In the show this time, we talk to Prof. Jon Butterworth about particle physics(!), Indy rounds up the latest news and we find out what we can see in the June night sky from Ian Morison and John Field.
This month in the news: a galaxy up in arms.
When the noted philosopher and occasional astronomer Immanuel Kant observed galaxies in the 18th century, he thought they looked like "Island Universes". Fast forward two hundred and fifty years or so, and we know that while poetic, that name is quite far from the truth. Astronomers in the 1920s debated whether galaxies and nebulae were part of our own milky way or not. Edwin Hubble conclusively put the matter to rest by measuring the distance to Cepheid variable stars in spiral nebulae. Galaxies are - to paraphrase - far, far, away. Hubble also came up with a classification system for galaxies that we still use today, with the two main categories being spiral and elliptical galaxies. We now estimate that there are roughly two hundred billion galaxies in the observable universe, which can presumably all be sorted using this system.
One of the most studied galaxies, by virtue of its proximity, is the Andromeda Galaxy. Andromeda, also known as Messier 31, is the closest spiral galaxy to the Milky Way, and is the largest galaxy in the so-called "local group" of galaxies. It is in fact moving towards the Milky Way, and the two galaxies are expected to collide in roughly 4 billion years. Before that happens, though, scientists have been very interested in studying Andromeda to shed more light on the formation process and evolution of spiral galaxies. Andromeda's spiral arms are of particular interest: some images of the galaxy appear to show it having concentric rings, rather than spiral arms. Astronomers have suspected that the clue to Andromeda's shape might lie in the way it has interacted with surrounding satellite galaxies over time. In 2006, a team from South Africa performed a simulation of a collision between Andromeda and the dwarf galaxy M32, assuming that M32 passed through the larger galaxy, very close to its center. They found that the gravitation effect of this interaction was to give Andromeda concentric rings, similar to the shape it has today.
However, a trajectory sending M32 very close to the center of Andromeda is unlikely, according to astronomers at Harvard and the University of Maryland. This is for two reasons: firstly, there is simply less chance of M32 passing close to the center, simply because it's a very small region. Secondly, dwarf galaxies moving towards the centre of a bigger galaxy have a good chance of getting nudged off course by other satellite galaxies. They have run a new simulation where M32 crosses the edge of Andromeda's disk, and their findings were recently posted on arXiv. Simulating Andromeda and its companion over a period of 2 billion years, a sped-up film shows M32 shooting through the disk and generating ripples which turn into spiral arms - the effect is not unlike throwing a stone into a pond. In contrast to the previous simulation, this study finds that spiral arms are generated by the collision - although these arms would look a lot like concentric circles when viewed almost edge-on, which is what the astronomers suggest is going on here. This result provides insight into Andromeda's history, and definitely suggests that a collision is responsible for the spiral arms.
It also provides information about the companion dwarf galaxy M32. The currently accepted theories about dwarf galaxies say that they are so compact because their larger companion strips them of outer layers of gas, stars and dark matter. The simulation suggests otherwise, though: the intense gravitational encounter with Andromeda would not have been enough to remove the quantities of matter consistent with observations today. This means that the dwarf galaxy must have started off compact, implying that it (and others) are formed by different processes than astronomers thought.
In other news, the universe is a little bit less habitable than we thought:
A type of star favoured for exoplanet searches, known as M-dwarfs (they are a type of red dwarf star), might turn out to be very inhospitable for life. M-dwarfs are quite common, relatively small and cool stars, meaning that a planet in the theoretical 'habitable zone' where liquid water can be found would be closer in to its star, and orbit in less time - this would give astronomers more chances to study it. However, the proximity of the habitable zone also means that the effect of the solar wind coming from the M-dwarf is stronger, thus reducing the chances that exoplanets would be able to hold on to their atmosphere. Astronomers have found that the solar wind experienced by such planets could be 10 to 10,000 times stronger than the wind encountered by earth. While this diminishes the chances of life, it has been noted that planets with a strong enough magnetic field may be able to hold on to their atmosphere. The search, then, is still on...
Interview with Prof. Jon Butterworth
In a somewhat atypical interview, we talk to Prof. Jon Butterworth, the head of the physics and astronomy department at UCL and blogger for the Guardian, about his about his work in... particle physics! Heavily involved in the search for the Higgs Boson using the ATLAS detector at the Large Hadron Collider, Jon tries to explain particle physics to Indy and Mark (not an easy task!), talks about the overlap between particle physics and astronomy and shows us things for a particle physicist's point of view.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere night sky during June 2014.
