Astronomy Oddities 5

 

Active Galactic Nucleus.  An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much higher than normal luminosity across some of the electromagnetic spectrum.  The luminosity is not produced by stars.  The radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy.  It may also be a lot of star formation activity at the core of the galaxy.  There are two types of AGNs.  Type 1 AGNs show broad and narrow emission lines.  Type 2 AGNs show only narrow emission lines.  Some AGNs transition between different spectral types.  They are called changing-look AGNs.  One changing-look AGN is NGC 7582.  The AGN has a short- and long-term X-ray behavior.  [source: Nowakowski, “Astronomers investigate X-ray spectral variability of active galaxy NGC 7582,” phys.org, Apr 7, 2023]

Asymptotic Giant Branch Stars.  The asymptotic giant branch (AGB) is a region of the Hertzsprung-Russel diagram populated by evolved cool luminous stars.  This type of low to intermediate-mass star will appear as a bright red-giant with a luminosity of up to thousands of times greater than the sun.  They are slightly larger and older than our sun, and are known producers of interstellar dust.   The variable intensity of dusty AGBs coincides with variations in the amount of dust these stars produce. This dust can lead to the creation of planets.   [source: University of Tokyo, “Twinkling stars fuel interstellar dust,” phys.org, Apr 6, 2023]

Bernardinelli-Bernstein Comet.  Comet Bernardinelli-Bernstein (BB) is a large Oort cloud comet, first discovered in 2014.  It was first spotted when it was 2.7 billion miles away, the greatest distance at which a comet has been discovered.  It has a nucleus of about 80 miles across and is the largest Oort cloud comet known.  The nucleus is about 50 times larger than found at the heart of most known comets  [source: “Hubble Confirms Largest Comet Nucleus Ever Seen,: www.nasa.gov, April 12, 2022]

Brightest Cluster Galaxy.  A brightest cluster galaxy (BCG) is defined as the brightest galaxy in a cluster of galaxies.  BCGs include the most massive galaxies in the universe. Galaxy clusters can contain hundreds to thousands of individual galaxies, bound together by gravity and surrounded by dark matter and gas.  At the center of these galaxy clusters are the BCGs.  Galaxy clusters funnel new material on the BCGs.  This means that BCGs grow very large.  BCGs have been observed to actively grow new stars.  The cluster seems to be feeding free-floating gas, known as Intracluster Medium (ICM) to the BCG in the middle of the cluster galaxy.  The flow of cool ICM onto the BCG is known as a ‘cooling flow.’  The cluster known as SPT2215 is the most distant and earliest BCG found.  It was formed 5.3 billion years after the Big Bang.  [source: Dunne, “The Most Distant Cooling-Flow Galaxy Cluster Yet Observed,” Astrobites, Apr 3, 2023]

cD Galaxy.  The type-cD galaxy is a giant elliptical galaxy, characterized by a large halo of stars.  They can be found near the center of some galaxy clusters.  The “c” in “cD” refers to very large galaxies.  The “D” refers to the fact that the galaxies appear diffuse.  They are frequently considered the largest galaxies. The cD galaxies likely grow by consuming smaller galaxies.  It is not unusual to have cD galaxies have multiple nuclei.  Some cD galaxies have envelopes over one million light-years in radius.  It is currently thought that CD galaxies are the result of galaxy mergers.  [source: Seigar et al, “Intracluster light and the extended stellar envelopes of cD galaxies,: Monthly Notices of the Royal Astronomical Society, July 2007]

Faint Blue Galaxy.  A faint blue galaxy (FBG) is a small galaxy with low surface luminosity.  They have sparsely scattered blue stars, and very little red stars, which are the most common type of star in most galaxies.  They have no structure or shape.  They are considered as small dwarf-irregular satellite-galaxies undergoing a burst of star formation.  In 2016, an FBG called Leoncino (AGC 198691) was discovered 30 million light-years away.  Astronomers found surprisingly few heavy chemical elements inside this galaxy.  Leoncino has the fewest metals of any observed gravitationally bound star system.  [source: Hays, “Faint blue galaxy could possess Big Bang clues,” UPI, May 12,2016]

