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... the star cluster Pleiades?

It can be seen from nearly every part of the inhabited globe, from as far north as the Artic Circle to the southernmost tip of South America. Click here to learn more about this star cluster.

Pleiades Cluster

PSR B1509-58

X-ray nebula & pulsar PSR B1509-58

... what pareidolia is?

Pareidolia is a psychological phenomenon involving a vague and random stimulus (often an image or sound) being perceived as significant; the imagined perception of a pattern or meaning where it does not actually exist, as in considering the Moon to have human features; the tendency to perceive a specific, often meaningful, image in a random or ambiguous visual pattern.

Pareidolia is seeing what appears to the individual to be a representation of a face, figure, or form in clouds, wood grain, marble, smoke, shadows, or any non-homogeneous area. It can also be an auditory phenomenon as in hearing white noise or a record played backward that sounds to the individual like words or a melody that isn't actually there.

For example, in the adjacent photograph, viewers may perceive the shape of a hand.

The image is actually that of the x-ray nebula surrounding a very young and powerful pulsar, known as PSR B1509-58, or B1509 for short. The pulsar is a rapidly spinning neutron star which is spewing energy out into the space around it to create complex and intriguing structures.

In this image made by NASA's Chandra X-ray Observatory, the lowest energy X-rays are coloured red, the medium range is green, and the most energetic ones are blue. Astronomers think that B1509 is about 1,700 years old and is located about 17,000 light years away in the constellation of Circinus. The nebula itself spans approximately 150 lightyears.

Credits: X-ray: NASA/CXC/CfA/P. Slane et al.

... what is a gravitational lens?

Gravitational lens: matter that through the bending of space in its gravitational field alters the direction of light passing nearby. The effect is analogous to that produced by a lens.

One of the most remarkable predictions of Einstein’s theory of general relativity is that gravity bends light. That effect was first demonstrated during a total solar eclipse in 1919, when the positions of stars near the Sun were observed to be slightly shifted from their usual positions - an effect due to the pull of the Sun’s gravity as the stars’ light passed close to the Sun.

In the 1930s Einstein predicted that a mass distribution, such as a galaxy, could act as a gravitational “lens”, not only bending light but also distorting images of objects lying beyond the gravitating mass. If some object is behind a massive galaxy, as seen from Earth, deflected light may reach Earth by more than one path. Operating like a lens that focuses light along different paths, the gravity of the galaxy may make the object appear stretched or as though the light is coming from multiple objects, rather than a single object. The object’s light may even be spread into a ring.

The first gravitational lens was discovered in 1979, when two quasars were discovered very close to each other in the sky and with similar distances and spectra. The two quasars were actually the same object whose light had been split into two paths by the gravitational influence of an intervening galaxy.

Rings or distinct multiple images of an object appear when the lens is extremely massive, and such lensing is called strong lensing. However, often the intervening lens is only strong enough to slightly stretch the background object; this is known as weak lensing. Credit: The Encyclopaedia Britannica

Read a related article about how astronomers have used gravitational lensing to discover very distant objects.

Galaxy Cluster Abell 2744

Galaxy Cluster 2744 - a gravitational lens. Credit: NASA/ESA