In this episode we find out about observations of regions of massive star formation from Dr Steve Longmore, hear about a chance to vote on what the Hubble Space Telescope will observe next, we get the latest news and find out what to see in the night sky during February.
In the news this month:
- There is a great variety in the masses of stars we see in our galaxy. Some are as massive as 120 times the mass of our own Sun but the question of how such massive stars form has puzzled astronomers for many years. As a gas cloud collapses, a proto-star forms in the centre. Current models suggest that stars more than 20 times the mass of the Sun create so much radiation pressure on the surrounding gas cloud that it overcomes the gravity of the star, blowing away the gas and halting the growth of the star. Computer simulations of stars forming in two dimensions suggest that the strong radiation completely stops the accretion process when a star reaches about 40 solar masses; well below the mass of the most massive stars observed. New research shows that these stars can form despite the strong radiation. A team at UCSC has carried out sophisticated simulations in three dimensions which show that massive star formation is possible and naturally leads to the formation of binary or multiple star systems. You can read about their research in their paper (PDF).
- More than 95% of the Martian atmosphere is composed of carbon dioxide with smaller amounts of nitrogen, carbon monoxide, water vapour, oxygen and argon. A group of researchers at NASA's GSFC used the IRTF and Keck telescopes to take spectra of Mars over a seven year period. They found concentrations of methane over certain parts of the Martian surface that varies with the seasons. Methane is destroyed by sunlight so the presense of this gas indicates that there is ongoing production. The mechanism for methane production on Mars is not yet known although suggestions include various geological and biological mechanisms.
- The Moon always shows the same face to us on Earth as it is synchronously locked; it rotates once on its axis in the time it takes to orbit the Earth. Researchers at the Institut de Physique du Globe de Paris have presented evidence that suggests that the Moon could have once faced the other way. The evidence comes from a study (PDF) of the ages of impact craters on the lunar surface.
- The International Year of Astronomy got off to a good start with a launch event at the UNESCO HQ in Paris on 15th January. 2009 celebrates 400 years since Galileo first turned a telescope to the sky and observed the Moon, and the planets. In West Sussex in England the start of the year of celebration was marked by recognition of the little known English astronomer Thomas Harriot. Harriot was a contemporary of Galileo and, according to papers at the West Sussex record office, he used a telescope to observe and map the Moon before Galileo. You can listen to Allan Chapman talking about the observations on the 365 Days of Astronomy podcast for January 14 2009.
The Smithsonian Astrophysical Observatory's Submillimeter Array (SMA) is an 8-element radio interferometer located atop Mauna Kea in Hawaii and is above most of the water vapour in the atmosphere. The array observes at wavelengths 600-1000 times longer than the light we see with our eyes. This lets us see light from very cold gas and dust in the universe.
Steve Longmore has been using the SMA to observe regions in space where massive stars are forming. Massive stars dominate the light output of galaxies that are forming stars but as they are so rare and short-lived they are difficult to find and study. They are formed in very massive, cold, dense, molecular clouds composed mostly of molecular hydrogen. Given the conditions of these giant molecular clouds, Steve is trying to work out how many stars of different mass will come out.
Hubble - You Decide
- NGC 6634 - star forming region;
- NGC 6072 - a planetary nebula;
- NGC 40 - a planetary nebula;
- NGC 5172 - spiral galaxy;
- NGC 4289 - edge-on spiral galaxy;
- Arp 274 - interacting Galaxies.
The close for votes is March 1st with the image released during the 100 Hours of Astronomy global event (April 2-5). Get voting.
The Night Sky
Ian Morison tells us what we can see in the night sky during February 2009.
High in the south is the constellation of Orion the Hunter with a line of three stars making up his belt. The upper left hand star of Orion is Betelgeuse - a red supergiant - and at the lower right is Rigel a blue supergiant. Towards the east of Orion is a fairly blank patch of sky. The first constellation is Monoceros which doesn't really have much visible by the unaided eye. However it does contain the Rosette nebula and is probably the location of the nearest stellar mass black hole. Further east and north you will see Procyon in Canis Minor and beyond that is Cancer. Although Cancer doesn't contain much to see by eye, binoculars show the very nice Beehive Cluster (M44). Continuing on we come to Leo.
Venus cannot be missed at magnitude -4.5 after sunset. Saturn is lying below the main stars of Leo. All of the other classical planets have been sneaking around behind the Sun and are just about becoming visible before dawn.
- Mars, Jupiter and Mercury are coming into the pre-dawn sky. On February 22nd it might be worth trying to have a look for them as they will be joined by the Moon. Although they will be an appreciable angle from the Sun, they will be very low in the east as seen from the UK so you will need a very clear horizon to see them. Make sure that you are very careful not to look at the Sun once it starts to rise.
- Around February 22rd-24th Comet Lulin will be two degrees below Saturn. It is about magnitude 7 so this should be possible to see with binoculars from a dark site.
- Near the end of the month dwarf planet Ceres is moving upwards behind the hind quarters of Leo. It will be around magnitude 6.9 to 7.2 so you will therefore need binoculars. Observe it over a few nights and see it move.
Over Christmas Ian was in New Zealand and got to see a wonderful part of the southern sky containing Vela and Carina down to Crux - the southern Cross - and Centaurus. One of the brightest stars in that region is Alpha Centauri. Alpha Centauri is actually a triple system, one of which is Proxima Centauri - the nearest star to the Sun. Up to the left of Alpha Centauri you'll see Beta Centauri. Alpha Centauri is just over 4 light years away but Beta Centauri is over 100 times further away so it must be inherently very bright. Alpha and Beta Cenaturi are the pointers that can be used to find Crux - the Southern Cross. Just to its lower left is a prominent dark region named The Coalsack. It's a dense region of dust and gas about 2000 light years from us. As you move up along the Milky Way - towards Carina - is the False Cross. Up to the right of the right-hand star of the False Cross is a fuzzy region called C96 (NGC 2516). Below the False Cross towards Crux is the Carina Nebula. It's a fantastic region to observe in detail and contains a star - Eta Carina - which is probably the next star that will explode as a supernova near the Earth.
Ian recommends a couple of books for observing in the southern hemisphere:
- How to Gaze at the Southern Stars by Richard Hall (review at New Scientist)
- 2009 New Zealand Astronomical Yearbook
For more information about the night sky check out Ian's Night Sky pages for February 2009.
Odds and ends
Members of the Jodcast will be at the Jodrell Bank Centre for Astrophysics stand at AstroFest 2009 on February 6-7 so, if you're there, drop by and say hello.
|Interview:||Dr Steven Longmore and Stuart Lowe|
|Night sky this month:||Ian Morison|
|Presenters:||Roy Smits and Stuart Lowe|
|Intro script:||David Ault|
|Intro editor:||Fiona Thraille|
|Segment voice:||Danny Wong-McSweeney|
|Cover art:||Star trails seen over the Submillimeter Array. Credit: Nimesh Patel|