Leo is setting in the west as it gets dark, while in the south is Boötes, with its bright star Arcturus. Rising in the east is the Summer Triangle, consisting of the stars Vega in Lyra, Deneb in Cygnus and Altair in Aquila. A third of the way from Altair towards Vega is the asterism of Brocchi's Cluster, or the Coathanger, in front of the Cygnus Rift. Delphinus the Dolphin lies below it. Ursa Major is high in the north-west and contains the famous asterism of the Plough, with the stars Merak and Dubhe pointing towards Polaris, the North Star. In the middle of the Plough's handle is a double star, known as Mizar and Alcor, and Mizar itself can be seen to be a double star through a telescope.
- Jupiter sets nearly three hours after sunset at the beginning of June. It fades from magnitude -1.9 to -1.8 during the month, and shrinks from 33 to 32" in angular diameter. By month's end, it is low down at sunset and lies almost on the line between the stars Castor and Pollux. The Galilean moons are still visible using a small telescope, but surface details on the planet are harder to spot due to atmospheric scintillation.
- Saturn lies in Libra, between the stars Spica and Antares. It dims from magnitude +0.2 to +0.4 during the month and is about 18" across. It is moving retrograde (westward) across the sky towards the double star Alpha Librae, lying 2.5° away from it at the end of June. Saturn's rings are about 40" across and are inclined at 21° to the line of sight, making the major divisions between the rings visible to small telescopes, but viewing is slightly hampered by the planet's low elevation.
- Mercury can be observed low in the west-north-west shortly after sunset at the beginning of the month, but it fades from magnitude +1.2 to +3.4 by the 11th and is lost in inferior conjunction (between the Earth and the Sun) by the 19th.
- Mars Is receding rapidly, dimming from -0.5 to 0 in magnitude and shrinking from 11.8 to 9.5" in angular size during June. It starts the month 2.5° from the star Porrima and ends it 3.5° from Spica, moving through the constellation of Virgo. Mars is at its highest at sunset, giving the last chance of the current apparition to observe features on its surface.
- Venus starts the month shining at magnitude -3.9, moving quickly through the lower part of Aries. It then enters Taurus and passes between the Hyades and Pleiades star clusters on the 28th, ending the month 3.5° from the star Aldebaran. The planet is low on the eastern horizon just before dawn, showing a gibbous phase and decreasing from 14 to 12" in size during June. Over the same period, its fractional illumination increases from 77 to 85%, keeping its brightness almost constant.
- Saturn is well placed for observation this month. It is at its height soon after dark. To find it, follow the Plough's handle down past red Arcturus to white Spica. Saturn is the yellowish object to Spica's lower left. A magnitude 8.2, Titan - Saturn's largest moon - can be seen. A larger telescope shows the distinction between the planet's A, B and C rings.
- This month is a good time to observe the globular cluster M13 in Hercules and the 'double double' star in Lyra. Hercules is between the bright stars Arcturus and Vega, and its four brightest stars make a trapezium called the Keystone. M13 is two-thirds of the way up its right-hand side, and is the brightest globular cluster in the northern hemisphere sky. The double double, Epsilon Lyrae, is to the left of Vega, showing two stars in binoculars but four when viewed through a telescope.
- Noctilucent clouds may be spotted towards the end of June. They are the highest clouds in the atmosphere at around 80 kilometres above the Earth, and can be seen towards the north during late twilight. Normally too faint to see, sunlight shining from below the northern horizon can render them visible around midsummer, just when the lower part of the atmosphere goes into shadow. Noctilucent clouds seem to be getting bigger, brighter and more common, but their cause is unclear.
- Jupiter can be seen lying just below the star Pollux an hour after sunset from the 2nd to the 4th, low in the west-north-west. Mercury may also be visible, very low beneath Pollux's twin star, Castor.
- Mars is 3° above and slightly left of a waxing gibbous Moon an hour after sunset on the 7th.
- Saturn is about 2° up and to the right of a waxing gibbous Moon after sunset on the 10th, low in the east-south-east.
- Venus is 2.5° to the left of a thin crescent Moon before dawn on the 24th, sitting between the Hyades and Pleiades Clusters.
John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during June 2014.
