C/2014 UN2071: Largest Discovered Comet

Posted on April 17, 2022 by evang914
Hubble Telescope image and computer model of C/2014 UN2071, via Smithsonian Magazine

Scientists in the past week have confirmed the size of the largest comet ever discovered. It is measured to stretch over 80 miles wide (wider than the state of Rhode Island) and weigh 500 trillion tons- 100,000x more than the typical comet.

The comet was originally discovered back in 2014 when it was still 3 billion miles from the sun. It was suspected the comet was atypically large given its brightness at that distance. Images of the comet were taken by the Hubble Telescope earlier this year, and the scientists were able to use a computer model to make the determination of its size by removing the coma (the dust/ice cloud a comet gives off) from the solid nucleus. As a comet gets closer to the sun, the increased heat causes the coma to expand.

The comet is currently traveling in our general direction at 22,000 mph and is expected to reach its closest approach in 2031, although it will still be 1 billion miles away. However, astronomers are hoping that observing the comet will give them a better clue about the types of objects that exist in the Oort Cloud, where the comet originated from. Although we know of their existence, objects from the Oort Cloud have yet to be directly observed. Despite this being the largest comet discovered to date, astronomers believe more objects of similar size exist out there.

Source: Phys Org

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New Horizons Still Bringing New Discoveries

Posted on April 17, 2022 by evang914
Image analysis highlighting areas where volcanic activity is believed to have occurred, via NYT

It’s been nearly 7 years now since the New Horizons spacecraft made its fly-by of Pluto, and even though it now finds itself in the remote parts of the Kuiper Belt (over 50 AU from the sun!), the photos it took of Pluto are still helping scientists today uncover new mysteries about the icy planet.

A few weeks ago, researchers from the Southwest Research Institute (the same institute where Dr. Stern works) published a paper in the Nature Communications journal stating they believe they have found evidence of recently erupted ice lava near two of Pluto’s mountains long suspected of being ice volcanos: Wright Mons and Picard Mons. They now believe the two mountains were formed from a small colony of cryovolcanic domes. The researchers came to the conclusion that they were looking at ice lava deposits after differentiating the irregular, undulating surface of water ice from other surface areas of Pluto shaped by erosion.

The confirmation of recently erupted ice volcanos provides further proof for the existence of recent and possibly current geologic activity within Pluto and the internal heat source that would be required for volcanism to take place. Icy lava also requires there to be liquid beneath the surface of pluto within an astronomically recent time period, also providing scientists greater support for there being a liquid ocean of water beneath the surface of the planet.

Although it is suspected the volcanos have been active sometime in the past 200 million years, scientists are unsure if they are still active today. The discovery shows, though, how researchers are still using data sent from the New Horizons spacecraft to better understand the planet.

Source: New York Times

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Blog #6: Enceladus’s Tiger Stripes

Posted on April 17, 2022 by nadiamcglynn

The Cassini Spacecraft revealed dramatic geysers spewing from Enceladus’s tiger stripes, horizontal, nearly parallel fissures near the moon’s south pole, in 2006. It was believed that these may have been caused by “cryo-volcanism” (icy volcanos!), but new research suggests that it may be caused by the changes in the eccentricity of Enceladus’s orbit over 100 Myr timescales.

NASA, ESA, JPL, SSI, Cassini

During each orbit of Saturn, the icy “crust” of Enceladus goes through periods of thickening and thinning, which occurs at the bottom of the global ice shelf in a process similar to the way a lake freezes from top to bottom.

This expansion of ice can increase the amount of pressure exerted on the sub-crustal ocean, the increasing pressure also stresses the ice, which can lead to the fissures that allow the liquid water to travel through the 20-30 km barrier to the surface. This pressure would be enough to cause the ‘tiger stripes,’ but not enough to facilitate the geysers we have observed.

A study from 2016 proposed that the water that makes it into the stress induced fractures in the ice would immediately boil when exposed to the vacuum of space, producing the geysers. A study published in February of this year agrees that this is a viable process on Enceladus, but perhaps not on Europa, a similar icy planet experiencing similar icy eruptions.

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Blog #5: AR Aur b (protoplanet formation caught in action!)

Posted on April 17, 2022 by nadiamcglynn

As we have been able to look farther outside of our neighborhood of the solar system, our understanding of extrasolar planets and the formation of other planetary systems has had to undergo questions and testing to ensure that our hypothesis is reasonable. The surprising orbits of some extrasolar planets has caused some such questioning, such as “Is it possible for jovian planets to form very close to a star?” (Textbook, pg 392). Studying what data we can collect from the formation of other planetary systems is important to solidifying our ideas of the universe and solar system evolution.

