This month in the news: is there no place like home?
NASA's Kepler satellite is undeniably an impressive mission. Having been running continuously now since 2009, it has analysed over 150,000 stars in a 100 square degree patch of sky (for comparison the Moon covers only 0.2 square degrees) and has identified more than 3800 planetary candidates. However, if you are only interested in the news of Earth-like habitable planets then the discoveries of Kepler may appear to be infuriatingly sparse. During Kepler's five years of operation there have been no planets which precisely fit the narrow criteria of being Earth-like. This is because an Earth-like planet must orbit a Sun-like star within the habitable zone (the distance at which liquid water can exist on a planets surface) and be of a similar radius to the Earth. There have been several planets that have come close to being Earth-like, such as Kepler-20e which orbits a Sun-like star, has a radius which is 80% of the Earth but its small orbit means it has a surface temperature of several hundred celsius. There has also been Kepler-22b, which orbits another Sun-like star and is within the habitable zone but has almost twice the radius of the Earth making it unlikely to have a rocky surface.
Perhaps though the search for new Earths around Sun-like stars is too restricting. After all, every star will have a habitable zone around it and it is known that stars smaller than the Sun evolve slower, which is perhaps more conducive to the long timescales required for life to develop. Smaller stars than the Sun have other advantages over Sun-like stars when it comes to finding new Earths. For one, smaller stars are more abundant, for example within 30 light years of the Earth there are only 5 Sun-like stars but there are hundreds of small Class M red dwarf stars, this provides a far larger sample of potential planetary systems to study. Also smaller stars have habitable zone orbits that are much smaller than those of Sun-like stars, meaning that the habitable planets will require less time orbit the host star, which means the Kepler satellite can build up the picture of the orbiting planets over a much shorter span of time. However most of the planets discovered around red dwarf type stars seem to have very tiny orbits and, because the stars are so dim, follow up observations from Earth based telescopes, which are required to determine properties of exo-planets, are far more difficult if not impossible at the present time.
With all that said though the announcement last month by the Kepler team of the newly discovered planet Kepler-186f is enormously exciting. It is the first planet to be discovered that has an estimated radius that is almost exactly the same as the Earth's and is nestled snugly within the important habitable zone, therefore meaning liquid water on its surface is possible. Of course at the present time Kepler-186f is the only planet of its kind that has been found around a red dwarf star but due to the way Kepler detects planets (by measuring the slight dimming of the star when a planet passes directly in front) even one detection wildly increases the probability that there are similar planets around other red dwarf stars. Unfortunately, detections of such planets for the time being with Kepler will not tell us anything about the likelihood of life on these planets. However, discovering them will be provide a catalogue for which future, more sophisticated space telescopes such as the James Webb Telescope can study and reveal the properties of their atmospheres, which may tell us whether or not life on these distant worlds exists.
Interview with Dr Chris Hales
We talk to Dr. Chris Hales about his work on detecting weakly polarised radio sources, which hid did for his PhD. He explains the issues with detecting weak polarised sources and the work he did to improve the validity of the results. He then goes on to talk about his current work at the NRAO where they are attempting to map the magnetic field of the universe.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere night sky during May 2014.
Gemini is setting in the west as twilight ends, with Canis Minor and its bright star Procyon to its lower left. Cancer is further to the south, with the Beehive Cluster at its heart. Leo the Lion is even further round, with the star Regulus and some galaxies nearby that are visible with binoculars or a small telescope. Over to the east is Botes and the star Arcturus, with Corona Borealis beside them. Continuing to move around the sky, the four stars of the Keystone in Hercules can be found, and the globular cluster M13 is two-thirds of the way up its right-hand side. The summer constellations are rising in the north-east, with the stars Vega in Lyra and Deneb in Cygnus. To the south-east, below Botes, are Virgo and the bright star Spica, as well as Libra, Serpens Caput and the zodiacal constellation of Ophiuchus.
