A Potential Wormhole Detection Method

A Potential Wormhole Detection Method

physics   October 29, 2019

Credit: Shutterstock

Wormholes have been ubiquitous in science fiction for a long time. The prospect of a portal which transports you across the universe is too good to pass up. Surprisingly, wormholes are now a physical possibility. Wormholes agree with Einstein’s general theory of relativity, which means their existence is permitted by the laws of physics. However, just because they can exist, doesn’t mean they do exist, since a positive detection of wormholes has never been made. Recently, physicists De-Chang Dai and Dejan Stojkovic published a paper outlining what a possible wormhole detection could look like, and how to look for them.

An important thing to note is that wormholes are two-directional. Theoretically, if objects can travel from point A to point B using the wormhole, then they can also travel from point B back to point A. This paper rests on the fact that if matter can be exchanged in this manner across a wormhole, then forces must also behave in the same way. For example, if a negative charge is on side A of a wormhole, and a positive charge is on side B of a wormhole, then the two charges experience an attraction to one another, due to the electromagnetic force transmitted across the wormhole. To an observer unaware of the wormhole on side A, this behaviour would look very strange, as it would appear that the negatively charged particle is experiencing a force from nowhere.

The authors propose that a similar method could be used to detect wormholes candidates. Rather than charged particles, however, the paper suggests using stars as wormhole detectors. One popular idea is that black holes themselves may harbour wormholes. Suppose we want to determine whether the black hole in the centre of our galaxy, Sagittarius A*, contains a wormhole. The paper suggests observing the orbits of stars around Sagittarius A* and looking for any unexplained deviations. Such deviations may suggest that the stars are experiencing gravitational attraction to massive objects, like other stars, on the other side of the wormhole.

Unfortunately, there is a catch. Unexpected deviations in the stars’ orbits may be caused be the black hole containing a wormhole, but this is not the only potential cause. There exist many other explanations that do not include wormholes which can explain the perturbation of a star’s orbit around a black hole, such as other stars which may be obscured from view. Consequently, although this paper proposes an exciting prospect, it is by no means a definitive detection method.

Read the original research paper here: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.083513

The 2019 Nobel Prize in Physics

The 2019 Nobel Prize in Physics

physics   October 27, 2019

Credit: Nobel Institute

On October 8, the 2019 Nobel Prizes in Physics were announced. This year, there were three recipients: Swiss astrophysicists Michel Mayor and Didier Queloz, and Canadian physicist James Peebles. Peebles will receive one half of the associated monetary prize, and Mayor and Queloz will split the other half.

Michel Mayor and Didier Queloz are being recognized for one of the most revolutionary discoveries in modern astronomy: the detection of the first exoplanet orbiting a main sequence star. The planet 51 Pegasi b, also known as Dimidium, was discovered in 1995 around the star 51 Pegasi 47.9 lightyears from Earth using the radial velocity method. It had a mass of around 146 Earth masses and orbited its host star in 4.23 days. This discovery proved to the scientific community and the world at large that planets exist beyond the solar system. Since then, exoplanetary astronomy has experienced a massive boom in research, resulting in over 4,000 known exoplanets.

51 Pegasi b is a significant discovery not just because it demonstrated that exoplanets exist, but because it showed astronomers that exoplanetary systems will vary greatly from our own. 51 Pegasi b is the only planet in its system, and it is a Jupiter-sized planet that orbits its star very closely. Comparing this to our own eight-planet system, where the closest gas giant to the Sun takes 12 years to orbit the Sun, this system is in stark contrast to our own. 51 Pegasi b is the original “hot Jupiter”, a class of planet that further research has shown is one of the most common types of exoplanet. This discovery paved the way for the exoplanetary astronomy of today, which will hopefully culminate in the discovery of truly habitable worlds, and perhaps extraterrestrial life, sometime in the future.

James Peebles is being recognized for his ground-breaking contributions to theoretical studies in physical cosmology. Once, physical cosmology was not considered a serious or rigorous branch of physics. However, thanks to the work of physicists such as Peebles, it is now our best tool for understanding how the origins and eventual fate of the universe. He has been previously recognized by the Shaw Prize, whose citation for Peebles stated that he transformed “a highly speculative field into a precision science."