We believe that our jovian planets formed through accretion in the gaseous protoplanetary disk, first acquiring icy/rocky cores of a certain mass and then gathering surrounding gas (mainly hydrogen and helium with some differences between planets) to become the “gas giants” that we observe today. This process is feasible for planets that orbit relatively close to their host star, but what about for giant planets with a wider orbit? These farther out planets would not have time to accrete a sufficiently massive core.

The disk instability model is a model proposed to explain the formation of planets with masses of ∼1 M☉ to ∼2 M☉ with orbital distances of 20-120 AU. This theory suggests that areas of the protoplanetary disk may become cooler and denser than other areas, leading to gravitational instability that allows a gaseous planet to form. Up until now there hasn’t been much convincing evidence for the model.

A team of scientists studying the star AB Aurigae found a protoplanet about 9 times as massive as Jupiter orbiting at 93 AU! They named this planet AB Aur b. It can be seen in the picture below as the lower bright blob orbiting the star, which has been blocked out so that the light does not disrupt in observing the orbits of the protoplanetary disk.

AB Aur b in the planetary disk, Thayne Currie/Subaru Telescope

This discovery presents some evidence for the unstable disk theory. Other theories for how these wide orbit, massive planets form may be planetary migration as described in our textbook.

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‘Oumuamua: An Interstellar Visitor

Posted on April 17, 2022 by Quint Gfroerer
An artist’s rendition of what ‘Oumuamua might have looked like (The Guardian)

In 2017, a small, long object between 100 and 1,000 meters in length and between 35 and 167 meters in height and width passed through the inner solar system with a trajectory and speed only possible if it originated from beyond our solar system. This object, now known as ‘Oumuamua, is one of the first discovered to have an interstellar origin, and exhibited many unusual characteristics we have yet to explain.

‘Oumuamua passed inside of Mercury’s orbit, then traveled within 0.17 astronomical units of Earth (1 AU is the distance from Earth to the Sun) before taking a trajectory leading it outside of the solar system. When traveling away from the Sun, ‘Oumuamua’s speed increased by an amount typically indicative of comet outgassing. However, no such outgassing was observed. ‘Oumuamua also exhibited an atypical tumbling motion for objects with a high length-to-width ratio. These unusual characteristics, along with its abnormal elongated shape, have led some to theorize that the object was constructed by aliens, however most experts deem this to be very unlikely. Regardless, ‘Oumuamua is a fascinating object both in its characteristics and its extrasolar origin, and is perhaps among the first of many interstellar objects to be discovered.

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Blog#6 Red Giant and White Dwarf

Posted on April 17, 2022 by Irene

Pauli Exclusion Principle (Wikipedia): every electron is indistinguishable from another. Two identical electrons cannot locate in the same volume of space with the same exact properties (energy, spin, direction) Thus, the electron has to be excluded from this space or remain at the higher energy level. 

HR diagram

When a main-sequence star (Wikipedia) comes towards the end of its life, the pressure at its core is so high that all electron states are filled. Therefore, electrons become degenerate (Wikipedia) they are forced to have higher energy than they should have at their temperatures due to Pauli Exclusion Principle. Therefore, its He core collapses, and stars climb to the red giant branch until the core temperature reaches 10^8K, then He fusion begins in the core (helium will become carbon). This process occurs at the top of the red giant branch. Moreover, the star’s core volume will be bigger due to He fusion, so there will no longer be any electron degeneracy, all energy restored due to degeneracy will be released at one, causing Helium Flash (Wikipedia)

Helium Flash

Therefore, the star will drop to a horizontal branch and becomes a red supergiant. The carbon core will slowly collapse and the H&He burning shall overcome gravity. Dust forms in outer space, light energy pushes out dust, and dust pushes gas, the outer envelope will slowly be blown away, forming a Planetary nebula (Wikipedia).

Planetary Nebula

The collapsing carbon core henceforth becomes White Dwarf (Wikipedia). Whit dwarves have balance between gravity and degeneracy and are very dense. They cannot shrink anymore. They will cool off eventually. 

White Dwarf

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Enceladus: Alien Life in Our Own Solar System?

Posted on April 17, 2022 by Quint Gfroerer
Enceladus, one of Saturn’s moons (NASA)

Enceladus is an icy moon of Saturn, and is fairly small (or medium-sized, for a moon) with a diameter of about 500 km. For reference, the Moon has a diameter of about 3,475 km. Despite its size, however, Enceladus has been rated as among the most probable sources of life in our own solar system outside of Earth. Scientists think this might be possible because Enceladus has a large subsurface ocean below a layer of ice which is about 35 km thick. Its ocean is estimated to be about 28 km thick, which is almost eight times the average depth of Earth’s ocean. Enceladus experiences internal heating due to tidal forces from Saturn and other moons, which causes large geysers on its icy surface, and makes oceanic volcanism possible at the bottom of its massive subsurface ocean. This last point is especially significant, as life on Earth is theorized to originate from similar oceanic volcanic environments.

