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2MASS Galaxy Survey

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The 2MASS Galaxy Reshift Survey measured the positions of 40,000 galaxies across the whole sky. The colours of the galaxies denote their distance, highlighting the clusters and networks threading through the cosmos. The most distant galaxies in the image are at a redshift of around 0.2, corresponding to a distance of around 2.7 billion light years, though the colour scale (shown below) saturates at small and large distances (for clarity). The survey works in near-infrared light, and so is able to see through more of the galactic dust than optical images. However, there is a strip across the middle where our own galaxy is still in the way.

For more information about the survey, please see Huchra et al. (2012) APJs 199 26.

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GW150914

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GW150914 was the first ever gravitational wave signal discovered, and was detected by the twin LIGO detectors in the United States. The source was the coallescence of two black holes, each around 30 times the mass of the Sun, making this the first observational evidence of a binary black hole.

The signal arrived at LIGO Livingston around 7 milliseconds before it arrived at LIGO Hanford, allowing its position to be constrained largely to the Southern Hemisphere. Although its possible locations appear to include the Large Magallenic Cloud, its distance of 1300 light years means that it originated much further away, likely in a distant galaxy.Additional information between the detectors, such as the relative phase of the gravitational waves, means that the localisation is restricted largely to one part of the sky, rather than a complete ring.

GW151226

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GW151226 was the second ever gravitational wave signal discovered at any significance, and was detected by the twin LIGO detectors in the United States. The source was the coallescence of two black holes, one of which was 5-10 times the mass of the Sun and the other roughly double that.

The signal arrived at LIGO Livingston around 1 millisecond before it arrived at LIGO Hanford, allowing its position to be constrained to two. Its distance of around 1300 light years means that it originated in a distant galaxy. Compared with the first detection (GW150914) the lower masses of these black holes, and the similarly large distance, the properties of the system are less well constrained.

LVT151012

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LVT151012 is the third most significant gravitational wave candidate signal discovered by LIGO in the first run (Sept 2015-Jan 2016). It was detected by the twin LIGO detectors in the United States, but not with enough certainty to be declared a definite detection, though the probability of it being a false alarm is 5%. If real, the source was the coallescence of two black holes of around 23 and 13 times the mass of the Sun. However, given the uncertainty, these masses are uncertain.

The signal arrived at LIGO Hanford around 1 millisecond before it arrived at LIGO Livingston, allowing its position to be constrained to two. Its distance of around 3000 light years means that it originated in a distant galaxy. Compared with the first detection (GW150914) the slightly lower masses of these black holes and the much larger distance, the properties of the system are less well constrained.