(ORDO NEWS) — A new image from the Hubble Space Telescope perfectly illustrates why astronomers have to be so careful about distance in space.
More than 1 billion light-years away, two galaxies float in the dark, a beautiful golden snail-like spiral seemingly caught in the act of colliding.
They are called SDSS J115331 and LEDA 2073461, and despite their appearance, they do not interact at all.
On the contrary, they are separated by a fairly large distance. Their location is an absolutely beautiful line-of-sight match.
Galaxies often collide in space, pulling together along dark matter superhighways to the nodes of galaxy clusters, where they rush towards a common galactic center.
This process is thought to be one of the ways that supermassive black holes at their centers grow to masses billions of times that of the sun: when galaxies merge, so do their central black holes.
But the cosmos is big and full of things, so scientists must be careful when interpreting two objects that appear to be in the same place. Do they interact or overlap at a great distance from each other?
Distance is one of the most important tools we have. to interpret the universe around us. The size, mass, and brightness of many objects cannot be accurately measured without an accurate distance measurement.
But distance in space can also be difficult to measure. You can’t tell how far away something is just by looking at it unless you know how much light it gives off.
That’s why things like Type Ia supernovae, which have a known intrinsic brightness, are a useful tool. to measure distance in space.
For relatively close objects, we can use parallax, which is how objects move across the sky relative to each other.
However, beyond a certain distance, individual objects become harder and harder to see. So scientists rely on other tools, such as how the expansion of the universe stretches light from distant objects.
This is how we know that SDSS J115331 and LEDA 2073461 are not at the epicenter of a giant collision, although there are other clues: the two galaxies are too neat; a collision might ruin them.
Even near the Milky Way, distance is difficult to measure. Recently, scientists discovered that the source of gamma radiation is further away than they thought. In this case, the overall shape and alignment of the radiation and its source allowed scientists to make a connection.
While overlapping galaxies may not help scientists better understand galactic collisions and mergers, they can be used to understand spiral galaxies.
With the backlight of a more distant galaxy, interstellar dust in a foreground galaxy can be more easily seen. Scientists have used this alignment quirk to map the distribution of interstellar dust in several galaxies.
It’s unclear if Hubble’s SDSS J115331 and LEDA 2073461 images will be used for this purpose. But it’s incredibly beautiful to look at.
Contact us: [email protected]