Peebles made significant contributions to the Big Bang model, our current theory which describes the origin of the universe. He also predicted several ways in which the Big Bang model could be experimentally supported, such as the cosmic microwave background (CMB). He made further significant contributions to big bang nucleosynthesis, models of the formation of large-scale structure in the universe, and the ever-mysterious dark matter and dark energy. The significance of Peebles’ career cannot be understated, as thanks to his work, we have an exceptional understanding of the origin and evolution of the universe. Studies in physical cosmology will ideally lead to, sometime in the future, a complete understanding of dark matter and dark energy; this would be a grand triumph in our quest to understand reality.

TESS Discovers a New Class of Exoplanet

TESS Discovers a New Class of Exoplanet

astrophysics   August 16, 2019

Credit: NASA

Although exoplanetary astronomy may be a relatively young scientific field, over 4 000 exoplanets are known today. From this vast set of data, scientists have been able to determine that there are general classes which almost every exoplanet falls into, such as Super-Earth, Mini-Neptune, and Hot Jupiter. However, recent observations by NASA’s TESS (Transiting Exoplanet Survey Satellite) have identified a completely new class of exoplanet: the Ultrahot Neptune.

Astronomer James Jenkins reported the discovery of the planet in question, LTT 9779b, at the TESS Science Conference on July 29th. The planet was first identified as a candidate using TESS, and subsequent observations were conducted by HARPS (High Accuracy Radial Velocity Planet Searcher). LTT 9779b orbits the star LTT 9779, a sun-like and high metallicity star situated around 260 light years from our solar system. Thanks to these observations, astronomers were able to determine that the planet orbits its host star in a mere 19 hours, which places it extremely close to the star. Further measurements determined that the planet has a radius of 4.6 Earth radii, and a mass of 29.3 Earth masses. This positions it firmly in the Neptune-like category of planets, but it is the first such Neptune-like planet to be discovered so close to its star.

Interestingly, it appears that hardly any planets with Neptune-like mass have orbits of four days or fewer around their star. Rather, the most commonly-found planets this close to their star are Super-Earths, or planets with masses greater than that of Jupiter. These results, plus the proximity of the planet causing it to have a temperature around 2000 kelvins, categorizes LTT 9779b as a planet in the Neptunian desert. This collection of traits has never been observed before, and thus, the Ultrahot Neptune class is born.

Studying LTT 9779b will provide crucial insights into the existence of the Neptunian desert, and the evolution of gas planets. Current theories seem to suggest that gas planets often form farther out from their star, then move closer in over time. As the planet migrates nearer to its star, its orbital period decreases, and its temperature greatly increases. Furthermore, the decreasing distance between the planet and the star results in an increase in the concentration of solar wind particles, and the star slowly strips the planet of its atmosphere. Scientists hypothesize that the Neptunian desert exists because Jupiter-like planets migrate extremely close to their stars, stripping off their atmospheres, and leaving behind only a rocky core. This suggests that the newly discovered Ultrahot Neptune is perhaps a transitionary phase from Hot Jupiter to Super-Earth.

The next steps for research are to determine the rate at which LTT 9779b is losing mass due to its star. If the rate at which it loses mass is fast on astronomical time scales, then perhaps this is the reason no other Ultrahot Neptunes have been discovered until now: they simply exist for too short a time.

Read the presentation abstract here: https://tsc.mit.edu/docs/Talk_Abstracts.pdf

Two Earth-Like Exoplanets Detected Orbiting Nearby Star

Two Earth-Like Exoplanets Detected Orbiting Nearby Star

astrophysics   July 03, 2019

Image Credit: Planetary Habitability Laboratory

The search for life elsewhere in the universe has just received another major boost. An international team led by the University of Göttingen has detected two planets orbiting the 24^th-nearest star to the Sun. Teegarden’s star is a red dwarf situated around 12.5 light years away from our solar system, and is approximately eight billion years old. More importantly, it is home to two Earth-like planets, Teegarden b and Teegarden c.

Both planets are believed to be terrestrial (rocky) worlds. Teegarden b has a mass of 1.05 Earth masses, orbits 0.0252 AU from its star, and takes a mere 4.91 days to complete a single orbit. Similarly, Teegarden c has a mass of 1.12 Earth masses, orbits 0.0443 AU from its star, and completes one orbit in 11.409 days. Both planets are among the 19 most habitable planets known to science out of a total of 4000 known planets. In fact, Teegarden b has the highest ESI (Earth Similarity Index) discovered so far.

Although it is possible that both planets could host liquid water on their surfaces, Teegarden b is the favoured candidate for habitability. There is a 60% chance that it has a temperate surface environment, indicating a range of temperatures from 0 to 50°C. This temperature could vary based on atmospheric composition, with 28°C being the likely surface temperature if the planet has an Earth-like atmosphere. Contrastingly, there is only a 3% chance that Teegarden c has a temperature surface environment, with the surface temperature likely being around -47°C if the planet has an Earth-like atmosphere.