Galactic Wind.  A galactic wind is a high velocity stellar wind emanating frommassive stars or black holes.  They are normally observed in starburst galaxies.  The resulting effect is a massive gust of rapidly expanding super-heated gases that can span the length of a galaxy.  The winds cause an outflow of gases and other materiel  into the halo of a galaxy.  It helps spreading metals around a galaxy.  Superwinds are theorized to form in compact starburst galaxies in which star growth is much higher than in other types of galaxies.  A new study shows the effects of galactic winds from the center of NGC 253, located 11.4 million light-years from Earth.  This galactic wind is composed of gas with temperatures of millions of degrees that glows in X-rays.  An amount of hot gas equivalent to two million Earth masses blows away from the galaxy’s center every year.  [source: Cowing, “Chandra Determines What Makes a Galaxy’s Wind Blow,” Space Ref, Apr 4, 2023]

Halo.  The galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component.  The stellar halo is the component of its galactic halo containing stars.  The halo of the Milky Way has about 1% of its total stellar mass.  The Milky Way halo extends to over 100 kiloparsecs from the galactic center.  Astronomers have detected in the stellar halo a group of stars more distant from Earth than any known within our own galaxy.  208 stars inhabit the most remote part of our galaxy.  This halo is a spherical stellar cloud dominated by dark matter.  The furthest star in this halo is 1.08 million light-years away.  [source: Dunham, “Astronomers discover Milky Way galaxy’s most-distant stars,” Reuters, Jan 12, 2023]

HIP 68468.  HIP 68468 is a Sun-like star in the constellation Centaurus.  It is 300 light-years away.  It has two exoplanets orbiting it.  It has a remarkable abundance of elements, such as lithium. This star may have swallowed one or more planets, based on the lithium content and refractory elements discovered near its surface.  This discovery provides an indication that violent histories may be common for planetary systems.  [source: Borzo, “Astronomers discover dark past of planet-eating ‘Death Star’,” University of Chicago News, Dec 15, 2016]

Kepler-78b.  Kepler-78b is an exoplanet around the star Kepler-78.  At the time of its discovery in 2013, it was the exoplanet most similar to Earth in terms of mass, radius, and density.  The planet is 400 light-years away.  It orbits close to its sun and the planet’s surface is 3,680 degrees Fahrenheit.  That is high enough to strip the planet of any stable atmosphere.   [source: “Astronomers Find Earthlike Planet, but it’s Internally Hot,” The New York Times, Oct 30, 2013]

NGC 2419.  NGC 2419 is a globular cluster in the constellation Lynx.  It is about 300,000 light-years from the Solar System.  The cluster is considered part of the Milky Way and takes 3 billion years to make one orbit around the galaxy.  Intrinsically, it is one of the brightest and most massive globular clusters of our galaxy.  It is composed of two different populations of red giant stars, one behind more helium-rich than the other, which does not fit in the current model of globular cluster formation.  This globular cluster does not contain similar amounts of helium as most other globular clusters.  Also, stars in this cluster hold other elements, such as nitrogen, that vary.  It is not sure how NGC 2419 was formed.  [source: Goddard Space Flight Center, “Hubble views multi-generational cluster NGC 2419,” phys.org, Apr 7, 2023]

Rossby Wave.  Rossby waves are a type of inertial wave or ripple naturally occurring in rotating fluids.  They are observed in the atmospheres and oceans and other planets, owing to the rotation of Earth or of the planet involved.  Rossby waves in Earth’s atmosphere help to steer the jet streams and weather patterns.  A recent study offers the best evidence yet that similar large-scale features also exist on the Sun.  An understanding of these features could help scientists to better predict the formation of sunspots and the eruption of solar flares.   [source: Perkins, “Planet-sized ‘waves’ spotted in the Sun’s atmosphere,” Nature, Mar 27, 2017]

