Galactic Punctuation and Collisions

VV340 (also known as Arp 340 or UGC 9618) is a pair of interacting gas rich spiral galaxies in the Bootes constellation. Located ~450 million light years from Earth.

It is classified as Luminous Infrared Galaxy (LIRG). LIRGs produce high amounts of IR radiation and can emit from tens to hundreds times more energy than typical galaxies. Actively growing supermassive black holes (AGN) or an intense period of star formation are normally attributed to be the cause of this energy production.

Spitzer data shows that the majority of the IR emissions is coming from the edge on galaxy (VV340 North), and coupled with data from Chandra there is strong evidence for a growing supermassive black hole (SMBH) at its centre obscured by the rest of the galaxy - however only a small proportion of the IR radiation is emitted from SMBH region. However in the UV and short wavelength optical emissions from GALEX and Hubble observations, show that VV340 South to be the brighter suggesting that it has a much higher level of star formation.

Colliding galaxies like this are a premonition of our own Milkyway's future. As we are predicted to be on a collision course with Andromeda. But before anyone starts preaching the apocalypse it's not going to happen for another 3 to 5 billion years. So where safe! Galactic cannibalism is not rare! In fact there are 2 BHs in Andromeda's nucleus. The second BH may well be from a galactic collision.

Juno

The Space mission not the film about the pregnant girl with Michael Cera playing his usual role. Set sail last friday as part of NASA's new frontiers program, it will take about five years to get to Jupiter where it will then spend a year orbiting the gas giant.

The main objectives of Juno are to peer into Jupiter's interior to determine how it formed and to map its atmosphere below the clouds to determine its global structure and motion. Also to be probed is Jupiter's magnetosphere by directly sampling charged particles and measuring the magnetic field while observing the auroras in the UV-region. It is suspected that in the inner atmosphere the hydrogen it contains is under such high pressure it becomes a fluid known as metallic hydrogen which is thought to be the source of Jupiter's magnetic field hopefully Juno will shed some light on this.

The name for Juno is very apt as in Greek-Roman mythology Jupiter drew a vail of clouds around him self to hide his mischief and it was Jupiter's wife Juno who peered though the clouds and exposed Jupiter. Hopefully the spacecraft will live up to it's name.

Lego figures of (From left to right) the gods Jupiter and Juno as well as astronomer Galileo Galilei made of aluminium have been sent along for the ride.

Maths/Physics tattoo

Is it sad that instantaneously knew this was the Maclaurin series for sine?


Note! the if you follow the link the guy says it's a Taylor series but its a Taylor series where that starting point is zero so it's a Maclaurin series

Economical Numbers

"There are 10^11 stars in the galaxy. That used to be a huge number. But it's only a hundred billion. It's less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers."- Richard Feynman

Determining a central mass from observations of its satellites

This is based on an experiment Ben and I did in our first year at Keele. Its was a good experiment that produced some surprisingly accurate results.

Kepler's Third Law states

The plan of the experiment is to fill in each of the variables(Period P and Radius a).

First things first is you need to acquire images of the thing you wish to determine the mass of, about 10 spaced over an adequate timescale (would depend on system observed). In the case of the experiment Ben and I conducted we had 7 images of Uranus over a period of 240 days.

Next Use a program that allows you to "blink" between images (we used SAOImage) and Find the bodies which are moving in the images. This can be quite difficult as the central body is most likely moving also relative to the background, this is why it is good to have a couple of images closer together. As there will be only a small change in the background-the moon should change position in a much smaller period. Once the satellites have been identified mark their positions on each image.

Then using the imaging program find the (central) x,y co-ordinates for each body and the central mass in each image. The relative positions of the satellites from the central body. Using these values its just a case of using the Pythagorean theorem (a^2 + b^2 = c^2) to calculate the radius of the orbit in pixels. Convert the radius into Kilometers.

Going back to the relative positions and using an ATAN2 function to convert the x,y co-ordinates into a relative angle to the central mass. Then using n Pi (where n is an integer value) to adjust so an angle against time is a straight line graph - this is needed due to definition of the ATAN2 function . The gradient of such a graph is the angular frequency ω of orbit. From the angular frequency ω we can find the period P of the orbit using the relation below.

