The Hubble Space Telescope is the oldest space telescope in orbit in the past twenty-eight years. Nonetheless, this mission is still hard at work revealing things about our solar system, neighboring exoplanets, and some of the remotest regions of the universe. And from time to time, it also captures a picture that happens to reveal something interesting and unexpected.
Recently, during a study by Abell 370, a galaxy cluster located about four billion light years away in the constellation Cetus Sea Monsters), Hubble managed to spot something in the foreground. Observing this collection of several hundred galaxies, the picture was photobombed by 22 asteroids whose tails formed stripes that looked like astronomical background phenomena.
The study was part of the Frontier Fields program, in which Hubble captured images of some of the earliest galaxies in the universe (aka "reliquary galaxies") to determine how they evolved over time to have. The location of this asteroid field is close to the ecliptic (the plane of our solar system) where most of the asteroids are located, which is why Hubble astronomers saw so many transitions.
In the past, Hubble has recorded many cases of asteroid trails as he made observations along a line of sight near the plane of our solar system. In this case, the Near-Earth Asteroids (NEAs), which orbit the earth at an average distance of about 260 million kilometers, have not been discovered because of their weakness. But thanks to images taken by Hubble, the scientists were able to manually identify them based on their movement.
Of the 22 asteroids, five were identified as unique objects. The image was composed of several images in visible and infrared light, which were published on 6 November 2017. The picture was created in honor of "Asteroid Day", a global annual event that takes place every year on June 30th to draw attention to asteroids and what can be done to protect the earth from potential impact.
The day coincides with the anniversary of the Tunguska event, which took place on June 30, 1918, in eastern Russia, leading to the flattening of 2,000 square kilometers (770 square miles) of forest. Although it was far less damaging than the Cretaceous-Paleogene (K-Pg) extinction event that occurred 66 million years ago and probably killed the dinosaurs, Tunguska was the most damaging asteroid event in recorded history.
In many cases The images taken by Hubble appear as white traces that look like curved stripes, an effect caused by parallax. In astronomy, parallax is an observational effect in which the apparent position of an object appears to be different due to different lines of sight. When Hubble circled the Earth and took several pictures of the galaxy, the asteroids seemed to move relative to the background stars and galaxies.
The asteroids have movement along their tracks and other contributing factors also led to their striped appearance. While the white stripes have been identified as asteroid tails, the blue stripes are distorted images of distant galaxies behind the pile. This effect is known as gravitational lensing, in which the light from distant objects is distorted and magnified by the presence of an intervening object.
In this case, the intervening object whose gravitational force magnified the light of the background galaxies was too far away for Hubble to directly see why astronomers use the technique to control the to examine the most distant objects in the universe. But while the blue stripes were expected, the white stripes caused by asteroids completely surprised!
This year, the European Space Agency (ESA), in collaboration with the European Southern Observatory (ESO), is hosting a live webcast with expert interviews, news about some of the recent asteroid research and a discussion of what killed the dinosaurs. You can watch this event tomorrow at 13:00 CEST (11:00 UST / 04: 00 PST) on the ESS Asteroid Day website.
Further Reading: ESA
Abell 370, asteroid, featured, Hubble Deep Field, Hubble Space Telescope, near Earth asteroid