- Jupiter is still at 45° elevation in the west at sunset at the beginning of May, setting around 01:00 BST (British Summer Time, 1 hour ahead of Universal Time). It dims from -2.0 to -1.9 in magnitude during the month, while shrinking from 35 to 33" in angular diameter. It is only 20° above the horizon at sunset by month's end, and sets at around 23:00 BST (although you may see it for up to an hour longer if you have a very low north-western horizon). Jupiter lies in Gemini, moving from beside the fourth-magnitude star Mekbuda towards the bright stars Castor and Pollux, and passing Wasat on the way. You can see the Galilean moons with binoculars, and the Great Red Spot at certain times with a telescope, with the best chance to observe coming early in the month.
- Saturn reaches opposition (opposite the Sun in the sky) on the 10th, so it is in the sky all night. It shines at magnitude +0.1 quite low down in Libra, and its disc is 18.6" in diameter. It is moving west (retrograde) towards the star Alpha Librae. The rings are now 22° from the line of sight and about 43" across, so a small telescope can pick out Cassini's Division.
- Mars is receding from us and dims from -1.2 to -0.5 this month, while shrinking from 14.5 to 11.8" in angular size. It moves little in the sky during May because its retrograde motion ends midway through the month, and it lies close to the star Porrima in Virgo. Mars is best seen early in the month, at around 23:00 BST.
- Mercury has its best apparition of the year this month. It is low in the evening twilight as May begins, but rises higher each evening, appearing 15° above the horizon at sunset in the second half of the month. It reaches elongation (its furthest from the Sun in the sky) on the 25th, shining at magnitude +0.4 and presenting a crescent disc 8" across and 40% illuminated. It is visible for 2 hours after sunset at this point, but by the end of May it is only 5° above the horizon 1 hour after sunset, with a brightness of magnitude +1.2.
- Venus lies in Pisces and shines at magnitude -4. It is some 12° above the eastern horizon half an hour before sunrise. Its gibbous disc drops from 17 to 15" in angular size this month, but its illuminated fraction increases from 67 to 77%, keeping its brightness almost constant.
- It is a good time to observe Mars this month as it appears larger than usual in the sky.
- It is also a good time to observe Saturn this month, since it, too, appears large in the sky and is up throughout the night. It can be located by following the arc of the Plough's handle towards orange Arcturus, then continuing the curve down to white Spica, and finally looking for the slightly brighter yellow object to it's lower left - this is Saturn. As well as its ring system, binoculars or a small telescope allow you to spot its largest moon, Titan, at magnitude 8.2.
- Jupiter is coming to the end of its current apparition, but can still be easily seen this month. It is high in the sky just after sunset, allowing surface features to be seen with a telescope.
- Comet C/2012 K1 (PANSTARRS) passes below the Plough this month. With a magnitude of +7 to +8, it can be seen with binoculars. It is near the leftmost star of the Plough's handle on the 1st and 2nd, passes by Chi Ursae Majoris on the 18th and 19th and approaches Psi Ursae Majoris on the 26th and 27th.
- The Eta Aquariid meteor shower peaks before dawn on the 6th. With a low south-eastern horizon, up to 10 meteors per hour may be visible. The meteors come from dust particles release by Comet Halley when it approached the Sun 4000 years ago.
- Jupiter is near a thin crescent Moon on the 3rd and 4th.
- Mars is near a waxing Moon on the 11th. Mercury is close to a thin crescent Moon on the 30th.
John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during May 2014.
Orion the Hunter is low in the west, with three stars forming his Belt. To Māori, they form part of the Bird Snare. The blue star Rigel marks one of Orion's feet, while red Betelgeuse forms one of his shoulders. Above the Belt are the three stars of Orion's Sword, the middle member of which is actually the Orion Nebula. Slightly fuzzy to the naked eye, it is a bat-shaped cloud in binoculars or a small telescope and can be seen to be a beautiful star-forming region with a large telescope. The Belt and Sword are sometimes described as the Pot or the Saucepan by southern hemisphere observers. Following Orion is Canis Major, one of his hunting dogs, with Sirius, the brightest star in the night sky, forming its head. It is commonly known as the Dog Star, but to Māori it is Takarua, the Winter Star, and in Ancient Egypt it was called Sothis, and heralded the annual flooding of the River Nile. Procyon, the brightest start in Canis Minor, is lower down. Both Sirius and Procyon have faint white dwarf companions, but these are not easily observed. Following a line from Rigel through Betelgeuse leads to the planet Jupiter, near to Castor and Pollux, the heads of the Gemini Twins. Bands and belts on Jupiter's surface can be seen on a dark night using a telescope, while binoculars show its four largest moons.
