auckland Astronomical Society website
https://www.astronomy.org.nz/new/public/default.aspx
-- Adapted from a note to the nzastronomers group by Jonathan Green.
11. 2020 Conference and RASNZ Centenary
The 2020 Conference will be held 8-10 May at Wellington with the Wharewaka Function Centre the venue (near the Michael Fowler Centre) in downtown Wellington. The Wellington Astronomical Society is hosting this conference.
2020 marks a significant milestone in the life of the Society as it was founded in November 1920 with 75 members.
The SCC invites ideas from members how the Society might commemorate its centenary at next year’s conference. Please send your suggestions to the SCC at conference@rasnz.org.nz.
-- Glen Rowe, Chair, Standing Conference Committee
12. Remembering Opportunity
It travelled more than 500m kilometres simply as a passenger, sleeping dreamless, vacuum-packed. The five-and-a-half-month voyage was devoid of all interest until the very end, when the spacecraft lost 20,000kph of its velocity in just over six minutes as it plunged through an alien sky to the desert below. Parachutes spread and airbags deployed. The package bounced, rolled and came to rest.
Four hours after landing on January 25th 2004, it opened its eyes. Its makers, back on Earth, looked through them at a landing site as perfect as they could have wished for. Opportunity’s landing on Meridiani Planum, a little south of the Martian equator, had not been a particularly precise affair — it could have come down anywhere in an ellipse some 100km long and 18km wide. But by chance the spot where it had ended up, about 25km from the centre of the target, was inside a small crater dug out by a meteorite impact. On the side of that crater the scientists saw straight away the distinctive strata of sedimentary rock. Nothing of the sort had ever before been seen beyond the Earth. It was exactly the type of thing the robot had been sent to find.
Opportunity was officially MER-B, the second of the two rovers of the Mars Exploration Rover programme; MER-A, Spirit, had landed a few weeks earlier in the great Gusev Crater, almost half the planet away. Unofficially, it was Oppy, and often a she. The two rovers’ missions were due to last 90 sols — a sol being the 24 hours and 40 minutes it takes Mars to turn on its axis. Faced with that time limit, Opportunity’s minders were thrilled not to have to spend any of those precious sols just looking for interesting rocks.
For the first 56 sols, Opportunity never strayed more than ten metres from that propitious landing site. It took pictures with its various cameras, ground holes with its little rasping drill, dug a trench by spinning one wheel while it kept the others locked, measured the spectra of various minerals. The scientists concluded that the sediments they saw had been laid down in a salty dying sea. If that had been all Opportunity had ever told them, the mission would have been counted a great success.
But on Sol 57, it ventured out into the wider world.
Guided by pictures from satellites above, Opportunity headed for a deeper crater, Endurance, a kilometre or so away. It drove down into it and looked around further, poking and prodding for the rest of the year. A human geologist might have accomplished as much or more by way of assessment in a leisurely afternoon. But the nearest human geologists were on another planet, and likely to remain there for some decades to come.
After climbing back out of Endurance — no one had known whether it would be able to — Opportunity was sent off to inspect the jettisoned heat-shield that had protected it as it burned down through the Martian atmosphere, now a glinting monument on the pockmarked plain. It was not the only thing that had fallen from the sky. As it rolled on, Opportunity came across a meteorite, its lithology distinctively un-Martian. Later it took a little video of Phobos, the larger of Mars’s small moons, passing as a shadow across the face of the Sun.
On Sol 946, in September 2006, Opportunity reached Victoria Crater, seven kilometres from its landing site, 800 metres across. Its makers knew that the 90-sol lifetime they had promised for Opportunity and Spirit was conservative, a low bar to ensure some kudos for “mission accomplished”. But none had expected it to be surpassed by a factor of ten.
That said, it had not all been plain rolling. Opportunity had spent a few harrowing sols stuck in sand at Purgatory Ripple; later, one of its steering motors failed. While it was exploring Victoria it was caught in a global dust-storm that cut it off from Earth and covered its solar panels with dirt. Happily, though, the same winds that drove the storms also blew the panels clean, or cleaner, after their passing. A joint in the shoulder of its robot arm, dicky since the mission started, finally seized up.
On March 30th 2011, Sol 2,155 of its mission to Gusev, Spirit failed to check in with Earth by radio as scheduled; it was never heard from again. Opportunity continued its long trek to Endeavour crater, 1,000 times larger than the crater in which it had started off. The point where it reached the rim was named Spirit Point, in memoriam. On August 6th 2012 a newer, bigger rover, Curiosity, landed at the foot of Aeolis Mons, thousands of kilometres away. Opportunity looked after itself for nine days to allow the scientists and engineers to make a fuss of the newcomer, then set out to study the intriguing smectite clays that a European orbiter had detected on Cape York, a peak further along Endeavour’s rim.
