We can Probably Find Supernovae Enhanced by Gravitational Lensing, We Just Need to Look

Using the microlensing metthod, a team of astrophysicists have found the first extra-galactic planets! Credit: NASA/Tim Pyle

Gravitational lensing provides an opportunity to see supernovae and other transients much farther than we normally can. A new research proposal outlines a plan to use a comprehensive catalog of strong gravitational lenses to capture these rare events at extreme distances.

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A Gravitational Lens Shows the Same Galaxy Three Times

This star- and galaxy-studded image was captured by Hubble’s Wide Field Camera 3 (WFC3). The galaxy visible in the bottom right corner of the image, named SGAS 0033+02 is a triple gravitational lens. Credit: ESA/Hubble & NASA, E. Wuyts.

Images from the Hubble Space Telescope are often mind-bending in both their beauty and wealth of scientific wonder. And sometimes, Hubble captures light-bending images too.

Hubble’s Wide Field Camera 3 (WFC3) snapped a photo of a galaxy where the light has been bent by gravitational lensing, so that the galaxy show up not just once, but three times. But the multiple views aren’t exact replicas of each other — they appear as different shapes.

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What a Perfect Gravitational Lens

Clustered at the centre of this image are six luminous spots of light, four of them forming a circle around a central pair. Credit: ESA/Hubble & NASA, Acknowledgment: J. Schmidt

A stunning new photograph from the Hubble Space Telescope shows a nearly perfect Einstein Ring, an effect caused by gravitational lensing. This is one of the most complete Einstein Rings ever seen.

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Gaia Finds 12 Examples of Einstein Crosses; Galaxies Being Gravitationally Lensed so we see Them Repeated 4 Times

Credit and : R. Hurt (IPAC/Caltech)/The GraL Collaboration

In 1915, Einstein put the finishing touches on his Theory of General Relativity (GR), a revolutionary new hypothesis that described gravity as a geometric property of space and time. This theory remains the accepted description of gravitation in modern physics and predicts that massive objects (like galaxies and galaxy clusters) bend the very fabric of spacetime.

As result, massive objects (like galaxies and galaxy clusters) can act as a lens that will deflect and magnify light coming from more distant objects. This effect is known as “gravitational lensing,” and can result in all kinds of visual phenomena – not the least of which is known as an “Einstein Cross.” Using data from the ESA’s Gaia Observatory, a team of researchers announced the discovery of 12 new Einstein Crosses.

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Dark Energy Survey Finds Hundreds of New Gravitational Lenses

It’s relatively rare for a magical object from fantasy stories to have a analog in real life.  A truly functional crystal ball (or palantir) would be useful for everything from military operations to checking up on grandma. While nothing exists to be able to observe the mundanities of everyday life, there is something equivalent for extraordinarily far away galaxies: gravitational lenses.  Now a team led by Xiaosheng Huang from Lawrence Berkeley National Laboratory (LBNL) and several universities around the world have published a list of more than 1200 new gravitational lensing candidates.

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If We Used the Sun as a Gravitational Lens Telescope, This is What a Planet at Proxima Centauri Would Look Like

mage of a simulated Earth, at 1024×1024 pixel resolution, at the distance of Proxima Centauri,at 1.3 pc, as projectedby the SGL to an image plane at 650 AU from the Sun. Credit: Toth H. & Turyshev, S.G.

As Einstein originally predicted with his General Theory of Relativity, gravity alters the curvature of spacetime. As a consequence, the passage of light changes as it encounters a gravitational field, which is how General Relativity was confirmed! For decades, astronomers have taken advantage of this to conduct Gravitational Lensing (GL) – where a distant source is focused and amplified by a massive object in the foreground.

In a recent study, two theoretical physicists argue that the Sun could be used in the same way to create a Solar Gravitational Lens (SGL). This powerful telescope, they argue, would provide enough light amplification to allow for Direct Imaging studies of nearby exoplanets. This could allow astronomers to determine if planets like Proxima b are potentially-habitable long before we send missions to study them.

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Gravitational lenses could be the key to measuring the expansion rate of the Universe

Illustration of gravity waves from a neutron star merger. Credit: NRAO/AUI/NSF

One of the tenets of our cosmological model is that the universe is expanding. For reasons we still don’t fully understand, space itself is stretching over time. It’s a strange idea to wrap your head around, but the evidence for it is conclusive. It is not simply that galaxies appear to be moving away from us, as seen by their redshift. Distant galaxies also appear larger than they should due to cosmic expansion. They are also distributed in superclusters separated by large voids. Then there is the cosmic microwave background, where even its small fluctuations in temperature confirm cosmic expansion.

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A Rogue Earth-Mass Planet Has Been Discovered Freely Floating in the Milky Way Without a Star

An artist's impression of a rogue planet. Image Credit: By Interpott.nrw - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=83123717

If a solar system is a family, then some planets leave home early. Whether they want to or not. Once they’ve left the gravitational embrace of their family, they’re pretty much destined to drift through interstellar space forever, unbound to any star.