Once the period is known it is just a case of rearranging Kepler's third law for Mass M and you have the mass of the central body

New Radio Space Telescope in Orbit

The Construction of RadioAstron in Russia

The Russian Federal space agency has launched a new radio space telescope, RadioAstron, which will combine signals with ground-based telescopes to provide "incredibly high resolution - as if taken by a telescope with a dish as wide as the maximum distance between the antennas - from the Earth to the Moon".

The launch of the telescope on a Zenith-3M Rocket

It is expected to be operational in a few months, and will aim to confirm the existence of a black hole in one of our neighbouring galaxies and hopefully obtain "detailed data about pulsars, interstellar plasma and neutron stars in the Milky Way"

Click on the linked title for more info.

The Hubble Space Telescope and Beyond

In 1990 the space shuttle Discovery carried the Hubble Space Telescope (HST) into orbit and 21-years later (after many upgrades and rescue missions by Shuttle crews), it is set to provide us with awe-inspiring images and valuable data until at least 2014. Only time will tell what Hubble’s successor, the James Webb Space Telescope (JWST) due to launch in 2018, will reveal about the mysteries of the cosmos.

Hubble Space Telescope in Orbit

The HST has certainly played a major role in the world of astronomy and physics, with achievements in many different areas of these subjects. Successful missions include researching black holes at the centre of galaxies, observing the formation of planets around new stars, estimating the age of the Universe, detecting the first organic molecule in the atmosphere of a Jupiter-sized exo-planet and providing evidence for the existence of dark energy. I thought I would write a little more about the age of the Universe since this is an area of particular interest to me.

In the early 20^th century, Edwin Hubble discovered the expansion of the Universe and also a relationship between the distance d of an object and the velocity v in which it is receding; v=H₀d, where H₀ is the Hubble Constant. A value for this Hubble Constant can therefore be determined by accurately measuring the velocity and distance of an object such as a galaxy; the Hubble Constant is simply related to the age (Age=1/H₀).

The recessional velocity could be accurately measured using the red-shift of the light that it emits (the Doppler Effect on a cosmological scale), however the distance proved a little trickier to find. Certain stars, called Cephieds, pulsate and this pulsation is related to the absolute magnitude of the star which can be used to find the distance. The inaccuracy occurred due to ground-based telescopes not being able to “see” faint enough. Using the ground-based telescopes the age of the Universe was estimated at 7-20 billion years old. There is a lot of uncertainty in these results!

With the launch of HST, the Cepheids could now be observed much more accurately, free from atmospheric effects and light pollution. With this data the Hubble Constant was found to be 71 km s^-1 Mpc^-1 with a 10% uncertainty¹, which corresponds to an age of 9 to 14 billion years, which is much more accurate than previous results. With the use of other experiments this was pin-pointed to 13.7 billion years¹.

The HST has also played another important role, and that is in bringing the world of science to the general public, and seeing images from the HST is partly what first sparked my interest in science. I saw beautiful images of galaxies and nebulae and formations of interstellar gas and dust, such as the Pillars of Creation, and I immediately wanted to know what they were, where they came from and how they fit into the grander scale of the Universe.

Pillars of Creation- Image by HST

With the construction of the James Webb Space Telescope, things can only get better. The JWST will see further into the infra-red and hence will see further than Hubble (light from further objects is more red-shifted). The JWST also boasts a larger mirror, allowing it to collect more light and peer ever deeper into space. One disadvantage that I can see to JWST is that its orbit will be much further away from the Earth, it is in fact not going to orbit the earth at all, but the Sun! It orbits the Sun at the same rate as the Earth and so is stationary relative to us on Earth. Due to the immense distance astronauts will not be able repair or modify the JWST, as was possible with Hubble. The future however looks bright.

The orbits of HST and JWST

For more information on Hubble visit, www.nasa.gov/hubble

For more information on JWST visit, www.jwst.nasa.gov

1-Images and values from nasa.gov