The constellations of Scorpius and Sagittarius are rising in the east in the evening, reaching high into the sky later and showing off many beautiful objects. Crux, the Southern Cross, is high overhead after sunset, and near the star Beta Crucis is a star cluster called the Jewel Box, which appears as a hazy star to the unaided eye and as a pretty group of stars in binoculars or a telescope. Between Crux and Sirius, Carina the Keel and Vela the Sails sit along the Milky Way and contain the asterisms of the False and Diamond Crosses. They contain a wealth of bright stars, clusters and nebulae, many of which can be observed with no equipment. The Carina Nebula is the brightest of these, and appears larger than the Orion Nebula. Binoculars reveal its bright star clusters and glowing clouds of gas, intertwined with dark lanes. Within it, the star Eta Carinae is bright and orange.
The planets Mars and Saturn are in the north and east respectively after sunset. Mars is in Virgo, near the blue-white star Spica, and is now receding from the Earth and shrinking in apparent size. Lying away from the Milky Way, Many galaxies can be spotted in Virgo using a medium-sized telescope. Saturn is a yellowish object in Libra the Scales. It reaches opposition (opposite the Sun in the sky) on the 10th, and is occulted by the nearly-full Moon for observers in New Zealand and Australia at around midnight NZST (New Zealand Standard Time, 12 hours ahead of Universal Time) on the night of the 14th-15th. The event is visible to the unaided eye, but its progress will be spectacular when viewed through binoculars.
Autumn is a prime time to observe the Aurora Australis, or Southern Lights. Caused by the interaction between the solar wind and the Earth's atmosphere, the phenomenon can sometimes be seen from southerly parts of New Zealand, Australia and South America, consisting of a red glow, or even moving sheets of red and green light, on the southern horizon. With a high level of activity on the Sun so far this year, it is worth checking the several websites on which you can find current information and short-term forecasts of aurorae.
The planet Venus is in the morning sky, but rises later each day as it moves closer to the Sun from our perspective.
Odds and Ends
A group of university students from around the world have started a project called "Mars Time Capsule" which aims to send three miniature spacecraft to Mars, carrying messages, pictures and possibly video to the Red Planet as a sort of time capsule for future astronauts. More informtaion on the project can be found on their website.
Back in April, the European Southern Observatory added to its online image gallery a photo of a rock with petroglyphs of llamas photographed near the La Silla site by Hakon Dahle. This photo, reminds us that astronomers were not the first people to visit many of the mountaintops where modern observations now stand. In other llama-related news, workers at the ALMA observatory rescued a very young vicuna (the wild ancestor of the alpaca) that was separated from its herd by a pack of Chilean foxes. The fawn was eventually brought to a wildlife rehabilitation centre where it will be taken care of until it is ready for release back into the wild. More information can be found here.
A group in the University of Edinburgh has been researching the possibility of life on the moons of exoplanets - "exomoons". The study, by Duncan Forgan and Vergil Yotov, examines the various different factors that could influence the hability of exomoons. An article on the study can be read on Ars Technica here.
|Interview:||Dr Chris Hales and Chris Wallis|
|Night sky:||Ian Morison and John Field|
|Presenters:||George Bendo, Fiona Healy and Indy Leclercq|
|Editors:||Indy Leclercq and Chris Wallis|
|Segment Voice:||Iain McDonald|
|Website:||Sally Cooper and Stuart Lowe|
|Website:||Sally Cooper and Stuart Lowe|
|Cover art:||Llamas at La Silla. CREDIT: ESO/H.Dahle|