Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 5
The featured image shows a distant galaxy distorted into a giant arc around the center of a galaxy cluster by gravitational
lensing.
Please see the explanation for more detailed information.

A Molten Galaxy Einstein Ring
Image Credit: ESA/Hubble & NASA, S. Jha; Processing: Jonathan Lodge

Explanation: It is difficult to hide a galaxy behind a cluster of galaxies. The closer cluster's gravity will act like a huge lens, pulling images of the distant galaxy around the sides and greatly distorting them. This is just the case observed in the featured image recently re-processed image from the Hubble Space Telescope. The cluster GAL-CLUS-022058c is composed of many galaxies and is lensing the image of a yellow-red background galaxy into arcs seen around the image center. Dubbed a molten Einstein ring for its unusual shape, four images of the same background galaxy have been identified. Typically, a foreground galaxy cluster can only create such smooth arcs if most of its mass is smoothly distributed -- and therefore not concentrated in the cluster galaxies visible. Analyzing the positions of these gravitational arcs gives astronomers a method to estimate the dark matter distribution in galaxy clusters, as well as infer when the stars in these early galaxies began to form.

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
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Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 6
The featured image shows a map of star motions in the Milky Way galaxy with red, mostly on the left, meaning stars
are moving away us. Blue, on the right, shows stars there
are mostly toward us. Please see the explanation for more detailed information.

Milky Way Motion in 3D from Gaia
Credit & License: ESA, Gaia, DPAC; Text: Ata Sarajedini (Florida Atlantic U., Astronomy Minute podcast)

Explanation: Our sky is alive with the streams of stars. The motions of 26 million Milky Way stars are evident in the featured map constructed from recent data taken by ESA's Gaia satellite. Stars colored blue are moving toward us, while red indicates away. Lines depict the motion of the stars across the sky. The large blue on the left and red areas on the map's right give the overall impression that stars in the Milky Way are rotating around the center. However, there is a region near the middle -- caused by our own Sun's motion relative to a rigidly-rotating central Galactic bar -- that seems to reverse it. Understanding details about the motion of stars is helping humanity to better understand the complex history of our Milky Way galaxy and the origin of our Sun.

Tomorrow's picture: open space

< | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.