I’m participating in the action against pending U.S. anti-piracy legislation - SOPA (The Stop Online Piracy Act) and PIPA (The Protect IP Act). I’ve “darkened” my most popular viewed images on flickr: http://www.flickr.com/photos/starrydude/3483623481/

SDSS Galaxy Survey

Key to modern extragalactic surveys is to measure the redshift of the object, via spectral means.  By redshift we mean the increase in the wavelength of the electromagnetic radiation (i.e. the light) received by a detector compared with the wavelength emitted by the source, e.g. if the source is moving away from us then the wave will be stretched, if coming towards us it will be compressed. Any increase in wavelength is called “redshift”, even if it occurs in electromagnetic radiation of non-optical wavelengths, such as gamma-rays.

Redshifts surveys in the 1980s and the 1990s (e.g., the CfA, IRAS, and Las campanas surveys) measured thousands to tens of thousands galaxy redshifts. Multifibre technology now allows us to measure redshifts of millions of galaxies. One of these such surveys uses data obtained with the Sloan Digital Sky Survey (SDSS). The SDSS is a U.S.-Japan-Germany joint project to image a quarter of the Celestial Sphere at high Galactic latitude as well as to obtain spectra of galaxies and quasars from the imaging data. The dedicated 2.5 meter telescope at Apache Point Observatory. Recently they have released the most detailed survey ever completed (with the release of DR7) - anyone can navigate around the Universe with their navigation tool - so go and give it a go! Oh and here is what the Universe looks like from the SDSS….

The SDSS has made detailed 3D maps of relatively nearby galaxies. The Earth is at the centre of these wedges, and each point represents a galaxy, with the outer circle at a distance of 2 billion light years. The region between the wedges was not mapped by the SDSS because dust in our own galaxy obscures the view of the distant universe in these directions (Illustration: M Blanton/ SDSS)

Hubble Detects Unusual Object

Astronomers working on the Supernova Cosmology Project have recently discovered an object that they can not explain:

Not there to begin with (left)…. appears later (right) Image Credit: K. Barbary et al.

This is an image taken with the Hubble Space Telescope of a galaxy cluster in Bootes.  The cluster is named: CL 1432.5+3332.8, not the most imaginative but believe me there are lots of cluster to name! The cluster is at a redshift of 1.112 (which is just another way of stating the distance to it) and this means that it would have taken the light some 8.2 billion years to travel to the HST camera. Now that’s pretty cool. The really odd thing is over about 100 days the transient source brightened (for those of you who care, to about a peak of 21 in the i and z bands) and then declined over a similar time-scale. Now the first thing I thought of when I saw this was supernova. Though it turns out that the lightcurve (the shape of it brightening and becoming more faint) looks nothing like any known supernova. It is also inconsistent with another type of event - microlensing, where one star acts as a gravitational lens on a background star.

So the question is, what the heck is it? The object is not found in any other databases and details about it during its observation are minimal. Very interesting and its good to know we are still unsure about everything we observe.

If you fancy reading more then you can find their discovery paper on astro-ph.