Although these initial findings seem promising, especially for Teegarden b, further study is required to determine the extent to which these planets are habitable. These planets were discovered using the radial velocity method, and are unfortunately non-transiting. This means that in order to determine other key characteristics such as radius, direct observation with a future telescope such as the James Webb Space Telescope may be required. As well, red dwarfs are known to emit violent flares, which could be capable of destroying the planets’ atmospheres and sterilizing their surfaces. Due to how close the planets orbit their star, they may be tidally locked, meaning one side of the planet would face the star at all times. This could create two extreme sides to the planet, rather than an overall temperature climate, rendering the planets uninhabitable. Follow-up studies will be required in the future to further assess the habitability of these two worlds.

Read the original research paper here:

https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/201935460

Mystery of Galaxy Thought to be Devoid of Dark Matter Resolved

Mystery of Galaxy Thought to be Devoid of Dark Matter Resolved

astrophysics   June 15, 2019

Image: NASA/Hubble Space Telescope

Dark matter is the most abundant physical substance in the universe, occurring five to six times more than the ordinary matter we are made of. On smaller scales, dark matter is thought to play a critical role in the formation of galaxies. Last year, however, our current understanding of galactic formation was jeopardized by the discovery of NGC1052-DF2, a galaxy which appeared to be completely devoid of dark matter.

Due to the puzzling nature of NGC1052-DF2, a group of researchers led by the Instituto de Astrofísica de Canarias re-examined all the data associated with the original study. The conclusion that the galaxy had no dark matter was based on the measurement of the distance to the galaxy. This distance had been previously determined in another study to be around 20 megaparsecs, or approximately 65 million light years away. The team then used multiple independent measurement methods, and carefully determined the distance to NGC1052-DF2. They determined that in reality, this galaxy is 13 megaparsecs away, only 65% the previously measured distance.

This anomaly implied that the previously determined measurement of the galaxy’s mass was also incorrect, with the galaxy’s true mass being half of what it was thought to be. From this, they were able to ascertain that the mass of the stars within the galaxy is around 25% of the believed value. Using this result, the team finally concluded that NGC1052-DF2 does have dark matter after all; in fact, the galaxy’s mass seems to be around 75% dark matter. These revised measurements allowed the team to show that there is “plenty of room for dark matter” in this galaxy.

The dark matter-free galaxy mystery has not been resolved yet. The same group of researchers who wrote the original paper on NGC1052-DF2 wrote another paper a different galaxy, NGC1052-DF4, where dark matter is also seemingly absent. The researchers led by the Instituto de Astrofísica de Canarias are conducting a study on the distance to NGC1052-DF4, and it appears that it may also have been measured to be farther away than it is. It appears this mystery should soon be put to rest once and for all.

Read the original research paper here:

https://academic.oup.com/mnras/article-abstract/486/1/1192/5380810?redirectedFrom=fulltext

The Production of Heavy Elements via Collapsars

The Production of Heavy Elements via Collapsars

astrophysics   May 16, 2019

The gold in your jewelry and the uranium powering nuclear reactors might seem entirely unrelated. However, in a paper published in Nature, two astrophysicists suggest that many of the heavy elements found throughout the universe are created as a result of a collapsar, a rare kind of supernova.

Collapsars occur when a rapidly-rotating, high-mass star collapses into a black hole, causing the outer layers to explode in a supernova. As the star dies, its core undergoes a catastrophic gravitational collapse resulting in the formation of a black hole, leading to the supernova explosion of the outer shell. Then, the remnants of the star fall into orbit around the black hole, creating a vortex of high-energy lighter elements. In this extreme scenario, the conditions are right enough to allow a nuclear process known as the r-process take place, causing many of the heavy elements of the universe to form.

It was previously thought that the majority of elements formed via the r-process were a result of neutron star mergers. Nonetheless, a recent analysis of the galactic abundance of one of these r-process elements, europium, seems to indicate that a different mechanism was supplying the universe with the multitude of heavy elements we see today.

The authors of this study identify collapsars as a likely source. In fact, over 80% of r-process elements could be formed via collapsar-catalyzed nuclear reactions. Although collapsars are much rarer than neutron star mergers, they produce a much greater quantity of these r-process elements, explaining  why they create the majority of heavy elements in the universe.

Read the official research paper here:

https://www.nature.com/articles/s41586-019-1136-0