Astronomers like to call these drifters “rogue planets,” and they’re getting better at finding them. A team of astronomers have found one of these drifting rogues that’s about the same mass as Mars or Earth.

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Meet WFIRST, The Space Telescope with the Power of 100 Hubbles

The Wide First Infrared Telescope (so far). Image credit: NASA/TJT Photography

WFIRST ain’t your grandma’s space telescope. Despite having the same size mirror as the surprisingly reliable Hubble Space Telescope, clocking in at 2.4 meters across, this puppy will pack a punch with a gigantic 300 megapixel camera, enabling it to snap a single image with an area a hundred times greater than the Hubble.

With that fantastic camera and the addition of one of the most sensitive coronagraphs ever made – letting it block out distant starlight on a star-by-star basis – this next-generation telescope will uncover some of the deepest mysteries of the cosmos.

Oh, and also find about a million exoplanets.

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Astronomers Figure Out How to use Gravitational Lensing to Measure the Mass of White Dwarfs

The technique of gravitational lensing relies on the presence of a large cluster of matter between the observer and the object to magnify light coming from that object. Credit: NASA

For the sake of studying the most distant objects in the Universe, astronomers often rely on a technique known as Gravitational Lensing. Based on the principles of Einstein’s Theory of General Relativity, this technique involves relying on a large distribution of matter (such as a galaxy cluster or star) to magnify the light coming from a distant object, thereby making it appear brighter and larger.

However, in recent years, astronomers have found other uses for this technique as well. For instance, a team of scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) recently determined that Gravitational Lensing could also be used to determine the mass of white dwarf stars. This discovery could lead to a new era in astronomy where the mass of fainter objects can be determined.

The study which details their findings, titled “Predicting gravitational lensing by stellar remnants” appeared in the Monthly Noticed of the Royal Astronomical Society. The study was led by Alexander J. Harding of the CfA and included Rosanne Di Stefano, and Claire Baker (also from the CfA), as well as members from the University of Southampton, Georgia State University, the University of Nigeria, and Cornell University.

A Hubble image of the white dwarf star PM I12506+4110E (the bright object, seen in black in this negative print) and its field which includes two distant stars PM12-MLC1&2. Credit: Harding et al./NASA/HST

To put it simply, determining the mass of an astronomical object is one the greatest challenges for astronomers. Until now, the most successful method relied on binary systems because the orbital parameters of these systems depend on the masses of the two objects. Unfortunately, objects that are at the end states of stellar evolution – like black holes, neutron stars or white dwarfs – are often too faint or isolated to be detectable.

This is unfortunate, since these objects are responsible for a lot of dramatic astronomical events. These include the accretion of material, the emission of energetic radiation, gravitational waves, gamma-ray bursts, or supernovae. Many of these events are still a mystery to astronomers or the study of them is still in its infancy – i.e. gravitational waves. As they state in their study:

“Gravitational lensing provides an alternative approach to mass measurement. It has the advantage of only relying on the light from a background source, and can therefore be employed even for dark lenses. In fact, since light from the lens can interfere with the detection of lensing effects, compact objects are ideal lenses.”

As they go on to state, of the 18,000 lensing events that have been detected to date, roughly 10 to 15% are believed to have been caused by compact objects. However, scientists are unable to tell which of the detected events were due to compact lenses. For the sake of their study then, the team sought to circumvent this problem by identifying local compact objects and predicting when they might produce a lensing event so they could be studied.

Animation showing the white dwarf star Stein 2051B as it passes in front of a distant background star. Credit: NASA

“By focusing on pre-selected compact objects in the near vicinity of the Sun, we ensure that the lensing event will be caused by a white dwarf, neutron star, or black hole,” they state. “Furthermore, the distance and proper motion of the lens can be accurately measured prior to the event, or else afterwards. Armed with this information, the lensing light curve allows one to accurately measure the mass of the lens.”

In the end, the team determined that lensing events could be predicted from thousands of local objects. These include 250 neutron stars, 5 black holes, and roughly 35,000 white dwarfs. Neutron stars and black holes present a challenge since the known populations are too small and their proper motions and/or distances are not generally known.

But in the case of white dwarfs, the authors anticipate that they will provide for many lensing opportunities in the future. Based on the general motions of the white dwarfs across the sky, they obtained a statistical estimate that about 30-50 lensing events will take place per decade that could be spotted by the Hubble Space Telescope, the ESA’s Gaia mission, or NASA’s James Webb Space Telescope (JWST). As they state in their conclusions:

“We find that the detection of lensing events due to white dwarfs can certainly be observed during the next decade by both Gaia and HST. Photometric events will occur, but to detect them will require observations of the positions of hundreds to thousands of far-flung white dwarfs. As we learn the positions, distances to, and proper motions of larger numbers of white dwarfs through the completion of surveys such as Gaia and through ongoing and new wide-field surveys, the situation will continue to improve.”

The future of astronomy does indeed seem bright. Between improvements in technology, methodology, and the deployment of next-generation space and ground-based telescopes, there is no shortage of opportunities to see and learn more.

Further Reading: CfA, MNRAS