After several years of development and anticipation, the James Webb space telescope was launched on December 25, 2021, on Ariane flight VA256, with the intent to replace the famous Hubble space telescope as NASA’s flagship space telescope.
With its spectral sensitivity ranging from the red part of the visible light portion of the electromagnetic spectrum to mid-infrared, the telescope has the ability to probe some of the oldest and most distant objects ever observed, with a sensitivity to detect cosmic sources 100 times fainter than Hubble’s detection limit.
In astronomical observations, look back time refers to the time that has passed since light originating from a far-away object left that object to arrive now on Earth, as we observe the object. Light does not travel instantaneously, with a speed of just under 300,000km every second. This means that light from an object 300,000km away would take one second to reach us here on earth, and by observing that object from earth, we would always be observing that object as it were a second before.
On cosmic scales, distances become so vast that looking at extremely far away objects can mean looking at light that left millions, or indeed billions, of years ago. Thus, the farther away we look, the farther back in time we look as well.
The James Webb space telescope will be able to look at some of the faintest objects ever observed, and thus some of the farthest objects ever observed as well. Consequently, the James Webb telescope will be looking farther back in time than any other telescope of its kind thus far.
Looking that far away, however, comes with its own set of problems. Since space itself is expanding in our expanding universe, the light leaving far away objects expands itself, over its billions of years of travel time across the universe, before reaching us here on Earth. This expansion causes the wavelength of this incoming light to stretch and expand as well, making the wavelength longer, thus shifting light towards the ‘redder’ part of the spectrum.
This is called redshift, and over long enough timescales, can result in ultraviolet and visible light being shifted to the infrared portions of the spectrum. Thus, a telescope such as the James Webb telescope, with its main spectral sensitivity lying in infrared, is better equipped to observe high redshift targets such as those farthest away from us.
Josef Borg completed a PhD in Astronomy at the Institute of Space Sciences and Astronomy, University of Malta, and is currently a researcher at the Faculty of Health Sciences at the University of Malta. He is also Malta’s representative on the European Astrobiology Network Association (EANA) council.
Sound Bites
• Space X Falcon rocket, used to send the Deep Space Climate Observatory to Lagrange Point 1, will hit the moon in March.
The observatory launched on February 11, 2015, from Cape Canaveral, Florida, the US, and the spent rocket’s upper boost stage will hit the moon on March 4. While normally such stages at the time of launch were disposed of as they hit earth’s atmosphere, this particular stage was too high to return to earth after launch and has been travelling through the earth-moon system for seven years.
https://www.space.com/spacex-falcon-9-rocket-hit-moon-march-2022
• Saturn’s moon Mimas could harbour an ocean beneath its surface.
With a number of moons in the outer solar system already known to harbour such undersurface oceans, Saturn’s smallest inner moon, Mimas, joins that list after observations of its rotation. A strange wibble observed in its rotation could be indicative of a sloshing ocean below the surface of the small moon.
https://www.space.com/saturn-death-star-moon-hidden-ocean
For more sound bites listen to Radio Mocha every Saturday at 7.30pm on Radju Malta and the following Monday at 9pm on Radju Malta 2 https://www.fb.com/RadioMochaMalta/.
DID YOU KNOW?
• Telescopes don’t come with one fixed magnification! Magnification on telescopes can be easily changed using different eyepieces and some other specific accessories. The magnification of a telescope is calculated by dividing the focal length of the telescope, which is normally fixed, with the focal length of the eyepiece. Using different eyepieces with varying focal lengths thus allows more or less magnification, as necessary.
• The James Webb space telescope is named after a previous NASA administrator! James E. Webb was NASA administrator between 1961 and 1968, and was instrumental in the Apollo missions which saw mankind’s first Moon landing in 1969.
• The James Webb space telescope will be at a distance of around 1.5 million kilometres from Earth! The telescope will be at a point called the L2 Lagrange point, some 1.5 million kilometres from Earth. For comparison, the Hubble space telescope orbits the Earth at a distance of around 550km from the earth’s surface, and the Moon is around 380,000km away from Earth, on average.