Hubble's Latest & Greatest Finds: The Star at the End of the Universe and a Mostly Harmless Galaxy

Written by Hayley Bricker, Sciences Libraries Research Assistant

In March and April 2018, Hubble made two astonishing contributions to our spatial understanding of the universe: the furthest single star ever imaged, MACS J1149+2223 Lensed Star-1, nicknamed "Icarus", and NGC 1052-DF2, the first galaxy observed without almost any dark matter. These two discoveries continue to solidify Hubble's place in modern astronomical imaging as the top investigative tool.

The light Hubble imaged from Icarus is 9 billion years old. It is a tremendously old star, representative of much different cosmic stellar conditions than we currently live in. Imaging Icarus presents scientists with an opportunity to directly observe stellar evolution as it was 9 billion years in the past, filling in gaps of our current understanding of life in our universe.

Hubble has made grand contributions to the theory of dark matter, its latest which challenges the idea that dark matter exists at all. NGC 1052-DF2 is a small and diffuse galaxy with significantly less proportions of both stars and dark matter when compared to the Milky Way. Contrarily, this type of galaxy is rather common in the universe, according to a 2015 sky survey of the Coma cluster, where NGC 1052-DF2 is located. Scientist view its observation as both a challenge to and support of the theory of dark matter.

A Magnificent View

Icarus is special. Not only because it is a magnificent feat to image a star at such a distance, but it is equally astonishing that it was discovered via the astronomical technique of "gravitational lensing." Many of us have grown up with the basic understanding that we live in a fabric of space-time. This fabric can be severely bent and warped by an object of great mass. In the most dramatic representations of this concept, a black hole is usually the object. However, clusters of galaxies can also bend space-time. This massive interaction can act as a "lens" and reflect light along the warped curvature of space. Gravitational lensing is a powerful technique used to image very distant and large groups of objects in the universe, and on occasion, can resolve single objects such as Icarus.

Image of a gravitational lens.

[A gravitational lens, courtesy of Space.com]

 

A graphic depicting a galaxy lensing two distant objects from the Chandra X-Ray Observatory

[A graphic depicting a galaxy lensing two distant objects, courtesy of the Chandra X-Ray Observatory.]

 

Image of Icarus taken by Hubble.

[Icarus, imaged by Hubble.]

In Icarus' case, Hubble was able to capture an image of a galaxy cluster bending the light of distant stars behind it, illuminating Icarus for eager astronomers. While in the past single stars and even some planets have been observed via lensing, Icarus is astonishing because of the timing of observation. Icarus was captured in its supernova phase. It is a blue supergiant star, meaning it is expected to implode violently at the end of its life. The light of the supernova was lensed by the galaxy cluster in the foreground, allowing Icarus to stand out from its surrounding objects. Without the star going into supernova, it would not have been distinguishable. 

A Cosmic Query

Since the late 1990s, dark matter has been the prevailing mystery in the astrophysics and cosmology community. First, it was a deeply disturbing and slightly sinister presence in scientific debates, and then it became a highly exciting and accepted assumption of what the universe contains. Dark matter is the matter that is unseen yet makes up much of the mass in the universe. It was first posited by Lord Kelvin in an 1884 talk, and rigorously explored by Einstein & Hubble in the early 20th century, that most of the mass of galaxies is made up of unseen dark matter, only detectable because the spin rate of observable galaxies indicates there is more mass within than currently calculated. Presently, the accepted ratio of dark matter to normal matter in galaxies is 100:1.

Presently, galactic formation theories call for a recipe of mostly dark matter—so much, in fact, that is widely thought that galaxies cannot form without the presence of dark matter.

In March, a galaxy 65 million light years away, was observed with hardly any detectable dark matter. NGC 1052-DF2 is much smaller in mass than the Milky Way and is also much less diffuse with close to no gas or star-forming regions. Scientists from Yale University leading the investigation into NGC1052-DF2 studied the velocities of 10 stars within the galaxy to calculate an estimate of the galaxy's total mass, only to come up drastically short.

A spiral galaxy NGC 5194, commonly known as the Whirlpool Galaxy imaged by Hubble.

[Spiral galaxy NGC 5194, commonly known as the Whirlpool Galaxy imaged by Hubble.]

An elliptical galaxy, imaged by Hubble.

[Elliptical galaxy, M87 imaged by Hubble.]

Researchers studying NGC 1052-DF2 believe that there may be objects or forces that can mimic dark matter. Some researchers believe that NGC1052-DF2 is a new class of galaxy: the type of galaxy that would form if there was no dark matter associated with it at all. Most galaxies observed to have dark matter are either spiral galaxies, like the Milky Way, or large elliptical galaxies like the discovery of NGC 1052-DF2 potentially challenges the current understanding of what dark matter is, where it can be found in the universe, and most importantly, the physical laws by which galaxies are able to form.

So Long and Thanks for all the Stars: What's in Store for Hubble?

The Hubble Space Telescope was launched in 1990 and quickly gained a reputation for conducting some of the most pressing and detailed work in the history of astronomy. It has imaged galaxies, planets and nebulae, generating the most iconic images of these objects, ultimately culminating in the conceptual framework of our place in the universe by which today's society functions.

Image of Crab Nebula Core. Image of the planet Jupiter imaged by Hubble.  Image of a deep field taken by Hubble.  

[Click here to view more images captured by Hubble]

Hubble has been serviced numerous times, but the versatility of the telescope is quickly being eclipsed by bigger and grander space telescope projects launching in the 2020s, such as the James Webb Telescope (JWST). JWST boasts a mirror diameter almost three times wider than Hubble's mirror for unparalleled imaging in the longwave spectrum to the mid-infrared. To this end, JWST will be an engineering feat, as it takes a tremendous level of precision to keep an infrared telescope at a temperature that effectively reduces interference with imaging. Recently, NASA, ESA, and the Canadian Space Agency (CSA) have experienced funding and scheduling setbacks, increasing the time to JWST's launch. JWST's goals and standards, however, ride upon the legacy and accomplishments of Hubble thus far.

Hubble will most likely remain in orbit until 2040 without any assistance and could last longer. Currently, there are no servicing missions planned for Hubble, but as obstacles continue to arise for JWST, there is potential for the extension of Hubble's life. No matter the time to mission end, Hubble's atmospheric reentry will truly mark the end of astronomy's first great observational era.

Resources in the Library

If you're interested in reading more on Hubble and dark matter, check out some of UCLA's resources below:

Gates, Evalyn. Einstein's Telescope: The Hunt for Dark Matter and Dark Energy in the Universe. New York: W.W. Norton & Co., 2009. Print.

Mediavilla, Evencio., Munoz, Jose A., Garzon, Francisco., Mahoney, Terence J. Astrophysical Applications of Gravitational Lensing. Cambridge University Press, 2016. Online access.

Panek, Richard. The 4 Percent Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality. Boston: Houghton Mifflin Harcourt, 2011. Print.

Shirasaki, Masato. Probing Dark Matter and Dark Energy with Weak Gravitational Lensing Statistics. Singapore: Springer, 2016. Online access. 

Krauss, Lawrence M. The Fifth Essence: The Search for Dark Matter in the Universe. New York: Basic Books, 1989. Print.  

Heymans, Catherine. The Dark Universe. Bristol: IOP Publishing, 2017. Online access.