Ultra Diffuse Galaxy.  An ultra diffuse galaxy (UDG) is an extremely low luminosity galaxy.  Their lack of luminosity is due to the lack of star-forming gas, which results in these galaxies being reservoirs of very old stellar populations.  Based on discoveries confirmed in 2018, this class of galaxies includes both extremes of dark matter content.  Some UDGs consist almost entirely of dark matter, while other UDGs appear to be almost entirely free of dark matter.  DGSAT 1 is a UDG as big as our Milky Way galaxy, but its stars are spread out so thinly that it is nearly invisible.  Most UDCs are found in clusters.  DGSAT is sitting all alone and is considered a living fossil.  Only two UDGs have been found in the Local Group, a small cluster that has 60 known galaxies, including the Milky Way and Andromeda.  Scientists believe that understanding the total number of UDGs in the Local Group is crucial to our understanding of the cosmos.  [source: Leibniz Institut for Astrophysik, “Researchers predict a large population of ultra-diffuse local galaxies,” phys.org, March 31, 2023]

Valles Marineris.  The Martian canyons known as Valles Marineris are over 2,500 miles long, 120 miles wide, and 23,000 feet deep.  It is more than 10 times as long as the Grand Canyon.  It was named after the Mariner 9 Mars orbiter of 1971-72, which discovered it.  It is the largest canyon system in our solar system.  It has two trenches or chasms, called chasmata.  The first is Ius Chasma that is 522 miles long.  The second is Tithonium Chasma that is 500 miles long.  The lack of active plate tectonics on Mars makes it tough to figure out how the canyon formed.  [source: Anderson, “See Mars’ Grand Canyon in stunning new photos,” EarthSky, July 28, 2022]

Van Allen Belt.  The Van Allen radiation belt is a zone of energetic charged particles, mostly from the solar wind and some from cosmic rays.  The particles are captured and held by the magnetosphere.  Earth has two such belts and sometimes others may be temporarily created.  The inner belt is from 400 to 7,500 miles above the Earth.  The outer belt extends 36,000 miles above the Earth.  The inner belt results from interactions of cosmic rays with Earth’s atmosphere.  The outer belt is made up of billions of high-energy particles from the Sun.  The inner edge of the outer belt has a very sharp transition which highly relativistic electrons cannot penetrate.  The reason for this shield-like behavior is not well understood.  [source: “What are the Van Allen Belts and why do they matter?,” science.nasa.gov]

Vela Supercluster.  The Vela Supercluster is a massive galactic supercluster.  It is 870 million light-years away and within the vicinity of the Zone of Avoidance, centered on the constellation Vela.  It is one of the largest structures found in the universe.  It is about 1,000 times the mass of the Milky Way.  It is one of 10 million superclusters of galaxies in the universe.  About 29 initial clusters have been identified in it.  It was discovered in 2016.  It had gone unnoticed due to the location behind the plane of the Milky Wa galaxy, where dust and stars obscure background galaxies.  [source: Byrd, “A new major supercluster of galaxies,” EarthSky, Nov 21, 2016]

Venus.  Venus spins on its axis clockwise, making it the only planet in the Solar System that spins in retrograde.  There are more volcanoes on Venus than any other planet.  Astronomers have discovered 85.000 volcanoes on Venus so far.  Scientists think that most of these volcanoes are dormant.  On In March 2023, scientists announced they found the first direct evidence of active volcanoes on Venus.  A day on Venus lasts 343 Earth days, while a year on Venus is shorter, at just 225 days.  This means that a year on Venus is shorter than a day.  Venus only rotates at 4 mph, compared that to Earth’s 1,040 mph.  The temperature on Venus can reach 870 degrees Fahrenheit due to an extreme greenhouse effect and the atmosphere being made up of mostly carbon dioxide.  The air pressure on Venus is 90 times higher that the pressure at sea level on Earth, That’s equivalent to about half a mile under the ocean.  Winds can reach 450 miles an hour on Venus.  The Venusian winds are faster than the strongest tornadoes on Earth.  The upper winds flow 50 times faster than the planet’s rotation.  [source: EarthSky editors, “Active volcanoes on Venus found in Magellan data,” EarthSky, March 15, 2023[

