This culminated in the discovery of dark energy by two supernova survey teams. My journey to the clouds Because massive stars evolve quickly and with high complexity, they challenge our ability to model and understand the physical processes that occur within them. Phil Massey is one of the prominent astronomers who have spent their careers studying them.
I was both the local instrument scientist for the spectrograph Massey was scheduled to use and had overlapping scientific interests, so he invited me to join the project if I would collect the data.
It could collect light from more than objects at a time using optical fibers mounted to small magnetic buttons that were precisely placed on a metal plate by a high-speed robotic arm. When it worked smoothly, watching it go was pure joy. The observing run was nearly flawless, yielding hundreds of spectra of LMC red supergiants. From those and other spectra, Massey, along with astronomer Emily Levesque of the University of Washington, developed techniques to measure the temperatures of red supergiants, resulting in a revised temperature scale that resolved a previous disagreement with theoretical stellar models.
They also identified several stars with radii of about 1, times that of the Sun, making them some of the largest stars known. White pixels were brighter in the December image, black pixels were fainter, and gray pixels did not change. These echoes are reflected light from the original supernova, observed almost 20 years after the initial blast. The powerful Dark Energy Camera, with its 2.
We were seeing light echoes — the original light from the supernova reflected off surrounding dust clouds in the LMC, like sound waves bouncing through the Alps. These light echoes form rings tracing the surfaces of surrounding dust clouds that are located the same distances from the supernova.
Individual rings with different radii represent reflections from sheets of dust at different distances from the explosion.
It turned out that these light echoes had been discovered before by another project, so we had simply rediscovered them. But as Rest continued to scrutinize the observations, he started finding additional light echoes with arcs that corresponded to locations other than that of SN A. These new echoes were from supernovae that had exploded in the LMC centuries ago, yet we were still seeing the original explosions in delayed form.
These light echoes revealed a unique way to study supernovae long after their initial blasts. And while our project ultimately did not find compelling evidence for MACHOs as an important source of dark matter, we still found something totally unexpected — and potentially quite powerful.
The most obvious result of this interaction is the Magellanic Stream and its leading arm, which form of a twisted ribbon of neutral hydrogen gas that astronomer David Nidever of Montana State University found extends over more than half the sky.
Viewed from the LMC, the streamers have the same velocities as those of the strangely moving stars we had previously found. Moreover, we measured the abundance of iron in some of our weird stars, finding they had surprisingly little iron compared to other stars in the LMC. However, they were a good match for SMC stars. Based on the streamers and seemingly migrant stars, we concluded that the LMC had stolen stars from its smaller sibling, the SMC. This scenario would explain why 30 Doradus is forming stars so aggressively.
The infalling material provides external pressure on 30 Doradus and keeps the stellar winds and supernovae within from completely blowing away the nearby gas, which would halt further star formation.
These ripped-out, massive stars might also be the source of the microlensing events that were seen in the s, which would further rule out MACHOs as a significant source of dark matter scattered throughout the Milky Way. With better data and more sophisticated theoretical models, exactly how the Magellanic Clouds have been interacting with each other over the eons is becoming clearer by the year.
Astronomer Nitya Kallivayalil of the University of Virginia and others have been hard at work measuring the 3D motions of nearby galaxies, including the Magellanic Clouds. They have determined that the clouds are only loosely bound, if at all, to the Milky Way. Astronomer Gurtina Besla of Steward Observatory has led work to model the motions of the clouds, finding that the LMC and SMC have made several close passes over the past few billion years — and that they likely collided with each other about million years ago.
This is why my current interest, and that of many others, is to map the sky in search of these stars. The Victor M. Blanco Telescope in Chile collects observations for the Dark Energy Survey, as a nearby astronomer takes in the spectacular night sky and the goliath scope. In , two groups — one led by astrophysicist Keith Bechtol of the University of Wisconsin-Madison and the other by Sergey Koposov of Carnegie Mellon University — used the DES data to discover eight new extremely faint, low-mass dwarf galaxies.
Some of these galactic specters have locations, distances, and velocities that make them likely satellites of the Magellanic Clouds — in other words, satellites of satellites. Looking for galaxies in all the wrong places. Astronomers confirm the Large Magellanic Cloud is a galactic cannibal. Found: The first exoplanet outside of our Milky Way. Arp 91 showcases a cosmic union in deep space.
Ask Astro : Can a black hole form without a parent star? Astronomers get a 3D look at nearby stellar nurseries. Credit : AAO. Lying only about , light years away, they were the closest known galaxies to the Milky Way until recently, when the Sagittarius and Canis Major dwarf galaxies were discovered and found to be even closer.
Although very close to us, the Magellanic Clouds have played a significant role in our understanding of the distant Universe. Magellan's discovery of the LMC and SMC predated telescopes, but even after the instruments allowed Galileo and astronomers in the 17th century to get a closer look, it was still several hundred years before scientists could accurately calculate the distance to the LMC, the SMC and other nearby galaxies.
Scientists came to better understand cosmic distances using tools such as " standard candles " objects, such as certain types of variable stars, that have known luminosities. From then on, the LMC was considered the closest galactic object to Earth until , when astronomers found the Sagittarius dwarf elliptical galaxy , according to NASA.
Another discovery in , the Canis Major dwarf galaxy , turned out to be even closer. The LMC is part of a collection of dozens of galaxies known as the Local Group , so named because they are fairly close to our own Milky Way galaxy.
The most prominent member is the Andromeda galaxy, a Northern Hemisphere object visible with the naked eye just north of the constellation of the same name. The Andromeda galaxy is 2.
Other than its proximity to Earth, the LMC is also known for being a site where stars form. Within the LMC's borders, several observatories from NASA and other space agencies have witnessed vast amounts of gas coming together to create young stars.
A composite image of the Tarantula Nebula — a region of the LMC more properly known as 30 Doradus — revealed violence and radiation through the lenses of the Hubble, Chandra and Spitzer space telescopes. Images captured by the Hubble Space Telescope show that this region consists of several pockets of gas and numerous brilliant new stars. It is also close enough to study in detail less than a 10th of the distance to the Andromeda galaxy, the closest spiral galaxy and lies almost face-on to us, giving us a bird's-eye view.
The LMC's relatively close location to Earth also affords astronomers the chance to study it in more detail, with the aim of extrapolating information that can help explain how other galaxies behave.
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