Australian Sky & Telescope March - April 2022

IN A COUNTRY SUCH AS AUSTRALIA that spans so far from north to south, it’s sometimes easy to forget that astronomical objects that can be seen at one latitude cannot be seen at others. I was reminded of this recently when I was reminiscing about living on the NSW north coast in my youth, and being able to just make out the Andromeda Galaxy with binoculars, low on the northern horizon. I can’t easily do that now from Sydney, as the giant galaxy culminates at only about 14° altitude. There are too many buildings, hills and trees in the way, not to mention the light pollution. And for those in our more southerly cities it’s either extremely hard or essentially impossible. But the difficulty of seeing a northerly astronomical object…

ASTRONOMERS HAVE precisely mapped out 12 stellar streams in and around the Milky Way. These ribbon-like structures of stars moving in a coherent fashion are the remains of satellite galaxies or globular clusters ripped apart by our galaxy’s tidal forces. Tracking their 3D positions and motions will eventually help to chart the distribution of dark matter in the Milky Way. Stellar streams were discovered in the 1970s, but the number of known systems has increased spectacularly over the past years, thanks to programs such as the Pan-STARRS 1 Survey on Haleakala, Hawai‘i, and the Dark Energy Survey in the Chilean Andes. At present, astronomers know of almost 70 streams. A team led by Ting Li (University of Toronto) used a fibre-optics spectrograph on the 3.9-metre Anglo-Australian Telescope in NSW to…

The Moon has orbited Earth for billions of years, but quasi-satellites travel in phase with our planet around the Sun for only a few hundred years. Now the first detailed observations of the quasi-satellite 469219 Kamo‘oalewa suggest that it (and perhaps others) might actually come from the Moon itself. Discovered in 2016, Kamo‘oalewa is both the closest and smallest known quasi-satellite and comes within range of large telescopes every year. Benjamin Sharkey (University of Arizona) and colleagues have observed it over the past five years using the Large Binocular Telescope and the Lowell Discovery Telescope, and reported their results in the journal Nature Communications Earth & Environment. Data collected at visible and infrared wavelengths showed that Kamoʻoalewa reflects more light at longer wavelengths (1.5 to 2.5 microns), making it more…

PLANETS ABOUND in the Milky Way. They probably do in other galaxies, too, but the usual techniques can’t reach far enough to tell. Using an innovative method, Rosanne Di Stefano (Center for Astrophysics, Harvard & Smithsonian) and colleagues announced a possible extragalactic exoplanet in the journal Nature Astronomy. In X-ray binaries, a black hole or neutron star siphons material off a companion star. Infalling material heats up until it emits X-rays. This hot inner region is small enough that a planet passing in front of it could block most or all of the radiation. Di Stefano and collaborators set out looking for such a signal, examining observations of 238 X-ray binaries in three nearby spiral galaxies: M51, M101 and M104 (the Whirlpool, Pinwheel, and Sombrero galaxies). The hunt struck gold…

The Tamworth Regional Astronomy Club Inc. offers you are a rare opportunity for an astronomy experience like no other. Visit observatories and be guided by experts as you link into the amazing world of citizen science in astronomy — comets, variable stars, hands-on astrophoto stacking and processing. Limited to 20 people. Register your interest early. 5 days in October 2022 $2,200 per person Register your interest: tamworthastronomy.com.au Contact: tracthestars@gmail.com 0437 834 944 0427 668 802…

When interstellar object 1I/‘Oumuamua was first spotted tumbling through the Solar System, we’d never seen anything like it. Among many unexplained oddities was its shape: With an aspect ratio of 6:6:1, it was basically an otherworldly pancake. But at the US Division for Planetary Sciences meeting in October, Ari Heinze (now at University of Washington) reported preliminary results for an asteroid, 2016 AK193 , that behaves remarkably like ‘Oumuamua: It tumbles like the interstellar object did, and it seems to be just as elongated. Unlike ‘Oumuamua, though, this asteroid is not a new arrival; it has probably been going around the Sun for billions of years. Follow-up observations will take some patience, since 2016 AK193 won’t come close enough to observe again until 2029, Heinze says. Still, the asteroid’s mere…