Vesta.  Vesta is the second largest object, after Ceres, in the asteroid belt.  It has a diameter of 326 miles.  It is the brightest asteroid visible from Earth.    Its south ploe has a hole in it.  Vesta has been long suspected to be the source of numerous meteorites that have hit the Earth.   Vesta has been more extensively sampled on Earth in terms of meteorites collected than any other extraterrestrial body.  Over 3,000 pounds of meteorites found on Earth came from Vesta.  [source: Krause, “How two ‘star-like points of light’ became geological worlds,” Oakridger.com, April 4, 2023]

Virgo Cluster.  The Virgo Cluster is a large cluster of galaxies in the constellation Virgo.  It has about 2,000 member galaxies.  Molecular gasses in the Virgo Cluster has been swept away by a huge cosmic broom that is preventing nearby galaxies from birthing new stars.  The actual cause of it has been a mystery.  Some of the galaxies in the Virgo Cluster are moving so rapidly that they are losing a significant amount of gas.  This orphaned gas can get compressed as it is blown back and moves behind its parent galaxy, and form stars as it does so.  These stars will fly away, becoming isolated stars in the Virgo Clster between the galaxies.  [source: Plait, “Blue Blobs Turn Out to be Orphan Star Clusters Mae of Gas Cast-Off From Galaxies,” syfy.com, July 22, 2022]

Void.  Cosmic voids (also known as dark space) are vast spaces between filaments which contain very little or no galaxies.  Voids can have a diameter of 300 million light-years.  The voids make up the vast majority of the volume of the universe, despite hosting almost none of the matter.  Dark energy could be casued by pressure from giant voids.    [source: Sutter, “Giant voids of nothingness may be flinging the universe apart,” Live Science, Aug 12, 2022]

Voyager.  The Voyager program sent two robotic probes into interstellar space.  In 1977, Voyager 1 and Voyager 2 were launched.  As of 2023, they are still in operation.  Voyager 1 is moving at 38,019 mph and is 14.8 billion miles away from Earth.  Voyager entered interstellar space in 2012.  Voyager 2 is moving at 34,384 mph and is 12.4 billion miles away from Earth.  Voyager 2 entered interstellar space in 2018.  For a few months each year, the distances between the Voyager spacecraft and Earth decrease.  That’s because Earth in its orbit moves toward the spacecraft faster than they’re moving away.  Earth’s motion around the sun is faster than the motion of the Voyager spacecraft.  Earth moves through space at a speed of 67,000 mph, faster than the Voyager spacecraft are moving.      [source: Whitt, “Why are the Voyager spacecraft getting close to Earth?,” EarthSky, March 23, 2023]

VT 1137-0337.  VT 1137-0337 is a new pulsar wind nebula between 14 and 80 years old.  It is the youngest pulsar ever discovered and lies in a dwarf galaxy (SDSS J113706, 18-033737.1) 395 million light-years away.  This may be the most powerful pulsar to date in a distant galaxy.  [source: Buongiorno,“This powerful pulsar is so young it might still be a teenage,” Astronomy, June 15, 2022]

WASP-39b.  WASP-39b (Bocaprins) is a hot Jupiter extrasolar planet 700 light-years away, notable for containing a substantial amount of water in its atmosphere.  It is located in the constellation Virgo.  The planet is only 4.3 million miles away from its star.  Its molecules in the atmosphere include sodium, potassium, water, carbon dioxide, carbon monoxide, and the mystery molecule, sulfur dioxide.  It is the first evidence of photochemistry on an exoplanet.  It orbits its host star (Malmok) every 4 days.  [source: Houser, “Astronomers detect ‘mystery molecule’ in exoplanet’s atmosphere,” freethink.com, Nov 29, 2022]