What bolsters this point even more is that methane, carbon dioxide, and dihydrogen have been recorded in Enceladus’ geyser plumes, which is best explained by oceanic volcanism. These chemicals were also recorded in levels that current Earth-based models cannot explain unless one factors in the role of life in generating methane at the volcanoes. This does not indicate life on Enceladus, as there could be other explanations for the levels of methane and carbon dioxide in the geyser plumes, but it is significant nonetheless that life would be the best explanation for these chemical levels if they were observed on Earth. In summary, Enceladus has both an environment that would make extraterrestrial life possible and levels of certain chemicals that would be consistent with the presence of life on the moon. Thus, Enceladus is a very interesting moon that definitely warrants further scientific study.

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Blog#5 Pluto

Posted on April 17, 2022 by Irene

Pluto, formerly considered one of the nine planets, has always been controversial. Nonetheless, since the International Astronomical Union redefined the meaning of planet (A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit) (check IAU Website for further information)

Pluto now falls into the category of a dwarf planet because of its size and the fact that it inhabits a region of other similarly sized bodies known as the Trans-Neptunian region. A dwarf planet is a celestial body that -orbits the sun, has enough mass to assume a nearly round shape, has not cleared the neighborhood around its orbit and is not a moon.

Definition of Dwarf Planet and Examples Cr. NASA

NASA’s New Horizons mission is the first mission that conducted a Pluto flyby and provided humans with a high resolute picture of Pluto. 

Pluto has one important moon: Charon. Half the size of Pluto, Cajun is the largest moon of Pluto and the largest known moon relative to its parent body. Pluto and Charon are considered binary systems and experience tidal locking. NASA’s New Horizons mission discovered that the reddish north cap of Charon is atmospheric outgassing from Pluto. 

Charon Cr. NASA
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Magnetar — A Fascinating Neutron Star

Posted on April 17, 2022 by sissichen17

Neutron stars are the collapsed core of the massive stars (our Sun cannot qualify that). Neutron star was the smallest and densest stellar object in the universe. A city-sized neutron star can obtain the mass of the Sun. There are two types of neutron stars — magnetars and pulsars. Pulsars are neutron stars with fast rotational rates, and magnetars — as the name states — are neutron stars with extremely large magnetic fields. Magnetar — my favorite object in the whole universe —  formed from a fascinating process. During the formation when the supernova explosion happened, the magnetic field increases due to the conservation of magnetic flux. Strong magnetic fields originated from magnetar originated from the magnetohydrodynamic dynamo process before neutron stars reached equilibrium configuration. Through the dynamo process, heat and rotational energy will convert into magnetic energy. Strong magnetic fields exist and persist because of the currents in a proton-superconductor phase of matter. Giant flares, the strong eruptions caused by magnetars, burst gamma rays and give enormous information & interesting phenomenon about this mysterious star.

Picture of Magnetar from Space
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Blog Post 5: Comets and their Tails

Posted on April 17, 2022 by isaachuggins
Halley’s Comet, one of the most famous comets that routinely comes back to the terrestrial worlds and can be seen. Credit to Wikipedia.

Comets are large balls of dust, rock, and ice that travel across our solar system and other solar systems. They are large like asteroids, around 10 km in diameter in our solar system. The largest one in our Solar System is Bernardinelli-Bernstein, a massive body about 85 miles in diameter. These objects can approach near Earth and can be seen in the night sky on regular intervals, due to their orbits being predictable and tracked by scientists.

The comet is made of three main parts; the nucleus, the comma, and the tails. The nucleus is the center of the comet, or the actual rock itself. It is made of dust and ice, which remains stagnant and stable in the outer solar system. However, once the comet approaches the center, the ice begins to sublimate away. This area is known as the comma. This atmospheric layer only appears when the object is getting close to the sun, making the object glow bright.

The tails extend thousands of miles behind. There are two tails, a plasma tail and a dust tail. One of them is made of plasma, which is blasted away from the sun by solar wind. The dust tail is made of physical objects, which is blasted away by the sun’s radiation pressure. Both of these tails always face away from the sun, even when moving away from the sun. The tails get larger closer to the sun, since these forces are much greater when closer.

The orbit of a comet, where the tail gets larger as it gets closer to the sun. Credit to the European Space Agency.

One of the reasons why comets are so interesting is because they come from such far distances, yet we can still observe them due to their orbits occasionally coming close to the terrestrial planets. It takes millions of dollars to get photos from an object far away such as the Kuiper Belt. Comets are opportunities for such objects to come to us instead. The comet mentioned before, Bernardinelli-Bernstein, may originate from the Oort Cloud, and will be within Saturn’s orbit by 2032. Even better, some comets come so close that we can see them as pronounced objects in the night sky. Halley’s comet comes every 75 years, and is predicted to come again around 2061.

Remember, comets, just like Tails the fox, have two tails. Credit to Wikipedia.
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