Hubble Captures 2 Galaxies Overlapping to Form a Stunning Interstellar 'Snail'


Why astronomers must be so careful about distance in space is beautifully illustrated in a new image from the Hubble Space Telescope. Two galaxies, more than one billion light-years apart, linger in the shadows with stunning golden spirals that appear to be on the verge of collision. Despite appearances, SDSS J115331 and LEDA 2073461 aren't at all communicating with one another.

Instead, there is a significant gap between them. The serendipity of their alignment in the line of sight is breathtaking. As they are drawn together by dark matter superhighways to galaxy cluster nodes, galaxies do clash in space very regularly. From there, they stream toward a shared galactic centre.

When galaxies merge, their central black holes do as well, and this is thought to be one way the supermassive black holes at their centres grow to masses billions of times that of the Sun.

However, because space is vast and filled with numerous objects, astronomers must exercise caution when evaluating two objects that appear to be in the same location. Are they overlapping with a great gap between them or are they interacting?

One of the most crucial tools we have for understanding the universe around us is distance. Without a precise distance measurement, it is impossible to determine an object's size, mass, or brightness. However, it might be challenging to estimate distances in space. Unless you know how much light anything emits, you can't tell how far away something is just by looking at it.

Because of their known intrinsic brightness, objects like Type Ia supernovae serve as a valuable tool for measuring distance in space. We can use parallax—the way objects move across the sky in relation to one another—for relatively close objects.

Individual things, however, becoming increasingly more difficult to perceive once you get further away from them. Therefore, scientists rely on other methods, such as how the Universe's expansion spreads out light from far-off objects.

Although there are other signs as well, this is how we know SDSS J115331 and LEDA 2073461 are not now involved in a massive collision: Because of how well-organized the two galaxies are, a collision would ruin them.

Distances can be tricky to estimate, even near the Milky Way. Recently, researchers discovered that a gamma radiation source was farther away than previously believed. In that instance, scientists were able to draw the connection since the radiation and its source shared a similar form and alignment.

Scientists can utilise overlapping galaxies to study spiral galaxies even though they may not be able to use them to understand galactic collisions and mergers.

The interstellar dust in a foreground galaxy may be easier to see when backlit by a more distant galaxy. This odd alignment has been exploited by researchers to trace the distribution of interstellar dust across several galaxies.

It's unclear if this will include using Hubble's image of SDSS J115331 and LEDA 2073461. However, it is really beautiful to look at.

The Hubble website offers wallpaper-sized versions of this image.

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