Jupiter is visible in the west after sunset for the first half of the month, before disappearing into the twilight. Sirius, the brightest night-time star, is can be seen in the same part of the sky in the evening, and again in the south-east before dawn. The zodiacal constellations of Scorpius and Sagittarius dominate the south-eastern sky in the evening, the red star Antares - meaning 'Rival of Mars' - marking the Scorpion's heart. To Māori and some Polynesian cultures, Scorpius is a fishing hook and Antares is the eye of the hook, stained with the blood of the mythical hero Maui. Binoculars or a telescope show many star clusters and nebulae in this region of the sky. The globular clusters M4 and NGC 6144 appear close to Antares, while a number of double stars can be seen along the body of the Scorpion with the unaided eye. The open cluster NGC 6231 is near the Scorpion's stinger, as is M7, and both can be seen as hazy glows with the naked eye under a dark sky. M6, the Butterfly Cluster, is not far away, a telescope revealing an elongated cluster of stars forming its wings. The constellation of Sagittarius the Archer is also rich in objects. Its brightest stars are known as the Teapot, near the top of which is the bright globular cluster M22.
Two of the most spectacular night sky sights are M8, the Lagoon Nebula, and M20, the Trifid Nebula. M8 is a compact cluster surrounded by a halo of nebulosity containing a dark rift, and is dominated on its western side by two sixth-magnitude stars. M20 is nebulous, with the dark lanes that split it into three sections discernible using a telescope of 200 millimetres or more in aperture. Its pink and blue colours can be seen in long-exposure photographs. It is also worth finding M23, an open cluster containing arcs and chains of stars, M24, a bright cloud of stars interspersed with dark nebulae, M25, an open cluster hosting several deep yellow stars, and M55, an open cluster of magnitude 7.4.
The Milky Way is at its brightest, widest and deepest around Scorpius and Sagittarius. It is Al Nahr (the River) to Arabs, the River of Heaven to Chinese and Te Ikaroa (the Long Fish) to Māori. The centre of the Milky Way galaxy is in the direction of Sagittarius, and its dark lanes are dust and gas that may one day form new stars. A scan along it, towards Crux and Carina in the west, reveals more star clusters and glowing clouds of gas. The Magellanic Clouds can be seen low in the south on a moonless night, and are small galaxies not far outside our own.
The planet Saturn is towards the north in the evening, in front of the stars of Libra, and Mars can be seen in a nearby part of the sky. Saturn is fading and shrinking as it recedes from us, but a small telescope can still pick out the disc of the planet, as well as its rings and its largest moon, Titan. Venus rises around 05:00 NZST (New Zealand Standard Time, 12 hours ahead of Universal Time) at the beginning of the month and around 06:00 by the end, appearing as a brilliant morning star. Venus is directly above Matariki (the Pleiades star cluster) in mid-June. The heliacal (dawn) rising of Matariki and Puanga (the star Rigel) on the 21st marks the winter solstice, when the Sun rises and sets at its most northerly points, and is the start of the new year for Māori in Aotearoa (New Zealand).
Odds and Ends
Citizen scientists are trying to revive a long-inactive space probe in a crowdfunded project called the ISEE-3 reboot. A team of volunteers from various backgrounds have made contact with a probe launched by NASA in the seventies known as ISEE-3 (International Sun/Earth Explorer) as it passed realtively close to earth. The team aims to wake the probe up and execute one last burn to put it in position where it can do science once more.
Three new astronauts arrived on the ISS recently as part of Expedition 40, "Blue Dot". Part of the trio was ESA astronaut Alexander Gerst, a German geologist by training who will spend 6 months on board the station. Part of his tasks will involve undergoing a battery of medical tests to better understand how the human body adapts to space conditions.
Statistics taught everyone a lesson in late May, when a suspected gamma-ray burst detected by the Swift satellite turned out to be nothing at all. An automatic alert on Swift, apparently triggered by the random arrival of an unusually high quantity of X-rays, led to the release of a preliminary analysis by astronomers that was hampered by a power cut here on Earth. Although it was announced as an X-ray source, and as no more than a rough guide to alert other astronomers to a potentially interesting transient event, a burst of online interest blew the release up into a big story - rather like the event itself.
|Interview:||Prof Jon Butterworth with Indy Leclercq and Mark Purver|
|Night sky:||Ian Morison and John Field|
|Presenters:||Indy Leclercq, Mark Purver and Chris Wallis|
|Editors:||Indy Leclercq, Sally Cooper and Mark Purver|
|Segment Voice:||Iain McDonald|
|Website:||Indy Leclercq and Stuart Lowe|
|Cover art:||The inside of the ATLAS detector at CERN, with an artists' impression of a black hole superimposed CREDIT: ATLAS Experiment © 2014 CERN|