As the unexpected years went by, Opportunity continued along the hilly rim of Endeavour until it came to Perseverance Valley, which cuts through towards the crater floor. It was heading down the valley when, on June 10th 2018 — Sol 5,111, well over seven Martian years of service — another dust storm cut it off from Sun and Earth. When, after months, the global storm subsided, the rover’s minders, now family, waited for its solar panels to be blown clean. It appears they were not. After over 1,000 messages attempting to restore contact, Opportunity was declared lost on February 12th.
If more than a handful of people ever get to explore Mars in person, surely one day someone will follow its tracks down Perseverance, looking for the mast on which its cameras are mounted — separated for stereoscopy, easily anthropomorphised — to honour a pioneer who travelled far and provided insight after insight into the history of Mars. Until then, imagine her as she was photographed by the orbiting HiRise camera after first reaching the scalloped rim of Victoria, looking down onto its rolling dunes: a tiny speck perched on a promontory peak, a new planet swimming before her eagle eyes, watched in silence from the skies.
-- This article appeared in the Obituary section of the print edition of The Economist, February 21, 2019, p.82, under the headline "Remembering a robot".
13. Hubble & Gaia Weigh the Milky Way
The mass of the Milky Way is one of the most fundamental measurements astronomers can make about our galactic home. However, despite decades of intense effort, even the best available estimates of the Milky Way’s mass disagree wildly. Now, by combining new data from the European Space Agency (ESA) Gaia mission with observations made with the NASA/ESA Hubble Space Telescope (HST), astronomers have found that the Milky Way weighs in at about 1.5 trillion solar masses within a radius of 129 000 light-years from the galactic centre.
Previous estimates of the mass of the Milky Way ranged from 500 billion to 3 trillion times the mass of the Sun. This huge uncertainty arose primarily from the different methods used for measuring the distribution of dark matter — which makes up about 90% of the mass of the galaxy.
To weigh the Milky Way the team measured the velocities of globular clusters — dense star clusters that orbit the spiral disc of the galaxy at great distances. The more massive a galaxy, the faster its clusters move under the pull of its gravity. Most previous measurements have used the speed at which a cluster is approaching or receding from Earth, the velocity along our line of sight. Measurements from the HST and Gaia allowed the sideways movement of the clusters to be also determined, giving their space motion in 3D. From that the galactic mass could be calculated.
The group used Gaia’s second data release as a basis for their study. Gaia was designed to create a precise three-dimensional map of astronomical objects throughout the Milky Way and to track their motions. Its second data release includes measurements of globular clusters as far as 65 000 light-years from Earth.
The team combined this data with Hubble’s unparalleled sensitivity and observational legacy. Observations from Hubble allowed faint and distant globular clusters, as far as 130 000 light-years from Earth, to be added to the study. As Hubble has been observing some of these objects for a decade, it was possible to accurately track the velocities of these clusters as well.
By combining Gaia’s measurements of 34 globular clusters with measurements of 12 more distant clusters from Hubble the team was able to compute the Milky Way’s mass in a way that would be impossible without the two space telescopes.
Until now, not knowing the precise mass of the Milky Way has presented a problem for attempts to answer a lot of cosmological questions. The dark matter content of a galaxy and its distribution are intrinsically linked to the formation and growth of structures in the Universe. Accurately determining the mass for the Milky Way gives us a clearer understanding of where our galaxy sits in a cosmological context.
See the original item at https://www.spacetelescope.org/news/heic1905/
-- Abridged from the above item forwarded by Karen Pollard.
14. Quotes
“For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.” -- Richard Feynman.
“To do real good physics work, you do need absolute solid lengths of time … it needs a lot of concentration … if you have a job administrating anything, you don’t have the time. So I have invented another myth for myself: that I’m irresponsible. I’m actively irresponsible. I tell everyone I don’t do anything. If anyone asks me to be on a committee …‘no’ I tell them: I’m irresponsible.”
-- Richard Feynman, who explained his method in a 1981 television interview. Quoted in
https://www.chronicle.com/interactives/is-email-making-professors-stupid
Alan Gilmore Phone: 03 680 6817
P.O. Box 57 alan.gilmore@canterbury.ac.nz
Lake Tekapo 7945
New Zealand
Comments