Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets; the phenomena include supernova explosions, gamma ray bursts, and cosmic microwave background radiation. More generally, all phenomena that originate outside Earth’s atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole.
It is the study of everything outside the atmosphere of Earth.It studies celestial objects (such as stars, galaxies, planets, moons, asteroids, comets and nebulae) and processes (such as supernovae explosions, gamma ray bursts, and cosmic microwave background radiation). This includes the physics, chemistry of those objects and processes.
Saturn continues to be a standout object in the early evening sky.
The ringed planet stands about 20° above the southwestern horizon an hour after sunset and remains on view until nearly 10 p.m. local daylight time.
The ringed planet shines at magnitude 0.5, more than a full magnitude brighter than any of the background stars in its host constellation, Sagittarius.
If you own a telescope, there’s no better target than Saturn. Even the smallest instrument shows Saturn’s 16″-diameter disk surrounded by a dramatic ring system that spans 36″ and tilts 26° to our line of sight.
Mission to Mercury Launches
The BepiColombo spacecraft launched October 19th, at 9:45:28 p.m. EDT, atop an Ariane 5 rocket from an equatorial launch site in Kourou, French Guiana, beginning a seven-year journey to Mercury. The voyage began perfectly, atop towering pillars of flame that lit up the early morning sky and remained visible until the side boosters burned out 2 minutes later, leaving the steady light of the main rocket stage visible as a greenish point in the sky.
BepiColombo’s journey will return it to Earth, past Venus twice, and take it by Mercury six times before finally settling in to orbit on December 5th, 2025. The mission is a combined effort of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency(JAXA).
Getting to Mercury is difficult — so difficult that fewer spacecraft have visited Mercury than have visited Saturn. NASA has sent two spacecraft: Mariner 10, which completed three flybys (all over the same hemisphere) in 1974 and 1975, and Messenger, which accomplished its orbital mission from 2011 to 2015.
The ghost of Cassiopeia
About 550 light-years away in the constellation of Cassiopeia lies IC 63, a stunning and slightly eerie nebula. Also known as the ghost of Cassiopeia, IC 63 is being shaped by radiation from a nearby unpredictably variable star, Gamma Cassiopeiae, which is slowly eroding away the ghostly cloud of dust and gas. This celestial ghost makes the perfect backdrop for the upcoming feast of All Hallow’s Eve — better known as Halloween.
IC 63 — nicknamed the Ghost Nebula — is about 550 light-years from Earth. The nebula is classified as both a reflection nebula — as it is reflecting the light of a nearby star — and as an emission nebula — as it releases hydrogen-alpha radiation. Both effects are caused by the gigantic star Gamma Cassiopeiae. The radiation of this star is also slowly causing the nebula to dissipate.
Gravitational waves could soon accurately measure universe’s expansion
Scientists estimate that given how quickly LIGO researchers saw the first neutron star collision, they could have a very accurate measurement of the rate of the expansion of the universe within five to 10 years.
Twenty years ago, scientists were shocked to realize that our universe is not only expanding, but that it’s expanding faster over time.
Pinning down the exact rate of expansion, called the Hubble constant after famed astronomer and UChicago alumnus Edwin Hubble, has been surprisingly difficult. Since then scientists have used two methods to calculate the value, and they spit out distressingly different results. But last year’s surprising capture of gravitational waves radiating from a neutron star collision offered a third way to calculate the Hubble constant.
That was only a single data point from one collision, but in a new paper published Oct. 17 in Nature, three University of Chicago scientists estimate that given how quickly researchers saw the first neutron star collision, they could have a very accurate measurement of the Hubble constant within five to ten years.
Galaxy clusters are rare regions of the universe consisting of hundreds of galaxies containing trillions of stars, as well as hot gas and dark matter.
It has long been known that when a galaxy falls into a cluster, star formation is fairly rapidly shut off in a process known as “quenching.” What actually causes the stars to quench, however, is a mystery, despite several plausible explanations having been proposed by astronomers.
A new international study led by astronomer Ryan Foltz, a former graduate student at the University of California, Riverside, has made the best measurement yet of the quenching timescale, measuring how it varies across 70 percent of the history of the universe. The study has also revealed the process likely responsible for shutting down star formation in clusters.
Each galaxy entering a cluster is known to bring some cold gas with it that has not yet formed stars. One possible explanation suggests that before the cold gas can turn into stars, it is “stripped” away from the galaxy by the hot, dense gas already in the cluster, causing star formation to cease.
Another possibility is that galaxies are instead “strangled,” meaning they stop forming stars because their reservoirs cease getting replenished with additional cold gas once they fall inside the cluster. This is predicted to be a slower process than stripping.
A third possibility is that energy from the star formation itself drives much of the cold gas fuel away from the galaxy and prevents it from forming new stars. This “outflow” scenario is predicted to occur on a faster timescale than stripping, because the gas is lost forever to the galaxy and is unavailable to form new stars.
Because these three different physical processes predict galaxies to quench on different relative timescales over the history of the universe, astronomers have postulated that if they could compare the number of quenched galaxies observed over a long time-baseline, the dominant process causing stars to quench would more readily become apparent.