Whirlpool Galaxy.  The Whirlpool Galaxy (M31 or NGC 5194) is a spiral galaxy 31 million light-years away in the constellation Canes Venatici.  It has a diameter of 76,900 light-years.  It was the first galaxy to be classified as a spiral galaxy.  Its pair with NGC 5194 is among the most famous and relatively close interacting systems, and thus a favorite subject of galaxy interaction models.  The galaxy’s arms are long lanes of stars and gas studded with dust.  These arms are star-formation factories, compressing hydrogen gas and forming new star clusters.  [source: “Hubble captures massive star cluster in spiral Whirlpool Galaxy,” India Today, May 25, 2022]

White Dwarf.  A white dwarf is a stellar core remnant composed mostly of electron-degenerative matter.  White dwarfs are far denser than any substance on Earth.  A white dwarf is the size of the Earth, but with the mass of the Sun.  No fusion takes place in a white dwarf.  The maximum mass that a star can end its life with and still become a white dwarf is 1.4 solar masses.  This is called the Chandrasekhar limit.  More than 90% of the stars in the Milky Way galaxy will become white dwarfs.  The fastest spinning white dwarf completes a full rotation in 25 seconds.  The white dwarf is in the binary star system LAMOST J024048.51, which is 2.015 light-years away.  The star is Earth’s size but over 230,000 times more massive.   [source: Choi, “Spinning Propeller Star Slingshots Plasma at 7 Million MPH,” Inside Science, Nov 24, 2021]

WISE 0855-0714.  This is a sub-brown dwarf (not quite a planet and not quite a star) 7.4 light-years away.  It is the coldest (-55 degrees F) known object outside of our Solar system and is just barely visible at infrared wavelengths.  Its atmosphere is full of clouds of water vapor.  This was the first time water clouds have been detected outside our Solar System.  Its mass is 3 to 10 Jupiter masses.  [source: Atkinson, “First Detection of Water Clouds Outside Our Solar System,” universetoday.com, July 7, 2016]

Wolf-Rayet Star.  Wolf-Rayet (WR) stars are a rare set of stars with unusual spectra of ionized helium, nitrogen, and carbon.  The spectra indicate very high surface enhancements of heavy elements. They are among the most luminous, most massive, and most briefly detectable stars known.  Some evidence shows that WR stars could be responsible for the abundance of dust, partly through interactions with binary companions.  [source: Gough, “Prelude to a Supernova: The James Webb Captures a Rare Wolf-Rayet Star,” Universe Today, March 15, 2023]

YZ Ceti b.  YZ Ceti b is a rocky exoplanet that orbits a red dwarf star 12 light-years away.  The star and its four planets are in the constellation Cetus.  The star is classified as a flare star that undergoes intermittent fluctuations in luminosity. A magnetic field was detected from YZ Ceti b.  This is the first possible detection of a magnetic field on a planet beyond the solar system.  YZ Ceti b is not in the habitable zone.  It is too close to its star. The planet’s magnetic field pushed its plasma back toward the star, which then interacts with the star’s own magnetic filed, emitting bright flashed of energy.    [source: Lewis, “Strange radio signals detected from Earth-like planet could be a magnetic field necessary for life,” Live Science, Apr 3, 2023]

Zombie Star.  A zombie star is a hypothetical result of a supernova which leaves behind a remnant star, rather than completely dispersing the stellar mass. After astronomers looked at Supernova SN 2012Z in the NGC 1309 galaxy, they discovered that a star survived the explosion. Not only did it survive, but the new star was even brighter than it had been before. The white dwarf exploded as a supernova, with the former helium core left behind as a remnant zobie star.  [source: Seale and Tasoff, “The Star That Survived a Supernova,” UC Santa Barbara, June 23, 2022]

Zone of Avoidance.  The Zone of Avoidance (ZoA) is the are of the sky that is obscured by the Milky Way galaxy.  When viewing space from Earth, the interstellar dust and stars in the plane of the Milky Way (the galactic plan) obstruct the view of around 20% of the extragalactic sky at visible wavelengths.  Recently, astronomers have been able to determine the existence of a galaxy cluster behind the ZoA.  There could be as many as 58 galaxies in the structure.  [source: Carpineti, “Hidden Structure Discovered Behind the Milky Way’s ‘Zone of Avoidance’”, IFL Science, Nov 9, 2022]